In the Pacific Ocean off the Northwest Coast of the US, there is a food chain of
ID: 181890 • Letter: I
Question
In the Pacific Ocean off the Northwest Coast of the US, there is a food chain of 4 trophic levels:
Sharks eat Rays/Skates eat Scallops eat Phytoplankton.
There are two ways humans might be interfering with this system: (1) Fishing for sharks could greatly reduce the shark population. (2) Discharge from sewage treatment plants and storm sewers could greatly increase the availability of nitrogen and phosphorous—key nutrients for phytoplankton growth—and increase the amount of phytoplankton in the water. What impact might these have on the entire food chain and how might that depend on what determines the structure of this community?
In your answer, please include:
(a) An introduction explaining the concepts of trophic levels and food chains. Describe both direct and indirect interactions between trophic levels.
(b) An explanation of how the models of top-down control and bottom-up control can be applied to the shark food chain. Include:
How you expect the shark food chain to react to shark hunting according to each model. (What happens to EVERY trophic level?)
How you expect the food chain to react to increased levels of phytoplankton nutrients according to each model. (Again, what happens to EVERY trophic level?)
What are the direct and indirect interactions that cause these outcomes?
Explanation / Answer
Trophic level: This system in ecology also pronounced as Food chain of an ecosystem, step in a nutritive series.The series goes as follows:
Level based on their feeding behavior: The level start from the bottom and comes to the top, The most basic level to strengthen all other levels is “Producers” (green plants) –Consumed by second-level organism known as “Herbivores”—The next level is the animal eaters or “Carnivores”—The forth level in this cycle is “Secondary carnivores” those who eat primary carnivores.There are organisms as “Omnivores”, which are carnivores also consume plant sources of food. Also a trophic level of “Decomposers”, those who transforms or degrades the dead matter, these nutrients then can be accessible to producers.
Direct effect or interactions are those cases where an indivisual of one species directly affects fitnesses of other organism. Divisions are made into four categories- i) All forms of exploitation, ii) Interferance competition, iii) various of other types of positive. two good examples are Commensalism and Mutualism.
Indirect approach or effect is referring to a broad variety of species interactions that is linked to direct species interaction, such as predetion. This effect is heavily applied to trophic pyramids and keystone species. This effect is further devided into three parts i) Exploitation competition, ii) Apparant competition, iii) Indirect positive interactions with various other forms. Examples are the Keystone predation, trophic cascade etc.
Bottom up control is what we have mentioned in the first para, having producers, then primary consumers and then secondary consumers. Top up control is the view of the same approach with an oppostive view or role. We may have both the scores or organisms number and analysis result, are the useful.
In our particular problem we have "Sea trophic level/ food chain" has showed us an example to analyze. Sharks eat Rays/Skates eat Scallops eat Phytoplankton. Here the Phytoplatons are the primary producers- provides the source for Scallops- in turn in determines the secondary consumer Rays- finally goes up to the level of Sharks, the " Secondary Carnivores" eating Rays or Skates.
Now focusing on our problem: 1) Fishing too much of Sharks could disturb the whole system and can leads it to a choas or disturbance. Top down aspect is significantly breached here to cause imbalance as the top predator is removed the chain is disrupted. This causes surge in Ray fish population, then to Scallops and way back to the phytoplanktons. Bottom up approach is to suggest when the "Phytoplaktons" are destroyed or removed, this can severely damage the entire food chain.
Top down approach is thus single most caase where Shraks population decrese help flourihing Phytoplanktons to grow abundantly, water colour from the Pacific Ocean off the Northwest Coast of the US could turn to green from blue.