Elephant Seals – Worse Than Your Akita’s Shedding

As aforementioned, I’ve currently become deeply invested in podcasts. One such podcast is “Science Friday” hosted by Ira Flatow on Public Radio International. On a recent jam-packed episode, an exciting topic came up – Elephant Seals [1]! These (not-so) little guys have been causing lots of problems for the last couple of decades; and we’re only finding out now!

First, a little bit about Elephant Seals. There are two breeds of Elephant Seals – Northern and Southern [2]. In this study, we focused on the Northern breed or Mirounga angustirostris. The Southern species is not only significantly larger, but also lives longer than its Northern counterpart. The Northern species lives only along the Pacific coast of Northern America. In terms of IUCN status, the Mirounga angustirostris is a success story! Once thought to be extinct due to over-hunting, this guy has made a comeback and is back up at around 120,000+ [3].

In case anyone was wondering why they’re called “Elephant” Seals… (Mirounga angustirostris)

Mirounga leonine (Southern Elephant Seal)

Elephant Seal shedding

Elephant Seal puppy

For several decades, scientists have been noticing severe mercury spikes in the Pacific Ocean off the coast of California. The case was unknown for years until an exciting development came along in science – using DNA mapping technology to map the DNA of the ocean! What was the result? This mercury was coming from the coast? Lo and behold, we find shedding Elephant Seals on the shoreline!

During a recent study (which can be found here [4]) at UC Santa Cruz, it was discovered that during the molting season, levels of methyl-mercury – one of the most toxic forms of mercury – was 17 times higher than normal (as if it wasn’t dangerous enough in the body already). And it’s in fact precisely because of the mercury’s poisonous levels that Elephant Seals try to shed their hair. The Seals will cumulate the mercury in the hair on their bodies, and then shed the hair to rid the body of the toxin [5], in a process called Catastrophic Molting [6]!

One might ask how we know that the mercury is coming from the Elephant Seals fur and not from their feces or other fauna altogether. The answer lies in newborn Seals. Because mercury is so easily absorbed into the system of living creatures, it stands to reason that pregnant mothers would “infect” their unborn children as well. In fact, pups born to contaminated mothers showed high levels of methyl-mercury in their “natal coal” or the hair that they are born with [7]. So, we can extrapolate that the seals coat is to blame for increased ocean methyl-mercury levels.

Now you might not think that this is a problem, but the mercury in the hair gets washed up back into the oceans, digested by microbes in the water, and moves its way back up the food chain, until it may have serious consequences for humans, Elephant Seals, and the ecosystem overall. The levels found around Seal molting grounds are higher than those found in highly urbanized, contaminated coastal towns. This problem is further accentuated by the fact that industrial pollutants in the water have already significantly increased mercury levels in the oceans.

What makes the situation worse is that mercury doesn’t degrade either, which means that overtime, it’s going to concentrate itself more heavily at the top of the food chain, with unknown consequences. This process is known as biomagnification.

So, do we know anything? Well, yes. We know the harmful effects that methyl-mercury has on the human body. According to the EPA, methyl-mercury has significant effects on humans, including but not limited to: neurological development in infants, “impairment of the peripheral vision; disturbances in sensations (“pins and needles” feelings, usually in the hands, feet, and around the mouth); lack of coordination of movements; impairment of speech, hearing, walking; and muscle weakness” [8] and even potentially death. One such extreme case of mercury poisoning was in Japan, from 1932 to 1968 [9]. A factory that produced acetic acid discharged its waste into Minamata Bay, where nearby residents consumed contaminated shellfish for years. What was eventually known as Minamata disease caused “brain damage, paralysis, incoherent speech and delirium” in over 50,000 local residents.

So, how do we stop all of this? Scientists aren’t quite sure, but one thing is for sure: we need to reduce our pollutant footprint if we want to keep these cute guys around, and other apex predators; especially if we want a chance of surviving a healthy human life, for us and generations to come.

Sources:

1. http://www.sciencefriday.com/segment/09/11/2015/testing-ocean-dna-americans-pass-a-science-quiz-and-polar-bear-diets.html
2. http://animals.nationalgeographic.com/animals/mammals/elephant-seal/
3. http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/northernelephantseal.htm
4. http://www.pnas.org/content/early/2015/09/02/1506520112
5. http://www.santacruzsentinel.com/environment-and-nature/20150917/molting-elephant-seals-recycle-mercury-back-into-seawater
6. http://www.mnn.com/earth-matters/wilderness-resources/stories/elephant-seals-are-raising-mercury-levels-california-beach
7. http://www.theverge.com/2015/9/12/9313363/mercury-molting-seals-fur-California
8. http://www.epa.gov/mercury/effects.htm#meth
9. http://www.who.int/mediacentre/factsheets/fs361/en/