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What is the menu today in a subantarctic kelp food web from the Kerguelen Islands? Phytodetritus, phytoplankton and phytobenthos; not living kelp
Ist Teil von
Marine biology, 2022-09, Vol.169 (9), Article 118
Ort / Verlag
Berlin/Heidelberg: Springer Berlin Heidelberg
Erscheinungsjahr
2022
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Kelp forests dominated by
Macrocystis pyrifera
are widely distributed in coastal waters from boreal, temperate and subantarctic regions. This widespread distribution may result in regional differences in food web structure and functioning. In temperate northern regions, where most studies on kelp forest benthic food webs have been conducted, kelp grazing is a well-documented phenomenon and can lead to the overgrazing of
M. pyrifera
by sea urchins when their predators (e.g., sea otters) are absent. In contrast, little is known about their counterparts in subantarctic areas. The present study aimed to reconstruct the benthic food web of a kelp forest dominated by
M. pyrifera
in a subantarctic environment using stable isotope analysis. Stable carbon (δ
13
C), nitrogen (δ
15
N) and sulfur (δ
34
S) isotope ratios were measured from food sources (macrophytobenthos, suspended particulate organic matter SPOM, and sediment) and consumers (sponges, bivalves, gastropods, sedentary and mobile polychaetes, arthropods and echinoderms) which were sampled in a kelp forest of the Kerguelen archipelago. Mixing models highlighted two interconnected trophic pathways which were either supported by SPOM and resuspended macrophytobenthos detritus (bentho-pelagic), or by live micro/macrophytobenthos (phytobenthos-based). No major prey were highlighted for several consumers, indicating the existence of potential supplementary trophic pathways. No consumer relying primarily on living
M. pyrifera
was highlighted by the mixing models. The investigated kelp forest is hence a complex ecosystem supporting multiple trophic pathways, and direct consumption of
M. pyrifera
is limited. Nonetheless,
M. pyrifera
and other macrophytobenthos species may constitute a pool of detritus supporting several trophic pathways.