Ask a Marine Scientist:

answers to Ecology questions!

Index To Questions

ZONATION

Rocky Shore Zonation Links Rocky Shore Zonation

Animals in the Zones Rivers versus Marine Ecosystems

DEFENSES & INTERACTIONS

Marine Mutualism Marine symbiosis suggestions

Marine Symbiosis Marine Camouflague Symbiotic and parasitic examples

GENERAL MARINE ECOLOGY

Marine Biome Marine Science Definitions Sessile Marine Filter Feeder

Decomposers and Producers Introduced Marine Species in California Vertical migration Ocean Decomposers Effect light removal Oxygen in seagrass beds

ZONATION

Rocky Shore Zonation Links - Received from Mark in England

Q. I would like information please about WWW links specific to rocky shore zonation. My searches so far seem to have been quite unsuccessful.

A. Thanks for your question. I don't know of any WWW sites that are as specific as you are asking. As you may have already found out, there are many things that are simply not to be found in the WWW. (exaggerated media stories to the contrary).

For a topic like rocky shore zonation, there is nothing that can beat a good marine ecology textbook. Usually, public libraries don't have textbooks like this, but if there is a university or college library nearby, you should try that.

Try looking for:
Barnes, R.S.K and R.N. Hughes 1982. An introduction to marine ecology. Blackwell Scientific Publications, London.
It has an entire chapter devoted to rocky shores.

Good Luck!

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Rocky Shore Zonation (Received from Alex Ford in U.K.)

Q: What would you say has the main effect of zonation on rocky shores, physical or biological effects.

Both physical and biological factors are important in determining zonation on rocky shores. In general, physical factors such as desiccation (drying out), temperature and solar radiation are important in setting the upper limit of where plants and animals live on the shore. Biological factors, such as competition and predation tend to set the lower limits of where organisms live on the rocky shore.

To explore this further, we can use a common rocky shore animal like a barnacle as an example. If you visit a rocky intertidal shorline during low tide, you'll likely see a white "strip" of barnacles. There is a fairly well defined upper line where no barnacles are found, and a lower line where they are also absent. The reasons that barnacles cannot live higher up the shore are mainly physical in nature. If a barnacle larvae settles on the rocky shore too high up, it will not be covered by the incoming tide very often. It will be stressed by drying out, and by overheating in the sun, and will likely die. Thus, the upper limit of the barnacles is set by physical factors. Lower down in the intertidal there are many predators on barnacles. These predators would include whelks, starfish, and other carnivores. These predators eat any barnacles that are unfortunate enough to settle too low in the intertidal zone, and therefore establish the lower limit of barnacle settlement. If predators are excluded from a low intertidal area, barnacles can flourish - it is not that they cannot live there due to physical factors, but they are prevented from living there by predation. Competition with other aminals is also involved in setting the lower limits of where barnacles live.
Answered with the assistance of Dr. Thomas Carefoot

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Animals in the Zones - Received from Kim in South Africa

Q: What creatures live in the photic zone, sublittoral zone and intertidal zone (specifically in South Africa)? I need specific animals please. Otherwise, where can I find this kind of info on the Internet?

A. The photic zone is the layer of water into which the sun can penetrate. In most cases the average depth of the photic zone is usually about 100m below the surface. If the water is murky, the photic zone will be more shallow; if the water is clear it will extend deeper. Since sunlight penetrates the photic zone, microscopic, photosynthetic organisms called phtyoplankton can grow and live there. Animals such as euphausids, copepods, crab larvae, fish larvae and other forms of zooplankton that feed on the phytoplankton are often found in the photic zone. At night time, shrimp and other animals will surface to the photic zone to feed on the krill under the mask of darkness. A variey of different kinds of fish species (schooling fish like herring, pilchards, sardines, etc..) can also be found in the photic zone, feeding on the plankton.

The sublittoral zone is the area below the lowest of the spring tides. Basically, sublittoral refers to anything below the littoral zone, which is the area of the shore bounded by the highest and lowest of the spring tides. There are a variety of animals that live in the sublittoral zone. The large kelps, such as the bladder kelp, Nereocystis sp., and the giant kelp, Macrocystis sp., are often found in this zone. The kelps host a variety of other organisms, including kelp crabs, decorators crabs, kelp greenlings,large anemones, rockfish, many species of nudibranch, bryozoans, and others. Exposed rocky areas will often have sea urchins as well. Along sandy stretches of the shore you may find animals such as sea pen and sand dollars. Many of the larger rhodophytes (red algae) are only found in the sublittoral zone.

The intertidal is host to a whole series of animals, and almost every invertebrate phyla is represented in one form or another. I'll leave this part up to you - there are many books about the intertidal zone and the creatures that live there.

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Rivers versus Marine Ecosystems

Q: What are some of the possibilities he rate of primary consumer production NOT sufficient to satisfy the rate of carnivore consumption?

A: There are many reasons why primary consumer production may not be enough for carnivores. River eco-systems are subject to high levels of disturbance from altered water flows, temperature variations (within the river and day to day), pollution concentrations, seasonal variations and so forth. Within this ecosystem the primary producers are hard pressed to produce at a steady stable level. Sometimes they produce more and sometimes they produce less than whats needed for carnivore consumption.
In a comparison the ocean production levels are much more stable as the oceans are not subject to the same variations that the rivers are.

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DEFENSES & INTERACTIONS

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Seminar suggestions for marine symbiosis - Received from Helen in California

Q: I would appreciate some suggestions for my situation. I have to do a seminar in two of my classes this semester and I don't know what I'm going to do them on. I need to find a topic for a Marine Symbiosis and Biology of Algae seminar. I would prefer to combine the topic into the two seminars. A few topics that are being discussed in seminars to come are Hydrothermal Vents and Nudibranchs. I was thinking about doing the symbiosis of Clown Fish and Sea Anemones, but thought that would be too general. If you have any suggestions they would be greatly appreciated. My first seminar is on May 8, 1997 and the next one
is on May 20, 1997. Thank you for your response.

A. Dear Helen: It seems to me that if you want to combine marine symbiosis and biology of algae, the classic topic would be zooxanthellae in coral. As you should know from your classes,
zooxanthellae are single celled organisms that contain chloroplasts and two flagellae. They are in a group of animals called dinoflagellates, most of which are free living members of the phytoplankton. In the case of zooxanthellae, however, they live within the tissues of animals, particularly stony corals. The corals depend on the photosynthetic activity of the zooxanthellae for much of their energy requirements, and in return, they provide a safe place for the zooxanthellae to live. This is a well studied relationship, and you should be able to find a great deal more information about it from your textbooks and articles in the library. Good Luck!

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Marine Symbiosis (received from Simon in Colorado)
Q: I am interested in an interesting example of symbiosis in the
marine environment. Also sources easily attainable that support this
system would be appreciated.

A. One excellent example of marine symbiosis is that which exists between certain cnidarians and the zooxanthellae algae that inhabit them. Over 60 genera of corals contain these zooxanthellae, including virtually all of the reef building corals. They are also in sea anemones such as Anthopleura xanthogrammica, which can be found on the west coast of North America.
The nutritive needs of the corals are supplied partly by food captured with their tentacles, and partly by the photosynthetic efforts of the zooxanthellae. The symbiosis also helps with the deposition of the calcium carbonate that forms the coral skeleton, as the algae removes carbon dioxide from the system. The algae benefits from the system by getting protection from the coral or anemone - since it is housed within the animals tissues, it cannot be eaten by herbivores.

More information about the zooxanthellae - cnidarian symbiosis is available in almost any invertebrate textbook, and many detailed scientific papers have been published on the topic in recent years. Books on corals and coral reefs will also contain this information.

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Marine Camouflague - Received from Brandon in Oregon

Q: Can you tell me all the types of different senses that exist in the underwater world and their advantages/disadvantages are or how a prey can be "camoflauged" sort of from that sense so they can't be found? For example, some sharks can sense fish by thier electrical fields. But is there a way to hide their electrical field?

A. Many of the sensory systems that are observed in terrestrial systems have an equivalent in the oceans. Many of the ocean's inhabitants have reduced vision, though (except for Cephalopods, which have remarkably good vision). Many of the cetaceans have extraordinary echolocation sensory systems, and since sound travels faster and farther in water, it makes sense that this would be so.

Chemoreception is an important sense in the marine environment. Chemicals are constantly being secreted by marine animals, for a variety of purposes, including defense, mate attraction, etc.. Nudibranchs (sea slugs, a type of mollusc) sequester chemicals from their prey (sponges) and use these chemicals for defense. When a fish or other predator grabs a nudibranch, the foul taste tends to deter the fish from consuming the animal. Nudibranchs have also been found to use chemicals as a form of camouflage, secreting substances into the water to mask their presence. Often the chemicals mimick some other type of organism, such as the sponge they are feeding on, or some other type of benthic animal.

Hagfish, along with many other marine fishes, secrete large quantities of mucous, which is believed to deter other animals from feeding on them. The mucous may also allow the hagfish to escape if it is caught (most animals do not like a mouthful of slime). The use of mucous for defensive purposes is rather common among other marine lifeforms as well.

Crypsis in the form of coloration is also a common theme in the underwater world. Many animals are colored in a way that helps them to blend in with their environment. Many species of fish are colored in such a way that they blend in very well with the bottom. Many of the flatfish such as flounder and sole can hardly be distinuished from the sandy bottoms that they live on. Nudibranchs often assume the colour of the animal that they feed on, and they do so by retaining pigments aquired from their prey. Tidepool sculpins often conform with the predominant color in a tidepool. They have the ability to change colours, and will often do so if they are alarmed by a predator. Many of the Cephalopoda have the ability to change their colour at will, too. These animals have specialized organs called chromatophores, which can be used to change the colour of the organism instantaneously.

Most predatory fishes use some form of electroreception to detect their prey. However, many of those prey species also have electroreception capabilities that can be used to detect predators. Sharks are very effective predators, but they certainly do not always get their dinner on time. Attacks on prey are not always successful, and the lack of success can often be attributed to the escape response of the prey. Some species of fish have remarkable escape responses. Reef fishes in particular have very interesting escape behaviours. Some retreat to crevices in the reef when they feel threatened by their surroundings. Many reef species are also hide at night when many of the predacious fishes are foraging.

The electrical fields that are generated by fish orginate from the muscle tissue, and is the result of muscular contractions as they move through the water. I think that for many fish species, it would be difficult to mask the electromagnetic fields being generated. Some form of movement is necessary to maintain the flow of water over the gills, either through forward locomotion or some form of gill ventilation. Seeking cover, either in a rock crevice, among kelp, or some other form of protective structure, is probably the best strategy for evading predators and concealing the electric field. I know that electric rays, which are capable of generating exceptionally large electric fields (~200V) have rather thick insulating layers of skin. This insulating layer may help the animal mask the electromagnetic fields that it generates during movement and from its electroplaques.

There are numerous other examples of the use of crypsis and camouflage in the marine environment. Bioluminesence is an interesting phenomenon that some scientists believe may be used as a form of crypsis. There is still a lot of discussion (disagreement and conflicting theories) about the purpose and possible advantages of light production in marine organisms.

I hope this answers some of you questions.

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Symbiotic and parasitic examples - received from Billy in California

Q: Could you please give me some examples and pictures of ocean creatures who have symbiotic and parasitic relationships?

A: Here are some examples of symbiosis:

1. Shrimp and anemones. On example from the Pacific is the association of the shrimps Heptacarpus kincaidi and Lebbeus grandimanus with anemones of the Urticina genus. Typically, the shrimp are more closely associated with the anemones during the day than at night. It is believed that the shrimp associate with the anemones primarily for protection against predators.
2.A great marine example of mutualism is the relationship between large reef fish and the cleaner fish that keep them free of parasites (one partner gets food, the other gets a clean!)
3. Another example is the relationship between the clown fish and sea anemones (Actinia and Stoichactis). The clown fish brings food to the anemones, while the stinging tentacles of the sea anemones deter predators from approaching the clown fish.
4.Cnidarians and the zooxanthellae algae that inhabit them: over 60 genera
of corals contain these zooxanthellae, including virtually all of the reef building corals. The nutritive needs of the corals are supplied partly by food captured with their tentacles, and partly by the photosynthetic efforts of the zooxanthellae. The symbiosis also helps with the deposition of the calcium carbonate that forms the coral skeleton, as the algae removes carbon dioxide from the system. The algae benefits from the system by getting protection from the coral or anemone - since it is housed within the animals tissues, it cannot be eaten by herbivores.

Here are some examples of parasitic relationships:

1. Angler fish: In these fish, the male has become a tiny parasite that attaches to and lives on the female, near her genitals.
2. The snail tentacle parasites: are members of the genus Leucochloridium. They are Digeneans (Platyhelminthes) and use snails as intermediate hosts. Inside this host, larvae of the worm develop into large sack-like structures filled with metacercariae (another larval stage). These sacs pulsate and eventually attract birds which eat them. The larvae then leave the tissues of the snail and take up adult residence in the bird. They are not highly pathogenic and are a normal part of many north american woodland habitats.
3. Gray whales are covered with skin parasites! Whale lice (cyamids-actually tiny crustaceans) and barnacles both hitch a free ride. Barnacles eat plankton and food scraps. Whale lice are parasites that eat whale skin and damaged tissue.

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GENERAL

Q: What types of animals live in the pacific ocean? Is an ocean a biome?

A: Check out the OceanLink website to discover the huge diversity of animals that live in the Pacifc ocean and other oceans. The entire website is dedicated to the marine biome. A biome is a geographically area that supports a community of similiar plants and animals that are adapted to similar environmental conditions. A biome is the largest geographical biotic unit and is named after the dominant type of vegetation, such as a coral reef or a kelp forest. Therefore there are many different biomes found in the ocean and the OceanLink website is a great place to explore the marine biome.

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Marine definitions and examples (received from Joseph in Georgia, USA)

Q. : Could you give examples of the following terms in relation to the ocean
1.Producers;organisms that make food
2.Consumers;organisms that eat producers
3.Autotrophics;makes food from inorganic matter
4.Heterotrophs;organisms that cannot make own food
5.Decomposers;organisms that break down organic matter for food
6.Plankton;Tiny plant like organisms
7.Nekton;controll location by swimming
8.Benthos;Plants and anamials that live on the floor of the ocean
Thank you, this is for my 8th grade report in science Please keep it simple to understand

A. Examples
1. Producer: Another term for autotroph (see below)

2. Consumer: Another term for heterotroph (see below)

3. Autotroph: A species that uses chlorophyl to capture the sun's light and make organic molecules would fit this category, for example any species of algae (also called seaweed). Sea Lettuce, known as Ulva, is a common species of green seaweed found on most shores. Recently, deep sea animals have been found near hydrothermal vents on the ocean floor. Many of these animals do not have a mouth or gut - instead they reley on a "chemosynthetic autotrophic bacteria" for their food. These bacteria are autotrophs, but they do not get their energy from the sun - instead, they derive energy from the energy rich sulfer compounds that spew out of the hot vents.

4. Heterotroph:.Organisms that rely on Autotrophs to create organic molecules. Any animal that you can think of would be a heterotroph, such as fish, whales, crabs, sea stars, tubeworms, etc. etc.

5. Decomposer: Decomposers do not create their own organic molecules, so they are a type (subset) of heterotrophs. Bacteria are major decomposers, and exist in all marine environments as well as terrestrial ones. Marine bacteria help to cycle dead organic material back into the marine food webs.

6. Plankton: Any plant or animal that cannot swim against a current can be defined as plankton. Although many types of plankton are microscopic, plankton does not have to be tiny - some large jellyfish cannot swim against the currents that they live in, and can therefore be defined as plankton. Many larval stages of common animals, such as crabs, barnacles, worms, sea stars, snails, etc. can be found wandering in the water column as plankton. Other animals, such as copepods and krill (related to shrimp) spend their entire lives as part of the plankton. Bacteria and algae can also be part of the plankton.

7. Nekton: Anything that can swim against a current could be defined as Nekton. If you can swim, you could be part of the Nekton. Of course, if you don't swim very well, and just float around with the current, then you'd be plankton! Examples of Nekton include most fish in the ocean (though larval fish are often part of the plankton!), as well as other strong swimming animals like squid, whales, seals, and turtles.

8. Benthos: Benthic animals and plants live on the ocean floor. Adult crabs, sea stars, and barnacles are part of the benthos, as well as marine snails, clams, sea anemones, corals, and many other animals. Red, green and brown algae are part of the benthos, since they are usually attached to rock or sand. (One notable exception is a species of algae, Sargassum, that floats with the current in the Sargasso sea. It would be considered to be plankton).

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Decomposters and Producers - Received from Osvaldo in California.

Q: What are some aquatic decomposers??? What are someaquatic Producers???

A: A decomposer is an organism that breaks down dead organicmaterial into inorganic forms, while a producer builds organicmaterials from inorganic substances. In the oceanic environment, the major primary producers are phytoplankton. These microscopic organisms convert inorganic molecules and the sun's energy into biomass via photosynthesis. Diatoms (Class Bacillariophyceae) are some of the best known species of planktonic algae. They are
unicellular, with cell size ranging from 2 to 1000 micrometers, although some species form long chains. All diatoms have an external skeleton composed of silica, which is called a frustule. Diatoms and other types of phytoplankton are consumed by herbivorous zooplankton, such as protozoans, copepods and larvaceans. For more information and pictures of diatoms, see "Diatoms: Nature's Gems".

The major decomposers in marine ecosystems are bacteria. This decomposition releases inorganic forms of essential elements (such as nitrogen, phosphorus and carbon) back into the ecosystem, where they are available for use by autotrophs (photosynthetic organisms). In addition to microbial decomposers, scavenging organisms also recycle detritus either in the water column or the benthos (sea floor). Examples of benthic scavengers include sea cucumbers (Class Holothuria), polychaete worms (Class Polychaeta) and fiddler crabs (Uca sp.).

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Introduced Marine Species in California -Received from Eric in Iowa

Q: Hi I am a bioilogy student from Iowa and I have to do a report on the influx of forienge species on the California coast. Can you please tell me at least a page worth of information on this subject? Thanks.

A. Hello Eric:
We're assuming that you are a biology (not bioilogy) student, and you are interested in foreign (not forienge) species. We're also not sure where you got the impression that we'll write your whole report for you!!!!! We'll give you a start, but the rest of the research and writing is up to you!!!!

The "foreign" species that you're interested in are more commonly called "introduced" species. One common animal that was introduced to the California coast is the Atlantic oyster, (latin name Crassostrea virginica). When this was introduced, many animals were also brought along, "piggybacking" on the oyster shells, including the barnacles, Balanus amphitrite and Balanus improvisus, as well as the Bryozoans Schizoporella unicornis and Schizoporella errata, along with hundreds of others.

If you look for more information about these animals in California, particularly the Atlantic Oyster, you should find lots of stuff. If you use the Latin names to search with, it will make your job much easier!

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Sessile Marine Filter Feeder - Received from Lancy in Ontario, Canada

Q: Can you tell me what is "sessile marine filter feeders"?

A: First the word "sessile" means an animal that does not move, but stays in one spot. The animal is usually attached to a rock or some other substrate on the bottom of the ocean. "Marine" means lives in a salt water environment, like the ocean for example. A "filter feeder" is an animal that feeds on tiny plants and animals (plankton) that are suspended (floating) in the water. An example of a "sessile marine filter feeder" is a barnacle. A barnacle is a type of crustacean (related to crabs and shrimps) that is permanently attached to a substrate, usually a rock, and never moves from where it is permanently attached. Their soft body parts are completely enclosed in calcareous exoskeleton (skeleton on the outside). They have a "door" that they can open and extend specialized feeding appendages out into the water to "grab" (filter feed) out tiny plankton from the water column.

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Vertical migration - received from Rolando in Toronto, Ontario

Q: Can you tell me if the animals the live in the deep end of the ocean raise to the surface once night falls? Thank you

A: Thanks for your question!
There are many plankton that live in the water column that migrate up near the surface at night and then drop down from 100 to 1000 m below the surface during the day. This behaviour is thought to help them avoid predators.
There are predatory fish that follow the daily migration of the plankton, so they also live in the deep during the day and up near the surface at night.

This kind of migration is called vertical migration.

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Ocean Decomposers - received from TomVanner in Portsmouth.

Q: Can you please tell me the names of five decomposers?

A: Decomposers are essential in nutrient recycling in food web, so good question! I will give you examples of decomposers that are all active and important in the marine environment:

1. Fungi: the study of marine fungi is an up and coming science. In January of 2000, they announced the discovery of 2 new genera of marine fungus: Lulworthia and Lindra both of which are estuarine seaweed decomposers.
2. Shipworms: these are molluscs in the family Teredinidae, they bore through wood leaving calcium deposits and decomposing the wood.
3. .Bacteria: such as Vibrio furnissii, which breaks down chitin a major component of arthropod shells (such as crab and lobster shells).
4. .Meiofauna: like nematodes (flatworms) that eat seaweed washed up on shore.
5. .Microbes: like amoebas, flagellates, ciliates, diatoms that all breakdown plant and animal material.
   

Effect of light removal - received from Josie in Northridge, California

Q: What affect does the removal of light have on aquatic ecology?

A: Removing light from any biological system has drastic effects on its processes. Ultimately the energy for all life forms comes from light. Primary producers (plants or algae) cannot photosynthesize without light. If there is no photosynthesis the producers are not creating any sugars. Allthe animals that depend on plants or algae as a food source would die and all the animals that depend on those animals would die too. Ultimately removing light form a system would topple the trophic pyramid of interactions and the ecosystem would fall apart.

The only ecosystems that are not dependent on light are chemosynthetic systems. Organisms that lvie in environments where there is no light like the deep sea floor have found a way to create energy without light. They use hydrogen sulfide to produce energy. The chemosynthetic baceteria that is the base of the deep sea trophic system oxidizes these sulfides and are able to fix carbonfrom carbon dioxide into organic sugars to use as energy sources.

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Oxygen in seagrass beds - received on from Austin in Miami, Florida

Q: Could you please tell me some general info about oxygen levels in seagrass communities?

A: The sea grasses are flowering (higher) plants that grow in the shallow waters of quiet bays. Their maximum depth is determined by how far light can penetrate into the water column (hence why they exist mostly in shallow waters). Many of the 100 or so species of sea grass grow in thick beds that provide habitat for many other living things including clams, snails, fish and aquatic reptiles. These communities are among the most productive marine communities.

The oxygen in sea grass beds comes from the atmosphere and from the seagrass itself. Since sea grass beds are restricted to shallow water where light is high, we can assume dissolved oxygen is also fairly high. What consumes the oxygen? All living things that exist in the community. The sea grass, the fish, the bacteria. the snails etc, and all the other invertebrates that live in the sea grass bed.

What is able to live at different oxygen levels? This is a tougher question. Oxygen is required by all living organisms to oxidize energy-yielding compounds. Generally speaking, oxygen consumption increases with increasing body size and with increasing activity levels. Therefore sessile creatures like sponges and bivalve molluscs consume far less oxygen than fish or swimming crustaceans. There are some organisms that can survive in places with little or no oxygen. Anaerobic organisms like some protists and bacteria can live in very low oxygen levels. Most marine organims have some adaptations to deal with low oxygen levels. For example, invertebrates living in the intertidal who rely on oxygen in the water column are oxygen deprived during low tide. They revert to lower efficiency anaerobic metabolic pathways (energy use without oxygen) to respire. However, motile organisms have to option of moving to an area of higher oxygen and this is usually what they do. Usually animals are adapted to have low respiration rates (low activity levels) in low oxygen environments and increase their oxygen consumption as it becomes available. They can store up oxygen reserves is tissues and blood. Oxygen-carrying components in the blood of organisms allow animals to hold high levels of oxygen in their blood in times when oxygen in the environment is too low.

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