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Seagrasses are gaining attention thanks to their metabolism and potential major role as carbon sinks, with further implications as nature-based solutions against climate change. Despite their recognized importance and the growing number of studies published, there is still a striking paucity of information on seagrass metabolism and contribution to biogeochemical cycles for some seagrass species and ocean areas. In this study we assessed the metabolic balance and nutrient cycling contribution of seagrasses to the benthic compartment of a tropical reef lagoon in Reunion Island, providing original information on a barely studied seagrass species (Syringodium isoetifolium) and a poorly studied ocean region (West Indian Ocean). We measured the net productivity, respiration and the metabolic balance in different components of the lagoon benthic compartment (i.e. seagrass, sediment, and benthic community) and the water-sediment nutrient benthic fluxes at differently impacted sites within the lagoon. The biogeochemical environmental variability, including inorganic and organic indicators of anthropogenic contamination, was also assessed at each site.Large spatial variability was detected in the metabolic balance of each benthic component assessed, also associated with the natural and/or anthropic-driven environmental variability found in the lagoon. The seagrass S. isoetifolium was net autotrophic across the lagoon and contributed to the lagoon benthic metabolism with net plant productivity exceeding by one order of magnitude the plant respiration. The lowest seagrass metabolism was detected at the impacted site. The metabolic balance of the sediment was heterotrophic but the high productivity of S. isoetifolium contributed to reducing the heterotrophy of the whole benthic community. The lagoon-wide benthic metabolic balance was slightly heterotrophic, but the associated uncertainty ranged from autotrophy to heterotrophy. Nutrient concentrations in the lagoon were low and the benthic community capacity for nutrient retention (uptake) and removal (denitrification and anammox) indicated potential for buffering moderate nutrient inputs into the lagoon. Organic contaminants of emerging concern (CECs) were low but detectable in the lagoon, especially in highly frequented beach areas, arising as an environmental quality indicator of interest.

Anthropogenic wastes from different origns (urban, agricultural or industrial activities) have brought severe consequences to the environmental quality of freshwater ecosystems. The impact to aquatic biota linked to contamination has been mainly assessed in function of the toxic (either lethal or sublethal) effects produced on organisms. The ability of organisms to avoid exposure to contaminants, which helps organisms to prevent toxicity, began to be also considered as evidence of environmental risk. The risk associated to the contamination-driven organisms’ spatial displacement can be a serious problem to habitat selection, migration, and (re)colonization processes as well as to the community structure even if no toxic effect at individual level occurs. Theriver inputs of contamination can occur in different zones over its course showing a patchy scenario or a contamination gradient. As organisms exposed to these contamination scenarios can move from contaminated to more favorable habitats, avoiding the contact with the toxic compounds, we have hypothesized that an avoidable discharge can act as chemical barrier causing a habitat fragmentation and affecting the organisms’ displacement (from down to upstream and vice versa). Therefore, the present study aims (i) to verify if the contamination originated from urban and agricultural discharges in a river (i.e. Guadalete River; Southwest Spain) could generate a chemical barrier that restricts the displacement of one of their representative organisms (i.e. the shrimp Atyaephyra desmarestii,and (ii) to discriminate the preference/avoidance response of this species on the effects of the contaminants in water and sediment compartments. Habitat selection assays were performed in a free-choice, multi-compartmented, non-forced exposure system, simulating the spatial arrangement of the samples such as their distribution in the environment, and the freshwater shrimp A.desmarestii, species frequently found in European Rivers (including in the Guadalete River), was used astest organism. Water and sediment samples were collected along Guadalete River, including pristine and sewage-impacted areas (e.g., near the local wastewater treatment plant). Contamination was assessed by measuring a wide range of commonly reported metals and organic contaminants (hydrocarbons, pesticides, pharmceuticals, personal care products, etc.). Results clearly showed that shrimps selected the less contaminated water and sediment samples, indicating that their spatial distribution might be driven by contamination levels. In addition, evidence of habitat fragmentation due to contamination of sediment was observed in the sampling area close to the wasterwater treatment plant. The preference behavior towards some river samples was highly related to contamination levels of water and sediment. Results indicate that contamination might act as chemical barrier causing a spatial isolation of populations., C.V.M. Araújo is grateful to the Spanish Ministry of Economy and Competitiveness for a Juan de la Cierva contract (IJCI-2014-19318). This studywas partially funded by NET SCARCE project (Red Consolider sobre los efectos de la escasez de agua y el cambio global en sistemas fluviales -CTM2015-69780-REDC).

Trabajo presentado en la SETAC Europe 27th Annual Meeting (Environmental Quality Through Transdisciplinary Collaboration), celebrada en Bruselas del 7 al 11 de mayo de 2017., In recent years, the use of personal care products (PCPs) has increased notably. This increase together with growing of human population in coastal areas has provoked a constant entrance of emerging pollutants into the aquatic environments. However, data about bioaccumulation and toxicity of PCPs in aquatic biota are scarce. In this research, the clam Ruditapes philippinarum has been considered as model organism. The aim of this work was to investigate the role of TiO2 nanoparticles in bioaccumulation of organic PCPs and the toxic responses of single and mixture exposure experiments using a battery of antioxidant enzymes (superoxide Oxidase, catalase, total gluthathione peroxidase, Se-dependent glutathione peroxidase and glutathione reductase ) , lipid peroxidation and DNA damage. In the experiment, four treatments, controls and ethanol controls were run in parallel. Two of the four treatments were single treatments, one of the treatment was 100 ppb of TiO2 in form of nanoparticles < 100 nm (TiO2 NPs) and the other one TiO2 in bulk form. The other two treatments were mixture treatment: a) 100 ppb of TiO2 NPs plus 10 ppb of a mix of organic PCPs and b) 100 ppb of TiO2 bulk plus 10 ppb of mix of organic PCPs. The organic PCPs selected were triclosan (antimicrobial), OTNE (fragrance) and benzophenone-3 and octocrylene (UV filters).. Bioaccumulation of inorganic compound such as TiO2 was almost immediate reaching steady stationary over exposure time; and depuration rate was low. Respect to organic compounds in mixtures, triclosan and benzophenone-3 accumulations were mediated by TiO2 and was driven by the size of the particles. TiO2 NPs seems to play a key role in the uptake of organic compounds (“a Trojan horse”), probably due to their high surface area, large pore volume and the presence of high affinity surface hydroxyl groups 1, plus their capacity to stabilize the occurrence of these organic compounds in the cell tissues. NPs provide potential route for the delivery of nanoparticle-associated toxic pollutants to sites where they would not normally reach them. Many NPs, including TiO2 NPs, have shown a tendency to adsorb other pollutants by binding transitional metal and organic pollutants; in addition they have showed the ability to internalize them into the body and cells. The joint action of the organic compound mix and any of the two forms of TiO2 provoked significant (p< 0.01) changes in the activity of antioxidant enzymes compared (EROD, SOD, CAT, T-GPx, Se-GPx, GST and GR). Despite of higher bioaccumulation of triclosan and benzophenone-3 in the TiO2 NPs mixture than TiO2 bulk mixture treatments, toxicity observed could be consequence of compound interactions instead of total bioaccumulation processes., This research has been funded by Junta de Andalucía (PE2011-RNM-7812 project).

The spatial distributions and fates of selected legacy and emerging compounds were investigated and compared in surface sediments sampled along the Adriatic mud-wedge and in deep-sea regions from the southern Adriatic basin. Results indicated that the concentrations of legacy contaminants (PAHs, PCBs and DDTs) and emerging contaminants (tonalide, galaxolide, EHMC, octocrylene, BP3 and NP) ranged from 0.1 to 572 ng g(-1) and from