Testing a typology system of running waters for conservation planning in Hungary |
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Authors: | Dénes Schmera Bruno Baur |
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Institution: | (1) Great Lakes Center, Buffalo State College, 1300 Elmwood Avenue, Buffalo, NY 14222, USA;(2) The Research Foundation of the State University of New York, Buffalo State College, Office of Sponsored Programs, Buffalo, NY, USA;(3) Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, USA;(4) Department of Biology, Buffalo State College, 1300 Elmwood Avenue, Buffalo, NY 14222, USA |
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Abstract: | The zebra mussel (Dreissena polymorpha) and its congener the quagga mussel (Dreissena rostriformis bugensis) are both invaders in freshwater, but have very different invasion histories, with zebra mussels attaining substantially
faster rates of spread at virtually all spatial scales. However, in waterbodies where they co-occur, D. r. bugensis can displace D. polymorpha. To determine if the mechanisms for this displacement are associated with different survival and growth, we kept mussels in
flow-through tanks for 289 days with two temperature regimes that mimicked the natural surface water (littoral zone) and hypolimnion
conditions of Lake Erie. For the littoral zone regime, we used water directly from the surface of Lake Erie (range 4–25°C,
average 11.9 ± 0.6°C). For the profundal zone treatment, Lake Erie surface water was chilled to about 6°C (range 5–8°C, average
6.2 ± 0.6°C) for the full duration of the experiment. For each of these temperature regimes, we used three replicate tanks
with only zebra mussels present and three replicate tanks with only quagga mussels (150 ind./tank each), and three replicate
tanks with both species (75 ind./tank of each species). Quagga mussels had higher survivorship and grew more than zebra mussels
in all treatments. For both species, the size of the mussel entering the winter was critical for survivorship. Larger mussels
had a higher survival over the winter in all treatments. For both species, there was a survivorship and growth tradeoff. In
the warmer littoral zone treatment both species had higher growth, but lower survival than in the colder profundal zone treatment.
Surprisingly, although quagga mussels outperformed zebra mussels, zebra mussel survivorship was better when they were faced
with competition by quagga mussels than with just intraspecific competition. In addition, quagga mussels suffered size-specific
mortality during the growing season only when facing interspecific competition with zebra mussels. Further experiments are
needed to determine the possible mechanisms for these interspecific effects. |
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