Trophic versus geographic structure in stable isotope signatures of pelagic seabirds breeding in the northeast Atlantic

Feeding ecology and geographic location are 2 major factors influencing animal stable isotope signatures, but their relative contributions are poorly understood, which limits the usefulness of stable isotope analysis in the study of animal ecology. To improve our knowledge of the main sources of isotopic variability at sea, we determined δ15N and δ13C signatures in the first primary feather of adult birds from 11 Procellariiform species (n = 609) across 16 northeast Atlantic localities, from Cape Verde (20°N) to Iceland (60°N). Post-breeding areas (where the studied feather is thought to be grown) were determined using light-level geolocation for 6 of the 11 species. Isotopic variability was geographically unstructured within the mid-northeast Atlantic (Macaronesian archipelagos), but trophically structured according to species and regardless of the breeding location, presumably as a result of trophic segregation among species. Indeed, the interspecific isotopic overlap resulting from combining δ15N and δ13C signatures of seabirds was low, which suggests that most species exploited exclusive trophic resources consistently across their geographic range. Species breeding in north temperate regions (Iceland, Scotland and Northern Ireland) showed enriched δ15N compared to the same or similar species breeding in tropical and subtropical regions, suggesting some differences in baseline levels between these regions. The present study illustrates a noticeable trophic segregation of northeast Atlantic Procellariiformes. Our results show that the isotopic approach has limited applicability for the study of animal movements in the northeast Atlantic at a regional scale, but is potentially useful for the study of long-distance migrations between large marine systems

Climate change in the Atlantic Ocean since the 1940's and the effects on the global climate

En aquest projecte s’ha estudiat la relació entre els canvis en les temperatures superficials de l’Oceà Atlàntic i els canvis en la circulació atmosfèrica en el segle XX. Concretament s’han analitzat dos períodes de estudi: el primer des del 1940 al 1960 i el segon des del 1980 fins al 2000. S’ha posat especial interès en les anomalies en les temperatures superficials del mar en la regió tropical de l’Oceà Atlàntic i la possible interconnexió amb els canvis climàtics observats i predits. Per a la realització de l’estudi s’han dut a terme una sèrie d’experiments utilitzant el model climàtic elaborat a la universitat d’UCLA (UCLA‐AGCM model). Els resultats obtinguts han estat analitzats en forma de mapes i figures per a cada variable d’estudi. També s’ha fet una comparació entre els resultats obtinguts i altres trobats en altres treballs publicats sobre el mateix tema de recerca. Els resultats obtinguts són molt amplis i poden tenir diverses interpretacions. Tot i així algunes de les conclusions a les quals s’ha arribat són: les diferències més significatives per a les variables estudiades i trobades a partir dels resultats obtinguts del model per als dos períodes d’estudi són en els mesos d’hivern i a la zona dels tròpics; concretament a parts del nord de sud Amèrica i a parts del nord d’Àfrica. S’han trobat també canvis significatius en els patrons de precipitació sobre aquestes mateixes zones. També s’ha observant un moviment cap al nord de la zona d’interconvergència tropical i pot ser degut a l’anòmal gradient trobat a la zona equatorial en les temperatures superficial de l’Oceà. Tot i així per a una definitiva discussió i conclusions sobre els resultats dels experiments, seria necessari un estudi més ampli i profund.

Polyunsaturated aldehydes from large phytoplankton of the Atlantic Ocean Surface (42ºN to 33ºS)

Polyunsaturated aldehydes (PUAs) are organic compounds mainly produced by diatoms, after cell wounding. These compounds are increasingly reported as teratogenic for species of grazers and deleterious for phytoplanktonic species, but there is still scarce information regarding concentration ranges and the composition of PUAs in the open ocean. In this study, we analyzed the spatial distribution and the type of aldehydes produced by the large-sized (>10 μm) phytoplankton in the Atlantic Ocean surface. Analyses were conducted on PUAs released after mechanical disruption of the phytoplankton cells, referred to here as potential PUAs (pPUAs). Results show the ubiquitous presence of pPUA in the open ocean, including upwelling areas, as well as oligotrophic gyres. Total pPUA concentrations ranged from zero to 4.18 pmol from cells in 1 L. Identified PUAs were heptadienal, octadienal and decadienal, with heptadienal being the most common (79% of total stations). PUA amount and composition across the Atlantic Ocean was mainly related to the nitrogen:phosphorus ratio, suggesting nutrient-driven mechanisms of PUA production. Extending the range of trophic conditions considered by adding data reported for productive coastal waters, we found a pattern of PUA variation in relation to trophic status.