Abstract
Long-term variations of ecological status in a Mediterranean coastal lagoon (Sacca di Goro, Northern Adriatic) were investigated, combining data on the concentration of surface sediment contaminants and on the structure of the macrobenthic community. The aim was to assess any amount of chemical contamination and check the response of the macrobenthic community to sediment contamination. Over the studied period, the sediments of the lagoon showed contamination by trace metals and organochlorine pesticides, with most of them exceeding the thresholds indicated by the Italian legislation in many samples. Contamination by polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) instead never exceeded the threshold. The ecological status based on the macrobenthic community, evaluated through biotic indices (AMBI and M-AMBI), fell below the Good/Moderate threshold in most samples. The results indicate a possible influence of toxic compounds in sediment on benthic organisms, but most of the variability shown by the macrobenthic community is probably due to other factors. The difficulty in establishing a cause/effect relationship was due to the co-occurrence and variability of various stressors (both natural and anthropogenic) and their interactions. The methods currently used for monitoring transitional waters thus seem insufficient to disentangle the effect of pollutants and other environmental variables on the benthos. Integrated approaches (e.g., bioaccumulation and toxicity tests) are thus needed for a more precise identification of the risk posed by a high concentration of pollutants in such environments.
Highlights
Contaminated sediments are a priority issue in aquatic systems impacted by anthropogenic use, industry, and urban development
Particle size distribution was determined samples were analyzed for grain sizeorganic and organic
Not significant differences were observed among years in the percentage of Organic matter (OM), sand, silt, and clay in the sediment (Friedman test, p < 0.05) (Figure 2)
Summary
Contaminated sediments are a priority issue in aquatic systems impacted by anthropogenic use, industry, and urban development. Sediments act as a "sink" for contaminants, making the analytical determination of their concentrations easier with respect to the water column and providing time-integrated information about the ecosystem health. The evaluation of temporal changes in sediment contamination is crucial to answer questions about the state of the system, whether it is improving in time or to determine if remediation activities have benefited the system [1]. Water 2020, 12, 1074 effect of contaminants on the biota are often a snapshot in time, with very few samples in a short study period. In such studies, the influence of temporal variation cannot be evaluated. The knowledge on temporal variation in contaminant availability is desirable, as recommended by the Water Framework
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