Paradox of estuarine quality: benthic indicators and indices, consensus or debate for the future

Measuring ecological quality status in low-diversity Arctic intertidal foraminiferal assemblages using a diversity-based index

EcoQS assessment of the marine intertidal zone based on its fauna is challenging because the assemblages have a low diversity and consist of stress tolerant species. The new approach we propose is to pool foraminiferal diversity (effective number of species exp(H'bc)) across the whole intertidal zone including the salt marsh and tidal flat. In seven fjordheads studied in northern Fennoscandia, polycyclic aromatic hydrocarbon (PAH) concentrations indicated low levels of pollution (EcoQSPAH Excellent to Moderate). Jadammina or Balticammina dominated the salt marsh, Elphidium albiumbilicatum, Elphidium williamsoni, Elphidium clavatum, and Buccella frigida occurred in the tidal flat. Ovammina opaca thrived in both belts. While foraminiferal test abnormalities are often proposed to measure pollution impacts, we did not detect any correlation with PAHs. EcoQS based on foraminiferal diversity (EcoQSforam Excellent to Good) matched EcoQS based on PAHs suggesting that pooled foraminiferal diversity reliably measures intertidal EcoQS.

Testing the applicability of the Modelling-Ongrowing Fish farms-Monitoring B (MOM-B) investigation system for assessing benthic habitat quality in the manila clam Ruditapes philippinarum aquaculture areas

The coastal aquaculture areas have been subject to a variety of anthropogenic pressures in recent studies, and reasonable environmental quality assessment is essential for both ecological conservation and production practices. However, there are significant differences between the results produced from various environmental quality assessment regarding the focus of the evaluation and the fundamental methodology. Furthermore, many of these methods are very specific and difficult to adapt to general applications. Here, we utilized the Modelling-Ongrowing fish farms-Monitoring B investigation system (MOM-B), we assessed the benthic habitat quality of benthic bivalve aquaculture areas in the Xiaoqing River estuary located in Laizhou Bay, China. The aim was to validate the accuracy and practicality of this system. The biological, chemical, and sensory parameters of the MOM-B system, temperature, chlorophyll a (Chl-a), food availability, and planktonic larvae were evaluated throughout the investigation area during the summer of 2021. The MOM-B results indicated that the benthic habitat quality in the survey area was good and lightly disturbed, but the quality in the middle tide area began to deteriorate in August, the hottest month of the summer. Environmental factors indicated that the combined effects of high temperatures and fine sedimentation had led to increased environmental stress in the middle tide area. Food availability and population recruitment also suggested that the benthic habitat quality was better in the high tide and low tide areas than in the middle tide area, and more favorable for the survival of Manila clams. The accuracy, sensitivity, and discriminatory ability of the MOM-B system were demonstrated by environmental and biological indicators. This work showed that the MOM-B system is a practical, simple, and sensitive environmental assessment tool that is easy to implement in estuarine and benthic bivalve aquaculture areas. It can be used for long-term continuous monitoring and as an early warning tool for benthic habitat quality.

Spatio-temporal variability in macroinvertebrate community structure and ecological health status of a tropical dynamic river-estuarine system, India: An integrated approach of multivariate analysis

River-estuarine ecosystems are under severe anthropogenic threat due to resource exploitation, transportation, sewage/industrial discharges, and pollutants from surrounding areas. Monitoring the water quality and biological communities is essential for assessing ecosystem health and sustainability. Present study integrated the ecological community data along with water quality analysis to understand the impact of anthropogenic pressures on benthic macroinvertebrates. Samples were collected from 10 locations (comprising of both rural and urban areas) for Benthic macroinvertebrates, physico-chemical and microbiological parameters along the lower stretch of the Bhagirathi-Hooghly river-estuarine (BHE) system during the post-monsoon seasons of 2020, 2021, and 2022. During the entire study period, a total of 5730 individuals from 54 families in 19 orders of 3 phylum of macroinvertebrate were recorded. Among them Thiaridae (27.1%) and Chironomidae (22.8%) were found to be the most abundant families. Based on the water quality data Cluster analysis and nMDS indicated two distinct groups of locations: Group-I with rural settings and Group-II with urban settings. Alpha diversity metrics showed higher diversity (2.817) and evenness (0.744) in rural locations (Group-I) compared to urban locations (Group-II). The overall saprobic score of the macroinvebrate data revealed Group-I (5.09) to be in good condition, while Group-II (4.95) showed moderately polluted conditions. Redundancy analysis (RDA) highlighted the correlation of pollution-tolerant species (Chironomidae, Culicidae) with high organic loads i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD) in Group-II. In contrast, Group-I locations exhibited positive correlations with Dissolved Oxygen (DO) and supported less pollution-tolerant organisms (Coenagrionidae, Dytiscidae). The study emphasizes the importance of integrated analysis of ecological community data and water quality parameters to assess the health status of river-estuarine ecosystems.

Long-term sediment records reveal over three thousand years of heavy metal inputs in the Mar Menor coastal lagoon (SE Spain)

The Mar Menor lagoon combined high biological production and environmental quality, making it an important economic engine. However, the pressure of human activities put its ecological integrity at risk, the oldest environmental impact being mining activity recorded since Roman times, about 3500 years ago, reaching its maximum intensity in the 20th century, contributing heavy metals to the lagoon sediments for almost 30 centuries. This work reviews the spatiotemporal evolution of the main heavy metals in this coastal lagoon using data from 272 surface sediment samples obtained during the last 40 years and two deep cores covering the total history of the lagoon (c. 6500 yrs BP), so as their incidence in the lagoon trophic web. The observed patterns in sedimentation, sediment characteristics and heavy metal content respond to the complex interaction, sometimes synergistic and sometimes opposing, between climatic conditions, biological production and human activities, with mining being mainly responsible for Pb, Zn and Cd inputs and port activities for Cu. High Fe/Al, Ti/Al and Zr/Al ratios identify periods of mining activity, while periods of arid climatic conditions and deforestation that increase erosion processes in the drainage basin and silt concentration in the lagoon sediments are determined by high Zr/Rb and, to a lesser extent, Zr/Al and Si/Al ratios. After the cessation of direct discharges into the lagoon in the 1950s, the recent evolution of heavy metals concentration and its spatial redistribution would be determined by hydrographic and biogeochemical processes, solubility of different elements, and coastal works in harbours and on beaches. The bioconcentration factor decreases along the trophic levels of the food web, suggesting that the lagoon ecosystem provides an important service by retaining heavy metals in the sediment, largely preventing their bioavailability, but actions involving resuspension or changes in sediment conditions would pose a risk to organisms.

Assessing the ecological quality status of macrobenthic communities in a marine terminal of liquefied natural gas in Peru

Macrobenthic organisms are useful bioindicators to assess ecological quality status. On the south-central coast of Peru (13°15.15'S, 76°18.5'W), a Liquefied Natural Gas (LNG) marine terminal has been operating since 2010. We investigated the macrobenthic communities and sediment parameters from 2011 to 2020 to evaluate the ecological quality status in the surrounding area of the marine terminal, using the AZTI Marine Biotic Index (AMBI) and its multivariate version (M-AMBI). We analyzed the diversity and community composition of macrobenthic invertebrates and the physico-chemical parameters of the sediment from 29 sampling sites, ranging from 0 to 15m depth. The sampling design considered: the direct influence zone ("DIZ", surroundings of the marine terminal), and northern (NCZ) and southern (SCZ) control zones. Our results indicated that abundance was high at SCZ and decreased with depth. Species richness and diversity were high at DIZ and NCZ, respectively, and increased up to 10m but dropped at 15m. High sand content was recorded in shallow depths, while in deeper areas and DIZ, mud and organic matter increased and redox potential was negative. AMBI indicated a "slightly disturbed" status in general, while M-AMBI indicated "good" or "moderate" status at depths ≤ 12m, and "poor" status at 15m. Overall, the season/year factor was not important, and variables were mostly significantly different across depths. Redox potential and organic matter were correlated with M-AMBI at 15m. In general, our results indicate an acceptable ecological quality surrounding the marine terminal, likely because the study area is not influenced by an important input of an anthropogenic stressor. This study highlights the importance of monitoring benthic communities in the surroundings of human-made structures and the use of ecological quality indices for understanding potential impacts.

Inferring the ecological quality status based on living benthic foraminiferal indices in transitional areas of the Guanabara bay (SE Brazil)

Using benthic foraminifera, we evaluate the ecological quality status (EcoQS) of transitional waters of the Guanabara Bay (SE Brazil) by applying the diversity-based index exp (H'_bc) and the sensitivity-based Foram-AMBI for the first time in South America. The Guanabara Bay was selected for this study as it is one of the largest transitional ecosystems in the State of Rio de Janeiro and has been severely impacted by anthropogenic activities. Concentrations of potentially toxic elements (PTEs) were assessed by sequential chemical extraction in three phases (i.e., dissolved in water, adsorbed on organic matter, and Mn oxy-hydroxides). Total organic carbon, total nitrogen, and stable isotope (δ¹³C and δ¹⁵N) signatures of organic matter were analyzed to trace environmental stress. The Ammonia/Elphidium ratio suggests hypoxic conditions at most of the sampled sites. Principal component analysis identifies the first component as environmental stress underlying organic matter and PTE enrichment (in all three phases), which is positively related to Foram-AMBI and negatively to exp (H'_bc). The exp (H'_bc) and Foram-AMBI indices reveal that stations near the Governador Island and Niterói margin have the worst EcoQS, showing medium to extreme pollution. Additionally, Foram-AMBI and exp (H'_bc) provide a congruent EcoQS classification for ∼64% of the sites. Although these results are promising, they suggest that a significant effort should be made to obtain better knowledge of foraminiferal ecological requirements to employ benthic foraminifera as a biomonitoring and management method.

Benthic community resilience in two differently impacted tropical estuaries: Taxonomic vs functional approaches

Estuaries experience incessant modifications due to various stressors causing shifts in the benthic species community structure and ecosystem functioning. Two tropical estuaries along Northwest India, exposed to varied intensities of anthropogenic perturbations, were sampled seasonally for two consecutive years. Specific aims were to assess, compare and link the macroinvertebrate taxonomic and functional structures, to evaluate the resilience of estuarine benthic ecosystems by employing the multiple-trait approach and to identify major influencing environmental drivers for patterns discerned. Taxonomic and functional compositions in both the estuaries produced varied segregations along the estuarine zones, driven primarily by natural estuarine gradients like salinity and sediment grain size, despite extant anthropogenic stressors. Multiple traits contributed to the variance in benthic functioning. The Biological Trait Analysis (BTA) revealed that both the estuaries had similar trait compositions in the lower zones, while the middle and upper zones of each estuary presented different permutations of traits. The functional complexity at different estuarine sections was influenced by the variability in taxonomic composition and species dominance. However, relationships between Functional Diversity (FD) and species diversity were equivocal, signifying that taxonomic diversity may not be an efficient proxy for benthic functioning. As the zones had differential stressors and disturbance acts as a filter, discrete functional trait profiles of opportunistic traits were visualized along the potentially impacted zones. Thus, the less impacted lower zones had multiple traits, while the mid-upper zones that were subject to both anthropogenic and natural stressors had fewer traits. A more consistent functional structure, higher functional redundancy and substantial proportion of recolonisation traits (small-sized, short-lived, motile forms) suggested better resilience in one study estuary than the other one. Our study advocates that the inclusion of both taxonomical and functional metrics can provide in-depth inferences related to the macrobenthic community resilience and this coupled approach is imperative for effective future management programs.

Benthic impact assessment of a dredge sediment disposal in a dynamic resilient environment

The eastern part of the Bay of Seine (English Channel) is highly impacted by harbour activities and the dumping of dredged sediment by the port authorities of Le Havre (GPMH) and Rouen (GPMR). Sediment dredged by the GPMH (2-2.5 millions of m³ per year) has been disposed at the subtidal Octeville site since 1947. Since the 2000s, mainly fine sediment (80% of fine particles <63 μm) has been disposed using alternate mosaic boxes with limited thickness (0.2 to 0.6 m per box per year), preventing the accumulation of disposed sediment in some parts of the dumping site. During the period August 2016 to September 2017, an experimental study was set up to identify the spatio-temporal changes of the macrobenthos collected at ten stations on six dates: three stations where different volumes of sediments were dumped (from 41,000 to 186,000 m³), two stations located within the Octeville site but without dumping operations during the study and five stations outside the disposal site (northern and southern zones). The Taxonomic Richness, total abundance and abundances of the polychaete Owenia fusiformis show negative correlations with the volumes of deposited sediment, whereas use of the AMBI (AZTI's Marine Biotic Index) and B2OA (Benthic Opportunist Annelids Amphipods) indices does not allow us to distinguish the impacted zone. Our study shows that the impact of dumping remains local and the benthic habitats display a high degree of resilience with rapid recovery of the community after the cessation of disturbance. Recommendations on the future long-term strategy are proposed to improve assessment and minimise the impact of dumping sediment on this benthic habitat.

Influence of water quality on the macroinvertebrate community in a tropical estuary (Buenaventura Bay)

The anthropogenic discharges of inorganic nutrients impact water quality, affecting the macroinvertebrate assemblage and food safety. The main objective of this study was to examine the seawater quality and macroinvertebrate dynamics in muddy habitats of Buenaventura Bay, Colombian Pacific. Macroinvertebrates were captured using artisanal trawl nets during different seasons and along four sampling sites. Multivariate analyses (canonical correspondence analysis and generalized additive model) were used to assess the effects of variations in nitrite, nitrates, phosphate concentrations, and physicochemical variables (salinity, pH, dissolved oxygen [DO], temperature, and total dissolved solids [TDS]) of water on the macroinvertebrate assemblage. Richness was the highest at sites with high salinity and temperature and low concentrations of nitrites and TDS. The densities of the commercial shrimp species Xiphopenaeus riveti and Rimapenaeus byrdi were the highest at sites with higher DO and alkalinity, and lower nitrate concentrations. The swimming crab Callinectes arcuatus was dominant at sites with low water quality. In summary, in the transitional season and at the inner sites of Buenaventura Bay, it was observed the lowest water quality due to high nitrate concentration. High nitrate concentration was highlighted as the main anthropogenic factor that could decrease the capture of target macroinvertebrate species for food and livelihoods of artisanal fishermen and their families. Thus, macroinvertebrate communities may be vulnerable to increased inorganic nutrient inputs, which could affect estuarine water quality and ecosystems services. Integr Environ Assess Manag 2022;18:796-812. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Changes in Macrozoobenthos Community after Aquatic Plant Restoration in the Northern Venice Lagoon (IT)

Responses of the macrozoobenthic community to an ecological restoration activity in the northern Venice lagoon were studied, within the scope of the project LIFE SEagrass RESTOration aimed at recreating aquatic phanerogam meadows largely reduced in recent decades. Transplants were successful in almost all project areas. Macrozoobenthos was sampled in eight stations before (2014) and after (2015, 2016, 2017) transplanting activities. An increase in abundance and fluctuations in richness and univariate ecological indices (Shannon’s, Margalef’s, Pielou’s indices) resulted during the years. Comparing non-vegetated and vegetated samples in 2017, every index except Pielou’s increased in the latter. Multivariate analysis (hierarchical cluster analysis, MDS, PERMDISP, SIMPER) grouped samples by localization rather than years, with differences between stations due to the abundance of common species. In 2017, results were also grouped by the presence or absence of aquatic plants, with differences in the abundance of grazer and filter-feeding species. Results of ecological index M-AMBI depicted conditions from moderate to good ecological status (sensu Dir.2000/60/EC) with similar fluctuations, as presented by univariate indices from 2014 to 2017. Responses of the macrozoobenthic community were more evident when comparing vegetated and non-vegetated samples, with the vegetated areas sustaining communities with greater abundance and diversity than non-vegetated samples, thus demonstrating the supporting function of aquatic plants to benthic communities.

Ecological quality status assessment of tropical estuaries with benthic indices using differently derived reference conditions

Setting appropriate reference conditions (RCs) is critical for classifying the Ecological Quality Status (EcoQS) which is extremely challenging, considering the present-day estuaries. The EcoQS of three tropical estuaries was assessed by applying five different RCs to identify the best applicable method for the area. The AZTI's indices (AMBI and M-AMBI) categorised areas with sharper pollution gradient with ease, while classification of moderate-low polluted areas was ambiguous. Indices responded to chemical stressors more clearly in the impacted estuary compared to the less polluted estuaries. Ecological status assigned by the default RC (lowest AMBI and highest diversity and richness values) were more accurate than those obtained on application of other four types of RCs, owing to various estuarine constraints that are discussed herewith. Thus, prior to application, caution should be exercised while setting area-specific RCs. The inclusion of combination of AZTI's indices with professional judgment for successful appraisal of ecosystem is recommended.

The Marine Influence Index (MII): A Tool to Assess Estuarine Intertidal Mudflat Environments for the Purpose of Foraminiferal Biomonitoring

In this paper, we propose a marine influence index (MII), which is thought to give an integrated quantitative description of the complex of the environmental parameters controlling the foraminiferal fauna in estuarine intertidal mudflats. The MII contains three components, as follows: (1) the relative distance along the salinity gradient, (2) the emergence time relative to a reference tidal cycle, and (3) the relative importance of river outflow in the 30 days before sampling the foraminiferal fauna. Although these three parameters all have a strong relation with salinity, they also implicitly include other environmental parameters, such as the introduction of marine and continental organic matter and biota, hydrodynamic energy, or temperature. In order to show the functioning of this new index, MII is calculated for 28 stations in the Auray and Vie estuaries, for two different periods. The next step will be to compare the MII with faunal data sets. Ideally, this comparison should allow us to find strong correlations between some characteristics of the foraminiferal assemblages and the MII. If such strong correlations were indeed found, any major deviation of this relationship could then be interpreted as being due to strong anthropogenic disturbance.

Foraminiferal Distribution in Two Estuarine Intertidal Mudflats of the French Atlantic Coast: Testing the Marine Influence Index

This study focuses on the foraminiferal distribution on intertidal mudflats of two contrasted estuaries (Auray and Vie) along the French Atlantic coast. In both estuaries, the foraminiferal communities are dominated by Haynesina germanica and the Ammonia tepida group. Stations located near the outlets show a high diversity and abundance of species of the genus Elphidium. Stations in the inner estuary show a higher proportion of agglutinated species (Ammotium salsum, Ammobaculites agglutinans). Multivariate statistical analysis suggests that the distance to the sea and the percentage of fine sediment (<63 µm) are the two main parameters explaining the foraminiferal distribution. Chemical analyses of the sediment show that the two studied estuaries are not affected by major anthropogenic pollution, so that the faunas should mainly reflect the natural controlling parameters. Three indices of environmental quality commonly used in coastal areas show counter-intuitive differences between stations, suggesting that these indices may be less reliable for use in intertidal estuarine mudflats. The newly developed Marine Influence Index (MII) integrates three major ecological factors: the position of the sampling point on the salinity gradient, the emergence time at low tide and the relative importance of fresh water discharge. In our dataset, MII shows significant correlations with the controlling environmental parameters (distance to the sea, percentage grains <63 µm), as well as with the foraminiferal patterns (PCA axis 1, species richness, percentage of Elphidium spp. and Quinqueloculina spp.). These results suggest that the MII explains a substantial part of the faunal variability on estuarine intertidal mudflats, and can be used to detect deviations from the natural distribution patterns in response to anthropogenic pollution.

Parasites as conservation tools

Parasite success typically depends on a close relationship with one or more hosts; therefore, attributes of parasitic infection have the potential to provide indirect details of host natural history and are biologically relevant to animal conservation. Characterization of parasite infections has been useful in delineating host populations and has served as a proxy for assessment of environmental quality. In other cases, the utility of parasites is just being explored, for example, as indicators of host connectivity. Innovative studies of parasite biology can provide information to manage major conservation threats by using parasite assemblage, prevalence, or genetic data to provide insights into the host. Overexploitation, habitat loss and fragmentation, invasive species, and climate change are major threats to animal conservation, and all of these can be informed by parasites.

Effect of multiple stressors on the functional traits of sub-tidal macrobenthic fauna: A case study of the southeast coast of India

The use of functional information of taxa is a promising approach to uncover the underlying mechanism of ecosystem functioning. We used biological trait analysis (BTA) to assess the functional response of subtidal macrobenthos with multiple stressors. Seventeen environmental variables from 42 stations of five coastal districts were assessed along the southeast coast of India. Dominant fauna was assigned into 20 categories belonging to six functional traits. Additionally, we used five ecological groups (EG) of AMBI as a covariable trait to validate functional traits and EG relationship. The trait composition in the communities showed significant variation between undisturbed and disturbed areas. RLQ/Fourth corner combined approach illustrated the effects of stressors and isolated the corresponding species associated with different stressors. Smaller, short-lived, deposit-feeding, and discretely motile fauna occurred at the disturbed areas, whereas, larger, long-lived, and highly motile at the undisturbed area. Dissolved oxygen, organic enrichment, and metals concentration were the main environmental descriptors influencing the trait composition. The results highlight the importance of the BTA approach to uncover the response of the macrobenthic community to anthropogenic disturbances-driven impacts in multi-stressed near-shore coastal ecosystems.

COVID-19 Pandemic Lockdown: An Excellent Opportunity to Study the Effects of Trawling Disturbance on Macrobenthic Fauna in the Shallow Waters of the Gulf of Gabès (Tunisia, Central Mediterranean Sea)

This study describes for the first time in the central Mediterranean Sea the effects of bottom trawling on macrobenthic fauna in tidal channels of the Kneiss Islands in the Gulf of Gabès, Tunisia. Following a BACI protocol, two control stations (protected by artificial reefs) and two trawled stations (impacted stations) were sampled during a period with the absence of bottom trawling activity (the COVID-19 pandemic lockdown period from March to May 2020) and during a trawled period. Although bottom trawling had no impact on sediment composition, this anthropogenic activity reduced the concentration of dissolved oxygen and had a noticeable effect on water column turbidity. The absence of trawling led to a significant increase in biomass, number of species, and abundance of total macrofauna. This illustrated the negative effect of trawling activity in shallow waters and the high resilience of macrobenthic communities of the tidal ecosystem of the Kneiss Islands. In the future, it would be very important to control the use of this destructive fishing gear due to its negative impact on the marine habitat and macrofauna, which represents essential prey for fishes and birds living in this protected area.

Macrofauna community patterns in a Chiloe Island channel used intensely for aquaculture: the ecological status of its benthic environment

Background

It is known that aquaculture may produce negative environmental effects on marine ecosystems. Southern Chile is one of the most important salmon and mussel-producing areas in the world. Here we assess the ecological status of benthic communities near farming centers in Caucahue Channel, Chiloe, which has been used intensely for salmon and mussel production for 30 years.

Methods

The macrofauna, sediments and water column were characterized at distances of 5 to 100 m from three salmon and three mussel-producing centers. Information was also obtained from reference sites 500 to 3000 m from these aquaculture farms. The macrofauna and environmental conditions during winter were analyzed using uni- and multivariate analysis and the AZTI Marine Biotic Index (AMBI) as an indicator of benthic community condition.

Results

(i) There is a high degree of spatial dissimilarity in macrofauna and environmental variables among sampling sites and types of environments (far from or near farming centers) and between the northern and southern areas of the channel; (ii) sediment structure (mean grain size and percentage of total organic matter) correlated with the observed dissimilarities in macrofauna communities; and (iii) the level of perturbation according to AMBI was heterogeneous, with sites in the undisturbed/normal range to moderately disturbed/polluted.

Conclusions

We found a high spatial dissimilarity in benthic macrofauna and environmental variables among sampling sites, environmental types and between the northern and southern areas of the channel. AMBI and multivariate community-environment analysis are useful tools to define the level of perturbation of a geographic area at different spatial scales, using all the ecological information from each sample and replicates.

Salinity as a Key Factor on the Benthic Fauna Diversity in the Coastal Lakes

Benthic communities were studied in nine Polish coastal lakes of the Baltic Sea; representing three levels of hydrological connection with the sea (isolated, periodically connected, and permanently connected), with resultant differences in salinity (freshwater, transitional, and brackish). The lakes classified in this way allowed us to investigate biodiversity in relation to the degree of environmental pressure. Stress intensity in coastal water bodies, resulting from contrasting marine and terrestrial influences, varied from mild to severe. Spatial variation in environmental predictors affected species richness more strongly than seasonal fluctuations. The broader the spatial salinity gradient, the smaller the species number recorded. Differences in the intensity of natural instability only slightly affected species number and α-diversity. In Baltic coastal lakes, characterized by low salinity (max. 7.5 PSU), benthic faunal communities were dominated by large populations of opportunistic species. This applied primarily to closed systems and those periodically influenced by seawater intrusion. The marine component of fauna played a more important role in increasing the diversity of benthos in permanently open water bodies (brackish). The highest density of benthic fauna was recorded in them, whereas low values were associated with the strongest instability, observed in lakes periodically linked with the sea (transitional).

Benthic Foraminiferal Indices and Environmental Quality Assessment of Transitional Waters: A Review of Current Challenges and Future Research Perspectives

Transitional waters straddle the interface between marine and terrestrial biomes and, among others, include fjords, bays, lagoons, and estuaries. These coastal systems are essential for transport and manufacturing industries and suffer extensive anthropogenic exploitation of their ecosystem services for aquaculture and recreational activities. These activities can have negative effects on the local biota, necessitating investigation and regulation. As a result of this, EcoQS (ecological quality status) assessment has garnered great attention as an essential aspect of governmental bodies’ legislative decision-making process. Assessing EcoQS in transitional water ecosystems is problematic because these systems experience high natural variability and organic enrichment and often lack information about their pre-human impact, baseline, or “pristine” reference conditions, knowledge of which is essential to many commonly used assessment methods. Here, foraminifera can be used as environmental sentinels, providing ecological data such as diversity and sensitivity, which can be used as the basis for EcoQS assessment indices. Fossil shells of foraminifera can also provide a temporal aspect to ecosystem assessment, making it possible to obtain reference conditions from the study site itself. These foraminifera-based indices have been shown to correlate not only with various environmental stressors but also with the most common macrofaunal-based indices currently employed by bodies such as the Water Framework Directive (WFD). In this review, we firstly discuss the development of various foraminifera-based indices and address the challenge of how best to implement these synergistically to understand and regulate human environmental impact, particularly in transitional waters, which have historically suffered disproportionate levels of human impact or are difficult to assess with standard EcoQS methods. Further, we present some case studies to exemplify key issues and discuss potential solutions for those. Such key issues include, for example, the disparate performance of multiple indices applied to the same site and a proper assignment of EcoQS class boundaries (threshold values) for each index. Disparate aptitudes of indices to specific geomorphologic and hydrological regimes can be leveraged via the development of a site characteristics catalogue, which would enable the identification of the most appropriate index to apply, and the integration of multiple indices resulting in more representative EcoQS assessment in heterogenous transitional environments. In addition, the difficulty in assigning threshold values to systems without analogous unimpacted reference sites (a common issue among many transitional waters) can be overcome by recording EcoQS as an ecological quality ratio (EQR). Lastly, we evaluate the current status and future potential of an emerging field, genetic biomonitoring, focusing on how these new techniques can be used to increase the accuracy of EcoQS assessment in transitional systems by supplementing more established morphology-based methods.

Seasonality of macrobenthic assemblages and the biotic environmental quality of the largest monsoonal estuary along the west coast of India

This study deals with the macrobenthic assemblages and the biotic environmental quality of Kochi backwaters (KBW), India. Due to the heavy river discharge, extensive limnetic and turbid conditions prevailed in the KBW during the southwest monsoon (June to September). This exerted a profound adverse effect on the abundance, richness, and diversity of macrobenthic assemblages. Overall, mesohaline conditions with a clayey sand bottom substratum favored the high macrofaunal abundance during the southwest and northeast monsoon seasons. But mesohaline condition and sandy silt bottom were found to support high macrofaunal abundance in the KBW during the pre-monsoon season. Polychaete dominated the macrobenthic community, regardless of seasons. Capitella capitata, Heteromastus similis, Paraheteromastus sp., Prionospio cirrobranchiata, Minuspio cirrifera, Pagurapseudopsis kochindica, P. gymnophobia, Ctenapseudes indiana, C.chilkensis, Tanais sp., Villorita cyprinoides, Grandidierella sp., Ampelisca sp., and Littorina sp. were the dominant ones observed during the study. The sediment organic carbon, in general, showed a positive correlation with polychaete abundance during all three seasons. The ecological status of KBW during all three seasons was assessed as per BO2A index, which ranged from 0.05 to 0.18, suggesting a healthy to a moderately polluted bottom environmental condition.

Indicative value of benthic foraminifera for biomonitoring: Assignment to ecological groups of sensitivity to total organic carbon of species from European intertidal areas and transitional waters

This work contributes to the ongoing work aiming at confirming benthic foraminifera as a biological quality element. In this study, benthic foraminifera from intertidal and transitional waters from the English Channel/European Atlantic coast and the Mediterranean Sea were assigned to five ecological groups using the weighted-averaging optimum with respect to TOC of each species. It was however not possible to assign typical salt marsh species due to the presence of labile and refractory organic matter that hampers TOC characterization. Tests of this study species' lists with Foram-AMBI on two independent datasets showed a significant correlation between Foram-AMBI and TOC, confirming the strong relation between foraminifera and TOC. For one of the validation datasets, associated macrofaunal data were available and a significant correlation was found between the foraminiferal Foram-AMBI and the macrofaunal AMBI. The here proposed lists should be further tested with sensitivity-based indices in different European regional settings.

Linking fish and crustacean taxonomic composition with seasonal contrasts in the soft-bottom intertidal zone

The primary objective of this study was to investigate the seasonal fish and crustacean variations concerning taxonomic composition, species richness, and diversity in sandy beach habitat. For this purpose, we investigated the Sonmiani Hor lagoon area during four distinct seasons, i.e., northeast (NE) monsoon, pre-monsoon, south-west (SW) monsoon, and post-monsoon for one year. During each haul, the net was pulled about 100m along the beach in 0.5m depth. The results showed a strong linear correlation between the diversity index and equitability in fishes (r = 0.978). The diversity index was strong negatively correlated with the abundance and biomass (r = -0.978, -0.972, respectively). The physical attributes like sea surface water temperature and salinity showed a strong negative effect on species assemblages (r = -0.981 and -0.943, respectively). The mean air and water temperature illustrated approximately 3°C difference during NE and pre-monsoon seasons. However, salinity, pH, and electrical conductivity did not show any significant seasonal variabilities. Under the ecological indices, the fish species displayed higher diversity (H' = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H' = 1.58). The equitability and species richness, however, remained more noticeable during SW monsoon (J' = 0.81). The total number of individuals of fish and crustaceans reached 4799 with 3813 fish individuals and 986 individuals of crustaceans. A total of 27 families of fish while five crustacean families comprising of 30 genera and 38 fish species while ten genera and 17 species of crustaceans were recorded. Liza subviridis displayed the highest abundance among the sampled fish species. In conclusion, fish species constituted a significant part of the coastal fauna in the study area. The seasonal variations displayed distinct variations in fish species composition and diversity.

Conservation Paleobiology as a Tool to Define Reference Conditions in Naturally Stressed Transitional Settings: Micropaleontological Insights from the Holocene of the Po Coastal Plain (Italy)

The key role of paralic environments as providers of ecosystem services, associated with their increasingly threatened state, led to the definition of international water management policies aimed to improve ecological quality status (EcoQs). Restoration actions rely on the definition of reference conditions, which is a particularly challenging task in naturally stressed transitional environments. In the present work, we apply the diversity index Exp(H’bc) on benthic foraminifer assemblages from two anthropogenically unimpacted transitional to coastal Holocene sediment successions of the Po coastal plain, in order to assess past EcoQs (PaleoEcoQs). Ostracod ecological groups provided detailed insights on naturally stressful paleoenvironmental conditions. We show that “poor” to “moderate” PaleoEcoQs are recorded by biological indicators at reference conditions under fluctuations of chemical-physical parameters and organic matter enrichment. We emphasize the importance of a site-specific paleobiological approach, as significant differences in diversity occur even on a short spatial scale. This study illustrates that early to mid-Holocene sediment successions resulted to be appropriate for conservation paleobiological purposes, providing a high-resolution paleoecological record under the influence of the Holocene sea-level rise in analogy with the present-day global change.

Reconstruction of the palaeo-ecological quality status in an impacted estuary using benthic foraminifera: The Santos Estuary (São Paulo state, SE Brazil)

The Santos Estuary (SE Brazil) is a coastal ecosystem with a high ecological importance and has been strongly impacted by human activities over the last century. A multiproxy analysis of sediment core dated by ¹³⁷Cs, ²¹⁰Pb and ²²⁶Ra activities and based on sediment geochemistry and benthic foraminifera is here used to reconstruct the environmental changes and the variations of the Palaeo-Ecological Quality Status (Palaeo-EcoQS) during the last ~120 years. The Palaeo-EcoQS was reconstructed by applying the diversity index Exp(H'_bc) based on the benthic foraminiferal fauna. Specifically, the Ecological Quality Ratio (EQR) allowed to assess the Palaeo-EcoQS during the last ~120 years using local reference conditions. Based on our data, the pre-industrial period (~1883-1902) represents the reference conditions with "Good" Palaeo-EcoQS. The ~1902-1972 period coincides with the beginning of industrial operations and intensification of coastal urbanization leading to a deterioration of the environmental quality and Palaeo-EcoQS shifting to "Moderate" conditions. Dredging operations in 1972 led to increase the influences of adjacent sea that ultimately resulted in a "Good" Palaeo-EcoQS persisting up to the 1990s. Despite the preservation actions and recovery programs, the 1993-2012 period was characterized by an overall deterioration of the environmental conditions. Indeed, the reconstructed "Poor" to "Bad" Palaeo-EcoQS suggest the ineffectiveness of the remediation actions. This work confirmed that benthic foraminifera are reliable to evaluate EcoQS and Palaeo-EcoQS in estuarine ecosystems. Based on the present findings and previous studies showing the potential of fossil foraminifera to define in situ reference conditions, we recommend the inclusion of foraminifera in the list of biological quality elements within legislations concerning transitional and marine habitats.

Fish and crustacean biodiversity in an outer maritime estuary of the Pearl River Delta revealed by environmental DNA

Understanding the faunal community structure in the estuary would be crucial in assessing the health of the ecosystem. The poor visibility in the estuarine area due to the outflow from the Pearl River hinders the conventional visual census in assessing the megafaunal biodiversity. In this study, the fish and crustacean biodiversity of Hong Kong's western waters, i.e. the outer maritime estuary of the PRD, were studied through the metabarcoding of environmental DNA (eDNA). eDNA from the seawater and sediment samples was extracted from five sites in the region. After testing the performance of two genetic markers, amplicons of the cytochrome oxidase I, amplified by polymerase chain reaction, were subjected to Illumina high-throughput sequencing (MiSeq) analysis. A total of 22 fish species from 17 families and 34 crustacean species from 27 families were identified by blasting the sequences against the NCBI GenBank database, demonstrating segregation between samples from different sites. This study provides insight on the detail distribution of fish assembly in PRD, when compared with a previous eDNA study in the inner brackish PRD.

Coastal restoration evaluated using dominant habitat characteristics and associated fish communities

Increasing coastal populations and urban development have led to the loss of estuarine habitats for fish and wildlife. Specifically, a decline in complexity and heterogeneity of tidal marshes and creeks is thought to negatively impact fish communities by altering the function of nursery grounds, including predator refuge and prey resources. To offset these impacts, numerous agencies are restoring degraded habitats while also creating new ones where habitat has been lost. To improve understanding of what contributes to a successful restoration, six quarterly sampling events using two gear types to collect small- and large-bodied fishes were conducted to compare the fish community structure and habitat characteristics at three natural, three restored, and three impacted (i.e. ditched) areas along the coast of Tampa Bay, Florida. Overall, impacted sites had significantly lower small-bodied and juvenile fish diversity than natural and restored areas, while restored sites harbored a greater number of fish species than impacted sites for both large- and small-bodied fish. Habitat features such as shoreline slope differentiated impacted and restored from natural areas. Although we did not find a direct correlation, habitat heterogeneity likely played a role in structuring fish communities. These findings provide guidance for future coastal restoration or modification of existing projects. Specifically, the habitat mosaic approach of creating a geographically compact network of heterogenous habitat characteristics is likely to support fish diversity, while decreasing shoreline slope in a greater amount of area within coastal wetland restorations would more closely mimic natural areas.

Multidisciplinary study to monitor consequences of pollution on intertidal benthic ecosystems (Hauts de France, English Channel, France): Comparison with natural areas

The intertidal areas of the Hauts-de-France (English Channel - France) stand out for the occurrence of fragile ecosystems that are exposed to natural and human-induced stress. Over the last two centuries, the northern part of this region has experienced a strong human pressure, with the settlement of numerous activities (i.e., metallurgic factories, harbors, embankments). On the contrary, the southern part includes mostly natural areas. The whole region is influenced by a macrotidal regime. A multidisciplinary approach based on sedimentological (grain-size), geochemical (trace metals, biomarkers) and biological (foraminifera) proxies was used to unravel the contrasting environmental conditions in the Hauts-de-France. Three foraminiferal-types communities, which reflect different ecological characteristics at regional scale, were identified: 1) estuarine macrotidal assemblages (Haynesina germanica associated to Elphidiidae) in low impacted estuaries; 2) industrial-perturbed assemblages (H. germanica and Cribroelphidium excavatum) in harbor areas; and 3) infaunal-dominant assemblages (Bolivina variabilis and B. pseudoplicata) in embankment areas. The outcomes of this study show that a multiproxy procedure needs to be adopted for properly characterizing intertidal ecosystems, where human impacts and natural stresses overlap and are hard to disentangle.

Comparing structural and functional approaches to distinguish benthic communities from eutrophic and non-eutrophic estuaries

The performance of three approaches for macrobenthic classification in distinguishing communities subjected to different environmental conditions was compared: i) the traditional species-based approach; ii) a tolerance-based approach according to ecological groups of the AMBI index; and iii) a character-based approach using biological traits. We used a hierarchical sampling design including three progressively smaller spatial scales, considering that the environmental degradation influence benthic communities at the larger spatial scale. Despite small-scale spatial variations, all approaches performed similarly, distinguishing eutrophic from non-eutrophic benthic communities as they varied significantly at the larger scale, corresponding to the scale at which human induced changes act. Our results suggest that all three methodological approaches could be used as operational criteria to assess estuarine environmental quality, and despite more meaningful, there is still a degree of subjectivity in functional approaches, associated to the lack of more detailed information on macrofaunal life-cycles and levels of tolerance to disturbance.

Defining ecological reference conditions in naturally stressed environments - How difficult is it?

The present study performed in Horten Inner Harbor (southern Norway) shows that foraminifera link the present-day Ecological Quality Status (EcoQS) to EcoQS of former times and, this way, bridge an important knowledge gap concerning determination of reference conditions, even in naturally stressed environments such as transitional waters and oxygen depleted habitats. In Horten Inner Harbor, geochemical data in the oldest deposits showed stable background concentrations for about 200 years (from about 1600 to 1800) before human activity became noteworthy, reflecting 'good' to 'high' status. Hence, it is reasonable that organisms, which lived in the area during the same nearly un-impacted time interval, represent the biologically defined reference conditions, irrespectively of whether the biotic indices are classified as 'good' or 'bad'. The present paper illustrates, with a conceptual model, how the retrospective foraminiferal biomonitoring method can be used to detect environmental perturbations in estuaries and meet the difficulties of the Estuarine Quality Paradox.

Can an oligotrophic coastal lagoon support high biological productivity? Sources and pathways of primary production

Coastal lagoons are among the most productive systems in the world. Many marine species make use of this by entering the lagoons as juveniles for nursery and growth before returning to the sea for reproduction. Humans take advantage of such fish migration processes by fishing, and exploit the high productivity for aquaculture activities. The Mar Menor is one of the largest coastal lagoons in the Mediterranean, sustaining relatively high fishing intensity despite the fact that it has traditionally been characterized as highly oligotrophic. However, in the last decades, this lagoon has suffered drastic changes induced by human activities. This has led to eutrophication, which started mainly as a consequence of changes in agricultural practices in the lagoon watershed, and triggered such fundamental changes in the system, as the mass development of jellyfish. The aim of this work is to capture and analyse the structure and functioning of the trophic web of the Mar Menor when it was still, in contrast to other coastal lagoons, oligotrophic, to provide a start point for analysing the consequences of changes in the distribution of macrophyte meadows and of eutrophication. We have compiled a detailed trophic model of this lagoon, comprising 94 compartments, using an ECOPATH model to capture the period 1980-1995. At this time the lagoon was an autotrophic system with a high net surplus of production that reached 9124.31gC/m2/year, while the production/biomass (P/B) ratio reached 34.56 and the total primary production/total respiration ratio was 7.01. The lagoon exported a 38.46% of total flows, including the catch by fishing, and 44.40% went to detritus. The primary production was mainly benthic (99.4%) due to the microphytobenthos and macrophytes. However, despite the fact that total fishery landings in the study period ranged between 144,835.5 and 346,708.5 kg, the gross efficiency was low, making up only 0.005% of the net primary production. This could partly be explained by the high trophic level of the fish catch (2.9), but mainly because most of the primary production (10,532.06 gC/m2/year) went directly to the detritus pool and was accumulated in the sediment in the Caulerpa prolifera meadows. We suggest several reasons why such high productivity coincided with low chlorophyll concentrations and good overall water quality: 1) the domination of both benthic biomass and primary production over pelagic ones with a high biomass of filter feeders, detritus feeders and scavengers, 2) high species diversity, complex and long food webs characterized by low connectance,3) the export of a significant part of the production from the system, and 4) the accumulation of surplus organic matter (as detritus) in sediments. We compare the food web of the Mar Menor in this mentioned oligotrophic stage to those of ten other lagoons in pursuit of more general implications regarding lagoon ecosystem functioning.

Factors structuring spatio-temporal dynamics of macrobenthic communities of three differently modified tropical estuaries

Tropical estuaries of industrialized northwest coast of India, subject to seasonal and multifarious anthropogenic interventions, are poorly studied. Three estuaries, Ulhas, Amba and Savitri were investigated seasonally to identify the principal factors among natural and anthropic stressors that shaped spatio-temporal macrobenthic patterns. The macrobenthic community structure and chemical parameters differed significantly between estuaries, zones and seasons. Multivariate dispersions were significant between the estuaries whereas for the zones and seasons, significant variability was nonexistent. Multivariate regression analysis indicated that both natural and anthropogenic drivers influenced the spatio-temporal variability of macrobenthos of Ulhas and Amba. In Savitri, no anthropogenic factor was significantly influential. Salinity explained a greater proportion of the variability of macrobenthic structure than other factors in all estuaries. The pollution tolerant species responded largely to salinity changes and were observed to inhabit specific salinity zones. Thus, the spatio-temporal patterns of the estuarine macrobenthos were primarily dictated by the salinity.

Response of benthic macrofauna to multiple anthropogenic pressures in the shallow coastal zone south of Sfax (Tunisia, central Mediterranean Sea)

Anthropogenic activities including coastal industries, urbanization, extensive agriculture and aquaculture as well as their cumulative impacts represent major sources of perturbation of marine coastal systems. Macrobenthic communities are useful ecological indicators for monitoring the health status of marine environments (or polluted environments). The present study reports, for the first time, the response of benthic macrofauna sampled during two years survey (2015-2016) to multiple anthropogenic pressures on the coastal zone south of Sfax (Tunisia). A total of 12 stations were monitored seasonally at locations downstream from the main potential sources of disturbance. 106 macrobenthos taxa, belonging to six animal phyla and 70 families, were identified with a dominance of polychaetes (42%), crustaceans (35%) and molluscs (18%). We used an ANOVA test and cluster analysis to identify spatial gradient linked to environmental and anthropogenic factors, including depth, sedimentary texture and anthropogenic activities (i.e. phosphogypsum discharges).The macrofauna present lowest species number and abundance on stations undergoing anthropogenic inputs, which are extremely polluted by heavy metals (Cd, Cu, F and N) and excess of organic matter. Univariate parameters reveal a general trend of increasing species diversity with increasing distance from the pollution source. The polluted stations are strongly dominated by carnivores, and selective deposit feeders, and more closely linked to the availability of trophic resources than to anthropogenic constraints. The seasonal changes in macrobenthic abundance, diversity indices and community structure are mainly linked to the biological cycle (e.g. recruitment events) of the dominant species. Biotic indices (AMBI and BO2A) classified the coastal zone south of Sfax as moderate and good ecological status. This study suggests that initiating a long-term monitoring programme would improve our understanding of the temporal changes of macrobenthic communities of this ecosystem, contributing to the assessment of effective management and conservation measures in this disturbed area.

The difficulty of disentangling natural from anthropogenic forcing factors makes the evaluation of ecological quality problematic: A case study from Adriatic lagoons

The complex and dynamic nature of transitional ecosystems pose problems for the assessment of the Ecological Quality Status required by the European Water Framework Directive (WFD; 2000/60/EC). In six Adriatic lagoons, Ecological Quality Status was studied by comparing a biotic index based on macrophytes (MaQI), and three indices based on invertebrates (M-AMBI, M-bAMBI, and ISD). Ecological Status evaluated though MaQI and ISD resulted in quite degraded ecosystems (moderate/poor/bad), with only opportunistic algae and macrobenthic communities dominated by small size classes. Those results were supported by physico-chemical parameters, indicating high nutrients inputs, and anthropogenic pressures related with agriculture and fishery activities. Ecological Status obtained with M-AMBI and M-bAMBI was higher, with some sites reaching even the "good" status. The best response to anthropogenic pressures, in terms of a pressure index, was obtained by M-AMBI and M-bAMBI. Nevertheless, the response of used metrics (such as AMBI and bAMBI) to environmental variables not related to anthropogenic impact, and the high heterogeneity of physical-chemical conditions within lagoons, represent potential problems for the correct evaluation of Ecological Status of transitional waters. When different metrics give different responses it becomes a problem for managers who cannot easily make a decision on the remedial measures. The disagreement among indices arose because of the different response of biological elements to different stressors, and because the different indices based on macroinvertebrates focused on different aspects of the community, providing complementary information. So urge the need to find alternative approaches for a correct assessment of Ecological Status, with the combination of different biological elements, and considering the development of new indices (e.g. M-bAMBI) or refinement of the existing ones.

Structure of the benthic macrofauna of an anthropogenic influenced area: Skhira Bay (Gulf of Gabès, central Mediterranean Sea)

Skhira Bay located in the Gulf of Gabès, on the southeastern coast of Tunisia, is an important area in terms of its dense vegetation coverage, wide continental shelf, and fisheries resources. However, this area with a typically micro-tidal range is subject to intensive anthropogenic pressures: soft bottom trawling, chemical pollution from phosphoric acid production, and shipping activity. The present study is the first investigation of the structure of the benthic macrofauna on this part of the Tunisian coast. In April 2010, 28 stations were sampled along four transects from the phosphogypsum outfall on an inshore-offshore gradient. A total of 239 macrobenthos taxa, belonging to nine zoological groups and 140 families, were identified with a dominance of polychaetes (33.5%), crustaceans (29.4%), and mollusks (19.6%). Results show that the stations facing the phosphogypsum discharges are the most disturbed and characterized by a poorly diversified macrofauna. The macrofauna is dominated by carnivores, suspension feeders, and selective deposit feeders, and seems to be linked more to the availability of trophic resources than to disturbance. Four benthic assemblages are identified using Cluster and MDS analyses linked to edaphic factors, such as sediment structure, organic matter content, inshore/offshore gradient, and the proximity of the phosphogypsum outfall. The biotic indices (AMBI and BO2A) calculated from macrofauna data show that the ecological status of Skhira Bay varies overall from moderate to good. This study suggests initiating a long-term monitoring program to improve our understanding of the temporal changes of this ecosystem, to recommend the necessary conservation measures in this area of high-value natural heritage.

Beyond classic ecological assessment: The use of functional indices to indicate fish assemblages sensitivity to human disturbance in estuaries

Assessing ecological health of aquatic ecosystems is crucial in the current context of biodiversity loss to guide and prioritize management actions. Although several fish-based indices were developed to assess the ecological status of estuarine ecosystems, they do not provide guidance on the causal responses of communities to disturbances. The functional trait-based approach provides an understanding of how human disturbance affects the composition of biological and ecological traits in assemblages, as well as their consequences for ecosystem functioning. Here, we evaluate the responses of fish assemblages to human disturbance in 30 French estuaries using several taxonomic and functional indices (e.g. diversity, evenness or redundancy). We tested whether these indices can provide additional information on the human impacts and health of assemblages that are not reflected by the ecological indicator (fish-based index ELFI). Results indicated that high values of local human disturbances were associated to a decrease in fish abundance, decrease in species richness and reduced functional redundancy, whereas taxonomic and functional evenness increased. In contrast, the functional richness remained stable suggesting that the functional traits of species removed by stressors were maintained by more tolerant species. Indeed, we found that the local disturbances mainly resulted in a decrease in the proportions of small benthic species feeding on macro-invertebrates, which were dominant in the studied estuaries. Some functional alterations were detected by the fish-based index, but the decline of functional redundancy was not reflected, highlighting a serious concern for management. Indeed, the abrupt collapse of functional redundancy in response to local disturbances can decrease the ability of assemblages to maintain certain species traits in the face of future environmental disturbance, including climate change. From a management perspective, the application of such functional redundancy measure in monitoring programs can help stakeholders identify sensitive areas where conservation efforts need to be planned.

Testing performances of marine benthic biotic indices under the strong seasonality in the tropical intertidal habitats, South Andaman, India

Understanding the natural variability and its influence on the performance of marine biotic indices used for the health assessment of marine ecosystem is the prime concern. This study addresses the seasonal variability of univariate and multimetric indices by using macrobenthic data collected from three intertidal habitats for two years (July 2013-July 2015). The univariate indices viz., abundance, richness, Shannon index and ES ₍₁₀₀₎ showed strong seasonal variability. For the multimetric indices, the seasonal variability was low and appeared site specific. W-statistics, AMBI and M-AMBI showed highest constancy whilst BENTIX and BOPA exhibited wide - ranging. A general tendency could be inferred as majority of indices showed improvement in benthic quality (poor - moderate and good - high) from turbulent monsoon to stable dry period. The results are discussed concerning possible consequences especially related to the benthic community and biotic indices in intertidal habitats under the influence of sewage discharge and monsoonal effects.

Maintenance dredging impacts on a highly stressed estuary (Guadalquivir estuary): A BACI approach through oligohaline and polyhaline habitats

Understanding the effects of dredging in estuaries is a hard task due to the difficulty of implementing an adequate environmental diagnosis, as a consequence of the salinity gradient and anthropogenic disturbances. To assess the effects of maintenance dredging work on the Guadalquivir estuary (southwestern Spain), we used a Before-After-Control-Impact (BACI) approach to determine both direct and indirect effects in two salinity ranges. No effects were found on water and sediment physicochemical characteristics. The small impacts on dredged areas were followed by a rapid recovery of opportunistic species. The poor status of the benthos does not permit the detection of significant effects on macrofaunal community structure. The use of stable isotopes analysis to determine impacts on food web structure showed that changes over time seem to be explained by natural temporal variation rather than the dredging works. This paper emphasises the need to define proper management and conservation plans to improve the status of the benthic communities of the Guadalquivir estuary.

Effects of dams on downstream molluscan predator-prey interactions in the Colorado River estuary

River systems worldwide have been modified for human use and the downstream ecological consequences are often poorly understood. In the Colorado River estuary, where upstream water diversions have limited freshwater input during the last century, mollusc remains from the last several hundred years suggest widespread ecological change. The once abundant clam Mulinia modesta has undergone population declines of approximately 94% and populations of predators relying on this species as a food source have probably declined, switched to alternative prey species or both. We distinguish between the first two hypotheses using a null model of predation preference to test whether M. modesta was preyed upon selectively by the naticid snail, Neverita reclusiana, along the estuary's past salinity gradient. To evaluate the third hypothesis, we estimate available prey biomass today and in the past, assuming prey were a limiting resource. Data on the frequency of drill holes-identifiable traces of naticid predation on prey shells-showed several species, including M. modesta, were preferred prey. Neverita reclusiana was probably able to switch prey. Available prey biomass also declined, suggesting the N. reclusiana population probably also declined. These results indicate a substantial change to the structure of the benthic food web. Given the global scale of water management, such changes have probably also occurred in many of the world's estuaries.

Sediment quality in a metal-contaminated tropical bay assessed with a multiple lines of evidence approach

A sediment quality assessment was performed near to the main industrial source of metal contamination in Sepetiba Bay, Brazil, which represents one of the worst cases of trace metal contamination reported for coastal areas. Acute and chronic toxicity tests, benthic fauna community analysis and metal bioavailability evaluations were applied to identify risks to the benthic community. Significant amphipod mortality was observed close to the major pollution source and lower copepod fertility was observed for all stations. Equilibrium-partitioning and biotic-ligand models to predict pore water metal toxicity, which were based on acid-volatile sulfide (AVS) and organic carbon fraction (f_OC) normalization approaches, suggested that metals are not likely to be available in sediment pore water. However, Cd, Pb and Zn concentrations were mainly (>50%) weakly bound to sediments, suggesting high potential bioavailability. Linking the chemical results with ecotoxicological responses, we observed that sediment-feeding organisms presented acute and chronic toxicities that were positively correlated to the metal concentrations in the sediments. Additionally, benthic fauna composition was dominated by tolerant species, revealing a trophic structure response to environmental contamination. These results reinforce the necessity of a multiple lines of evidence approach to establish sediment quality and to support environmental management decisions that are based on observed effects and potential extrapolation scenarios into the future.

Relationship between structure of macrobenthic assemblages and environmental variables in shallow sublittoral soft bottoms

We establish baseline knowledge of abundance, diversity and multivariate structure of macrobenthos from shallow sublitoral soft bottoms in the North Portuguese coast and elucidate main environmental factors that shape their spatial patterns. In this area distribution of soft bottoms is patchy, surrounded by boulders and rocky substrates. This particular landscape and the lack of significant anthropogenic disturbances are values for the conservation of this habitat. Sediment and physicochemical properties of the water column were studied to provide models for each studied macrobenthic variable. Our models highlighted that most of variation (59%-72%) in macrobenthic spatial patterns was explained by the studied environmental variables. Sedimentary variables were more relevant that those of the water column. Therefore, disturbances affecting sedimentary environment could cause dramatic changes in macrobenthic assemblages because of the limited availability of soft bottoms in the area. In this way, results are useful to adopt right management and conservation strategies.

What are the factors driving long-term changes of the suprabenthos in the Seine estuary?

A Before/During/After Control-Impact approach is used to assess the effects of Port 2000 on the suprabenthos in the North Channel (NC) of the Seine estuary during the period from September 2001 to October 2015. Since the beginning of Port 2000 construction (2002-2005), the NC is affected by an increase of salinity (marine influence) and input of sand. The suprabenthos changes are mainly characterised by an increase in species richness in the upper part of the NC and a decrease in species density and biomass of the dominant mysid species over time. Multiple stressors (natural and anthropogenic) have been operating simultaneously (hydrological changes, construction of Port 2000, supplementary dredging) rendering the interpretation of the biological changes difficult. Thus, the present results evidenced a combination of changes in the Seine Estuary not only attributed to the impact of the Port 2000 construction.

Integrated monitoring of chemicals and their effects on four sentinel species, Limanda limanda, Platichthys flesus, Nucella lapillus and Mytilus sp., in Seine Bay: A key step towards applying biological effects to monitoring

The International workshop on Integrated Assessment of CONtaminants impacts on the North sea (ICON) provided a framework to validate the application of chemical and biological assessment thresholds (BACs and EACs) in the Seine Bay in France. Bioassays (oyster larval anomalies, Corophium arenarium toxicity assay and DR Calux) for sediment and biomarkers: ethoxyresorufin-O-deethylase (EROD) activity, acetylcholinesterase (AChE) activity, lysosomal membrane stability (LMS), DNA strand breaks using the Comet assay, DNA adducts, micronucleus (MN), PAH metabolites, imposex, intersex and fish external pathologies were analysed in four marine sentinel species (Platichthys flesus, Limanda limanda, Mytilus sp. and Nucella lapilus). Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals were analysed in biota and sediment. Results for sediment and four species in 2008-2009 made it possible to quantify the impact of contaminants using thresholds (Environmental Assessment Criteria/EAC₂₀₀₈: 70% and EAC₂₀₀₉: 60%) and effects (EAC₂₀₀₈: 50% and EAC₂₀₀₉: 40%) in the Seine estuary. The Seine estuary is ranked among Europe's most highly polluted sites.

Differences in the structure of copepod assemblages in four tropical estuaries: Importance of pollution and the estuary hydrodynamics

We examined the relationship between pollution and structure of copepod assemblages in estuaries, using sampling standardization of salinity range to reduce the effects of "Estuarine Quality Paradox". Copepod assemblages were analyzed in four Southeast Brazilian estuaries with different water quality levels and different hydrodynamic characteristics. The pollution negatively impacted the descriptors of the assemblage structure. The distribution of structure of copepod assemblages also showed a main separation trend between the most polluted estuaries and those less polluted. Temperature was the main factor affecting the assemblage structuring in the four estuaries. This factor acted in synergism with the effects of pollution impact and physical characteristics of the estuaries on the structure of copepod assemblages, supporting the potential vulnerability of coastal environments due to nutrient enrichment associated with climate change. Our study demonstrated the importance of sampling standardization of the salinity range in estuaries for reliable analysis of pollution effects on biota.

Structuring factors of the spatio-temporal variability of macrozoobenthos assemblages in a southern Mediterranean lagoon: How useful for bioindication is a multi-biotic indices approach?

The authors investigated the impact of the extension of the El Kantra Channel on the composition and structure of macrobenthic assemblages in Boughrara Lagoon (Gulf of Gabes, Tunisia along with the use of 4 biotic indices (AMBI, BENTIX, M-AMBI and TUBI). Thirteen stations were sampled seasonally in 2012-2013. Forty-one species were found in 2012-2013 not recorded in 2009-2010, including 20 species of polychaetes belonging to the trophic groups of deposit-feeders and carnivores which are expected to increase in areas disturbed by organic pollution. During the survey, we recorded a high fish mortality, essentially caused by the development of harmful algal blooms (HAB) which increased organic matter deposition, thus inducing polychaete development. This seems to weaken the bio-indicating power of biotic indices used here which, paradoxically, classified all sampled stations at a high ecological status. A review of these indices and their applicability to all marine environments is recommended.

Is meiofauna community structure in Artificial Substrate Units a good tool to assess anthropogenic impact in estuaries?

The applicability of estuarine meiofauna and harpacticoid copepods' communities in an artificial substrate unit (ASU) was assessed and compared to natural substrates (sediment and pneumatophores) as a tool to discern estuaries under different types of anthropogenic impacts. The ASU's replicates demonstrated a low variation of density among replicates when considering the total meiofauna and copepod species, which was reflected by a great similarity within the samples. In relation to the most abundant groups found, the ASU samples properly represented the natural substrates, even though nematodes were poor colonizers. That the ASU only showed significant differences between areas suggested that standard substrates could more efficiently detect the differences between communities and pointed toward the applicability of ASUs meiobenthic communities as useful tools for impact studies.

Consistent patterns of variation in macrobenthic assemblages and environmental variables over multiple spatial scales using taxonomic and functional approaches

Spatial variability of environmental factors and macrobenthos, using species and functional groups, was examined over the same scales (100s of cm to >100 km) in intertidal sediments of two transitional water systems. The objectives were to test if functional groups were a good species surrogate and explore the relationship between environmental variables and macrobenthos. Environmental variables, diversity and the multivariate assemblage structure showed the highest variability at the scale of 10s of km. However, abundance was more variable at 10s of m. Consistent patterns were achieved using species and functional groups therefore, these may be a good species surrogate. Total carbon, salinity and silt/clay were the strongest correlated with macrobenthic assemblages. Results are valuable for design and interpretation of future monitoring programs including detection of anthropogenic disturbances in transitional systems and propose improvements in environmental variable sampling to refine the assessment of their relationship with biological data across spatial scales.