[1] Carbon system parameters measured during several expeditions along the coast of Chile (23°S-56°S) have been used to show the main spatial and temporal trends of air-sea CO 2 fluxes in the coastal waters of the eastern South Pacific. Chilean coastal waters are characterized by strong pCO 2 gradients between the atmosphere and the surface water, with high spatial and temporal variability. On average, the direction of the carbon flux changes from CO 2 outgassing at the coastal upwelling region to CO 2 sequestering at the nonupwelling fjord region in Chilean Patagonia. Estimations of surface water pCO 2 along the Patagonian fjord region showed that, while minimum pCO 2 levels (strong CO 2 undersaturation) occurs during the spring and summer period, maximum levels (including CO 2 supersaturation) occur during the austral winter. CO 2 uptake in the Patagonia fjord region during spring-summer is within the order of −5 mol C m −2 yr −1 , indicating a significant regional sink of atmospheric CO 2 during that season. We suggest that the CO 2 sink at Patagonia most probably exceeds the CO 2 source exerted by the coastal upwelling system off central northern Chile.

Unialgal and mixed cultures of the toxic dinoflagellate Alexandrium minutum and the non-toxic dinoflagellate Prorocentrum micans were cultured under phosphate (P) limitation (<1 µM), in the presence or absence of the copepod Acartia clausi. The aim was to determine the possible effects of interspecific competition, predation and nutrient limitation on the production of Paralytic Shellfish Poisoning (PSP) toxin by A. minutum. The growth rate of A. minutum was higher in the cultures of A. minutum and copepods than in the mixed cultures of A. minutum and P. micans, which indicates that A. minutum was more negatively affected by interspecific competition than by predation. Toxin content per cell in A. minutum increased in all cultures, but toxin production rate was higher in cultures with P. micans and/or A. clausi. Toxin concentration in A. minutum increased as PO 4 3 -concentration diminished. In the mixed cultures with copepods, analyses of toxin content in the copepods showed that at cell toxin contents lower than approximately 20 fmol cell -1 , mainly cells of A. minutum were ingested by copepods, whereas at higher toxins content per cell, copepods fed mainly on P. micans. We conclude that one of the possible advantages of toxin production by A. minutum under P limitation is to enhance interspecific competition, by redirecting grazing pressure to non-toxic phytoplankton species. It would allow a possibly low competitive ability of A. minutum to be offset under low nutrient concentrations. KEY WORDS: Dinoflagellates · Phosphorus · Nutrients · Toxins · Copepods · Predation · Interspecific competitionResale or republication not permitted without written consent of the publisher

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Several experiments were performed to determine the effects of cell toxin concentration, composition and toxicity of Alexandrium minutum on ingestion rate, egg production, hatching success and naupliar fitness of the copepod Acartia clausi. A combination of A. minutum and nontoxic algae (Prorocentrum micans, Tetraselmis suecica and Isochrysis galbana) was used as food. Copepods ingested a higher amount of A. minutum cells as the concentration of these toxic dinoflagellates increased, and also in response to decreasing total food concentration available for the copepods. A positive relationship was obtained between A. minutum cells ingested by copepods and total toxin concentration per copepod. Hatching success and naupliar production were lower when copepods ingested a higher amount of toxic dinoflagellates. This negative effect could has been due to the accumulated toxins in the egg and copepod tissues, and was higher when A. minutum had a higher cell concentration of GTX1. Finally, the results obtained from nauplii incubated with T. suecica and I. galbana showed that nauplii hatched from females fed non-toxic food (T. suecica and I. galbana) reached copepodite stage earlier than those nauplii hatched from females fed with a combined of toxic (A. minutum) and non-toxic (T. suecica and I. galbana) food. KEY WORDS: Dinoflagellate · Copepod · Toxins · PSP · ReproductionResale or republication not permitted without written consent of the publisher

This study was carried out during an autumn bloom of Dinophysis acuminata in the Galician Rías Bajas (NW Spain). The main objective was to determine whether any of the predominant zooplankton species could ingest and transfer toxins through the pelagic food web. Grazing experiments showed that the copepods Temora longicornis and Oithona nana and the tintinnid Favella serrata fed on Dinophysis spp. whereas the copepods Acartia clausi and Euterpina acutifrons did not. However, only F. serrata seem to profit from the ingestion of the toxic dinoflagellates. Field populations of F. serrata increased whereas T. longicornis and O. nana densities declined after the toxic outbreak. Okadaic acid content found in the seston size fractions 100-200, 200-300 and 300-1000 µm showed a good correlation with F. serrata. These results confirm the hypothesis that tintinnids can transfer dinoflagellates toxins to higher trophic levels in the pelagic food web. The importance of faecal pellets with undigested dinoflagellates as an alternative pathway to transmit toxins to pelagic or benthic organisms is mentioned.