Percorrer por autor "Fraile, Igaratza"
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- Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North AtlanticPublication . Rebotim, Andreia; Voelker, Antje; Jonkers, Lukas; Waniek, Joanna J.; Meggers, Helge; Schiebel, Ralf; Fraile, Igaratza; Schulz, Michael; Kucera, MichalPlanktonic foraminifera preserved in marine sediments archive the physical and chemical conditions under which they built their shells. To interpret the paleoceano-graphic information contained in fossil foraminifera, the recorded proxy signals have to be attributed to the habitat and life cycle characteristics of individual species. Much of our knowledge on habitat depth is based on indirect methods, which reconstruct the depth at which the largest portion of the shell has been calcified. However, habitat depth can be best studied by direct observations in stratified plankton nets. Here we present a synthesis of living planktonic foraminifera abundance data in vertically resolved plankton net hauls taken in the eastern North Atlantic during 12 oceanographic campaigns between 1995 and 2012. Live (cytoplasm-bearing) specimens were counted for each depth interval and the vertical habitat at each station was expressed as average living depth (ALD). This allows us to differentiate species showing an ALD consistently in the upper 100m (e.g., Globigerinoides ruber white and pink), indicating a shallow habitat; species occurring from the surface to the subsurface (e.g., Globigerina bulloides, Globorotalia inflata, Globorotalia truncatulinoides); and species inhabiting the subsurface (e.g., Globorotalia scitula and Globorotalia hirsuta). For 17 species with variable ALD, we assessed whether their depth habitat at a given station could be predicted by mixed layer (ML) depth, temperature in the ML and chlorophyll a concentration in the ML. The influence of seasonal and lunar cycle on the depth habitat was also tested using periodic regression. In 11 out of the 17 tested species, ALD variation appears to have a predictable component. All of the tested parameters were significant in at least one case, with both seasonal and lunar cyclicity as well as the environmental parameters explaining up to >50% of the variance. Thus, G. truncatulinoides, G. hirsuta and G. scitula appear to descend in the water column towards the summer, whereas populations of Trilobatus sacculifer appear to descend in the water column towards the new moon. In all other species, properties of the mixed layer explained more of the observed variance than the periodic models. Chlorophyll a concentration seems least important for ALD, whilst shoaling of the habitat with deepening of the ML is observed most frequently. We observe both shoaling and deepening of species habitat with increasing temperature. Further, we observe that temperature and seawater density at the depth of the ALD were not equally variable among the studied species, and their variability showed no consistent relationship with depth habitat. According to our results, depth habitat of individual species changes in response to different environmental and ontogenetic factors and consequently planktonic foraminifera exhibit not only species-specific mean habitat depths but also species-specific changes in habitat depth.
- Natural geochemical markers reveal environmental history and population connectivity of common cuttlefish in the Atlantic Ocean and Mediterranean SeaPublication . Rooker, Jay R.; Wells, R. J. David; Addis, Piero; Arrizabalaga, Haritz; Baptista, Miguel; Bearzi, Giovanni; Dance, Michael A.; Fraile, Igaratza; Lacoue-Labarthe, Thomas; Lee, Jessica M.; Megalofonou, Persefoni; Rosa, Rui; Sobrino, Ignacio; Sykes, António; Villanueva, RogerNatural markers (delta C-13 and delta O-18 stable isotopes) in the cuttlebones of the European common cuttlefish (Sepia officinalis) were determined for individuals collected across a substantial portion of their range in the Northeast Atlantic Ocean (NEAO) and Mediterranean Sea. Cuttlebone delta C-13 and delta O-18 were quantified for core and edge material to characterize geochemical signatures associated with early (juvenile) and recent (sub-adult/adult) life-history periods, respectively. Regional shifts in cuttlebone delta C-13 and delta O-18 values were detected across the 12 sites investigated. Individuals collected from sites in the NEAO displayed more enriched delta C-13 and delta O-18 values relative to sites in the Mediterranean Sea, with the latter also showing salient differences in both markers among western, central and eastern collection areas. Classification success based on cuttlebone delta C-13 and delta O-18 values to four geographical regions (NEAO, western, central and eastern Mediterranean Sea) was relatively high, suggesting that environmental conditions in each region were distinct and produced area-specific geochemical signatures on the cuttlebones ofS. officinalis. A modified delta C-13 and delta O-18 baseline was developed from sites proximal to the Strait of Gibraltar in both the NEAO and Mediterranean Sea to assess potential mixing through this corridor. Nearly, all (95%) of delta C-13 and delta O-18 signatures ofS. officinaliscollected in the area of the NEAO closest to the Strait of Gibraltar (Gulf of Cadiz) matched the signatures of specimens collected in the western Mediterranean, signifying potential movement and mixing of individuals through this passageway. This study extends the current application of these geochemical markers for assessing the natal origin and population connectivity of this species and potentially other taxa that inhabit this geographical area.
- Regional patterns of δ13C and δ15N for European common cuttlefish (Sepia officinalis) throughout the Northeast Atlantic Ocean and Mediterranean SeaPublication . David Wells, R. J.; Rooker, Jay R.; Addis, Piero; Arrizabalaga, Haritz; Baptista, Miguel; Bearzi, Giovanni; Fraile, Igaratza; Lacoue-Labarthe, Thomas; Meese, Emily N.; Megalofonou, Persefoni; Rosa, Rui; Sobrino, Ignacio; Sykes, Antonio V.; Villanueva, RogerThe European common cuttlefish, Sepia officinalis Linnaeus, 1758 is a coastal nektobenthic species ranging from the Shetland Islands through the Northeast Atlantic Ocean and Northwest Africa into the Mediterranean Sea [1]. This species constitutes one of the most economically valuable cephalopod resources in the Northeast Atlantic Ocean, supporting an important fishery resource [2,3]. Sepia officinalis has a relatively short lifespan of 1–2 years, early sexual maturity and an extended spawning season laying eggs on the seafloor with direct benthic, large hatchlings [4,5]. Given this species geographical distribution combined with limited dispersal, it has been a targeted model species to examine connectivity throughout the Northeast Atlantic Ocean and Mediterranean Sea (hereafter NEAO-MS) [6]. Natural biomarkers such as stable isotopes are commonly used to examine food web structure and ecosystem connectivity in marine environments [7,8]. Stable isotopes of carbon (δ13C) and nitrogen (δ15N) are particularly useful tracers due to their natural abundance being influenced by the environment and ease of measurement in body tissues without having to track individuals in a population. δ13C is traditionally used to trace carbon pathways because little fractionation occurs between predator and prey, and different primary producers (energy sources) often have unique δ13C values [9]. δ13C values of consumers are a product of the primary producers’ composition and influenced by the dissolved inorganic carbon (DIC) pool, as well as local abiotic factors including sea surface temperature, and can differ across ocean basins [10] and region-specific freshwater to marine gradients [9]. δ15N becomes enriched with increasing trophic level and is used to infer trophic position [7], but can also differ at the base of the food web. Depending upon the types of nutrients available to stimulate growth, δ15N values can be used to track energy flow in high-nutrient (nitrate) and low-nutrient (N2 fixation) ecosystems as well as new nitrogen (upwelled nitrate) versus regenerated nitrogen (ammonia, urea). Combining both δ13C and δ15N offers the potential to study the connectivity and population structure of species because longitudinal and latitudinal gradients exist throughout marine ecosystems [11,12], including the NEAO-MS [8,13].