ECOSYSTEMS and BIOMES

Ecosystems vary according to the predominant types of living and nonliving elements available. Ecosystems may be classified along two major types:

• natural or those which have existed and are regenerated through natural processes; and


• man-made or those which have been formed through man's intervention.

Whether natural or man-made, ecosystems are basically characterized by the continuity of life processes brought about by the presence of life support systems that move around in cyclic paths.

Most of us are confused when it comes to the words ecosystem and biome. What's the difference? There is a slight difference between the two words. An ecosystem is much smaller than a biome. Conversely, a biome can be thought of many similar ecosystems throughout the world grouped together. An ecosystem can be as large as the Sahara Desert, or as small as a puddle or vernal pool.

Ecosystems are dynamic interactions between plants, animals, and microorganisms and their environment working together as a functional unit. Ecosystems will fail if they do not remain in balance. No community can carry more organisms than its food, water, and shelter can accomodate. Food and territory are often balanced by natural phenomena such as fire, disease, and the number of predators. Each organism has its own niche, or role, to play.

The types of marine ecosystems commonly used by fisheries and aquaculture are: coastal waters (including estuaries and lagoons), coral reefs, soft bottom continental shelves, upwelling continental shelves, open oceans and polar oceans.

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.

Coral reefs

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.

Soft-bottom continental shelves appear in front of major river systems and deltas from which they receive their characteristic fine sediments (e.g. gravel, sand and mud). Extending up to a depth of 200 metres, they are usually strongly influenced by the riverine effluents from which they draw their high productivity and which govern their natural variability. These ecosystems are exploited with a variety of fishing methods and are particularly suitable for bottom trawling. Artisanal fisheries are generally restricted to the shallower areas of these shelves, while semi-industrial and industrial fleets (with which artisanal fisheries often conflict) can exploit both the nearshore and offshore areas.

Upwelling continental shelves are very productive continental shelves found mostly at the eastern boundaries of the oceans, often in front of arid zones or deserts. The usually wind-driven, upwelling process brings cold, nutrient-rich water from deep layers into the euphotic zone where photosynthesis uses sunlight and the upwelled nutrients to produce the organic matter that is the basis of the marine food chain. These ecosystems are affected by strong inter-annual variability (e.g. El Niño and La Niña, off Peru-Chile). They represent areas of especially high concentrations of small pelagic species usually exploited by surface fisheries using purse seiners and mid-water trawls.

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. Seamounts are noticeable elements of the open ocean ecosystem and host some long-living and fragile deep-sea resources (e.g. orange roughies) on which fisheries have recently expanded - causing concern for the conservation of these poorly known ecosystems. Upper layers are exploited mainly with wide opening midwater trawls (e.g. for horse mackerel) and longlines (e.g. for tuna, billfishes and sharks).

Polar oceans (i.e. the Arctic and Antarctic oceans) are particular, highly-productive ecosystems with great seasonality, characterized by active, current-driven, enrichment processes that sustain important fishery resources (e.g. fish, krill, whales, small cetaceans) and other species (e.g. seabirds, seals). Some doubts have been raised that in some years krill production might be insufficient to support the demand of seals, penguins and albatross for the food needed to raise their offspring.

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.

Freshwater Ecosystems

Only 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.

Fall overturn

Where there is a pronounced change of seasons, the warming of the surface of the lake in the summer prevents this water from mixing with deeper water. This is because warm water is less dense than cold.
The surface water becomes enriched in oxygen

• some from the air above it


• the rest - because it is in the limnetic zone - from photosynthesis.
  

But the water in the profundal zone - being removed from both these sources - becomes stagnant.

In the fall, however, as the surface water cools, it becomes denser and sinks to the bottom - carrying oxygen with it.

A similar phenomenon occurs when the ice melts in the spring.

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.

The early course of a river is often in steep, mountain areas, with rapidly-flowing cold water. As a river continues along its course (which is always changing), the surrounding terrain flattens out and the river widens. Rivers often meander (follow a winding path) along their middle course. Tributaries (smaller rivers or streams) and runoff flow into the river, increasing the river's volume (the amount of water it has). Rivers often have increased volume and water speed in the spring, as snow at the river's source melts.

Most rivers end when they flow into a large body of water. The end of the river is called the mouth. At the mouth, there is usually a river delta, a large, silty area where the river splits into many different slow-flowing channels that have muddy banks. New land is created at deltas. Deltas are often triangular-shaped, hence the name (the Greek letter 'delta' is shaped like a triangle).

The Water in a RiverAt the source of a river, the water is relatively pure. As the water flows downstream, it picks up silt and minerals (including mineral salts) from the soil and rock in the river bed. Many other chemicals enter river water as it flows downstream, including animal waste, human sewage, agricultural (farm) runoff, urban runoff, and mining/factory effluent.

The course of a river changes over time, as erosion caused by the flowing water and sediment sculpts the landscape around the river. Rivers erode land and carry it downstream towards the sea or lake it flows into. This kind of erosion can even form canyons, like the Grand Canyon (eroded by the Colorado River), waterfalls, like Victoria Falls (formed by the Zambezi River), oxbow lakes, and other formations.
As eroded soil is carried downstream, it is deposited at areas where the river slows, especially where the river meets the body of water it flows into (often the ocean or a lake), forming a fertile river delta that has muddy swamps and/or sandbars.

River Extremes

The longest river in the world is the Nile River (4,157 miles long); it is located in northeastern Africa, and flows into the Mediterranean Sea. The second-longest river is the Amazon River (3,915 miles long); it is located in northeastern South America, and flows into the Atlantic Ocean. The third-longest river is the Chang (Yangtse) River (3,434 miles long); it flows across south-central China into the East China Sea.
The river with the biggest volume (the most water flowing in it) is the Amazon River.

What is a Biome?

A biome is a large area with similar flora, fauna, and microorganisms. Most of us are familiar with the tropical rainforests, tundra in the arctic regions, and the evergreen trees in the coniferous forests. Each of these large communities contain species that are adapted to its varying conditions of water, heat, and soil. It is characterized by a given assemblage of plants and animals that interact with each other within a given natural enironmental setting. Global climate patterns, plant and animal relationships and their evolution and migration, movements of continents and, to a high degree, human a ctivities, determine the distribution of species of plants and animals. For instance, polar bears thrive in the arctic while cactus plants have a thick skin to help preserve water in the hot desert.

The word "biome" is used to describe a major vegetation type such as tropical rain forest, grassland, tundra, etc., extending over a large geographic area (Figure 1). It is never used for aquatic systems, such as ponds or coral reefs. It always refers to a vegetation category that is dominant over a very large geographic scale, and so is somewhat broader than an ecosystem.

The major biomes are:
(a) deserts
(b) tundra
(c) grassland
(d) savanna
(e) coniferous forests
(f) deciduous forests
(g) tropical forests

Figure 1. The Distribution of Biomes

Tropical Rain Forests

Rainf forests are found in the tropics. Forming a thick, lush carpet of vegetation with a stunningly diverse array of species, tropical rain forests of the world once covered an area about the size of the United States. Today, tropical rain forests have been reduced by half, and logging continues at a feverish pace in many areas. Some experts think that tropical rain forests in all but a few places could be virtually obliterated early in the next century if nations do not enact strict measures to protect them.

A forest is that portion of the public domain where there is a predominant growth of trees. It is an area of land where plants and animal live together in close association, bound by specific and recognizable patterns of interdependence. Philippine forests are called tropical rain forests because of the country's tropical location and the amount of rainfall received (over 200 cm a year).

Of all the world's forests, it is those in the tropics that face the greatest threat from mankind. Tropical rainforests are one of nature's treasures, and many of them are now at risk. We have already destroyed half of the world's original tropical rainforests! Just in a few decades, we can possibly witness the complete elimation of the world's rainforests. Technically, this type of forest can be defined as a forest in the tropics receiving 4-8 meters of rain each year. Tropical rainforests are found in Central and South America, Southeast Asia and islands near it, and West Africa. There are smaller rainforests in northern Australia and other small islands. All tropical rainforests are found along the equator where the temperatures and the humidity is always high, with the days being equal to the nights.

Tropical Rainforest Layers

Tropical rainforests have four layers:

Emergent Layer
These giant trees thrust above the dense canopy layer and have huge mushroom-shaped crowns. These trees enjoy the greatest amount of sunlight but also must endure high temperatures, low humidity, and strong winds.

Canopy Layer
The broad, irregular crowns of these trees form a tight, continuous canopy 60 to 90 feet above the ground. The branches are often densely covered with other plants (epiphytes) and tied together with vines (lianas). The canopy is home to 90% of the organisms found in the rain forest; many seeking the brighter light in the treetops.

Understory
Receiving only 2-15% of the sunlight that falls on the canopy, the understory is a dark place. It is relatively open and contains young trees and leafy herbaceous plants that tolerate low light. Many popular house plants come from this layer. Only along rivers and roadways and in treefall and cut areas is sunlight sufficient to allow growth to become thick and impenetrable.

Forest Floor
The forest floor receives less than 2% of the sunlight and consequently, little grows here except plants adapted to very low light. On the floor is a thin layer of fallen leaves, seeds, fruits, and branches that very quickly decomposes. Only a thin layer of decaying organic matter is found, unlike in temperate deciduous forest.

Did you know that enough rainforests are being destroyed every minute to fill 50 football fields? We need to preserve these valuable resources because they are the lungs of our planet, and can possibly hold cures for many of our most deadly diseases. The tropical rainforests are a critical link in the ecological chains of our our earth's biosphere.

Despite covering only 2% of our planet's surface, over half of the earth's animal, insect species, and flora live there. Within a four mile square area of a tropical rainforest, you would find:

• Over 750 species of trees


• 1500 different kinds of flowering plants


• 125 species of mammals


• 400 species of birds


• 100 reptiles


• 60 amphibians


• countless insects


• 150 species of butterflies
  

**Only 1% of these species has ever been studied**

Important Facts

• Amazon rainforests produce about 40% of the world's oxygen


• One in four pharmaceuticals comes from a plant in the tropical rainforests


• 1400 rainforest plants are believed to offer cures for cancer


• 40% of tropical rainforests have already been lost in Latin America and Southeast Asia
  

Forest ecosystems have protective, regulative and productive functions. These functions can acquire utlity value for man and become functions of the cultural ecosystem. The effects of these functions on the environment are called forest influences. The more important of these are:

Protective functions

• soil protection by asorption and deflection of radiation, precipitation and wind;


• conservation of humidity and carbon dioxide by decreasing wind velocity; and


• sheltering and providing required conditions for plant and animal species.
  

Regulative functions

• absorption, storage and release of CO2, O2 and mineral elements.


• absorption of aerosols and sound;


• absorption, storage and release of water; and


• absorption and transformation of radiant and thermal energy.

Productive functions

• efficient storage of energy in utilizable form in phyto- and zoo mass;


• self-regulating and regenerative processes of woods, bark, fruit and leaf production; and


• production of a wide array of chemical compunds, such as resins, alkaloids, essential oils, latex pharmaceuticals, etc.

These functions can be utilized by man for:

Protection

• sheltering agricultural crops against drought, wind, cold and radiation;


• conserving soil and water; and


• shielding man against nuisances (noise, sights, smells and fumes)

Regulation

• improvement of atmospheric conditions in residential and recreational areas;


• improvement of temperature regimes in residential areas (roadside trees and parks); and


• improvement of the bio type value and amenity of landscapes.

Production

• supply of a wide array of raw materials to meet man's growing demands;


• source of employment; and


• creation of wealth