Effects of an estuarine invader reef-polychaete in macroalgae biomass and their role as habitat

BAZTERRICA, C; ALVAREZ, MF; BRUSCHETTI, CM; BOTTO, F; IRIBARNE, O

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

Biological invasions can modify species distribution of native communities and also their ecological role. We investigated the effects of the reef forming polychaete Ficopomatus enigmaticus invasion on the biomass and distribution of estuarine macroalgae in Mar Chiquita Coastal lagoon (37° 40′S, 57° 23′W), Argentina, and the importance of macroalgae as autogenic ecosystem engineer in relation to F. enigmaticus reefs, in order to expanding theoretical and evaluating tools for biologicalinvasions management. We showed that (1) the red macroalga Polysiphonia subtilissima grows almost exclusively on the reef surfaces; (2) the green macroalgae (mainly Cladophora sp.) are found almost exclusively in areas without reefs attached to mollusk shells; (3) no macroalgae occur in the sediment between reefs; (4) macroalgae as autogenic ecosystem engineer are relatively important in reef surfaces and in the valves of the sediment from areas without reefs. Manipulative experiments show that (1) reefs provide a complex substrate for settlement and survival that benefit red macroalga; (2) the invasive reef builder has negative indirect effects on green macroalgae probably by increasing sedimentation and grazing; (3) the structure of the macroalgae thallus affects, direct and indirectly, the abundance of the invertebrates even on highly structured surfaces such as reefs and shells from the sediment. In conclusions, reefs change the relative biomass contribution of each macroalgal species to the overall production in the lagoon and the role of macroalgae as ecosystem engineers persisted despite this invasive event that changed the  environmental heterogeneity of the system.