It rained again this weekend. We are waiting for a good satellite image of the impacts of the event and should have one from today. So far this season 14.66 inches has been recorded at the National Weather Service’s (NWS) LA Downtown site.
One of the recent storms created a clear biological response in the ocean following the storm. As we mentioned in the previous posting on El Nino, runoff brings a lot of nutrients for plants (nitrogen, phosphorus, etc) into the ocean. Just as on land these plant nutrients promote plant growth, but the ocean plants are microscopic phytoplankton. Although microscopic, they are so abundant that they change the color of the water from blue to more greenish. The ocean color sensors on satellites detect these changes and enable us to measure the concentration of chlorophyll from the plants in the ocean. This enables us to measure the response of the upper visible ocean to the nutrient inputs from the rain runoff.
Between February 5 and 8 nearly 3.3 inches of rain was recorded at the downtown NWS site. That’s quite a bit of rain in a relatively short time. As a result there was a significant volume of runoff that went into the ocean. About 1 week after the rain event a significant phytoplankton response was observed from satellite with high concentrations in both Santa Monica Bay and San Pedro Bay south of LA/LB harbor, extending nearly halfway to Catalina Island (~10-12 miles). The two satellite images show the chlorophyll concentration a couple of days prior to the storm (top image) and the concentration about one week after the storm (bottom image). The large increase of chlorophyll between the two images shows the effects of the added nutrients from the runoff on the coastal concentrations of phytoplankton.
One of our research interests is not only that there are “blooms” of phytoplankton, but what species bloom, and under what conditions do they bloom. Some phytoplankton can produce toxins that are harmful to marine life, birds, and to humans if we consume shellfish or other fish that have eaten the toxic phytoplankton. To determine what species of phytoplankton are present we monitor the species of phytoplankton at various piers around southern California. Whether the runoff from land promotes the formation of toxic blooms is one question that we are addressing in our studies of these “harmful” blooms in southern California.
We’ll write more about that in the next installment.
Sources:
Rainfall information: National Weather Service - http://www.weather.gov/climate/index.php?wfo=lox
Satelliete Images: SCCOOS
http://www.sccoos.org/data/modis/modis_regions.php?r=3
1Hammond and Hazelwood, 1972.
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