Abstract:
A comparative study on some limnological and
hydrobi ol ogi cal aspects o-f three southern coastal water
bodies- Rekawa, Kalametiya and Lunama were carried out from
March 1984 to June 1985. The three lagoons at Rekawa,
Kalametiya and Lunama differed in geomorphology,
hydrography, hydrology, and in physicochemical parameters.
The main parameters dealt with were morphometry,
temperature, salinity, dissolved oxygen content, light
transparency, suspended matter, organic content and BOD of
bottom sediments, pH, alkalinity, soluble reactive phosphate
concentration, chlorophyll 'a' concentration, primary
productivity and zooplankton abundance; in both time and
space.
The hydrographical regime of Rekawa lagoon was
seasonal and closely followed the monsoon cycle but changed
however from September 1984 due to an irrigation scheme.
The Kalametiya lagoon is comparable to a running water
body. The Lunama lagoon remains almost stagnant.
Seasonal variation of temperature in all three
lagoons closely followed changes in air temperature;
salinity variations were closely related to the monsoon
rain patterns. In all the three lagoons the major factor
controlling dissolved oxygen was temperature.In Rekawa the
factors controlling transparency, suspended matter, organic
content of bottom sediments was wind, while in Kalametiya
it was rainfall. The pH and alkalinity were closely related
to the salinity variations, and soluble reactive phosphate
was available at sufficiently high levels throughout the
year.
Overall production rates and its seasonal
-fluctuation was much higher at Rekawa than Kalametiya and
J
Lunama. Annual gross primary production in Rekawa,
Kal amet i ya and Lunama were
nn'7cr
7 / vJ
c» : .y C h a - 1yr ~ 1 , 2175 kg
C ha- 1yr * and 1890 k g C h a~1yr~1 respect i vel y ■ The
net :gross production r at i o s , and the assi mil at i on rati os
were calculated and correlation analyses were performed to
evaluate how the physicochemical parameters and hydrobio.logical
’ factors are related to the productivity changes in
the three lagoons. Seasonal abundance of zooplankton was
not associated with the salinity regime, but it was
significant1y correlated with biovolume of phytoplankton,
as well as chlorophyll "a" and primary productivity,
suggesting food was more important than salinity.
Interrel ationships between different parameters within and
between lagoons were evaluated.
