Macrobenthic community responses to multiple environmental stressors in a subtropical estuary

We assessed how multi- and univariate models reflect marine environmental health based on macrobenthic community responses to three environmental stressor categories: hydrodynamics, organic enrichment and metal contamination. We then compared the models with the benthic index AMBI (AZTI Marine Biotic Index). Macrobenthic community and physicochemical variables were sampled at 35 sites along Babitonga Bay, a subtropical estuary in Southern Brazil. Distance-based linear modelling identified depth, grain size and organic matter as well as Cu and Zn as key stressors affecting the macrobenthos. Using canonical analysis of principal coordinates (CAP), we developed three multivariate models based on the variability in community composition, creating stress gradients. The metal gradient showed better correlation with the benthic community. Sediment quality indices (Geoaccumulation Index and Contamination Factor) showed a low to moderate contamination status, with higher concentrations for Cr, Ni and Zn at the inner areas of the bay. According to AMBI, Babitonga Bay has a “good” environmental health status, and the AMBI values show stronger correlations with the hydrodynamic and organic enrichment gradients (r = 0.50 and r = 0.47) rather than the metal gradient (r = 0.29). Lumbrineridae polychaetes (not included in the AMBI list) and Scoloplos sp. were negatively related to the metal contamination gradient and were considered sensitive, while Sigambra sp., Magelona papillicornis, the gastropod Heleobia australis and species of the crustacean order Mysida were positively related to the gradient and considered tolerant to higher concentrations of metals in the sediment. Despite the inconsistency in the ecological classification provided by AMBI and its relationship with the metal gradient, our results suggest that the environmental quality was satisfactory for the studied gradients. The metal gradient showed the weakest correlation to AMBI. In such cases, the ecological classification of taxa by the index should be evaluated under the perspective of the action of inorganic genotoxic contaminants represented by metals.

Differential Response of Macrobenthic Abundance and Community Composition to Mangrove Vegetation

The mass planting of mangroves has been proposed as a mitigation strategy to compensate for mangrove loss. However, the effects of mangrove vegetation on the abundance and community composition of macrobenthos remain controversial. The macrobenthic communities in four intact mangrove forests with different conditions and the adjacent nonvegetated mudflats of two mangrove species with distinct stand structures on the western coast of Taiwan were examined. Some macrobenthic taxa occurred only in the mangroves, suggesting macrobenthic critical habitats. Seasonal shift in community composition was more pronounced in the mudflats than in the mangroves, possibly due to the rich food supply, low temperature, and shelter function provided by mangrove forests. However, crab density was always lower in the mangroves than in the mudflats. There was a negative relationship between the stem density of Kandelia obovata (S., L.) and infaunal density. The pneumatophore density of Avicennia marina (Forsk.) correlated negatively with epifaunal density. Our results show that the response of macrobenthic abundance and community composition to mangrove vegetation was inconsistent. We reason that mangroves are critical habitats for the macrobenthos in the mudflats. However, if mangrove tree density is high, we predict that the macrobenthic density will decrease. This suggests that at some intermediate level of mangrove tree density, where there are enough mangrove trees to harbor a macrobenthic community but not enough trees to significantly reduce this density, mangroves management can be optimally achieved to promote the presence of a diverse and dense macrobenthic community.

Assessment of Anthropogenically Stressed Ecosystem of Port Waters Using Macrobenthic Community-Biotic Indices

Macrobenthic community being used as marine health indictor vis-à-vis to anthropogenic disturbance since their characteristic of life cycle (reproductive mode, sedentary, energy transfer, sensitive-resistance species, indicator organism etc.). Therefore, the present study was chosen in Vizag port waters have been subject to a variety of anthropogenic pressure in the last two decades. The purpose of this study was to assess the ecological status of the port environment through biotic indices like AZTI 's Marine Biotic Index (AMBI) and Multivariate-AMBI Index (M-AMBI) which have been successfully validated geographically and anthropogenically stressed habitats. The result revealed that the inner harbor (IHC, Iron ore Q1 & Iron ore Q7) stations are heavily disturbed while the outer harbor fall between undisturbed and moderately disturbed status. It was observed that the reduced tidal action inside the harbor determines the health status indicating that the Iron ore transporting areas are at high risk with respect to benthic population.

Distribution Pattern of Macrobenthic Organisms In A Tropical Monsoon Influenced Port, New Mangalore, India

Study was carried out to understand the impact of natural and anthropogenic impacts on the macrobenthic organisms at the New Mangalore port, influenced by south-west monsoon located along the south-west coast of India. Soft bottom macrobenthos are the group of highly diverse benthic invertebrates in the coastal regions. The spatio-temporal variation in their abundance and diversity was observed along with the variations in the water column and sediment characteristics. Among the 61 taxa of macrobenthos reported, 41 belonged to the polychaetes. The organic carbon levels of >2% supported higher abundance of deposit feeders. A correlation in the abundance of polychaetes and sediment characteristics along with dissolved oxygen and pore water nutrients was observed. A shift in the community of macrobenthic species in response to environmental parameters was observed with the change in the season. During post-monsoon I, Prionospio sp., was dominant , whereas during pre-monsoon the amphipod, Ampelisca sp. was dominant. The abundance of opportunistic polychaetes, Prionospio sp., Cossura sp., and Tharyx filibranchia varied with the seasons indicating a change in the habitat characteristics during different seasons. The occurrence and dominance of macrobenthic speceis was influenced by the physical processes mainly governed by the exchange of seawater between the port and the Arabian sea. The stations located in the high circulation area showed higher seasonal variation in the macrobenthic community indicating pivotal role of local hydrodynamics on macrobenthic organisms. The occurrence of opportunistic species inside the port demonstrate the role of anthropogenic stress in structuring the macrobenthic community.