Comparative analysis of sedimentary metal phases and their respective roles in shaping living benthic foraminiferal communities: Implications for environmental biomonitoring

This work examines the effects of the potentially toxic element (PTEs) concentrations through total sediment digestion (TD) and sequential chemical extraction in three sedimentary phases (i.e., water, organic matter, and manganese hydroxides) on living benthic foraminifera in the Guanabara Bay (GB), one of the largest transitional ecosystems in Rio de Janeiro State (SE Brazil). It also considers the variations in the quantity and quality of organic matter, hydrodynamics and physicochemical parameters as stressors parameters for these organisms. The statistical analysis provides compelling evidence that measuring PTEs._TD through the total digestion of sediments is not the most effective method for assessing the impact of pollution on living meiofaunal organisms like benthic foraminifera. Conversely, it documents that benthic foraminifera respond to gradients of available (or soft-bound) PTE concentrations in the sediment, quantity and quality of organic matter, the level of environmental confinement, and changes in physicochemical variables. Therefore, this work supports the importance of analyzing available and/or softbound metal fractions for disentangling the response of living organisms to environmental impact. The present findings have significant implications for environmental biomonitoring studies and the development of ecological indices based on foraminifera.