Types of Ecosystem

The biosphere holds a wide variety of ecosystem types, which this chapter first sorts by origin and habitat. By origin, ecosystems are either natural (occurring with or without human interference, such as forest, grassland or desert ecosystems) or artificial/manmade (deliberately created and maintained by people, such as a rice field or maize field). Natural ecosystems are further split by habitat into terrestrial ecosystems (forest, grassland, desert) and aquatic ecosystems, which in turn split into freshwater and marine systems — freshwater bodies are classed as lotic (running water, such as rivers, springs and streams) or lentic (standing water, such as ponds and lakes). Of all these, the chapter singles out the pond ecosystem for detailed study, as a classic, compact example of a natural, aquatic, freshwater, lentic ecosystem that is self-sustaining and self-regulating. Its abiotic components consist of dissolved inorganic substances (CO2, O2, calcium, nitrogen, phosphate) and organic substances (amino acids, humic acid) derived from dead organic matter, and its functioning is governed by light, temperature, water pH and other climatic conditions. Its biotic components cover producers (a variety of phytoplankton such as Oscillatoria and diatoms, filamentous algae such as Spirogyra, floating plants such as Azolla and Eichhornia, submerged plants such as Potamogeton, rooted-floating plants such as Nymphaea and Nelumbo, and marginal macrophytes such as Typha), consumers (zooplankton such as Paramoecium and Daphnia as primary consumers, bottom-dwelling benthos such as molluscs and annelids, secondary consumers such as water beetles and frogs, and tertiary consumers/top carnivores such as ducks, cranes, large fish, hawks and even humans), and decomposers (bacteria and fungi living in the mud, water and bottom sediments, recycling nutrients back into the system). Structurally, a pond stratifies into distinct zones based on distance from shore and light penetration: the shallow, warm littoral zone near the shore hosts rooted plants; the open-water limnetic zone has effective light penetration and is dominated by plankton; the deeper profundal zone below it gets no effective light and is dominated by heterotroph …