Microplancton tóxico y nocivo en las Rías Gallegas en los años 2003 a 2006

[ESP] El dinoflagelado productor de toxinas paralizantes (PSP), Gymnodinium catenatum, desarrolló un intenso episodio tóxico en el año 2005, después de diez años de casi total ausencia en las aguas de la costa de Galicia. Este episodio se asoció con procesos de surgencia negativa (downwelling) y su inicio, con una corriente costera superficial, hacia el norte (0,2-0,6 m.s-1) paralela a la costa de Portugal. En 2006 se produjo una réplica con menores concentraciones celulares. El también productor de PSP, Alexandrium minutum, presentó proliferaciones en verano, en puntos geográficos muy concretos (Estuario de Baiona y Ría de Ares), relacionadas con estratificación halina y con resuspensión de quistes locales. El dinoflagelado responsable de la mayor parte de los cierres en los polígonos de producción de mejillón de las Rías, por toxinas lipofílicas, Dinophysis acuminata, presentó estos años dos floraciones, una en primavera debida sobre todo, a crecimiento in situ y otra en otoño, en la que además hubo advección desde la parte externa de las Rías, a través del nivel de superficie, excepto en el año 2006 en el que sólo proliferó en otoño. Dinophysis acuta proliferó cada año, en Octubre. El inicio de sus episodios tóxicos coincide con surgencia negativa. Las proliferaciones de diatomeas Pseudo-nitzschia spp., asociadas con acumulación de ácido domoico en mejillón cultivado en batea, se detectaron en momentos muy puntuales, máximo de una o dos semanas en los meses de Abril o Mayo (2004 y 2005) y Septiembre (2004 y 2006). Se pudieron observar a simple vista en las rías gallegas, mareas rojas de Lingulodinium polyedra en la Ría de Ares-Betanzos en 2003, asociadas con la detección de yesotoxinas, roja también fue la que se observó en la zona interna de Muros en 2005, por Myrionecta rubra y roja anaranjada la de Noctilluca scintillans en Pontevedra, Muros, Arousa y Baldaio en 2006. Se identificaron, por primera vez en la zona dos organismos, el dinoflagelado Takayama helix, que es muy posible que haya sido mal identificado en la zona, como Gyrodinium pulchellum y la cianobacteria productora de microcistinas, Microcystis botrys, que pudo haber sido malidentificada como M. aeruginosa y que produjo una marea verde, casi monoespecífica, en un área próxima a la desembocadura del río Umia, en Septiembre de 2006, cuando se tuvo que hacer un cierre de las zonas de producción de moluscos para protegerlos de un vertido químico tras el incendio de la planta química Brenntag.A Celia Díaz y Fernanda Franco por la asistencia técnica, a F. Amoedo, P. García, I. Lemos y S. Roura en especial por los recuentos celulares, a Ó. Torrado por los muestreos en Ares. A J. M. Cabanas y J. Triñanes por los datos del índice de afloramiento y de drifters, a N. Lundholm y S. Méndez, por su ayuda con la microscopía electrónica, a Ángeles Longa por la fotografía de la marea roja de Noctiluca scintillans, a J. Mouriño por la gestión de la base de datos, a L. Abal y A. Gómez por su ayuda con las gráficas, a la tripulación y a A.Castro y Romero, patrones de los B/O J.Naváz y Lura. A B. Reguera y T. Moita por las puestas en común sobre la ecología de Dinophysis spp. y G. catenatum, respectivamente. A Carmelo Thomas y Marli Bergesch por la confirmación de la identificación de T. helix y M. botris respectivamente. A J. Gilabert por su ayuda. Este trabajo fue financiado en su totalidad por la Consellería de Pesca y Asuntos Marítimos de la Xunta de Galicia

PSP detoxification kinetics in the mussel Mytilus galloprovincialis. One- and two-compartment models and the effect of some environmental variables

Paralytic shellfish poisoning (PSP) toxins are accumulated by bivalves during toxic plankton blooms. In these bivalves the toxins are distributed into different body tissues which have varying affinities for them, and later these toxins are transferred by the bivalves to other trophic levels. After the disappearance of the toxic cells, shellfish remain toxic for a variable period of time, depending on the detoxification kinetics. We studied these kinetics in mussels Mytilus galloprovincialis previously exposed to a bloom of the PSP producing dinoflagellate Gymnodinium catenatum. The toxin profile observed in the mussels was very similar to that of G. catenatum, showing that toxin transformations (chemical or enzymatic) had little or no importance in this case. The detoxification rates at all the sampling points decreased progressively from ca 0.25 to 0 d-1 following an inverse hyperbolic-like curve. These rates were related to different degrees to the environmental factors studied (salinity, temperature, and light transmission as a measure of seston volume, and in vivo fluorescence as a measure of phytoplankton concentration) and to fresh body weight during each sampling period (estimated by multiple regression). In general, detoxification rates became increasingly independent of the variables cited as the experiment progressed. One- and 2-compartment detoxification models, both with 2 variants (with fixed and variable detoxification rates depending on the environmental variables and body weight), were used to describe the detoxification kinetics observed. Neither of the 2 variants of the 1-compartment models correctly described detoxification. The 2-compartment models, on the other hand, particularly the environmentally controlled variant, fit the observed detoxification kinetics very well. There was only a slight difference between these last 2 models, which would suggest that the actual effect of the environmental variables considered in the detoxification process is unimportant.Versión del editor2,483

Evaluation of passive samplers as a monitoring tool for early warning of Dinophysis toxins in shellfish

From June 2006 to January 2007 passive samplers (solid phase adsorbing toxin tracking, SPATT) were tested as a monitoring tool with weekly monitoring of phytoplankton and toxin content (liquid chromatography–mass spectrometry, LC-MS) in picked cells of Dinophysis and plankton concentrates. Successive blooms of Dinophysis acuminata, D. acuta and D. caudata in 2006 caused a long mussel harvesting closure (4.5 months) in the Galician Rías (NW Spain) and a record (up to 9246 ng·g resin-week−1) accumulation of toxins in SPATT discs. Best fit of a toxin accumulation model was between toxin accumulation in SPATT and the product of cell densities by a constant value, for each species of Dinophysis, of toxin content (average) in picked cells. Detection of Dinophysis populations provided earlier warning of oncoming diarrhetic shellfish poisoning (DSP) outbreaks than the SPATT, which at times overestimated the expected toxin levels in shellfish because: (i) SPATT accumulated toxins did not include biotransformation and depuration loss terms and (ii) accumulation of toxins not available to mussels continued for weeks after Dinophysis cells were undetectable and mussels were toxin-free. SPATT may be a valuable environmental monitoring and research tool for toxin dynamics, in particular in areas with no aquaculture, but does not provide a practical gain for early warning of DSP outbreaks

Algunos aspectos del flujo de agua a través de las bateas de mejillón

8 pages, 6 figures.[EN] All studies on particle retention by mussel rafts have assumed a laminar or nearly laminar water flow, directed from the front to the rear of the raft. We have studied such a flow in five rafts in the Ría de Arousa. Our results show that, in most cases, the current velocity at the centre of the raft is slower than at the rear. This situation can only be achieved by means of lateral inputs. The current velocity showed great variation with depth and the differences depended on raft and time. The current direction also varied with depth and, in some cases, all currents entered the rafts from the same side. These findings have two important repercussions: a) it is necessary to change the sampling strategy to measure the retention of suspended material and the environmental impact by rafts; and b) the structure of the rafts can be modified to optimize their adaptation to the water flow.[ES] Todos los estudios hasta el presente, de retención de partículas por las bateas de mejillón, han asumido que el flujo a través de ellas es laminar o cuasilaminar y va de proa a popa (con la batea orientada hacia la corriente). Hemos estudiado el flujo en cinco bateas de la ría de Arousa. Nuestros resultados muestran que, en la mayor parte de los casos, la velocidad de la corriente en el centro de la batea es menor que en la popa y esta situación únicamente puede suceder cuando existen en la popa entradas laterales de agua. La velocidad de la corriente mostró grandes variaciones con la profundidad y estas diferencias dependieron tanto de la batea como del tiempo. La dirección de la corriente también varió con la profundidad y, en algunos casos, la entrada de agua en la batea a todas las profundidades se produjo por el misino costado, indicando que la batea no estaba orientada al efecto integrado de las corrientes. Estos resultados tienen dos importantes repercusiones: es necesario cambiar la estrategia de muestreo para medir la retención de material en suspensión; y la estructura de las bateas puede ser modificada para optimizar su adaptación al flujo de agua.This paper was supported in part by the project "Recursos alimenticios, crecimiento y variabilidad fisiológica del mejillón (Mytilus galloprovincialis)en la ría de Arousa" funded by the Consellería de Pesca, Xunta de Galicia.Peer reviewe

Influence of upwelling and river runoff interaction on phytoplankton assemblages in a Middle Galician Ria and Comparison with northern and southern rias (NW Iberian Peninsula)

17 páginas, 4 tablas, 6 figurasThe first oceanographic research (hydrography, nutrient salts, chlorophyll, primary production and phytoplankton assemblages) in a Middle Galician Ria was carried out in Corme-Laxe during 2001, just a year before the Prestige oil spill, being the only reference to evaluate eventual changes in the phytoplankton community. Due to the small size of this ria (6.5 km2), oceanographic processes were driven by the continental water supplied by Anllons River during the wet season (20–30 m3 s−1 in winter), and the strong oceanic influence from the nearby shelf during the dry season. The annual cycle showed a spring bloom with high levels of chlorophyll (up to 14 μg Chl-a L−1) and primary production (3 g C m−2 d−1) and a summer upwelling bloom (up to 8 μg Chl-a L−1 and 10 g C m−2 d−1) where the proximity of the Galician upwelling core (<13.5 °C at sea surface) favors the input of upwelled seawater (up to 9 μM of nitrate and silicate) to the bottom ria layer, even during summer stratification events (primary production around 2 g C m−2 d−1). Thus, phytoplankton assemblages form a “continuum” from spring to autumn with a predominance of diatoms and overlapping species between consecutive periods; only in autumn dinoflagellates and flagellates characterized the phytoplankton community. In the Middle Rias as Corme-Laxe, the nutrient values, Chl-a, primary production and phytoplankton abundance for productive periods were higher than those reported for the Northern (Ria of A Coruña) and Southern Rias (Ria of Arousa) for year 2001; this suggests the importance of the hydrographic events occurring in the zone of maximum upwelling intensity of the Western Iberian Shelf, where a lack of annual cycles studies existsThis work is a contribution to the CICYT projects Hydrodynamic and hydrochemistry of the Anllons River-Laxe Ria system: seasonal stages (ref. HID99-0699) and Historical evolution of the anthropogenic influence in the Anllons Basin, Anllons Estuary and Laxe Ria (ref. REN2002-04629-C03). This paper is a contribution to the Spanish LOICZ ProgrammePeer reviewe

New life-cycle stages of Gymnodinium catenatum (Dinophyceae): laboratory and field observations

11 pages, 7 figures, 2 tablesThe chain-forming dinoflagellate Gymnodinium catenatum is responsible for outbreaks of paralytic shellfish poisoning (PSP); however, the relative importance of benthic-planktonic lifecycle transitions in the appearance of blooms of this species needs to be clarified. By coupling field and laboratory experiments, the present study is the first to analyze the dynamics of vegetative cells and sexual stages during a bloom of G. catenatum. In natural samples, the sexual stages of G. catenatum were associated with several different cellular behaviors and morphologies. This confirmed laboratory evidence for the reversibility of the species' sexual processes and for the ability of zygotes to either bypass or shorten the route to resting-cyst formation. Moreover chains of up to 4 viable cysts with differing morphologies occurred and these have never been reported previously for this species. At least two of the cysts had reticulated surfaces, a feature related to sexual reproduction in previous studies; this observation suggests the involvement of sexual processes in mechanisms that cannot be explained by any known life cycle route depicted for this species. Morphological variability and abundance of the sexual stages during the bloom indicated the complexity of the G. catenatum sexual cycle and the important role of sexual reproduction in the ecological succession of this species. However, the lack of a dormancy period in the sexual resting stage (evidenced by the large number of germinated cysts in sediments sampled 3 mo after the bloom) indicated that the advection of off-shore populations shoreward, rather than 'seed beds', is the main mechanism explaining G. catenatum bloom formation in the Galician rías. © Inter-Research 2008This study was funded by the EU Project SEED (GOCE-CT-2005-003875) and the Xunta de Galicia Monitoring Program. R.I.F. was supported by a postdoctoral I3P contract from the Spanish Ministry of Education and SciencePeer Reviewe

Yessotoxins in Mollusks of the Galician Coast from 2014 to 2022: Variability, Biotransformation, and Resistance to Alkaline Hydrolysis

The presence of yessotoxins (YTXs) was analyzed in 10,757 samples of Galician bivalves from 2014 to 2022. Only YTX and 45-OH YTX were found. YTX was detected in 31% of the samples, while 45-OH YTX was found in 11.6% of them. Among the samples containing YTX, 45-OH YTX was detected in 37.3% of cases. The maximum recorded levels were 1.4 and 0.16 mg of YTX-equivalentsg−1, for YTX and 45-OH YTX, respectively, which are well below the regulatory limit of the European Union. The YTX and 45-OH YTX toxicities in the raw extracts and extracts subjected to alkaline hydrolysis were strongly and linearly related. Due to the lack of homo-YTX in Galician samples, the effect of alkaline hydrolysis on homo-YTX and 45OH-Homo-YTX was only checked in 23 additional samples, observing no negative effect but a high correlation between raw and hydrolyzed extracts. Hydrolyzed samples can be used instead of raw ones to carry out YTXs determinations in monitoring systems, which may increase the efficiency of those systems where okadaic acid episodes are very frequent and therefore a higher number of hydrolyzed samples are routinely analyzed. The presence of YTX in the studied bivalves varied with the species, with mussels and cockles having the highest percentages of YTX-detected samples. The presence of 45-OH YTX was clearly related to YTX and was detected only in mussels and cockles. Wild populations of mussels contained proportionally more 45-OH YTX than those that were raft-cultured. Spatially, toxin toxicities varied across the sampling area, with higher levels in raft-cultured mussels except those of Ría de Arousa. Ría de Ares (ARE) was the most affected geographical area, although in other northern locations, lower toxin levels were detected. Seasonally, YTX and 45-OH YTX toxicities showed similar patterns, with higher levels in late summer and autumn but lower toxicities of the 45-OH toxin in August. The relationship between the two toxins also varied seasonally, in general with a minimum proportion of 45-OH YTX in July–August but with different maximum levels for raft-cultured and wild mussel populations. Interannually, the average toxicities of YTX decreased from 2014 to 2017 and newly increased from 2018 to 2021, but decreased slightly in 2022. The relationship between 45-OH YTX and YTX also varied over the years, but neither a clear trend nor a similar trend for wild and raft mussels was observed