Macrobenthic community responses to multiple environmental stressors in a subtropical estuary

Abstract

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.

Chromium adsorption studies using brewer’s spent grain biochar: kinetics, isotherm and thermodynamics

“…The positive enthalpy is considered for endothermic reactions. The slightly positive value obtained in this study (3.07 kJ.mol -1 ) suggested a physisorption reaction (SOUZA et al, 2021). The change in the entropy (∆S) indicated the randomness of the reaction at the solid/liquid interface.…”

“…The adjustments of the Freundlich model provided a value of R 2 (0.79 to 0.88) and ∆q (5.65 to 9.15%) lower than the comparison with the Langmuir model (Table 6). The empiric Freundlich model does not represent the maximum adsorption capacity and does not present the equilibrium plateau, not fitting well the final experimental points of the equilibrium curve (SOUZA et al, 2021). The Temkin model showed R 2 values from 0.87 to 0.99 and ∆q from 2.12 to 6.78 (Table 6).…”

“…Cr is widely used in chemical industry for various applications such as pigments, metal plating, metallurgy, and in chemical production. Cr was detected up to 95.8 mg kg -1 of sediment samples in an estuarine region -----------------------------------------------------------------------Langmuir---------------------------------------------------------------------- ---------------------------------------------------------------------Freundlich------------------------------------------------------------------------- ------------------------------------------------------------------Redlich-Peterson----------------------------------------------------------------- of the Baía de Babitonga, located in northeast of Santa Catarina, where metallurgical and textile industries are concentrated (SOUZA et al, 2021).…”

Using the Heavy Metal and Biotic Indices to Assess Ecological Quality in the Central Area of the East Sea, South Korea

“…In this study, the observed positive correlation between H' and heavy metals was perplexing, as it is generally expected that higher concentrations of metals typically reduce macrobenthic community diversity [69]. Moreover, the mechanisms by which metal contaminants harm organisms often differ from those associated with organic pollution [70]. The effects of metal-induced mechanisms on organisms are usually only observable in the broader biological strata of populations or communities in subsequent generations or subpopulations of the affected species after extended periods of exposure [71].…”