Colonization pattern and population density of the Asian invasive mussel Limnoperna fortunei in a reservoir in central Argentina

BOLTOVSKOY DEMETRIO; KARATAYEV ALEXANDER; BURLAKOVA LYUBOV; CATALDO DANIEL; KARATAYEV VADIM; SYLVESTER FRANCISCO; MARIÑELARENA ALEJANDRO

Montreal, Quebec, Canada

Congreso; ICAIS 2009 (16th International Conference on Aquatic Invasive Species); 2009

ICAIS 2009 (16th International Conference on Aquatic Invasive Species)

Colonization Pattern and Population Density of Invasive Bivalve Limnoperna fortunei in a Reservoir in Central Argentina Demetrio Boltovskoy and Daniel Cataldo University of Buenos Aires, School of Exact and Natural Sciences, Department of Ecology, Genetics and Evolution C1428EHA Buenos Aires, Argentina Alexander Y. Karatayev and Lyubov E. Burlakova Buffalo State College, Great Lakes Center 1300 Elmwood Avenue, Buffalo, NY 14222, USA Vadim A. Karatayev City Honors School 186 East North Street, Buffalo, NY 14204, USA Francisco Sylvester University of Windsor, Great Lakes Institute for Environmental Research 401 Sunset Avenue, Windsor, ON, N9B 3P4 Canada The freshwater bivalve Limnoperna fortunei, native to Southeast Asia, was introduced into Argentina around 1990, swiftly spreading throughout the entire Río de la Plata-Paraná watershed and becoming the dominant macrobenthic organism on hard substrates. At present, the mussel is a major nuisance for industrial and power plants that use raw river or lake water for their processes, and several important effects on the biota have been described (enhancement of nutrient cycling, plankton gazing and invertebrate densities, modification of trophic interactions, etc.). Mussel densities in excess of 200,000 ind. m2 have been mentioned, but abundances over large areas have not been estimated. In December 2006 we performed a detailed study of the densities of L. fortunei in Embalse de Río Tercero, a medium-sized (54 km2) reservoir in central Argentina where the mussel was first discovered in 1998. Abundances were assessed on the basis of 109 diver-collected 0.25 m2 samples distributed among 25 transects. Mussel beds were clearly associated with the type of substrate. At the sampling time, most (85%) of the mussels were adult individuals (>13 mm in total length). Mean densities on bedrock and boulders (4867 ind. m-2) were over one order of magnitude higher than those on silt (339 ind. m-2), where it only occurred on isolated hard objects, such as wood debris. Other bottom types (gravel, sand) hosted intermediate values. Conversely, variability was highest on silt, gradually decreasing on harder and coarser substrates. Most substrate-associated population density differences were statistically significant. The reservoir hosts somewhat over 3x1010 mussels; over 90% of them at depths <10 m; deeper areas were almost invariably covered by a thick layer of silt. Thus, sandy and rocky areas, which represent about 13% of the lake bottom, hosted 58% of the mussels. The mean density for the entire water body was 712 ind. m-2. In terms of biomass, this represents 1262 metric tons of Limnoperna dry tissue, or 20,458 metric tons of whole wet Limnoperna mass (27 g of dry tissue, or 459 g of whole wet Limnoperna mass, per m2).