Meiofauna and macrofauna community structure in relation to sediment composition at the Iberian margin compared to the Goban Spur (NE Atlantic)

Meiofauna and macrofauna communities and several sediment characteristics were compared between a slope situated far from the coast (Goban Spur) and two transects across the Iberian Margin with steep slopes and close to the shore. The northern Galician transect (off La Coruna) was situated in an area subjected to wind-induced upwelling events. The western Galician transect was also subjected to upwelling. was additionally influenced by outflows of water rich in organic matter from the Rias Bajas. This transect also included the Galicia Bank. Macrofauna density decreased exponentially from the shelf edge ( 154 m) to the abyssal plain (495 1 m) and different communities occurred on the shelf, the upper- and lower slope and on the abyssal plain. Apart front two extremely low-density stations on the Iberian Margin, there were no significant differences in the meiofauna between the Goban Spur and the Iberian Margin. Along the La Coruna-transect a station where meiofaunal densities were low occurred at a depth of 1522 m. where the sediment was characterised by having a high median-grain size, ripple structures, a low C-org and total N content. There were relatively high numbers of macrofaunal filter-feeders but low numbers of crustaceans, indicating a high current velocity regime. On top of the Galicia Bank (similar to770 m) the sediment consisted mainly of shells of pelagic foraminifers, and had low contents of C-org and N. The macrofauna was dominated by filter-feeding and carnivorous taxa. At both these stations meiofauna densities were low. Meiofauna densities and community structure differed between the Goban Spur and the Iberian Margin. Meiofauna densities on the Galician shelf were more than double those on the Goban Spur shelf. The two deep stations on the La Coruna transect and the deepest station on the Galicia Bank transect all contained meiofaunal densities that were higher than found at similar depths off the Goban Spur. The meiofaunal densities were inversely correlated with %CaCO3 content and, excluding the shelf stations, were positively correlated with both %C-org and total N at the Iberian Margin. Neither upwelling nor the enriched outflows from the rias affected the macrofauna, but meiofaunal densities were greatly enhanced. (C) 2002 Elsevier Science Ltd. All rights reserved.