Claire Corlett

Fish Food, Fish Tanks, and More
Bioaccumulation of Methylmercury into Fishes and Humans | Koaw Nature

Bioaccumulation of Methylmercury into Fishes and Humans | Koaw Nature


[♪ theme music ♪] So you know about the food web- If we look at the bottom, this is where mercury begins its
aquatic bioaccumulation process into microorganisms, then
into fishes, and then into us. So there are many
species types of mercury, but I will continue talking about this organic
mercury, methylmercury, because 95% of the
mercury within fishes is methylmercury (MeHg)-which
is seen like this or like this. The first step of mercury
entering the food chain begins with its absorption
by bacteria or phytoplankton or even being methylated by
sulfate-reducing bacteria. And although higher organisms like fishes or us can uptake MeHg from
the environment, most of it comes from
consuming MeHg containing food. So take this diatom for example, a phytoplankton, or an
itty-bitty aquatic plant – methlymercury is transported
across its lipid membrane effected by diffusion of
its uncharged chloride
complex, CH3HgCl. Then a zooplankton,
such as a copepod, will consume that diatom. Since the methylmercury
is associated with the soluble
aspects of the diatom the copepod absorbs that
methylmercury more easily than, say, Hg (II) complexes which becomes bound to the
particulate cellular material of the diatom thus
being less digestible and excreted more
by the copepod. So then a little fishy
might come along, say a bluegill, and
eats that copepod. The methylmercury’s
liposolubility allows it to be partially
retained in fatty tissues. But the methylmercury is
also found in the meat, the stuff we humans like to eat and fish appear to
have a high specificity of the intestine wall for
methylmercury absorption. Let’s say a northern
pike comes along and eats that bluegill- it’s also consuming all
the retained methylmercury from that bluegill’s consumption
of eating a bunch of copepods with retained methylmercury that consumed a bunch of diatoms
with retained methylmercury. So these are examples
of consumption events at differing trophic levels. And the more trophic levels
that an aquatic system has, the more methylmercury top predators in that
system will have built up. So let’s say we add
another planktivore to this system we’ve
already designed. Let’s add a rainbow smelt. So a copepod that absorbed
a bunch of diatoms is then consumed by a
juvenile rainbow smelt that is then consumed
by a bluegill that is then consumed
by the northern pike. There’s more opportunity
for methylmercury absorption in this system at the
higher trophic levels. And even imagine
another top predator, the muskellunge, coming and eating that pike- and that pike has probably
eaten a lot of bluegills with retained methymercury
from eating a bunch
of…well you get it, right? So this is why they
say, “Eat more panfish.” They want you to
monitor your consumption of these top predatory fishes as well as panfish! Yes there are great
benefits from eating fishes like that of the
omega-3 fatty acids. But there does come a
point when these benefits from eating any type of fish is outweighed by the
amount of methylmercury that might bioaccumulate
in your body. And you might be
wondering whether there is indeed mercury in the waters
where your fish are coming from. Well mercury is introduced
into the environment both through natural and
anthropogenic causes. So even if the waters you
fish from or buy fish from don’t have industry
or mining near them, there is no escape from mercury because it is in our atmosphere And it keeps getting put into
our atmosphere by our industry and it has a residence time
of about a year meaning- it can reach just about
anywhere in the globe before entering lakes,
seas, oceans and rivers mostly via precipitation. It gets everywhere. So if you are woman
that is pregnant, or you are nursing or if
you even have children, it’s important to limit
of consumption of fish, especially certain
species of fishes. So I’ll list some
species that the FDA completely recommends
that you avoid if you fit one of the
categories I just mentioned. You want to try to
avoid eating any sharks, bigeye tuna, king mackerel, swordfish and marlin. Basically you’re eliminating
all the top predatory fishes. And in the inland
waters where I fish it’s recommended that
children under 15, nursing mothers and women
in their childbearing years don’t consume more
than 1 serving per week of low level predators
like bluegill, perch, inland trout, and crappies. And only have 1
serving per month of walleye, northern pike,
largemouth bass, catfish and other high
predatory species. And not to eat
muskellunge at all. Something I would never do- not ’cause I’m
pregnant-but because I have too much
respect for the fish and I release every one
of ’em that I catch. This clip on methylmercury
came from a larger video called “What is a Panfish.” Check it out. It’s pretty cool! Thanks for watching
and that link is below. If you’re not yet
subscribed please do so! That’s absolutely free Big thanks to my
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spread the knowledge and be Nature-heroic! Koaw.org – Koaw Nature 2019

2 comments on “Bioaccumulation of Methylmercury into Fishes and Humans | Koaw Nature

  1. Nicely done. A cogent explanation as to why we are receiving warnings about eating certain types of fish.

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