|Direct and indirect effects of zooplankton on seston stoichiometry|
Urabe, J. (1995). Direct and indirect effects of zooplankton on seston stoichiometry. Ecoscience 2(3): 286-296
In: Ecoscience. Université Laval: Sainte-Foy, Québec. ISSN 1195-6860, more
Controlled conditions; Grazing; Nutrients (mineral); Ponds; Secondary production; Seston; Zooplankton; Japan, Honshu, Chiba Prefect.; Fresh water
In the present study, the effect of zooplankton on the stoichiometry of seston was examined in a small eutrophic pond from April to August, because the relative elemental contents of seston relates with phytoplankton growth rate and food quality. In the pond, most of the sestonic particles were edible size (<30 mu m), and sestonic C:P and N:P ratios were high at low zooplankton biomass but low at high zooplankton biomass, suggesting that the zooplankton activity is one of the important factors inducing changes in seston stoichiometry. This possibility was substantiated by grazer gradient experiments that showed a significant increase in the relative P content of the seston with increasing zooplankton biomass. The response of sestonic elemental ratios to simulated grazing revealed that the zooplankton can affect seston stoichiometry by increasing the per capita availability of a deficient nutrient for phytoplankton through grazing as well as nutrient release. These results suggest that the effect of zooplankton on seston particles is feedback to their growth rate by changing not only food abundance but also food quality.