Physiological energetics of the zebra musselDreissena polymorpha in lakes II. Food uptake and gross growth efficiency |
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Authors: | Martin Sprung |
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Institution: | (1) Zoological Institute, University of Cologne, Germany;(2) Present address: UCTRA, Universidade do Algarve, Campus de Gambelas, P-8000 Faro, Portugal |
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Abstract: | Food uptake ofDreissena polymorpha from two shallow water sites and one site at a 9 m depth in lakes was monitored over the course of 1 1/2 years. Feeding was
characterized by the filtration capacity and ingestion capacity (i.e. the unrestricted maximum rates) at ambient temperature. The available food was estimated as seston dry weight, as seston
ash free dry weight and as seston volume (sum of the volumes of the particles in the water column).
The filtration capacity and ingestion capacity varied strongly during the course of the year by more than 1:10, with maximum
values during late spring and early summer. The filtration capacity was correlated with water temperature, the ingestion capacity
with temperature and seston concentration. However, at identical water temperatures both capacities were higher in spring
than in autumn. At the 9 m site, filtration and ingestion capacity was also significantly influenced by lack of oxygen caused
by stratification during summer.
In the allometric equations by which both capacities (C) were related to body weightW (C=a W
b
), an exponent b of 0.89±0.14 (mean±95% confidence interval) was calculated for the filtration capacity and 1.00±0.18 for
the ingestion capacity. Both exponents did not vary significantly during the course of the year. The seasonal trend of the
incipient limiting concentration (i.e. the seston concentration at which the intestine is filled to its capacity when the animal filters at maximum rate) was less
pronounced. It showed a significantly positive correlation with seston concentration and a negative correlation with temperature.
Except during the spring bloom, the incipient limiting concentration was in the range of the seston volume registered at the
sites. Gross growth efficiencies were highly variable. An annual average between 5 and 20% was calculated. Growth efficiencies
were lower at the shallow water sites with the highest seston concentrations. |
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Keywords: | Dreissena polymorpha filtration rate ingestion rate growth efficiency body size |
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