NATALIE PUDALOV's POST--UNABLE TO SIGN IN
During Professor Metzler’s
11/08/16 lecture on liquids, we talked about how the pressure an object
experiences in liquid can be calculated by determining the magnitude of force
perpendicular to an object and the object’s area. Ultimately, we talked about how
the area of an object could be ignored when trying to determine the pressure an
object experiences at a certain depth. I work in a comparative physiology lab
at Colgate and I was recently tasked with switching the tanks for the
sheepshead minnows—the tank had gotten dirty because the fish produce all sorts
of waste from their diet of plant material, algae, and detritus. In order to
switch their tanks:
1.
I took
them out of their dirty tank and placed them in a small fish bowl. Then I
cleaned their dirty tank.
2.
I placed
a few rocks at the bottom of the clean tank and put about 1 L of water in the
35 cm X 35 cm X 35 cm tank.
3.
I placed
the fish bank in the clean tank
4.
I put
about 10 L more into the tank
As I did this, I wondered how
much the pressure changed for the fish. With only 1 L of water, I assumed that
the fish were nearly at the top of the water and the pressure they experienced
from the water was negligible. As soon as I added the water back to their tank,
they swam to about half the tank’s height (17.5 cm=.175 m)
P0= 1.01 X 10^ -5 N/m2
PF=
(density water)(gravity)(depth)
= (1000 kg/m3)(9.8 m/s2)(.175)+
1.01 X 10^-5
=1715 Pa
ΔP= Pf-P0= 1715-(1.01x 10^-5)= 1714.99 Pa
This is consistent
with what reports say about where sheepshead minnows tend to live: “They prefer
quiet, shallow waters and have been found in saltwater bays and estuaries, as
well as coastal inland areas such as creeks, canals and ditches”
(tpwd.texas.gov).
However, I was still curious
about how deep-sea fish survive extreme pressures. Only about 2% of known
marine species live in the deep-ocean area, called the pelagic environment. Within
the pelagic zone, there’s the bathypelagic (1000-4000 m deep) and the
abyssopelagic zones (4000-6000 m deep).
Bathypelagic: 9.8
x 106 Pa-3.92 x 107 Pa
(1000
kg/m3)(9.8 m/s2)(1000)=9800000= 9.8 x 106 Pa
(1000 kg/m3)(9.8 m/s2)(4000)=
39200000= 3.92 x 107 Pa
Abyssopelagic: 9.8 x 107 Pa-
5.9 X 107 Pa
(1000
kg/m3)(9.8 m/s2)(4000)=9800000= 3.92 x 107 Pa
(1000 kg/m3)(9.8 m/s2)(6000)=
58800000= 5.9 X 107 Pa
In the bathypelagic and abyssopelagic regions, no light enters
this area of the ocean, so bioluminescence is common! This part of the ocean is
also characterized by extremely low temperatures and low oxygen levels.
In comparison to the sheepshead
minnows in the lab at Colgate, deep-sea organisms at 4000m (in between bathypelagic and abyssopelagic) experience over 20,000 times the pressure
that a sheepshead minnow does.
Sheepshead
minnow pressure: (1000 kg/m3)(9.8 m/s2)(.175)= 1715 Pa
Deep-sea
organism (like the humpback anglerfish) pressure: 3.92 x 107 Pa
Ratio: 3.92 x 107
Pa/1715 Pa=22857
This led me to do some
research on the biology that allows deep-sea fish to travel to such depths. How
do these organisms not get crushed by the enormous pressure they experience?
Unlike humans, fish do not
have compressible air pockets that would burst at really high pressures—thus
the pressure balance can be maintained in between their bodies and the water.
In addition to other adaptations, deep-sea fish have a compound called
trimethylamine oxide, which basically ensures that proteins and other important
molecules do not compress, denature, or completely alter their structure under
extremely high pressures. These high pressures also mean that the cell
membranes of fish are unsaturated—making them more loose and flexible. (A rigid
cell membrane is usually bad for organisms). Some research also indicates that
sulfur linkages between molecules in the cell membrane may play a key role.
Evidently, studying these organisms is made more difficult by the fact that
humans can’t actually travel that deep.
References:
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