Aquatic ecosystems, ponds, streams, lakes, rivers, oceans, estuaries
EVS Notes Unit I Multidisciplinary nature, Natural Resources, Forest resources, Water resources, Mineral resources, Food resources, Energy resources, Land resources, Role of an individual Unit II Introduction structure-function, Forest eco-system; Grassland ecosystem; Desert ecosystem; Aquatic ecosystems Unit III Air pollution, Water pollution, Soil pollution
THE POND ECOSYSTEM
A pond is a good example of a small self-sufficient and self-regulating ecosystem. Location, size, depth, and substratum of a pond influence the biology of the pond ecosystem. The components of the systems are as follows:
Temperature, light, water, and several inorganic and organic substances like CO2, O, N, PO, Ca, S, and carbohydrates, proteins, and lipids make abiotic components. Some proportions of nutrients are in a solution state but most of them are presently stored in the particulate matter as well as in living organisms. The amount of minerals present at any time in the physical environment of the pond is called the standing state.
They are green plants and photosynthetic bacteria categorized into two types:
Ceratophyllum, Hydrilla, Utricularia, Vallisneria, Jussiaea, Nitella, Wolfia, Lemna, Spirodella, Pistia, Eichhornia, Azolla, Salvinia, Trapa, Typha, Marsilea, etc. are included in this category. This may be classified further into submerged, free-floating, and amphibious plants.
These are minute floating or suspended lower plants belonging to some algae and flagellates. Ulothrix, Spirogyra, Oedogonium, Chlamydomonas, Zygnema, Volvox, Pandorina,
Cosmarium, Scendesmus, Closterium, Anabaena, Pediastrum, Microcystis, diatoms, etc. are common algal phytoplanktons.
These are as follows:
i) Primary consumers
(a) Zooplankton comprises ciliates, flagellates, other protozoans, small crustaceans like Copepods and Daphnia, etc. These animals drift with the water current and are found along with phytoplankton upon which they feed.
(b) Benthos or bottom forms comprise the bottom-dwelling animals, e.g., annelids and mollusks which feed on plants directly or on plant remains at the bottom.
ii) Secondary consumers
These are the carnivores that feed on the herbivores, e.g. insects and fish.
iii) Tertiary consumers
These are some large fish as game fish that feed on the smaller fish.
c) Decomposers (or micro consumers)
Several bacteria, fungi (Aspergillus, Cephalosporium, Pythium, etc.), and actinomycetes represent the group.
THE OCEAN (MARINE) ECOSYSTEM
The oceans of the world cover approximately 36,10,00,000 km2, i.e. about 71% of the earth’s surface. Atlantic, Pacific, Indian, Arctic, and Antarctic are the main oceans of the world. The ocean represents a very large and stable ecosystem. The main components of the ocean ecosystem are as follows:
Marine environment, as compared with fresh water, appears to be more stable in chemical composition due to being saline (35 parts of salts by weight per 1000 parts of water, while salinity of fresh water is less than 0.5%), and moreover, other physicochemical factors such as dissolved oxygen content, light, and temperature are also different. About 27% is NaCl; most of the rest consists of Ca, Mg, and K salts. Water is strongly buffered. The concentration of dissolved nutrients is low and constitutes an important limiting factor to determine the size of marine populations. Waves of various kinds and tides prevail there. Like ponds and lakes, the ocean shows distinct zonation.
This category includes phytoplankton and larger marine plants. The former group includes diatoms and dinoflagellates. The latter group includes seaweeds (algae) belonging to Chlorophyceae, Phaeophyceae, and Rhodophyceae; and angiosperms. Ruppia, Zostera, Posidonia, Halophila, Enhalus, etc. are true marine angiosperms while various species of Rhizophora, Avicennia, Sonneratia, Carapa, Aegiceros, etc., represent the mangrove complex tidal woodlands
These are heterotrophic macro consumers, being dependent for their nutrition on the primary producers. These are:
i) Primary consumers
The herbivores that feed directly on producers are chiefly crustaceans, mollusks, fish, etc.
ii) Secondary consumers
Carnivorous fishes, such as Herring, Shad, Mackerel, etc. are included in this group.
iii) Tertiary consumers
Fishes like Cod, Haddock, etc. are the tertiary or top consumers.
They are chiefly bacteria and some fungi which participate actively in the decomposition of dead organic matter.
An estuary is a semiclosed coastal body of water that has a free connection with the sea. It is strongly affected by tidal action, and within it, seawater is mixed with fresh water from land drainage. River mouths, coastal bays, tidal marshes, and bodies of water behind barrier beaches are some examples. Estuaries are generally productive because water flow subsidizes an abundance of nutrients. The chief biotic components of an estuarine ecosystem are as follows:
Macrophytes- marsh grasses, seaweeds, sea grasses, benthic algae, and phytoplankton.
Oysters, crabs, several kinds of shrimp, and many commercial sports fish.
CORAL REEF ECOSYSTEM
A coral reef represents one of the most beautiful and well-adapted ecosystems to be found in the world. Coral reefs are made up of calcareous skeletal remains and secretion of corals and certain algae. They are confined largely to the warm waters of the Pacific and Indian oceans.
A few coral reefs also occur elsewhere. The reef-building corals grow best in waters having an average annual temperature of about 24°C at a depth of about 40-50 meters. They can survive neither sudden temperature changes nor prolonged exposure to temperatures below 18°C. They also require for their growth rocky floor and sunlit water with having normal salinity of 35g I-1. They cannot grow in fresh or turbid waters or on highly saline lagoons.
Reef structures are built around islands and volcanic peaks by coral and other lime-secreting minute animals. Corals build protective shells of calcium carbonate around their bodies, which after their death, sink and accumulate on the sea bottom. Coral families usually produce forms that resemble branching trees or shrubs. In due course, the inner spaces between the branching coralline structures are filled up by the deposition of calcium carbonate either by lime-secreting organisms or by debris brought by sea waves. Apart from polyps (corals), a number of organisms and plants such as calcareous algae, bryozoans, mollusks, and microscopic protozoans (foraminifera) take part in building coral reefs.
These are little self-contained worlds, in bottles or other containers that simulate in miniature the nature of ecosystems. Completely closed micro-ecosystems (or microcosms) that require only light energy are very difficult to have on a small scale. Experimental microcosms usually vary from partially closed systems having outlets and inlets only for gaseous exchange with the atmosphere to very open systems involving assemblages of organisms maintained in various kinds of chemostats and turbid states with the regulated flux of both nutrients and organisms.
Well-designed microcosms may exhibit most of the basic functions and trophic structures of an ecosystem, except for the reduction in variety and size of constituent components. Microcosms are suitable for the study of nature and the functions of the ecosystems in the laboratory.
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