(LATO) IN LOWERED SEAWATER pH - Central Visayas Campus ...

surface seawater, for a given temperature and salinity, is the pH of seawater in
equilibrium with CO2 in the atmosphere (Skirrow and Riley, 1975).
The seawater has a good buffer system. This means that it would keep in track
the balance within its environment. The seawater’s buffer system equilibrates back
and forth the changes and stresses it encounters and thus, pH stays relatively constant
(http://www.livingreefs.com). However, when too much stress is encountered, the
seawater’s buffer system lessens its capabilities to maintain the balance within its
environment.
Dissolved carbon dioxide occurs as carbonic acid and its presence in water
lowers the pH. During the day when plants are illuminated and photosynthesis is
occurring, the dissolved CO2 is taken up from the water and the pH rises. At night
when no photosynthesis is taking place and the CO2 builds up thereby contributing to
a falling pH. On the other hand, high alkalinity promotes calcification, encouraging
the rapid growth of calcifying algae. High alkalinity combined with calcium dosing
promotes the precipitation of phosphate and this limits algae growth
(http://www.livingreefs.com). Temperature inversely controls the solubility of oxygen
in water; as temperature increases, oxygen is less soluble. In contrast, there is a direct
relationship between atmospheric pressure and DO; as the pressure increases due to
weather or elevation changes, oxygen solubility increases
(www.uwgb.edu/watershed). Low concentrations of dissolved oxygen leads to an
acidic environment, or lowered seawater pH (RiverTrends Manual, 2010).
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