Marine Turtle Genetics and Biology
All seven species of sea turtles are globally protected. Of these, five species: green turtle, (Chelonia mydas), loggerhead turtle (Caretta caretta), olive ridley turtle (Lepidochelys olivacea), leatherback turtle (Dermachelys coriacea) and hawksbill turtle (Eretmochelys imbricata) nest in Sri Lanka. Population genetic affinities and stock structure of any of these five species nesting in Sri Lankan beaches are not known due to lack of data. All five species are listed as Threatened while green turtle is Endangered (EN) and loggerhead and olive ridley are in the Vulnerable (VU) category. Green turtles are the most abundant sea turtle species in Sri Lankan waters followed by olive ridleys and very few individuals of loggerheads. Because of the extremely low numbers, with as few as 50 nests or less per years, the loggerhead population nesting in the Sri Lankan beaches qualifies it to be listed as Critically Endangered (CR) according to IUCN Red List 2015 criterion D. There is no loggerhead nesting in India. In the Indo-Pacific Ocean, there are five distinct genetic stocks of loggerheads, however, the Sri Lanka population forms an additional genetic stock is not known. Analysing mitochondrial DNA (mtDNA) of sea turtles can determine the stock structure and whether the population is genetically unique or have affinities to an already known population in the Indian Ocean or elsewhere.
Coastal Community and Marine Turtle Hatcheries
Sea turtle hatcheries are well established in Sri Lanka. Although hatcheries are used as an ex situ conservation tool of sea turtles, their contribution towards conservation of sea turtles is highly debated. There are 13 hatcheries along the southwest coast of Sri Lanka. All the hatcheries are operated by private owners and their prime motive is profit, relying on tourists for their viability and poor ecological practices are employed due to lack of scientific know-how. However, hatcheries can make a positive contribution to sea turtle conservation if they are managed using proper scientific guidelines especially when in situ conservation of sea turtles is expensive and impractical. The common practice in hatcheries is that turtle eggs that have been purchased from suppliers are then buried in hand dug egg chambers inside incubation enclosures. Temperature of a sea turtle nest during incubation is critical to successful development of hatchlings and for the determination of their sex. Many ecological and physical factors such as rainfall, air temperature, nest depth, sand moisture and gas exchange affect the nest temperature. In hatcheries, the depth of relocated nests can vary as they as buried by the hatchery keeper. Nest depth can influence the nest temperature with deeper nests being constant because they are less affected by solar radiation and air temperature.
Artificial Light Pollution, Coastal Development and Microplastics
Sea turtles are the most adversely affected marine vertebrate by coastal development which destroys and alters nesting habitats and also increases the artificial light disturbing the nesting behavior of females and hatchling migrations. Following the cessation of nearly three decades of civil war in 2009, the number of international tourist arrival to Sri Lanka has sharply increased from 438,475 in 2008 to 2,333,796 in 2018 breaking all historical records. Beach holidays been one of the most favoured tourist attractions, many new hotels have been built along the coastal lines, especially in the southern, southwestern and eastern coasts of Sri Lanka. Major turtle nesting sites are also located along these coastal areas. We assessed the new developments along the coast for the past ten years and measured the artificial light using a handheld Unihedron Sky Quality Meter (SQM) in the major nesting beaches. During the last decade, several large hotels have been built along these coastlines, some of them were built on the edge of the beach ignoring the government mandated 100 m buffer zone along the south and west coasts and 200m buffer zone along north and east coasts preventing rebuilding in shoreline areas. In some places hotels the beach area is been used for tourist activities which can be disturbing and distracting the nesting females. Regulations on large constructions in undisturbed turtle nesting beaches and introducing turtle friendly lights to be implemented to mitigate the light pollution.
