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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