Oceans are the storehouse of both biotic and abiotic resources. Nowadays, when the terristorial resources are rapidly declining, the ocean resources are gaining more importance. But, in order to ensure the sustainable use of precious marine treasure, we must have proper understanding about the functioning of marine ecosystem. Then only, the carrying capacity of nature could be restored; otherwise, the fate of marine ecosystem would not be different than earlier. For this purpose, let’s understand the functioning of marine ecosystem in the layman’s language.
What is ecosystem ?
It is a type of inter-relationships among the various living and physical components for survival through exchange of energy and matter. These components includes animals, plants, light, air, water, and other life supporting systems.
In this way, the health of plants and animals is determined by the physical settings in which they live. In short, the physical factors have strong bearing on the growth and development of living organisms.
Euphotic or photic zone is the surface layer of sea water which constitutes around 200 m. This is the most fertile zone comprising almost 90 percent of marine organisms. It is called photic duo to the availability of sunlight for photosynthesis. Apart from this, there disphotic and photic zone where sunlight hardly or cannot percolate. Hence, the aphotic zone of the ocean is known as “Biological deserts.”
Temperature and salinity
Temperature and salinity are the major determinants for the marine organisms. As we know that salinity affects the density of sea water creating upwelling and downwelling.
Besides, shell forming animals cannot thrive in the absence of certain level of salinity. Whereas, temperature determines the dissolution of atmospheric gases in the oceanic water.
In short, both are important in making favourable condition for the growth of marine life. Therefore, smooth functioning of marine ecosystem is directly depends on the level of salinity, as well as temperature.
Marine ecosystem constitutes vast varieties of species. For the convenience of better understanding, these are classified in the three groups according to the location in the sea water.These groups are -Plankton, Neckton, and Benthos.
Planktons are also called floating organisms including plants and animals. It has two major groups – Phytoplankton and Zooplankton. Phytoplanktons are autotrophic plants with photosynthetic pigment.
It is the food for marine herbivorous and others. Besides, they are credited for half of the oceanic oxygen through photosynthesis by using carbon dioxide and sunlight in the photic zone. On the other hand, zooplanktons are animals which thrive on the Phytoplankton. Plankton includes, algae, protozoas, and other floating animals.
Nektons are labeled as swimmers. These are secondary consumers which thrive on primary consumers zooplanktons. Almost all have backbone. Fishes, reptiles, and dolphins are Nektons. Nektons are the great source of food for human communities.
Unlike other two, benthos live at or near the bottom of the Marine environment. Crabs, oysters, and octopus are popular benthos which thrive at the bottom of the aquatic environment. These are also known for theirs recycling abilities of dead materials.
In the Marine ecosystem, these are the three categories of organisms which thrive in the different regions as per theirs abilities. In order to get insight of the functioning of marine ecosystem, at least a general understanding is highly essential.
• Phytoplankton> Zooplanktons>Nekton>Benthos and bacterioplankton…
This is the general order of marine ecosystem in which all the Marine communities are inter-related or interdependent.
Functioning mechanism of marine ecosystem
Unquestionably, Sun is the primary energy sources for entire environment. In oceanic environment, Phytoplankton as a autotroph, with the help of sunlight and carbon dioxide produces food and precious oxygen for the aerobic organisms.
In this sequence, zooplanktons are primary consumers which graze on the phytoplankton for theirs survival. The second group is Nekton which consume zooplanktons or even other Nektons. These are secondary consumers and constitutes large proportion of human food as well. Some of the Nektons are labeled as scavenger too.
Third group is benthos which thrive at the bottom of aquatic environment. Majority of them are decomposers and play important role in the recycling of materials.
Now, it is clear that marine ecosystem needs many life supporting systems for proper functioning. Unlike terristorial organisms, marine organisms are very sensitive for the changes in temperature, salinity, oxygen and other elements. Rise in temperature of sea water, ocean acidification, deoxygenating sea water and over fishing are some of issues threatening the existence of marine life.
•References: Oceanography by K. Siddhartha.