Can the leaf-bag technique detect benthic macrofauna responses to sediment contamination by metals and metalloids in estuaries?

Biodiversity mediates the effects of stressors but not nutrients on litter decomposition

Understanding the consequences of ongoing biodiversity changes for ecosystems is a pressing challenge. Controlled biodiversity-ecosystem function experiments with random biodiversity loss scenarios have demonstrated that more diverse communities usually provide higher levels of ecosystem functioning. However, it is not clear if these results predict the ecosystem consequences of environmental changes that cause non-random alterations in biodiversity and community composition. We synthesized 69 independent studies reporting 660 observations of the impacts of two pervasive drivers of global change (chemical stressors and nutrient enrichment) on animal and microbial decomposer diversity and litter decomposition. Using meta-analysis and structural equation modeling, we show that declines in decomposer diversity and abundance explain reduced litter decomposition in response to stressors but not to nutrients. While chemical stressors generally reduced biodiversity and ecosystem functioning, detrimental effects of nutrients occurred only at high levels of nutrient inputs. Thus, more intense environmental change does not always result in stronger responses, illustrating the complexity of ecosystem consequences of biodiversity change. Overall, these findings provide strong evidence that the consequences of observed biodiversity change for ecosystems depend on the kind of environmental change, and are especially significant when human activities decrease biodiversity.

Spatial distribution of organic and inorganic contaminants in Ria de Aveiro Lagoon: A fundamental baseline dataset

This paper presents baseline data of sediments characterization from Ria de Aveiro lagoon (Portugal). Twenty-two intertidal surface sediments were collected and analysed for their pseudo-total content of 25 major and trace elements and for their total content of PAHs (Sum16) and PCBs (Sum13). The fine fraction percentage and total organic carbon content were also determined. Ria de Aveiro Lagoon has been the target of several studies during the last decades, and it has been pointed out as a hot spot in terms of contamination García-Seoane et al., 2016. Nevertheless, data about sediments contamination is mostly focused on Hg Lillebø et al.,2011, and in a specific area of the lagoon Grilo et al., 2013, and there is not a clear and global picture about the spatial distribution of other elements, and especially of organic contaminants. Thus, this baseline dataset is of utmost importance for researchers and planners and it can be used to monitor the effect of disturbances, such as: dredging activities; hydrodynamic changes (either due to human activities or extreme events); external inputs (new discharges from industries and wastewater plants, etc).

Comparison of benthic indices for the evaluation of ecological status of three Slovenian transitional water bodies (northern Adriatic)

Benthic indicators are important tools for the classification of coastal and transitional water bodies. The aim of the work was to assess for the first time the Environmental Status (ES) of Slovenian transitional waters, comparing the following biotic indices: richness, Shannon-Weaver diversity, AMBI, M-AMBI, BENTIX and BITS indices. A total of 13 stations were sampled with a Van Veen grab, in three ecosystems in the northern Adriatic. Samples were sieved and sorted, invertebrates identified and counted. The anthropogenic impact was estimated with professional judgement. Richness and diversity showed a good response to anthropogenic pressure. Conversely, indices based on sensitivity/tolerance groups did not showed a clear distinction between more and less impacted ecosystems. In particular BENTIX underestimated the ES, while with BITS there was a overestimation. The best evaluation was obtained with M-AMBI, because even if based on a sensitivity/tolerance approach, it considered also the structural aspect of the community.