[Coral-List] Re Special report on ocean threats in the Economist

[Charles Booth]

I posted this last night, but it appears the text of my comments didn¹t make
it into the message (at least not the message included in Coral List Digest
No. 5, issue 9). So, I will try again (with a few minor revisions):

Regarding the article in the Economist cited by Shanee S. in an earlier post
(http://www.economist.com/surveys/displaystory.cfm?story_id=12798458), as a
physiologist who studies, among other things, salt and water balance in
marine animals, I cringe whenever I read the quote from JFK that: ŒAll of us
have in our veins the exact same percentage of salt in our blood that exists
in the ocean.¹  Over the years, I have heard and read others repeat this as
fact.

I hope readers of this listserv know that JFKs statement is not correct.
But, in case anyone is a but rusty on human physiology, typical
concentrations for sodium and chloride (the two major ions) of human blood
plasma and seawater are as follows:

In human blood plasma, sodium ion (Na+) makes up  ~ 36% and chloride ion
(Cl-) ~ 42% of the total salts by weight. In seawater, Na+ is 30.6 % and Cl-
is 55% of the total salts by weight. The relative proportions of  Na+ and
Cl- in blood and seawater might be the basis of JFK¹s statement; if so, he
missed the more important point: The total salt concentration of seawater
(3.5 %, or 35 ppt) is nearly four times that of human plasma (0.9%, or 9
ppt), a difference reflected in their osmotic concentrations:

Plasma [osmotic]  ~ 300 milliosmoles/kg (includes proteins and other organic
solutes)
Seawater [osmotic]  ~ 1050 milliosmoles/kg

Had JFK stated that the percentage of salt in our veins is exactly that same
as that in the blood of fish living in the ocean, I wouldn¹t quibble (after
all, cladistics tells us that we are fish, albeit highly specialized fish):

[Na+]  
Human plasma:  138 millimolar (mM)
Cod (Gadus) plasma: 174 mM
Seawater:  470 mM

[Cl-]
Human plasma:  106 mM
Cod (Gadus): 150 mM
Seawater:   548 mM

The osmotic concentration of cod blood plasma (~ 310 mOsm/kg) is essentially
the same as that of human plasma. So, we really have fish blood ­ not
seawater- circulating in our veins (and arteries and capillaries, etc).
I know this is a bit off topic, but it does relate to how science is
presented to the general public. I¹m know President Kennedy had good ­ or
even noble- intentions, but spreading misinformation, albeit inadvertently,
doesn¹t promote scientific literacy.

Chuck
*   *   *   *   *   *   *
Dr. Charles E. Booth
Dept. of Biology
Eastern Connecticut State University
Willimantic, CT  06226

Ph: 860-465-5260
Email: booth at easternct.edu
FAX:  860-465-5213