The series of change in ecosystem overtime is known as succession. It includes both either establishment or destruction of an ecosystem. This destruction can be natural or occur by human activities like deforestation, flood, fire, earthquake, pollution etc. It can be observe by identifying the species in a given area.
Assuming a situation, one large size ship containing huge quantity of crude oil, transporting through sea from one country to another. Due to some technical issue ship exploded or cracked; whole ship sank into the water whereas crude oil float on the surface of sea because oil is more viscous and heavier then water. Oil spread in to large area of sea hence polluting the vast region of ecosystem, that kills many life of organisms not only under water but it also disturb lives outside it such as birds specially driving birds, seashores organism, humans etc.
Area that directly exposed to oil pollution suffered immediate and total destruction of biodiversity as it is very toxic to organisms once they intake it they will die. but it doesn’t mean that it will remain same forever. The damaged ecosystem must undergoes slow process of regeneration simply knows as ecological succession.
Pattern of Change:
• Once the ship settled on the bottom of the sea and phase of acute toxicity of hydrocarbon passes, area starts resettling by organisms.
• Pioneer species or opportunistic species are the first that start growing after the disturbance, these species are characterized by small in size, short life cycle and high multiplication or fertility rate (majorities are microbes and micro flora) also known as r-Type of species.
• As ship sinks, curding of metal starts and organisms that adapted anaerobic conditions grows first until the complete layer of hydrocarbon removes.
Oil eating bacteria’s also facilitates in degrading the hydrocarbon layer on the surfaces. These bacteria are consider as transient organisms. Which present in that area between particular period of time and as oil completely degrades they die out from the area.
• When the sunlight starts reaching to the bottom of sea, algae start covering up the surface of ship where they can easily photosynthesis. And after that other photo-plants also start growing with them especially soft corals.
• Later the arrival of small creature and tiny fishes which relies on soft corals also start appearing and feeding on them.
• As soft coral starting covering the bottom, big fishes and predator organisms become more common as they feed on the smaller reef fishes. Predators such as diving fishes and shark.
• Early organism in succession are simple and may present in high number but as succession continues large organism come in seek of small animals for their food. It can also shows that the area undergoing succession end to food chain.
• Elsewhere in food chain other life form also colonize i.e. hard corals. They are relatively simple organism but are among the last to take hold.
• In ecosystem large animals or predators are very small in numbers as compare to the organisms they consume, they characterized as large in size, having long life cycles and slow multiplication rate also known as k-Type of species. Their presence elongates food chain and forming ecosystem more complex.
• Driving birds, predators like shark and hard corals need years to grow and to take hold. These organisms are the climax species of this ecosystem and are relatively stable organisms of the community.
• When the composition and structure of community starts resembling to the situation existing before the disturbance plus the presences of climax species in that ecosystem; both indicates that the particular ecosystem is now fully established.
Recovering of ecosystem from severe disturbance can take hundreds to thousands of years and this pattern of change in ecosystem is an example of ecological succession.