Dynamics of the Acartia genus (Calanoida: Copepoda) in a temperate shallow estuary (the Mondego estuary) on the western coast of Portugal

Abstract

        The purpose of this work was to review the dynamics of the Acartia species in the Mondegoestuary (a temperate North-Atlantic shallow estuary in Western Portugal) in a genus integratedperspective. The Acartia genus is represented in the system by the species Acartia clausi andAcartia tonsa; the samples were taken between July 1999 and June 2000, with 63 and 125 µmmesh size nets, and between January 2003 and January 2004, with a 335 µm mesh size net, in thedownstream and upstream areas of the estuary. Significant differences in abundance were foundbetween months and sampling stations for the two species (ANOVA, P≤0.05). A. clausi dominatedin the downstream estuary, registering peaks in June (156 ind. m^-3) and September (73 ind. m^-3); inthe upstream estuary this species showed a maximum of density in September (35 ind. m^-3.A. tonsadominated in the upstream estuary with peaks of abundance occurring in December (2372 ind. m^-3)and October (1056 ind. m^-3) in the downstream estuary this species exhibited higher abundancein August (52 ind. m^-3). The two species of the genus coexist in time exhibiting a strong spatialsegregation behavior in the estuary.