Chapter 5 -BIOMES

Biomes are climatically and geographically defined areas of ecologically similar climatic conditions such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Biomes are defined by factors such as plant structures (such as trees, shrubs, and grasses), leaf types (such as broadleaf and needleleaf), plant spacing (forest, woodland, savanna), and climate. Unlike ecozones, biomes are not defined by genetic, taxonomic, or historical similarities. Biomes are often identified with particular patterns of ecological succession and climax vegetation.

The biodiversity characteristic of each biome, especially the diversity of fauna and subdominant plant forms, is a function of abiotic factors and the biomass productivity of the dominant vegetation. In terrestrial biomes, species diversity tends to correlate positively with net primary productivity, moisture availability, and temperature.

A fundamental classification of biomes is into:

1. Terrestrial (land) biomes
2. Freshwater biomes
3. Marine biomes

Biomes are often known in English by local names. For example, a Temperate grassland or shrubland biome is known commonly as steppe in central Asia, prairie in North America, and pampas in South America. Tropical grasslands are known as savanna in Australia, whereas in Southern Africa it is known as veldt (from Afrikaans).

Terrestrial biomes include

• tundra
• taiga
• temperate deciduous forest
• scrub forest (called chaparral in California)
• grassland
• desert
• tropical rain forest
• temperate rain forest

The distribution of biomes as to annual precipitation and average temperature

Freshwater Ecosystems

Only 1-3% of the world's water is fresh. And 99% of this is either frozen in glaciers and pack ice or is buried in aquifers. The remainder is found in lakes, ponds, rivers, and streams.

Lakes and Ponds

Deep lakes contain three distinct zones, each with its characteristic communities of organisms.

Littoral zone

The zone close to shore. Here light reaches all the way to the bottom. The producers are plants rooted to the bottom and algae attached to the plants and to any other solid substrate. The consumers include:

• tiny crustaceans
• flatworms
• insect larvae
• snails
• frogs, fish, and turtles.

Limnetic zone

This is the layer of open water where photosynthesis can occur. As one descends deeper in the limnetic zone, the amount of light decreases until a depth is reached where the rate of photosynthesis becomes equal to the rate of respiration. At this level, net primary production no longer occurs.
The limnetic zone is shallower is turbid water than in clear and is a more prominent feature of lakes than of ponds.

Life in the limnetic zone is dominated by

• floating microorganisms - called plankton


• actively swimming animals - called nekton.

The producers in this ecosystem are planktonic algae.
The primary consumers include such animals as microscopic crustaceans and rotifers - the so-called zooplankton.
The secondary (and higher) consumers are swimming insects and fish. These nekton usually move freely between the littoral and limnetic zones.

Profundal zone

Many lakes (but few ponds) are so deep that not enough light reaches here to support net primary productivity. Therefore, this zone depends for its calories on the drifting down of organic matter from the littoral and limnetic zones.

The profundal zone is chiefly inhabited by primary consumers that are either attached to or crawl along the sediments at the bottom of the lake.

Such bottom-dwelling animals are called the benthos.

The sediments underlying the profundal zone also support a large population of bacteria and fungi. The decomposers break down the organic matter reaching them, releasing inorganic nutrients for recycling.

Rivers and Streams

The habitats available in rivers and streams differ in several ways from those in lakes and ponds.
Because of the current, the water is usually more oxygenated.
Photosynthesizers play a minor role in the food chains here; a large fraction of the energy available for consumers is brought from the land; e.g., in falling leaves.

Rivers are flowing bodies of waters. There are rivers on every continent (except Antarctica). Rivers are an important part of the Earth's water cycle and the sculpting of the Earth's topography as they carry huge quantities of water from the land to the sea.

MARINE ECOSYSTEM

Marine ecosystems are a part of the largest aquatic system on the planet, covering over 70% of the Earth's surface. The habitats that make up this vast system range from the productive nearshore regions to the barren ocean floor. Some examples of important marine ecosystems are:

• Oceans
• Estuaries and Salt Marshes
• Coral Reefs and Other Tropical Communities (Mangrove Forests)
• Coastal areas like Lagoons, Kelp and Seasgrass Beds and Intertidal systems (rocky, sandy, and muddy shores)

Marine ecosystems are home to a host of different species ranging from tiny planktonic organisms that comprise the base of the marine food web (i.e., phytoplankton and zooplankton) to large marine mammals like the whales, manatees, and seals. In addition, many fish species reside in marine ecosystems including flounder, scup, sea bass, monkfish, squid, mackerel, butterfish, and spiny dogfish. Birds are also plentiful including shorebirds, gulls, wading birds, and terns. Some marine animals are also endangered including whales, turtles, etc. In summary, many animal species rely on marine ecosystems for both food and shelter from predators.

Marine ecosystems contain several unique qualities that set them apart from other aquatic ecosystems, the key factor being the presence of dissolved compounds in seawater, particularly salts. This total gram weight of dissolved substances (salts) in one kg of seawater is referred to as salinity. In general 85% of the dissolved substances are Sodium (Na) and Chlorine (Cl) in seawater. On average seawater has a salinity of 35 parts per thousand grams (ppt) of water. These dissolved compounds give seawater its distinctive "salty" taste, affect species composition of particular marine habitats, and prevent oceans from freezing during the winter.

Open oceans

Open oceans (Pelagic) represent the largest area and volume of marine ecosystems, although their biological and fisheries production per unit of area is far less than the other ecosystems. The depth of open oceans varies from about 200m, where in theory the continental shelf ends and the continental slope starts, to 11 500m in the deepest trenches.

Coral reefs are the dominant type of ecosystems in tropical areas with low upwelling or freshwater inputs. Coral reef ecosystems occur in areas where sunlight can reach reef-building corals on solid surfaces and stable sediments. They are fragile, vital for island countries, richest in biodiversity and heavily impacted by inland runoffs and inland activities (e.g. deforestation or inappropriate agricultural practices). Coral reefs are particularly sensitive to destructive fishing methods using explosives and poisons. They are mainly used by artisanal fisheries.

In the warm, shallow waters around the islands, we find the corals and the coral reefs. Corals are micro organisms, so, they are the smallest animals you can imagine. These 'microscopic small' organisms produce (secrete) lime which form miniscule small holes (cavities). These miniscule small holes serve as their living room. The corals use their tentacles to trap passing plankton. Plankton is the food for corals. As generations of corals die, the lime skeletons of the dead micro organisms will build-up the coral reefs. It takes a coral reef 5 years to grow one inch. The forms of the reefs we can see today, are the result of a natural process of millions of years. These limestone forms are the environment (the habitat) for the many different en coloured tropical fish.

Marine bio-diversiy

The coral reefs in the Western Pacific have the highest marine biodiversity in the world. In the waters of the Philippines there are more than 2000 different kinds of fish. This area is one of the most unique in the Pacific Ocean. The coral reefs are very beautiful, ideal for divers and snorkelling tourists. Moreover, they also protect the shoreline by acting as a wave breaker.

Threats for the coral reefs?

Its very sad that many coral reefs have been damaged in the past by fishermen. Many fishermen used cyanide and dynamite to get fish in a more easy and fast way. To use the cyanide was an effective way not to kill but paralyze (put them to sleep) the fish for some time. It was then easy to collect the fish in a relative short time. The fish was sold to traders. Using the dynamite by the fishermen caused a lot of damage to coral reefs

WETLANDS

Wetlands are defined as land areas that are at least partially covered with water for all or part of the year. Wetlands are wet, of course! There are many different types of wetlands each with its own characteristics. They serve many roles and functions and are full of life!

There are many different types of wetlands found throughout the world. They are found everywhere in the world except Antarctica. Wetlands all have common characteristics, yet each are unique in their hydrology and biodiversity

MARSHES

A marsh is another type of wetland. There are salt water marshes and fresh water marshes. Marshes have shallow water and floating leafed plants and grasses. A great many animals like marshes because it is a very good place for protection from predators, food supply, and nesting sites. Migratory birds and waterfowl depend on marshes as resting places as they migrate.

Fresh water marshes are dependent upon rainfall, runoff, and flooding that occurs during certain seasons. Fresh water marshes support many species of animal, such as frogs, turtles, ducks, egrets, heron, hawks, muskrat, mink, otter, and in some regions alligators.

Salt marshes are generally influenced by wind and tides and have special plants that have adapted to the salty life of a salt marsh. They are useful commercially for speckled trout, crabs, and shrimp.

SWAMPS

Swamps are one type of wetland. They hold many different types of plants and animals. They fall into two categories; forested swamps and shrub swamps.

Forested swamps are dominated by the bald cypress and tupelo gum trees. They also have other varieties of trees and plants. They provide homes to many animals like deer, beaver, otter, muskrat, fox, black bear, frogs, snakes, turtles, and a large variety of birds. The difference between the forested swamp and the shrub swamp is that the forested swamp has lots of trees and is often covered by a layer of old leaves.

A shrub swamp is a swamp that has mostly shrubs in it rather than trees. It is dominated by grass, algae, reeds, and many types of shrubs. Herons and other birds like shrub swamps because of the abundant food supply.

BOGS

Bogs can be found all over but they are usually in cold regions of the world. Bogs form from shallow lakes, slowly moving water, and where there is bad water run off. They usually have no inflow or outflow.The plants decay slowly so there is lots of peat in bogs. The soil is generally poor and quite acidic. Unique plant life grows in bogs. Carnivorous plants such as the venus flytrap and pitcher plant grow in bogs. Also seen in bogs are a variety of wildflowers, grasses, rushes, and sedges. There is often an abundance of mosses and sphagnum moss. Bogs do not usually have a lot of different types of animals, other than insects, because the water is very acidic too. Migratory birds, however, often stop off at bogs to rest along their journeys. Some bogs will also have certain fish species such as the smallmouth bass. Some reptiles and amphibians are also found in bogs; frogs, salamanders, turtles, and snakes.

ESTUARY

Coastal waters

(including estuaries and lagoons) constitute the interface between the marine and the freshwater environments, and between the continents and the oceans. Estuaries are broad portions of rivers or streams near their outlet, influenced by the marine water body into which they flow. As such, estuaries are semi-enclosed coastal bodies of brackish water with free connection to the open sea. The demarcation between an estuary and the sea is generally the mean tidal level. Similar to coastal ponds or lakes, lagoons are shallow brackish water bodies with one or more restricted outlets to the sea. Estuaries and most lagoons receive water from land and therefore can be heavily impacted by land-based sources of pollution through inland runoffs. Coastal waters are the main area of development for artisanal fisheries and play a key role as nursery grounds for a wide range of marine species and are the principle cause of conflict between artisanal and industrial fisheries.