Abstract:
Jaffna Lagoon, located on the Northern coast of Sri Lanka, is a significant habitat for
marine life, yet its water quality and the role of environmental parameters on plankton
distribution and abundance remain unknown. The present study aims to investigate the
water quality of Jaffna Lagoon, plankton diversity, abundance, and their relationship
with water quality parameters. Water samples were collected from 20 different
locations between September 2021 and March 2022, and water quality parameters and
plankton samples were analyzed. The results revealed that the water quality of Jaffna
Lagoon was highly variable, with pH ranging from 7.67 to 8.52, dissolved oxygen ranging
from 5.34 to 8.76 mg/L, salinity ranging from 20.5 to 29.5 PSU, temperature ranging
from 26.06°C to 29.98°C, total nitrate ranging from 10x103 mg/L to 21.9x106 mg/L, and
total phosphate ranging from 0.01 mg/L to 0.32 mg/L. A total of 13 species belong to 12
families of planktons were identified, viz., Coscinodiscus granii, Leptocylindrus minimus,
Gyrosigma balticum, Woronichinia elenkin, Acartia sp., Gastropod larvae with ciliated
foot, Chaetoceros vanheurckii, Melosira sp., Cymbella cuspidata, Cymbella lanceolata,
Chaetoceros costatus, Closterium limneticum and Protoperidinium pellucidum.
Gyrosigma balticum was the most abundant plankton species (13%) in the lagoon,
followed by C. granii (10%) and C. vanheurckii (10%). The total phytoplankton abundance
fluctuated from values of <104 cells L−1 to values >2 × 106 cells L−1. The regression analysis
was performed to examine the relationship between plankton abundance, temperature,
and nitrate content. These findings contribute to the understanding of the ecological
status of Jaffna Lagoon and can inform the development of sustainable management
strategies for the lagoon ecosystem.
