Lake Ecology -- Lake Zones Understanding Lakes A typical lake has distinct zones of biological communities linked to the physical structure of the lake (Figure 10). The littoral zone is the near shore area where sunlight penetrates all the way to the sediment and allows aquatic plants ( macrophytes ) to grow. Light levels of about 1% or less of surface values usually define this depth. The 1% light level also defines the euphotic zone of the lake, which is the layer from the surface down to the depth where light levels become too low for photosynthesizers . In most lakes, the sunlit euphotic zone occurs within the epilimnion . Figure 10 However, in unusually transparent lakes, photosynthesis may occur well below the thermocline into the perennially cold hypolimnion . For example, in western Lake Superior near Duluth, MN, summertime algal photosynthesis and growth can persist to depths of at least 25 meters, while the mixed layer, or epilimnion , only extends down to about 10 meters.

Ultra- oligotrophic Lake Tahoe, CA/NV, is so transparent that algal growth historically extended to over 100 meters, though its mixed layer only extends to about 10 meters in summer. Unfortunately, inadequate management of the Lake Tahoe basin since about 1960 has led to a significant loss of transparency due to increased algal growth and increased sediment inputs from stream and shoreline erosion. The higher plants in the littoral zone, in addition to being a food source and a substrate for algae and invertebrates, provide a habitat for fish and other organisms that is very different from the open water environment. The limnetic zone is the open water area where light does not generally penetrate all the way to the bottom. The bottom sediment, known as the benthic zone , has a surface layer abundant with organisms. This upper layer of sediments may be mixed by the activity of the benthic organisms that live there, often to a depth of 2-5 cm (several inches) in rich organic sediments. Most of the organisms in the benthic zone are invertebrates, such as Dipteran insect larvae (midges, mosquitoes, black flies, etc.) or small crustaceans.

The productivity of this zone largely depends upon the organic content of the sediment, the amount of physical structure, and in some cases upon the rate of fish predation. Sandy substrates contain relatively little organic matter (food) for organisms and poor protection from predatory fish. Higher plant growth is typically sparse in sandy sediment, because the sand is unstable and nutrient deficient. A rocky bottom has a high diversity of potential habitats offering protection (refuge) from predators, substrate for attached algae ( periphyton on rocks), and pockets of organic "ooze" (food). A flat mucky bottom offers abundant food for benthic organisms but is less protected and may have a lower diversity of structural habitats, unless it is colonized by higher plants. THOSE THAT GO WHERE THEY CHOOSE FISH The freshwater biome The freshwater biome A lake at Acadia National Park, Maine. Freshwater is defined as having a low salt concentration  usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean). There are different types of freshwater regions: Ponds and lakes These regions range in size from just a few square meters to thousands of square kilometers.

Scattered throughout the earth, several are remnants from the Pleistocene glaciation. Many ponds are seasonal, lasting just a couple of months (such as sessile pools) while lakes may exist for hundreds of years or more. Ponds and lakes may have limited species diversity since they are often isolated from one another and from other water sources like rivers and oceans. Lakes and ponds are divided into three different zones which are usually determined by depth and distance from the shoreline. The topmost zone near the shore of a lake or pond is the littoral zone. This zone is the warmest since it is shallow and can absorb more of the Sun's heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects, such as dragonflies and midges, only the egg and larvae stages are found in this zone. The vegetation and animals living in the littoral zone are food for other creatures such as turtles, snakes, and ducks. From left: a view across Manzanita Lake toward Mt.

Lassen, California; a forest pond near Donnelly, Idaho; a Great Blue Heron; Paranagat Lake, southeastern Nevada. The near-surface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone. Plankton have short life spans  when they die, they fall into the deep-water part of the lake/pond, the profundal zone. This zone is much colder and denser than the other two. Little light penetrates all the way through the limnetic zone into the profundal zone. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration. Temperature varies in ponds and lakes seasonally. During the summer, the temperature can range from 4° C near the bottom to 22° C at the top.

During the winter, the temperature at the bottom can be 4° C while the top is 0° C (ice). In between the two layers, there is a narrow zone called the thermocline where the temperature of the water changes rapidly. During the spring and fall seasons, there is a mixing of the top and bottom layers, usually due to winds, which results in a uniform water temperature of around 4° C. This mixing also circulates oxygen throughout the lake. Of course there are many lakes and ponds that do not freeze during the winter, thus the top layer would be a little warmer. Streams and rivers These are bodies of flowing water moving in one direction. Streams and rivers can be found everywhere  they get their starts at headwaters, which may be springs, snowmelt or even lakes, and then travel all the way to their mouths, usually another water channel or the ocean. The characteristics of a river or stream change during the journey from the source to the mouth. The temperature is cooler at the source than it is at the mouth. The water is also clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can be found there.

Towards the middle part of the stream/river, the width increases, as does species diversity  numerous aquatic green plants and algae can be found. Toward the mouth of the river/stream, the water becomes murky from all the sediments that it has picked up upstream, decreasing the amount of light that can penetrate through the water. Since there is less light, there is less diversity of flora, and because of the lower oxygen levels, fish that require less oxygen, such as catfish and carp, can be found. From left: McArthur-Burney Falls State Park, California; trout; Green River, Utah; Brooks River, Alaska. Wetlands Wetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs are all considered wetlands. Plant species adapted to the very moist and humid conditions are called hydrophytes. These include pond lilies, cattails, sedges, tamarack, and black spruce. Marsh flora also include such species as cypress and gum. Wetlands have the highest species diversity of all ecosystems. Many species of amphibians, reptiles, birds (such as ducks and waders), and furbearers can be found in the wetlands.

Wetlands are not considered freshwater ecosystems as there are some, such as salt marshes, that have high salt concentrations  these support different species of animals, such as shrimp, shellfish, and various grasses. From left: Pescadero Marsh, California; coastal marsh at Umpqua Dunes, Oregon; trees and bogs on Esther Island, Alaska. Visit our gallery of wetlands images , which illustrate the amazing diversity of wetland ecosystems. Tundra Top photo by David K. Smith, UCMP. Ponds & lakes photos, from left: Glenn and Martha Vargas © 2004 California Academy of Sciences; David K. Smith, UCMP; Gerald and Buff Corsi © 2001 California Academy of Sciences; Glenn and Martha Vargas © 2004 California Academy of Sciences. Streams & rivers photos, from left: Dr. G Dallas and Margaret Hanna © 1999 California Academy of Sciences; Susan Middleton © 2003 California Academy of Sciences; Lorraine Elrod © 2000 California Academy of Sciences; Dr. Robert Thomas and Margaret Orr © 2004 California Academy of Sciences. Wetlands photos, from left: Dr.

Robert Thomas and Margaret Orr © 1999 California Academy of Sciences; David K. Smith, UCMP; Gerald and Buff Corsi © 2005 California Academy of Sciences. What Animals Are in the Intertidal Zone? | Sciencing What Animals Are in the Intertidal Zone? By Joseph Horst crab image by Vaclav Janousek from Fotolia.com The intertidal zone, also known as the littoral zone, is the land on a coastline that is above the water at low tide and underwater at high tide. Animals and organisms that live in the intertidal zone must be adaptable and able to live in a wide variety of temperature, light and tidal conditions. Each vertical zone within the intertidal zone is home to different types of animals. Upper Littoral Also known as the spray zone or the barnacle belt, the upper littoral makes up the highest vertical zone of the intertidal zone. This zone receives a lot of sunlight, but very little water apart from the waves' spray at high tide or during storms. Animals in the upper littoral zone range from barnacles to limpets to lichens.

Upper Mid-Littoral Similar to the upper littoral zone, animals in the upper mid-littoral zone must endure harsh conditions, such as rough waves and hot sunlight. Animals such as the striped shore crab and owl limpet live in this zone and have hard outer shells to protect themselves from the waves. Other animals that live in this zone include anemones, mussels and snails. Lower Mid-Littoral More water covers this part of the intertidal zone, only uncovering the animals and plant life twice a day. Animals that live in this zone are similar to those in the upper mid-littoral zone and include chitons, crabs and limpets. Lower Littoral Animals in the lowest part of the intertidal zone cannot survive in direct sunlight for long. The lower littoral zone gets 90 percent water and 10 percent pure sunshine and holds animals like the two-spotted octopus, the purple sea urchin, which looks like a hedgehog, and the nudibranch. References What animals live in the sublittoral zone? | Reference.com What animals live in the sublittoral zone?

A: Quick Answer The sublittoral zone is home to anemones, crabs, sea stars and coral. The sublittoral zone is another name for the deepest region of the intertidal zone. Full Answer The littoral zone is the region of ocean extending 600 feet out from the shore. Three sub-zones comprise the littoral zone: the supralittoral, eulittoral and sublittoral zones. The sublittoral zone extends to a depth of about 650 feet and is continuously below water. Coral and anemones are more plentiful in the sublittoral zone than in other regions of the intertidal zone because the zone is comparatively more stable in temperature and the amount of sunlight it receives. Sea stars and sea urchins also take advantage of the warm, sunlit waters of the sublittoral zone. On North America's west coast, the dungeness crab is an economically important intertidal resident. These crabs reside in beds of eelgrass on the sublittoral ocean floor, scavenging ocean carrion and preying upon small fish and other crustaceans.

While the dungeness crab is an important food crustacean on the west coast, concerns have arisen about its introduction in the Atlantic and its possible effects on native fauna. Algae and plantlife are also plentiful in sunny sublittoral waters. This provides an excellent food source for much of the intertidal fauna. However, excessive algae and plant material can block sun from the ocean floor and cause overcrowding for other species. animals that live in the littoral zone animals that live in the littoral zone Welcome to our reviews of the animals that live in the littoral zone (also known as oak harbor apartments washington ). Check out our top 10 list below and follow our links to read our full in-depth review of each online dating site, alongside which you'll find costs and features lists, user reviews and videos to help you make the right choice. "animals that live in the littoral zone Rated 4.7/5 based on 416 reviews mensgrayhats Grey Fedora, mens gray dress pants 30x36.

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The aquatic biome can be broken down into two basic regions, freshwater (i.e, ponds and rivers) and marine (i.e, oceans and estuaries). Freshwater Regions Freshwater is defined as having a low salt concentrationusually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e, ocean). There are different types of freshwater regions: ponds and lakes, streams and rivers, and wetlands. The following sections describe the characteristics of these three freshwater zones. Ponds and Lakes These regions range in size from just a few square meters to thousands of square kilometers. Scattered throughout the earth, several are remnants from the Pleistocene glaciation. Many ponds are seasonal, lasting just a couple of months (such as sessile pools) while lakes may exist for hundreds of years or more. Ponds and lakes may have limited species diversity since they are often isolated from one another and from other water sources like rivers and oceans. Lakes and ponds are divided into three different zones which are usually determined by depth and distance from the shoreline.

The topmost zone near the shore of a lake or pond is the littoral zone. This zone is the warmest since it is shallow and can absorb more of the Suns heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects, such as dragonflies and midges, only the egg and larvae stages are found in this zone. The vegetation and animals living in the littoral zone are food for other creatures such as turtles, snakes, and ducks. The near-surface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone.

Plankton have short life spanswhen they die, they fall into the deep-water part of the lake/pond, the profundal zone. This zone is much colder and denser than the other two. Little light penetrates all the way through the limnetic zone into the profundal zone. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration. Temperature varies in ponds and lakes seasonally. During the summer, the temperature can range from 4° C near the bottom to 22° C at the top. During the winter, the temperature at the bottom can be 4° C while the top is 0° C (ice). In between the two layers, there is a narrow zone called the thermocline where the temperature of the water changes rapidly. During the spring and fall seasons, there is a mixing of the top and bottom layers, usually due to winds, which results in a uniform water temperature of around 4° C. This mixing also circulates oxygen throughout the lake. Of course there are many lakes and ponds that do not freeze during the winter, thus the top layer would be a little warmer.

Streams and Rivers These are bodies of flowing water moving in one direction. Streams and rivers can be found everywherethey get their starts at headwaters, which may be springs, snowmelt or even lakes, and then travel all the way to their mouths, usually another water channel or the ocean. The characteristics of a river or stream change during the journey from the source to the mouth. The temperature is cooler at the source than it is at the mouth. The water is also clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can be found there. Towards the middle part of the stream/river, the width increases, as does species diversitynumerous aquatic green plants and algae can be found. Toward the mouth of the river/stream, the water becomes murky from all the sediments that it has picked up upstream, decreasing the amount of light that can penetrate through the water. Since there is less light, there is less diversity of flora, and because of the lower oxygen levels, fish that require less oxygen, such as catfish and carp, can be found. Wetlands Wetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs are all considered wetlands.

Plant species adapted to the very moist and humid conditions are called hydrophytes. These include pond lilies, cattails, sedges, tamarack, and black spruce. Marsh flora also include such species as cypress and gum. Wetlands have the highest species diversity of all ecosystems. Many species of amphibians, reptiles, birds (such as ducks and waders), and furbearers can be found in the wetlands. Wetlands are not considered freshwater ecosystems as there are some, such as salt marshes, that have high salt concentrationsthese support different species of animals, such as shrimp, shellfish, and various grasses. Visit our gallery of wetlands images , which illustrate the amazing diversity of wetland ecosystems. Marine Regions Marine regions cover about three-fourths of the Earths surface and include oceans, coral reefs, and estuaries. Marine algae supply much of the worlds oxygen supply and take in a huge amount of atmospheric carbon dioxide. The evaporation of the seawater provides rainwater for the land. Oceans The largest of all the ecosystems, oceans are very large bodies of water that dominate the Earths surface.

Like ponds and lakes, the ocean regions are separated into separate zones: intertidal, pelagic, abyssal, and benthic. All four zones have a great diversity of species. Some say that the ocean contains the richest diversity of species even though it contains fewer species than there are on land. The intertidal zone is where the ocean meets the landsometimes it is submerged and at other times exposed, as waves and tides come in and out. Because of this, the communities are constantly changing. On rocky coasts, the zone is stratified vertically. Where only the highest tides reach, there are only a few species of algae and mollusks. In those areas usually submerged during high tide, there is a more diverse array of algae and small animals, such as herbivorous snails, crabs, sea stars, and small fishes. At the bottom of the intertidal zone, which is only exposed during the lowest tides, many invertebrates, fishes, and seaweed can be found. The intertidal zone on sandier shores is not as stratified as in the rocky areas.

Waves keep mud and sand constantly moving, thus very few algae and plants can establish themselvesthe fauna include worms, clams, predatory crustaceans, crabs, and shorebirds. The pelagic zone includes those waters further from the land, basically the open ocean. The pelagic zone is generally cold though it is hard to give a general temperature range since, just like ponds and lakes, there is thermal stratification with a constant mixing of warm and cold ocean currents. The flora in the pelagic zone include surface seaweeds. The fauna include many species of fish and some mammals, such as whales and dolphins. Many feed on the abundant plankton. The benthic zone is the area below the pelagic zone, but does not include the very deepest parts of the ocean (see abyssal zone below). The bottom of the zone consists of sand, slit, and/or dead organisms. Here temperature decreases as depth increases toward the abyssal zone, since light cannot penetrate through the deeper water. Flora are represented primarily by seaweed while the fauna, since it is very nutrient-rich, include all sorts of bacteria, fungi, sponges, sea anemones, worms, sea stars, and fishes.

The deep ocean is the abyssal zone. The water in this region is very cold (around 3° C), highly pressured, high in oxygen content, but low in nutritional content. The abyssal zone supports many species of invertebrates and fishes. Mid-ocean ridges (spreading zones between tectonic plates), often with hydrothermal vents, are found in the abyssal zones along the ocean floors. Chemosynthetic bacteria thrive near these vents because of the large amounts of hydrogen sulfide and other minerals they emit. These bacteria are thus the start of the food web as they are eaten by invertebrates and fishes. Coral Reefs Coral reefs are widely distributed in warm shallow waters. They can be found as barriers along continents (e.g., the Great Barrier Reef off Australia), fringing islands, and atolls. Naturally, the dominant organisms in coral reefs are corals. Corals are interesting since they consist of both algae (zooanthellae) and tissues of animal polyp. Since reef waters tend to be nutritionally poor, corals obtain nutrients through the algae via photosynthesis and also by extending tentacles to obtain plankton from the water.

Besides corals, the fauna include several species of microorganisms, invertebrates, fishes, sea urchins, octopuses, and sea stars. Estuaries Estuaries are areas where freshwater streams or rivers merge with the ocean. This mixing of waters with such different salt concentrations creates a very interesting and unique ecosystem. Microflora like algae, and macroflora, such as seaweeds, marsh grasses, and mangrove trees (only in the tropics), can be found here. Estuaries support a diverse fauna, including a variety of worms, oysters, crabs, and waterfowl. The Deep Sea ~ Ocean biology, Marine life, Sea creatures, Marine conservation... ~ MarineBio.org The Ocean / NEXT: Research Tools & Methods » Over 60% of our planet is covered by water more than a mile deep. The deep sea is the largest habitat on earth and is largely unexplored. More people have traveled into space than have traveled to the deep ocean realm.... - The Blue Planet Seas of Life Most people familiar with the oceans know about life only in the intertidal zone, where the water meets land, and the epipelagic zone, the upper sunlit zone of the open ocean.

Though these zones contain an abundance of ocean life because sunlight is available for photosynthesis, they make up only a small fraction of the ocean biome. In fact, most of the ocean is cold, dark and deep. It is important to realize that photosynthesis occurs only down to about 100 - 200 m, and sunlight disappears altogether at 1,000 m or less, while the ocean descends to a maximum depth of about 11,000 m in the Mariana Trench! To get an idea of how vast the ocean's depths are, consider that 79% of the entire volume of the earth's biosphere consists of waters with depths greater than 1,000 m. Until recently, the deep sea was largely unexplored. But advances in deep sea submersibles and image capturing and sampling technologies are increasing the opportunities for marine biologists to observe and uncover the mysteries of the deep ocean realm. Deep sea research is vital because this area is such an enormous part of the biosphere . Despite its depth and distance, it is still our backyard in comparison to outer space.

And yet, human exploration has revealed more detail about the surface of the moon and Mars that it has about the deep sea! Consider that hydrothermal vents and their unique organisms, which revolutionized our ideas about energy sources and the adaptability of life, were only discovered in 1977. There may be yet other life-altering discoveries to be found at the bottom of the ocean. The oceans are divided into two broad realms; the pelagic and the benthic. Pelagic refers to the open water in which swimming and floating organisms live. Organisms living there are called the pelagos.

From the shallowest to the deepest, biologists divide the pelagic into the epipelagic (less than 200 meters, where there can be photosynthesis), the mesopelagic (200 - 1,000 meters, the "twilight" zone with faint sunlight but no photosynthesis), the bathypelagic (1,000 - 4,000 meters), the abyssopelagic (4,000 - 6,000 meters) and the deepest, the hadopelagic (the deep trenches below 6,000 meters to about 11,000 m or 36,000 feet deep). The last three zones have no sunlight at all. Benthic zones are defined as the bottom sediments and other surfaces of a body of water such as an ocean or a lake. Organisms living in this zone are called benthos. They live in a close relationship with the bottom of the sea, with many of them permanently attached to it, some burrowed in it, others swimming just above it.

In oceanic environments, benthic habitats are zoned by depth, generally corresponding to the comparable pelagic zones: the intertidal (where sea meets land, with no pelagic equivalent), the subtidal (the continental shelves, to about 200 m), the bathyal (generally the continental slopes to 4,000 m), the abyssal (most of the deep ocean seafloor, 4,000 - 6,000 m), and the hadal (the deep trenches 6,000 to 11,000 m). There are several types of deep benthic surfaces, each having different life forms. First, most of the deep seafloor consists of mud (very fine sediment particles) or "ooze" (defined as mud with a high percentage of organic remains) due to the accumulation of pelagic organisms that sink after they die. [Unlike the shoreline, sandy habitats are rarely found in the deep sea because sand particles, created by wave action on coral and rocks at shorelines, are too heavy to be carried by currents to the deep.] Second, benthic areas too steep for sediment to stick are rocky.

Rocky areas are found on the flanks of islands, seamounts, rocky banks, on mid-ocean ridges and their rift valleys, and some parts of continental slopes. At the mid-ocean ridges, where magma wells up and pushes seafloor tectonic plates apart, even flat surfaces are rocky because these areas are too geologically new to have accumulated much mud or ooze. Third, in some areas certain chemical reactions produce unique benthic formations. The best known of these formations are the "smoker" chimneys created by hydrothermal vents, which are described in detail below. Exploration of these zones has presented a challenge to scientists for decades and much remains to be discovered. However, advances in technology are increasingly allowing scientists to learn more about the strange and mysterious life that exists in this harsh environment. Life in the deep sea must withstand total darkness (except for non-solar light such as bioluminescence ), extreme cold, and great pressure. To learn more about deep-sea marine life, sophisticated data collection devices have been developed to collect observations and even geological and biological samples from the deep.

First, advances in observational equipment such as fiber optics that use LED light and low light cameras has increased our understanding of the behaviors and characteristics of deep sea creatures in their natural habitat. Such equipment may be deployed on permanent subsea stations connected to land by fiber optic cables, or on "lander" devices which drop to the seafloor and which are later retrieved (typically after a radio command activates the dropping of ballast so the lander may float up.) Second, remotely operated vehicles (ROVs) have been used underwater since the 1950s. ROVs are basically unmanned submarine robots with umbilical cables used to transmit data between the vehicle and researcher for remote operation in areas where diving is constrained by physical hazards. ROVs are often fitted with video and still cameras as well as with mechanical tools such as mechanical arms for specimen retrieval and measurements. Other unmanned submarine robots include AUVs (autonomous undersea vehicles) that operate without a cable, and the USA's new Nereus , a hybrid unmanned sub which can switch from ROV to AUV mode and which is currently the world's only unmanned submarine capable of reaching the deepest trenches. Third, manned deep sea submersibles are also used to explore the ocean's depths.

Alvin is an American deep sea submersible built in 1964 that has been used extensively over the past 4 decades to shed light on the black ocean depths. Like ROVs, it has cameras and mechanical arms. This sub, which carries 3 people (typically a pilot and 2 scientists), has been used for more than 4,000 dives reaching a maximum depth of more than 4,500 m. France, Japan and Russia have similar manned scientific submersibles that can reach somewhat greater depths, while China is currently building one to reach 7,000 m. The bathyscaphe Trieste at the National Museum of the U.S. Navy in Washington, D.C. Until 2012, only one manned submarine device has ever reached the bottom of Mariana trench at almost 11,000 m: the bathyscaphe Trieste manned by Jacques Piccard and Don Walsh. During the Trieste's single dive in 1960, its windows began to crack, and it has never been used since.

52 years later, on March 25, 2012 (March 26 local time) , James Cameron successfully dove in his commissioned one-man sub to the Challenger Deep . Don Walsh was invited to join the expedition. Physical Characteristics of the Deep Sea The physical characteristics that deep sea life must contend with to survive are: abiotic (non-living) ones, namely light (or lack thereof), pressure, currents, temperature, oxygen, nutrients and other chemicals; and biotic ones, that is, other organisms that may be potential predators, food, mates, competitors or symbionts. All these factors have led to fascinating adaptions of deep sea life for sensing, feeding, reproducing, moving, and avoiding being eaten by predators. Light The deep sea begins below about 200 m, where sunlight becomes inadequate for photosynthesis . From there to about 1,000 m, the mesopelagic or "twilight" zone, sunlight continues to decrease until it is gone altogether. This faint light is deep blue in color because all the other colors of light are absorbed at depth. The deepest ocean waters below 1,000 m are as black as night as far as sunlight is concerned.

And yet, there IS some light. People who dive deep in a submersible (with its lights off) are often mesmerized by an incredible "light show" of floating, swirling, zooming flashes of light. This is bioluminescence , a chemical reaction in a microbe or animal body that creates light without heat, and it is very common. And yet, this light is low compared to sunlight, so animals here — as well as those in the mesopelagic zone — need special sensory adaptations. Many deep-sea fish such as the stout blacksmelt have very large eyes to capture what little light exists. Other animals such as tripodfishes are essentially blind and instead rely on other, enhanced senses including smell, touch and vibration.

Scientists think bioluminescence has six different functions (not all used by any one species): headlights, such as the forward-facing light organs (called photophores ) of lantern fish ; social signals such as unique light patterns for attracting mates; lures to attract curious prey, such as the dangling "fishing lures" of anglerfish ; counterillumination, in which rows of photophores on the bellies of many mesopelagic fish produce blue light exactly matching the faint sunlight from above (making the fish invisible to predators below them); confusing predators or prey, such as bright flashes that some squid make to stun their prey, and decoys that divert attention, such as the glowing green blobs ejected by green bomber worms ; and "burglar alarms" in which an animal being attacked illuminates its attacker (the "burglar") so that an even bigger predator (the "police") will see the burglar and go after it. Some swimming sea cucumbers even coat their attackers with sticky glowing mucus so the "police" predators can find them many minutes later. Most bioluminescence is blue, or blue-green, because those are the colors that travel farthest in water.

As a result, most animals have lost the ability to see red light, since that is the color of sunlight that disappears first with depth. But a few creatures, like the dragonfish , have evolved the ability to produce red light. This light, which the dragonfish can see, gives it a secret "sniper" light to shine on prey that do not even know they are being lit up! Pressure Considering the volume of water above the deepest parts of the ocean, it's no wonder that hydrostatic pressure is one of the most important environmental factors affecting deep sea life. Pressure increases 1 atmosphere (atm) for each 10 m in depth. The deep sea varies in depth from 200 m to about 11,000 m, therefore pressure ranges from 20 atm to more than 1,100 atm. High pressures can cause air pockets, such as in fish swim bladders , to be crushed, but it does not compress water itself very much. Instead, high pressure distorts complex biomolecules — especially membranes and proteins — upon which all life depends. Indeed, many food companies now use high pressure to sterilize their products such as packaged meats.

Life appears to cope with pressure effects on biomolecules in two ways. First, their membranes and proteins have pressure-resistant structures that work by mechanisms not yet fully understood, but which also mean their biomolecules do not work well under low pressure in shallow waters. Second, some organisms may use "piezolytes" (from the Greek "piezin" for pressure). These are small organic molecules recently discovered that somehow prevent pressure from distorting large biomolecules. One of these piezolytes is trimethylamine oxide (TMAO). This molecule is familiar to most people because it gives rise to the fishy smell of marine fish and shrimp. TMAO is found at low levels in shallow marine fish and shrimp that humans routinely eat, but TMAO levels increase linearly with depth and pressure in other species. Really deep fish, including some grenadiers which humans are now fishing, smell much more fishy! Animals brought from great depth to the surface in nets and submersible sample boxes generally die; in the case of some (but not most) deep-sea fishes, their gas-filled swim bladder (adapted to resist high pressure) expands to a deadly size.

However, the vast majority of deep-sea life has no air pockets that would expand as pressure drops during retrieval. Instead, it is thought that rapid pressure as well as temperature changes kill them because their biomolecules no longer work well (high TMAO does not help, as it appears to be too high in deep-sea life for biomolecules to work properly at the surface). Advances in deep sea technology are now enabling scientists to collect species samples in chambers under pressure so that they reach the surface for study in good condition. Pressure-adapted microbes have been retrieved from trenches down to 11,000 m, and have been found in the laboratory to have all these adaptations (pressure-resistant biomolecules and piezolytes). However, pressure adaptations have only been studied in animals down to about 5,000 m. We do not yet know if the adaptations found at those depths work at greater depths down to 11,000 m. Temperature Except in polar waters, the difference in temperature between the euphotic, or sunlit, zone near the surface and the deep sea can be dramatic because of thermoclines, or the separation of water layers of differing temperatures.

In the tropics, for example, a layer of warm water over 20°C floats on top of the cold, dense deeper water. In most parts of the deep sea, the water temperature is more uniform and constant. With the exception of hydrothermal vent communities where hot water is emitted into the cold waters, the deep sea temperature remains between about -1 to about + 4°C . However, water never freezes in the deep sea (note that, because of salt, seawater freezes at -1.8°C ). If it did somehow freeze, it would just float to the surface as ice! Life in the deep is thought to adapt to this intense cold in the same ways that shallow marine life does in the polar seas. This is by having "loose" flexible proteins and unsaturated membranes which do not stiffen up in the cold. Membranes are made of fats and need to be somewhat flexible to work well, so you may be familiar with this adaptation in your kitchen. Butter, a saturated fat, is very hard in your refrigerator and would make a poor membrane in the cold, while olive oil — an unsaturated fat — is semi-solid and would make a good flexible membrane.

However, as with pressure, there is a tradeoff: loose membranes and proteins of cold-adapted organisms readily fall apart at higher temperatures (much as olive oil turns to liquid at room temperature). Oxygen The dark, cold waters of much of the deep sea have adequate oxygen. This is because cold water can dissolve more oxygen than warm water, and the deepest waters generally originate from shallow polar seas. In certain places in the northern and southern seas, oxygen-rich waters cool off so much that they become dense enough to sink to the bottom of the sea. These so-called thermohaline currents can travel at depth around the globe, and oxygen remains sufficient for life because there is not enough biomass to use it all up. However, there are also oxygen-poor environments in intermediate zones, wherever there is no oxygen made by photosynthesis and there are no thermohaline currents. These areas, called oxygen minimum zones , usually lie at depths between 500 - 1,000 m in temperate and tropical regions. Here, animals as well as bacteria that feed on decaying food particles descending through the water column use oxygen, which can consequently drop to near zero in some areas. Biologists are still investigating how animals survive under such conditions.

Although most of the deep seafloor has oxygen, there are exceptions in isolated basins with no circulation. Some of these basins that have no oxygen are found at the bottom of the Mediterranean Sea . In 2010, scientists investigating these at 3,000 m depths made a startling discovery: the first known animals to be living continuously without any oxygen. The animals are tiny Loriciferans , members of an animal phylum first discovered in 1983. How they can survive these conditions is not yet known [see Animals thrive without oxygen at sea bottom ]. Food Deep sea creatures have evolved some fascinating feeding mechanisms because food is scarce in these zones. In the absence of photosynthesis, most food consists of detritus — the decaying remains of microbes, algae, plants and animals from the upper zones of the ocean — and other organisms in the deep. Scavengers on the seafloor that eat this "rain" of detritus include sea cucumbers (the most common benthic animal of the deep), brittle stars (seen in the photo above), and grenadier or rattail fish.

The corpses of large animals such as whales that sink to the bottom provide infrequent but enormous feasts for deep sea animals and are consumed by a variety of species. This includes jawless fish such as hagfish , which burrow into carcasses, quickly consuming them from the inside out; scavenger sharks; crabs; and a newly discovered group of worms (called Osedax , meaning bone-eater) which grow root-like structures into the bone marrow! Deep-sea pelagic fish such as gulper eels have very large mouths, huge hinged jaws and large and expandable stomachs to engulf and process large quantities of scarce food. Many deep-sea pelagic fish have extremely long fang-like teeth that point inward. This ensures that any prey captured has little chance of escape. Some species, such as the deep sea anglerfish and the viperfish , are also equipped with a long, thin modified dorsal fin on their heads tipped with a photophore lit with bioluminescence used to lure prey. Many of these fish don't expend much energy swimming in search of food; rather they remain in one place and ambush their prey using clever adaptations such as these lures.

Others, such as rattails or grenadiers (pictured below) cruise slowly over the seafloor listening and smelling for food sources failing from above, which they engulf with their large mouths. Many mesopelagic and deeper pelagic species also save energy by having watery, gelatinous muscles and other tissues with low nutritive content. For example, an epipelagic tuna's muscle (the kind you might eat) may be 20% protein. This makes for a strong, fast muscle, but also takes considerable energy to maintain. In contrast, a deep pelagic blacksmelt or viperfish may have only 5-8% protein. This means they cannot swim as well as a tuna , but they can achieve a larger body size with much less maintenance costs. Some mesopelagic species have adapted to the low food supply (and sometimes to the low oxygen content) in moderate-depth waters with a special behavior called vertical migration . At dusk, millions of lantern fish, shrimp , jellies and other mobile animals migrate to the food-rich surface waters to feed in the darkness of night. Then, presumably to avoid being eaten in daylight, they return to the depths at dawn to digest.

Some of the species undergo large pressure and temperature changes during their daily migrations, but we do not yet know exactly how they cope with those dramatic daily changes. Since plankton is scarce in the deep sea, filter feeding (the most common mode of feeding in shallow waters) is a difficult way to make a living. Consequently, some deep-sea animals belonging to groups once thought to be exclusively filter feeders have evolved into carnivores! One of these is the carnivorous sea squirt Megalodicopia hians . Sea squirts or tunicates are generally harmless filter feeders which draw in microscopic organisms through a siphon tube, but Megalodicopia hians has a huge jaw-like siphon that can rapidly engulf swimming animals! Another of these is the ping-pong-tree sponge, Chondrocladia lampadiglobus. Again, the vast majority of sponges draw in microscopic material through tiny pores, but this sponge has tree-like branches with large glass globes covered in Velcro-like sharp spikes that impale swimming prey!

Submarine canyons provide mixed blessings for seafloor life Other Adaptations of Deep-sea Animals We've described many of the unique adaptations that animals of the deep-sea have evolved to cope with their harsh environment. Let's look at some others, not all of which are fully understood. Body Color: This is often used by animals everywhere for camouflage and protection from predators. In the deep sea, animals' bodies are often transparent (such as many jellies and squids ), black (such as blacksmelt fish ), or even red (such as many shrimp and other squids). The absence of red light at these depths keeps them concealed from both predators and prey. Some mesopelagic fish such as hatchetfish have silvery sides that reflect the faint sunlight, making them hard to see. Reproduction: Consider how hard it must be to find a mate in the vast dark depths. For most deep sea species, we do not know how they achieve this. Earlier we noted that unique light patterns may aid in this. Deep-sea anglerfish may use such light patterns as well as scents to find mates, but they also have another interesting reproductive adaptation.

Males are tiny in comparison to females and attach themselves to their mate using hooked teeth, establishing a parasitic-like relationship for life. The blood vessels of the male merges with the female's so that he receives nourishment from her. In exchange, the female is provided with a very reliable sperm source, avoiding the problem of having to locate a new mate every breeding cycle. Gigantism: Another possible adaptation that is not fully understood is called deep-sea gigantism . This is the tendency for certain types of animals to become truly enormous in size. A well-known example is the giant squid , but there are many others such as the colossal squid , the giant isopod , the king-of-herrings oarfish (which may be the source of sea-serpent legends ), and the recently captured giant amphipod from 7,000 m in the Kermadec Trench near New Zealand. While the giant tubeworms of hydrothermal vents (see below) grow well due to abundant energy supplies, the other gigantic animals live in food-poor habitats, and it is not known how they achieve such growth. It may simply be a result of the feature we examine next: long lives.

Long Lives: Many deep-sea organisms, including gigantic but also many smaller ones, have been found to live for decades or even centuries. Long-lived fishes include rattails or grenadiers and the orange roughy , which are of special concern as they are targets of deep-sea fisheries . These species reproduce and grow to maturity very slowly, such that populations may take decades to recover (if at all) after being overfished . This has happened repeatedly to the orange roughy, a deep-sea fish easily found congregating around seamounts in the southern oceans. Once fisheries have wiped out one seamount population, they move on to another seamount. [see Rough seas for orange roughy: Popular U.S. fish import in jeopardy ] Also of concern with respect to their long, slow lives are a group of animals once thought to be restricted to warm tropical waters: corals . In the last 30 years, numerous cold-water coral species have been found on rocky surfaces throughout the deep sea. These animal colonies may live for centuries, or — amazingly — even millennia. One deep-sea coral colony off Hawaii has been dated at over 4,000 years old, making it older than the Pyramids of Egypt!

[see Deep-Sea Corals May Be Oldest Living Marine Organism ] Again, these corals are highly vulnerable to fisheries as they are easily destroyed by deep-sea trawl nets , and they may take decades to grow back. [see NOAA's Coral Reef Conservation Program: Threats to Deep-sea Corals for more information] Science at FMNH - Exploring Unknown Deep Sea Ecosystems Hydrothermal Vent and Cold Seep Communities Life in the deep sea is relatively sparse compared to the epipelagic (euphotic) and intertidal zones, with two exciting, and relatively recently discovered exceptions — hydrothermal vent and cold seep communities. Hydrothermal Vents These amazing formations were first discovered in 1976 - 77 during a deep sea expedition with Alvin at a mid-ocean ridge near the Galapagos . At that time, only geologists were aboard, with the goal of directly observing seafloor spreading — the mid-ocean ridges being places where magma welling up underneath pushes two tectonic plates apart, creating a rift valley between them.

Some geologists thought there might be geyser-like hot springs, as found in rift valleys on land (such as in Iceland), while others thought that high pressure would prevent such formations. However no one predicted any interesting biology. What they found not only revolutionized geology but biology even more so. These dives to depths of about 2,700 m revealed hot springs of far greater complexity and beauty than anyone had imagined: hot mineral-rich water spewing (like continuous geysers) from vents heated by magma , with metal sulfides precipitating in the cold surrounding seawater to form intricate, colorful and often towering chimneys. Moreover, a completely unexpected community of life was found around these aptly named hydrothermal vents, with not only high densities of numerous new species, but also a new kind of ecosystem flourishing in the dark that had never been imagined by scientists — an ecosystem based on toxic gas! The most amazing of the new species was a giant tubeworm, named Riftia . Growing rapidly in dense clusters, these 2-meter-tall worms were found to have no digestive tract. The revolutionary finding was that they subsist on energy-rich hydrogen sulfide in vent water and generated in the Earth's crust.

Hydrogen sulfide (rotten-egg gas) is normally toxic to animals, but these worms avoid the problem in a spectacular manner. They harbor bacteria known as chemoautotrophs (in a large sac replacing a digestive system), which can use the energy in hydrogen sulfide to convert carbon dioxide into sugars, just as plants do using sunlight. The worm's blood picks up and delivers sulfide, carbon dioxide and oxygen to these bacterial symbionts, which in turn "feed" their hosts with the excess sugars they make (while turning the sulfide into a non-toxic waste product). Thus, the ecosystem was found to run on the Earth's geothermal energy rather than sunlight. Many scientists now think that life on Earth began at such vents over 3 billion years ago. Since those first discoveries near the Galapagos, hydrothermal vent communities have been found at depths ranging from about 1,500 m to over 5,000 m [see Expedition to Mid-Cayman Rise Identifies Unusual Variety of Deep Sea Vents ]. Most vents are along the mid-ocean ridges, where magma is close to seawater.

Other animals with bacterial symbionts have been found, including other species of tubeworms, giant clams and mussels, snails, and shrimp. Undoubtedly many vent communities are yet to be found, since many ridge areas have not yet been explored. The water temperature of vents is much warmer than normal for the deep sea (about 2°C ), reaching as high at 400°C without boiling due to the high pressure. However, nothing can live at such temperatures. The communities of vent life are mostly found between about 8 - 25°C , but may reach perhaps 60°C around some animals such as Pompeii worms (Alvinella) . Though complex life seems not to live at higher temperatures, some archaea have been found living at temperatures of over 120°C ! IMCS Deep Sea Microbiology Lab videos: Black Smoker | Tube Worms | Pompeii Worms | Zoarcid Fish | Crabs Cold Seeps After the first vent discoveries, other unexpected high-density deep-sea ecosystems were found.

Named cold seeps, these occur at places (mostly along continental margins ) where cold methane (which at depths below 500 m forms methane-hydrate "ice"), hydrogen sulfide, and/or oil seep out of sediments to provide abundant energy. By some estimates, there is more energy locked up in the methane hydrates than in all (other) fossil/hydrocarbon fuels combined. Animals with symbiotic bacteria were found, different from but related to vent species, including tubeworms, clams, and mussels. Some mussels harbor methane-using bacteria instead of sulfide-using ones, making ecosystems powered by natural gas! Dense seep communities have also been found around deep brine pools, or "lakes within oceans." These form where salt deposits under the ocean floor dissolve to form pools of water so dense from their salt content that they do not mix with the overlying seawater. So far a few of these have been found in the Gulf of Mexico and the Mediterranean Sea.

At the best-studied brine pool (in the Gulf of Mexico: [see Lakes Within Oceans ] high densities of mussels live around the rim, subsisting (using symbionts) on methane gas seeping from the pool. However, no known animal can survive the salt within the pool itself. Various microbes have been found in the high salt waters, however. In 2012, a new deep-sea ecosystem dubbed a "hydrothermal seep" was discovered off Costa Rica. It is a mosaic of vent and seep communities, with many new species. See the news story " Hot Meets Cold at New Deep-Sea Ecosystem " for more information. References Where aquatic plants grow - Aquatic plant guide: Minnesota DNR Where aquatic plants grow 500 Lafayette Road Box 25 St Paul, MN 55155-4025 tel. (651) 259-5092 Where aquatic plants grow Within a lake or pond, aquatic plants grow in an area known as the littoral zone--the shallow transition zone between dry land and the open water area of the lake.

In Minnesota waters, the littoral zone extends from the shore to a depth of about 15 feet, depending on water clarity. The shallow water, abundant light, and nutrient-rich sediment provide ideal conditions for plant growth. Aquatic plants, in turn, provide food and habitat for many animals such as fish, frogs, birds, muskrats, turtles, insects, and snails. Protecting the littoral zone is important for the health of many of a lake's fish and other animal populations. Aquatic plants are grouped into four major categories: Algae have no true roots, stems, or leaves and range in size from tiny, one-celled organisms to large, multi-celled plant-like organisms, such as chara or muskgrass. Plankton algae, which consist of free-floating microscopic plants, grow throughout both the littoral zone and the well-lit surface waters of an entire lake. Other forms of algae, including stringy filamentous types, are common only in the littoral area. Submerged plants have stems and leaves that grow entirely underwater, although some may also have floating leaves. Flowers and seeds on short stems that extend above the water may also be present.

Submerged plants grow from near shore to the deepest part of the littoral zone (see Figure 1 , below) and display a wide range of plant shapes. Depending on the species, they may form a low-growing "meadow" near the lake bottom, grow with lots of open space between plant stems, or form dense stands or surface mats. Floating-leaf plants are rooted in the lake bottom, but their leaves and flowers float on the water surface. Water lilies are a well-known example. Floating leaf plants typically grow in protected areas where there is little wave action. Emergent plants are rooted in the lake bottom, but their leaves and stems extend out of the water. Cattails, bulrushes, and other emergent plants typically grow in wetlands and along the shore, where the water is typically less than 4 or 5 feet deep. As Figure 1 illustrates, each of the four types of aquatic plants favors a certain water depth. Typically, however, the growth areas are not sharply divided. Expect to see overlap in growth--submerged plants, for example, are often interspersed among floating-leaf varieties. The width of the littoral zone will vary within a lake and among lakes.

In places where the slope of the lake bottom is steep, the littoral area may be narrow, extending several feet from the shoreline. In contrast, if the lake is shallow and the bottom slopes gradually, the littoral area may extend hundreds of feet into the lake or may even cover it entirely. Cloudy or stained water, which limits light penetration, may restrict plant growth. In lakes where water clarity is low all summer, aquatic plants will not grow throughout the littoral zone but will be restricted to shallow areas near shore. Other physical factors also influence the distribution of plants within a lake or pond. For example, aquatic plants generally thrive in shallow, calm water protected from heavy wind, wave, or ice action. However, if the littoral area is exposed to the frequent pounding of waves, plants may be scarce. In a windy location, the bottom may be sand, gravel, or large boulders--none of which provides a good place for plants to take root. In areas where a stream or river enters a lake, plant growth can be variable. Nutrients carried by the stream may enrich the sediments and promote plant growth, or suspended sediments may cloud the water and inhibit growth.

In summary: Where aquatic plants grow and how abundant they are may vary greatly from lake to lake, and even within a lake itself. Qualified lake specialists can help you decide what you should or should not do. DNR regional Fisheries staff can help direct you to available resources and aquatic plant specialists. Connect with us

Question: Where do littoral creatures live?
Answer: Shoreline