INTERANNUAL VARIABILITY OF ZOOPLANKTON IN THE RÍA DE VIGO, NORTHEAST ATLANTIC.

Abstract

From 1997 to 2005, a mesozooplankton monthly study was carried out in a station located in the Ría de Vigo (42º 13, 3´ N, 8º 47, 7´ W) at a depth of 29 m. Its biomass was estimated and a range of 0.23-208.47 mg dry weight free of ash per m3 was found. Total abundance was counted and interannual range was between 252 and 52 474 ind. per m3. Zooplankton abundance showed an increasing trend during the last years. In the community structure it was observed that the dominant zooplanktonic group was copepods, with an interannual range of 45.4-56.0 % and 1 591-8 499 ind. per m3. For the rest of holoplankton, predominant groups were appendicularia (7 -14%) and cladocera (2 - 15%). In meroplankton the cirripedia nauplii and echinodermata larvae are dominant. The first do not reach 15% and record abundances minor than 9 000 ind. per m3, and the latter do not exceed 6% and a maximun of 22 433 ind. per m3 in the year 2003. Presence of species from warm waters must be highlighted, such as the copepods Temora stylifera and Oncaea mediterranea, with respective maximum values of 840 and 141 ind. per m3 as well as the cladocera Penilia avirostris, showing an occasional important presence in october 1997, reaching a 11.2 % and abundance of 81 ind. per m3 .

Key words: zooplankton, biomass, relative abundance, absolute abundance, Ría de Vigo. NE Atlantic.