FINDINGS from a recent study of endangered green sea turtles at two sites in Sabah suggest that these aquatic creatures’ health is potentially sensitive to the quality of their foraging habitats
The two sites of Balambangan Island and the Kudat Peninsula in the Tun Mustapha Marine Park off the north-west coast of Sabah are only some 40km apart but differences in the turtles’ condition are noticeable.
In the paper titled “Variations in Body Condition of Green Turtles (Chelonia mydas) in Two Nearby Foraging Grounds Indicate Their Sensitivity to Foraging Habitats”, the researchers say coastal seagrass habitats are critical foraging grounds for the animals.
“However, these habitats are vulnerable to anthropogenic [manmade] effects, potentially leading to their degradation with consequent impacts on the health of foraging green turtles,” say the researchers in the paper published in Aquatic Conservation: Marine and Freshwater Ecosystems in November 2023.
In the study, the two foraging habitats were surveyed by capturing turtles and evaluating their physical condition and then assessing seagrass cover. The team observed and measured 42 turtles captured off Balambangan Island and 53 off Kudat. Blood samples were also taken from these animals before they were released back to the sea.
Evaluation points included carapace length and body weight to determine Fulton’s body condition index, as well as barnacle occurrence and abundance – excessive barnacle cover can be a sign of general bad health in a sea turtle. Fulton’s body condition index (BCI) is used in fisheries biology to assess the overall health of an aquatic animal based on its weight and length.
According to the paper, “Despite having similar genetic compositions, the Kudat mainland aggregation had significantly higher body size… than the Balambangan Island aggregation”.
Among other measures, the study found the average curved carapace length of green turtles in Kudat’s coastal waters – where seagrass cover is higher – to be 61.7cm (±14.5cm), with the animals weighing in at 30kg (±22.2kg). In contrast, green turtles in Balambangan Island’s waters have an average curved carapace length of 51.6cm (± 8.1cm), and a weight of 17.3kg (±7.7kg).
The Kudat turtles were also found to have significantly higher barnacle occurrence (Cheloniba testudinaria) at 78.8%, compared with 31% in the animals in Balambangan Island waters.
According to the researchers, the differences in BCI between the two aggregations cannot be attributed to size and barnacle-occurrence differences, suggesting that the foraging habitat is the primary factor affecting the turtles’ condition.
Seagrass beds in waters around Kelambu Island, Sabah. The condition of this habitat affects the health of the green sea turtles that feed on the seagrass. — GAVIN JOLIS/Universiti Malaysia Sabah“Seagrass cover at Kudat mainland was only slightly higher than at Balambangan Island.
“This suggests that the body condition of green turtles is potentially sensitive to the quality of foraging habitats, such as nutrients and water quality,” says the team.
The researchers in the study are Hideaki Nishizawa of the Graduate School of Informatics, Kyoto University; Juanita Joseph and Gavin Jolis of the Borneo Marine Research Institute at Universiti Malaysia Sabah (UMS); Sabah Wildlife Department’s Hussien Muin; Kudat Turtle Conservation Society’s Sofia Johari; Ejria Saleh of the Small Islands Research Centre at UMS; and Irwan Isnain of Sabah Parks.
Human threats
Among these threats are pollution comprising plastic debris and chemical runoffs from coastal development as well as marine debris, artificial light pollution interfering with nesting habits, habitat destruction, becoming bycatch, and being hit by boats.
Weighing a turtle on Kimihang beach, Kudat, Sabah. A turtle’s size and weight can indicate the population’s health. — GAVIN JOLIS/Universiti Malaysia SabahChemical runoff can directly affect water quality, impacting both turtles and their food sources, he says, and plastic debris not only contaminates the water but also poses ingestion risks.
The turtles tend to mistake floating plastic for jellyfish, which is an occasional part of their diet, and the indigestible plastic eventually kills them.
“Activities like coastal development, dredging, mining, and fish bombing can significantly degrade and destroy vital habitats for marine turtles,” he explains in an email.
According to Jolis, there are several key differences between the Kudat mainland and Balambangan Island despite the proximity of the two sites in the marine park.
While both the island and the mainland pose human-made threats to turtle habitats, Jolis says their specific nature and sources differ due to the different human activities and development patterns in each area.
Jolis: ‘Activities like coastal development, dredging, mining and fish bombing can significantly degrade and destroy vital habitats for marine turtles.’ — Pic providedOn the Kudat mainland, sites like Kelambu Island, Kimihang Beach, and Lampu Island are inhabited areas with aquaculture farming as well as recreational activities like swimming, snorkelling, and beach camping.
“These activities bring risks such as pollution, too much light at night, trash in the ocean, and habitat destruction.
“Additionally, the recent start of silica mining near our study sites could soon cause problems for the habitats, potentially resulting in adverse environmental consequences – unless adequate mitigation measures are implemented,” Jolis says.
The Balambangan Island’s study site, on the other hand, is mostly uninhabited but sits next to a fishing village, with a small river flowing from the island’s north into the site.
“Here, the main threats are becoming accidental catch in fishing gear, and collisions with boats.
“Notably, poaching of turtle eggs and harvesting of turtles from their foraging grounds still persist in the Balambangan area, exacerbated by its proximity to the international border which makes it an easy target for poachers,” he points out.
Beyond still waters
The second largest marine park in Malaysia at 898,762ha and with over 50 islands and islets, the Tun Mustapha Park is also home to Malaysia’s second largest concentration of coral reefs.
Luconia Shoals in Sarawak’s waters is now the country’s biggest marine park at over one million hectares.
Lying within the Coral Triangle – considered a major global area of marine biodiversity and conservation – the Tun Mustapha Park hosts 82 species of coral, 715 species of fish, 50 species of shellfish, and 130 species of seaweed, besides the green turtles.
Like the Kudat mainland, Balambangan Island may face a possible threat from silica mining impacts following reports that there are plans to start quarrying there.
Jolis warns that silica mining on Balambangan Island could significantly contribute to negative impacts on the marine environment and turtle populations.
“Both areas face imminent challenges, particularly with the potential expansion of silica mining activities,” he says.
It was reported last year that protests have arisen from villagers – mostly fisherfolk – in Sikuati, Kudat, as well as conservationists and the area’s diving community over the possible threats from a silica mining project. Besides contamination from mining activity, protesters are also concerned about the construction of a jetty.
Reports have also emerged of another silica mining project that would be located on the northern part of Balambangan Island. In June 2023, Sabah’s Environ-mental Protection Department director Vitalis Moduying was quoted as saying that the state’s authorities are monitoring the project.
Tagging a turtle before releasing it back into the sea. — GAVIN JOLIS/Universiti Malaysia SabahJolis says their study has, for instance, highlighted the potential impact of silica mining at Kg Bangau-Bangau located in the town of Semporna on Sabah’s eastern coast.
“If adequate mitigation measures are not implemented, the runoff from mining operations could harm the nearby marine ecosystems, affecting food sources and the overall health of foraging turtles.
“Additionally, constructing large structures like a jetty for mining can disrupt sandy beach profiles, interfering with nesting sites and making them less suitable for turtles to lay their eggs.
“Although our study does not specifically focus on Kg Bangau-Bangau, we have suggested that any mining activities near any turtle habitats, like seagrass beds, coral reefs, or sandy beaches, could destroy these vital environments and ultimately harm turtle populations in the long term.”
Jolis stresses that it is important to note that the green turtles foraging in Kudat and Balambangan Island waters are estimated to come mainly from Sarawak and Sabah’s Turtle Islands National Park where they were born and hatched.
“These adult turtles migrate from their birthplace to foraging grounds and then back again to lay eggs.
“If they encounter human-made threats in their foraging areas, they may be unable to return to their birth beaches to nest,” he explains.
The threats in Kudat and Balambangan Island waters, he adds, could subsequently lead to a decrease in nesting numbers in Turtle Islands Park, which lies in the Sulu Sea some 3km north of Sandakan, Sabah.
Swimming with turtles
Based on the results of the study, the team recommends that long-term monitoring and research be conducted, particularly on water and sediment quality.
“Long-term studies provide valuable insights into trends, potential threats, and the effectiveness of conservation measures,” says Jolis.
“The monitoring helps identify the causes of changes, such as pollution or habitat degradation, enabling targeted conservation actions,” he says, adding that it is also crucial in understanding the health of foraging habitats and their impact on the health of turtles over time.
Another recommendation is to identify and protect critical nesting and foraging habitats within the park, including implementing measures to safeguard key sites from human-made disturbances.
“It is imperative to minimise or eliminate human-made threats like mining and unsustainable coastal development in the foraging habitats of turtles,” Jolis says.
This involves promoting sustainable coastal management practices that prioritise the conservation of marine turtle habitats, such as implementing zoning regulations and mandating Environmental Impact Assessments for all development projects.
Effective conservation, says Jolis, requires the active involvement and support of local communities as well as local and state authorities.
“Providing training and education programmes can help raise awareness about the importance of marine turtle habitats and the need for conservation efforts.
“Empowering local communities to participate in monitoring, enforcement, and sustainable livelihood initiatives fosters a sense of ownership and responsibility for marine turtle conservation within the community.”
