Change in Bloom

(From left) Mary Hilbern, Art Miller, John McGowan, and Melissa Carter stand behind a bucket used for phytoplankton sampling at the end of the Scripps Pier.

Low-tech but persistent data series offers revealing clues about red tides, harmful algal blooms

It was the Roaring ’20s. It was a time of prohibition and speakeasies. The Charleston was all the rage on dance floors. Babe Ruth was king of baseball. Scripps Institution of Oceanography at UC San Diego entered its second decade of exploration and scientists at the young institution looked for new and different ways to explore the ocean.

Winfred Emory ("W.E.") Allen, an assistant professor of biology who joined Scripps in 1919, began investigating new methods of studying marine phytoplankton. One day Allen walked to the end of the Scripps Pier and collected a sample of sea water to evaluate, quantify, and record its phytoplankton content. He took another sample the next day. He collected samples, in fact, every day for the next 20 years. Without computers or technical equipment, Allen’s low-tech archive of sea water and phytoplankton resulted in a data "time series"–although it wasn’t called that at the time.

Decades later Scripps biological oceanographer John McGowan began poring over Allen’s historical pier data and the powerful insights they revealed. Inspiration took hold. In 1983, McGowan, in Allen-like fashion, launched a "cheap and easy" pier sample database to document baseline information about phytoplankton, water temperature, and other basic characteristics of samples taken twice a week.

After 18 years McGowan’s Scripps Pier data set has begun to provide valuable clues about important biological processes off the coast. The first scientific research paper based on McGowan’s data set is being published in the journal Progress in Oceanography and bears some revealing conclusions about Southern California phytoplankton blooms, including red tide events, which can kill fish and strip oxygen out of seawater, and harmful algal blooms.

Working on an interdisciplinary research team with lead author Hey-Jin Kim, a former Scripps student now based at the Monterey Bay Aquarium Research Institute; physical oceanographer Art Miller, and staff research associate Melissa Carter, McGowan and his collaborators discovered that the number of phytoplankton off Southern California has been on the rise over the 18 years of sampling. Major blooms occurred more frequently in the 1990s than the 1980s and the timing of these events appears to be creeping earlier in the spring, the data showed.

The team of researchers detailed six "extreme" outbursts of plankton growth, or red tides, events that are well known along the coast because of the crimson seawater discoloration along the shoreline.

The scientists did not pinpoint the cause of the blooming events–McGowan and others are working on this now—but with the data they were able to rule out two commonly thought sources: wind-driven upwelling, in which cold, nutrient—rich water rises to the sea surface from the ocean depths, and runoff from land. The new research indicates that the mechanism behind the plankton blooms is likely originating somewhere offshore.

McGowan says the work and funding devoted to the pier data set is not only paying dividends now, but will help unlock further mysteries off the coast because the data represent a baseline for making future comparisons.

"These types of long-term time series, especially with biological variables, are really rare," said Miller. "It was really only with (McGowan’s) foresight, creativity, perseverance, and inspiration that this analysis is possible."

McGowan is the first to admit that there’s little glamour in retrieving and analyzing a bucket of seawater from the pier twice a week. Such data take time to reveal results.

"You find out things about biology by doing time series that cannot be determined any other way," McGowan said. "It’s a very, very powerful technique. Ecological events happen rarely or episodically and in order to catch them you have to keep track of what’s going on. Then all of a sudden—whammo—something big happens and that reverberates through the system for years afterwards."

Highlighting the interdisciplinary nature of the research, McGowan credits Kim and Miller’s ability to analyze the physical forces in the marine environment to help them understand the biological outcomes.

The research was supported by the MacArthur Foundation, the California Cooperative Oceanic Fisheries Investigations (CalCOFI), National Science Foundation, NASA, the Department of Energy, the Office of Naval Research, and NOAA.

—Mario C. Aguilera

September/October 2009