ИСТИНА

Seasonal changes of quantities of all meiobenthos groups are well known for temperate and polar re-gions. However, seasonality in abundances is typical for tropical intertidal also. Seasonal studies were undertaken on the White Sea intertidal zone and in mangrove intertidal in Red River delta (Vietnam). Prominent seasonal variations were found in every meiofaunal taxa in both regions. Samples in Red river delta were taken in three localities on muddy intertidal with Kandelia candel (L.) vegetation. One sample series were collected inside mangrove bush, the second on the border of mangroves and the third on the open tide flat. On the White Sea two transects across intertidal zone were collected seasonally on high energy beach composed by coarse to medium sand and in the sheltered muddy intertidal. In all sites and seasons nematodes are the most abundant group followed by harpacticoid copepods. Other meiobenthic groups including annelids, tardigrades, ostracods, gastrotrihs etc were much less abundant. Significant seasonal changes occur in every taxon in all sites of both regions. On the White Sea intertidal minimal values occur in mid-winter (January) and metazoan abundance increases already in early spring (April) despite of ice coverage on the intertidal. On the Red River stations maximal metazoan abundance was record in spring (April), lowest values registered in January in mangrove sites and in November on the open flat. Seasonal trends of nematodes and harpacticoid copepods were different. Maximal nematodes density appears in Spring and Summer while harpacticoids were more numerous in Winter time (at least at two stations form three). By magnitude temporal variability on the White Sea stations approaches two orders for nematodes and one for harpacticoids. In Red river sites nematodes max to min ratio was up to six, for harpacticoids it approaches two orders of magnitude. Meta-analysis of literature data exhibits high seasonal variability both in tropical and polar tidal zones. Seasonal changes occur in most of investigated areas at all latitudinal zones. Factors which are responsible for seasonal changes in meiobenthic associa-tions are discussed.