Similarity of micro-zooplankton and relations with environmental variables in a subtropical estuary

Abstract

The spatial and seasonal variations of the micro-zooplankton abundance in a subtropical estuary were studied during a year. Five sampling sites were monthly sampled in Guaratuba Bay, Paraná State, from September 2004 to July 2005. The microzooplankton was sampled in the water subsurface with suction pump and filtered in 64

μm plankton net. The environmental variables was gotten with a multiparameter Horiba U10 (salinity, dissolved oxygen, temperature and pH), and Secchi disk (transparency). The cluster similarity analysis grouped zooplankton in freshwater, summer meroplanktonic organisms and holoplanktonic contend different ontogenetic stages. The distinct groups among stations sampling occurred for the high proximity of the tributaries discharges or in function of the linking of the estuary with the ocean. Between the months, the seasons had been separate. The canonical correlation analysis (81% of explanation) complemented the results of the analysis of grouping, separating seasonally and spatially the main groups and its abundance. The results suggest clear space

and seasonal variations for the micro-zooplankton in the Guaratuba Bay, with peaks of abundance in the summer due to meroplankton contribution associated to the highest water temperatures. Copepoda had dominated numerically under other groups, mainly the immature forms, sufficiently showed in reason of the small opening mesh of the employed net.