Occurrence of the toxic dinoflagellate Alexandrium ostenfeldii in the coastal waters of the southeastern Bay of Biscay
Luis
Ferrer1*,
Marta
Revilla1,
Aitor
Laza-Martínez2,
Yolanda
Sagarminaga1,
Almudena
Fontán1,
Joana
Larreta1,
Izaskun
Zorita1,
Oihana
Solaun1,
José Germán
Rodríguez1,
Leire
Arantzamendi1,
Manuel
González1 and
Andrea
Del Campo1
-
1
Marine Research Division, Centro tecnológico experto en innovación marina y alimentaria (AZTI), Spain
-
2
University of the Basque Country, Spain
Marine phytoplankton, as primary producers, contribute to the sustenance of bivalve aquaculture. However, some phytoplankton species can synthetize potent toxins, which are ingested by filter-feeding organisms and pose a threat to human health. These toxic species can also cause serious impacts to marine environment and economic activities at coastal sites. In temperate areas, phytoplankton abundance and composition show large spatio-temporal fluctuations that involve seasonal cycles, species succession and sporadic blooms. This variability is controlled by both top-down factors (e.g., grazing) and bottom-up factors (e.g., nutrients and light availability), being all of them ultimately driven by oceanic and meteorological processes, and anthropogenic pressure on coastal zones. Among those phytoplankton organisms, some species of the genus Alexandrium produce paralytic shellfish poisoning (PSP) toxins.
It is known that the responses to the environment differ among toxic phytoplankton taxa, even within the same genus. Here we address how physical drivers and bottom-up factors control toxic microalgae in the coastal waters of the southeastern Bay of Biscay. In these waters, a recent development of bivalve aquaculture at a pilot plant (called “Mendexa”) has led to monitor phytoplankton, toxins and hydrographic variables since 2014. Mendexa is located 2 km off the coast of the Basque Country (northern Spain), at a depth of approximately 45 m (Figure 1). The Basque coast is influenced by 12 short rivers with big slopes, which are torrential in character and provide, annually, 150 cubic metres per second of freshwater. This freshwater supply alters the physico-chemical composition of the shallow waters and often leads to an increase of nutrient concentration in the inner shelf waters (Valencia et al., 2004). The pilot plant uses a longline system for the culture of mussels (Mytilus galloprovincialis Lmk.) and occupies a total area of 1 ha. For more detailed information, the reader is referred to Azpeitia et al. (2016) and Muñiz et al. (2019).
At Mendexa, toxins are analysed monthly in the mussels collected in the upper metres of the water column. When any toxin exceeds the regulatory limit, samples are taken at a higher frequency (twice a month). According to the European legislation, the toxins analysed are the following: domoic acid, saxitoxins and lipophilic toxins (i.e., okadaic acid, dinophysistoxins, pectenotoxins, azaspiracids and yessotoxins). Saxitoxins, which are PSP toxins, are analysed by means of the mouse bioassay. For phytoplankton, the hose sampling method and a plankton net (20 µm) are used to take integrated samples through the water column, as dinoflagellates can present heterogenous vertical distribution. These samples are fixed with acidic Lugol’s solution and analysed following the Utermöhl sedimentation method. Occasionally, the identification of dinoflagellates is carried out using fluorescence microscopy, after staining with calcofluor. The physico-chemical conditions are characterized using a CTD (Conductivity, Temperature and Depth sensors). Also, several water samples are collected to quantify dissolved inorganic nutrients by colorimetric methods.
Specifically, here we study the events of high PSP toxin concentration in mussels (growing on longlines offshore) which occurred in autumn 2018, when the only PSP producer that could be found was Alexandrium ostenfeldii (Paulsen) Balech & Tangen. Previously, Alexandrium spp. had been reported along the Basque coast (e.g., Aylagas et al., 2014). In order to assess the influence of both local and regional processes on these events, meteorological and hydrographic variables together with satellite chlorophyll-a data were used. Also, particle tracking models and machine learning techniques were considered. Our hypothesis is that the occurrence of the dinoflagellate A. ostenfeldii and the high PSP toxin concentration were caused by the meteorological and oceanic conditions existing in autumn 2018. The month of September was characterized by warm and very dry conditions. In contrast, October was very rainy (i.e., high river runoff), which raised the concentration of inorganic nitrogen in the surface waters of the southeastern Bay of Biscay at mid-autumn. This together with stable atmospheric and oceanic conditions triggered the PSP toxins to exceed the regulatory limit in November and December, coinciding with the presence of 80 cells per litre of A. ostenfeldii (Figure 2). We anticipate our results to be a starting point for the development of predictive models that will play a useful role in the study of the evolution of Harmful Algal Blooms (HABs) in the southeastern Bay of Biscay.
Acknowledgements
This research was supported by the Basque Government and the European Union (INTERREG Atlantic Area Programme, grant agreement no. EAPA_182/2016).
References
Aylagas, E., Menchaca, I., Laza-Martínez, A., Seoane, S., and Franco, J. (2014). Evaluation of marine phytoplankton toxicity by application of marine invertebrate bioassays. Sci. Mar. 78(2), 173−183. doi: 10.3989/scimar.03957.26C || Azpeitia, K., Ferrer, L., Revilla, M., Pagaldai, J., and Mendiola, D. (2016). Growth, biochemical profile, and fatty acid composition of mussel (Mytilus galloprovincialis Lmk.) cultured in the open ocean of the Bay of Biscay (northern Spain). Aquaculture 454, 95−108. doi: 10.1016/j.aquaculture.2015.12.022 || Muñiz, O., Revilla, M., Rodríguez, J. G., Laza-Martínez, A., and Fontán, A. (2019). Annual cycle of phytoplankton community through the water column: Study applied to the implementation of bivalve offshore aquaculture in the southeastern Bay of Biscay. Oceanologia 61(1), 114−130. doi: 10.1016/j.oceano.2018.08.001 || Valencia, V., Franco, J., Borja, Á., and Fontán, A. (2004). “Hydrography of the southeastern Bay of Biscay”, in Oceanography and Marine Environment of the Basque Country, eds Á. Borja and M. Collins (Amsterdam: Elsevier), 159−194.
Keywords:
Alexandrium ostenfeldii,
Dinoflagellate,
HABs,
Phytoplankton,
toxic
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Oral Presentation
Topic:
Ecology, Biodiversity and Vulnerable Ecosystems
Citation:
Ferrer
L,
Revilla
M,
Laza-Martínez
A,
Sagarminaga
Y,
Fontán
A,
Larreta
J,
Zorita
I,
Solaun
O,
Rodríguez
J,
Arantzamendi
L,
González
M and
Del Campo
A
(2019). Occurrence of the toxic dinoflagellate Alexandrium ostenfeldii in the coastal waters of the southeastern Bay of Biscay.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00023
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Received:
19 Jun 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Dr. Luis Ferrer, Marine Research Division, Centro tecnológico experto en innovación marina y alimentaria (AZTI), Pasaia, Spain, lferrer@azti.es