Whale Poop Plays A Vital Role In Ocean Ecosystems

February, 2011

Researchers off the coast of Maine have found that whales play a crucial role in the ocean’s nitrogen cycle, and may result in more abundant fish populations in areas where whales are concentrated. Most marine life deposits feces near feeding areas, but because whale feces floats, whales actively pump nitrogen back to the surface from their feeding grounds deep beneath the surface.

This discovery, published in the scientific journal PLoS ONE, found that nitrogen levels (NH4+) were dramatically higher in ocean waters where whales poop. The increases in nitrogen may help bolster tiny photosynthetic organisms including diatoms, cyanobacteria, and green algae called phytoplankton. In the western North Atlantic low nitrogen levels are thought to limit the growth of phytoplankton, and researchers speculate that whale poop may provide the added dose of nutrients needed to stabilize microscopic communities.

Even with whale populations diminished by overhunting, whales can still play a significant role in oceanic nutrient cycles. Whale pumps produce more nitrogen from their waste than all the rivers in the Gulf of Maine combined—about 23,000 metric tons each year.

Though some coastal areas suffer from excess nitrogen and other nutrients, a problem called eutrophication, many places in the ocean of the Northern Hemisphere have a limited nitrogen supply. So far whale poop has not been linked to eutrophication, which most often occurs in bays and estuaries located downstream of agricultural communities. Agricultural runoff from chemical fertilizers can create a “dead zone” such as the ones in the Gulf of Mexico and off the central coast of Oregon. The chemical nutrients in fertilizers can also trigger algal blooms to begin producing toxins.

It turns out that whale poop contains just enough nitrogen to help phytoplankton multiply. Phytoplankton have declined in eight of ten ocean regions over the past century, and this likely limits the abundance of all marine life that feed on them, from microscopic zooplankton
and invertebrates to fish and marine mammals. Low iron content is also thought to be a limiting factor in phytoplankton growth, along with rising ocean temperatures and acidification.

Because phytoplanktons are crucial to all marine life, increasing their productivity could help bolster fisheries and the human food supply. While the whaling industry has long argued that whales compete with humans for fish, it turns out that few whale species eat fish, and their role in increasing nutrient levels may even be crucial to restoring decimated fisheries.

Many ocean regions once supported a variety of marine mammals that were pivotal in the marine nutrient cycle. Some were hunted to extinction, such as the sea mink. Others, like many whale species, have been severely reduced. Restoring whale populations may be crucial to restoring the world’s fisheries, along with the many coastal communities that depend on the ocean for sustenance and livelihood.