THE SPREAD OF NON-INDIGENOUS INVASIVE SPECIES OF MACROALGAES COULD CHANGE THE ROCKY INTERTIDAL ASSEMBLAGE COMPOSITION

MARINA QUIROGA; GABRIELA PALOMO; MARIA BAGUR

Mar del Plata

Conferencia; 2nd World Conference on Biological Invasions and Ecosystem Functioning; 2011

Grupo de Investigación y Educación en Temas Ambientales (GrIETA)

Data about biodiversity and its changes through time and space can serve to identify processes of biodiversity loss. The detection of invasive species during long term monitoring studies can allow scientists evaluate their impact on biodiversity. In this study we investigate the spread of the non-indigenous invasive macroalgaes Ahnfeltiopsis devoniensis (Rhodophyta, Phyllophoraceae) and Schizymenia dubyi (Rhodophyta, Schizymeniaceae) on the intertidal rocky shore of Mar del Plata, Argentina (38° S, 57° W). Invertebrates and macroalgae were sampled both in summer and winter from February 2007 to January 2011, and at three different tidal levels. Five quadrats (0.25 m2) were scraped at each level and all the organisms were collected for the quantification of biomass. A total of 55 taxa were found and organisms were identified to the species level in most cases. Sparse A. devoniensis thalli (2.6 % relative abundance) were detected at the lower intertidal level in February 2007. However, by January 2011 their relative abundance increased to 11.36 %. A. devoniensis biomass showed a 27 fold increase during that period. Schizymenia dubyi were detected at lower intertidal level in January 2010 showing a relative abundance of 2, 38% that by January 2011 increased to 4, 59%. S. dubyi biomass was increased almost 100%. Both species were spread along the three intertidal levels. The effects of these exotic algae on assemblage structure could be important since both could displace B. rodriguezii – an ecosystem engineer that creates microhabitat for a large number of other organisms.