Marine or ocean ecosystem
Introduction: These are the gigantic reservoirs of water covering approximately 71% of the Earth's surface (an area of some 361 million square kilometers). The salt concentration in an open sea is usually 3.5% (35 parts per thousand (ppt)). Dominant ions are sodium & chloride. Average temperature of Marine ecosystem is 2-3 degree centigrade, devoid of light.
I. Biotic components:
1.Producers: It includes phytoplanktons (diatoms, dinoflagillates), large seaweeds (mainly algae like chlorophyceae, phaeophyceae & rhodophyceae; angiosperms like Ruppia, Zostera, posidonia ), and mangrove vegetation (like Rhizophora, Carapa etc.)
a) Primary consumers:These are herbivores and feed directly on producers (Crustaceans, Mollusks, fish etc.)
b) Secondary consumers:These are carnivorous fishes (Herring, Sahd and Mackerel)
c) Tertiary consumers: These are top carnivorous fishes (Cod, Haddock, etc.)
3) Decomposers: These are micro – organisms like bacteria, fungi.
II. Abiotic components: High Na, Ca, Mg and K salt concentration, variable dissolved oxygen content, light & temperature make a unique physiochemical conditions in marine water.
ENERGY FLOW IN ECOSYSTEM:
- All organisms must obtain a supply of energy and nutrients from their environment in order to survive.
- The transformations of energy in an ecosystem begin first with the input of energy from the sun.
- Because, it is the first step in the production of energy for living things, it is called “Primary production”.
- Photosynthesis -- Chemical reaction where green plants use water & carbon dioxide to store the sun’s energy in glucose.
- ENERGY is stored in glucose.
- Glucose is stored as starch in plants
- The majority of autotrophs are photoautotrophs that harness the energy of the sun and pass some of this energy onto consumers through feeding pathways.
- The energy contained within producers and consumers is ultimately passed to the decomposers that are responsible for the constant recycling of nutrients.
- Thus, there is a one-way flow of energy through the biotic community and a cycling of nutrients between the biotic and abiotic components of the ecosystem
- Energy flow cannot occur in reverse direction.
- Starts from autotrophs (the producer level, i.e., first trophic level) to Heterotrophs including plant eaters or Herbivores (second trophic level) and so on.
- The amount of energy decreases with successive trophic levels.
- Only About 1% of energy from the sun is used by green plants & rest remains unutilized.
- Similarly, there is loss of energy in each trophic level.
- The transfer of food energy between the organisms in an ecosystem can be tracked by constructing food chains, food webs, pyramids of numbers, biomass and energy and energy flow diagrams.