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Module 4: Benefits of Whales A LEARNING TOOL ABOUT WHALES, INTERCONNECTED SPECIES & ORGANISMS, CLIMATE CHANGE AND HUMANITY - A CAPE BRETON UNIVERSITY SENIOR SEMINAR COMMUNITY ACTION PROJECT

Whales “play key roles in healthy marine ecosystems, providing services to human societies.” (Roman et al, 2014)

Benefits of Whales

Humans do not see whales on a daily basis and are often unaware whales can benefit ecosystems in many ways. Simply by freely being themselves in the oceans we benefit from their presence. They are the unseen heroes to our ecosystems. The benefits of whales was the starting point of this project giving evidence whales are vital to ecosystems and increase populations of other species and organisms, including an increase in krill and fish stocks. While we know whales eat large volumes of fish and krill humans also eat, we need to learn more about whales to know how they actually increase the productivity of the oceans in many ways. Whales are a benefit to all life which humans need to recognize, not only for sustainability reasons, but also for the survival of humanity.

Great whales can produce major nutrient influences acting as marine “ecosystem engineers” by influencing physical changes and species diversity important for restoration and management of the oceans with their population growth (Roman et al, 2014).

Roman et al (2014) explains there are four mechanisms or ecological pathways in which whales influence marine ecosystems, namely, whales as

  1. Consumers
  2. Prey
  3. “Vectors of nutrient and material flux”
  4. Whale falls as nutrient pathways.

Mechanisms by which whales can alter and engineer marine ecosystems:

(Credit: Roman et al, 2014)

Consumers

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).

Penguins

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
  • predation
  • 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).

Bubble Nets

Humpback whales purposely disturb the bottom of the ocean to flush prey out of burrows in:

  • mud
  • sand
  • 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).

Seabirds

Prey

While whales are large, they can also be prey in the oceans from large predators, such as giant sharks and killer whales, that can leave an assortment of indirect effects in the ecosystem (Roman et al, 2014).

Giant sharks (left), Killer whale (right)

As a result of the large removal of great whales, the diet of killer whales expanded to include smaller marine mammals, such as in the North Pacific Ocean harbor seals, Steller sea lions, and sea otters, which deceased these populations and specifically with respect to the loss of sea otters, created an increase in herbivorous sea urchins, and a decrease in coastal kelp forests (Roman et al, 2014).

Roman et al (2014) suggests in the Aleutian archipelago and places in the North Pacific Ocean, the decline of kelp forest lead to unexpected changes, such as:

  • reductions in primary productivity and coastal fish populations
  • decrease in marine withdrawal of carbon from the atmosphere.
Whale Pump (Credit: Roman et al, 2014)

“Vectors of Nutrient and Material Flux”

Only whales have the capability to create major nutrient transfers within the oceans or from deep layers to the surface (Moss, 2017).

Whales contribute to primary production through their “vertical mixing, horizontal transfer, and recycling” of carbon and ocean limited nutrients (Roman et al, 2014) where they occur in high densities (Roman et al, 2016).

When whales dive to feed they add energy through their movement that creates a mixing in the ocean, which is especially important when there is “stratified conditions” or calm winds (Roman et al, 2014).

Nutrients are transported to the surface of the ocean when whales release fecal plumes, called “whale pump”, and urine in the areas they feed when they:

  • respire
  • digest
  • metabolize, or
  • rest at or near the ocean surface (Roman et al, 2014).
Nutrient transfer between ecosystems (Credit: Moss, 2017)

Whale pump increases productivity in “biological hotspots” which are regions where there is high level of primary productivity with a “rich and diverse upper trophic levels” (Roman et al, 2014).

Whales, cetaceans and other marine mammals enhance the productivity of plankton by delivering large volumes of “primary limiting macronutrient” to the upper levels or “photic zone”, where sunlight enters into the depths to permit photosynthesis, as they feed at or below the warm water layer that decreases in temperature as depth is increased, and then eliminating near the surface high concentrations of ammonium to assist productivity (Roman et al, 2014).

Primary production in the Southern Ocean is limited by iron availability; however, sperm whales feed on prey living deep in the ocean and release whale pump at the surface promoting the transport of iron into the photic zone (Roman et al, 2014).

Because whales do not absorb much of their dietary iron, their “fecal plumes” have a “concentration of at least 10 million times greater than surrounding waters which could have a resulting benefit of exporting “at least 200,000 tons of carbon yr−1 from the atmosphere to the deep ocean” (Roman et al, 2014).

An increase in whale population would mean more iron being released at the ocean’s surface (Roman et al, 2014).

While “krill contain about 24%” of iron in the Southern Ocean’s upper 200 m, they would not increase in the absence of whales as there would be a lack ofwhale-contributed” iron fertilization necessary for primary productivity which further supports the value of whales in “marine nutrient cycling” (Roman et al, 2014).

Roman et al (2014) suggests great whales, such as baleen whales and humpback whales, who migrate between Northern and Southern Hemispheres contribute to the “horizontal transport” of essential nutrients across these long ocean journeys, baleen whales being those that have the farthest annual movements.

While these whales are in their “winter calving grounds” they fast and use their lipid reserves for maintenance of their metabolism and, with females, their milk production, they release necessary primary limiting macronutrient into waters that usually offer little ability to sustain life during their reproductive migrations forming a “great whale conveyor belt” enhancing productivity in “lower-level breeding areas” during recovery of whale populations (Roman et al, 2014).

Blue Whale

Whale Falls

Great whales are the biggest form of organic material to fall to the seafloor enriching the nutrient and energy deprived realm with:

  • proteins and lipids
  • altering the food availability
  • providing habitat
  • supporting diverse biotic communities (Roman et al, 2014).

Whale carcasses go through an “ecological succession” in the North Pacific in stages:

  • mobile-scavenger stage” when sharks, hagfish and other organisms feed on the soft tissue
  • enrichment‐opportunist stage” where seafloor organisms feed on the enriched sediments bones
  • sulphophilic stage” which can remain for decades supporting over 200 microscopic animal species that are able to manufacture organic molecules from water and carbon dioxide (Roman et al, 2014) including species that have two sets of eyes in shallow marine habitats and species without eyes in deep sea habitats (Shimabukuro et al, 2017).

Whale falls have led to both ecological and evolutionary enrichment on the seafloor with more than 60 microscopic animal species connected only to whale falls; however, many of these species may go extinct as a result of the increased absence of whale falls (Roman et al, 2014).

Roman et al (2014) suggests great whale falls can efficiently transfer carbon from the ocean’s surface to the deep sea at a rate of 190,000 tons of carbon yr−1.

An increase in whale populations to previous historical numbers would lead us to an important increase in carbon export to the magnitude of “climate engineering” to “mitigate climate change” (Roman et al, 2014).

Given the massive decline of whales, the reorganization of ocean ecosystems creates an unnatural trophic pyramid with larger numbers of smaller animals rather than larger animals historically (Pearce, 2010).

Keeping whales fed is possible if their prey is constantly being produced suggesting a greater population of whales would help feed the ecosystem instead of devouring it (Pearce, 2010).

This could be achieved by whale falls feeding scavenging species for up to 80 years (Pearce, 2010) depending on the size of the whale carcass (Shimabukuro et al, 2017).

While whales can also be stranded along coastlines, these numbers are small compared to whale falls that occur in the ocean (Roman et al, 2014).

Video Link:

Baleen Whale Fall Becomes a Deep Sea Banquet at Davidson Seamount | Nautilus Live

Whale Population Recovery and Ocean Restoration

After learning about the many benefits of whales, it is astonishing whale populations are at such grave declines. As humans we continue to gain knowledge as we gain information but we have not been putting our knowledge of the benefits of whales to good use. We may learn more benefits of whales to enrich ecosystems and benefit humanity. While increasing whale populations will not fix all of the problems humans have created, it will have a positive effect to help stabilize the oceans with many benefits.

Roman et al (2014) suggests whales “play key roles in healthy marine ecosystems” benefiting human societies and the functioning of our ecosystem which is expected to improve as whale populations recover.

Some whale populations are recovering from commercial whaling to a decline today of 66% to as high as 90%, such as the North Pacific humpbacks and southern right whales, while others, such as the North Atlantic right whales and Antarctic blue whales, may take decades or even centuries, if possible, to recover, as our oceans are changing and are hard to predict (Roman et al, 2014).

Ecosystem services provided by whales:

(Credit: Roman, et al, 2014)
Created By
Maria Lisa Polegatto
Appreciate

Credits:

Created with images by Francesco Ungaro - "untitled image" • Cameron Venti - "untitled image" • Jason Row - "Adelie Penguins leap to land from the frozen waters of Antarctica" • Dick Martin - "Bubble Net Feeding is a unique feeding technique employed by Humpback Whales, in which a group of whales swim in a shrinking circle blowing bubbles below a school of fish. This shrinking column of bubbles surrounds the school of fish forcing them upward. The whales spontaneously swim upward through the bubble net, mouths wide open, catching thousands of fish in one gulp. http://alaskasphotos.com/main.php/v/MLS_6555c-bubble-net-feeding.html " • Hanson Lu - "flight" • Tim Cole - "untitled image" • Gerald Schömbs - "untitled image" • Tim Cole - "untitled image" • Jakob Owens - "untitled image" • Robyn Carmel - "With ocean temperatures rising, food productivity along the California coast has declined. Humpback Whales have had to forage much closer to shorelines (AND the Golden Gate Bridge!) due to krill and other prey items being pushed towards the coastline as a result of climate change and crashing food populations such as herring and anchovies." • George Karelitsky - "Humpback Whales in Alaska" • NOAA - "Sperm whale flukes"