Mercury is only present in small amounts in marine ecosystems, yet it

Mercury is only present in small amounts in marine ecosystems, yet it still presents a potential danger to fish eaters. Species of fish that are relatively higher on the food chain contain higher concentrations of mercury in their tissues than do smaller fish. Mercury is efficiently absorbed, but only very slowly excreted, by tiny organisms such as algae and phytoplankton. When these small organisms are consumed by a predator, and those predators are consumed by other predators, the mercury level accumulates. In order to reduce the natural occurrence of mercury biomagnification, fisheries could study measures of plankton density, which are relatively easy and inexpensive to estimate. Such measurements have been shown to be effective predictors of mercury biomagnification, wherein high levels of density positively correlate with high levels of mercury concentration.

Many larger fishing companies, in order to assuage consumer concerns, have combined their marine fishing efforts with farm fishing, which involves raising fish commercially in tanks or enclosures with no exposure to mercury or other chemicals that are susceptible to biomagnification. Another advantage of fish farming and other forms of aquaculture is that it counteracts the overfishing that has destroyed marine habitats in many ares while allowing commercial fishermen to keep up with the increasing market demand for fish.

Which of the following, if true, most strongly supports the prediction that fisheries that measure marine plankton density would reduce the amount of mercury in the fish they obtain from the ocean?

(A) Fish that live in areas of high plankton density are easier to obtain.
(B) Small-scale coastal fishermen have reported lower levels of mercury in fish obtained from areas of low plankton density.
(C) High plankton density is also correlated with high mercury levels in fish farm tanks.
(D) Consumer concerns regarding mercury levels in fish have been greatly reduced due to the increase in fish farming.
(E) Fishing companies that use farm fishing raise fish that live in tanks with high levels of plankton but have no mercury in their tissues.