7 subtropical regions Utama, 2005. This is because much cloudy cover in many
tropical areas compared with sub tropic. Temperature changes slowly from the coast towards offshore, temperature generally is higher in coastal areas because
the sea could absorb sunlight easier while for the sea it is not easy to change the temperature when the environmental temperature does not change, commonly the
temperature of the offshore is stable. Temperature is one of the most important factor for living organisms in the ocean, because temperature affects both
metabolism and proliferation activity of any organism. Average temperature between each measurement point does not differ significantly, which range from
21
o
C – 32
o
C for seaweed and 21
o
C – 32
o
C for pearl oyster, where the temperature was within the category is suitable for developing marine farming area. The range
of temperature is not large due to Indonesian waters have a uniform temperature pattern Wiradisastra, 2004.
2.1.1.4 Acidity
Acidity or Potential of Hydrogen pH measured concentration hydrogen ion in water, indicated the acid and alkalie degree of sea water. Generally, acidity scale
is from 0 to 14, the mean value is a neutral number 7. Measurement of acidity is very important because acidity values affect the solubility and availability of
various nutrition for the organism. Sea water has ability to sustain fluctuating changes in acidity. pH or water acidity is one of the factors affecting productivity.
pH is measured during the study which ranged from 7.2 - 7.9 ppm for seaweed and 7.2 – 7.9 ppm for pearl oyster. The pH ranges show that the open water is
productive. Changes in pH can have bad consequences for the life of sea biota, either directly or indirectly Wiradisastra, 2004.
2.1.1.5 Salinity
Salinity is the concentration of soluble ions mineral in water and expressed in mg per liter ppm, or the amount of salt in grams per kilogram of sea water. Sea
water generally contains 3.5 salt, dissolvable gases, organic materials and some particles of insoluble substances. Salinity is also influenced by the osmotic
8 pressure; the more the higher salinity the more higher the osmotic pressure,
another cases influence by tidal and seasonal. Salinity around the estuary tends to decrease, but during the dry season when the flow of the river water decrease, sea
water flow further to around estuary so that the increased salinity in estuary. In contraraly in the wet season, there is an increase flow freshwater from rivers
which empty into the sea, so salinity in the estuary decrease. Salinity is very influential on the cultivation of seaweed and other organisms, because each
organism has a certain range for life. Salinity measured during the study ranged from 33 - 34 ppt for seaweed and 33 – 34 ppt for pearl oyster. Many
environmental factors affected the changes in the salinity such as: water circulation, evaporation, precipitation and flow of the river to the estuary
Wiradisastra, 2004.
2.1.1.6 Depth of Sea Water
Depth of sea water is one of the most important parameter in studying the dynamics of the sea. Slight differences in the depth for example due to
differences in surface heating will result to differences in ocean currents. Therefore, the determination of depth is important in oceanography. Water
pressure increases according to the depth of the sea. Depth of sea water is usually measured by using the echo sounder or CTD conductivity, temperature, depth.
The depth is measured using CTD based on the value of pressure. Depth Measurements are made at selected points to represent the whole mapped area.
The information about the components of this data is obtained from field, the lowest is about 1.4 meter and the highest depth is 85 meter. Reference data which
have been collected and processed from various maps are then overlaid and spatial interpolation technique Wiradisastra, 2004.
2.2 Interpolation of Surface Analysis
