Seasons in the Sea - Overview for March

March is the time of new beginnings in the sea off Central California. March is when the blustery northwest winds of spring start to bring deep, nutrient-rich water to the sea surface. March is also when billions of tiny single-celled drifting algae (phytoplankton) emerge from winter dormancy, taking advantage of increasing sunlight and nutrients to grow and reproduce.

Though invisible to the naked eye, these tiny algae form the warp and woof of Central-Coast food webs. Their spring growth helps define the larger pattern of life that will be woven over the course of the year--a pattern that includes everything from barnacles to blue whales.

Field Observations:
A March research cruise and plankton tow in Monterey Bay

We put out to sea from Moss Landing Harbor on a drizzly March morning. I stood at the rail of the research vessel, feeling cold, damp steel beneath my hand and breathing the scent of the salt spray. As we left the harbor mouth, the boat rolled and pitched with the steep, choppy seas left over from several days of gusty northwest winds. Fortunately for us, those winds had died down overnight.

Brian, the ship's captain, steered the boat toward an oceanographic monitoring buoy a few miles offshore in Monterey Bay. About half an hour later we saw the buoy emerge from the misty drizzle. Two technicians donned wet suits and SCUBA gear, then swam over to work on scientific instruments that bristled from the buoy like antennae on some ungainly aquatic insect.

As I watched the divers kick across the gray-green water, a marine biologist came on deck with what looked like a six-foot-long nylon stocking on the end of a long rope. Holding the rope in one hand, she tossed the "stocking" (a plankton net) over the side of the ship and dragged it through the water for a few seconds.

After pulling the net back on board, she rinsed its contents into a small glass jar. She then handed the jar to me and asked me to take it into the ship's lab while she collected a second sample.

Walking carefully across the slippery deck, I took a quick glance at the jar. As far as I could tell, it contained nothing more than clear, cold sea water, with perhaps a few bubbles and fragments of seaweed. But when I placed it on the lab bench and looked more closely, I was amazed to see dozens of tiny darting creatures about the same size and shape as the commas on this page.

The biologist came back with a second sample. Seeing me squinting at the side of the jar, she offered me a small hand lens. Peering into the water through the hand lens, I saw what looked like tiny silverfish darting back and forth with spasmodic jerking motions.

She explained that these were copepods, one of the most common type of tiny drifting animals, or zooplankton, in Monterey Bay. Looking closer, I noticed that the copepods were surrounded by tiny moving dots--other zooplankton that were too small to see clearly, especially on board a rolling ship.

After we returned to shore, I asked if I could take a look at this same water sample under a microscope. We carried the samples carefully into a lab. The marine biologist used an eyedropper to transfer a few drops of the sea water from the sample jar into a Petri dish (a glass plate a few inches across with a 1/2-inch-high rim).

Placing the Petri dish under a dissecting scope, the first thing I tried to do was to look more closely at the copepods. But they jerked their little antenna and zipped around so fast that I couldn't keep them in view very long.

Noticing some specks in the water with the copepods, I zoomed in to 40X magnification and discovered a wonderful menagerie of miniscule creatures. Some looked like tiny tadpoles with large mouths and wide staring eyes. Others looked like science-fiction aliens with triangular bodies, huge bulbous eyes, long spines, and other protuberances. Some of these animals swam feebly about using hundreds of tiny hairs as oars. Others just seemed content to float motionless in the water.

The marine biologist explained that these unworldly creatures were actually the young, drifting larvae of fish, crabs, and other animals that live in kelp beds and tide pools around the bay.

I had also noticed objects that looked like little twigs or bits of debris scattered across the bottom of the Petri dish. She said these were chains of diatoms.

I zoomed in to 75X magnification. At this scale, some of the diatoms looked like yellow-green glass bricks laid out in neat, curving rows. Other diatoms looked like green glass beads strung on long thin wires. Many of the diatoms sprouted long, dangerous-looking spines. Broken diatoms and spines lay everywhere. Rather than being surrounded by water, the diatoms seemed to be embedded in it; when I tapped on the side of the dish, the diatoms and debris jiggled as if set in Jell-O.

I looked up from the microscope and commented that the scattered diatoms made me think of construction debris from the building of the Emerald City in The Wizard of Oz. The biologist just smiled and said "It's pretty much all glass." Seeing my perplexed look, she explained that the shells of diatoms are composed of silica, just like window glass. She added that diatoms are by far the most common type of phytoplankton in Monterey Bay, especially in spring, when they form vast "blooms."

Stepping back and looking down at the Petri dish with my naked eye, all I could see was a little pool of clear sea water. But now I realized that this little dish contained a tiny, self-contained world, and an dizzying variety of plants and animals. I tried to extrapolate all the life I had seen under the microscope to the vast expanse of water in Monterey Bay. My mind struggled to imagine the uncountable numbers of living organisms growing and swimming and feeding and reproducing out there.

Overwhelmed, I left the lab, walked down to the beach, and contented myself with watching the afternoon sunlight shine through the translucent green waves. At this scale, I could almost comprehend the greening of the sea that takes place in March on the Central Coast.