In ocean currents caused by differences in seawater density period, winds constantly above sea level and tidal especially in coastal areas. Ups and downs can also replace water in total and continuously so as to avoid water pollution. While the beach may change the distribution and dampen the flow. Flow has a positive and negative effect for the life aquatic biota. Flow can cause tissue ausnya jazad life due to erosion or teraduknya muddy substrate resulting in turbidity that inhibition of photosynthesis.
At other times, the benefits of the current is supplied food, dissolved oxygen, plankton deployment and removal of CO2 as well as the remains of marine products (Romimohtarto, 2003). Flow benefits for many biota are concerns the addition of food for the biota and disposal of dross. For algae shortage of chemicals and CO2 can be met. As for animals, CO2 and waste products can be removed and O2 remain available. Flow is also an important role for the spread of plankton, both holoplankton and meroplankton.
Figure 11. Use of currents on mariculture
Especially for the last group consisting of eggs and fry-fry basic invertebrates and fish. They have the opportunity to avoid food competition with the parent-parent, especially that live attached like barnacles (Belanus spp.) And mussels (Mytilus viridis). The fact that can not be tolerated against the strong and weak currents will hamper mariculture activities (Ghufron and Kordi, 2005).
Flow is also very important in the circulation of water, carrying dissolved material and suspended solids (Dahuri, 2003), and can have an impact on the presence of organisms tacks. Water flow rate will vary vertically. Water currents in waters that lotik generally turbulent water current that moves in all directions so that the water will be distributed to all parts of the waters. Flow is a very broad movement of water occurs in all the oceans of the world. These flows have particular significance in determining the direction for the cruise ships.
The speed of water flow to the cultivation of floating net cages in the sea should not be more than 100 cm / sec (Gufron and Kordi, 2005) and lower flow velocity of 25 cm / sec. As for the seaweed 20-30 cm / sec and pearl oyster ranges from 15-25 cm / sec (DKP, 2002). In the current tapering ecosystem is influenced by the strength of the wind, the stronger the wind will cause the currents stronger and deeper influence the water layer.
At letik waters flow velocity generally ranging from 3 m / sec. It is however very difficult to create a limit on the flow rate. Because the flow of water in an ecosystem greatly fluctuate from time to time depending on the fluctuations in discharge and water flow and substrate conditions that exist. River flow velocity is affected by the slope, the fertility level of the river. Depth and keleburan river, so that the flow velocity along the river can vary which in turn will affect the type of substrate river.