After a long, cold winter, spring is finally upon us. As the days grow longer and the temperatures start to rise, plant growth increases. From the single-celled Phytoplankton thriving in the estuary’s nutrient-rich waters to the lush Spartina foliating in the marshes, the estuary literally seems to come to life. Sands are also starting to settle from the winter storms, and the beach profile is starting to take shape.
Clams, Oysters, and many other bivalves reproduce in the spring; since they are free-spawners, they send their larvae to join the great clouds of zooplankton for 60 to 80 days as they drift and swim in the offshore currents. As a result, the first good clam-digging tides of the year occur in spring. Acres of tidal flats are exposed to the morning sun and to eager predators–mostly consisting of birds and humans.
Barnacles are also starting to settle in the inter-tidal zone during the spring. Barnacles are planktonic until they gain weight and sink to the bottom. As they find a favorable substrate, they create a cement like adhesive from their heads and form a headstand position for the rest of their lives. Barnacles will land on everything from rocks and pilings to the shells of other animals (see photo).
Zooplankton populations explode in the spring and continue to flourish well into summer. Among them are holoplanktons, like copepods and mysids, which spend their entire lives in the estuary as plankton. Meroplankton are in the estuary temporarily in this form as the embryo and larval stages of such diverse species as clams, shrimps, crabs, sea stars, sea urchins, and fishes.
Horseshoe crabs are very active this time of year as well. As the water temperature gets warmer, it triggers the females’ eggs to start to grow and mature. Over the next two to three months, female horseshoe crabs will deposit 50,000 eggs into the upper beach during the high tides from the new and full moons. Their eggs are a large source of nutrients and energy for many other species in the estuary. Last year The WaterFront Center was able to count over 1,500 Horseshoe crabs at Beekman and Teddy Roosevelt beach alone!
Flocks of migrating birds and waterfowl swell the ranks of resident and overwintering populations. Some, such as the Red Knott, stop only briefly in the estuary to feed mainly on Horseshoe crab eggs. They gain three times their body weight before flying up to higher latitudes. A few species linger longer before heading north. Others remain in the area and join resident populations. These species will court and build nests in the marshes, meadows, and forests on the fringes of the estuary–most rearing fledglings by season’s end.
Some estuaries are hosts to spring migrations of anadromous fishes which move through on their way to freshwater spawning grounds. American shad, for example, start arriving in late April and continue arriving through May. Some marine species spawn or bear live young in the estuaries during the spring. Stripped Bass, perch, menhaden and herring are most popular with anglers.
It’s amazing to watch the transformation process that happens during the spring. From plants, to birds, to sea life, there’s so much new life. After such a cold, frozen winter, it’s great to see all this activity starting in the estuary. It means summer can’t be far behind!