The isotopic niche of odontocetes in the southwestern Atlantic Ocean and its relation to environmental isotopic patterns

Cibele Troina, G. (Speaker), Silvina Botta (Contributor), Elskens, M. (Contributor), Dehairs, F. (Contributor), Eduardo R. Secchi (Contributor)

Activiteit: Talk or presentation at a conference

Description

We analyzed carbon (δ13C) and nitrogen (δ15N) stable isotope composition (SIC) in skin tissues of seven odontocete species along the outer continental shelf and slope off Brazil: Stenella attenuata, Stenella frontalis, Stenella longirostris, Tursiops truncatus, Delphinus delphis and Steno bredanensis (Delphinidae) and Physeter macrocephalus (Physeteridae). SIC at the base of the food web (basal: Particulate Organic Matter = POM and zooplankton) was used to understand patterns in isotopic variability in top predators and how shifts in basal isotopic composition are propagated into top predators. The sampling area was divided into four sub-areas with distinct oceanographic characteristics: south-shelfbreak (S-SB, ≈34°S – 28°S), south-offshore (S-off), southeast-shelfbreak (SE-SB, ≈28°S – 24°S) and southeast-offshore (SE-off). We calculated the Standard Ellipse Area (SEA) of the isotopic niche for POM, zooplankton and cetaceans for each area using Stable Isotope Ellipses in R (SIBER). There was no statistical difference in basal δ13C among the different areas (Mean ± SD -21.5±1.5‰). However, basal δ15N values were significantly higher in S-SB (POM: 6.2±2.4‰; zooplankton: 5.8±2.8‰) than in the other areas. In general, models estimated larger basal’ SEA for S-SB and SE-SB, both areas subject to a greater influence of continental waters or upwelling events. Highest mean δ15N values were observed in S. bredanensis (17.9±0.5‰) and D. delphis (15.3±1.5‰). These two species were sighted only in the southern area, which had higher basal δ15N values. Moreover, cetaceans sampled along the southern area had larger SEA. Regarding those species registered in both areas (T. truncatus, S. frontalis and S. longirostris), all individuals sampled in the south had higher average δ15N values than their southeastern counterparts. Thus, higher δ15N might result from shifted basal δ15N values which are being propagated up the food web rather than from a higher trophic position of the southern dolphin groups.
Periode23 okt 201727 okt 2017
EvenementstitelSociety for Marine Mammology: 22nd Biennial Conference on the Biology of Marine Mammals
EvenementstypeConference
Conferentienummer22
LocatieHalifax, Canada
Mate van erkenningInternational