Whales and the spring plankton bloom

The waters off New York harbor hold their breath in late spring, then exhale in an explosion of microscopic life. Warming currents carry with them the season's first great abundance: billions of copepods (Calanoida) and zooplankton rising from the depths as phytoplankton blooms paint the surface waters green. The ocean becomes soup thick with life barely visible to the naked eye, each cubic meter holding thousands of tiny crustaceans no bigger than rice grains. If you are near the water now, notice how the harbor light has changed, how it catches differently on water made dense with invisible plenty.

Into this underwater meadow come the North Atlantic right whales (Eubalaena glacialis). These fifty-ton filter feeders arrive with the precision of clockwork, their migration timed to the ocean's most productive weeks. A right whale's mouth opens like a cathedral door, revealing baleen plates that hang seven feet long like vertical blinds. Water rushes in carrying millions of copepods, particularly the energy-rich Calanus finmarchicus that fuel the whale's massive body. The baleen filters hold the copepods while water streams back through, leaving behind a mouthful of concentrated protein that can weigh a ton in a single feeding session.

This convergence represents one of nature's most precisely calibrated relationships. The copepods time their reproduction to the spring bloom of diatoms and phytoplankton, riding ocean currents that concentrate them into dense patches. The whales have followed these same feeding grounds for millennia, their migration routes hardwired by generations of successful feeding. A right whale must consume thousands of pounds of copepods each day during these peak weeks, building fat reserves that will sustain the animal through summer months when food becomes scarce. The whales feed by swimming slowly through the densest patches, mouths agape, their throat pleats expanding accordion-style to accommodate massive volumes of plankton-rich water.

But this ancient rhythm faces modern pressures. Right whales number fewer than 340 individuals, making them among the world's most endangered marine mammals. Their dependence on specific feeding areas during predictable seasons makes them vulnerable to ship strikes and fishing gear entanglement precisely when they are most focused on survival. Climate change threatens to shift the timing and location of plankton blooms, potentially disrupting a relationship millions of years in the making. The copepods themselves respond to water temperature changes measured in single degrees, their reproduction cycles shifting with warming seas. Listen now to the water lapping nearby, whether it is harbor waves or distant shore. In that sound is the pulse of an ocean system still holding its ancient rhythms, still bringing together whale and copepod in late spring waters, still exhaling abundance into the warming light.