Filtration rates of the invasive pest bivalve Limnoperna fortunei as a function of size and temperature

SYLVBESTER FRANCISCO; DORADO JIMENA; BOLTOVSKOY DEMETRIO; JUAREZ ANGELA; CATALDO DANIEL

Ennis, Irlanda

Conferencia; 13th International Conference on Aquatic Invasive Species; 2004

Institute of Technology, Sligo, Ballinode, Sligo, Ireland

FILTRATION RATES OF THE INVASIVE PEST BIVALVE Limnoperna fortunei AS A FUNCTION OF SIZE AND TEMPERATURE Sylvester, F.1,2, Dorado, J., Boltovskoy, D. 1,2, 3, Juárez A. 1 and Cataldo, D. 1,2,3 1 Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina; 2  Consejo Nacional de Investigaciones Científicas y Técnicas; 3 Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”. ABSTRACT Limnoperna fortunei (Dunker, 1857) is a freshwater bivalve mollusc native to the rivers of Southeast Asia that appeared in Hong Kong in 1965, between 1980 and 1986 in Japan, Taiwan and Korea, and in Argentina in 1990. Most of these invasions are thought to have occurred via ships ballast water. Presently the geographic range of this species in South America covers the entire Paraná-Uruguay-Río de la Plata watershed, including Argentina, Uruguay, Paraguay, Bolivia and Brazil, extending over 3000 km upstream from its original place of entry – the Río de la Plata estuary. Shortly after arrival, Limnoperna’s bysally attached populations reach densities in excess of 150,000 ind. m-2 clogging pipes, filters, heat exchangers, condensers etc. in industrial and power plants that use raw water, chiefly for cooling purposes. In addition, similarities between the zebra mussel and L. fortunei suggest that the latter may have an even stronger environmental impact than Dreissena. It is anticipated that Limnoperna’s filtering activity affects strongly trophic interactions and the availability of food for both pelagic and benthic species, and the rates of other ecosystem processes including mineralization of nutrients, oxygen availability and sedimentation rates, yet research in this direction has so far been practically absent. In order to contribute to the assessment of these impacts, laboratory filtration experiences were performed using monocultures of the alga Chlorella vulgaris. Experimental conditions included two mollusc sizes (15 and 23 mm), and three water temperatures (15, 20 and 25ºC) covering the normal thermic seasonal range in the lower Paraná river and Río de la Plata. Filtration rates obtained were, for the larger mussels: 9.9, 13.1 and 17.7 ml∙mg tissue dry weight -1∙h-1 at 15, 20 and 25ºC, respectively, and for the smaller ones: 17.7, 20.8 and 29.5 ml∙mg-1∙h-1. Differences between sizes and between temperatures (except for those between 15 and 20°C) were statistically significant. These results indicate that although in absolute terms larger animals have higher clearance rates, as a function of body mass smaller individuals feed more actively. Within the range of experimental values used, filtration rates were positive associated with water temperature. These clearance rates (125-350 ml∙individual‑1∙h‑1) are generally higher that those reported for other suspension feeding bivalves, including the invasive species Dreissena polymorpha, D. bugensis and Corbicula fluminea. These high filtering rates, associated with very high densities (up to over 150,000 ind.∙m‑2) sugest that the environmental impact of this mussel may be swiftly changing ecological conditions in the areas colonized. Keywords: Limnoperna fortunei, bivalves, molluscs, filtration, grazing, ecosystem impact.