Carbon dioxide absorption measurement of seagrass Enhalus acoroides Linn. By infrared gas analyser in closed system

Abstract

A study on CO₂ absorption of seagrass Enhalus acoroides Linn. using CO₂ flux measurement technique in close system. The chamber was made from the transparent glass 29 x 39 x 40 cm. The top of the chamber was closed with a 1.2 μm transparent PE sheet. The CO2concentration in the air was measured with an infrared gas analyzer model LI-820 (LI-COR, Inc). The sampling tube was used to circulate the air from the chamber to the analyzer and then back to the chamber. In the chamber, the sea water with salinity 30 ppt was filled at 15 cm depth. The measurement was done every 1 hour from 8:00 am to 5:00 pm. Light intensity, air temperature and humidity, water temperature and pH were also recorded at the measurement time. The CO₂ absorption was calculated by the method modified from Silva et al. (2008). The result found that CO₂ absorption was change correlated to light intensity. The lower CO₂ absorption was found in the morning then raise up to highest at 1:00 pm then lower in the afternoon. The highest CO₂ absorption of seagrass was 0.3 μmol CO₂ m^-2s^-1 .The pH of sea water for the chamber without seagrass was constant at 6.6 through the experiment. The pH of sea water for the chamber with seagrass was 5.8 in the morning then raise up to 7.5 at 5:00 pm.