Present Status of Coral Reefs in Southern Coastal Waters of Sri Lanka: A Base Study from Hikkaduwa to Tangalle

Abstract

Selected coral reefs were monitored to assess the current status of the reefs in Southern coast
of Sri Lanka. The underwater visual census (UVC) survey was conducted in September to
November 2014 at seven selected sites. i.e., Hikkaduwa, Rumassala, Weligama, Mirissa,
Polhena, Dondra and Tangalle in the Southern coast, namely. Line intercept transect method
(LIT) was used to estimate the coral and sessile benthic cover categories. Total of 84 surveys
transects, four transects for each site at three replicates were deployed at shallow depth
between 1 to 3 m. Environmental parameters were obtained to support the diversity
observations. Percentages of sessile benthic categories (live coral, dead coral, coral rubble,
rock, sand/silt) showed a significant differences among surveyed sites. The highest mean
coral cover was observed at Weligama (64.75%±17.71) followed by Mirissa
(49.97%±11.26), Polhena (21.57%±7.83), Hikkaduwa (19.68%±3.83), Dondra
(17.31%±7.84), Rumassala (12.5%±5.59) and Tangalle (5.08%±7.66). The highest mean
dead coral cover was at Hikkaduwa (36.05%±5.34) while the highest mean coral rubble cover
was observed at Polhena (31.95%±9.37). Altogether 14 coral groups were recorded including
Acropora sp., Pocillopora sp., Favia sp., Montipora sp., Millepora sp., Goniastrea sp.,
Favites sp., Podabacia sp., Pachyseris sp., Pavona sp., Leptoria sp., Porites sp., Galaxea sp.
and Echinophora sp. From which the abundant species were Acropora sp., Montipora sp.,
and Pocillopora sp. The highest mean Shannon diversity indices (H‟) for coral groups
showed at Mirissa (1.297±0.149) while the highest mean Evenness was at Rumassala
(0.895±0.054).Temperature, DO, salinity, conductivity measurements were in acceptable
levels which are favorable for reef growth. The TDS/TSS, concentrations of nitrate and
phosphate in all sites were greater than the critical levels for a sound reef health. Most of the
Southern coastal waters were observed degrading due to sedimentation, excess growth of
calcareous alga Halimeda sp., destructive fishing practices, coral trampling and poor coastal
management practices causing negative impacts in these reefs. These findings emphasise that
the need for adopting effective management and conservation measures to protect the high
coral diversity in Southern coastal waters of Sri Lanka.

Keywords: Coral reefs, Southern Sri Lanka, Environmental parameters, Coral reef
monitoring, Human disturbancesc