Vertical distribution of Eurytemora americana (Crustacea, Copepoda) during a tidal cycle in the Bahía Blanca estuary

MENÉNDEZ MARÍA CLARA; HOFFMEYER MÓNICA SUSANA; PICCOLO MARÍA CINTIA; FERNÁNDEZ SEVERINI MELISA DAIANA

Buenos Aires

Jornada; VIII Jornadas Multidisciplinarias de la Sociedad Argentina de Biologia.; 2006

Sociedad Argentina de Biología

Vertical distribution of zooplankton is a complex phenomenon involving differents behaviors that change according to species and individual. This distribution depend on factors such as age, sex and spawning and external factors such as tidal cycles, lunar phase, light intensity, temperature and salinity. This study analyze the influence of tide and physical and chemical variables on vertical distribution of developmental satages of E. americana. Sampling was conducted at Cuatreros Port in August 2005. samples were taken every three hours at surface and bottom over a 14-hour period. Submersibles pumps discharging into 200 µm mesh nets were used. Salinity, temperature, chlorophyll a, particulate organic matter and suspended sediment were measured at each time. Temperature range was 9.8-11.6 ºC and salinity 29.3-33.2. Chlorophyll a was higher at surface whereas the highest concentration of suspended sediment was registered during flood at bottom. Copepodids I-III dominated at surface during all tidal cycle and the highest value was observed during ebb. A similar pattern ocurred at bottom, although during flood copepodids IV-V were more abundant and the differences in abundance were not as marked as in surface. Adults males and females showed a similar pattern along the tidal cycle (surface and bottom) but males were always more abundant than females. Nauplius, copepodids I-III and IV-V were, in general, more abundant at surface while males and females at bottom. Differences in the abundances would indicate that the stages are distributed differentially in the water column and that the tide influences their position in the water column.