The great whales are the largest creatures on Earth, but their relative rarity in our oceans means they are generally overlooked in favor of the far more abundant algae and planktons when it comes to assessing influences on ocean ecology. However, a new study published by the University of Hawaiʻi at Mānoa evaluates decades of research on the role of baleen and sperm whales — and discovered that they have a much larger impact on marine ecosystems than previously believed.
Through the phenomena known as a “whale pump” and “the great whale conveyor belt,” these ocean giants recycle nutrients and keep them moving through the oceans so that they don’t settle to the ocean floor where they are inaccessible to other marine life. Whales mix the water column due to their bulk, and after they’ve fed at depth, they return to the surface and release fecal matter. This supplies iron and nitrogen to the surface microorganisms at the bottom of the food chain. The baleen whales in particular travel between their rich, high-latitude feeding ground and their low-latitude calving grounds annually. They release nitrogen in the form of urea into the comparatively nutrient-poor equatorial areas after transporting nutrients nearly 10,000 kilometers, hence the conveyor belt analogy.
The great whale populations suffered terribly due to commercial hunting, with populations decreasing by an estimated 66 to 90 percent. Numbers are slowly beginning to rise again and recovery is potentially critical for ocean resiliency. The study notes that recovered whale populations would also benefit rather than compete against commercial fishing industries, saying the increased nutrient input “could lead to higher rates of productivity in locations where whales aggregate to feed and give birth,” supporting more robust tropical fisheries. The study also discusses “whale-fall specialists,” species that evolved at great depths to take advantage of the enormous nutrient payload delivered when a dead whale sinks to the sea floor. A 40-ton great whale carcass deposits 2,000 times the annual nutrients that would otherwise fall on a given area. The study speculates that many species reliant on whale falls could well have become extinct due to the human-induced population declines before we ever had a chance to discover them.
The “Whales as Marine Ecosystem Engineers” study was conducted by an international team of 10 researchers, led by Joe Roman from the University of Vermont. Roman states that the study’s findings, “Warrants a shift in view from whales being positively valued as exploitable goods – or negatively valued because they compete with people for marine fish – to one that recognizes that these animals play key roles in healthy marine ecosystems, providing services to human societies.”