The aquatic biomes can be broken down into two different regions:
- Freshwater Regions
- Marine Regions
Freshwater Regions
- Freshwater is defined as having a low salt concentration of less than 1%
- Plants and animals in these areas are adjusted to a low salt concentration, so they would not be able to survive in a place of high salt concentration
- The different types of freshwater regions include (Ponds and lakes, streams and rivers, and wetlands)
Ponds and Lakes
- Ponds and lakes are also seperated. These places are seperated into three different "zones." These zones are determined by depth and distance from the shoreline of greater bodies of water.
Littoral Zone is the topmost zone near the shore of a lake or pond.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, 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 and are 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, so when they die, they fall into the deep-water part of the lake/pond called 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
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 clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can be found there.
- As you move downstream, the water becomes deeper and makes more room for other fish 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.
Marine Regions
- Marine regions cover about three-fourths of the Earth’s surface and include oceans, coral reefs, and estuaries.
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. 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.
- The dominant organisms in coral reefs are corals.
- 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.
Why are these biomes important?
- Water is the basis of life, it supports life, and countless species live in it for all or part of their lives. - Freshwater biomes supply us with our drinking water and water for crop irrigation.
- The oceans contain several billion photosynthetic plankton which account for most of the photosynthesis occuring on Earth. Without these, there might not be enough oxygen to support such a large world population and complex animal life.
Destruction that occurs in Freshwater areas:
- Freshwater biomes have suffered mainly from pollution.
- Runoff containing fertilizer and other wastes and industrial dumpings enter into rivers, ponds, and lakes and tend to promote abnormally rapid algae growth. When these algae die, dead organic matter accumulates in the water. This makes the water unusable and it kills many of the organisms living in the habitat. Stricter laws have helped to slow down this thoughtless pollution.
Destruction in marine regions
- Overfishing and pollution have threatened to make oceans into ecological disaster areas. Industrial pollutants that are dumped upstream of estuaries have rendered many marine habitats unsuitable for life.
- Oil spills are damaging to the marine environment, but yet only make up less than twenty percent of petroleum that enters the ocean.
- Almost forty percent of polluting oil comes from industrial runoff from cities that is carried by rainwater and rivers.
- In coastal regions, excess fertilizer from gardens and farms not only drains into the soil, but it gets carried into the ocean in the same way oil is. This provides an excess in nutrients to the water, which encourages the overgrowth of algal blooms and the process of eutrophication. This deprives the marine biome of its oxygen which in turn, smothers the creatures that live there.
- Offshore Dumping in addition to harmful petroleum and fertilizers, garbage and raw sewage are being disposed of into the ocean every day.
- Internal examinations of whales, sharks, dolphins and other aquatic life, have shown foreign items such as beer cans and plastic garbage bags have been accidentally ingested.
- Many coastal cities around the world empty their sewage into the ocean with little or no treatment at all.
- Human sewage not only contains fecal matter and urates, but also carries harmful bacteria that aren't naturally occurring in the marine ecoystems of the world. Human waste also contains trace amounts of medications and other controlled substances, which add up when combined with large amounts of the toxin-containing wastes.
- All of this is emptied into the ocean in staggering amounts and is destroying the marine environment.
- Tourism at Earth's Expense Cruise ships produce sewage, greywater, oily bilge, air pollutants and other hazardous wastes into the marine atmosphere.
- Though pollution released by freight ships is equally dangerous, the amount of people ordinarily found on cruise ships introduces this toxic combination of pathogens and wastes at higher, more concentrated amounts.
-Overpopulated sea-ports that connect cruise ships to other ports also experience a higher amount of marine pollution.
- Regulations pertaining to offshore dumping only require that cruise lines are a minimum of three miles from land before dumping their wastes into the ocean, and an estimated 175,000 gallons of sewage and other wastes are dumped daily.
- These same regulations allow the disposal of solid garbage materials twelve miles from land.
Why is teaching this important?
By educating people about the consequences of our actions, we can all gain a better understanding of how to preserve the earth’s natural biomes. The areas that have been destroyed the most will never regain their original forms, but conservation will help to keep them from getting worse.
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