Will A Warmer, More Acidic Ocean Lead To Increased Pseudo-Nitzschia Bloom Toxicity In The Southern California Bight? Website
Period: 2/1/2012 -
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Our goals for this project are: 1) To determine how future rising seawater pCO2 (reduced pH) will affect growth and synthesis of the neurotoxin domoic acid by local Los Angeles area species and strains of the harmful bloom diatom Pseudo-nitzschia; 2) Test how predicted levels of sea surface warming will affect the physiology and potency of these toxic diatoms; and 3) Examine the mutual interactive effects of acidification, warming, and other climate change variables such as altered light fields and nutrient availability, with regards to Pseudo-nitzschia growth and toxin production.
This project will take a dual approach to addressing these goals, by incorporating both laboratory culture and natural harmful bloom studies. The Hutchins laboratory currently maintains a number of culture isolates of domoic acid-producing Pseudo-nitzschia species from our local area, most of which were isolated by our graduate students. These cultures representing the dominant domoic acid-producing species that form blooms in the Southern California Bight (and other new isolates that will be obtained during this project) will be cultured in long term, steady state conditions over a range of environmentally relevant pCO2 levels, from present day (~390 ppm) to projected year 2100 concentrations (~800 ppm). Temperature experiments will use the same cultures maintained at either present day coastal ocean temperatures, or at levels ~3-4oC above current values, again representing expected mid- to late-21st century sea surface temperature values. Domoic acid toxin production will be measured using ELISA and/or HPLC, and cell physiology and growth will be closely followed using an established set of biological, biochemical, and biogeochemical analyses. These culture experiments will also determine how the interactions of pCO2 and temperature with each other, and with other variables such as nutrient availability and irradiance, will affect cellular toxin levels in these Pseudo-nitzschia species. These laboratory culture experiments will be complemented by field incubation experiments using the annually recurring toxic Pseudo-nitzschia blooms from the SCB, in order to examine CO2 and temperature effects on domoic acid production in natural communities.
One of the biggest challenges faced by the regulatory agencies that manage harmful algal bloom events along the Southern California coast today is accurately predicting their future impacts in a rapidly changing environment, and devising practical ways to adapt to these changes. This is especially critical as these blooms are occurring along one of the most densely populated urban coastlines in the world. A recent Science paper warned that upwelled water in our area is already carrying an alarmingly strong high-CO2, low pH imprint from anthropogenic CO2 enrichment (Feely et al. 2008). Our project will determine whether these rapid shifts in seawater carbonate chemistry, along with simultaneous sea surface warming trends, are likely to drive quantitative and qualitative changes in the toxicity of the most problematic harmful algal bloom (HAB) group in our area. It is obvious that accurate predictions of any future increases in the toxic footprint of HABs in a warming and acidifying ocean must be a priority for marine resource managers and public health agencies.
Reliable information on how pCO2 in combination with other environmental variables affects the toxicity of Pseudo-nitzschia will be useful in designing appropriate monitoring and prediction strategies. It has been noted, for instance, that highly toxic Pseudo-nitzschia blooms often occur in areas where coastal topography promotes strong upwelling (Trainer et al. 1998); these areas of freshly upwelled water are also precisely where seawater CO2 concentrations are the highest (Feely et al. 2008). The results of our study will thus be useful in making specific management recommendations, such as whether observing systems such as our local SCCOOS (Southern California Coastal Ocean Observing System) should consider including parameters like pCO2 and pH in their monitoring efforts, in order to improve their HAB forecasting capabilities.
This project cannot answer all of the important questions about the effects of anthropogenic climate change on harmful algal blooms in the Southern California Bight, but it will offer local resource managers an answer to one of the most critical uncertainties: Can we expect Pseudo-nitzschia blooms to become much more toxic in the future? The answer to this question represents a key step forwards towards learning to understand, predict, and adapt to the many changes that are likely to occur in harmful algal communities in the greenhouse ocean during the years to come.
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