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Monterey Bay P. australis bloom

A number of people have asked about the recent, large bloom of P. australis that was found in Monterey Bay. Lots of work still going on to analyze this, process samples and pull the whole story together. Many people are involved -- look for more info from them in the near future. Here's a quick summary from my perspective:

The bloom extended from Monterey Bay (especially the southern half) well to the south along the Big Sur coast -- the extent of the area we surveyed. Physical/chemical evidence suggests the bloom was responding to upwelled nutrients, with upwelling plumes diverting water/cells into Monterey Bay, along shore and off shore in a somewhat complicated pattern that can be seen in sea surface temperature images. Drifter tracks and vertical profiles provide an example of how cells can be advected from the nutrient rich upwelling center into the Bay where they subsequently sink and are then transported at depth back towards the original site of upwelling. This kind of "race track" circulation of water could explain how cells are transported ~southerly on the surface waters and ~northly at some depth in a recirculating pattern that may serve to sustain the bloom for long periods of time.

In the southern bight of Monterey Bay we observed 1e6+ cells per L extending from the surface to 60m -- from surface to bottom. Two-thirds of this biomass was probably sitting below the euphotic zone! This and many other observations paint a clear picture of cells sinking. The availability of a high biomass of toxin-producing cells in the water column as well as accumulating at depth illustrate how domoic acid may move through many branches of the food web, pelagic and benthic. Overt manifestation of toxicity may therefore appear to vary depending on "who eats who" where and when. Also many examples of subsurface populations of P. australis -- cells appeared to be sitting atop the thermo/nutricline in the 15 -20m horizon.

Thus far, per cell toxicity of P. australis appears to be low relative to what was observed at the height of the '98 bloom that was linked to sea lion illness and mortality. We think changes in per cell toxin concentration are linked to the physiological status of the cells, particularly as it relates to N and Fe availability. Understanding where toxin-producing cells are and something about the physcial and chemical environment in which those cells reside could thus help resource managers assess and predict the potential impacts of these blooms in the future.

Embedded within the P. australis bloom was a relatively intense bloom of Alexandrium catenella. We also noted the presence of Dinophysis cf. fortii, a species known to bloom in our waters and also known to produce diarrhetic shellfish toxins. So the "australis bloom of 2000" was really more of a triple whamy: P. australis, A. catenella and a touch of D. cf fortii for good measure. Imagine -- you might suffer from DSP, be unable to do anything about on account of the PSP, then forget the whole thing on account of the ASP!

Understanding these blooms, their spatial extent, variation in toxicity, etc., clearly demands access to waters beyond that reached by piers or small open boats. Use of DNA probe technology allowed us to detect these cells and map their distribution in near real-time aboard ship. Overlaying these images with plots of sea surface temperature and chlorophyll fluorescence made it possible to predict where we might find toxin-producing species, then test those predictions empirically. Information gathered was disseminated to Health Department officials, researchers in the Monterey Bay area, Monterey Bay Sanctuary representatives, etc., and NOAA personnel as it was collected. It was great to see so many people mobilize and cooperate to document this event.

Chris Scholin