Effects of pollution on marine gastrotricha in the northwestern Adriatic Sea

The barrier islands and coast south and east of Venice, Italy, were sampled in parallel to the work of Schrom two decades ago. Where he found 49 site records for 24 species of gastrotrichs at 8 sites, 5 littoral and 3 shallow sublittoral, we found 5 site records for 2 species at 9 sites, 5 littoral and 4 shallow sublittoral. We had no site records from littoral sites; one species, Dolichodasys elongatus, occurred at all sublittoral sites. From other locations (n=15) in our present survey of the Italian coastline, where we have paired littoral: sublittoral sites, we have found 6.7 (±0.9) species in the former and 8.0 (±0.9) in the latter. The absence of gastrotrichs in samples from all five littoral sites and the dominance of D. elongatus in sublittoral sites is clear evidence as to the severity of pollution in this area. However, five species were found in a sample from the top of a longshore bar at one location, indicating that a type of local refugium exists from which future recolonization of the remaining habitat could proceed, if the input of pollutants can be reversed.