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

BRUSCHETI, M.; ADDINO, M.; LUPPI, T; O. IRIBARNE,

BIOLOGICAL INVASIONS

SPRINGER

Lugar: Berlin; Año: 2018 vol. 20 p. 2245 - 2256

1387-3547

Invasive species can exert strong effects onstructure and function ofmarine ecosystem. In estuaries,nutrient enhancement due to anthropogenic activitiescan increase microalgal biomass but invading filterfeederscan eventually regulate their abundance. This iswhat we hypothesized that is happening in a SWAtlantic coastal lagoon (Mar Chiquita, 37400S,57230W, Argentina) invaded by the polychaete Ficopomatusenigmaticus. Here, we experimentally evaluatedthis hypothesis in a mesocosms experiment. Fourtreatments were performed: (T1) with nutrients (NO3,PO4 and NH4), (T2) with reefs and nutrients, (T3) withreefs, and (T4) without reefs or nutrients.Water sampleswere obtained to determine in vivo chlorophyll a (Chla)and nutrients concentration. Additionally, to evaluatethe trophic position and particle selectivity by thepolychaete, analysis of stable isotopes of particulateorganic matter (POM) of thewater and individuals wereperformed. Stable isotopes analysis showed that themain resource used by F. enigmaticuswas the fraction ofPOM between 62 and 250 lm, showing particle selectivityand suggesting that the reefs have the potential topromote shifts in size, composition and biomass of localfood source. Mesocosms experiments showed thatnutrient supply increased the Chla concentration, butwhen reefs were added, the Chla decreased. Thus,nutrients increased the phytoplankton biomass butgrazing by the reefs counteracted these increments.This indicates that an invader such as F. enigmaticusmightmodulate an anthropogenic impact via suspensionfeeding, and therefore its role in mitigate the consequencesof eutrophication may be highly important.