Data from: Habitat dimensionality, temperature and feeding strategies as determinants of trophic structure in a marine food web

Disentangling the determinants of trophic structure is central to ecology.
The capacity to capture subjugate and consume a prey (i.e. gape
limitation) is a relevant limitation to acquire energy for most organisms,
especially those in smaller size ranges. This generates a size hierarchy
of trophic positions in which large organisms consume small ones. Body
size is tightly correlated to gape limitation and explains a large
fraction of variance in the body size-trophic position relationship.
However, a considerable fraction of variance still remains to be
explained. Consumer search space dimensionality (2D or 3D) and feeding
strategies, temperature and the size structure of primary producers can
alter the trophic structure, but tests based on information from natural
food webs are scarce. We generated specific predictions about the body
size trophic position relationship and evaluated them using information
from a subtropical South Atlantic coastal marine ecosystem: benthic realm
(2D, rocky shore and sandy beach) and the pelagic realm (3D). We
characterized this marine coastal food web based on stable isotopes of
carbon and nitrogen from 256 samples from primary producers (macroalgae
and phytoplankton) to large predators (sand shark) in summer and winter.
Consumer body size encompassed 6 orders of magnitude in weight from
10-2 to 6x104 g. Isotopic signal corresponded to an
integration of carbon sources from basal consumers to top predators. The
body size-trophic position relationship showed a linear positive
association with different slopes for the benthic and pelagic
environments. This implies a smaller predator prey size ratio for pelagic
(3D) with respect to benthic consumers (2D) as theoretically expected. No
seasonal differences were found in slopes and most of the overall variance
in benthic environments was largely explained by feeding strategies of the
different taxonomic groups. We provide an integrated evaluation on the
role of body size, consumer search space and feeding strategy to
understand the determinants of trophic position. Results demonstrate that
integrating Gape Limitation hypothesis, the dimensionality of consumer
search space and feeding strategies into a formal robust framework to
understand trophic structure is feasible even in complex natural
ecosystems.