Porpoises in the San Francisco Bay – an example of how a small change can have big results!

Sometimes in a rapidly changing world, it is difficult to see the effects that small changes in human lifestyle can have on not only climate, but on ecosystems.  Various countries and international organizations are working to pass legislation to ensure change.  One such case of legislation working is being observed in the San Francisco Bay – the return of harbor porpoises.  This was recently reported in the QUEST biology blog.

The map below shows the location of the San Francisco Bay, marked by the bubble with an A, from Google. In 1972, the Clean Water Act was passed, working to improve the quality of water bodies within the United States by regulating the pollutants that were dumped into the ocean.  The quality of the water in the Bay began diminishing in the early 1900’s.  During World War II, the San Francisco Bay became a large war time port and ship building center.   By the time of the 1950’s and 1960’s, the Bay was so polluted that it literally smelled like raw sewage.

So when and why exactly did the porpoises leave the Bay?   The answer isn’t exactly clear.  From bone records found in the Bay, porpoises have made this location a home for hundreds of years.  As late as the 1930’s, there were reports of porpoise sightings.  But in the last 70-80 years, these reports were fewer and far between. Approximately three years ago, the first porpoises were spotted returning to the Bay.  Since then, Jonathan Stern,  a whale researcher from San Francisco State University who was featured in the QUEST article, and other researchers have been looking to find the answers to why they left in the first place, and what has caused them to return after so many years.   According to Stern, even though the Clean Water Act was passed in 1972, it takes awhile for the food supply to return, and even longer for predators of that food to return.

Harbor porpoises as seen from the Golden Gate Bridge. (Photo: William Keener/Golden Gate Cetacean Research). From the QUEST Science blog

While it isn’t easy to collect data from such a large body of water, the same types of phenomena can be observed in local streams and rivers that many GLOBE schools are visiting to record data.  The Hydrology Chapter of the GLOBE Teacher’s Guide has quite a few protocols that students could use to examine the quality of the streams and its effect on life.

For instance, a change in water pH, which can be collected through the pH protocol, can affect the types of macroinvertibrates found in the water body.  This in turn has an effect on the food chain – whether that be through an increase or decrease in food supply.  This would be an interesting research study to do over the course of many years - following local legislation and news articles on water quality, monitoring the water as a GLOBE school, and seeing if there are any changes found.

To read more information about the return of the San Francisco Bay harbor porpoises, head on over to the QUEST science blog.  If you’re a GLOBE school and are participating in any of the hydrology protocols, we’d love to hear from you and your findings!  Leave a comment here or email us at science(at)globe.gov!

-jm