Abstract
We investigated the impact of fish farming on the benthic biota of 2 habitats (sea- grass meadows of Posidonia oceanica and non-vegetated soft bottoms), by examining in detail the nematode assemblages, and the effects of organic enrichment on their abundance, diversity (spe- cies richness and trophic diversity), community structure and individual size. All investigated faunal variables differed significantly between impact and control sediments, except for indi - vidual nematode biomass. Nematodes displayed reduced biodiversity beneath the investigated fish farms in both vegetated and non-vegetated habitats. The nematode genera Richtersia, Desmoscolex and Halalaimus were highly sensitive to biodeposition and disappeared almost com- pletely in farm sediments, whereas other genera such as Daptonema and Prochromadorella largely increased their relative abundance. The impact of biodeposition was investigated also in terms of K-dominance curves and functional variables (life strategies as maturity index, and func- tional (i.e. trophic) diversity) which showed that nematodes are very sensitive to this kind of envi- ronmental disturbance. Our results indicate that the analysis of nematode assemblage composi- tion, the life traits of the dominant species and the presence/disappearance of certain nematode species represent a reliable tool for monitoring the quality state of marine sediments exposed to fish-farm organic wastes.
Highlights
Mediterranean aquaculture production has increased by 77% over the last decade, especially in coastal systems (Rosa et al 2012)
We investigated the impact of fish farming on the benthic biota of 2 habitats, by examining in detail the nematode assemblages, and the effects of organic enrichment on their abundance, diversity, community structure and individual size
Our results indicate that the analysis of nematode assemblage composition, the life traits of the dominant species and the presence/disappearance of certain nematode species represent a reliable tool for monitoring the quality state of marine sediments exposed to fish-farm organic wastes
Summary
Mediterranean aquaculture production has increased by 77% over the last decade, especially in coastal systems (Rosa et al 2012). Previous investigations revealed that benthic assemblages can respond to fish-farm activities in terms of: (1) a decrease in abundance, biomass and species richness (Klaoudatos et al 2006, Tomassetti et al 2009), due to a selection of a few opportunistic species (Weston 1990); (2) a shift in the relative importance of the different trophic guilds (Pearson & Rosenberg 1978); (3) changes in the size of benthic organisms (Tsujino 1998); and (4) a shift in life strategies, with increasing relevance of opportunistic species (Bongers et al 1991, Mirto et al 2002) Meiofauna, due to their important role in marine benthic food webs (Moens et al 2005) and their bioecological traits (small size, high abundance, fast generation times and absence of larval dispersion), are a useful tool to investigate alterations in the sea bottom. This study completes a previous investigation carried out to ascertain the effects of fish-farm wastes on abundance, biomass and community structure of meiofaunal assemblages (Mirto et al 2010)
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