Food web structure of the benthic community at the Porcupine Abyssal Plain(NE Atlantic): a stable isotope analysis

Citation
K. Iken et al., Food web structure of the benthic community at the Porcupine Abyssal Plain(NE Atlantic): a stable isotope analysis, PROG OCEAN, 50(1-4), 2001, pp. 383-405
Citations number
100
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Earth Sciences
Journal title
PROGRESS IN OCEANOGRAPHY
ISSN journal
0079-6611 → ACNP
Volume
50
Issue
1-4
Year of publication
2001
Pages
383 - 405
Database
ISI
SICI code
0079-6611(2001)50:1-4<383:FWSOTB>2.0.ZU;2-B
Abstract
The deep-sea benthic community at the Porcupine Abyssal Plain (NE Atlantic) is a highly food limited system. The annual input of sedimenting phytodetr itus, which reaches the sea floor around May/June, is the major input of en ergy. The relative trophic position of the most abundant components of the benthos (90 species or higher taxonomic groups), including meiofaunal, macr ofaunal, and megafaunal organisms, was evaluated by :stable isotope analysi s. The majority of the macro- and megafaunal organisms investigated were de posit feeders (N=35), less numerous were suspension feeders (N=17) and pred ators/scavengers (N=29). Stable nitrogen values overlap and cover a large r ange within feeding types, indicating a strong overlap in food sources and a high degree of competition for food. Suspension feeders, mainly cnidarian s, have a broad trophic spectrum through feeding on resuspended material as well as capturing pelagic prey; thus during the greater part of the year t hey can compensate for any shortage in sedimenting fresh POM. Benthic depos it feeders use a variety of feeding strategies to exploit their common food resource. The holothurians, the dominant megabenthic group at PAP, include d some highly mobile species, which seem to be quite efficient in tracing a nd exploiting localised patches of nutritious phytodetritus. Other holothur ian species, however, forage successfully on more refractory material, poss ibly assisted by enteric bacteria. Predators/scavengers fall into two group s, representing two major trophic pathways. Firstly, several of the inverte brate predators prey on deposit-feeding organisms and so are the end consum ers of an exclusively benthic food web. Secondly, there are highly mobile b enthopelagic predators/scavengers, which are a major link with the benthope lagic food web through their feeding on pelagic prey. Generally, within the benthic community at PAP competition for food is redu ced by two alternative evolutionary adaptations: (1) specialization on slig htly different food sources and (2) vertical expansion of the trophic spect rum. This leads to a rather complex food web, covering a total delta N-15 r ange of at least 10%o. (C) 2001 Elsevier Science Ltd. All rights reserved.