Editor’s Note: William Gilly, a professor of cell and developmental biology and marine and organismal biology at Stanford University, is traveling with a group of students on board the Don José in the Sea of Cortez. They will monitor and track Humboldt squid and sperm whales in their watery habitats. This is the group’s first blog post for ScientificAmerican.com.
SEA OF CORTEZ—Today we awoke to pink sunrise reflected off the gentle, rich waters of the Sea of Cortez. To us, it may as well have been the universe’s first sunrise, the birth of the world. We are 10 undergraduates, a teaching assistant, two professors and various scientists and crew aboard the Don José in the Gulf of California. Yesterday we left the boats and sidewalks of La Paz behind and cruised to Bahia Mangeles on the northwest side of Isla San José, where we anchored for the night. After dark we found ourselves visitors in a world constructed of intricate, alien life. The night was made of milky fish darting about our boat, silent cacti marching down the desert hills to the sea, strangely gentle movements of air, and the eternal constellations.
For the next three weeks, we will explore, carry out research and satiate our curiosity—as John Steinbeck and Ed Ricketts stated about their 1940 voyage through these storied waters, "we wanted to see everything our eyes would accommodate." Each student has a project ranging from nudibranchs to whale communication to videography. Sperm whales and the Humboldt squid on which they prey will be our targets during the next week at sea, and with luck, we hope to study interactions of these creatures using underwater video, acoustic sampling and electronic tagging.
Throughout the morning we rotated watches on the sun deck, with pairs of students constantly scanning the horizons for sperm whales. We also rigged a hydrophone to drag behind the boat and periodically stopped to listen for the calls of any whales we could not see. Sperm whales make distinctive clicking noises that can be heard on the hydrophone up to 10 miles away. But the only sounds were the squeaks of several pods of dolphins, some of which played around our bow as we searched for the leviathan north of Isla San José.
By 10 A.M. we had not seen any whales whatsoever, so we turned east across the Gulf to a tiny island, Farallon San Ignacio, off the Sonoran Coast. You won’t find this island on many maps, because, as Herman Melville notes in Moby Dick, true places are never on any map. Many squid and sperm whales were found near this island during the last course in 2008, and following our fishermen’s instincts, we will search there again. The crossing takes 12 hours, and on the way we are periodically recording depth profiles (to 600 meters) of water temperature, salinity, oxygen and chlorophyll using an instrument called a CTD profiler—an acronym for conductivity, temperature and depth (electrical conductivity is how salinity is measured). The measurements will reveal how these physical properties of the water column change on a west-to-east transect across the Gulf. We will roughly follow a transect done in 2008, allowing us to compare the years.
Halfway across the Gulf, at our third of six CTD stations, we encountered pods of Risso’s and bottlenose dolphins. Both species are serious squid-eaters, and we found two tiny arm tips from a type of mid-water squid floating on the surface (exact species to be identified later). These probably were bits dropped by the foraging dolphins. Our CTD cast revealed that the mid-water oxygen minimum zone (where oxygen is less than 10 percent of the value at the surface) was less than 100 meters deep—on the Baja side of the Gulf it had been nearly 200 meters deep. Maybe the shallow OMZ makes it easier for the dolphins to feast on mid-water squid that tend to inhabit the OMZ.
As our journey continues, this blog will continue. Written by the undergraduates, it will describe our daily activities—scientific, philosophical, leisurely or otherwise—and explain the diverse projects under way. For now, the diesel engine and wavelets jostle the boat as we cruise to the location of the fourth CTD cast, while the sun sets and spinner dolphins twirl beside the boat.
Read more about the Stanford Holistic Biology class here.
Image of jumping dolphin courtesy of Lauren Linsmayer; image of students listening to sperm whale on hydrophone courtesy of Liz Parissenti; image of CTD profiler deployment courtesy of Chris Rurik