Microzooplankton were sampled at four stations in the open waters of the northern Adriatic sea during 38 cruises from 1990 to 1993. Samples were collected at 1, 10, 20 m and near the bottom, using a 5 l Niskin bottle. Copepod nauplii densities were significantly higher than densities of all other microzooplankton groups, even ciliates. The maximum values were noted in August, what correspond to a high number of adult Oithona nana, the dominant copepod species in the northern Adriatic sea. Due to naupliar size differences, sampled community was divided in five categories: NSI (<90um), NSII (90-102 um), NSIII (120-160um), NSIV (160-210um)and NSV (>210um). PC analysis was used to extract the main patterns of changes in temperature, salinity, chlorophyll a concetration, nanophytoplankton and microphytoplankton cell numbers and their relation to each naupliar category. The annual temperature variability was not related to nanophytoplankton cell numbers and was negatively corellated with microphytoplankton. Temperature was the major source of naupliar temporal and spatial variability, it was positively correlated with the NSI and negatively with the NSV. Chlorophylla concentrations and nanophytoplankton cell number correlated with abundances of larger nauplii (>NSIII). These results confirm importance of cell smaller than 20 um as a food to early naupliar development stages. Naupliar abundance accorded with a maximum number of anchovy larvae and postlarvae in the notrhern Adriatic. Different size categories of nauplii seem to be adequate diet of anchovy during transitional phase between passive and active feeding.

Biologija