The response of benthic macrofauna to anthropogenic stress in Narragansett Bay, Rhode Island: a review of human stressors and assessment of community conditions

Past-President address: My journey in microbial ecology-footprints in the sand, island hopping, supply chains, and technology bridges

This paper highlights and honors the connectivity among protistan researchers, using my own research journey as a backdrop, with attention to the supply chain of ideas, supporters, and other influencers who helped to shape and guide my career by sharing their ideas, protocols, skills, and enthusiasm. In looking back at the journey, the supply chain in my career has also included changes in the conceptual framework for my research studies, converging with a continuous flow of ideas and support from colleagues and mentors. To illustrate the complex map of ideas and supporters, this paper will examine technological advances, paradigm shifts in ecological constructs, geographical considerations, breakthroughs in peritrich biology, and the importance of an integrated perspective as we navigate the changing realities of today's scientific challenges.

Spatiotemporal variability on local-regional scale in subtidal meiofaunal assemblages along the southern coast of Korea

This study was conducted to investigate the spatiotemporal variability in subtidal meiofaunal assemblages off the southern coast of Korea at local and regional scales. Abiotic and biotic samples were collected by site (three sites at least 10 km apart) within region (three coastal regions at least 50 km apart) over 7 years (2015-2021). The density and taxon richness of meiofaunal assemblages differed significantly among sites, but not among regions or years. The meiofaunal assemblage composition differed significantly among sites, regions, and years. A distance-based multivariate multiple regression analysis revealed that the mean sediment grain size and total nitrogen, lead, nickel, chromium, and aluminum concentrations were key environmental variables determining the variation of the meiofaunal assemblages. This study can provide basic ecological data for understanding the spatiotemporal distribution of meiofauna assemblages and aid in the development of management strategies to mitigate marine pollution on the southern coast of Korea.

Combined effects of climate change and environmentally relevant mixtures of endocrine disrupting compounds on the fitness and gonads' maturation dynamics of Nucella lapillus (Gastropoda)

Coastal areas are affected by multiple stressors like climate change and endocrine disruptors (EDCs). In the laboratory, we investigated the combined effects of increased temperature and EDCs (drospirenone and mercury) on the fitness and gonads' maturation dynamics of the marine gastropod Nucella lapillus for 21 days. Survival was negatively affected by all the stressors alone, while, in combination, a synergistic negative effect was observed. Both chemicals, as single factors, did not cause any effect on the maturation stage of ovaries and testis. However, in the presence of a higher temperature, it was clear a delay in the maturation stage of the ovaries, but not in the testis, suggesting a higher negative impact of the stressors in females than in males. In summary, drospirenone caused a low negative impact in aquatic species, like gastropods, but in combination with other EDCs and/or increased temperature can be a matter of concern.

Taxonomic and functional macrofaunal diversity along a gradient of sewage contamination: A three-year study

We investigated the structural and functional changes of the soft-bottom macrofaunal community following the improvement of a wastewater treatment-WWT plant. The macrofauna was collected at increasing distance from the main outfall in 2018, 2019, and 2021. Organic matter and nutrients were analysed in the water column near the outfalls to detect possible changes due to the improved treatment. We examined Functional Entities-FEs (i.e. a unique combination of species functional traits), species richness, Shannon-Wiener diversity-H', and taxonomic and functional β-diversity. From 2018 (before the year of the treatment change), to 2021, we noted a gradual decrease of organic carbon in the water column. In contrast, sediment characteristics (i.e. grain-size) did not change before and after treatment enhancement, with the exception of redox potential. Species richness and FEs gradually increased moving far from the source of organic contamination and after wastewater treatment enhancement, especially near the outfall. We observed different phases of macrofaunal succession stage after the WWT amelioration. A 'normal stage', i.e. slightly lower species richness, was reflected in decreasing functional richness. Higher taxonomic β-diversity values with significant turnover components indicated that the community was subjected to broad changes in species composition. However, functional β-diversity did not follow the same pattern. After treatment improvement, modified environmental conditions led to the establishment of new species, but with the same functions. Towards 2021, the community improved its resilience by increasing functional redundancy and reduction of vulnerability, which enhanced community stability. The latter was also reflected in the well-balanced proportion of macrofaunal feeding habits after the WWT upgrade. Integrating the classical taxonomic approach with the analysis of FEs, and environmental characteristics can provide an accurate insight into macrofauna sensitivity to stressors that are likely to lead to changes in the ecological state of an area.

The Fundão dam failure: Iron ore tailing impact on marine benthic macrofauna

The Fundão dam failure, the worst environmental disaster in Brazilian history, launched 50 million m³ of iron ore tailings mud through the Doce River, reaching the Atlantic Ocean. Generally, mine tailings increase the sediment inflow, leading to mud burial of epibenthic macrofauna, and the raise of metal(oid)s concentration causing macrofauna long-term changes. After almost four years, tailings mud was still spreading on the Doce River Shelf, while impacts on marine macrofauna were still unknown. Herein, the IMS index (a tracer of Fundão dam tailings mud), sediment variables, organic pollutants, and metal(oid)s were integrated to uncover the drives of macrofauna structure from Costas da Algas to Abrolhos bank MPAs. Tailings mud was present only in Doce River Mouth and Degredo, organic pollutants and metal(oid)s above safety levels were concentrated in those same areas. Tailings mud (IMS index) drastically reduced species richness and diversity, favoring the abundance of opportunistic species. Mud, IMS index and Al, Ba, and V, metal(oid)s linked to dam failure, structured macrofauna composition in this impacted area, dominated by resistant groups as Nuculidae, Spionidae, and Magelonidae. Conversely, an opposite pattern was found for further and deeper sites with high CaCO3 content and total nitrogen that also showed large grain size, in areas known to harbour biogenic structures, sustaining a macrofauna composition distinct from the impacted areas, dominated by Syllidae and Crassatellidae, sensitives to impacts. Macrofauna composition was most structured by sediment variables, followed by the intersection between metal(oid)s-IMS and Mud, both gradients acting almost entirely on a broad spatial scale. Benthic macrofauna at the Doce River Shelf is still impacted by Fundão dam tailings mud, even after almost four years of the disaster, and may continue to, since the influx of tailings does not stop, and sediment resuspension is a recurrent source for those impacts.

Assessing the sewage discharge effects on soft-bottom macrofauna through traits-based approach

We assessed the effect of sewage-derived materials on the structural and functional attributes of the soft-bottom macrofauna at an increasing distance from the entire diffusion area. Our results showed clear spatial changes of macrofaunal density and biomass along the distance gradient from the main outfall. High values of biodiversity, species composition, and species linked to organic enrichment near the duct suggested that moderate organic stress affected this community. The traits analysis abundance-based, compared to biomass-based one, distinguished most clearly sewage contamination conditions. Functional diversity displayed spatial patterns with higher values in the less impacted sites and was significantly related to species numbers and the biotic indices (like M-AMBI). This approach is ideal for detecting macrofaunal functional changes due to sewage contamination. Thus, we infer that traits analyses could offer great potential for environmental assessment and monitoring of coastal areas influenced by human activities.

Benthic macroinvertebrate community response to environmental changes over seven decades in an urbanized estuary in the northeastern United States

Narragansett Bay is representative of New England, USA urbanized estuaries, with colonization in the early 17th century, and development into industrial and transportation centers in the late 18th and early 20th century. Increasing nationwide population and lack of infrastructure maintenance led to environmental degradation, and then eventual improvement after implementation of contaminant control and sewage treatment starting in the 1970s. Benthic macroinvertebrate community structure was expected to respond to these environmental changes. This study assembled data sets from the 1950s through 2010s to examine whether quantitative aggregate patterns in the benthic community corresponded qualitatively to stressors and management actions in the watershed. In Greenwich Bay and Providence River, patterns of benthic response corresponded to the decline and then improvement in sewage treatment at the Fields Point wastewater treatment plant. In Mount Hope Bay, the benthos corresponded to changes in bay fish populations due to thermal discharge from the Brayton Point power plant. The benthos of the Upper West Passage corresponded to climatic changes that caused regime shifts in the plankton and fish communities. Future work will examine the effects of further environmental improvements in the face of continued climatic changes and population growth.

Blue crab (Callinectes sapidus) population structure in southern New England tidal rivers: Patterns of shallow-water, unvegetated habitat use and quality

The blue crab, Callinectes sapidus, has a broad geographic distribution encompassing coastal waters of the eastern United States and Gulf of Mexico, but intraspecific patterns of habitat use and quality are lacking at northern latitudes. This study examined the population structure of blue crabs in the Seekonk and Taunton Rivers (Rhode Island and Massachusetts, USA): two tidally influenced rivers contiguous with the Narragansett Bay Estuary and dominated by shallow-water, unvegetated habitats. Crabs were collected fortnightly from May through August (2012-2016), and abundance- and growth-based metrics were used to assess riverine habitat use and quality. These metrics were also analyzed with respect to crab life history traits and in situ abiotic conditions to elucidate patterns of habitat selection throughout ontogeny. Crabs measuring 8 to 185 mm carapace width (CW; n = 2,577) were collected, and two distinct age-classes occupied the rivers during the spring and summer (maximum abundance ~ 5 crabs/10 m²). The younger age-0+ cohort was numerically dominant (~ 88% of total catch) and comprised of male and juvenile female crabs (mean ± SD abundance = 0.28 ± 0.26 males/10 m² and 0.14 ± 0.12 juvenile females/10 m²). Males accounted for the majority of age-1+ crabs (~ 83% of cohort), yet sexually mature females were also observed (9% of cohort; mean ± SD abundance = 0.04 ± 0.06 adult females/100 m²; size at 50% maturity ± 95 CI = 129.0 ± 0.2 mm CW). Crabs were spatially segregated along a salinity gradient with males and juvenile females prevalent in oligohaline waters (upper river salinity ~ 5 ppt) and adult females mainly concentrating in higher salinity areas (mid- and lower river salinity ~ 11-21 ppt). Seasonal and interannual patterns in crab abundance also differed by sex and ontogeny. Peak catches of males and juvenile females occurred during the spring and mid-summer, and annual abundances were positively related to dissolved oxygen (DO) concentrations. In contrast, mature females were most abundant during August and years with elevated water temperatures. The absolute and relative growth rates of juvenile crabs equaled 0.9 ± 0.3 mm CW/day and 1.5 ± 0.6 % CW/day, respectively, and were directly related to DO levels. A synoptic examination of crab abundance and growth across a broad geographic range indicated that shallow-water, unvegetated habitats presently serve as functional nurseries in southern New England tidal rivers.

Functional plasticity in oyster gut microbiomes along a eutrophication gradient in an urbanized estuary

Background

Oysters in coastal environments are subject to fluctuating environmental conditions that may impact the ecosystem services they provide. Oyster-associated microbiomes are responsible for some of these services, particularly nutrient cycling in benthic habitats. The effects of climate change on host-associated microbiome composition are well-known, but functional changes and how they may impact host physiology and ecosystem functioning are poorly characterized. We investigated how environmental parameters affect oyster-associated microbial community structure and function along a trophic gradient in Narragansett Bay, Rhode Island, USA. Adult eastern oyster, Crassostrea virginica, gut and seawater samples were collected at 5 sites along this estuarine nutrient gradient in August 2017. Samples were analyzed by 16S rRNA gene sequencing to characterize bacterial community structures and metatranscriptomes were sequenced to determine oyster gut microbiome responses to local environments.

Results

There were significant differences in bacterial community structure between the eastern oyster gut and water samples, suggesting selection of certain taxa by the oyster host. Increasing salinity, pH, and dissolved oxygen, and decreasing nitrate, nitrite and phosphate concentrations were observed along the North to South gradient. Transcriptionally active bacterial taxa were similar for the different sites, but expression of oyster-associated microbial genes involved in nutrient (nitrogen and phosphorus) cycling varied throughout the Bay, reflecting the local nutrient regimes and prevailing environmental conditions.

Conclusions

The observed shifts in microbial community composition and function inform how estuarine conditions affect host-associated microbiomes and their ecosystem services. As the effects of estuarine acidification are expected to increase due to the combined effects of eutrophication, coastal pollution, and climate change, it is important to determine relationships between host health, microbial community structure, and environmental conditions in benthic communities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-020-00066-0.

How do spatial and environmental factors shape the structure of a coastal macrobenthic community and meroplanktonic larvae cohort? Evidence from Daya Bay

We examined the relative importance of spatial processes (dispersal-related) and environmental processes (environmental selection-related) in community structure for macrobenthos (including juveniles and adults) and meroplanktonic larvae in the subtidal areas of Daya Bay, China. We found that both macrobenthos and meroplanktonic larvae showed similar spatial patterns, both following the distance-decay relationship. The results of variation partitioning analysis (VPA) showed the roles of both spatial and environmental factors in governing the assembly of both communities, although both explained only a small (slightly larger for spatial factor) fraction of the community variation. We also found that macrobenthos were more affected by spatial processes than meroplanktonic larvae. In addition, we highlight that the mechanisms determining community structure change according to the spatial extent considered.

Population genomics of rapid evolution in natural populations: polygenic selection in response to power station thermal effluents

BACKGROUND

Examples of rapid evolution are common in nature but difficult to account for with the standard population genetic model of adaptation. Instead, selection from the standing genetic variation permits rapid adaptation via soft sweeps or polygenic adaptation. Empirical evidence of this process in nature is currently limited but accumulating.

RESULTS

We provide genome-wide analyses of rapid evolution in Fundulus heteroclitus populations subjected to recently elevated temperatures due to coastal power station thermal effluents using 5449 SNPs across two effluent-affected and four reference populations. Bayesian and multivariate analyses of population genomic structure reveal a substantial portion of genetic variation that is most parsimoniously explained by selection at the site of thermal effluents. An FST outlier approach in conjunction with additional conservative requirements identify significant allele frequency differentiation that exceeds neutral expectations among exposed and closely related reference populations. Genomic variation patterns near these candidate loci reveal that individuals living near thermal effluents have rapidly evolved from the standing genetic variation through small allele frequency changes at many loci in a pattern consistent with polygenic selection on the standing genetic variation.

CONCLUSIONS

While the ultimate trajectory of selection in these populations is unknown and we survey only a minority of genomic loci, our findings suggest that polygenic models of adaptation may play important roles in large, natural populations experiencing recent selection due to environmental changes that cause broad physiological impacts.

Six decades of change in pollution and benthic invertebrate biodiversity in a southern New England estuary

Pollution has led to a decline of benthic invertebrate biodiversity of Narragansett Bay, raising questions about effects on ecosystem functions and services including shellfish production, energy flow to fishes, and biogeochemical cycles. Changes in community composition and taxonomic distinctness (biodiversity) were calculated from the 1950s-when quantitative benthic invertebrate data first became available-to 2015. Change in community composition of the bay was correlated with changes in dissolved inorganic nitrogen, dissolved oxygen, and sediment contaminants. A mid-bay reference site showed moderate changes in community composition but no change in biodiversity. In contrast, a more impacted site in the upper bay showed substantial differences in community composition over time and a decline in taxonomic distinctness. Bay-wide, as inputs of some stressors such as nutrients and sediment contaminants have declined, there are signs of recovery of benthic biodiversity but other stressors such as temperature and watershed development are increasing.

A Random Forest approach to predict the spatial distribution of sediment pollution in an estuarine system

Modeling the magnitude and distribution of sediment-bound pollutants in estuaries is often limited by incomplete knowledge of the site and inadequate sample density. To address these modeling limitations, a decision-support tool framework was conceived that predicts sediment contamination from the sub-estuary to broader estuary extent. For this study, a Random Forest (RF) model was implemented to predict the distribution of a model contaminant, triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) (TCS), in Narragansett Bay, Rhode Island, USA. TCS is an unregulated contaminant used in many personal care products. The RF explanatory variables were associated with TCS transport and fate (proxies) and direct and indirect environmental entry. The continuous RF TCS concentration predictions were discretized into three levels of contamination (low, medium, and high) for three different quantile thresholds. The RF model explained 63% of the variance with a minimum number of variables. Total organic carbon (TOC) (transport and fate proxy) was a strong predictor of TCS contamination causing a mean squared error increase of 59% when compared to permutations of randomized values of TOC. Additionally, combined sewer overflow discharge (environmental entry) and sand (transport and fate proxy) were strong predictors. The discretization models identified a TCS area of greatest concern in the northern reach of Narragansett Bay (Providence River sub-estuary), which was validated with independent test samples. This decision-support tool performed well at the sub-estuary extent and provided the means to identify areas of concern and prioritize bay-wide sampling.

Metal uptake, oxidative stress and histopathological alterations in gills and hepatopancreas of Callinectes amnicola exposed to industrial effluent

Metal uptake by biota due to elevated environmental concentrations elicits oxidative stress and could lead to pathological outcomes. The relationship between the histopathological profile of hepatopancreas and gills and altered biochemical features (antioxidant enzymes i.e. GSH, GPx, CAT, SOD, lipid peroxidation (MDA) and serum protein) in the blue crab, Callinectes amnicola from contaminated parts of the Lagos Lagoon was investigated. Monthly crab, sediment and surface water samples were taken from effluent receiving areas of the Lagos lagoon i.e. Makoko, Okobaba, Iddo, Ikoyi and Mid-lagoon (control site) over an 18-month period and analyzed for metal levels (Pb, Cd, Zn and Cu). Significantly higher levels of GPx and lower levels of Pb, Zn and Cu was recorded in gills and hepatopancreas of crabs from the mid-lagoon compared to crabs from other sites. Reaction patterns of gills across the different sites of the lagoon included regressive (ranging from epithelial lifting, disruption of pilaster cells, detached cuticle to focal necrosis) and circulatory disruptions (oedema); increased activity of GSH and GPx in gills were positively correlated with lesions of lower importance factor. Reaction patterns in hepatopancreas were more regressive including vacuolation/infiltration of fatty lobules, necrosis, granuloma, disintegrated lumen, atrophied tubules and loss of lobular hepatocyte structure; increased activity of GSH, GPx and CAT were positively correlated with lesions of low importance factor in the hepatopancreas. Findings show that lesions in both gills and hepatopancreas of the blue crab could be associated with uptake of metals, depleted antioxidant activity and incidence of lipid peroxidation in tissue.

Sediment characteristics and benthic ecological status in contrasting marine environments of subtropical Hong Kong

Sediment characteristics and benthic communities on a finer sampling scale in four contrasting environments in subtropical Hong Kong were analyzed in summer and winter 2012. In two harbour habitats which suffered from historic sewage pollution or hypoxic events, organic carbon, nutrient and trace metal content in the sediment were significantly higher than that in an offshore area and a marine reserve. The relatively low organic and nutrient content in the offshore habitat could be resulted from enhanced resuspension of such materials from the seabed owing to intense water mixing and disturbance caused by bottom trawling. The biotic indices AMBI and M-AMBI were shown to be useful in assessing the benthic ecological status of these habitats. Such indices can also be more sensitive than sediment physico-chemical parameters in differentiating the response of macrofauna to seasonal changes in the benthic environment.

Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX

A combination of historical bivalve surveys spanning 30–50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration.

Is there a possibility of ranking benthic quality assessment indices to select the most responsive to different human pressures?

Although a plethora of benthic indices exist, there is no agreement on what index or indices should be used by environmental managers to establish benthic quality. The objective of this investigation was to rank 35 benthic quality assessment indices used in different countries to evaluate the impact produced by 15 different human pressures (including multipressure, aquaculture, sewage discharges, eutrophication, physical alteration, chemical pollution, climate change, etc.). The ranking was determined by taking into account the coverage area of biogeographical provinces, number of citations testing a pressure and number of citations with significant correlation with pressure. We analysed 363 references, of which 169 showed quantitative data. Over a potential total score of 100, the highest values were obtained by the following indices: (i) AZTI's Marine Biotic Index (AMBI), which scored 77, tested by using 14 pressures in 14 provinces from the Arctic to tropical seas; (ii) multivariate AMBI (M-AMBI), which scored 74, tested with 12 pressures in 13 provinces; (iii) Bentix (BENTIX), which scored 68, tested with nine pressures in six provinces; (iv) Benthic Quality Index (BQI), which scored 66, tested with five pressures in seven provinces; and (v) Benthic Opportunistic Polychaetes Amphipods (BOPA) index, which scored 62, tested with eight pressures in six provinces.

A biological condition gradient model for historical assessment of estuarine habitat structure

Coastal ecosystems are affected by ever-increasing natural and human pressures. Because the physical, chemical, and biological characteristics unique to estuarine ecosystems control the ways that biological resources respond to ecosystem stressors, we present a flexible and adaptable biological assessment method for estuaries. The biological condition gradient (BCG) is a scientific framework of biological response to increasing anthropogenic stress that is comprehensive and ecosystem based and evaluates environmental conditions and the status of ecosystem services in order to identify, communicate, and prioritize management action. Using existing data, we constructed the first estuarine BCG framework that examines changes in habitat structure through time. Working in a New England (U.S.) estuary with a long history of human influence, we developed an approach to define a reference level, which we described as a "minimally disturbed" range of conditions for the ecosystem, anchored by observations before 1850 AD. Like many estuaries in the U.S., the relative importance of environmental stressors changed over time, but even qualitative descriptions of the biological indicators' status provided useful information for defining condition levels. This BCG demonstrated that stressors rarely acted alone and that declines in one biological indicator influenced the declines of others. By documenting the biological responses to cumulative stressors, the BCG inherently suggests an ecosystem-based approach to management. Additionally, the BCG process initiates thinking over long time scales and can be used to inspire scientists, managers, and the public toward environmental action.

Developing a wintering waterfowl community baseline for environmental monitoring of Narragansett Bay, Rhode Island

In 2004, the Atlantic Ecology Division of the US Environmental Protection Agency’s Office of Research and Development began an annual winter waterfowl survey of Rhode Island’s Narragansett Bay. Herein, we explore the survey data gathered from 2004 to 2011 in order to establish a benchmark understanding of our waterfowl communities and to establish a statistical framework for future environmental monitoring. The abundance and diversity of wintering waterfowl were relatively stable during the initial years of this survey, except in 2010 when there was a large spike in abundance and a reciprocal fall in diversity. There was no significant change in ranked abundance of most waterfowl species, with only Bufflehead ( Bucephala albeola) and Hooded Merganser ( Lophodytes cucllatus) showing a slight yet significant upward trend during the course of our survey period. Nonmetric multidimensional scaling (NMDS) was used to examine the community structure of wintering waterfowl. The results of the NMDS indicate that there is a spatial structure to the waterfowl communities of Narragansett Bay and this structure has remained relatively stable since the survey began. Our NMDS analysis helps to solidify what is known anecdotally about the bay’s waterfowl ecology, and provides a formalized benchmark for long-term monitoring of Narragansett Bay’s waterfowl communities. Birds, including waterfowl, are preferred bioindicators and we propose using our multivariate approach to monitor the future health of the bay. While this research focuses on a specific area of New England, these methods can be easily applied to novel areas of concern and provide a straightforward nonparametric approach to community-level monitoring. The methods provide a statistic test to examine potential drivers of community turnover and well-suited visualization tools.

Biomarker responses to sewage pollution in freshwater mussels (Diplodon chilensis) transplanted to a Patagonian river

Field and laboratory experiments were combined to evaluate biomarker responses of Diplodon chilensis to sewage pollution. Mussels from an unpolluted area in Lacar lake (S0) were caged at a reference site (S1) and at two sites with increasing sewage pollution (S2, S3) in Pocahullo river (all in Argentina). After 1 month, gill (g) glutathione S-transferase (GST) and catalase (CAT) activities, and lipid peroxidation (TBARS) were found to be significantly elevated in S3, gGST being positively correlated with fecal bacteria (FC) concentration. Digestive gland (dg) enzyme activities were depressed and dgTBARS were increased in all transplanted mussels. After 3 mo, most variables returned to control levels in S1 mussels except for dgCAT and dgTBARS. After seven months, GST and CAT activities of S0 and S3 mussels were evaluated in the laboratory, before and after acute exposure (8 h) to high fecal bacteria concentration ([FC] in S3x 2). gGST increased in both groups, while dgGST responded only in S3 mussels. gCAT and dgCAT activities were similarly increased by acute exposure in both groups. Our results suggest that gGST and gCAT are suitable biomarkers for high FC pollution regardless of previous exposure history. In addition, we show that dgCAT is sensitive to the acute increase in FC load, both in naive and long-term exposed individuals, while dgGST becomes responsive after long-term acclimatization.

A review of strategies to monitor water and sediment quality for a sustainability assessment of marine environment

The basic aim of this work is (1) to review and present practically operational requirements for a sustainability assessment of marine environment, such as describing the monitoring process, research approaches, objectives, guidelines, and indicators and (2) to illustrate how physico-chemical and biological indicators can be practically applied, to assess water and sediment quality in marine and coastal environment. These indicators should meet defined criteria for practical usefulness, e.g. they should be simple to understand and apply to managers and scientists with different educational backgrounds. This review aimed to encapsulate that variability, recognizing that meaningful guidance should be flexible enough to accommodate the widely differing characteristics of marine ecosystems.

Multivariate methods and artificial neural networks in the assessment of the response of infaunal assemblages to sediment metal contamination and organic enrichment

A 4-year annual sediment survey was conducted in an organically enriched tidal channel to compare the performance of univariate community descriptors, traditional multivariate techniques (TM) and artificial neural networks (AANs), in the assessment of infaunal responses to moderate levels of sediment metal contamination. Both TM approaches and the SOM ANN revealed spatiotemporal patterns of environmental and biological variables, suggesting a causal relationship between them and further highlighting subsets of taxa and sediment variables as potential main drivers of those patterns. Namely, high values of non-natural metals and organic content prompted high abundances of opportunists, while high values of natural metals yielded typical tolerant assemblages of organically enriched areas. The two approaches yielded identical final results but ANNs showed the following advantages over TM: ability to generalise results, powerful visualization tools and the ability to account simultaneously for sediment and faunal variables in the same analysis. Therefore, the SOM ANN, combined with the K-means clustering algorithm, is suggested as a promising tool for the assessment of the ecological quality of estuarine infaunal communities, although further work is needed to ensure the accuracy of the method.

Relationships between watershed emergy flow and coastal New England salt marsh structure, function, and condition

This study evaluated the link between watershed activities and salt marsh structure, function, and condition using spatial emergy flow density (areal empower density) in the watershed and field data from 10 tidal salt marshes in Narragansett Bay, RI, USA. The field-collected data were obtained during several years of vegetation, invertebrate, soil, and water quality sampling. The use of emergy as an accounting mechanism allowed disparate factors (e.g., the amount of building construction and the consumption of electricity) to be combined into a single landscape index while retaining a uniform quantitative definition of the intensity of landscape development. It expanded upon typical land use percentage studies by weighting each category for the intensity of development. At the RI salt marsh sites, an impact index (watershed emergy flow normalized for marsh area) showed significant correlations with mudflat infauna species richness, mussel density, plant species richness, the extent and density of dominant plant species, and denitrification potential within the high salt marsh. Over the 4-year period examined, a loading index (watershed emergy flow normalized for watershed area) showed significant correlations with nitrite and nitrate concentrations, as well as with the nitrogen to phosphorus ratios in stream discharge into the marshes. Both the emergy impact and loading indices were significantly correlated with a salt marsh condition index derived from intensive field-based assessments. Comparison of the emergy indices to calculated nitrogen loading estimates for each watershed also produced significant positive correlations. These results suggest that watershed emergy flow is a robust index of human disturbance and a potential tool for rapid assessment of coastal wetland condition.

Recolonisation of translocated metal-contaminated sediments by estuarine macrobenthic assemblages

A recolonisation experiment was performed using sediments from three locations (Nords Wharf, Cockle Bay and Warners Bay) along a metal contamination gradient (Lake Macquarie, Australia). The study aimed to determine whether the source of the sediments would influence the recolonisation of benthic assemblages, providing additional information regarding the ecological risks associated with the more contaminated sediments. Sediments were translocated to two locations within the lake and retrieved after 22 weeks along with benthic samples from the surrounding sediments (ambient). Total abundance was greater in the reference treatment (Nords Wharf), with this difference being driven by polychaetes, especially capitellids. In general, univariate metrics were similar among the recolonised treatments, although evenness and diversity patterns were complex due to significant location-treatment interactions. PERMANOVA analysis demonstrated that the Nords Wharf treatments were significantly different from the more contaminated treatments (Cockle Bay and Warner's Bay) and the ambient assemblages, with no differences being detected among Cockle Bay and Warners Bay assemblages. Collectively, the findings showed that the source of the sediments influenced the composition of the recolonised assemblages, with the described approach being a powerful tool for examining the effects of location-specific sediments under environmentally relevant conditions.

Can sediment total organic carbon and grain size be used to diagnose organic enrichment in estuaries?

Eutrophication (i.e., nutrient enrichment, organic enrichment, and oxygen depletion) is one of the most common sources of impairment in Clean Water Act 303(d)-listed waters in the United States. Although eutrophication can eventually cause adverse effects to the benthos, it may be difficult to diagnose. Sediment organic carbon (OC) content has been used as an indicator of enrichment in sediments, but the amount of surface area available for carbon adsorption must be considered. We investigated the utility of the relationship between OC and sediment grain size as an indicator of eutrophication. Data from the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program was used to test this relationship. However, anthropogenic contaminants are also capable of causing adverse effects to the benthos and often co-occur with elevated levels of OC. Contaminant analysis and toxicity tests were not consistently related to enrichment status as defined by relationship between total OC and grain size. Although variability in response occurred, reflecting the variance in the water column factors (dissolved oxygen, chlorophyll a, and nutrients) and limited sample sizes, the data supported the hypothesis that sites designated as enriched were eutrophied. Dissolved oxygen levels were reduced at enriched sites, whereas chlorophyll a and nutrients were higher at enriched sites. This suggests that the relationship of OC to grain size can be used as a screening tool to diagnose eutrophication.

An overview of marine biodiversity in United States waters

Marine biodiversity of the United States (U.S.) is extensively documented, but data assembled by the United States National Committee for the Census of Marine Life demonstrate that even the most complete taxonomic inventories are based on records scattered in space and time. The best-known taxa are those of commercial importance. Body size is directly correlated with knowledge of a species, and knowledge also diminishes with distance from shore and depth. Measures of biodiversity other than species diversity, such as ecosystem and genetic diversity, are poorly documented. Threats to marine biodiversity in the U.S. are the same as those for most of the world: overexploitation of living resources; reduced water quality; coastal development; shipping; invasive species; rising temperature and concentrations of carbon dioxide in the surface ocean, and other changes that may be consequences of global change, including shifting currents; increased number and size of hypoxic or anoxic areas; and increased number and duration of harmful algal blooms. More information must be obtained through field and laboratory research and monitoring that involve innovative sampling techniques (such as genetics and acoustics), but data that already exist must be made accessible. And all data must have a temporal component so trends can be identified. As data are compiled, techniques must be developed to make certain that scales are compatible, to combine and reconcile data collected for various purposes with disparate gear, and to automate taxonomic changes. Information on biotic and abiotic elements of the environment must be interactively linked. Impediments to assembling existing data and collecting new data on marine biodiversity include logistical problems as well as shortages in finances and taxonomic expertise.