Papers by Gotzon Basterretxea
Deep Sea Research Part II: Topical Studies in Oceanography, 2010
The life cycle of the toxic dinoflagellate Alexandrium minutum consists of an asexual stage, char... more The life cycle of the toxic dinoflagellate Alexandrium minutum consists of an asexual stage, characterized by motile vegetative cells, and a sexual stage, a resting cyst that once formed remains dormant in the sediment. Insight into the factors that determine the distribution and abundance of resting cysts is essential to understanding the dynamics of the vegetative phase. In investigations carried out between harbor (northwestern Mediterranean Sea), the spatial and temporal distribution patterns of A. minutum resting cysts and of the sediments were studied during different bloom stages of the vegetative population. Maximum cyst abundance was recorded mainly in the innermost part of the harbor while the lowest abundance always occurred near the harbor entrance, consistent with the distribution of silt-clay sediment fractions. The tendency of cysts in sediments to increase after bloom periods was clearly associated with new cyst formation, while cyst abundance decreased during non-bloom periods. Exceptions to this trend were observed in stations dominated by the deposition of coarse sediments. High correlation between the presence of cysts and clays during non-bloom periods indicates that cysts behave as passive sediment particles and are influenced by the same hydrodynamic processes as clays. In Arenys de Mar, the main physical forcing affecting sediment resuspension is the seiche, which was studied using in situ measurements and numerical models to interpret the observed distribution patterns. During non-bloom periods, cyst losses were smaller when the seiche was more active and at the station where the seiche-induced current was larger. Thus, seiche-forced resuspension appears to reduce cyst losses by reallocating cysts back to the sediment surface such that their burial in the sediment is avoided. The observed vertical profiles of the cysts were consistent with this process.
Continental Shelf Research, 2008
The variability of suspended sediments in a Mediterranean harbour was studied using high-frequenc... more The variability of suspended sediments in a Mediterranean harbour was studied using high-frequency moored instruments. Data analysis revealed that the fundamental mode of oscillation or seiche is the main contribution to the sea level variability and currents. Yet a direct relation between the seiche and suspended sediment was not clear. To study the sediment dynamics, a coupled hydrodynamicsediment one-dimensional vertical model for sand and non-cohesive mud was implemented. Results showed good agreement between most of the observed and simulated resuspension events. Indeed, the vertical extension and the duration of these events were satisfactorily simulated for mud class. Model simulations were used to determine the time delay between suspended sediment and currents, which improved the correlation between the seiche and suspended sediment to some degree. Scarce events of sediment advection from outside waters and fresh water discharges from land-based sources were identified. It is suggested that phytoplankton species detected in the harbour were responsible for discrepancies between observations and simulations. r
Estuarine, Coastal and Shelf Science, 2005
A study of Santa Ponc¸a Bay (Balearic Islands) was conducted during summer 2002 to understand fur... more A study of Santa Ponc¸a Bay (Balearic Islands) was conducted during summer 2002 to understand further the processes controlling recurrent Alexandrium taylori blooms near the beach. These massive algal proliferations (10 6 cells L ÿ1 ) have become common in many anthropized pocket beaches of the Mediterranean during the summer season. Nearshore dissolved inorganic nutrient concentrations (DIN) are generally high near the shoreline (avg. DIN at 1.6 mM), yet this factor alone is insufficient to explain harmful algal bloom (HAB) occurrences at some beaches and their absence in others. It is postulated that summer conditions, and particularly, the mild breeze conditions are key factors into understanding these nearshore blooms. The advantages of this coastal environment for a migrating dinoflagellate such as A. taylori are discussed. Resilience to undergo enhanced turbulence episodes, motility, day/night migration and a favorable current regime that produces shoreward transport at sea surface are regarded as concurrent mechanisms that lead to HAB generation and maintenance.
Page 1. Proyectos de investigación en parques nacionales: 2007-2010 33 CARACTERIZACIÓN BIOGEOQUÍM... more Page 1. Proyectos de investigación en parques nacionales: 2007-2010 33 CARACTERIZACIÓN BIOGEOQUÍMICA DEL LITORAL DEL ARCHIPIÉLAGO DE CABRERA ANTONIO TOVAR-SÁNCHEZ1, GOTZON BASTERRETXEA2 ...
Progress in Oceanography, 2005
Currents, particle fluxes and ecology were studied in the Palamó s submarine canyon (also known a... more Currents, particle fluxes and ecology were studied in the Palamó s submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE-SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow.
... DE CABRERA GOTZON BASTERRETXEA1, ANA SABATÉS2, ANTONI JORDI1, IGNACIO A. CATALÁN1, ITZIAR ÁLV... more ... DE CABRERA GOTZON BASTERRETXEA1, ANA SABATÉS2, ANTONI JORDI1, IGNACIO A. CATALÁN1, ITZIAR ÁLVAREZ1, MIQUEL PALMER1Y BEATRIZ MORALES-NIN1 ... «Transporte y acumulación de larvas de peces en el PN del Archipiélago de Cabrera» 344 ...
Page 1. PHYTOPLANKTON PRIMARY PRODUCTION AND RESPIRATION BALANCE lN THE ÜP WEL LiNG-CÁNÁR Y CÜAST... more Page 1. PHYTOPLANKTON PRIMARY PRODUCTION AND RESPIRATION BALANCE lN THE ÜP WEL LiNG-CÁNÁR Y CÜASTA L TRANS/T/ON ZONE REGION Oral J. Aristepi(2), ED Ratm(!), P. T"(2), G. Eastemetxec;(!), MF ...
This study presents a comparison of the results for two conceptually different primary production... more This study presents a comparison of the results for two conceptually different primary production models applied to the Bransfield Strait during austral summer. The first model is based on light availability and the performance of photosynthesis-irradiance (PI) curves. Production values obtained with this first model are very similar to in situ incubations (rL0.79). The second model estimates primary production from absorbed light spectra and quantum yield (), allowing estimations of carbon fixation rates with no need of incubations. Production rates obtained by this second method show a close relationship to those obtained from the previous model, although data are slightly overestimated (0.1 gC m.' d '). The result of applying both models to different areas of the Bransfield Strait, divided by their physical and biological characteristics, leads to a general distribution of primary production in the area in which higher values (>2 gC m' d ') are found in the western region of the Strait.
Scientia Marina
This paper shows observational evidence of internal wave generation and mixing in the southwest s... more This paper shows observational evidence of internal wave generation and mixing in the southwest shelf-break region of Gran Canaria Island. Signals of periodic internal motion and related mixing events were detected through large pycnocline variations and subcritical gradient Richardson events. Broad areas of homogeneous dense water over the slope, where the vertical temperature field displays a wave-like pattern, provide further evidences of internal wave mixing in this region. The observed diapycnal chlorophyll transport matches with mixing events, suggesting a periodic nutrient supply to the euphotic zone through internal wave mixing. We postulate that internal wave mixing may be an important mechanism contributing to the biological enhancement reported southwest of Gran Canaria Island.
... Deep-Sea Res., 22: 251-263. Prinsenberg SJ. WL Wilmot and M. Ramay. - 1974. ... 1991. Barotro... more ... Deep-Sea Res., 22: 251-263. Prinsenberg SJ. WL Wilmot and M. Ramay. - 1974. ... 1991. Barotropic and baroclúiic tidai cur-rents in the eastern basins of the North Atlantic. J. Geophy. Res., 96: 22,259-22.27 1. CHLOROPHYLL INCREASE DUE TO Ih'TERNAL WAVES 97
Journal of Geophysical Research Atmospheres
Continental shelf waters have limited capacity to store absorbed and river-discharge carbon and a... more Continental shelf waters have limited capacity to store absorbed and river-discharge carbon and associated biogenic elements. Consequently, all but a small fraction of these received elements must either be exported to the open sea or buried in sediments. As regards to its transport from the shelf to the open ocean, the presence of energetic fronts along many continental margins, which
In recent years there has been an increasing interest in the study of the interactions between di... more In recent years there has been an increasing interest in the study of the interactions between distant parts of the atmosphere and how local areas respond in front of global scale climatic patterns. Although these climatic patterns are usually concentrated in certain areas over the ocean, they generate slowly varying atmospheric perturbations that propagate away and produce large scale spatial
In this study we analyse the influence of environmental factors on settlement and recruitment of ... more In this study we analyse the influence of environmental factors on settlement and recruitment of Diplodus sargus in shallow rocky habitats of Minorca. We compare the variability in settlement and post-settler population dynamics in two areas, north and south, with different wind regimes and ocean dynamics. During 2012, settlement was measured by direct visual census of fish juveniles throughout the settlement and recruitment period (April-July) at three coves located in each area. The settlement pattern was similar at the three nearby coves but notable differences were observed among areas, which were attributed to differences in environmental forcing. A decline in settlement was observed in the north coves in response to a storm with winds exceeding 10 m/s, waves above 3 m and alongshore flow enhancement. We did not observe significant variations in post-settler growth between the two areas. Thus, population dynamics were mainly regulated by variations in juvenile mortality. Mortal...
Journal of Plankton Research, 2015
ABSTRACT The size structure of phytoplankton reveals relevant information on the structure and re... more ABSTRACT The size structure of phytoplankton reveals relevant information on the structure and response of aquatic systems to environmental drivers. To estimate the phytoplankton size distribution, we combined simultaneous particle size measurements obtained with a laser in situ scattering and transmissometry instrument (LISST) and fluorescence profiles using canonical correlation analysis (CCA). We tested the performance of this method with a series of synthetic laboratory samples generated by mixing cultured phytoplankton cells and natural sediments with grain sizes within the size range of phytoplankton. Our results revealed that the method yields reliable estimation of the algal fraction allowing the discrimination of phytoplankton size distribution when algal cells constitute >25% of total suspended particulate matter. Uncertainties arise in very turbid waters and when samples are composed of two phytoplankton species with very different contribution to chlorophyll in terms of cell size. Application of the proposed method in a survey of 37 stations carried out in Palma Bay (Mediterranean Sea) effectively represented the patterns of four main size fractions dominating coastal phytoplankton biomass, demonstrating the utility of the method. Compared to previous published methods, the proposed method is more robust because it is not impeded by the presence of non-algal components.
Remote Sensing of Biomass - Principles and Applications, 2012
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Papers by Gotzon Basterretxea