The physical oceanography of upwelling systems and the development of harmful algal blooms

Abstract

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.

Climatic regulation of the neurotoxin domoic acid

“…If the latter is indeed a factor, it suggests the potential for "seeding" populations moving northward during warm ocean regimes. Several retentive areas (e.g., Heceta Bank and the Juan de Fuca Eddy) are conducive to phytoplankton bloom initiation, including toxigenic Pseudo-nitzschia (39)(40)(41). Northward advection during warm regimes may be a source of toxic blooms to these regions.…”

Gymnodinium catenatum Graham isolated from the Portuguese coast: Toxin content and genetic characterization

“…The distribution and population dynamics of Gymnodinium catenatum have been studied along the Portuguese coast (e.g. Amorim et al, 2001;Moita et al, 2003;Pitcher et al, 2010), but still little is known about toxin and genotypic variability of G. catenatum strains within regional populations (Costa et al, 2010). The aim of this study was to investigate possible toxin and genetic variability of G. catenatum populations present in Portuguese coastal waters.…”

Environmental Forcing of Red Tides in the Southern Benguela

“…The windward cape-leeward bay geography creates upwelling shadows where increased residence time builds phytoplankton biomass and harmful dinoflagellate blooms [55][56][57][58][59]. Alongshore winds and currents accelerated by the cape sweep clockwise into the leeward bay (Figure 3(f)).…”