Zooplankton of Lake Kivu, East Africa, half a century after the Tanganyika sardine introduction

TY - JOUR

T1 - Zooplankton of Lake Kivu, East Africa, half a century after the Tanganyika sardine introduction

AU - Isumbisho, M.

AU - Kaningini, B.

AU - Sarmento, H.

AU - Micha, J.-C.

AU - Descy, J.-P.

N1 - Copyright 2008 Elsevier B.V., All rights reserved.

PY - 2006/11/1

Y1 - 2006/11/1

N2 - The introduction into Lake Kivu of the planktivorous fish Limnothrissa miodon at the end of the 1950s raised major concern about the fate of mesozooplankton, but few data were available to assess the impact of predation. In this study, we followed zooplankton variations in Lake Kivu for 3.5 years. Present Lake Kivu mesozooplankton is dominated by cyclopoid copepods (Thermocyclops consimilis, Mesocyclops aequatorialis and Tropocyclops confinis), but cladocerans and rotifers are also present. Each year, total crustacean abundance in the plankton increased to a distinct seasonal maximum following a rise of phytoplankton production associated with a deep epilimnetic mixing in the dry season (August-September). This dependence on phytoplankton resource suggests that mesozooplankton dynamics in Lake Kivu is mainly bottom-up controlled, contrary to expectations from the food web structure. However, measurements of body size indicate that sardine predation affects the cladoceran Diaphanosoma excisum, whereas the larger copepods may efficiently escape predation by migration in the deep mixolimnion at daytime. Total biomass of mesozooplankton in Lake Kivu is lower than in lakes Tanganyika and Malawi. This may be related to the disappearance of a large grazer that existed before the sardine introduction, whereas the large lakes of the same region have a more complex pelagic food web, with piscivorous fish, and with calanoid copepods, which can more efficiently exploit phytoplankton production.

AB - The introduction into Lake Kivu of the planktivorous fish Limnothrissa miodon at the end of the 1950s raised major concern about the fate of mesozooplankton, but few data were available to assess the impact of predation. In this study, we followed zooplankton variations in Lake Kivu for 3.5 years. Present Lake Kivu mesozooplankton is dominated by cyclopoid copepods (Thermocyclops consimilis, Mesocyclops aequatorialis and Tropocyclops confinis), but cladocerans and rotifers are also present. Each year, total crustacean abundance in the plankton increased to a distinct seasonal maximum following a rise of phytoplankton production associated with a deep epilimnetic mixing in the dry season (August-September). This dependence on phytoplankton resource suggests that mesozooplankton dynamics in Lake Kivu is mainly bottom-up controlled, contrary to expectations from the food web structure. However, measurements of body size indicate that sardine predation affects the cladoceran Diaphanosoma excisum, whereas the larger copepods may efficiently escape predation by migration in the deep mixolimnion at daytime. Total biomass of mesozooplankton in Lake Kivu is lower than in lakes Tanganyika and Malawi. This may be related to the disappearance of a large grazer that existed before the sardine introduction, whereas the large lakes of the same region have a more complex pelagic food web, with piscivorous fish, and with calanoid copepods, which can more efficiently exploit phytoplankton production.

UR - http://www.scopus.com/inward/record.url?scp=33750460573&partnerID=8YFLogxK

U2 - 10.1093/plankt/fbl032

DO - 10.1093/plankt/fbl032

M3 - Article

AN - SCOPUS:33750460573

VL - 28

SP - 971

EP - 989

JO - Journal of Plankton Research

JF - Journal of Plankton Research

SN - 0142-7873

IS - 11

ER -