Stable isotopes reveal different dependencies on benthic and pelagic pathways between Munida gregaria ecotypes

IRIGOYEN, A.J.; TROBBIANI, G.A.; FUNES, M.; GALVÁN, D.E.

Food Webs

Elsevier

Año: 2018 vol. 17

2352-2496

Forage species are key nodes in the energy fluxes between benthic and pelagic zones. The squat lobster, Munidagregaria, is a common forage species of the Southern Hemisphere and its abundance is increasing. This speciespresents two ecotypes: one (subrugosa) that settles on the sea bottom immediately after the metamorphosisand another (gregaria) that remains in the water column for a variable period of time, before adopting a benthichabit. Hypotheses on its settlement are conflicting; one proposes that it is a density-dependent process of the seabottom and the other that it is regulated by the availability of pelagic food. To rule out whether feeding factorscould be significant in the decision-making process, the first step is to identify whether the ecotypes have differentdiets or not. This study compared the isotopic niche location, the trophic levels and the reliance on benthic orpelagic resources between ecotypes. Among all sampling events, the isotopic niches of the gregaria and thesubrugosa ecotypeswere significantly distant fromeach other. In addition, the difference in δ13C values betweenecotypes covered an average of 75% of the total difference between pelagic and benthic pathways. Benthic individualsrelied mostly on benthic animals, while pelagic individuals relied on pelagic primary producers. Overall,results show that each ecotype feeds mainly on different energy pathways. Considering its feeding ecology andmovements during life history, M. gregaria is a key component of bentho-pelagic coupling.