As consumers, whales can have strong influences on marine communities both directly as predators and indirectly in interactions in the food-web at an estimate of 65% of primary production required in the North Pacific Ocean to sustain their populations prior to commercial whaling (Roman et al, 2014).
Without whales, this level of productivity is shunted to other species, however, in the past there likely was higher primary production due to “whale-induced recycling and upper-ocean retention of nutrients” (Roman et al, 2014).
While whales have a “high total metabolic rate” but a “low mass-specific metabolic rate” for their immense size, smaller animals would be limited to 8% of the biomass of the blue whale (Roman et al, 2014).
Therefore, if primary production was constant, reducing the populations of baleen whales lowers the marine ecosystems potential to retain carbon (Roman et al, 2014).
Whales are predators who can also have a major influence on both the ecological and the evolutionary changing aspects of prey populations that grow “through food webs and biogeochemical cycles”, such as the transport of nitrogen and iron (Roman et al, 2014).
With the removal of whales in the Southern Oceans during the 20th Century, other krill predators may have increased, such as penguins and fur seals in the Antarctic (Roman et al, 2014).
While marine mammals, including whales, can be thought of as reasons for fish population decline, direct evidence of this is limited (Roman et al, 2014).
In fact, it is suggested in ecosystems where whale populations were reduced, there was also large decreases in fish stocks; therefore, instead, the presence of whales resulted in an improvement in fish yields (Roman et al, 2014).
Species of blue whales in the Southern Ocean promote the productivity of fish stocks through whale pump (Roman et al, 2014).
Whales can provide stability and reduce both the occurrence and amount of fluctuations caused by concerns in relation to:
- climate issues
- primary productivity (Roman et al, 2014).
With the removal of whales, evidence suggests systems will be more at risk to external stressors and will be harder to manage (Roman et al, 2014).
Foraging whales can influence the local physical environment of the ocean. Whales diving and surfacing can enhance the upward movement of rich nutrients in deep water during feeding sessions (Roman et al, 2014).
Humpback whales create “bubble nets” creating a spiral flow using their breaths to round up their prey as the most fleeting of “engineered physical constructs” (Roman et al, 2014).
Humpback whales purposely disturb the bottom of the ocean to flush prey out of burrows in:
- broken shells (Roman et al, 2014).
Gray whales create meter-wide gouges by plowing the Bering Sea floor while foraging causing substantial sediments and nutrients to be suspended in the waters while also improving the recycling of nutrients and uncovering crustaceans from the ocean bottom to move them to the surface providing food for seabirds feeding on the surface (Roman et al, 2014).