Tiny Colossus of the Ocean Realm

     Resting below the surface, the blue whale hung suspended, nearly inert. Gradually, it roused to the calls of others like itself: whale voices; feeding sounds? Looking up, it saw a broad shadow backlit by sunlight. Slowly, it turned its gigantic body upward, to a near-vertical axis, then, with powerful thrusts of its tail flukes, accelerated toward the dark patch (who’d have thought it could reach such speed?!). Just before reaching it, the whale veered sharply sideways, opened its cavernous mouth, and lunged into the wriggling pink mass of crustaceans that resembled miniscule shrimp. Through the bristly baleen plates hanging from its upper jaw, the whale squeezed out a rush of water and swallowed the trapped-in krill. Engulfed by the whale, these krill had fulfilled their destiny as major players in the marine food web.

     Its size is small, but in the vast world ocean, krill’s significance is colossal. In every major ocean system, these marine invertebrates form the basis of the food web for whales, seabirds, fish, squid, seals, other invertebrates – even sharks. Through nutrient-rich upwelling triggered by the California Current’s seasonal winds, circulation patterns and lengthening daylight, our ocean waters provide sustenance for an incredible biomass. And throughout this system, krill is king, a “keystone species.”

     Of roughly 85 species worldwide, the dominant krill in north-central California are Thysanoessa spinifera and Euphausia pacifica, less than an inch long. Grazing on microscopic plants, or phytoplankton, they transfer energy up the food web to incrementally larger animals. Krill may swarm in bait balls as dense as 100,000 per cubic yard throughout the water column. Patches of it may stretch for miles, sometimes visible from the air as wide, rosy swaths at the surface, or as dark ruddy masses, just below.

     Krill is the near-exclusive food of gigantic blue whales. Humpbacks prefer its superior caloric value to that of small fish. Whales, using their long-distance hearing, can recognize the feeding grunts of their kin that indicate the dinner bell has sounded, the feast has begun. Dolphins and sea lions may join the frenzy, chasing down fish and other krill-eaters, using visual clues like hovering seabirds to locate distant prey patches. Krill can lay out an impressive seafood smörgåsbord.

     Commercial salmon, rockfish, flatfish, sardine and squid fisheries depend on it. Without even seeing its stomach contents, fisherfolk can tell a salmon has eaten krill, by the bright pink color of its flesh. If it’s eaten mostly small fish, the flesh will be paler, less flavorful.

     Some animals migrate thousands of miles to find it, targeting California, Washington and Oregon waters in the summer-fall feeding season; our marine sanctuaries often mark prime feeding sites. But abundance varies from year to year. When scarce, the entire marine ecosystem is sent reeling, causing animal migration patterns to shift radically: whales that usually feed off our coast may hunker down in lower latitudes to feed on what little prey they can find. Species unable to migrate may starve. Seabirds fail to fledge their chicks, or skip breeding altogether.

     But when krill is abundant, marine life doesn’t just survive -- it thrives. In spring 2017, seabird rookeries teemed with countless healthy chicks. And off San Francisco on June 26, 2017, during a two-hour shift, Farallon Island biologists spotted an incredible 248 krill-gulping blue, humpback and fin whales. Life was good.

     You can help conserve marine life, from krill to whales, and others in between. It’s a big job, but start at home, and proceed from there: reduce dependence on carbon-based fuels like gas, coal and oil that pollute our seas. Educate yourself and your community about clean energy alternatives. Be an earth-wise consumer, and learn which businesses and products are truly “green.” Use the power of your vote and the power of your purse to work toward achieving these worthy goals that will benefit all creatures, great and small, that inhabit our blue planet.

Mary Jane Schramm • NOAA Greater Farallones • Nat'l Marine Sanctuary

Maryjane.schramm@noaa.gov • Photo Credits: Top Left: Krill from local waters. Credit: ACCESS-NOAA; Top right: Krill from Cordell-Farallones-Point Blue ACCESS cruise. Credit: ACCESS-NOAA;  Above: Blue whale lunge-feeding on surface swaths of krill. Credit: Unknown. • more, visit https://go.usa.gov/xUmcp; also, https://www.newscientist.com/article/dn19841-blue-whale-feeding-methods-are-ultra-efficient/; National Geographic: https://www.youtube.com watch?v=cbxSBDopVyw