Population dynamics of Calanopia americana Dahl F., 1894 (Copepoda, Calanoida) in a reef environment in tropical Brazil

The present study aimed to analyze variations in population dynamics of the Copepoda Calanopia americana (C. americana) in a reef area in tropical Brazil. Diurnal and nocturnal samples were collected at a fixed station during ebb tide, over four lunar cycles, and in the dry and rainy seasons. C. americana presence was very frequent (94%) and occurred in nearly all samples. Overall, juveniles presented higher densities than adults, and females were more abundant than males. There was a significant difference (p < 0.001) between the dry and rainy period for density, biomass and production, with the largest average values observed during the dry season (97.2 ± 91.0 ind.m-3 , 157.64 ± 131.80 µg C m-3 and 34.20 ± 30.36 µg C m-3 day-1 , respectively). In relation to the variation between day and night, the population dynamics of C. americana followed a pattern noted in previous studies, showing density peaks at (522,3 ± 402,68 ind.m-3 ) and lower values during the day (324,0 ± 336,36 ind.m-3 ). During the dry season, the amount of available light coupled with a lower amount of suspended material interferes with the community by increasing the density and influencing the productivity of C. americana. Although some studies have shown the influence of the lunar cycle on the migration processes of C. americana, in this study these variation did not have significant influence on population dynamics. Key-words: lunar cycle, plankton, production, biomass