Analysis of Future Harmful Algae Bloom Frequency in the Monterey Bay with the use of CMIP5 Models

Over the years, frequent Harmful Algal Bloom (HAB) events have been recorded in the Monterey Bay. This area is often considered a “hot spot” for, Over the years, frequent Harmful Algal Bloom (HAB) events have been recorded in the Monterey Bay. This area is often considered a “hot spot” for algal blooms due to its geological features and ocean circulation patterns. Although most algae blooms are harmless, species like Pseudo-nitzschia (diatoms) produce toxins which can have devastating impacts on ecosystems, local economies and public health. Analysis of future HAB events in Monterey Bay was conducted concerning changes in future climate conditions (i.e., changes in wind speeds and sea surface temperatures). Statistically downscaled Coupled Model Intercomparison Project phase 5 (CMIP5) representative concentration pathway (RCP) 4.5 and 8.5 scenarios from 1950 through 2099 were used to evaluate climatic changes the area may experience for the specified climate variables. Methods of analysis include time series analysis of 29 CMIP5 models for seasonal monthly mean wind speeds and 18 models for a seasonal monthly mean of sea surface temperatures for the projected years of 1950 through 2098 and 2006 through 2098 from the downscaled ⅛ degree BCSD CMIP5 monthly 4.5 and 8.5 RCP scenarios. The project found relatively consistent wind speeds throughout the century with minimal windspeed decline by the end of the century. Sea surface temperatures during spring and summer for RCP scenarios 4.5 and 8.5 show temperature increases ranging from 1.1°C to about 2.6°C. All sea surface temperature figures contain statistically significant positive trends. The summer seasonal multi-model mean had higher positive trends when compared to the spring multi-model mean. While this analysis includes the most prevalent climate variables present during HAB outbreaks, there are other environmental, climate, nutrient levels and geophysical parameters that impact HAB occurrences. Favorable conditions also vary between algae strains; conditions that may be optimal for one strain can be detrimental to another. Future work will include ocean circulation models in conjunction with water nutrient content to provide further in-depth analysis.