Environmental regulation of the estuarine copepods Acartia tonsa and Eurytemora americana during coexistence period.

HOFFMEYER, M. S; BERASATEGUI, A.A.; BEIGT, D.; PICCOLO, M.C.

JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM

Cambridge University Press

Lugar: United Kingdom; Año: 2009 vol. 89 p. 355 - 361

0025-3154

The seasonal dynamics of Acartia tonsa and the invader Eurytemora americana were analysed in relation to the environmental variability occurring from April to November in the Bahia Blanca Estuary. Twice a month, the abundance of eggs, nauplii, copepodites and adults was examined and some environmental variables were recorded. Multivariate statistics (CCA) was applied to analyse the data ofvariables. Acartia tonsa eggs and nauplii diminished from April-May and they were almost absent between June and September, although a small larval peak could be detected from the end of July to October. A11 the stages of this species increased in number through spring. Eurytemora americana was registered as from June and only nauplii larvae were observed, with a peak increase during September. Copepodites and adults were observed asfrom July, increasing in number until peaking at the end of September. The number of all stages of this species decreased abruptly, the whole population disappearing from the plankton. The A. tonsa developmental stages were most positively correlated with temperature, photoperiod and other light variables whereas those ofE. americana showedpositive correlations with chlorophyll-a and salinity. Thegradients of the main environmental factors likely give rise to a certain niche separation facilitating the coexistence of the two copepod populations within the period studied.