Oceanic Life Causing Harm?

Rising phytoplankton popultions in the Pacific ocean is one of several explanations as to why levels of methylated mercury are on the rise. According to data gathered by U.S. researchers and policy makers, methylated mercury levels have been on the rise at an annual rate of 30%.

Methyl mercury, a human neurotoxin formed when mercury is methylated by microbes can accumulate in tuna as well as in a variety of fish commonly consumed. Although the process of how mercury is methylated is known, it is unclear how such large amounts are appearing in oceans. It is estimated that as much as 29% of all subsurface mercury is methylated.

It was once thought that methylated mercury came from rivers and streams which terminated at oceans, or even mercury in the atmosphere. Additional explanations, as to how this is occurring include excess amounts of organic carbon from phytoplankton providing surfaces where microbes can methylate mercury. Warmer climate changes in certain zones due to global warming may be the cause of a phytoplankton and fish population increase, which in turn produce more organic carbon. Like many problems regarding oceanic life today, the delicate balance between terrestrial and atmospheric activity is greatly impacting marine biological interactions.

-Julio Rodriguez (group c)


Update:
Methyltaed mercury levels as small as 3 µg/kg may have toxic effects on humans. Methylated mercury is converted into inorganic mercury in the liver and kidneys but also targets the brain and the rest of the CNS.

Symptoms of methyl mercury poisoning, due to high levels of the accumulated toxin, are impaierd motor, cognitive and other functions controlled by the CNS. Also, inhaling methyl mercury can be as toxic as ingesting it.

I am not sure that amounts of methyl mercury accumulated in fish is related to the ability to intake the toxin. It may be that certain fish are in a section of the ocean that has high levels of methyl mercury and then considered more dangerous than others.