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BUOYANCYBy group 7
What is a buoyancy?
Buoyancy is the upthrust generated bythe
displacement of the ambient medium.
Aquatic animals are considered to be
neutrally buoyant when the resulting
upthrust and weight of the animal are equal.
Mechanisms of buoyancy
Static
Adjustable
Static Buoyancy
Static buoyancy mechanisms usually involve a
long-term reduction in the relative density of the
animal, either by the inclusion of low-density
metabolically derived substances
Adjustable Buoyancy
Adjustable buoyancy mechanisms is usually
associated with regular vertical movements of
many marine and freshwater animals.
Adjustable buoyancy usually adapted for by
requirement.
According to Dr. Richard Frange,buoyancy control mechanism include:
Mechanism of vascular, there are three vascular
area for gas exchange between bubbles and pools
of blood flow.
Pneumaticus duct is a channel that connects the
esophagus and swim bladder
Kinds of Buoyancy
Positive buoyancy, when an object floats,
Negative buoyancy, if an object sinks,
Netral buoyancy, if the object can be floated
Source: http://spot.pcc.edu/~lkidoguc/Aquatics/AqEx/Water_Buoyancy.htm
Flexible Buoyancy Chambers
The Siphonophore Float
The Fish Swimbladder
Physalia physalis
Spirula
http://www.whoi.edu/page.do?pid=10897&i=701&x=114
Sepia
Fish Swimbladder Swimbladder is the organ-shaped air-filled sac
that it serves fish remedy set a float in the water,
so the fish do not need to swim continuously to
maintain its position.
Fish Swimbladder
Table representative species of the four main horizontal oceanic layers
Depth (m) Presure (atm) Layer Species
0-150 1-16 Epipelagic Sun-fish
150-1000
16-101
Mesopelagic
Lanternfish,
melamphaids,
stomiatoids, trichiuroids
gonostomatids
1000-4000
101-401
Bathypelagic
Cyclothone,
gonostomatids,
xenodermichthys
Near the sea
floor
Up to 400
Benthopelagic
Macruorids,
eretmophorids, brotulids
Hydrostatic pressure
Hydrostatic pressure is pressure generated by hydrogen, in influencing by deepness, specific mass, gravitation massa, beside that is the weight of the water column is usually measured in atmospheres (atm).
P = r x g x z
Where:
P = hydrostatic pressure (pressure/unit area)r = density of water (g/cm3)
g = acceleration due to gravity (980 cm/sec2)
z = depth below the water surface (cm)
Rigid Buoyancy Chambers
Nautilus, Spirula and Sepia are the only living
chepalopods which have retained buoyancy mechanisms
in the form of a chambered shell.
In Sepia, for which most information is available, each
main chambers is subdivided by about six thin
sublamellae which run parallel with the thicker walls or
lamellae of the chambers
The cuttlebone of sephia
The depth range is limited by the strength of he cuttlebone and the osmotic pressure
gradient
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