The upwelling systems of the eastern boundaries of the world’s oceans are susceptible to harmful algal blooms (HABs) because they are highly productive, nutrient-rich environments, prone to high-biomass blooms. This review identifies those aspects of the physical environment important in the development of HABs in upwelling systems through description and comparison of bloom events in the Benguela, California and Iberia systems. HAB development is dictated by the influence of wind stress on the surface boundary layer through a combination of its influence on surface mixed-layer characteristics and shelf circulation patterns. The timing of HABs is controlled by windstress fluctuations and buoyancy inputs at the seasonal, event and interannual scales. Within this temporal framework, various mesoscale features that interrupt typical upwelling circulation patterns, determine the spatial distribution of HABs. The inner shelf in particular provides a mosaic of shifting habitats, some of which favour HABs. Changes in coastline configuration and orientation, and bottom topography are important in determining the distribution of HABs through their influence on water stratification and retention. A spectrum of coastline configurations, including headlands, capes, peninsulas, Rías, bays and estuaries, representing systems of increasing isolation from the open coast and consequent increasing retention times, are assessed in terms of their vulnerability to HABs.

The traditional interpretation of Coccolithus pelagicus as a cold water proxy is examined based on its distribution patterns in the water column off the Portuguese coast (using data from eleven cruises) and in Holocene surface sediment samples and Quaternary cores from the same region. Coccolithus pelagicus is common in the Portuguese upwelling system, an area where surface waters are predominantly of subtropical origin. Although revealing an affinity for low temperature upwelled waters, the species was found in waters up to 18ЊC associated with riverine plume and shelf-break fronts. C. pelagicus seemed to consistently occupy a particular ecological niche, between other phytoplankton groups, related to moderate turbulence conditions combined with nutrient availability. From this behaviour, it is proposed that C. pelagicus can be used as a tracer of the periphery of areas of enhanced productivity. Coccolithus pelagicus preferences for fronts of moderate temperature and salinity gradients are tentatively used to explain particular features of its sedimentary record. The repeated increase of C. pelagicus in thanatocoenoses (surface sediment assemblages) close to three river mouths, on the Portuguese shelf, are interpreted as a positive response to the development of riverine plumes. On the other hand, inconsistencies in the correlation between sea surface cooler-glacial and warmerinterglacial isotope stages and the relative abundance pattern of C. pelagicus during the Late Quaternary, as registered in two Galicia Bank piston cores (42ЊN), are tentatively explained in terms of shifts in the extent of the outer limit of the local palaeoproductivity belt off the Iberian Peninsula.

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Diatom and coccolithophorid abundance and diatom assemblage composition found in the water column along the Portuguese margin, during upwelling and non-upwelling conditions, are compared to the distribution patterns observed in the recent sediments from the same area. The water column results indicate a one order of magnitude increase in phytoplankton biomass during upwelling conditions (summer), with diatoms being the most important contributors. Coccolithophorids, on the contrary, dominate the phytoplankton in winter (non-upwelling). The comparison of the upwelling and non-upwelling spatial distribution of these phytoplankton groups to their sedimentary record reveals the sediment record as a reflection of the upwelling situation, preserving most of its original spatial variability. The comparison between living and fossil diatom assemblages indicates that from the two genera which dominate the summer biological assemblage, Pseudo-nitzschia and Chaetoceros, Pseudo-nitzschia is not represented in the sediments, while Chaetoceros is the dominant form of the sediment. Thalassiosira, which occurs in the same abundance in both seasons, responding to both river and upwelling nutrient input, can not be a reliable indicator of any single process. However, this genus distribution in the sediments can be used as an indicator of continuous nutrient availability. Such results are of great importance,for paleoceanographic reconstructions, since they constitute a good indication that the sediment record, even though somewhat altered with respect to assemblage composition, does reflect the water column characteristics. 0 Elsevier, Paris / Ifremer / Cnrs / Ird upwelling / Portugal I diatom I water column I sediment R&sum6-DiatomCes et coccolithophoridks dans la colonne d'eau et le sediment et memoire des upwellings au large du Portugal. L'abondance de diatomees et des coccolithophorides et la composition des populations de diatomtes ont CtC observees le long de la c&e du Portugal dans la colonne d'eau et dans les sediments recents. Pendant l'upwelling (it& la biomasse du phytoplancton dans la colonne d'eau augmente d'un ordre de grandeur avec les diatomees. En l'absence d'upwelling (hiver), les coccolithophorides predominent. La repartition de ces groupes dans le sediment reflete la situation d'upwelling en conservant la variabilite spatiale originelle. La comparaison entre les populations de diatomees vivantes et les fossiles indique que l'un des deux genres dominants en tte, Pseudo-nitzschia, nest pas represente dans le sediment tandis que l'autre, Chaetoceros, y predomine. Le genre Thalassiosira, present avec la m&me abondance pendant les deux saisons, en raison de l'apport de nutriments par le fleuve et par l'upwelling, ne peut etre l'indicateur fiable dun processus unique, mais la presence de ce genre dans les sediments indique la disponibilite permanente de nutriments. Ces resultats sont d'une grande importance en paleo-oceanographic car ils montrent que le sediment reflete les caracteristiques de la colonne d'eau, malgr...

Diatom and coccolithophorid abundance and diatom assemblage composition found in the water column along the Portuguese margin, during upwelling and non-upwelling conditions, are compared to the distribution patterns observed in the recent sediments from the same area. The water column results indicate a one order of magnitude increase in phytoplankton biomass during upwelling conditions (summer), with diatoms being the most important contributors. Coccolithophorids, on the contrary, dominate the phytoplankton in winter (non-upwelling). The comparison of the upwelling and non-upwelling spatial distribution of these phytoplankton groups to their sedimentary record reveals the sediment record as a reflection of the upwelling situation, preserving most of its original spatial variability. The comparison between living and fossil diatom assemblages indicates that from the two genera which dominate the summer biological assemblage, Pseudo-nitzschia and Chaetoceros, Pseudo-nitzschia is not represented in the sediments, while Chaetoceros is the dominant form of the sediment. Thalassiosira, which occurs in the same abundance in both seasons, responding to both river and upwelling nutrient input, can not be a reliable indicator of any single process. However, this genus distribution in the sediments can be used as an indicator of continuous nutrient availability. Such results are of great importance,for paleoceanographic reconstructions, since they constitute a good indication that the sediment record, even though somewhat altered with respect to assemblage composition, does reflect the water column characteristics. 0 Elsevier, Paris / Ifremer / Cnrs / Ird upwelling / Portugal I diatom I water column I sediment R&sum6-DiatomCes et coccolithophoridks dans la colonne d'eau et le sediment et memoire des upwellings au large du Portugal. L'abondance de diatomees et des coccolithophorides et la composition des populations de diatomtes ont CtC observees le long de la c&e du Portugal dans la colonne d'eau et dans les sediments recents. Pendant l'upwelling (it& la biomasse du phytoplancton dans la colonne d'eau augmente d'un ordre de grandeur avec les diatomees. En l'absence d'upwelling (hiver), les coccolithophorides predominent. La repartition de ces groupes dans le sediment reflete la situation d'upwelling en conservant la variabilite spatiale originelle. La comparaison entre les populations de diatomees vivantes et les fossiles indique que l'un des deux genres dominants en tte, Pseudo-nitzschia, nest pas represente dans le sediment tandis que l'autre, Chaetoceros, y predomine. Le genre Thalassiosira, present avec la m&me abondance pendant les deux saisons, en raison de l'apport de nutriments par le fleuve et par l'upwelling, ne peut etre l'indicateur fiable dun processus unique, mais la presence de ce genre dans les sediments indique la disponibilite permanente de nutriments. Ces resultats sont d'une grande importance en paleo-oceanographic car ils montrent que le sediment reflete les caracteristiques de la colonne d'eau, malgr...