Seasons in the Sea - A month-by-month guide to Central California sea life
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Monterey Bay; Image credit: NASA

Overview

for April

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The pace of life quickens

April is the month when the pace of life quickens for marine organisms on the Central Coast. Upwelling kicks into high gear, creating almost continuous diatom blooms in nearshore waters. Wind-driven currents carry the diatoms and the accompanying microscopic grazers along the coast, providing food for larger animals such as krill.

Schools of small fishes, sea lions, and whales begin migrating northward along the California coast to take advantage of the bounty. Young marine mammals leave their nursery areas to make their way in an environment filled with food, but also with danger. Even animals on the seafloor benefit from debris that drifts down from the blooms and feeding frenzies near the sea surface.

Life in the kelp beds and the tide pools also becomes more competitive as algae and animals colonize vacant space created by winter storms. Crabs and other tide-pool animals gear up for frenzy of reproductive activity that will peak in June or July.

As storms become less frequent, sand begins to move from offshore areas toward shore, exposing some seafloor areas to colonization, but burying other areas closer to shore. Beaches and dunes begin to build up with the decline in winter storms.

Some seabirds gather in nesting colonies on cliffs and offshore islands, feeding on while others leave the area to nest thousands of miles away, often in remote parts of the Arctic. Shore and beach birds also gather in large flocks, then leave the area to nest elsewhere.

All of these trends continue in May, when upwelling and diatom blooms reach their yearly peak. Vast numbers of animals such as market squid, anchovies, and rockfish become supply essential nutrition for seabirds and other animals that give birth or migrate into the region to take advantage of the abundant food. The seeds of life that were planted in February, germinated in March, and leafed out in April, will be coming into full bloom.


Field observations:

The howling wind whipped at my jacket as I struggled to climb the sandy path through the dunes at Moss Landing State Beach. When I reached the crest of the dune, I stopped to admire the panorama of Monterey Bay stretching out before me.

White caps and spray streaked the cobalt sea. I could see the pale silouette of the Santa Cruz Mountains to my right and the Santa Lucia's to my left, their lower flanks veiled in sea mist.

I had taken a late lunch break this April afternoon, hoping to clear my head with a breath of fresh air, and maybe even do a little surfing. There was certainly no shortage of fresh air on this wind-swept beach, but the waves were completely unrideable--they heaved and churned chaotically in what surfers call "Victory at Sea" conditions. It had been this way every afternoon for the past week.

I shivered, remembering how cold the ocean had felt when I surfed a few days before--the water must have been down around 50 degrees Fahranheit. This meant that the northwest winds were forcing surface waters offshore, allowing cold water to rise up from the depths. I knew this cold water carried nutrients that are great for marine algae, but it can sure make life tough for surfers. A moot point today. I could see that I wouldn't be doing any surfing during this lunch break.

Just up the coast, to my right, the Moss Landing Harbor beakwater jutted out to sea. Flowing out from the harbor entrance was a tongue of green-brown water--the ebb-tide plume from Elkhorn Slough. My initial response was "yech." But then It occurrred to me that this plume was a rich soup of plant nutrients, microscopic algae (which gave the water its green color), swarms of microscopic animals, and even young fish, which might be returning to the sea after spending their first few months in the shallow waters of the slough.

Where the greenish water met the dark blue water of the bay, I could see dozens of seabirds, which at first I took to be seagulls, floating in long, irregular lines along the edge of the plume. I pulled my binoculars out of my backpack and looked again. The birds' long, graceful necks, sharp bills, and snappy black and white plumage identified them as grebes--probably Western Grebes stopping for bite to eat during their spring migration. Farther offshore, flocks of dark, lithe cormorants flew northward like geese, their wings flapping rapidly just above the sea surface.

Leaning into the wind, I walked down the eroded face of the dunes. Driftwood and dense tangles of kelp littered the upper beach. Relicts of a recent storm, they had already been partly buried by the blowing sand. Here and there, green shoots of dune plants struggled to keep their two or three leaves above the blasting sand and wind.

I walked down to the water's edge. Hundreds of pale pink mole-crab shells marked the high-tide line, along with fragments of sand dollars and clam shells. Looking closely at the mole-crab shells, I discovered that they were not fragments of dead animals, but just the hard shells off their backs. I remembered reading a scientific paper that described how mole crabs grew rapidly and shed their shells each time a pulse of food (microscopic algae) arrived at the beach.

I stood up and looked around again. It occurred to me that everything out here--the wind, the plume of green water, the birds, the dune plants, the mole-crab shells--were all connected. They were all signs of spring, of life returning after winter storms, of living things fattening up and gearing up for a summer of growth and procreation. I took a few more breaths of fresh air, then walked up the beach and headed back to my office to get warm.

    All text © Kim Fulton-Bennett                About            Contact            Disclaimer