Trophic Ecology in Marine Ecosystems from the Balearic Sea (Western Mediterraniean)

dc.contributor
Universitat de les Illes Balears. Departament de Biologia
dc.contributor.author
Valls Mir, Maria
dc.date.accessioned
2018-02-08T11:47:12Z
dc.date.available
2018-02-08T11:47:12Z
dc.date.issued
2017-07-28
dc.identifier.uri
http://hdl.handle.net/10803/461496
dc.description.abstract
The conservation of marine ecosystem structure and functioning is a priority target within the context of the environmental management. This is especially important in oligotrophic systems such as the Balearic Sea, where food availability is a limiting factor. For such a target is fundamental to know the array of predator-prey interactions as a basis to understand the food web trophodynamics. In this Thesis, the trophic structure of the pelagic and benthic habitats off the Balearic Islands and the feeding ecology of three taxonomic groups (cephalopods, elasmobranchs and mesopelagic fishes) playing a key role in marine ecosystems, were investigated A relatively large food web (89 species) encompassing both the pelagic and the benthic habitats were analysed. The food webs extended up to 4 trophic levels in both habitats, and most species occupied intermediate trophic levels. A high partitioning rate of trophic resources was found, which might be related to the reduction of competition for food. The energy link between the pelagic and benthic communities (benthopelagic coupling; BPC) was stronger on the shelf break, where higher hydrodinamism mix the water column and associated nutrients, than on the slope. The geographical variability of oceanographic drivers (i.e. eddies, currents) influenced the strength of the BPC. Regarding species trophic interactions, stomach contents provided evidence of mesopelagic prey coupling pelagic and benthic habitats, especially down the shelf break. Rays from the shelf consumed mainly decapod crustaceans and teleosts, whereas sharks from the slope fed primarily upon mesopelagic prey (i.e myctophids, euphausiids). Sharks and rays variation in diet was driven by species specific ontogenetic stages and habitat use. The diet of the two squid Loligo vulgaris and L. forbesii, examined for the first time in the Mediterranean, showed their highly piscivorous habits. Their prey composition revealed a lack of diet overlap as a result of their bathymetric segregation. Both squids showed shifts in diet related to size and their reproduction period. The squid L. vulgaris feed on small benthic prey until they reach a size threshold and feed on benthopelagic fish thereafter. Seasonal changes in diet in both squid species, likely related to reproduction, might help improving their individual body condition. During this period, L. vulgaris increased the consumption of highly nutritive polychaetes, whereas the adults of L. forbesii carried out movements to deeper waters to feed on lipid-rich mesopelagic prey. Mesopelagic prey are important food resources for demersal species in the Balearic Sea and, as a result of their nycthemeral movements, they have important implications for the transport of mass and energy through the water column. The trophodynamics of this group revealed that food sources (δ13C) varied little over the spatial scales sampled (location and depth) but showed high seasonality, reflecting intra-annual changes in the species composition of the phytoplankton community. By contrast, spatio-temporal variations of mesopelagic trophic interactions (δ15N) were minimal. Important niche segregation was observed between the non-migratory stomiiforms and some of the extensive migratory myctophids. Finally, the comparative analysis of the trophic ecology of deep-sea cephalopods and elasmobranchs showed that they displayed different feeding strategies with a clear resource partitioning between and within taxa. Segregation of the isotopic space indicated a contrasting food source gradient (δ13C) stretching from pelagic (squids and cuttlefishes) to nektobenthic (octopuses and elasmobranchs) sources. However, deep-sea sharks off the Balearic Islands frequently preyed on mesopelagic species, as did squids and cuttlefishes. Cephalopods, in turn, constituted an important food resource for deep-sea sharks. Squid and shark species identified as benthopelagic feeders, play a key role in the transport of energy from midwater regions to the benthic community.
en_US
dc.format.extent
180 p.
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dc.format.mimetype
application/pdf
dc.language.iso
eng
en_US
dc.publisher
Universitat de les Illes Balears
dc.rights.license
ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs.
dc.source
TDX (Tesis Doctorals en Xarxa)
dc.subject
Stomach contents
en_US
dc.subject
Stable isotopes
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dc.subject
Resource partitioning
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dc.subject
Food web
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dc.subject
Benthopelagic coupling
en_US
dc.subject
Elasmobranchs
en_US
dc.subject
Cephalopods
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dc.subject
Mesopelagic fish
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dc.subject
Trophic level
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dc.subject
Feeding strategy
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dc.subject
Diet shift
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dc.subject
Shelf
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dc.subject
Slope
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dc.subject
Western Mediterranean
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dc.subject.other
Ecologia de comunitats marines: Ecologia tròfica, xarxes tròfiques marines
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dc.title
Trophic Ecology in Marine Ecosystems from the Balearic Sea (Western Mediterraniean)
en_US
dc.type
info:eu-repo/semantics/doctoralThesis
dc.type
info:eu-repo/semantics/publishedVersion
dc.subject.udc
57
en_US
dc.subject.udc
574
en_US
dc.contributor.director
Quetglas, Antoni
dc.contributor.codirector
Moyà Niell, Gabriel
dc.embargo.terms
cap
en_US
dc.rights.accessLevel
info:eu-repo/semantics/openAccess


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