Aquatic life zones, which include the ocean, rivers, lakes, and wetlands, differ in many aspects from terrestrial biomes. Unlike the situation in terrestrial biomes, temperature and precipitation are not the factors that determine the types of organisms that thrive in an aquatic ecosystem. First, water itself tends to moderate temperature and second, any precipitation falling on the water cannot obviously be a major influence. Based on water movements, it is categorized as
(1) Lentic-Water is still or slowly moving. Eg pond, lake, etc.
(2) Lotic- Running water systems, eg springs, streams, and rivers, etc.
(3) Wetlands- These areas gots inundated with water and support a flourishing community of aquatic organisms. They are shallow systems with black and rich sediments and abundant nutrients. e.g.Swamps, marshes, and mangroves are examples of wetlands. The marine ecosystem is the largest aqueous ecosystem and occupies around 71% of the earth’s surface which consists of high biodiversity compared to terrestrial ecosystems. The maximum diversity of marine organisms is found in the tidal zone. Marine – flora, and fauna is highly tolerant of high salt content. They cannot live in freshwater. If they are placed in freshwater, their body will swell due to osmosis. Bioluminescence properties can be seen in deep-sea creatures. Brackish Water contains more salinity than freshwater but not as much as seawater. • There are three main types of the organism in an aquatic ecosystem-
- Plankton – The free-floating plankton are microorganisms that cannot swim easily and are buffeted about by the waves and currents.
Plankton again is of two types: Phytoplankton and Zooplankton.
Phytoplankton is the photosynthetic producers of the ocean and they form the basis of the ocean’s food web.
Zooplankton is the primary consumer that feeds on phytoplankton.
- Nekton- Nektons are strong swimmers, include all the larger organisms like fish, turtles, and whales.
- Benthos- These are the bottom – dwellers adapted to living on the floor of the water body. Some fix themselves to one spot like sponges, oysters, and barnacles. Others burrow themselves into the sand like worms and clams. Some others move about on the floor, like crawfish and brittle stars.