Stressors affecting the macrobenthic community in Rapallo Harbour (Ligurian Sea, Italy)

Description

An annual survey was carried out in Rapallo Harbour (Ligurian Sea, NW Mediterranean) to study the main stressors affecting the macrobenthic communities. The harbour was characterised by a relevant organic enrichment (between 51.9 mg g–1 and 109.6 mg g–1), which did not affect the water column oxygenation, and low but detectable heavy-metal contamination (on average Cu=135.0 μg g–1 and V=23.8 μg g–1). The seasonal changes in the heavy metal concentrations suggested a significant increase in tourist activities (i.e. boat movements) during summer and autumn. In the inner, more protected sampling site, the harbour structures and the vessel movements increased both organic enrichment and sediment instability, resulting in macrobenthic communities dominated by indicator species associated with these stressors. In addition, during summer and autumn, despite a relevant chlorophyll-a flux to the sediment, the settling material was dominated by phaeopigments and refractory proteins, which reduced its trophic value for benthic consumers. In the outer part of the harbour the main stressor was a polluted freshwater inflow, as indicated by the dominance of indicator species such as Capitella spp. (on average 79.5%), Neanthes caudata, Malacoceros girardi and Diopatra neapolitana.

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