Relationships among upwelling, phytoplankton blooms, and phycotoxins in coastal Oregon shellfish

Abstract

Climatologies derived from satellite data (1998 to 2007) were used to elucidate seasonal and latitudinal patterns in winds, sea surface temperature (SST), and chlorophyll concentrations (chl) over the Oregon shelf. These were further used to reveal oceanographic conditions normally associated with harmful algal blooms (HABs) and toxic shellfish events along the Oregon coast. South of 43°N, around Cape Blanco, summer upwelling started earlier and finished later than north of 43°N. Spring blooms occur when light limitation is relieved, before the initiation of upwelling, and secondary, more intense blooms occur approximately 2 wk after upwelling is established. North of 45°N, SST and chl are heavily influenced by the Columbia River plume, which delays upwelling-driven cooling of the surface coastal ocean in spring, and causes phytoplankton blooms (as indicated by increased chl) earlier than expected. The presence of saxitoxin in coastal shellfish, which causes paralytic shellfish poisoning, was generally associated with late summer upwelling. The presence of domoic acid in shellfish, which leads to amnesic shellfish poisoning, was greatest during the transition between upwelling and downwelling regimes. This work demonstrates that satellite data can indicate physical situations when HABs are more likely to occur, thus providing a management tool useful in predicting or monitoring HABs.

Harmful algal blooms along the North American west coast region: History, trends, causes, and impacts

“…In WA, little is known about the origin of coastal blooms of Alexandrium, but it is possible that they may also be brought inshore when upwelling winds relax or downwelling winds occur and enter coastal bays; e.g., Grays Harbor and Willapa Bay (Roegner et al, 2002), although this is not always the case (Cox, 2001). The relaxation or reversal of upwelling-favorable winds is also likely an important mechanism for bringing blooms into contact with the Oregon coast, and Tweddle et al (2010) showed that elevated toxin levels were associated with late summer upwelling. Anthropogenic nutrient sources are more likely to be relevant in inland waters along the Strait of Juan de Fuca and in Puget Sound (Rensel, 2007), although with the exception of some shallow bays, the nutrient source is still more likely upwelled waters.…”

“…Since 2007, Oregon has been monitoring surf zone phytoplankton for the presence of HABs and Alexandrium is commonly observed in samples, especially from the middle of June through September when the water temperature is >12.5 8C (ODFW data at http://bioweb.coas.oregonstate.edu/$mocha/ odfwdata.html). High levels of saxitoxin in shellfish tissues are also often associated with late summer upwelling and higher chlorophyll concentrations (Tweddle et al, 2010). Comparing the tissue PST data with the surf zone Alexandrium data indicates that a very low abundance of cells can result in elevated levels of tissue toxins (ODA and ODFW data at http://bioweb.coas.oregonstate.…”

Pseudo-nitzschia physiological ecology, phylogeny, toxicity, monitoring and impacts on ecosystem health

“…Another initiation site, or ''hot spot'', for toxigenic Pseudo-nitzschia blooms is the Heceta Bank, off the Oregon coast . The impact of DA toxicity on razor clam, mussel and Dungeness crab industries appears to be increasing in recent years, with exceptionally extensive and prolonged closures occurring from 2003 to 2005 (Tweddle et al, 2010). Additional hot spot areas in California include Monterey Bay, San Luis Obispo and Point Conception .…”

Time-Space Variability of Chlorophyll-a and Associated Physical Variables within the Region off Central-Southern Chile

“…These differences arise from latitudinal variation in large scale wind systems and/or from local variations in wind forcing linked to coastal topography, coastline orientation, and/or bathymetry; in addition, variations in large-scale circulation and mesoscale activity, and continental runoff can have a significant influence [11][12][13][14][15]. Geographical and/or local changes in the distribution of phytoplankton biomass and/or biological production rates have been positively related to spatial variability in wind-driven coastal upwelling [7,15,16] but, in some cases, this association has been found to be weak or negative [17,18]. The level of mesoscale activity (in terms of eddy kinetic energy) has been identified as an additional forcing factor causing cross-shore differences in the distribution of nutrients and/or phytoplankton (biomass and primary production rates) between and within EBCs [12,19,20].…”