OVERVIEW OF THE AREA
The reefs around Nikoi are part of the Sunda shelf, a shallow area with a maximum depth of around 20 meters. Strong tidal currents flow through the entire area. Wherever you can find substrate, there will be life in profusion. It can be gardens of soft corals or hard corals which can be found closer to the surface.
Around Nikoi is a variety of underwater habitats:
- fringing reefs
- mangrove flats,
- sand flats,
- rubble patches,
- sea grass beds,
- soft coral gardens,
- granite boulders,
- swim throughs and ledges...
all with their unique floras and faunas.
As the area is quite shallow, big pelagic species do not congregate here meaning there are only a few dolphins, whales or hammerhead sharks. The water is often murky which is mainly due to the waves and the strong currents. As a result, the diving in the area cannot be advertised as world class diving. When having a closer look into the area, you will find that there is as much to see and to explore as anywhere else especially when it comes to soft coral species.
Most of the reefs have been overfished in the area.
Since Nikoi has been opened as a resort, some of the fishermen have shied away and species such as groupers are now to be seen on the reef. The large number of fishing nets and traps that are to be found attest that fishing has been going on in the past.
All in all the coral reefs around Nikoi are healthy, apart from the area in front of the beach and the houses. This could be explained by the seasonal shifting of the sand. In some areas, it is as good as it gets, despise some bleaching events that have occurred in the past.
I have only found two Crowns of Thorn in the entire underwater circumnavigation of Nikoi Island. There are definitely more to be seen but in no epidemic proportion.
There are still a few Sea Cucumbers of commercial value. These are protected due to the fact that they are located just in front of the jetty and no fisherman would dare to pick them up.
The best diving areas around Nikoi can experience strong currents up to 4 knots, which makes it a difficult dive. For experienced divers it is well worth the dive as you can find some fascinating soft coral formations, which are as good as anywhere else.
As we continue exploring, we discover more fish species such as Snake Eels, Cuttle Fish and Wrasses of all kinds in the sea grass. Gobies are also to be seen in the mud flats and even Damsels that I was unable to find in any book.There is an opportunity for new species to develop with the discovery of a meter long Pipefish for example. If these species are not new to science, they are definitely new to the area.
NIKOI UNDERWATER IN MORE DETAILS
Due to current and two monsoon seasons the North east and the Southwest, the visibility greatly varies, and is often less than 5 meters for most part of the year. During the transition period between monsoon, when the wind dies down, the ocean clears and some of the underwater boulders are visible in their entirety, and truly becomes as good as it gets for this region.
The coral reef
A coral reef is many things. It is a complex underwater biome, a vital part of the oceanic world, a testament to the power of Nature, a historical record of our past, a teaching in the fragility of ecological balance, a declaration of biodiversity but above all a healthy coral reef is a living sculpture of great beauty
Nikoi reefs are surprisingly resilient and considering the various pressures from fishing, pollution from tar and oil drifting from the South China Sea, the reefs are relatively healthy. Since the conception of the resort, the most destructive methods of fishing have stopped. Especially dynamite fishing that is still used in other part of the archipelago, despise the fact that it is completely outlawed.
Nikoi island, being located offshore has been spared most of the run offs from Bauxite mining, run off from development and human wastes that have decimated part of the ecosystems on the Bintan coast.
The main direct pressure is still over fishing, and most of the top predators are gone, and valuable species highly thought after for export are sparse.
The east coast of Bintan is a string of fishing villages, relying on fishing to sustain them.
We are in regular dialogues with the fishing community, and proposed the creation of a marine protected area to help replenish the fish stock. (For more information on this issue check the conservation effort around Nikoi Island)
In biological terms, a coral reef is a slow and determined construction by plants and animals that live together in close dependency. Like any ecosystem, a balance is required to ensure the continued livelihood of the coral reef as a whole. The measure of that continued livelihood is the progressive build up of a calcium carbonate (limestone) bed beneath the living layer of corals and the animals and plants that depend on them. This ‘calcification’ process continues for years and years, sometimes millions of years, creating a massive network of skeletons, sometimes even creating new islands. When we talk about the ‘coral reef’, we are referring to this entire system – the highly colorful ‘skin’ or surface of living plants and animals and what lies beneath - a giant mesh of limestone deposits, the remains of the plants and animals that went before. Nikoi Island is entirely fringed by a coral reef.
In addition Nikoi has a high diversity of underwater habitat in a “small “ area: fringing reefs, mangrove flats, sand flats, rubble patch, sea grass bed, soft coral garden, boulders with swim through and ledges, all with their unique plants and animals.
Some habitat like the sand banks become treasure hunts, finding a host of seldom seen species like live seashells, sand dollars and so on.
There are other islands in the region that have good reefs, but Nikoi high diversity within is unique.
Corals as individual animals can be found in all waters from tropical equatorial seas to freezing polar regions, but coral reefs can only be built under very specific conditions. In fact only one per cent of the ocean volume of the planet satisfies the conditions required by corals for their growth, and within that volume of ocean much less has a suitable bottom for coral settlement. We often take our reefs on Nikoi for granted.
The waters ideally suited for corals to survive lie in a belt running around the center of the planet on either side of the equator from 30°N to 30°S. Coral reefs are hot spots of life and growth, color and sculpture, in the otherwise fairly empty tropical seas. About half the world’s coastlines are in the tropics and about a third of these have coral reefs, adding up to about 250,000 km2 of the earth’s surface. This process can be witnessed clearly during the low tide, where Nikoi island double in size.
Corals contain microscopic algae (zooxanthellae) within their cells. These zooxanthellae, like all plants, perform the process of photosynthesis and pass the food that they create to the coral animal.
Corals are very dependent on these plant cells for a healthy life. As a result, corals are in competition with other types of plants found on the reef. There are many types of algae underwater; the largest types being called macro algae, which can grow very fast.
Macro algae crops are kept under control by the fact that plenty of reef fish eat it. Like cows in a field of grass, the fish graze on the macro algae, and so the macro algae does not have the chance to overgrow corals.
If grazing fish are over fished macro algae tends to spread very quickly and grow over the top of corals.
If the water is very turbid, then the particles in the water will stop some of the light at the sea’s surface from reaching the corals that lies beneath. This makes life more difficult for the corals because of their dependency on the zooxanthellae’s photosynthesis. Hence the fact that most hard coral species are found in the 5 meters depth range around Nikoi Island due to the turpid water. Fortunately the strong current partly make up for that with a constant flow of nutrients.
If there is a lot of sedimentation occurring onto the corals themselves, then the corals are choked by the particles that land on them. Sedimentation is also bad for reefs because it can have a negative effect on the amount of successful reproduction that can occur on a reef. When the seabed is covered in fine particles that can be moved around by waves and currents, then coral larvae cannot settle on it. There is tremendous hydraulic power in action from the beach side where the sand completely shift from one season to the next, forming a shallow lagoon in the process for part of the year. At the same time it expose new substrate where a few bold coral colonies take their chances and sometimes succeed if they can grow fast enough.
Although invisible to most, the same process operates underwater, with huge amount of sand shifting, covering and uncovering patches of reef.
Coral reefs grow best where the currents and waves wash in the highest concentration of fresh supplies of plankton. At the same time, the higher the concentration of nutrients, the greater the competition that corals will have against other organisms that feed on the same nutrients, like algae and sponges. In the deeper water where the current is at its peak, mostly sponges and soft coral predominate around Nikoi, but become magical moments of pure raw feeding frenzy, all polyps extended to catch anything passing by.
Corals are animals, and like us, need oxygen. Wave action stirs up seawater, increasing the amount of oxygen it contains. This is another reason why coral reefs grow very well where there is plenty of wave action and the “rough” weather of the monsoons helps the growth of our reefs around I pod rock for example.
Today the Atlantic Ocean has 60 species of coral and 500 of fish as compared to the Pacific which has over 700 species of coral and over 1500 species of fish in Indonesia for example.
In the Indo-west Pacific, because there is a richer species pool in general. As a result, there are predators here that have no equivalent in the western Atlantic. For example, the crown of thorns sea star, giant clams, anemone fishes (clownfish) do not exist in the Caribbean and can all be witnessed easily right from the beaches with a mask and snorkel.
There is a place in the world that has been called ‘the biodiversity triangle’. It is a triangular area of the Indo-west Pacific between the Philippines, Indonesia and Papua New Guinea. The centre of the triangle lies between the Philippines, central Indonesia and eastern Indonesia. For example, there are 175 species of butterfly fish and angelfish in the Indo-west Pacific but only 15 in the Atlantic.
Nikoi lies on the outer edge of that triangle.
There are many factors involved in maintaining a reef or ensuring its continued health but some of the predictions for the earth as a whole imply a decline in the reefs’ abilities to survive - increases in sea water temperature, increases in levels of ultraviolet radiation, changes in the level of atmospheric carbon dioxide which will affect the levels within the sea, human population increases which will place even larger demands on fish populations – and the list goes on. The balance that holds the reef ecosystem together is under threat. At some stage, the scales may tip against the favor of the reefs.
Many reefs have already collapsed close to the “mainland”. (Bintan island) with very little hope in the near future for a fast recovery. Nikoi, on the other hand, not unlike the analogy of Noah’s arch, has still enough of each species to pursue effort towards a total protection of it’s waters.
When you look at a hard coral, you are actually looking at a colony of many animals living together in a tightly knit community where there is sharing of space, food and protection. These connected polyps are also capable of living independently
The living animal is called the polyp. It has a mouth, a stomach reproductive organs, and a three-layered body wall.
Most corals are actually an incredible combination of animals with microscopic plants living inside their cells, zooxanthellae. They are the perfect example of synergy and together, create a miniature ecosystem with the energy producer and energy consumer inside the same organism.
Zooxanthellae can exist both in the coral cells and as free-living planktonic organisms.
Most coral polyps normally only extend their tentacles at night, which is why coral reefs look so much more alive at night than during the daylight. The reason for feeding at night is that this is when the zooplankton rise to the shallows, which is what most coral polyps eat. But around Nikoi some coral species can been seen feeding during the day, because there are no deep water for the zooplankton to hide, and the strong almost constant current brings in enough nutrients.
In length, branches of a branching coral may increase from a few millimeters to about 8 centimeters in a year. Acropora, which is one of the fastest growing corals, has been known to grow up to 15 centimeters in a year. On our jetty there is one that is less than a year old. The front of I pod rock area has seen a amazing recovery from a past bleaching event where the top reef is 100% coverage of hard coral, mainly acropora.
On the left of the main jetty, many new recruits have established colonies that are now thriving,
Balls of coral tissue may remain on an otherwise dead skeleton and later re-establish themselves as coral polyps, secreting a skeleton again. You can watch this on the branching coral in front of the beach, where most of the skeleton is overgrown with algae but the tips are coming back.
We run an experiment by braking of the tips of dead algae smoldered skeleton to create new substrate, and the little polyps took full advantage of that clean surface to recolonise the reef.
Scavenger animals such as crabs, shrimps and lobsters eat the corpses of dead animals on the reef. These are indiscriminating and will eat anything, including the corpses of their own species. Through this process, nearly all organic tissues are transformed into the fecal matter of these scavengers which then settles in cracks and holes, on the bottom etc. Then along come the deposit feeders, which include sea cucumbers, worms and snails. They crawl over both the internal surfaces of the reef and the bottom. They wade through the sediment and consume the organic leftovers and microbes in the fecal matter. They basically treat the waste of the reef, re-suspending reusable particles in the water, which will then be reprocessed by the reef’s filter feeders. A sea cucumber can pass as much as 200 pounds of sand through its body each year and is one of the most effective waste treatment systems in the sea.
WAR ON THE REEF
The most sought after commodity by corals is space. They are in eternal competition with all other sessile (attached to the bottom) reef organisms for it, including each other. When coral colonies grow to be within about two centimeters of each other, they are capable of sensing each other chemically. One of the colonies will throw out its guts, and will begin to digest its rival alive leaving a no man’s land of white skeleton as it slowly overgrows the other coral. On the crowded patch of reef around I pod rock or pass the mangrove and even in some patches around the fringing reef of the beach areas you can see this white area along the edge of one colony where the mucus strands have munched away at the polyps. This competitive behavior is most obvious in the most densely populated zones of the reef – between 3 and 15 meters.
There is a hierarchical ranking in who eats who. The slow growing species tend to be the most aggressive while fast growers will be more subordinate. Some of these subordinate species may produce antibiotics to use in retaliation, or may put out sweeper tentacles to defend themselves. These sweeper tentacles help to prevent being overgrown by the next-door neighbor and are also useful in preventing corals growing above, where they would block out the essential light. The sweeper tentacles are thrown out at night-time, so under the cover of darkness the battle for space takes place on the reef.
Some species found on Nikoi reefs
Fungia, also known as the mushroom corals. They produce offspring by budding off from a fixed, stalked stage in its life cycle. Fungia can travel on a tidal current. When they feel the need to move they expand their tentacles like the sail of a ship to catch the current. The coral can right itself if it is turned upside down. It uses its tentacles, expanding and contracting them repeatedly until one side of its body is more full with seawater. When the coral, probably after many strained attempts, finally rights itself, it opens its mouth and vigorously spouts seawater. This poses great stress on the coral and the contortions required to right itself cost it a great deal of energy. Some of them have a tiny worm living in a cavity on their underside. The worm can help to pull the coral across the sand and a jerk of the worm can be the final push required for the coral to right itself.
Acropora corals overwhelmingly dominate most Indo-Pacific coral communities where there is good light availability and water circulation. Under these conditions Acropora displaces other groups of corals.
Tubastrea is an azooxanthellate scleractinian and clearly demonstrates in its simple structure how azooxanthellate corals do not form complex skeletal frameworks, unlike their zooxanthellate relatives.
Anemones are colorful, jelly-like structures with waving tentacles and are of particular appeal on Indo-Pacific reefs because of the symbiotic association with the clownfishes that live inside. These fishes have a special protective coating, enabling them to withstand living among an entire battalion of stinging cells without being hurt.
The digestive surface of the cavity making it possible for an anemone to digest a relatively large animal in a relatively short space of time, even a fish or a crab.
Tube dwelling anemones are solitary animals, each encased in a mucous tube impregnated with detritus and buried vertically into a soft substratum.
The octocorals are some of the most brightly colored and delicate looking creatures on the reef. They sometimes resemble flowery trees. Among the octocorals are the soft corals, the sea fans, sea whips and sea pens. Most are filter feeders and tend to grow in areas with a current flow. Some boulder walls are entirely covered with them, facing the current, and are truly explosions of bright colors. Seldom seen by novice divers, because of the harsh condition to witness them, they are true gems in the underwater treasure chest of Nikoi Island.
Sea fans and sea whips are both gorgonians. Sea fans grow in one plane, sea whips in long projections. Sea whips are superficially a little like black corals but their axis is always smooth, never thorny. Even the same species may grow as a radial whiplike form in a spot with random turbulence and only a meter away, as a flattened fanlike form, oriented perpendicular to a prevailing water current.
A sponge must pump about a ton of water through its system to extract enough food to gain an ounce of body weight. Sponges draw in water through specialized cells in their canals and chambers.
Sponges provide homes for a huge variety of animals including shrimp, crabs, barnacles, worms, brittlestars, sea cucumbers and other sponges. Crucial microbes also live within the sponge and even within the sponge’s cells
Tunicates look like simple structures but this belies their complexity. They belong to the chordate group of animals, which includes the vertebrates. Tunicates do not have a backbone but they do have a heart. They are vase shaped animals attached at one end to the substratum. They can be solitary or colonial.
The echinoderms make up some of the most characterful invertebrates of the coral reef – the lolloping sea cucumbers, spangling sea stars and jewel like sea urchins. Echinoderm means 'spiny skinned' but not all members of the phylum have spines. As a rule, the echinoderms have five symmetrical parts to their bodies (but in the sea urchins and sea cucumbers the radial symmetry can only be seen on the inside of the animals).
Crinoids can grow new arms or even a central body disc if the original is lost. They eat any small animals and plants that drift by.
Sea stars can evert their stomach through their mouth to envelop their prey. They pour digestive enzymes over the prey, which is partially digested externally. Food varies from algae, microorganisms, sponges, corals, worms, crustaceans, mollusks and other sea stars.
Their skin is toxic so they have few predators.
They have amazing powers of regeneration. Some species are able to regenerate their whole body from a sizeable fragment. Some species reproduce asexually by tearing across the disc, each half regenerating to become complete again. Others reproduce by breaking off an arm which again regenerates to a whole. Sexes are separate. They release eggs and sperm for fertilization in the open water to form pelagic larvae.
The crown of thorns eats at night. It ejects its entire stomach, bringing the coral tissues into direct contact with the digestive enzymes so digestion begins before the tissue has actually been brought to the seastar’s mouth. The seastar does not damage the skeleton, only the live polyp tissues. This process takes 4-6 hours. The area of feeding is defined by the size of the stomach and therefore the size of the sea star. Once a coral is digested, the sea star moves on to the next branch or colony. It can eat about 2 square foot / day (watching fishes) but it has the ability to move relatively rapidly across the reef.
They are called brittle stars because their arms break off easily but they have great powers of regeneration and losing an arm is no big deal to them. Some feed on detritus and microorganisms but many are active predators preying on small worms and crustaceans. Some species burrow into the sandy bottom around coral patches, leaving only the tips of their tentacles sticking out to feed on detritus or on suspended particles, sending small columns of water down their bodies with their waving movements so that they can breathe.
Sea urchins play an important role on the reef as algal grazers. They are part of the herbivorous community, along with many fishes, that keep algal populations under control. A change in the sea urchin population can change the composition of the reef. There have been some fairly drastic changes in urchin populations in the past, both increases and decreases.
Sea cucumbers are the vacuum cleaners of the reef, playing a very important role as the organisms that put back into circulation the precious nutrients that would otherwise be lost to the sandy layers of the seafloor. The sea cucumber actually forages through all the trash and returns to the ecosystem what can be used again.
They are in huge demand in Asia. They are easy to harvest, they barely move. They are easy to process, they only need to be boiled then dried. But as a result, there are now many reefs with barely a single specimen left on the reef. Luckily we still have a few.
Barnacles are very prominent on intertidal boulders (and on ship’s hulls!) Nearly all barnacles have a number of calcareous plates in their carapace to enclose and protect the body. They have cement glands near their basal plates which secrete a cement for attachment to the substrate. This compound aroused a great deal of interest from dentists for its underwater sticking capabilities. Almost every boulder is encrusted with them close to the low tide mark.
Cleaner shrimps, together with the cleaner fishes, keep the levels of most pathogens and parasites quite low in wild fish populations. Many cleaner shrimp live on or near anemones and attract fish with of their bright colors and gestures. The largest ones live on the anemone's tentacles or near its mouth. The smaller ones wait on the sand around it. As a fish approaches the larger shrimps attract its attention by dancing and waving their antennae. When the fish has been successfully enticed, all the shrimp join in the cleaning operation. If you are patient you can get a free manicure.
Giant clams live in shallow waters on or near the upper reef surfaces in the sandy lee sides of reefs where their symbiotic partners, zooxanthellae, can receive the sunlight they need for photosynthesis. This intense sunlight would ordinarily be destructive to the clam itself, but over evolutionary time it has developed a protective pigmentation – brilliant shades of blue, green, brown and yellow in their mantle. The zooxanthellae return the clam’s hospitality by releasing nourishment into the clam’s bloodstream. Without the zooxanthellae, there would not be enough plankton in the nutrient poor tropical water to allow the giant clam to grow to the sizes that they do. But when their photosynthetic days are over, the clams eat the algae, but newly invading zooxanthellae are immune to consumption by the animal. In this sense, the clam can be regarded as a closed system on the reef. Priced as a delicacy, they have nearly disappeared from most reefs, but you can find them easily on Nikoi, straight off the beaches on the reef crest.
There are about 35,000 species of gastropod. They move on a large single 'foot' which looks like it's coming from the stomach. The snails have a tongue covered with file-like teeth which they use to rasp away vegetable or animal matter. Some use it to drill oyster and clam shells. A nudibranch is a snail that loses its shell shortly after the larval stage. It is so-named because of the naked gills on its back that it breathes through.
In the deeper waters on rubble patches and sand banks, you can find helmet conch shell (cm and 2 to 3 kg), live olive shells, scallops,
Ribbon worms have an amazing ability to contort their muscular bodies. Some species have flat bodies, other are cylindrical. Some species are capable of injecting venom to capture prey. They can be over 50cm long.
Polychaete worms are very various looking group of worms which includes the 'bristle' worms (like centipedes), fan worms, christmas tree worms and spaghetti worms. Some burrow in the sediments, others live in the interstices of semi-consolidated sediments or among rubble
Cuttlefishes are masters of camouflage, changing colors but also textures at will; they also have one of the largest brain-to-body size ratios of all invertebrates, making them some of the most intelligent invertebrates around. Fierce predator they actually attacked stingrays and ate all the other small fish caught in a fish trap on the reef left of the jetty to remain the last survivors in the trap after one week.
Cuttlefish's eyes are speculated to be fully developed before birth and start observing their surroundings while still in the egg, and may prefer to hunt the prey they saw before hatching
They come to mate on our reef, and are seeing in pairs especially in the month of April and may when food is plentiful with many new hatchlings around cuing on the slight rise in water temperature during the transition between monsoons.
Once a relationship is established and the threat factor out of the way, amazing encounters are possible including touch and will imitate gestures made with one’s fingers for example.
Algae are essential on the reef as the primary producer, using photosynthesis to fix light energy. Put very simply, if there were no algae, there would be no reefs. But as stated so many times already, macroscopic algae are prolific growers in most tropical waters and will compete heavily with corals for space and light. If they become too dominant, they can threaten to overgrow existing colonies and prevent any new colonies from forming by preventing coral larvae from settling. Conversely, algae spores cannot settle and grow on living corals either because the merciless polyps will eat them.
Some butterfly fishes and angelfishes live in committed partnerships. Some butterfly fishes pair for at least three years. Sometimes pairings may be weaker, depending on the environmental conditions and sometimes pairings may occur between fish of different species, perhaps because of sparsely spread populations. Beggars can’t be choosers.
The blind goby which lives in burrows with a shrimp – having mated for life it need not leave its burrow to search blindly for a mate.
There is a certain jack, known commonly as the pilotfish since it tends to swim just in front of sharks, rays, turtles and other large fish. Juvenile golden trevallies, also display this type of ‘piloting’ behavior with sharks and other large fishes such as groupers
A great number of reef fish feed on the filamentous and macroalgae growing on the reef including parrotfishes, surgeonfishes and rabbitfishes. They will scrape the thin filamentous algal film that grows on all bare surfaces. They can be thought of as the roving cattle herd, sweeping the reef clean of its ‘grass’. Other smaller grazers such as blennies and damselfishes are more like cattle kept in pasture, generally territorial.
All goatfishes are carnivorous, feeding on worms, crustaceans, brittle stars, small mollusks and the heart urchins that live in the sediment. (Some also feed on small fishes). Goatfishes possess special sensory devices called barbels hanging down from their chins. These organs are chemically sensitive and are used to probe into the bottom.
Squirrelfishes sleep during the day in holes and caves, emerging at night to feed on shrimps and crabs. Squirrelfish have huge eyes which gives them excellent night vision. They are mainly bottom feeders.
Snappers feed mainly at night, moving away from the reef itself to do so. Ironically some species feel the need to protect themselves from predation during the day, hence forming schools in daylight hours. They eat mainly fish but will also consume crabs, shrimps and many other crustaceans, also cephalopods. The yellowtail snapper feeds around the clock, working mostly at night but always on the lookout during the day for an opportunity to munch. It is very undiscriminating in its diet, eating anything from other fishes to eggs and larvae, even waste matter.
Scorpionfishes also use camouflage to catch dinner. They feed mostly on crustaceans but will even eat the juveniles of their own species. Most moray eels have long canine teeth for their fish diet, supplemented occasionally with an octopus or crustacean
As with corals, the reproductive cycles of many fish are dictated by the phases of the moon. The link to the lunar cycle is a very practical one since the oceanic tides and currents are also controlled by the movements of the moon around the earth. Just before full moon, the evening tides sweep outwards from the shore. This is the ideal moment for gamete release, since they will be carried away from the reef which is, after all, one of the most efficient plankton-devouring systems. Eggs and sperm are helpless parts of this plankton themselves until they develop into motile fish. Ensuring their carriage away from the reef protects them, but then the juvenile fish must somehow make it to another reef where they can settle.
All anemonefishes are hermaphrodites. There is a rigid hierarchy in an anemone colony of fishes. The female is the largest and most socially dominant fish in the group. When a female dies, the largest male will grow change sex, and the next largest will sexually mature as fast as possible to become the breeding male. The parent fish will tolerate a few juveniles but when grown sufficiently, they must leave and make a frequently perilous journey to find another unoccupied anemone of their own.
In learning to dive, we are learning to move like fish. One of the most important aspects of this is figuring out how to be weightless, that is how to avoid sinking like a stone or floating to the surface like a buoy. We achieve this by wearing a jacket filled with air which can be inflated or deflated depending on whether we need to be more or less buoyant. Fish have an in-built buoyancy compensator, called a swim bladder (or gas bladder, or air bladder). It is situated near the center of the fish and like our jackets, can expand and contract on demand. There are two types of gas bladder – open and closed. Most reef fishes have closed swim bladders, meaning that they can be inflated with air extracted from the surrounding water. To deflate, the excess air is passed from the swim bladder to the bloodstream. Fish with open bladders have to rise to the water’s surface to take in air directly to the bladder. These fish, when rising to the surface, release the excess air from their bladder through their throats. If it is not released, the bladder will rupture.
Although rare nowadays, we spotted sail fish, a few barracudas, Spanish mackerel, tunas, giant trevally, but unfortunately most of those are rare occurrence over the span of 3 years of constant observations giving us a clue of what is happening further out. Most of these species are pelagic, not resident, and totally out of our “control”.
Indo pacific humpback dolphins, visit our area, but they are shy in their behaviors, they are difficult to spot, unless the sea is flat calm. They are also called pink dolphins for the pinkish coloration of their skins, sometimes being totally white.
Seagrass beds and mangroves function as nurseries for a variety of fishes and invertebrates that spend their adult life on coral reefs. They are ideally suited for this purpose because they are away from the heavy predative population of the reef, there is protection for small organisms because of the structural complexity of masses of leaves and roots and there is a rich food supply based on plant detritus and associated microorganisms and small invertebrates.
Seagrass beds are important zones for the protection and production of many animals. Green algae is a very important part of this ecosystem. Only a few animals eat the seagrass itself - dugongs, turtles, some mollusks and urchins - but many animals graze on the green algae and diatom films that grow on the seagrass blades. One of the most exciting things about seagrass beds is that this is where you are most likely to find a seahorse underwater. Large schools of benthic-feeding grunts and snappers migrate from the coral reefs to the seagrass beds at dusk, returning at dawn. The fishermen are very well aware of this.
The patches around Nikoi are not huge but this is where you can scout for unusual species and give the green turtle that nest on the island a good snack before going through the hard labor of digging and laying eggs. Such a hard labor that you can see them shedding tears. (Actually it is really a way to keep the eyes moist and keep the abrasive sand somehow under control
No coral reef in the world has ever been or will ever be in a constant state of growth. No sooner has the reef established itself than it must begin to defend itself against a constant battalion of destructive forces. The processes of construction must stay one step ahead in order for the reef to survive.
It is unwise to judge the state of a coral reef on one snapshot in time, although there are occasions when a state of doom becomes obvious. The balance between the ‘natural’ threats to the reef and the in-built resilience of the organisms upon it swings around. In general, without too much disturbance, the reef will manage to keep its head up by repairing what is broken down, or re-planting any ravaged patches. These regenerative powers come under great stress when the threats to the reef’s survival come thick and fast – one stress at a time is manageable, several at once or in rapid succession just might tip the balance. Nikoi reefs are not in pristine states, but are not doomed either. The pressures are kept in check, and it’s biodiversity from the varied habitats and the constant changes of temperatures, currents, wave action from storm and monsoonal wind (with the added blessing of no cyclones or tsunamis) gives it the extra edge to survive.
At the boat house, where we keep our snorkeling and dive gear we also have a few books on fish and coral and reef species for identification, and a I pad with a collection of photographs and movies taken around Nikoi and reefs nearby that records the ecosystem and species around the area.
Conservation issues and efforts
- photo galleries
- Dive sites
- Blog tales from the islands
- Turtle program
- Critter stories
- OIL MADNESS
- BLEACHING PICTURES 2016