Ecological studies on the planktonic copepoda of the Brisbane River estuary with special reference to Gladioferens pectinatus (Brady) (Calanoida)

Abstract

The seasonal salinity and temperature characteristics of the Brisbane River estuary are discussed, and, in addition, the changes in relative ionic proportions that occur in passing from the gradient to the freshwater zone.

Preliminary consideration is given to the taxonomy of three species of Pseudodiaptomus that occurred in the estuary. The spatial and temporal distribution of the following copepods is discussed in relation to salinity and temperature: Oithona sp. ; Acartia sp. ; Pseudodiaptomus, 3 spp. ; Labidocera sp. ; Isias uncipes; Gladioferens pectinatus; Sulcanus conflictus. The most striking features of the distribution of Gladioferens pectinatus were its continuous presence at the freshwater end of the gradient zone, and its downstream extension into water of high salinity during the colder months. Spatial and seasonal variation in egg number within the Gladioferens population was studied. In this population the relative proportion of immature copepodid stages decreased with increasing depth. There was evidence that portion of the mature female component of the Gladioferens population underwent diurnal vertical migration. The occurrence of Isias uncipes was restricted to winter and early spring when population densities were at a maximum immediately adjacent to the bottom and rapidly decreased to zero at higher levels. Evidence is presented that the range of salinity tolerance of Sulcanus is less than that of Gladioferens.

Results obtained are compared with those of similar studies elsewhere. Possible relationships between congeneric occurrence, sex ratio, and relative abundance are discussed.