Food web organization of Posidonia oceanica invertebrate community in fragmented and no-fragmented sites

Posidonia oceanica meadows play a fundamental role on biodiversity organization. Despite the causes are complex and still discussed, P. oceanica meadows are experiencing a fragmentation process, particularly on coastal areas. In this study we addressed the effect of meadow fragmentation on detritus associated macroinvertebrates abundance and diversity and on the structure of detritus based food webs by comparing a no-fragmented portion of the meadow with a fragmented one in the coastal area of Tarquina (Vt), Italy (42°12’40’’N 11°41’55’’E). Macroinvertebrate samples were collected using 20g autochthonous P. oceanica litterbags, the sampling design included six replicates litterbags placed in sampling sites in no-fragmented and fragmented areas of the meadow. To test the importance of autochthonous detritus quality in defining habitat complexity and carrying capacity, also six 20g Phragmites australis leaf litterbags were placed in each site. Detritus based food webs parameters were determined by correlative analysis of macroinvertebrate census data, corrected by 13C and 15N values. The results presented are from a pioneering approach to study invertebrate food web in P. oceanica meadow. The results emphasize the effect of fragmentation on community composition and biodiversity organization (food web).