|Fingerprints of lagoonal life: Migration of the marine flatfish Solea solea assessed by stable isotopes and otolith microchemistry |
(Article) Publié: Estuarine, Coastal And Shelf Science, vol. 104 p.23-32 (2012)
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The commercially important marine flatfish common sole (Solea solea) facultatively uses NW Mediterranean lagoons as nurseries. To assess the imprint left by the lagoonal passage, muscle carbon (C) and nitrogen (N) isotope values of S. solea juveniles caught in Mauguio lagoon in spring (shortly after arrival from the sea) and in autumn (before the return to the sea) were compared with values of juveniles from adjacent coastal marine nurseries. In addition, in the lagoon, sole otolith stable isotope (C and oxygen (0)) and elemental (11 elements) composition in spring and autumn, and the stable isotope composition (C and N) of organic matter sources in autumn, were determined. Overall, our data indicate that a distinct lagoonal signature existed. Specifically, lagoon soles showed a strong enrichment in muscle tissue N-15 (>6 parts per thousand) compared to their coastal relatives, likely linked to sewage inputs (see below), and a depletion in C-13 (1-2 parts per thousand), indicative of higher importance of C-13 depleted terrestrial POM in the lagoon compared to coastal nurseries. In addition, over the time spent in the lagoon, sole otolith delta C-13 and delta O-18 values and otolith elemental composition changed significantly. Analysis of the lagoon sole foodweb based on C and N isotopes placed sediment particulate organic matter (POM) at the base. Seagrasses, formerly common but in decline in Mauguio lagoon, played a minor role in the detritus cycle. The very strong N-15 enrichment of the entire foodweb (+7 to +11 parts per thousand) compared to little impacted lagoons and coastal areas testified of important human sewage inputs. Regarding the S. solea migration, the analysis of higher turnover and fast growth muscle tissue and metabolically inert and slower growth otoliths indicated that soles arrived at least several weeks prior to capture in spring, and that no migrations took place in summer. In the autumn, the high muscle delta N-15 value acquired in Mauguio lagoon would be a good marker of recent return to the sea, whereas altered otolith delta O-18 values and elemental ratios hold promise as long-term markers. The combination of several complementary tracers from muscle and otoliths may present the chance to distinguish between fish from specific lagoons and coastal nurseries in the future. (C) 2011 Elsevier Ltd. All rights reserved.