- Indonesia has a wealth of marine lake biodiversity, for example Lake Kakaban on Kakaban Island, and Lake Haji Buang on Maratua Island, Berau Regency, East Kalimantan.
- Haji Buang Lake has unique biodiversity that has not been widely explored such as stingless jellyfish, colorful sponges , starfish and sea cucumbers.
- This seawater lake mixed with fresh water needs to be protected from a number of threats because its habitat is very sensitive, for example invasion by foreign animals, waste and human movement.
- A number of activities that need to be watched out for include releasing foreign biota into lakes, and the possibility of transmitting pests from outside waters, for example via boats and other tourist facilities.
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| The Unexplored Unique Biodiversity of Haji Buang Sea Water Lake |
A unique starfish from Lake Haji Buang caught the attention of a young researcher. This lake is a brackish water lake, mixed with fresh sea water, because the location of the lake is on a small island in the middle of the sea between Kalimantan and Sulawesi.
Not only because of its morphology with lots of soft bumps and velvety skin, but also its color and grape face. Moreover, starfish are known to be fussy about brackish water, a mixture of fresh and sea water.
It was this sea star that brought Anargha Setiadi, a researcher from the Research Center for Climate Change, University of Indonesia (RCCC-UI) to go back and forth to Lake Haji Buang on Maratua Island , Derawan Islands, Berau Regency, East Kalimantan. This island is one of the outer islands of Indonesia which is close to Sarawak, Malaysia.
It wasn't just starfish that he found in the lake. There is a variety of unique biodiversity that can be found, such as stingless jellyfish, clusters of sponges with interesting morphology, and seagrass beds.
When seen underwater, the grape-faced starfish is metallic blue, but when brought to the surface it is black. Agha, as Anargha is known, started paying attention to the various animals and biodiversity of Lake Haji Buang around 2010-2012 in a photo gallery on Facebook, while studying for her undergraduate degree in Biology at the University of Indonesia. Continuing visits in 2017 and 2019. It was not surprising that he saw the changes that had occurred in the beauty of this lake, which seemed calm and dark.
Agha describes this lake as being like an aquarium with colorful coral flowers. When I first swam several years ago, there were quite a lot of types of jellyfish. "Each seawater lake has genetically different types of animals, even though at first glance they look the same," he said when we met in Bali. He is completing research in a laboratory in Bali. For example, golden jellyfish (Mastigias sp.). The gold jellyfish moves to look for the sun, in the morning it is near the pier, in the afternoon it moves to the middle of the lake.
According to him, compared to Lake Kakaban, another popular jellyfish lake in the Derawan Islands , the view of Lake Haji Buang is darker and seems mysterious. It could be because it is smaller, shady, with hills, and less sunlight.
During his descent in 2017, Agha found more small box, gold and moon jellyfish. However, the number is less than in 2008. Looking at archived photos, you can see jellyfish filling the lake. He compared the jellyfish lake at that time to drinking cendol without sauce.
Agha calls it SpongeBob Lake, the title of a cartoon about the underwater world, because of its diversity of animals. Under natural conditions, around 2017-2019, Lake Haji Buang was inhabited by various species of soft-bodied invertebrates and small fish. The bottom of the waters is covered by colorful sponge formations and stretches of green algae (seaweed) and seagrass.
In the middle of the lake's waters, it is inhabited by swarms of stingless jellyfish and various types of small fish (dragonfish, gobies and julung-julung are common in the Berau location). Meanwhile, the bottom of the waters are also inhabited by molluscs such as oysters and gastropods/snails, nemertea worms, echinoderms such as sea stars ("lake stars") and snake stars, as well as crustaceans such as small purple crabs and cave shrimp.
There are no true coral reefs in Haji Buang, because the water is quite brackish and has a low pH (slightly acidic). The shores of seawater lakes tend to be covered by mangrove forest vegetation which supports native biota.
The trip to Lake Haji Buang from Jakarta took the route to Berau Airport, then he stayed overnight in Tanjung Redep, then departed by speedboat to Maratua Island for around 3 hours. You can stay in Payung-payung village or Tanjung Harapan.
Haji Buang Lake is considered to have not been explored much. Only one new species was described in 2019, namely the starfish species ( Limnasterias oinops ) which is thought to be endemic. This species has an impressive number of characteristics with specific adaptations to lake ecosystems such as tolerance to brackish water and rainwater, large gill protrusions (papulae), and a thin body frame.
Get to know sea water lakes
Agha explained the characteristics of this lake. A seawater lake (also called a sea lake/ marine lake /salt water lake) is an enclosed body of water. This type of water is connected to the surrounding sea through cracks, vessels and underground tunnels, so the water is influenced by sea tides.
Lakes with significant jellyfish populations are often called "jellyfish lakes . " In the world, seawater lakes and similar ecosystems can be found in clusters in several locations such as Berau (East Kalimantan), West Papua; Vietnamese; Republic of Palau (a country in the Micronesia region, 971 km from the northeast side of Halmahera); and the Bahamas Islands (Atlantic Ocean).
Due to its relatively isolated nature from the surrounding sea, seawater lakes can act as natural laboratories for the evolution of living things. Saltwater lakes originate from dry karst valleys and inlets, flooded by rising sea levels. Sea water seeps in through karst veins, which is thought to have occurred after the last ice age ( Last Glacial Maximum ), or around 18,000 years ago.
In the Derawan Islands, Berau, sea water lakes are on Kakaban Island (Lake Kakaban) and Maratua Island (Lake Haji Buang). Kakaban is a seawater lake with the largest population of jellyfish (jellyfish lake) currently known. It covers an area of around 400 hectares and is one of the favorites for tourism in Berau, with its large flocks of jellyfish.
Meanwhile, Haji Buang Lake is still unknown, and is located near paved roads, the airport, residents' gardens and accommodation on Maratua Island with an area of around 14 hectares. The entrance to Haji Buang Lake is located near the side of the road, in the Payung-Payung Village area. When observed in March 2023, the two lakes were still surrounded by dense and natural forest vegetation.
Lake Kakaban and Lake Haji Buang have four types of jellyfish, namely golden jellyfish ( Mastigias ), upside-down jellyfish ( Cassiopea ), moon jellyfish ( Aurelia ) and small box jellyfish ( Tripedalia ). The golden jellyfish used to be a spotted marine species (spotted jellyfish), but the physical population changed after thousands of years in the lake (loss of spots and terminal arms ) .
Even though at first glance they look the same, genetic studies show that the golden jellyfish of Lake Kakaban and Lake Haji Buang are separate. The population of upside-down jellyfish ( Cassiopea ) also looks different, having white beads in Lake Haji Buang, and plain colors in Lake Kakaban.
In the 2000s, Lake Haji Buang was known to have a very high abundance of jellyfish. According to research by Becking et al. (2013), there are 18 species of sponges which are only found in Lake Haji Buang, and have not been found in other lakes. Therefore further research is needed.
Meanwhile, in Lake Kakaban, four unique species were found which are thought to be endemic, namely two species of sea cucumber, one species of tunicate, one species of crab.
Threats in Hajj Buang
Agha reminded us of a number of weak points in the seawater lake ecosystem, namely native biota which for thousands of years has been protected from predators in the sea. Observed to have a small or soft body, no sting, not hiding (exposed) or naive to the presence of predators.
This native biota is mostly invertebrates that are susceptible to pollutants such as ship paint and the like. The underground channel that flows sea water into the lake at every high tide is a source of clean sea water and is critical for the balance of salt levels in the lake's waters.
If they are narrow and oxygen-poor, these channels also act as “fortresses” that protect native biota from invasion by biota from outside the lake. As long as there are no human actions that create a shortcut for foreign biota to enter the lake.
One of the biggest threats currently is the release of any animals and plants that come from outside Lake Haji Buang, whether from the sea, estuaries or other lakes (foreign biota). This can be done intentionally, or unintentionally. Biota can be deliberately introduced by humans (for various purposes), or entered accidentally through unclean equipment/clothing, or foreign objects. This has happened in Palau, with the introduction of foreign biota around the early 2000s, sea anemones have become pests that spread quickly and are difficult to eradicate once the pest population has settled.
Threats in Hajj Buang
Agha reminded us of a number of weak points in the seawater lake ecosystem, namely native biota which for thousands of years has been protected from predators in the sea. Observed to have a small or soft body, no sting, not hiding (exposed) or naive to the presence of predators.
This native biota is mostly invertebrates that are susceptible to pollutants such as ship paint and the like. The underground channel that flows sea water into the lake at every high tide is a source of clean sea water and is critical for the balance of salt levels in the lake's waters.
If they are narrow and oxygen-poor, these channels also act as “fortresses” that protect native biota from invasion by biota from outside the lake. As long as there are no human actions that create a shortcut for foreign biota to enter the lake.
One of the biggest threats currently is the release of any animals and plants that come from outside Lake Haji Buang, whether from the sea, estuaries or other lakes (foreign biota). This can be done intentionally, or unintentionally. Biota can be deliberately introduced by humans (for various purposes), or entered accidentally through unclean equipment/clothing, or foreign objects. This has happened in Palau, with the introduction of foreign biota around the early 2000s, sea anemones have become pests that spread quickly and are difficult to eradicate once the pest population has settled.
Ideal management
According to Agha, ideal seawater lake/jellyfish tourism management needs to pay attention to the vulnerability of native biota and the lake's hydrological structure/process. Fragile native biota needs to be protected from attacks by pests/foreign biota. Therefore, regulations are needed to ensure that visitors (tourists or residents) do not release foreign biota (any animals and plants that come from the sea or other external waters) intentionally or not. A tub filled with fresh water can be provided to clean visitors' feet/shoes before entering the lake because it can carry pest seeds.
The movement of any goods (boats, mines, anchors) from external waters (from the sea or other lakes) also needs to be prevented to prevent transmission of pests from external waters. Native biota also needs to be protected from various tourism facilities that damage the physical and health of the biota, such as motorized boats, duck boats, or the use of chemical substances such as ship paint and wood polish in lake tourism facilities/facilities.
"After a discussion in October 2023, the land owners around the lake, the Payung-Payung Village Government and the Batu Payung Tourism Awareness Group (Pokdarwis) agreed to maintain the Haji Buang Lake ecosystem, as well as develop an environmentally friendly ecotourism plan, taking into account biodiversity. in this lake," said Agha to Indonesia, Monday (12/02/2024).
Another important thing is highlighting the value of the lake as a biologically unique conservation area, and this can be a means of scientific education for tourists. This good management has been implemented by the Republic of Palau since the 1980s in the Palau jellyfish lake ecosystem which is carefully guarded because it is believed to be a valuable state asset.