Modelling the geographic expansion of Crassostrea gigas in the marine coast of Argentina

CARRASCO, MAURO F; HARDKE, LEANDRO; WEILER, NILDA E.; BARÓN, PEDRO J.

Mar del Plata

Conferencia; 2ndWorld Conference on Biological Invasions and Ecosystem Functioning; 2011

Grupo de Investigación y Educación en Temas Ambientales

Since its illegal introduction to Argentina for aquaculture in 1982, and after several translocations, the Pacific oyster Crassostrea gigas has occupied the intertidal/shallow subtidal of northern (36.4ºS) and southern Buenos Aires and north of Rio Negro provinces (37º-39ºS), and continues its expansion. Since this ecosystem engineer is causing changes to the coastal geomorphology and producing impacts on traditional economic activities, the objective of our study is to develop a predictive model allowing to establish the most likely patterns of occupation of the intetidal (geographical range; most likely sites of bed formation; more vulnerable areas) of Argentina in the following years, by means of ecological niche modelling, field experiments and wave exposure modelling (WEMo). Environmental variables in the model include surface seawater temperature (SST), atmospheric temperature (AT), substrate type, and relative exposition to the breaking waves. SST indicates that the species will be able to form banks from Puerto Deseado ria (47.7ºS, Argentina) and Paranaguá (25.7ºS, Brazil) while AT predicted range of occupation spans from San Julian port (49.3ºS, Argentina) and Garopaba-Rio Grande (28.0º–32.0ºS, Brazil). The species recruits on all of the most widespread natural hard substrates in the region, including ignimbritic rhyolites (IR), medium-grain sandstone (MSS), fine-grain lime sandstone (LSS), polymictic conglomerate (PC), as well as in artificial substrates (e.g., concrete), but highest recruits per unit area were observed for PC. Although C. gigas can settle on sites with a wide range of exposure indexes, beds can only form in areas with low and mid exposure indices. Crassostrea gigas has occupied the intertidal/shallow subtidal of northern (36.4ºS) and southern Buenos Aires and north of Rio Negro provinces (37º-39ºS), and continues its expansion. Since this ecosystem engineer is causing changes to the coastal geomorphology and producing impacts on traditional economic activities, the objective of our study is to develop a predictive model allowing to establish the most likely patterns of occupation of the intetidal (geographical range; most likely sites of bed formation; more vulnerable areas) of Argentina in the following years, by means of ecological niche modelling, field experiments and wave exposure modelling (WEMo). Environmental variables in the model include surface seawater temperature (SST), atmospheric temperature (AT), substrate type, and relative exposition to the breaking waves. SST indicates that the species will be able to form banks from Puerto Deseado ria (47.7ºS, Argentina) and Paranaguá (25.7ºS, Brazil) while AT predicted range of occupation spans from San Julian port (49.3ºS, Argentina) and Garopaba-Rio Grande (28.0º–32.0ºS, Brazil). The species recruits on all of the most widespread natural hard substrates in the region, including ignimbritic rhyolites (IR), medium-grain sandstone (MSS), fine-grain lime sandstone (LSS), polymictic conglomerate (PC), as well as in artificial substrates (e.g., concrete), but highest recruits per unit area were observed for PC. Although C. gigas can settle on sites with a wide range of exposure indexes, beds can only form in areas with low and mid exposure indices.