EFFECT OF ACIDIFICATION ON THE ABUNDANCE OF FISH LARVAE IN REZU KHAL ESTUARY, COX’S BAZAR COASTS, BANGLADESH

Abstract

These studies mainly focus on to understand how ocean acidification concise recently hatched larvae stocks, their growth, recruitment and mortality rate that influence larvae abundance. This study was carried out from January to December 2021, in the Rezu khal Estuary, Cox’s Bazar which is one of the important estuarine systems in Bangladesh. Different fish larvae were collected by using Bongo net (500μm) which was being towed from bottom to surface. During sampling period, a total of 1,511 larvae were found, mean density was 125 /1000 m3 of fish larvae observed in laboratory. The average range of hydrological parameter were found 27.650C for surface water temperature, 8.37 for pH, 104.17 mg/l for alkalinity, 23.98 psu for salinity, which were within ideal range during study period. Ocean acidification factor including pCO2, HCO3-, CO32-, DIC-, ΩAragonite, ΩCalcite were also determined by using “Seacarb” package of R programming language and validated from CO2SYS software for CO2 system calculation. The mean value of ocean acidification factor such as pCO2, HCO3- ,CO32-,DIC-, ΩAragonite, ΩCalcite was recorded 82.94 μatm,.00065 mol/kg, .000125 mol/kg, .000808 mol/kg, 2.3364 and 3.6593 respectively. The results showed an insignificant relationship among pCO2, pH and larvae abundance in Rezu Khal. Larvae abundance was positively correlated with pH and negatively correlated with pCO2. However, there was a strong negative correlation between pCO2 and pH. Using these outputs, impact of ocean acidification on fish larval abundance can easily be identified. This research will help decision makers to take appropriate decisions on reducing the degree of acidification in Cox’s Bazar coasts of the Bay of Bengal.