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Phosphorus‐limited Daphnia: Intraspecific facilitation instead of competition
Author(s) -
Sommer Ulrich
Publication year - 1992
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1992.37.5.0966
Subject(s) - daphnia , biology , intraspecific competition , daphnia galeata , cladocera , algae , competition (biology) , population , scenedesmus , chemostat , botany , ecology , zooplankton , branchiopoda , demography , genetics , sociology , bacteria
P‐limited chemostat cultures of the green alga Scenedesmus acutus were inoculated with the herbivorous zooplankter Daphnia galeata after steady state had been reached. At low dilution rates (up to 0.5 d −1 ) and consequently low P content of the food algae (P : C < 0.0011) Daphnia could not grow. At higher dilution rates (from 0.55 d −1 upward) and higher P content of the food, Daphnia developed dense populations which were able to reduce algal biomass more than 10‐fold. This reduction was accompanied by an increase in the P content of the algae which gave rise to increased birth rates of Daphnia. The birth rates of P‐limited Daphnia depended on algal cell quotas in a saturating fashion which was mathematically similar to Droop’s growth equation. During P limitation the birth rates of Daphnia were positively correlated to population density, which suggests intraspecific facilitation instead of competition.