Ocean life appears to be affected by a relatively small number of variables such as temperature, density, available sunlight, available nutrients. If any one of these variables changes how do you think it might it impact the human food web?

A change in one of these variables can cause a population decrease in some living being that has the ocean as its habitat. This decrease would affect the feeding of animals that consume this living being and this will disharmonize the entire food chain of consumers above this living being.

Explanation:

Although the ocean is affected by a relatively small number of variables. These variables are essential for the maintenance of living beings within the ocean. If one of these variables is modified, in the long term, many species of living beings can be negatively impacted in an intense way, even having their survival in danger and decreasing their population density. This would be very harmful to the harmony of food chains within the ocean. That's because, as you may already know, the food chain is a feeding sequence between living beings, where one species feeds on another, which shows how one species depends on the other to survive.

Thus, if there is a change in the variables that act on the ocean and this change causes the population reduction of a species of living being. The species of animals that feed on this living being will also be affected as they will not have enough food to sustain themselves. Isss will decrease the population density of this second species, affecting the species that will feed on it, and so on.