The Heart of Indo Pacific

The sea bottoms of peninsular Malaysia and Malaysian Borneo are among the most spectacular and species-rich in the world, thanks to the unique geographic location of the country. Peninsular Malaysia is washed to the west by the Andaman Sea (which in turn borders the Indian Ocean) and by the more southerly Strait of Malacca (which separates it from the large Indonesian island of Sumatra), and to the east by the southern reaches of the South China Sea.

The insular States of Sabah and Sarawak - which together with Indonesian Kalimantan and the small sultanate of Brunei make up the huge island of Borneo - face the Sulawesi Sea to the east (separating Borneo from Indonesian Sulawesi itself), the Sulu Sea to the north (separating Borneo from the Philippine archipelago) and, finally, the South China Sea (which separates the island of Borneo from peninsular Malaysia to the west). These seas and sea basins cover an immense area just above the Equator and are characterised by an almost infinite variety of littoral environments, often uninhabited and to date largely unexploited. As yet the area is largely unaffected by the impacts of industrial and agricultural pollution. With careful management this should hopefully remain the case for a long time to come.

Most coastal fishing is still carried out by local fishermen using traditional methods, even though the deplorable habit of using home-made explosives or cyanide has already caused noticeable damage to coral reefs in several locations. There are worrying signs that the regular forays of fleets of open-sea fishing boats - especially those from China, Vietnam and the Philippines, which fish in complete disregard of environmental laws, at times bordering on piracy - are causing severe impoverishment of pelagic fauna.

Serious and perhaps irreparable damage has occurred over the last decade to many local populations of sea creatures: sea moths and seahorses (millions are used by Chinese chemists); sea snakes (hundreds of thousands are killed yearly in the Philippines for the tanning industry); sea cucumbers (entire populations have been exterminated to supply the trepang industry, as sea cucumbers are considered a delicacy of Asian cooking); sharks of all genera and species (these also, or rather their fins, are unfortunately considered a delicacy by devotees of Chinese cuisine); and hawksbill, leatherback and green turtles (protected in Malaysia but hunted throughout Indonesia for their flesh, eggs and shells).

Despite these impacts, the sea and seabeds around Malaysia and Indonesia, located in the centre of the Indo-Pacific basin (the area stretching for almost thirty thousand kilometres from Madagascar in the west to the easternmost islands of the Pacific), still represent one of the richest marine habitats in the world, with an estimated minimum of more than 3,000 different species of fish. This region, the heart of the genetic wealth of the entire Indo Pacific, has been subjected to the same tropical climate for more than 100 million years, with ideal conditions of light and temperature, which have nurtured the development of a complex differentiation of species.

Continental drift, the resulting volcanic activity, and erosion have contributed to the creation of a great variety of ecosystems within which completely different ecological niches co-exist in a fascinating evolutive environmental laboratory: unfathomed abyssal depths, rocky basaltic cliffs, shallow sandy or silty beds, expanses of sea grass, impenetrable mangrove forests and of course spectacular coral reefs. These varied ecosystems represent profoundly different environments whose specific characteristics have led to the evolution of many highly specialised species.

The most important geographic region, from a biological point of view, is perhaps the South China Sea basin, about 3,400,000 square kilometres in area, extending from the Equator almost to the Tropic of Cancer and from peninsular Malaysia to the Philippines. The sea depths, taking into account the adjacent areas and satellite basins, vary from just 100 metres (along the continental shelf of the Sunda Strait) to more than 5,000 metres (the abyssal depths of the northernmost part).

This sea is greatly affected by the monsoon weather patterns (north-east monsoons from December to February, and the south-west monsoons from June to August) which modify the surface currents and temperatures in shallow water with predictable regularity.

These temperatures generally vary between a minimum of 26°C and a maximum of 30°C. In a tropical regime with more or less constant temperatures such as these, the upward movement of large water masses (which helps to mix the nutrients found at the sea bottom with the water at the top in temperate and cold seas) is not possible. In the tropics the energy supply is ensured by the huge quantities of nutrients flowing into the sea from swollen rivers during the monsoons (this is why during the wet season it is common to find turbid water with limited visibility at shallow and medium depths).

Surface currents, high temperatures, and long periods of sunlight also guarantee a high energy supply. These are factors which give rise to the continuum of interconnected ecosystems which exists along the gradual transition from land to oceanic depths. In shallow and medium depths, where there is more sunlight and temperatures are higher, the peak of productivity and biodiversity is reached. Sand beaches are used as nesting sites by the green turtle (Chelonia mydas), the giant leatherback turtle (Dermochelys coriacea), and the hawksbill turtle (Eretmochelys imbricata), and as mating sites by sea kraits (Laticaudacolubrina).

Mammals, birds, reptiles and crustaceans living in these areas (and their eggs and young) represent an important source of food. Expanses of sea grass offer shelter to many cephalopods (such as squid and octopus) and provide nutrition for green turtles and dugongs, while hawksbills prefer feeding on sponges and soft corals along the reef. Littoral mangrove forests provide food and protection to an enormous number of young creatures gathered together in nurseries: especially fish, but also many different types of reptiles and birds. Other highly specialised species prefer the habitats offered by silty seabeds, which at first sight appear to be deserted and inhospitable.

Many creatures are carried by currents onto the barrier and fringing reefs, where they reach adulthood, joining the reefs’ inhabitants and contributing to the splendour of what has been described as one of the richest ecosystems in the world. Other species, especially large predators such as sharks and tuna, will choose the infinite pathways of the open ocean in search of prey or a companion. However, the conclusion remains the same; however diverse, these ecosystems are perhaps more inexorably interconnected than anywhere else on Earth and in each of these habitats - even in the most seemingly inhospitable - there will always be motives of interest for the biologist, naturalist and underwater photographer.