Cetaceans as Oceanic Engineers
Cetaceans play important roles in marine ecosystems and can be regarded as oceanic ecosystem engineers. By enhancing nutrient cycling and carbon storage and sequestration, cetaceans have the capacity to alter their environment. Whales release buoyant, nutrient-rich fecal plumes in surface waters that can stimulate phytoplankton growth, creating the essential foundation upon which marine life relies. Whale-mediated vertical flux of nutrients to the surface from below the mixed layer, and horizontal flux via migration from nutrient-rich feeding grounds to nutrient-poor breeding grounds, can be especially important in enhancing ecosystem functioning. Cetaceans also contribute to ‘blue carbon’, which refers to the natural processes through which the ocean traps carbon. Whale-stimulated phytoplankton that is unconsumed may sink to depth, leading to carbon storage and/or sequestration. Through their large body sizes and long lifespans, cetaceans have great capacity to store carbon for decades to centuries. When carcasses sink to the seafloor, that lifetime of stored carbon can be sequestered for millennia. As many populations recover from commercial whaling and other stressors, there is increasing potential for whales to enhance nutrient and carbon cycling. While intriguing, understanding of these processes is still largely in its infancy. However, there are ample opportunities to integrate data collection within current and future research programs to advance knowledge of the fine-scale mechanisms through which cetaceans contribute towards nutrient and carbon cycling. Understanding the role of cetaceans and other marine life in the carbon cycle is a potentially innovative and important strategy for combatting climate change that can be used alongside strategies to directly reduce fossil fuel emissions.