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Shifting Seas (video)
November 12, 2002

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Interviewee: Steven Webster, Monterey Bay Aquarium.

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Produced by Jack Penland

Copyright © ScienCentral, Inc., with additional footage courtesy of Texas A&M;, PPL Therapeutics, University Of Missouri, Advanced Cell, and Boston Museum of Science.

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Monterey Bay National Marine Sanctuary

Seaweb

COMPASS - Communication Partnership for Science and the Sea

While we humans debate the politics of global warming, it appears that nature—in some places—is already looking for cooler weather.

Two studies—60 years apart—show that sea life is already dramatically changing along one spot in northern California.


The Tides of Time

The question of global climate change is a politically charged issue that has scientists worldwide trying to assess what is going on and why. But, it’s difficult for scientists to accurately measure an extremely large and complex event. Instead, they must observe many little events. For example, they might measure the size of a glacier and compare it to historical records. They could count the plants and animals somewhere, and try to decide if that’s different from the way things were in the past. From many smaller observations like these they can build the overall picture.

To be accurate, scientists can’t confine those smaller observations just to the land or the air. Since two-thirds of the earth’s surface is covered by water, they also need to try measuring changes in sea life.

That’s not an easy job. Waves and currents are always stirring the seas. Life beneath the waves is also constantly on the move.

Furthermore, you have to conduct your “sea census” where some other scientist already counted, and the original survey needs to be old enough and accurate enough to offer some perspective. Also, the spot must still be in essentially the same condition as the first survey. Since global climate change is a relatively new concern, such survey sites are hard to find.

At Hopkins Point in Monterey, California, researchers have been taking the ocean’s temperature since 1891. The area is a picturesque, rocky tide pool and home to Stanford University’s Hopkins Marine Station (the first marine laboratory on America’s Pacific coast). The Monterey Bay Aquarium and the Monterey Bay Aquarium Research Institute are also nearby. Birds wait on the rocks for low tide, hoping to feed on the abundant life below.

Low tide is also a chance for scientists to examine that life, a chance to count and categorize the snails, mollusks, anemones and other creatures hiding in the rocks.

The first ocean scientist to conduct a survey here was Willis G. Hewatt in 1931. The doctoral student laid out a series of 1-yard by 1-yard squares among the rocks in an area that had been made a marine reserve earlier that same year. He used brass bolts to mark the area. For two years he patiently counted all the life in those squares and earned his degree.

Not only did he create a detailed written record of what he found; he left those four brass bolts firmly anchored in the rocks of Hopkins Point.

Sixty years later, under the direction of Jim Barry of the Monterey Bay Research Institute and Chuck Baxter from Hopkins Marine Station, Stanford University undergraduate students Rafe Sagarin and Sarah Gilman decided to follow up on Hewatt’s study. They wanted to know if the temperatures around Hopkins Point had changed, and whether that changed the life in this tidal pool.

Sea Change

The first step was to check a hundred years worth of daily air and sea temperatures, do the math, and see if there had been a change. They found that the average sea temperature was up about 1 1/2 degrees, and the average air temperature up about four degrees.

They then found those four bolts and, like Hewatt, spent two years hunched over the rocks repeating his sea survey.

According to their study, published in the journal Science, Sagarin and Gilmore “counted and identified over 58,000 individuals…in 35 resurveyed plots.” They chose 45 species and assigned each to one of three range categories. The northern range species tended to live near Monterey and further north. The southern species range was from Monterey southward. The range of the cosmopolitan species was centered on the waters off the coast of Monterey.

They found that the sea life at Hopkins point had changed quite a bit since Hewatt’s survey.

According to their study, “Of the 45 species analyzed, 32 exhibited statistically significant relative changes in abundance.” Of the nine southern species, eight had, “increased significantly.” Of the eight northern species, five had “decreased significantly.”

Dr. Steven Webster, senior marine biologist of the Monterey Bay Aquarium, said the statistics, “are pretty solid data to indicate that over that period of 60 years, now 70 years, this area is coming to be much more like a southern California system.”

While this is only one study of one small tidal pool among all the oceans of the world, the study is strong statistical evidence that some sea life is already seeking somewhere new to play it cool.



by Jack Penland


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