Trophic ecology of the surf zone community in the sw atlantic coast: an stable isotopes approach.

CARCEDO, MC; BLASINA, G; MOLINA, JM; SCOTTI, MARCO; ITO, MAYSA; MENENDEZ, MC; DUTTO, MS; MARTINEZ, A; CARDONA GARZÓN, J.; MOYANO, J.; LOPEZ CAZORLA, A; FIORI, SM

Mar del Plata

Congreso; XVIII Congreso Latinoamericano de Ciencias del Mar-COLACMAR 2019; 2019

Asociación Latinoamericana de Investigadores en Ciencias del Mar

The communities inhabiting the surf-zones of exposed sandy beaches have received little attention, with the trophic ecology of species the main focus in these areas. The main objective of this study was to explore the trophic niche of co-occurring pelagic and benthic species of the surf-zone of sandy beaches of the SW Atlantic coast. Specifically, we aim to know the trophic positions (TL) of the organisms, their feeding preferences and the possible overlap between trophic niches, in order to detect possible similarities in resource use within this area. Samples of zooplankton, macrobenthos and fishes were taken from the surf-zone across 200 m transects parallel to the shore with the appropriate method for each biological group. Organisms and tissues were freeze dried and grounded into a homogeneous powder. Aliquots (0.06-0.1 mg) were transferred to tin capsules and analyzed by simultaneous analysis of nitrogen (δ15N) and carbon (δ13C). Isotopic niche width and overlap determinations were calculated using corrected standard elliptical area (SEAc) (Jackson et al. 2011). Zooplanktonic species presented δ13C values varying from -20.8 to -18.7. The copepod Acartia tonsa had δ15N values between 12.1−12.5 (TL=3) while Paracalanus parvus and Euterpina acutifrons had lower δ15N values, from 9.1−11.6 (TL=2). Within the macrobenthos, with the epibenthic isopod Leptoserolis bonaerensis and the epibenthic amphipod Phoxocephalopsis zimmeri, presented δ13C mean values of -13.8 and -16.2 respectively. Both species had similar δ15N values, around 11.5−11.9 and a TL=3, showing an overlap in their? SEAc ( ~30%), indicating the existence of shared resources between these species. In the case of macrobenthic species with hyperbenthic habit like the mysids Pseudobranchiomysis arenae and Arthromysis magellanica, their δ13C values ranged between -16.8 to -18.4. Trophic niches of both mysids did not overlap, showing a separation in δ15N values: 10.9−11.6 and 12.4−12.7 respectively, belonging to different trophic levels (TL=2 and TL=3 respectively). Two fishes were found inhabiting the surf-zone, Odonthestes argentinensis and Ramnogaster arcuata. Their δ13C values ranged between -17.4 to -17.9 and from -18.5 to -18.9, respectively. Both species showed similar values of δ15N, around 13.5 and 15, and therefore belong to similar TLs: 3.5 and 4 respectively. No overlap was detected, suggesting a different resource use for these two species. Our study suggest the existence of significant niche segregation in the assemblages of the surf-zone of sandy beaches, essential for the coexistence of species inhabiting this inherently dynamic ecosystem.