An historical overview of impacts from land-based pollution on community based natural resource management (CBNRM) as it applies to marine fisheries & coral reefs in the tropics.

Industrial effluents appear to be primarily oxygen-consuming organic materials as measured by Biological Oxygen Demand (BOD) from agro-industries in Western Indian Ocean countries (Table 5).

Table 5. Industrial pollutants, western Indian Ocean.

Top-Downers, Blaming the Fishermen versus Bottom- Uppers Blaming Pollution for Demise of Coral Reefs

There are major debates as to which is more important to the demise of coral reefs, land-based pollution (“Bottom-Uppers”) or over-fishing ("Top-Downers"). Many coral reef biologists believe overfishing of herbivores is of greater importance than nutrients in driving algae overgrowth of reefs, though most publications supporting this “top-down” hypothesis lack nutrient water quality data. “Top-Downers” suggest the solution is to stop fishing. If this were the limiting factor in reefs, herbivorous fish populations would crash as fisheries intensified, causing reef algae to proliferate, so preventing fishing should cause corals and fish to recover. But in fact, these patterns were not seen in the Caribbean: overfishing long preceded coastal tourism over-development, while sewage effluents and algae proliferation increased simultaneously whenever new tourism areas were developed, and fish populations changed from being carnivore dominated (the preferred choice of fishermen) to becoming almost entirely herbivore dominated as algae became the only abundant food source. It has been found that a reduction in herbivory from overfishing may enhance the likelihood of inorganic/organic pollution causing a coral-algal phase shift, but a reduction in herbivory in the absence of eutrophication can also lead to the proliferation of algae [14].

While the debate continues, if land-based pollution and overfishing are not addressed, the creation of marine parks will not save the coral reefs nor the fisheries, and any hope of expanding the concept of CBNRM to coastal fisheries will be lost.

Coral Bleaching

Until massive coral bleaching and die-off due to recent ocean warming events starting in the 1980s, a major cause of coral die-off globally had been and continues to be nutrient pollution. Coral bleaching is the whitening of corals that occurs when the zooxanthellae are lost from coral tissues or the amount of photosynthetic pigment in the zooxanthellae is sharply decreased. Because corals can only survive in a limited range of conditions, a slight temperature increase over a prolonged period can result in bleaching. Stresses from pollution (e.g. nutrients, sedimentation), high levels of light, infections, excess shade and fluctuations in salinity levels are also associated with incidents of coral bleaching. If the sea surface temperature (SST) increased 1°C for a month or longer above the long-term average for the warmest months/season, the period was termed “a hot spot” and usually resulted in mass bleaching of coral reefs. If these conditions last only one month and it then cools down, almost all corals will gradually recover. If excessively hot surface water conditions persist for two to three months or if surface water temperatures reach 2°C or 3°C above average for one month, coral mortality becomes significant. In the Caribbean, once seawater temperatures reach about 30°C for a few weeks, corals can begin experiencing “bleaching”, the degree of bleaching appearing to increase with the length of period of elevated surface water temperatures. In 1982-1983, 70-95% of the corals in the Eastern Pacific off of Costa Rica, Panama, Colombia, and the Galápagos Islands died because of bleaching caused by the warm waters brought by El Niño (ENSO - El Niño–Southern Oscillation, irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean). In the late 1980s and early 1990s, bleaching became a regular and pervasive problem in the Caribbean and began to appear in the Pacific and Indian Oceans -- often related to El Niño events. During the El Niño of 1997- 1998, bleaching began in the eastern Pacific but then expanded to an unprecedented, alarmingly broad region across the Indian Ocean from Kenya to Indonesia and in the Pacific Ocean from Australia to Polynesia [2].

The consequences of coral die-off, be it from land-based pollution or ocean warming are similar; dead reefs, increased beach erosion, decreased fishery habitat, public health issues, declining tourism and ultimate loss of key economic sectors. One might challenge the importance of land-based pollution when the consequences of ocean warming events on coral die-off were as much as 10 times that from other causes in the Seychelles and much of the Western Indian Ocean (e.g. sediment from land or dredging, algae overgrowth, tourist and anchor damage, storm waves, or coral-eating crown of thorns starfish), resulting in 75- 99% loss of live coral. However, corals have begun recovering from this ocean warming event. Recovery can be enhanced by diminishing stresses like land-based pollution. Ocean warming must be dealt with through long-term international negotiations, but land-based pollution can be dealt with immediately at regional and local levels [14] (Figure 5).

Figure 5. Coral bleaching, West Coast, Barbados, 1988/1989; zooxanthellae giving, coral color, have been extruded, but coral is still alive [2].

The following summarizes the author’s experiences in the Caribbean and how they relate to the Indian Ocean along the eastern side of the African continent in the development of coastal tourism. General conclusions drawn are [2]

• Land-based pollution is a primary cause of coral reef degradation. At the September 1988 Regional Seas Conference sponsored by UNEP in Mexico City, land-based pollution was considered the number one environmental problem affecting the Caribbean Basin;

• This is primarily from nutrient enrichment of near shore marine waters associated with improperly or untreated domestic sewage and gray water originating from major urban areas and from tourism developments;

• The world's tropical waters are nutrient poor and ecologically thrown out of balance by this enrichment, resulting in coral reef ecosystems collapsing as a result of being smothered by epiphytic algae (benthic macro-algae), which prevents zooxanthellae (a symbiotic dinoflagellate living within the coral polyp from photosynthesizing (gives coral color & provides colonial corals with 98% of their total food requirements), the rest of its food coming from the polyps filtering micro-organisms out of the water – thus cutting off the coral’s food supply and starving it to death;

• Believed to be secondary in importance in causing coastal degradation are pollutants associated with agricultural runoff including sediment, pesticides and fertilizers, often from ill-conceived donor policies (e.g. subsidized bananas in the Caribbean on many of the “banana islands” such as Grenada, St. Lucia, St. Vincent and Dominica) (Table 6);

Source: Survey by DeGeorges [21], while USAID's Regional Environmental Management Specialist for the Caribbean, (REMS/C), in DeGeorges & Reilly [2].

• The loss of coral reef from sewage/nutrient pollution sets off a cycle of beach erosion as the source of sand, (corals breaking down gradually over time provide a major source of sand along with coralline algae) and because of lost protection from wave and storm action by the collapsing reef. This, along with declining artisanal fisheries from habitat loss and eye, ear and skin infections of bathers/swimmers, has the net result of diminishing tourism attractions;

• Western waste treatment technologies solve neither ecological (e.g. up to secondary treatment removes primarily biological oxygen demand/BOD but few nutrients) nor public health needs (e.g. secondary treatment as commonly used with relatively short outfalls.

• High tech tertiary treatment that removes significant amounts of nutrients suffers along with secondary treatment from high operation and maintenance levels (cost of maintenance, availability of spare parts, qualified technicians, who are even hard to find in the developed world) and as a result is rarely operated up to design capacity;

• One viral particle can make a person sick. Normally, sewer water dumped at sea should not come in contact with a person for at least two days; this period of time allowing for viral dieoff from ultraviolet radiation;

• Land-based discharge of sewage requires secondary treatment and viral aerosols are still an issue (e.g. spray irrigation of golf courses), which is maintained with difficulty in developing countries. On islands, land (e.g. overland flow, crops) is a major constraint as land availability can be an issue, while during the rainy season major holding ponds are needed;

• Solutions such as long outfalls with preliminary treatment, possibly land-based treatment and deep (not shallow) well injection, exist but are ignored by governments and developers, mostly out of ignorance, in favor of simple septic systems and secondary treatment package plants with short outfalls. A report in 2002 by Sealy of the Caribbean Water and Wastewater Association (CWWA) confirms this to still be the case. By 2017, it is hoped this is changing; [(23) ref in (14) ref].

• Once degraded, due to its slow growth rate, the coral reef system could take 100s if not 1,000s of years to come back, even if the source of pollution is removed and transplants of healthy coral are put into place. This is similar to the timeline for wildlife habitat to recover from the over-population of elephants in many land-based CBNRM programs in Southern Africa, once the elephant population is brought under control. If a mistake is made in over-harvesting wildlife, most wildlife populations, including elephant, can recover in ten years, while once the habitat is destroyed, it can take 100s of years for the vegetation and 1000s of years for the soil to recover;

• Most marine parks fail to deal with the major issues of land-based pollution and unless situated in a pristine watershed continue to degrade;

• Local artisanal fishermen are more often victims of degraded coral habitat by developers rather than the cause of the problem due to engaging in over-fishing and/or destructive fishing methods. While there is an increased need to work with artisanal fishermen to sustainably manage their fishery (e.g. breaking up the coastline/reef into fisher community-managed zones), they are not the major problem, which is coastal tourism as currently undertaken and land-based pollution in general;

• As in African parks and safari hunting areas with traditional hunters and pastoralists, hotel owners and dive operators often come into conflict with local fishermen, trying to stop access to areas that their families have fished for 100s of years in favor of exclusive high-paying clientele – SCUBA divers. This is analogous to wealthy tourists visiting Africa’s parks and hunting blocks, while the local community is excluded from the lands of their ancestors - both fisher and rural communities compressed into areas that can no longer ecologically sustain them;

• Coastal tourism in the tropics negatively impacts local cultures, often turning the sons and daughters of fishermen into drug dealers, gigolos and prostitutes from the immoral Western values imported by tourists;

• Most governments and NGOs fail to recognize the problem of land-based pollution, assuming that marine biodiversity can be protected by declaring an area a park, by putting up marker and mooring buoys, banning fishing and educating sport divers not to touch the corals. The problem is orders of magnitude more complex than this, but this simplified approach brings in lots of money to the NGOs from donors and from publicity directed at an ignorant, uninformed public contributing to the wrong cause;

• Dams in Africa have also had major adverse impacts on marine & estuarine fisheries. Freshwater flows help support marine fish production, as many marine fish spawn in the brackish waters of estuaries or deltas, whose salinities range between seawater (35 ppt.) and freshwater. A decrease in freshwater flow and in nutrients due to dam construction affects nursery areas in a number of ways, including increasing salinity, allowing predatory marine fish to invade and reducing the available food supply. Linked to the aquatic food chain, mangrove ecosystems can also be adversely impacted. Thus dams and flow regulation emanating from these dams, if not properly managed, can impact estuarine/near-shore water quality (e.g., salinity, nutrient availability), adversely impacting aquatic life. As a result of dams on the Senegal River, it is estimated that fish production in the river and estuary has dropped by 90% and has probably also adversely impacted marine fisheries through the loss of nursery functions for mullets (Mugilidae), shrimp (Penaeidae), shad (Ethmalosa fimbriata) and other species having an obligatory estuarine life history stage. On the Gambia River, there is a strong risk that a coastal/estuarine fishery yielding about 23,000 metric tons/year valued at Dalasis 66 million (US$ 11 million)/year at mid-1980 conversion rates would be significantly degraded along with a major dieback of mangroves, critical to the detrital food chain, as a result of the proposed Balingho Anti-Salinity Barrage. Dams on the Zambezi River have had a major adverse impact on Mozambique’s shrimp fishery. Prior to the Aswan High Dam (pre-1970), nutrients carried into the Mediterranean during the flood season resulted in large plankton blooms. This supported a large sardine fishery accounting for 30-40% of the annual Egyptian marine fishery yield. With the Aswan High Dam, and the elimination of the annual flood, the sardine fishery fell from 18,000 tons to less than 1,000 tons. The catch has since risen to a few thousand tons attributed to improved catch technologies, not necessarily a return in production. The shrimp yields at the mouth of the Nile also decreased by 67% with the elimination of nutrient supplies. Landings of other fish were 77% below pre-dam levels.

• Other issues include damage to coral reefs by divers (education critical) and boat anchors (permanent moorings, or the dive boat floating with the divers’ bubbles or a diver-towed buoy can solve this), dredging to create harbors, opening lagoons as harbors, filling in salt ponds/lagoons for housing developments, elimination of unsightly mangroves, unregulated harvest of coral and sea life for the aquarium trade, location of tourist lodges and lights too close to the beach affecting turtle nesting and sex ratios (the closer the eggs are laid to the waterline, the lower the temperatures and the more males are among hatchlings), as well as survival of the hatchlings (driven by lights from tourist hotels inland to their death); and • Global issues such as planetary and ocean warming, the breakdown in the ozone layer, etc. have become increasingly important since the late 1990s