Human Activities Impacts on the Coastal Environment

The anthropogenic (human-influenced) alteration of our coastal environments may take many forms including, but not limited to: tourism, antifouling paints, oil spills, destructive fishing, and the introduction of hard structures such as jetties, groins, and sea walls. These alterations change coastal dynamics and have far-reaching effects on coastal ecosystems, hydrodynamic and tidal regimes, and sediment transport rates.

With the sun, sea and white sands, tourism has become a major problem to coral reefs by the increase in boating activities and divers. An estimated 14 million people engage in SCUBA diving every year; with many divers seeking out coral reef ecosystems. Divers affect coral reef ecosystems by breaking coral and reef dwelling organisms with fins and equipment and by handling and touching the coral. They also stir up sediment with fins increasing surrounding water turbidity. Chadwick-Furman (2002) estimated that on a typical SCUBA dive of 60 min at 4–8 m depth, each recreational diver broke 1.7 ± 4.9 corals and raised 9.4 ± 11.9 sediment clouds onto the reef (n = 251 divers). This impact can be reduced by pre-dive educational briefings which explain the sensitive nature of coral reef ecosystems.

Boats use anchors and antifouling paints which directly affect coral reef ecosystems. Anchors and connected chains can break and fragment corals. This directly destroys homes of organisms but also indirectly increases the turbidity of the surrounding water; reducing the sunlight available to the zooxanthellae, which could lead to coral bleaching. Given the slow growth rate for most coral species, it can take many years, for coral colonies to recover . However, anchor damage can be prevented by the installation of mooring buoys and simple changes in boating habits and education.

Antifouling paints are used to prevent organisms from attaching to the bottom of boats. These include TBT; “the most toxic substance ever deliberately introduced to the marine environment by mankind”). Marshall et al., 2002 documented a TBT problem in the Great Barrier Reef caused by the grounding of a 21,000-ton container ship. They found that the “highly toxic substance” killed or injured most of the organisms in the surrounding area. Luckily, TBT is now a banned substance for vessels less than 83 feet in length, but other antifouling paints are still being used. These are copper based and have been documented to inhibit some coral larvae from developing into juvenile coral polyps.

Oil spills resulting from deliberate or accidental release of oils from ships or following a collision or grounding of vessels are one of the largest threats to reefs (GBRMPA, 2005.).

There are many ways in which the oil can come in contact with the reef after a spill. Floating oil may be deposited onto a reef as it becomes exposed at low tide, droplets of oil may be dispersed in the water column, or droplets adsorbed onto suspended solids in the water column may settle onto the reef (Teal and Howarth, 1984.).

When the oil comes in contact with the coral it can cause breakdown of the tissue and many other problems. Rinkevich and Loya (1979) for example, found that oil products could induce premature release of gonadal material and larvae, and reduce larval survival. Loya (1975) described that recolonisation of polluted reefs is slow as it disrupts reproduction and recruitment. These are just a few of the many effects it has on them.

The main factors influencing impact and recovery of coral reefs are as follows (IPIECA, 2006):

• The amount and type of oil spilled
• The degree of weathering of the oil prior to contact with corals
• The frequency of the contamination
• The presence of other factors, such as high sedimentation
• Physical factors such as storms, rainfall, currents and low tide
• The clean up operation
• The type of coral
• Seasonal factors such as mass spawning

Destructive fishing efforts are present on coasts in many developing countries. This is done via the use of dynamite to catch fish; where the dead fish float to the surface and the reefs are destroyed in the process. Collapse of whole reef slope sections is frequently observed due to dynamite fishing techniques.

Where explosions occur there is usually a reduction in fish abundance; possibly due to reduction in areas to live without protection from predation. Herbivore loss can be critical for reef health. The absence of herbivores increases algal abundance and leads to a reduction of coral settlement.

Most commonly, sodium cyanide is dissolved in seawater in plastic squirt bottles. Divers using hookah dive equipment squirt the milky solution at the target fish, which often then retreat into crevices in the reef or within coral thickets.

These corals may be subsequently broken apart by the diver to capture the fish. Cyanide tablets may also be secured to sticks and held close to a fish, or cyanide is mixed with bait and thrown overboard or placed into fish traps. There are also reports that fishermen occasionally pump the cyanide into the water from surface boats, mainly to target grouper spawning aggregations.

The stunned fish are then captured with handnets or attached to lines and hauled to surface-support boats, where they may directly enter the trade or be held in floating cages until export.