ALBERT

Description: At each study station, surface water temperature (±0.2°C) and salinity (±0.06) were measured in situ by triplicate readings with a multiparameter probe (Horiba U-10, Japan). Using Niskin bottles, surface water samples were collected for quantification of plankton and estimations of chlorophyll a. For the former, 250 ml were fixed with Lugol's solution (1% final concentration) and kept in the dark until analysis under the microscope, while for chlorophyll a, a volume of 200–250 mL was filtrated onboard through filter GF/C and kept at -20°C.

Description: Alexandrium ostenfeldii ist ein wichtiger Vertreter mariner planktischer Dinoflagellaten. Von dieser Art ist bekannt, dass sie in der Lage ist, drei verschiedene Arten von Algentoxinen zu produzieren. Dabei handelt es sich um Paralytic Shellfish Toxins (PST) (vgl. Kapitel 5.2), Spirolide (vgl. Kapitel 5.3.1) und die strukturell verwandten Gymnodimine (vgl. Kapitel 5.3.2). Die Toxinprofile unterschiedlicher Populationen unterscheiden sich je nach geographischer Region in Zusammensetzung und produzierter Menge der Toxine. PST sind sehr gut untersucht, da sie potente Neurotoxine sind und mehrfach Vergiftungen beim Menschen verursacht haben, von denen einige zu Todesfällen geführt haben. Diese Dinoflagellaten treten normalerweise in geringen Konzentrationen zusammen mit anderen dominanten Spezies auf und haben deswegen bisher eine geringe Bedrohung für Aquakulturen oder Ähnliches dargestellt. In den letzten Jahren wurden vermehrt dichte monospezifische Blüten von A. ostenfeldii beobachtet. Diese treten hauptsächlich in Brackwassersystemen mit geringeren Salinitäten als im offenen Ozean auf. Dies ist ein Grund, warum bisher relativ wenig über die von A. ostenfeldii produzierten Toxine und deren Zusammenhänge untereinander bekannt ist und in den letzten Jahren vermehrt Forschungsinteresse aufgekommen ist. Dabei gibt es erste Hinweise, dass die Toxinvariabilität weit größer ist als bisher bekannt. Die Ursache für das Vorkommen variabler Toxinprofile und ob eine Korrelation zwischen den drei Toxingruppen besteht, ist unklar. Es gibt Stämme, die lediglich eine Toxinart produzieren und wiederum Stämme welche alle drei Arten produzieren. Die dieser Arbeit zugrunde liegende Hypothese besagt, dass A. ostenfeldii Kulturen in Brackwassersystemen mit geringeren Salinitäten als im offenen Ozean ein komplexeres Toxinprofil mit Toxinen aller drei Toxingruppen ausbilden. Kulturen aus marinen Bedingungen produzieren im Vergleich dazu nur Toxine einer Gruppe, der Spirolide. Zusätzlich soll eine weitere Hypothese überprüft werden, wonach ein Zusammenhang zwischen der Produktion von Gymnodiminen und PST besteht. In dieser Arbeit werden dazu die Toxinprofile verschiedener bisher nicht untersuchter Stämme aus Chile, Argentinien, Kanada, dem Limfjord (Dänemark), der Nordsee, dem Kattegat, Norwegen und den Niederlanden mittels Tandem-Massenspektrometrie und HPLC-FLD analysiert. Um weitere Informationen über das Toxinprofil zu erhalten, werden diese Stämme neben den bekannten Toxinen auf bisher unbekannte Toxine untersucht. Darüber hinaus sollen weitere Informationen über den Zusammenhang der unterschiedlichen Toxingruppen gewonnen werden und durch den Vergleich der Ergebnisse eventuelle Zusammenhänge in den Toxinprofilen aufgeklärt werden. Die durchgeführte Analyse ergab zwei bisher unbekannte Gymnodimine, sechs zusätzliche Spirolide sowie zehn weitere Verbindungen, bei denen es sich ebenfalls um Spirolide handelt, für die jedoch keine Struktur mit ausreichender Sicherheit erklärt werden konnte (vgl. Kapitel 8.1).

Description: The gulfs that surround Península Valdés (PV), Golfo Nuevo and Golfo San José in Argentina, are important calving grounds for the southern right whale Eubalaena australis. However, high calf mortality events in recent years could be associated with phycotoxin exposure. The present study evaluated the transfer of domoic acid (DA) from Pseudo-nitzschia spp., potential producers of DA, to living and dead right whales via zooplanktonic vectors, while the whales are on their calving ground at PV. Phytoplankton and mesozooplankton (primary prey of the right whales at PV and potential grazers of Pseudo-nitzschia cells) were collected during the 2015 whale season and analyzed for species composition and abundance. DA was measured in plankton and fecal whale samples (collected during whale seasons 2013, 2014 and 2015) using liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). The genus Pseudo-nitzschia was present in both gulfs with abundances ranging from 4.4 x 102 and 4.56 x 105 cell l -1. Pseudo-nitzschia australis had the highest abundance with up to 4.56 x 105 cell l-1. DA in phytoplankton was generally low, with the exception of samples collected during a P. australis bloom. No clear correlation was found between DA in phytoplankton and mesozooplankton samples. The predominance of copepods in mesozooplankton samples indicates that they were the primary vector for the transfer of DA from Pseudo-nitzschia spp. to higher trophic levels. High levels of DA were detected in four whale fecal samples (ranging from 0.30 to 710 mg g-1 dry weight of fecal sample or from 0.05 and 113.6 mg g-1 wet weight assuming a mean water content of 84%). The maximum level of DA detected in fecal samples (710 mg DA g-1 dry weight of fecal sample) is the highest reported in southern right whales to date. The current findings demonstrate for the first time that southern right whales, E. australis, are exposed to DA via copepods as vectors during their calving season in the gulfs of PV.

Description: The extensive Argentine continental shelf supports high plankton productivity and fish catches. In particular, El Rincón coastal area and the adjacent shelf fronts (38.5–42º S, 58.5–62º W) comprise diverse habitats and hold species of economic and ecological value. So far, studies of the microbial community at the base of the food web remain scarce. Here we describe the early spring plankton (〉5-200 µm) structure in terms of abundance, biomass, species composition, functional groups and phycotoxin profiles in surface waters of El Rincón in September 2015. Diatoms were the most abundant and the largest contributors to carbon biomass at most stations. They dominated in coastal and inner-shelf (depths 〈50 m) while dinoflagellates and small flagellates (〈15 µm) dominated offshore at middle-shelf waters (depth ~100 m). Likewise, large (〉20 µm) heterotrophic protists, e.g. various ciliates and dinoflagellates species were more abundant offshore. Scanning of phycotoxins in the field disclosed that paralytic shellfish poisoning (PSP) toxins were dominated by gonyautoxins-1/4 (GTX1/4). Lipophilic toxins were detected in low abundance, e.g. domoic acid (DA), although a bloom of Pseudo-nitzschia spp. (up to 3.6 x 105 cells L-1) was detected at inner-shelf stations. Pectenotoxin-2 (PTX-2) and 13-desmethyl spirolide C (SPX-1) were the most abundant in the field. PTX-2 co-occurred with Dinophysis spp., mainly D. tripos, while SPX-1 dominated at middle-shelf stations, where cells of Alexandrium catenella (1 strain) and A. ostenfeldii (3 strains) were isolated. The quantitative PSP profiles of the Alexandrium strains differed significantly from the field profiles. Moreover, the three A. ostenfeldii strains proved to be PSP producers and additionally produced 5 novel spirolides. Phylogenetic analyses of these first strains from the South Atlantic disclosed a new ribotype group suggesting a biogeographical distinction of the population. The plankton survey presented here contributes with baseline knowledge to evaluate potential ecosystem changes and to track the global distribution of toxigenic species.

Description: In the Northern Patagonian gulfs of Argentina (Golfo Nuevo and Golfo San José), blooms of toxigenic microalgae and the detection of their associated phycotoxins are recurrent phenomena. The present study evaluated the transfer of phycotoxins from toxigenic microalgae to mesozooplankton in Golfo Nuevo and Golfo San José throughout an annual cycle (December 2014–2015 and January 2015–2016, respectively). In addition, solid-phase adsorption toxin tracking (SPATT) samplers were deployed for the first time in these gulfs, to estimate the occurrence of phycotoxins in the seawater between the phytoplankton samplings. Domoic acid was present throughout the annual cycle in SPATT samplers, whereas no paralytic shellfish poisoning toxins were detected. Ten toxigenic species were identified: Alexandrium catenella, Dinophysis acuminata, Dinophysis acuta, Dinophysis tripos, Dinophysis caudata, Prorocentrum lima, Pseudo-nitzschia australis, Pseudo-nitzschia calliantha, Pseudo-nitzschia fraudulenta, and Pseudo-nitzschia pungens. Lipophilic and hydrophilic toxins were detected in phytoplankton and mesozooplankton from both gulfs. Pseudo-nitzschia spp. were the toxigenic species most frequent in these gulfs. Consequently, domoic acid was the phycotoxin most abundantly detected and transferred to upper trophic levels. Spirolides were detected in phytoplankton and mesozooplankton for the first time in the study area. Likewise, dinophysistoxins were found in mesozooplankton from both gulfs, and this is the first report of the presence of these phycotoxins in zooplankton from the Argentine Sea. The dominance of calanoid copepods indicates that they were the primary vector of phycotoxins in the pelagic trophic web.