Macrobenthos response to sewage pollution in a tropical inshore area

Moving beyond traditional macrofaunal community structure studies in the Indian Ocean continental shelf: a research synthesis based on research weaving

The Indian Ocean (IO) continental shelf characterized by unique oceanographic and meteorological features and extreme habitat is a biodiversity hotspot region. Marine biodiversity provides valuable resources and services, in terms of economy, cultural, science, and education. Unsustainable exploitation and habitat degradation represent the greatest threat to biodiversity. Understanding how these services will change in the future requires knowledge of marine biodiversity. Although macrofaunal biodiversity is critical for the functioning of shelf systems, it has received much less attention, particularly in the IO, mainly due to logistics reasons precluding our ability to predict future changes. Here, we discuss the state of knowledge of macrofaunal ecology, to identify the knowledge gaps, which will allow for setting research priorities. The new framework in research synthesis, research weaving, that combines systematic mapping with bibliometric analysis was applied. The research weaving approach helps illustrate the evolution of research over time and identifies areas of current research interests and the performance of institutions and collaboration patterns. Data retrieved from the Web of Science were analyzed in the R and VOS Viewer software. The results highlight how macrofaunal research in IO is constrained by spatial and temporal scales, with the majority of studies focused on structural patterns. Moreover, most studies were conducted in a few countries (India, Australia, Saudi Arabia, Iran, and South Africa) using different sampling techniques hindering comparison within the IO habitats. Future studies investigating the macrofaunal community using a multidisciplinary approach and scientific collaboration (regional and international) can advance our efforts to close the marine biodiversity knowledge gaps.

Tracing the impact and recovery trajectory of oil spill affected tropical rocky intertidal macrobenthic communities using the BOPA index

A yearlong study was conducted to assess the impact of an oil spill on macrobenthos of rocky intertidal zone of Uran, India and its recovery processes, by comparing impacted site with a reference. Immediate acute effects observed were elevated sediment hydrocarbons, absence of macroalgae and amphipods, mass mortality of macrofauna and dominance of the opportunistic nereid, Namalycastis senegalensis. As the hydrocarbons reduced at the impacted site by ~50 % within three months, gradual re-appearance of macroalgae and re-colonization of amphipods (51.4 %) and sensitive polychaetes (7 %) indicated that the recovery was well underway. The amphipod, Allomelita pellucida proved to be a potential indicator of oil contamination. BOPA correlated with sediment hydrocarbons and performed effectively as the extant macrobenthic communities had sufficient representation of Polychaeta and Amphipoda. Notwithstanding the distinct initial impacts of the oil spill, comparable macrobenthic assemblages comprised of sensitive species at both sites after a year confirmed complete recovery.

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.

Assessment of ecological health of Swarnamukhi river estuary, southeast coast of India, through AMBI indices and multivariate tools

A combination of biotic indices, geo-accumulation (I_geo) index, and a multivariate approach were applied to assess the anthropogenic influence on the benthic community at five stations from 2018 to 2019 in the Swarnamukhi river estuary, Nellore, India. Non-metric multidimensional scaling and cluster analysis indicated that the Buckingham canal (BC) station showed azoic conditions and formed a separate cluster. Strong positive factor loadings of Cd (0.96), Al (0.93), Zn (0.91), Fe (0.90), Co (0.89), Cu (0.89), Ni (0.87), Pb (0.85), Cr (0.77), organic matter (0.94), Silt (0.92), and clay (0.93) and negative loading of sand (-0.90) showed the variability in sediment. AMBI results illustrated the disturbance status of each station and classified BC station as 'extremely disturbed' class, and M-AMBI assessed the ecological status as 'bad'. The I_geo index also revealed metal (Cd) contamination. The present study illustrated that the combined approach is effective for ecological assessment of coastal ecosystem.

Spatio-temporal variability in macrobenthic communities and trophic structure of a tropical estuary and its adjacent coastal waters

Spatio-temporal distribution of the macrobenthic community (> 500 μm) and the trophic ecology of polychaetes were studied for a year in the Cochin estuary (CE) and its adjacent coastal waters. A profound influence of the southwest monsoon (SWM) was evident in the CE, a tropical monsoonal estuary, during the present study. The sediment texture and macrobenthic density exhibited a pronounced spatial variation in the estuary, while in the coastal waters temporal changes were more prominent. Polychaetes formed the dominant taxa in terms of density and diversity in the estuary (53 species belonging to 25 families) as well as in the adjacent coastal waters (39 species belonging to 20 families). The polychaete species Diopatra neapolitana dominated during nonmonsoonal periods was found to be replaced by the higher abundance of Pisione sp. in the CE during the monsoon period. On the other hand, in the coastal waters, Cossura coasta, the dominant species during the pre-monsoon period, was replaced by the surface deposit feeder Paraprionospio pinnata during the monsoon and post-monsoon periods. The study evidenced the combined influence of sediment texture, salinity, and food availability in determining the distribution and abundance of the macrobenthic fauna in the CE and adjacent coastal waters. Feeding guild analysis and trophic importance index showed that carnivores and surface and subsurface deposit feeders were the dominant and trophically important feeding guilds in the study area. Redundancy analysis showed that the sandy substratum supported a diversified functional composition in the estuary and its adjacent coastal waters, and motile, discretely motile polychaetes and filter feeders were more associated with the sandy substratum. Results of the present study revealed that the seasonally fluctuating polychaete community structure in the study area was predominantly controlled by their diversified feeding habits and the ecological descriptors of the polychaete feeding guilds were linked primarily to the substratum type and food availability.

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.

Occurrence of tumors among gastropods Plicopurpura pansa (Gastropoda: Neogastropoda) in the Port of Manzanillo, Mexico

In order to evaluate the health of Plicopurpura pansa, a species considered vulnerable, a population of this gastropod living in proximity to the port of greatest cargo movement in Mexico was monitored seasonally during 1 year. Morphometric characteristics and sexual proportion were recorded. A macroscopic analysis was carried out to detect malformations and imposex; a histological analysis was performed to evaluate disseminated and gonadal neoplasias; the presence/absence in soft tissues of butyltin species (BTs) as possible contamination agents was also estimated. A total of 508 P. pansa specimens were collected. The largest specimens were obtained in winter. The coefficients of determination inside the port were low (R² = 0.453). In general, there was a greater proportion of females than males throughout the year. Distinctive foot malformations (tumors) were recorded, but without signs of imposex. The histological examination confirmed the presence of disseminated neoplasias in the foot and gonads of P. pansa in the Port of Manzanillo. The comparative analysis of the morphological and histological features of the studied gastropod population allowed us to recognize impact patterns in relation to proximity to the port. There were high concentrations of monobutyltin (MBT) and greater abundance of tumors in heavier specimens; this was associated with port proximity zones. P. pansa could therefore serve as a sensitive bioindicator of environmental health in marine systems.

Permutation Tests of Hierarchical Cluster Analyses of Carrion Communities and Their Potential Use in Forensic Entomology

Forensic entomologists can use carrion communities' ecological succession data to estimate the postmortem interval (PMI). Permutation tests of hierarchical cluster analyses of these data provide a conceptual method to estimate part of the PMI, the post-colonization interval (post-CI). This multivariate approach produces a baseline of statistically distinct clusters that reflect changes in the carrion community composition during the decomposition process. Carrion community samples of unknown post-CIs are compared with these baseline clusters to estimate the post-CI. In this short communication, I use data from previously published studies to demonstrate the conceptual feasibility of this multivariate approach. Analyses of these data produce series of significantly distinct clusters, which represent carrion communities during 1- to 20-day periods of the decomposition process. For 33 carrion community samples, collected over an 11-day period, this approach correctly estimated the post-CI within an average range of 3.1 days.

Testing the efficiency of temperate benthic biotic indices in assessing the ecological status of a tropical ecosystem

The objectives of the present study were to evaluate the ecological status of tropical coastal waters using the temperate benthic indices and examine the effect of seasonal variability on the performance of benthic indices. Macrobenthic samples were collected from northwest to southeast coast of India during 2003-2012 and we tested different univariate indices, ecological strategies, indicator species and multimetric indices. AMBI and multimetric indices performed satisfactorily in evaluating the ecological status. Seasonal variability on the biotic indices was observed during the southwest monsoon and fall intermonsoon period due to recruitment. Therefore, we recommended the non-monsoon period (January-May) as a suitable time of the year to use the indices for effective assessment of the Indian coastal waters. Results show that, the temperate benthic indices are efficient in assessing the tropical environmental status. However, complementary use of different indices is suggested for accurate assessment of the environmental status.

Potential ecological risk of heavy metal contamination in sediments and macrobenthos in coastal wetlands induced by freshwater releases: A case study in the Yellow River Delta, China

We investigated the nine heavy metal contents in the sediments and macrobenthos of the Yellow River Delta Wetlands using three experimental areas that received freshwater releases and one reference area that did not. Heavy metal contents, the single-factor contamination index (SFCI), the metal contamination index (MCI), and the biota-sediment accumulation factor (BSAF) were used to evaluate the potential ecological risk and bioaccumulation. We found that As exceeded the national standard value by more than 50%, and that the ranges of SFCI for each metal were generally larger in autumn than in spring. MCI showed no clear pattern, but the BSAF results suggest that Cd bioaccumulates from sediments to macrobenthos. Pollution-resistant species such as Corophium sinense, Chironomus sp., and Einfeldia sp. became dominant in the areas receiving freshwater releases, and provide direct evidence of ecological risk in the wetlands. Our results provide preliminary information to guide managers for ecological risk assessments.

Monitoring the effects of wastewater treatment strategies

Wastewater disposal in coastal waters causes widespread environmental problems. Secondary treatment is expected to reduce the adverse effects of insufficiently treated wastewater. The environmental impact of sewage disposal via 18 wastewater treatment plants was analysed using the benthic opportunistic polychaetes and amphipods (BOPA) index. In previous studies this index proved to be an effective tool for monitoring sewage pollution. The impact of these discharges was highly related to treatment level, which ranged from pre-treatment to biological, as well as to flow rates and outfall position. Locations affected by pre-treated wastewater showed environmental degradation, especially marked near outfalls with higher flow rates. At most locations, biologically treated wastewater did not cause a significant impact and an improvement in ecological integrity was detected after this secondary treatment had been implemented. The impact of discharge was highly related to chemical oxygen demand (COD), suspended solids and nutrient concentrations, which are all lower in biologically treated wastewater. A 'moderate' ecological status was observed not only near sewage outfalls with high wastewater flow rates (>1,500,000 m(3)/month) with a COD over 200 mg/l but also near those with lower flow rates but with a COD over 400 mg/l. To reduce the impact of sewage disposal, it is necessary to carry out adequate treatment, have site outfalls deep enough, and implement water recycling.