Chenical Factors

Chemical factors

*some of the chemical properties are:

-elements available

-oxygen

-salinity

-PH

Available elements

*elements such as nitrogen, calcium, phosphorous, iron, silicon, and manganese are needed in various amounts by organisms to live.

*in many coral reefs, the water is very poor in elements.

Dissolved oxygen

*fish need oxygen for respiration.

*different fish need different amounts of oxygen depending on their size, species, and activity.

*if the oxygen level drops below the optimum for an individual fish, its metabolic rate drops and its activity is reduced.

*Oxygen content of sea water is higher:

-at the sea surface where it’s more equilibrated with the atmosphere

- Around photosynthetic marine plats

-in colder water in which it’s more soluble

*below the thermocline, where there is a sudden change of temperature from warm above to cool below, the oxygen content can be very low and can seriously affect fish and other marine life.

*skipjack tuna cannot get enough oxygen below the thermocline and are therefore limited to surface water.

*oxygen is more soluble in cold water than warm water.

*a warm lagoon is therefore a restricted environment where only small low oxygen consuming organisms like ghost crabs, Picasso fish, and gobies can live.

PH of water

*the term PH denotes the concentration of fee hydrogen atoms-ions.

*life is only possible if blood is kept within a narrow range of PH.

*the normal range in terms of hydrogen ion concentration (PH) is from 7.35 to 7.45.

*it’s important for the internal environment to be maintained at these levels of PH to sustain life and optimize the body’s ability to function properly.

Salinity of water

*the average salinity of the sea is 35 part per thousand (ppt), but in an atoll lagoon it can be as high as 37 ppt and in an estury it can be very low.

* Salinity affects:

-osmoregulation in fish

-the buoyancy of pelagic eggs

-movement of species such as salmon

*different species have different salinity preferences

*stenohaline: organism which tolerate a narrow range of salinity

*euryhaline: organisms which tolerate a wide range of salinity.

Physical factors

*some of the physical properties include:

-temperature

-light

-substrate

-wave action

-currents

-density

-pressure

Temperature

*organisms respond to different temperatures(stenothermal,eurythermal)

*water temperature affects:

0feeding

-growth

-swimming speed

-spawning

-migration

* Fishes are ectothermal animals

Tolerance

*some organisms have a wider temperature tolerance range than others

*those with a small range are called stenothermal

*those with a larger range are called eurythermal

*in shallow water, where temperature fluctuates more eurytherms are predominant