Antarctic food web architecture under varying dynamics of sea ice cover

Abstract

In the Ross Sea, biodiversity organisation is strongly influenced by sea-ice cover, which is characterised by marked spatio-temporal variations. Expected changes in seasonal sea-ice dynamics will be reflected in food web architecture, providing a unique opportunity to study effects of climate change. Based on individual stable isotope analyses and the high taxonomic resolution of sampled specimens, we described benthic food webs in contrasting conditions of seasonal sea-ice persistence (early vs. late sea-ice break up) in medium-depth waters in Terra Nova Bay (Ross Sea). The architecture of biodiversity was reshaped by the pulsed input of sympagic food sources following sea-ice break up, with food web simplification, decreased intraguild predation, potential disturbance propagation and increased vulnerability to biodiversity loss. Following our approach, it was possible to describe in unprecedented detail the complex structure of biodiverse communities, emphasising the role of sympagic inputs, regulated by sea-ice dynamics, in structuring Antarctic medium-depth benthic food webs.

Changing Isotopic Food Webs of Two Economically Important Fish in Mediterranean Coastal Lakes with Different Trophic Status

“…Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis is increasingly becoming useful tool for detecting organic and inorganic matter sources and understanding species' foraging behaviour and the relationships between organisms. It is thus useful for reconstructing food webs in aquatic ecosystems [7,[29][30][31]. The isotopic ratio of these elements in consumer tissues reflects that of the assimilated food sources in a predictable way [7,32].…”

“…This makes it possible to disentangle the contribution of various basal sources to food networks [7,31,[33][34][35][36]. The δ 15 N values gradually increase with each trophic level, thus providing information on the position of organisms in the food web [31,37,38]. In parallel, the δ 15 N values of primary producers reflect the nature (organic or inorganic) and the source of nitrogen inputs (natural or anthropogenic) in a predictable way.…”

“…The main purpose of this study was to describe and analyse the diets and food webs of the eel Anguilla anguilla and the annular seabream Diplodus annularis in three neighbouring Mediterranean coastal lakes characterised by different eutrophication levels. It is known that energy flows and the transfer of nutrients depend primarily on the foraging choices of each organism within the community [31]. Similarly, the high trophic generalism and omnivory generally observed in A. anguilla and D. annularis [19,24,25,42,43] can be the result of different foraging strategies adopted by each individual within their respective populations.…”

“…In order to obtain highly detailed information and to consider variability in the use of resources by A. anguilla and D. annularis, the diet of the two species was obtained from trophic links of each individual within a population as determined by means of the Isotopic Trophic Unit (ITU) approach [31].…”

“…Isotopic Trophic Units are defined as groups of individuals with similar isotopic signatures occupying the same position in the δ 13 C-δ 15 N niche space [31].…”