Sediment characteristics and macrofauna distribution along a human-modified inlet in the Gulf of Oristano (Sardinia, Italy)
Como, S.; Magni, P.; Casu, D.; Floris, A.; Giordani, G.; Natale, S.; Fenzi, G.A.; Signa, G.; De Falco, G. (2007). Sediment characteristics and macrofauna distribution along a human-modified inlet in the Gulf of Oristano (Sardinia, Italy). Mar. Pollut. Bull. 54(6): 733-744. http://dx.doi.org/10.1016/j.marpolbul.2007.01.007
In: Marine Pollution Bulletin. Macmillan: London. ISSN 0025-326X; e-ISSN 1879-3363, more
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| Keywords |
Aquatic communities > Benthos
Chemical compounds > Sulphur compounds > Sulphides
Organic matter > Carbon > Organic carbon > Total organic carbon
Species diversity
Water bodies > Lagoons > Coastal lagoons
Marine/Coastal |
| Author keywords |
macrofauna; total organic carbon (TOC); benthic species richness;acid-volatile sulphides (AVS); artificial structures; Coastal lagoons |
| Authors | | Top |
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- Floris, A.
- Giordani, G.
- Natale, S.
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- Fenzi, G.A.
- Signa, G.
- De Falco, G.
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| Abstract |
We studied the spatial variability and within-year temporal changes in hydrological features, grain size composition and chemical characteristics of sediments, as well as macrofaunal assemblages, along a heavily modified inlet in the Gulf of Oristano (western Sardinia, Italy). The inlet connects the Cabras lagoon to the gulf through a series of convoluted creeks and man-made structures, including a dam and fish barriers built in the last three decades. Sediments were muddy and mainly composed of the “non-sortable” fraction (i.e., <8 μm particle size) in all four areas investigated: Lagoon, Creeks, Channel and Seaward. Along the inlet, however, the ratio between the <8 μm and the 8-64 μm fractions was highest in Creeks and Channel, between the fish barriers and the dam, suggesting impaired hydrodynamics. Consistently, steep gradients in water salinity, temperature and dissolved oxygen concentrations were found in proximity to the fish barriers. The whole inlet was characterized by a major organic enrichment of sediments, with up to an annual mean of 33.6% of organic matter and 11.7% of total organic carbon in Seaward due to the presence of seagrass leaf litter. Acid-volatile sulphide and chromium-reduced sulphur concentrations were highest throughout the year in Seaward and Lagoon, respectively, with a peak in summer. Consistently, the whole inlet supported low structured macrofaunal assemblages dominated by few opportunist species, with a relatively lower diversity in Lagoon throughout the year and the highest abundances in Seaward in summer. We infer that the presence of artificial structures along the inlet, such as fish barriers and the dam, impair the lagoon-gulf hydrodynamics, sediment exchange and animal recruitment and colonization. We suggest that the removal of these structures would favour water renewal in the Cabras lagoon, but would also increase the outflow of organic C-bonding fine particles into the gulf with serious consequences for Posidonia oceanica and Cymodocea nodosa seagrass meadows. We conclude that all possible consequences of such initiatives should be carefully considered before any action is taken. |
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