engleski

Long term changes in North Adriatic soft-bottom polychaete assemblages following a dystrophic crisis

In the Northern Adriatic Sea the combination of natural and anthropogenic processes causes periodical hypoxia and anoxia, which can determine mass mortality of benthic organisms. Here we report the results of a 20-year monitoring program carried out after an anoxic event in 1989 that caused benthic mass mortality over an area of about 1.200 km2. The recovery dynamics of the polychaete fauna was followed at 3 stations (including one sampled 1 year before the anoxic event). Samples (0.1 m2 Van Veen grab, 2 mm sieve) were collected from 1989 to 1994 and from 2003 to 2008. A total of 6519 specimens belonging to 186 species were identified. The analyses of univariate biodiversity indexes highlighted higher temporal variation of assemblage diversity in the period following the dystrophic crisis, followed by higher stability in the next decade. PERMANOVA suggested that the highest component of assemblage variation belonged to the factor year. Differences across years however varied in magnitude, depending on stations and were portrayed by nMDS plots of year’s centroids for each of the three stations. SIMPER analysis identified the species most characterising the assemblages in each year for each of the three stations. Our results highlight the importance of analysing long-term dataset in order to understand assemblage dynamics following strong events of disturbance. Assuming the 1989 anoxia as the event determining the biodiversity change, and considering our outcomes, which suggest that the assemblages still shows a pattern of non-random changes trough years, our data indicate that the polychaete fauna is still recovering without having reached a pattern of among-years stability. Focusing on the biology of the species characterising the different periods might help in understanding the ecological processes that have determined the observed pattern.

long-term biomonitoring; Northern Adriatic; soft bottoms; Polychaeta; anoxia; taxonomy

Rad je prezentiran na skupu 10th International Polychaete Conference, održanom od 20.-26.06.2010., Lecce, Italija.