![Whalefall_hires](https://upload.wikimedia.org/wikipedia/commons/1/1a/Whalefall_hires.jpg)
A whale fall occurs when the
carcass
Carcass or Carcase (both pronounced ) may refer to:
*Dressed carcass, the body of a livestock animal ready for butchery, after removal of skin, visceral organs, head, feet etc.
*Carrion, the decaying dead body of an animal or human being
*The str ...
of a
whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
has fallen onto the
ocean floor
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...
at a depth greater than , in the
bathyal
The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagi ...
or
abyssal zone
The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean a ...
s.
On the sea floor, these carcasses can create complex localized
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s that supply sustenance to deep-sea organisms for decades.
This is unlike in
shallower waters, where a whale carcass will be consumed by
scavenger
Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
s over a relatively short period of time. Whale falls were first observed in the late 1970s with the development of
deep-sea robotic exploration.
Since then, several natural and experimental whale falls have been monitored
through the use of observations from submersibles and remotely operated underwater vehicles (
ROVs) in order to understand patterns of
ecological succession
Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire) or more or less.
Bacteria allows for the cycling of nutrients such as ca ...
on the deep seafloor.
Deep sea whale falls are thought to be hotspots of
adaptive radiation
In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...
for specialized fauna.
Organisms that have been observed at deep-sea whale fall sites include
octopus
An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...
,
giant isopod
A giant isopod is any of the almost 20 species of large isopods, crustaceans distantly related to shrimp and crabs, which are decapods, in the genus ''Bathynomus''. They are abundant in the cold, deep waters of the Atlantic, Pacific, and Indian ...
s,
squat lobster
Squat lobsters are dorsoventrally flattened crustaceans with long tails held curled beneath the cephalothorax. They are found in the two superfamilies Galatheoidea and Chirostyloidea, which form part of the decapod infraorder Anomura, alongsi ...
s,
polychaete
Polychaeta () is a paraphyletic class (biology), class of generally marine invertebrate, marine annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that ...
s,
prawn
Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten.
The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature ...
s,
shrimp
Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...
,
lobster
Lobsters are a family (biology), family (Nephropidae, Synonym (taxonomy), synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs ...
s,
hagfish
Hagfish, of the class Myxini (also known as Hyperotreti) and order Myxiniformes , are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column, a ...
, ''
Osedax
''Osedax'' is a genus of deep-sea siboglinid polychaetes, commonly called boneworms, zombie worms, or bone-eating worms. ''Osedax'' is Latin for "bone-eater". The name alludes to how the worms bore into the bones of whale carcasses to reach enc ...
'',
crabs
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
,
sea cucumbers
Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...
, and
sleeper shark
The Somniosidae are a family of sharks in the order Squaliformes, commonly known as sleeper sharks. The common name ''"sleeper shark"'' comes from their slow swimming, low activity level, and perceived non-aggressive nature.
Distribution and hab ...
s. New species have been discovered, including some potentially
specializing in whale falls.
It has been postulated that whale falls generate
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
by providing evolutionary stepping stones for multiple lineages to move and adapt to new environmentally-challenging habitats.
Researchers estimate that 690,000 carcasses/skeletons of the nine largest whale species are in one of the four stages of succession at any one time.
This estimate implies an average spacing of and as little as along migration routes. They hypothesize that this distance is short enough to allow
larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
to disperse/migrate from one to another.
Whale falls are able to occur in the deep open ocean due to cold temperatures and high hydrostatic pressures. In the coastal ocean, a higher incidence of predators as well as warmer waters hasten the decomposition of whale carcasses.
Carcasses may also float due to decompositional gases, keeping the carcass at the surface.
The bodies of most great whales (which includes
sperm whale
The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus ''Physeter'' and one of three extant species in the sperm whale famil ...
s and many species of
baleen whale
Baleen whales (systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea (whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in their ...
) are slightly denser than the surrounding seawater, and only become positively buoyant when the lungs are filled with air. When the lungs deflate, the whale carcasses can reach the seafloor quickly and relatively intact due to a lack of significant whale fall scavengers in the water column.
Once in the deep-sea, cold temperatures slow
decomposition
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
rates, and high
hydrostatic pressures increase gas solubility, allowing whale falls to remain intact and sink to even greater depths.
Contribution to the biological pump
The amount of
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
tied up in a typical single whale carcass (about two
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s of carbon for a typical 40-tonne carcass) is roughly equivalent to the amount of carbon exported to a hectare of abyssal ocean floor in 100–200 years.
This amount of organic material reaching the seafloor at one time creates a pulse equivalent to about 2000 years of background
carbon flux
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major componen ...
in the 50 square meters of sediment immediately beneath the whale fall.
This helps to sustain the community structure that develops around a whale fall, but it also has potential implications for the
biological pump
The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments.Sigman DM & GH ...
, or the flux of organic material from the surface ocean to depth.
Whales and some other large marine animals feed on and follow large aggregations of zooplankton for sustenance. Based on simple trophic structure, this would mean whales and other large zooplankton feeders can be found at higher abundance around areas of high primary production, potentially making them important exporters of carbon to depth through food falls.
Biological pump models indicate that a large amount of carbon uptake by the deep sea is not supplied by particulate organic carbon (POC) alone, and must come from another source. Lateral
advection
In the field of physics, engineering, and earth sciences, advection is the transport of a substance or quantity by bulk motion of a fluid. The properties of that substance are carried with it. Generally the majority of the advected substance is al ...
of carbon, especially in coastal areas contributes to this deficit in the model, but food falls are also another source of organic carbon for the deep ocean.
Various percentages of the food fall contribution to the total carbon flux to the deep ocean have been hypothesized, ranging from 0.3% to 4%.
There is growing evidence that the contribution of food falls to the deep ocean carbon flux is larger than originally proposed, especially on the local scale in areas of high primary productivity. Unfortunately, contributions of food falls to the biological pump are hard to measure and rely on a few serendipitous studies on discovered falls
as well as planted carcasses
with much of the deep sea carbon flux studies relying on sediment traps.
Discovery
![Sample_collecting_at_whale_fall](https://upload.wikimedia.org/wikipedia/commons/6/6b/Sample_collecting_at_whale_fall.jpg)
The earliest indication that whale carcasses could host specialized animal communities occurred in 1854 when a new
mussel
Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...
species was extracted from a piece of floating whale
blubber
Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians.
Description
Lipid-rich, collagen fiber-laced blubber comprises the hypodermis and covers the whole body, except for pa ...
.
By the 1960s, deep sea trawlers unintentionally recovered other new
mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
species including
limpet
Limpets are a group of aquatic snails that exhibit a conical shell shape (patelliform) and a strong, muscular foot. Limpets are members of the class Gastropoda, but are polyphyletic, meaning the various groups called "limpets" descended indep ...
s (named ''
Osteopelta'') attached to whale bones.
The first recorded abyssal whale fall was discovered by US Navy
bathyscaphe
A bathyscaphe ( or ) is a free-diving self-propelled deep-sea submersible, consisting of a crew cabin similar to a bathysphere, but suspended below a float rather than from a surface cable, as in the classic bathysphere design.
The float is fi ...
pilots LT Ken Hanson, Master Chief George Ellis and LT Tom Vetter diving in bathyscaphe
Trieste II (DSV-1) on 19 February 1977.
The skeleton of the carcass, which was completely devoid of organic tissue, remained intact and collapsed flat on the seafloor. The submersible recovered a jawbone and phalanges. The whale was considered to be a
gray whale
The gray whale (''Eschrichtius robustus''), also known as the grey whale,Britannica Micro.: v. IV, p. 693. gray back whale, Pacific gray whale, Korean gray whale, or California gray whale, is a baleen whale that migrates between feeding and bree ...
based on the size of the bones and the skeleton, the lack of teeth and its location west of Santa Catalina.
The first whale-fall ecosystem, which included a chemoautotrophic assemblage living on the anaerobic breakdown of organic material in whale bones, was discovered by a team of
scientist
A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences.
In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...
s led by
University of Hawaii
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...
oceanographer
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics ...
Craig Smith in 1987. The DSV Alvin observed the remains using scanning
sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...
at in the
Catalina
Catalina may refer to:
Arts and media
* ''The Catalina'', a 2012 American reality television show
* ''Catalina'' (novel), a 1948 novel by W. Somerset Maugham
* Catalina (''My Name Is Earl''), character from the NBC sitcom ''My Name Is Earl''
...
Basin and collected the first photographic images and samples of animals and microbes from this remarkable community.
![Distribution of known whale falls](https://upload.wikimedia.org/wikipedia/commons/5/50/Distribution_of_known_whale_falls.jpg)
Many other whale falls have since been found by more researchers and deep-sea explorers as well as naval
submarine
A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
s. The increase in detection is largely due to the use of cutting-edge
side-scan sonar
Side-scan sonar (also sometimes called side scan sonar, sidescan sonar, side imaging sonar, side-imaging sonar and bottom classification sonar) is a category of sonar system that is used to efficiently create an image of large areas of the sea ...
which can minutely examine the ocean floor for large aggregations of matter. A 2022 study identified 45 known natural whale falls, 38 implanted ones, and 78 fossil ones with most in the Pacific but a significant number, particularly of fossil ones in the Atlantic.
Ecology
![Whale_fall_Whale_bone_recovery](https://upload.wikimedia.org/wikipedia/commons/7/75/Whale_fall_Whale_bone_recovery.jpg)
Whale falls are distributed heterogeneously throughout space and time, with a concentration along migration routes.
There is much faunal overlap in these whale falls across oceans. Mussels and
vesicomyid clams belong to groups that harbor
chemosynthetic
In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydro ...
bacteria, which can draw energy from
inorganic chemicals, such as sulfur. Before their presence was discovered at whale falls, the only known habitats of these groups were sunken wood and
hydrothermal vent
A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...
s. Similarly,
lucinid clams were previously only known to inhabit carbon seeps and
anoxic
The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:
* Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...
seafloor sediments
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mainly ...
.
Osedax, a genus of deep-sea polychaete worms, act as ecosystem engineers by excreting acid to erode whale bones and absorbing the nutrients trapped within.
This enhances biodiversity in the deep sea by increasing the water diffusion into the matrix of bones and facilitating colonization of the bone matrix by rarer species. Osedax have more dramatic effects in juvenile skeletons, which are not as well-calcified as adult skeletons.
At whale fall sites it is common to see between three and five trophic levels present, with two main nutritional sources constituting the base of the food web. Adult whale carcasses can house up to five trophic levels, whereas juveniles more typically have three.
Recent studies also show a possible trend of "dual niche partitioning", in which scavengers tend to reach peak densities on the carcass during the day and predators are more present during the night, reducing competition between the two trophic groups.
There is also a possible trend in tidal patterns and species occurrence, indicating that tides play a role in niche partitioning as well.
Similar ecosystems exist when other large volumes of nutrient-rich material fall to the sea floor. Sunken beds of
kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms.
Kelp grows in "underwat ...
create kelp falls, and large trees can sink to create wood falls. In more recent years,
shipwrecks
A shipwreck is the wreckage of a ship that is located either beached on land or sunken to the bottom of a body of water. Shipwrecking may be intentional or unintentional. Angela Croome reported in January 1999 that there were approximately ...
have also provided bases for deepwater communities. In ecosystems formed following a whale fall event, there are four stages of ecological succession.
Ecosystem stages
There are four stages of decomposition associated with a whale fall.
These stages vary in duration and overlap with one other with the size of the carcass, water depth, and other environmental variables, such as tidal flow.
Large, intact whale falls appear to pass through the four decomposition stages, while the stages on smaller or partial carcasses may be truncated.
Smaller cetaceans, such as porpoises and dolphins, do not undergo the same ecological succession stages due to their small size and lower lipid content.
Researchers believe the presence of Osedax worms may also be a contributing factor in the observed successional differences.
Stage 1
The initial period begins with "mobile scavengers" such as
hagfish
Hagfish, of the class Myxini (also known as Hyperotreti) and order Myxiniformes , are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column, a ...
and
sleeper shark
The Somniosidae are a family of sharks in the order Squaliformes, commonly known as sleeper sharks. The common name ''"sleeper shark"'' comes from their slow swimming, low activity level, and perceived non-aggressive nature.
Distribution and hab ...
s actively consuming soft tissue from the carcass. Consumption can be at a rate of per day.
This stage typically lasts months up to 1.5 years.
Stage 2
The second stage introduces the "enrichment opportunists". These are animals which colonize the bones and surrounding sediments that have been contaminated with organic matter from the carcass and any other tissue left by the scavengers.
This stage can last months up to 4.5 years.
Stage 3
In the third stage,
sulfophilic bacteria anaerobically break down the
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
s embedded in the bones. Instead of
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, they reduce dissolved sulfate () and excrete
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
. Due to the toxicity of , only resistant chemosynthetic bacteria survive. The
bacterial mat
A biofilm comprises any Syntrophy, syntrophic Microbial consortium, consortium of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a sl ...
s provide nourishment for mussels, clams, limpets and sea snails. As whale bones are rich in lipids, representing 4–6% of its body weight, the final digestion stage can last between 50 and possibly 100 years.
Stage 4
Some scientists postulate a fourth stage of ecological succession at whale fall sites, called the "reef stage".
A whale fall enters this stage once the organic compounds have been exhausted and only minerals remain in the bones, which provide a hard substrate for suspension and filter feeders.
Methanogenesis
A process called
methanogenesis
Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group ...
can also occur around whale falls. Archaea that produce methane can be abundant in anoxic sediment, but are typically not found in co-occurrence with the sulfur reducing bacteria found at whale falls. Whale falls do however support both sulfur reducing bacteria and methane producing archaea, leading to the conclusion that the area is not electron donor limited, and/or there is minimal or no competition for suitable substrate.
Concentration gradients of both sulfide and methane can be found around whale falls, with the highest concentration coming within one meter of the carcass, which is several orders of magnitude higher than the surrounding sediment concentrations. Methanogenesis appears to only occur in sediments as opposed to sulfur reduction, which occurs both in sediments and on the bones of the carcass.
The addition of sulfur reduction in both sediments and high lipid whale bones is a key factor for why whale falls are able to sustain deep-sea communities for extended periods of time.
Paleontology
Whale fall fossils from the late
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
and
Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
(34–23
MYA) in
Washington
Washington commonly refers to:
* Washington (state), United States
* Washington, D.C., the capital of the United States
** A metonym for the federal government of the United States
** Washington metropolitan area, the metropolitan area centered o ...
and from the
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58[Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...](_blank)
(23–5 MYA) in California and Japan.
This may be because the lipid content of early whale bones was too low.
As prehistoric whales evolved to live in pelagic waters and dive deeper, structural changes in their anatomy included increased size, reduced bone density and higher lipid content.
It is due to this increased lipid content that led to the establishment of chemosynthetic communities in the deep sea.
The discovery of the limpet ''
Osteopelta'' in an Eocene New Zealand turtle bone indicates that these animals evolved before whales, including possibly inhabiting
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
(251–66 MYA) reptiles. They may have survived in seeps, wood-falls and vents while waiting out the 20 million year gap between the reptiles' extinction and whales' emergence. Another possibility is that these fossils represent a prior, dead-end evolutionary path, and that today's whale fall animals evolved independently.
Anthropogenic effects
![Cheynes_whale](https://upload.wikimedia.org/wikipedia/commons/7/77/Cheynes_whale.jpg)
It has been suggested that the
whaling
Whaling is the process of hunting of whales for their usable products such as meat and blubber, which can be turned into a type of oil that became increasingly important in the Industrial Revolution.
It was practiced as an organized industry ...
industry has had an effect on the biological pump through the elimination of many large whales, reducing the amount of whale falls. The effects of this on
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
whale fall community assemblages is not well understood.
However, it is suggested that the removal of large whales might have reduced the total
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
of the deep sea by more than 30%.
Whales stored massive amounts of carbon that were exported to the deep sea during whale fall events. Whaling has thus also reduced the ability of the deep sea to
sequester carbon. Carbon can be sequestered for hundreds to thousands of years in the deep sea, supporting benthic communities.
It is estimated that, in terms of carbon sequestration, each whale is equivalent to thousands of trees.
Contrast with other large food-falls
There have also been studies based on the carcasses of other, non-mammalian marine vertebrates that have fallen to the deep sea. In particular, the chance discovery of a
whale shark
The whale shark (''Rhincodon typus'') is a slow-moving, filter-feeding carpet shark and the largest known extant fish species. The largest confirmed individual had a length of .McClain CR, Balk MA, Benfield MC, Branch TA, Chen C, Cosgrove J, D ...
carcass and three
mobulid
The eagle rays are a group of cartilaginous fishes in the family Myliobatidae, consisting mostly of large species living in the open ocean rather than on the sea bottom.
Eagle rays feed on mollusks and crustaceans, crushing their shells with th ...
ray carcasses led to observations on the communities that form surrounding large
elasmobranch
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gil ...
falls as opposed to whale falls.
Whale sharks inhabit waters of roughly 1,000 meters depth regularly, which suggests it could be a regular form of food fall in areas where it is abundant. Many
eelpout
The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All of the roughly 300 species are marine and mostly bottom-dwelling, some at great depths. Eelpouts are predominantly ...
s (Zoarcidae) were found surrounding the whale shark with some evidence of direct feeding as boreholes were observed on the carcass. Another theory suggests that the eelpouts were waiting for their main prey,
amphipods
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descri ...
and other small benthic animals. The three rays found were at different stages of decomposition, leading to varying assemblages found surrounding the individuals.
A higher abundance of scavengers was found surrounding the more intact individuals, including scavengers typical of whale falls like hagfish. Around the least intact individual a
bacterial mat
A biofilm comprises any Syntrophy, syntrophic Microbial consortium, consortium of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a sl ...
was observed in the zone of enrichment, but no clams or mussels typical of whale falls were seen.
Overall, the four carcasses observed showed no evidence of progression past the scavenger stage. The size limitations, as well as physiological differences between large elasmobranchs and whales more than likely causes the changes observed in the communities surrounding their respective carcasses.
Osedax
''Osedax'' is a genus of deep-sea siboglinid polychaetes, commonly called boneworms, zombie worms, or bone-eating worms. ''Osedax'' is Latin for "bone-eater". The name alludes to how the worms bore into the bones of whale carcasses to reach enc ...
worms have the ability to extract collagen from bones as well as lipids, enabling them to sustain themselves on bones other than the lipid-rich remains of whales. Although no Osedax were found on the non-mammalian remains in this study, their absence may have been due to the timing of observation, and the Osedax had not yet colonized the carcasses.
Various studies on smaller cetaceans and other marine vertebrate food falls come to similar conclusions that these falls bring a large amount of new organic material to depth, but support mostly a scavenger community, as opposed to the diverse assemblage seen at whale falls. This conclusion can be drawn based on the knowledge that large whales have much higher
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
content in their bulk composition and bone marrow, which supports the diverse communities present in succession at whale falls.
Researchers have compared
sauropod
Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...
carcasses to modern whale-fall events, recognizing that sauropods reached the size of modern cetaceans. Sauropod carcasses may have been energy rich reservoirs, and because they did not float great distances, may have been the primary resources of many terrestrial carnivorous dinosaurs.
See also
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Deep sea communities
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Marine snow
In the deep ocean, marine snow (also known as "ocean dandruff") is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to ...
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Detritivore
Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...
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Jelly-falls
Jelly-falls are marine carbon cycling events whereby gelatinous zooplankton, primarily cnidarians, sink to the seafloor and enhance carbon and nitrogen fluxes via rapidly sinking particulate organic matter. These events provide nutrition to be ...
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Whaling
Whaling is the process of hunting of whales for their usable products such as meat and blubber, which can be turned into a type of oil that became increasingly important in the Industrial Revolution.
It was practiced as an organized industry ...
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Osedax
''Osedax'' is a genus of deep-sea siboglinid polychaetes, commonly called boneworms, zombie worms, or bone-eating worms. ''Osedax'' is Latin for "bone-eater". The name alludes to how the worms bore into the bones of whale carcasses to reach enc ...
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Carbon sequestration
Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land ...
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Deep-sea wood
References
External links
Smith and Baco 2003 paper on whale fall ecology (University of Hawaii)
Robin Meadows, "A Whale of a Tale"14 September 2007
{{DEFAULTSORT:Whale Fall
Animal death
Aquatic ecology
Whales