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Food-web structure and trophodynamics of mesopelagic-suprabenthic bathyal macrofauna of the Algerian Basin based on stable isotopes of carbon and nitrogen

TitleFood-web structure and trophodynamics of mesopelagic-suprabenthic bathyal macrofauna of the Algerian Basin based on stable isotopes of carbon and nitrogen
Publication TypeArticolo su Rivista peer-reviewed
Year of Publication2009
AuthorsFanelli, E., Cartes J.E., Rumolo P., and Sprovieri M.
JournalDeep-Sea Research Part I: Oceanographic Research Papers
Volume56
Pagination1504-1520
ISSN09670637
KeywordsAlgerian Basin, Amphipoda, Animals, Balearic Islands, benthos, Biological materials, boundary layer, Cabrera, Chlorophyll, community structure, Copepoda, Cumacea, Cyclaspis longicaudata, Cyclothone, Deep sea, Deposits, Ecology, environmental factor, Environmental factors, Euphausiidae, Eurasia, Europe, Farm buildings, Feeding, food web, Gnathia, Hyperiidae, Isotopes, isotopic analysis, isotopic composition, Lepechinella, Majorca, Meats, Mediterranean Sea, Mesopelagic macrofauna, Munnopsurus atlanticus, Nicippe tumida, Ocean habitats, Pasiphaea multidentata, Phrosina semilunata, Platysympus typicus, Porphyrins, Praniza, Rhachotropis, Salpida, Southern Europe, Spain, stable isotope, Stable isotopes analysis, Suprabenthos, temporal variation, Temporal variations, Vibilia armata, Western Mediterranean, zooplankton
Abstract

The trophodynamics of mesopelagic (macrozooplankton/micronekton) and benthic boundary layer (suprabenthos=hyperbenthos) faunas from the Algerian Basin were characterized on a seasonal scale through stable carbon and nitrogen isotopic analyses of a total of 34 species and two broad taxa (Copepoda and Cumacea). This is the first study simultaneously focused on trophodynamics of deep-sea zooplankton and suprabenthos. Samples were collected southeast of Mallorca (Algerian Basin, Western Mediterranean), on the continental slope close to Cabrera Archipelago, at 650-780 m depths, ca. bi-monthly between August 2003 and June 2004. Mean δ13C values of suprabenthos ranged from -21.1‰ (Munnopsurus atlanticus) to -16.7‰ (Cyclaspis longicaudata). Values of δ15N ranged from 2.8‰ (Lepechinella manco) to 9.9‰ (larvae of Gnathia sp.). The stable isotope ratios of suprabenthic fauna displayed a continuum of values, confirming a wide spectrum of feeding guilds (from filter feeders/surface deposit feeders to predators). According to the available information on diets for suprabenthic species, the highest annual mean δ15N values were found for the hematophagous isopod Gnathia sp. parasite on fish (represented by Praniza larvae) and carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods, and the lowest δ15N values were found for two cumaceans (Cyclaspis longicaudata and Platysympus typicus) feeding on detritus. Assuming a 15N-enrichment factor of 2.5‰ and deposit feeders as baseline, we found three trophic levels in suprabenthic food webs. δ13C ranges were particularly wide among deposit feeders (ranging from -21.8% to -17.3‰) and omnivores (from -20.5% to -18.8‰), suggesting exploitation of particulate organic matter (POM) of different characteristics. Our isotopic analyses revealed lower ranges of δ13C and δ15N for macrozooplankton/micronekton, compared with suprabenthos. δ13C values of zooplankton taxa ranged from -21.1‰ (the hyperiid Phrosina semilunata) to -19.9‰ (the decapod Pasiphaea multidentata), while δ15N values ranged from 3.9‰ (P. semilunata) to 7.5‰ (P. multidentata). Among zooplankton, more enriched δ15N values were found among carnivores (e.g. the fish Cyclothone spp. and Pasiphaea multidentata) preying on copepods, hyperiids, euphausiids and small fish. The lowest δ15N values were found for hyperiids that feed on the mucus nets of salps (e.g. Vibilia armata). After contrasting isotope analysis with dietary data, we conclude there were two trophic levels among zooplankton/micronekton. Strong correlation between the mean annual δ15N and δ13C values was found for zooplankton (R2=0.7), but not for suprabenthos, which suggests a single source of carbon for plankton. We found a general seasonal trend for δ13C enrichment from late autumn (November) to late winter-spring (February-April) for both suprabenthos and zooplankton. The δ13C enrichment in February-April was correlated in zooplankton with higher surface chlorophyll a concentration 1 month before sampling. As evidenced by δ13C-δ15N correlations, the response of zooplankton to the peak of surface primary production was almost immediate (an increase of δ13C-δ15N correlations in February), and stronger than for suprabenthos. The response among suprabenthos was weak, with slight increase in δ13C-δ15N relationships in April-June. © 2009 Elsevier Ltd. All rights reserved.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-67649641787&doi=10.1016%2fj.dsr.2009.04.004&partnerID=40&md5=4741cf21a80ae7972eda14cf1bbe0e7c
DOI10.1016/j.dsr.2009.04.004
Citation KeyFanelli20091504