Effects of nutrient enrichment and grazing by an invasive filter feeder on phytoplankton biomass in a South West Atlantic coastal lagoon

BRUSCHETTI, C.M.; ADDINO, M.; TOMAS LUPPI; OSCAR IRIBARNE

BIOLOGICAL INVASIONS

SPRINGER

Lugar: Berlin; Año: 2018 p. 2245 - 2256

1387-3547

Invasive species can exert strong effects on structure and function of marineecosystem. In estuaries, nutrient enhancement due to anthropogenic activities canincrease microalgal biomass but invading filter-feeders can eventually regulate theirabundance. This is what we hypothesized that is happening in a SW Atlantic coastallagoon (Mar Chiquita, 37° 40′S, 57° 23´W, Argentina) invaded by the polychaeteFicopomatus enigmaticus. Here, we experimentally evaluated this hypothesis in amesocosms experiment. Four treatments were performed: T1) with nutrients (NO3,PO4 and NH4), T2) with reefs and nutrients, T3) with reefs, and T4) without reefs ornutrients. Water samples were obtained to determine in vivo chlorophyll a (Chla) andnutrients concentration. Additionally, to evaluate the trophic position and particleselectivity by the polychaete, analysis of stable isotopes of particulate organic matter(POM) of the water and individuals were performed. Stable isotopes analysis showedthat the main resource used by F. enigmaticus was the fraction of POM between 62 μmand 250 μm, showing particle selectivity and suggesting that the reefs have thepotential to promote shifts in size, composition and biomass of local food source.Mesocosms experiments showed that nutrient supply increased the Chlaconcentration, but when reefs were added, the Chla decreased. Thus, nutrientsincreased the phytoplankton biomass but grazing by the reefs counteracted theseincrements. This indicates that an invader such as F. enigmaticus might modulate ananthropogenic impact via suspension feeding, and therefore its role in mitigate theconsequences of eutrophication may be highly important.