Part III - Discussion:

In the face of global change, it is a major challenge of our time to understand the capacity of the tropical marine system to meet human needs without compromising opportunities for future generations. Our current problem deals with the understanding the effects of human induced changes in relation to changes brought on by natural causes on both a global and a local level.
Fortunately, there is a clear awareness of environmental issues at the governmental level and efforts were and are being made to improve knowledge in some areas. A number of marine protected areas have been established and active management is under way. The remote island of Aldabra has long been recognized for its unique flora and fauna and is well protected with a research station and permanent staff.
Before one can understand how to gauge a reef's health and resilience, one must first understand the dynamics behind the change, and the variables involved in recovery. Is it the number of young (larval species) which re-establish at a site that determines a faster recovery, or is it the amount of nutrients which enter the area, or is it the survival rates of populations once they have established themselves?
Nutrients are brought in an cycled out. Fish and coral populations in one region are linked to their spawning source in another. Cyclones or crown-of-thorns starfish destroy a portion of the reef in one year, while another area is still recovering from similar destruction several years earlier. Seaweed growth can be brought on by excess nutrients introduced by agricultural run off, a depletion of herbivores such as certain fish species or both. The system is even more complex than terrestrial systems.
It is thus important to understand the role and synergy between these variables in order to make recommendations to management authorities. Only then, it is possible to implement management concepts to preserve the fragile near-shore reef communities and its diversities of the Seychelles. On a local level, specific actions should involve:

Fishery Management supported by scientific investigation: Most biological issues of concern regard over-harvesting, harmful methods of harvesting and the continual degradation of important fish habitats. To properly understand the degrading effects of excess fishing practices, it is advisable even at this stage to investigate:

  • the response of fish populations to over-fishing and the natural replenishment of their populations;
  • what determines the number of fish larvae which replenish populations (is it the amount of available food? the number of predators? or the currents which bring larvae into an area? what kinds of effects do human-induced changes have on fish populations versus natural disturbances brought on by cyclones, crown-of-thorns starfish outbreaks, or El Niño events?

In addition, remote satellite sensing of phytoplankton should be done in order to quantify the level of primary production. Upper trophic levels, such as the grazing of zooplankton, and in turn secondary and tertiary consumer levels should be screened to obtain detailed data about total biomass productivity. Further detailed scientific studies should help to shed light onto the nutritional preferences that larval fish prefer and the amounts eaten by fish during one day, which ultimately, will make fishery management sustainable as it will be possible to determine flexible quotas for the amount of fauna that can be harvested without damaging the trophic relationships.

Acanthaster planci (Acanthasteridae) - a notorious nocturnal predator of scleractinian (branching) corals (150kB)

A cosmopolitan herbivore Eretmochelys imbricata (Chelonidae) (120kB)

Two Scorpaenopsis diabolus (Scorpenidae) on an eroded Lobophyllia sp. (185kB)

Apart from the direct nutritional benefits on an intact marine habitat, there are some other aspects of interest:
Marine Bioproducts: Marine organisms often produce chemicals as a means of defense or as an offensive weapon. Scientists are now beginning to look at such bioactive chemicals in order to discover new drugs or other useful products for humans, animals health, agriculture and other industries (for example, corals are sources of sun-protective chemicals and stonefish contain neurotoxins). It is already a scientific fact that chemicals of the mucal sheath in corals produce an UV-protective agent. Marine aquacultural practices could thus be applied to manage coral gardens and harvest a byproduct which could be used as a natural sunblocker.


Lobophyllia sp.(Mussidae) inbetween Cyphastrea sp. (Faviidae) left and Acanthastrea (Mussidae) right (160kB)

Species Intrusion: It is also advisable, to monitor the increasing boat traffic - especially that of large container vessels. The remote location as the Seychelles in particular should address the topic of ballast water by studying sources of paralytic shellfish toxins which international ships may introduce to their marine environment.
Such investigation can even promote recolonization of bleached or otherwise destroyed coral habitats, in that certain algae are known to produce chemicals that can induce coral larvae to settle on substrates. In a time when the destruction of coral reefs are causing severe coastal degradation, loss of biodiversity, and decline in harvestable fish population, discovering chemicals might aid in the recovery of such reefs is of great importance.

Plankton loaded waters attract the pelagic cosmopolitan Rhincodon typus (Rhincodontidae) (95kB)

Changes in species composition: It is essential to reveal the role and significance of soft corals on coral reefs especially at this stage, as many reef sites of the Seychelles are still suffering from the impacts of the 1998 ENSO. It was observed that soft corals, part of a normal coral reefs, in some circumstances are suspected of being an indicator of reef degradation. Thus, it is essential to understand nutritional requirements of soft corals, their distribution, dispersal and how often they are found in disturbed areas before one can judge their usefulness as a symptom of poor reef health. Likewise important are patterns and causes of algal distributions on the reef in order to distinguish natural differences between reefs from changes in the reef benthos, which may be caused by human activities on the reef or adjacent land.
Another useful indicator are the chemicals many marine plants and animals produce for defense or in response to stress. Monitoring certain chemicals may be a useful indicator by signaling environmental stress situations.
Geographic and seasonal changes to reefs, as well as the strength with which corals, coral competitors and coral predators replenish their populations is another indicating agent. In addition, the analysis of coral growth rings may reveal major environmental events and climate changes during the last few centuries and how they have influenced coral ecosystems in this area.

Dendronephyta sp. (Nephtheidae / Octocorallia) have a prickly appearance due to sharp supporting bundles of sclerites (150kB)

Phyllidia ocellata (Phyllidiidae) a grazer found on shallow reefs (140kB)

ENSO: Although there are no clear records of mass-bleaching events prior to 1979, it is possible that such events could be rare but recurrent phenomena that reefs have recovered from in the past. However, the extent of coral bleaching observed during recent ENSO provides a clear indication of the wider long-term impacts of rising sea surface temperatures. Although such events are largely driven by ENSO at the present time, most climate models predict that the threshold temperatures which currently drive mass-bleaching events will be reached on an annual basis in 30-50 years.
At both the regional and local scale, certain corals have adapted to warmer, or more variable temperature regimes. These include some of the same species which have been observed to be highly sensitive to temperature variations in other areas. Such adaptation is clearly seen in the reefs of the Arabian Gulf, where temperatures fluctuate over relatively wide extremes every year. Largely unquantified observations in the central Indian Ocean in 1998 showed similar local scale survival of corals in reef flat and lagoon areas. These are likely to be subject to more extreme temperatures on a regular basis, from the reduced water circulation and exposure to solar insolation and/or cold conditions in these areas (Spalding, Teleki, Spencer et al, 2000). It remains to be seen whether coral larvae from these corals can recolonise reefs where more sensitive corals have died, or whether there is indeed sufficient genetic resilience within these species to adapt to the continuing increases in temperatures predicted under current models.
Corals may be placed under additional stress by the projected increases in atmospheric CO2 concentration. It is believed that the concentrations of aragonite in surface waters will be reduced by such increases. Aragonite is an important component of the coral skeleton, and lower concentrations will reduce calcification rates and skeletal strength. This may lead to reduced rates of reef growth and weaker skeletal structures. All reef development is the result of coral growth out-pacing natural processes of erosion, from bioeroding organisms and also physical processes such as storms. Slower coral growth rates and weaker skeletal structures may shift the balance of many reefs from that of gradually accreting structures (catch-up reefs) to that of gradually eroding structures (give-up reefs), and this change will be further compounded by increasing rates of sea-level rise.
The 1997-1998 mass-bleaching event is providing a critical model of potential future impacts of climate change on coral reefs globally. Mass-mortalities were largely unpredicted and the wider ecosystem impacts, together with the potential for recovery and adaptation remain largely unknown.
Although new coral growth is now observed in most areas, there is some concern that mortality on such a massive scale could have lead to local disappearance of certain species, driving a loss in diversity and changes in community structure.
Despite some recovery, fast growing branching corals (providing there isn't another warming episode) may still take 6 to 10 years. (in most cases even more). In cases where massive species (e.g. Poritidae) have been effected, recovery may even take several decades if not a century.

Small colony of Leptoseris sp. (Agariciidae) (160kB)

A young Physogyra lichtensteini (Euphyllidae) on top of a dead larger one (135kB)

Detail of Symphyllia sp. (probably S.recta Mussidae - 130kB)

Tubastrea colonies in 30m deep waters - members of the almost azooxanthellate Dendrophylliidae (85kB)

Young Favites russelli (Faviidae) surrounded by coralline algae (185kB)

And finally, the snorkelling and diving public: Even though, at the current level, it is not yet a pressing issue, dive tourism is and more so in the future will be an important source of income for the locals. As there are both land bases and a live aboard which operates into the furthest reaches of the Seychelles archipelago it is essential to manage this growing industry properly. Dive boat anchors cause damage to reefs, smashing corals when they are thrown overboard. Providing floats or buoys for boats for tying up instead of anchoring can eliminate this impact.
The state government of the Seychelles should try to come up with mooring buoys, where (dive) boats bringing divers into these areas, can tie up their vessels to these buoys as not to drop their anchors onto the recovering coral population. In this way, mooring buoys serve as a system to curtail any damage to corals, especially in the long run, when coral growth has reshaped the fringing reefs of the Seychelles.
But there is more than the small boat traffic. It is really in the industry's best interest to encourage instruction on proper buoyancy and to make sure that divers are well trained before they actually get off on their own and onto the reefs. Divers also knock corals with their hands and fins when they don't have their buoyancy devices under control. Even experienced divers, who are photographers can damage corals in their enthusiasm to get a good shot. And then there are the beginners (those who don't know how to keep their fins up). These people should be channeled into heavily degraded sites with maybe a rich fish fauna. Only when they have acquired the proper skills and are adequately trimmed, they should be allowed to get to know the more pristine places. This way the operators can make sure that the best spots still will be as pristine as they are.
Dive operators even should be proponents of "conservationism" by trying to teach a little ecology along with the diving skills, so people go into the water and realize the full potentials of a reef ecosystem, how fragile most living reef-organisms really are and that even though scleractinian corals are a kind of rough, hard, and sharp, they can be damaged quite easily just by a stroke of a fin, the touch of a finger or by careless anchor dropping.
To maintain a healthy reef environment it is essential to police ourselves, and to make sure that future generations can admire them in the same way as we do .... once the original splendor is back.

Young Favia sp. (Faviidae) and larger Porites sp. (Poritidae) above (170kB)

Close up of Porites sp. (Poritidae - 170kB)

Junceella sp. (Antipathidae) are frequently seen in greater depths - (100kB)

School of omnivorous Platax teira (Ephippidae) - feed on algae and small invertebrates (70kB)

Literature: Colin P.L; Arneson C.; 1995; Tropical Pacific Invertebrates; Coral Reef Press; California - USA.
Fabricius K.; Alderslade P. 2001; Soft Corals and Sea Fans; A comprehensive guide to the tropical
     shallow water genera of the central-west Pacific, the Indian Ocean and the Red Sea;
     AIMS; Townsville - AUS
Gosliner T.M., Behrens D.W., Williams G.C.; 1996; Coral Reef Animals of the Indo-Pacific;
     Sea Challengers; California - USA.
March L., Slack-Smith S.; 1986; Sea Stingers; Western Australian Museum, Perth - AUS
Mojetta A.; Ghisotti A.; 1998; Pesci e Coralli del Mar Rosso; Arnoldo Mondadori Editore Spa,
     Milan - ITA
Pears V.&J.; Buchsbaum M. & R.; 1986; Living Invertebrates; Boxwood Publishers,
     Los Angeles , CA - USA.
Spalding M.; Ravilious C.; Green E.P.; 2001; World Atlas of Coral Reefs; UNEP World Conservation
     Monitoring Centre; Cambridge - UK
Veron J.E.N.; 2000; Corals of the World; Australian Institute of Marine Science; Townsville - AUS.
Wood E.M.; 1983; Corals of the World; TFH Publications Inc Ltd - USA
Further References: Australian Institute of Marine Science in Townsville - AUS:
Recent AIMS Report sheets: Human Impacts on Coastal Marine Ecology; Marine Biogeochemistry of
     Contaminants; Marine Bioproducts; Monitoring Change in Tropical Marine Biota;
     Predicting the Coastal Marine Environment; Supporting Tropical Fisheries;
     Sustaining Coral Reefs;
Caroline Cort 1996; One World - Anchoring and Diving on coral reefs;
     Australian Broadcasting Corporation; Melbourne - AUS
References on the web: Picture gallery Seychelles:
ENSO - (El Niño-Southern Oscillation):
State of the world reefs - Bigot L., Charpy L., Maharavo J., Rabi A.F., Paupiah N.,
Aumeeruddy R., Viledieu C., Lieutaud A.
2000; AIMS, Townsville - AUS
State of the reefs around Mahé island
TBL (Tissue Bleaching):
Curio trade