The main aim of the study is to make a qualitative and quantitative appraisal of physical damages of coral and to assess total debris and solid materials dumped around St. Martin’s Island. To do so, a few techniques have been applied, namely direct observations by scuba diving, collections of bottom samples by grab samplers and measurements of sediment accumulation using ocean sediment traps. Scuba Diving Scuba (self-contained underwater breathing apparatus) diving is a mode of underwater diving in which a diver uses a self-contained underwater breathing instruments (scuba) to breath. During each dive, the divers usually carry the source of breathing gas as compressed air which allowing them greater freedom of movement under the water. A scuba diver primarily moves underwater by using fins attached to the feet.
Scuba equipment primarily includes diving suit, and breathing equipment. Depending on the water temperature, depth and duration of the planned dive, the diver either use a wetsuit, drysuit or hot water suit. A number of factors dictate the type of breathing apparatus used by the diver. Typical considerations include the length of the dive, a scuba set is any breathing set that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. Although strictly speaking the scuba set is only the diving equipment which includes breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing called diving equipment with the pressure gauge.
In this research, a total of four dives were made between 9 and 12 April 2015, and each lasting up to 45 minutes to collected underwater information. Each dive was led by the first author and were accompanied by one underwater guide and one underwater photographer (with still and video camera). A research student was in standby and also made a few short sessions.
Grab Sampling Marine sediments are made up of varying mixtures of geological and biological material that have accumulated over long time periods. Collection of sediment samples from ocean floor is a difficult task. Ocean scientists usually use gab sampler to collect chunks of ocean sediments. A grab sampler is lowered vertically from a stationary vessel, commonly cover an area of 0.05 m 2 to 0.2 m 2 usually penetrating to a maximum depth of 15 cm into the sea floor. There are several types of grab samplers of which Van Veen grab is being commonly used. A Van Veen grab has long arms attached to each bucket, which are held together in an open position during lowering. When the grab reaches the bottom, the lowering wire relaxes, thus activating the release hook which enables the buckets to close together before the grab leaves the sea floor on hauling. The arms, besides giving good leverage during closure, also avoid the grab from being pulled off the bottom in case the ship turns as it is sampling. However, this grab is not recommended for use on coarser substrata because large gravel particles tend to become caught between the jaws resulting in loss of the sample upon retrieval of the grab. In this study, a total of two grab samples were collected using the Van Veen Grab (modified locally) sampler. After reception of the grab on deck, physical features, such as smell, color, presence/absence and transparency of supernatant water, visual sediment description (type, surface disturbed/undisturbed, presence of organic/inorganic debris, etc.) were recorded. Samplers were then properly packed to carry to the laboratory for further study.
Physical Damages to the Corals One of the major challenges for the growth and survival of coral community is the physical damage of coral species by direct human activities. During the scuba diving sessions, it was noticed that the physical damages of coral species is now in an alarming stage. Nearly in all locations it was found that out of 10 specimens at least two were broken-up, damaged or uprooted from its growth position by human interventions. The scale of damages is either a single individual was broken-up by direct hits or a small fraction of it has been eroded-up due to some massive destruction. It was attempted to examine the nature of physical damage and their links with human activities. It is clear that the process of destruction is steady and continuous. People involved with such destruction are both knowing-fully as well as due to lack of awareness. We have identified the evidence of at least three major causes of massive coral destruction physically. One of the major causes of physical damage of corals is the anchoring from local boats. Two other causes are fishing nets and coral hunting for tourists. In all cases the local peoples (boatmen, fishermen and coral collectors) are involved and responsible.