Feeding relationships in Mediterranean bathyal assemblages elucidated by carbon and nitrogen stable-isotope data

Abstract

3 faunally-distinct depth zones: 200 to 800 m (upper slope), 800 to 1425 m (middle slope) and 1425 to 1800 m (lower slope). Differences in δ 15 N and δ 13 C between October 1996 and May 1998 were observed only in the crustaceans Aristeus antennatus and Nematocarcinus exilis. There were few differences among depths in δ 15 N or δ 13 C of benthic fishes or crustaceans: the shrimps A. antennatus and Acanthephyra eximia showed higher δ 15 N values at greater depth, and δ 13 C values of the fishes Alepocephalus rostratus (Alepocephalidae) and Coelorhynchus coelorhynchus (Macrouridae) also tended to increase with increasing depth. Differences in plankton and suprabenthos were also observed among zones (at depth, greater δ 15 N values of gelatinous plankton, calanoid copepods and peracarids were recorded, along with smaller δ 13 C values of gelatinous plankton and peracarids). These are attributed to a microbially-mediated increase in δ 15 N and a reduction in δ 13 C of the particulate material remaining after preferential utilization of labile organic matter in the stable and relatively high (13°C) temperature of the Mediterranean water column. Strong positive correlations between δ 15 N and δ 13 C data for plankton, fishes and crustaceans indicated a single primary source material for these communities, which is attributed to marine snow.

Trophic Diversity of Plankton in the Epipelagic and Mesopelagic Layers of the Tropical and Equatorial Atlantic Determined with Stable Isotopes

“…Our results align with those of previous studies with stable isotopes suggesting a major importance of in situ feeding for deep zooplankton, mainly supported by the progressive increase of δ 15 N with depth in most species and groups [19][20][21]. However, the large variability observed in the niche overlap between layers, along with the increase in niche size with depth in oligotrophic zones, suggests that feeding migrations depend on the availability of prey, ultimately determined by the magnitude of zonal primary production.…”

“…A general increase of δ 15 N with depth, as found in all guilds in this study, was also reported in other studies with zooplankton [19][20][21]. Such an increase was interpreted as the consequence of the growing importance of omnivory and carnivory in deep layers depleted in phytoplankton.…”

“…In the case of trophic migrations in the ocean, a large overlap in the trophic niche of organisms collected in different layers would indicate intense and active migration between layers, while low niche overlap would apply to non-migrating, in situ feeders. Previous studies with zooplankton reported an increase in heavy nitrogen isotopes with depth that was interpreted as the result of changes in the quality of the organic matter (that is, microbial reworking) and trophic structure (that is, an increase of carnivory) from the surface to deep ocean layers [19][20][21]. These findings suggest that migration is restricted to adjacent layers.…”

Size Influence in Zonation Patterns in Fishes and Crustaceans from Deep-water Communities of the Western Mediterranean

“…The fish species with a positive relationship between mean weight and depth are the ones (mainly euphausiids), while on the lower slope zooplankton are the dominant food source of the dominant species, Alepocephalus rostratus (Carrasón, 1994). The deep-sea communities of the study area depend on plankton productivity as the main source of energy (Polunin et al, 2001).…”

A review of ecogeochemistry approaches to estimating movements of marine animals

“…However, some coastal regions, particularly shallow, enclosed or semi-enclosed bays with limited freshwater input, can become hypersaline and produce anomalously high d 18 O values (Lloyd 1966 Polunin et al 2001;Stuck et al 2001;Carlier et al 2007;Harmelin-Vivien et al 2008;Fanelli et al 2009Pinnegar et al 2000Stuck et al 2001;Bode et al 2007;Carlier et al 2007;HarmelinVivien et al 2008;Fanelli et al 2009 (Fig. 1A), and thus spatial variability in d 13 C at the base of the food web (d 13 C Base ) is primarily driven by the same physical parameters (temperature and [CO 2 ] aq ) that influence d 13 C DIC values.…”