The Crustacean Zooplankton (Copepoda, Branchiopoda), Atyid Decapoda, and Syncarida of the Nile Basin

Abstract

The about 17 spp. of calanoid copepods of the Nile basin are dominated by East African species, but in the lower Nile, several Mediterranean species are found. Some species are endemic to the basin and Lake Chad. Endemic species also occur in some of the East African plateau lakes. Two ecological groups are present: species typical of permanent, and species typical of ephemeral waters. Among Cyclopoida, the dominant genera are Mesocyclops and Thermocyclops, together about 20 species with African, Afro-Asian, and (few) with Mediterranean affinities. An invasive cyclopoid, Acanthocyclops trajani, has become dominant in the eutrophic delta lakes. Among anomopods, about ten species of Daphnia with different ecological and geographic ranges have been found. Some 75 species of cladocerans are now on record, a number that is expected to increase in future years. Anostracans are rep- resented by about six species of Streptocephalus, some of which are Mediterranean, other East African, and at least one restricted to the Ethiopian plateau. Syncarida (Bathynellacea) have been little studied, with three African species on record. Among decapods, Caridina nilotica occurs basin-wide and is partly planktonic, partly benthic. By analogy with Lake Chad and Lake George, zooplankton production is estimated at roughly 40 t per km2 for the East African plateau lakes. Production further north, in Lake Nasser and the Delta lakes, with a yearly biomass variation of a factor 3 (Nasser) to 10 (delta), and concomitant variations in water temperature, may not be fully compensated by higher biomasses and may be lower.