Factors controlling macroalgae assemblages in a Southwest Atlantic coastal lagoon modified by an invading reef forming polychaete

BAZTERRICA, M.CIELO; ALVAREZ, M. FERNANDA; BRUSCHETTI, MARTÍN; FERNANDO HIDALGO; FANJUL, EUGENIA; IRIBARNE, OSCAR; BOTTO, FLORENCIA

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 443 p. 169 - 177

0022-0981

In the SW Atlantic Mar Chiquita coastal lagoon (37° 40´S, 57° 23°W, Argentina) the invasive reef building polychaete Ficopomatus enigmaticus can directly and indirectly change the composition and abundance of primary producers by providing habitat to some species and excluding others. The magnitude of these effects may be regulated by consumers and nutrients availability. Here we evaluate the relative importance of consumers (large consumers: birds, fish and crabs; small consumers: amphipods, hydrobiid snails and crabs) and nutrients in controlling macroalgae development on the reefs and on the sediment in areas without reefs. Experiments showed that large consumers positively affect green macroalgae development in the sediment of areas without reefs, probably by enhancing availability of bivalve shells for macroalgae attachment, but had no effects on the development of red and green macroalgae on the reefs. No effect of nutrient addition on macroalgal biomass was detected. Small consumers, however, negatively affected the development of the green alga Cladophora sp., probably by direct consumption, and had a positive effect on the biomass of the red alga Polysiphonia subtilissima. These interactions would determine the abundance of macroalgae, the state of algal mats (e.g., thallus damage) and the spatial distribution (e.g., macroalgae patchiness). Consequently, the effect of an invader ecosystem engineer in the composition of species assemblages may be mediated by other community structuring forces, which in turn may have different effects according their interaction with the invader.