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

BAZTERRICA, M CIELO; ALVAREZ, M. FERNANDA; BRUSCHETTI, MARTÍN; BOTTO F.; IRIBARNE, OSCAR

Mar del Plata

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

Grieta; www.grieta.org.ar

Biological invasions can modify species distribution of native communities and also their ecological role. We investigated theeffects of the reef forming polychaete Ficopomatus enigmaticus invasion on the biomass and distribution of estuarinemacroalgae in Mar Chiquita Coastal lagoon (37° 40′S, 57° 23′W), Argentina, and the importance of macroalgae as autogenicecosystem 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 thereef surfaces; (2) the green macroalgae (mainly Cladophora sp.) are found almost exclusively in areas without reefs attachedto mollusk shells; (3) no macroalgae occur in the sediment between reefs; (4) macroalgae as autogenic ecosystem engineerare relatively important in reef surfaces and in the valves of the sediment from areas without reefs. Manipulative experimentsshow that (1) reefs provide a complex substrate for settlement and survival that benefit red macroalga; (2) the invasive reefbuilder has negative indirect effects on green macroalgae probably by increasing sedimentation and grazing; (3) thestructure of the macroalgae thallus affects, direct and indirectly, the abundance of the invertebrates even on highly structuredsurfaces such as reefs and shells from the sediment. In conclusions, reefs change the relative biomass contribution of eachmacroalgal species to the overall production in the lagoon and the role of macroalgae as ecosystem engineers persisteddespite this invasive event that changed the environmental heterogeneity of the system.