[Coral-List] symposium on effects of biodiversity on the coral reefs in the Pacific

Charles Birkeland charlesb at hawaii.edu
Thu Dec 21 02:43:45 EST 2006

Biodiversity and Coral Reefs in Asia – Pacific

Recently, there have been publications concerned with the effects of biodiversity loss on marine ecosystem services. These articles have focused mainly on the tropical western Atlantic.  The Pacific covers a third of the Earth and provides some different perspectives from the tropical western Atlantic. First, there is a major gradient of decrease in species richness from west to east across the Pacific from SE Asia (more than 500 species of scleractinian corals) to eastern Polynesia (perhaps less than 100 species). Even higher taxa of reef fauna are absent from eastern Polynesian reefs (e.g., 91 species of crinoids are listed from Indonesian reefs, while none of the Class Crinoidea are on reefs of the Society Islands, Marquesas, and Hawaii). Coastal habitats such as mangroves were also naturally absent in the east. Clipperton Island has only eight or nine species of scleractinians, yet the reef ecosystem appears robust and productive. The relative loss of ecosystem function 
and services on substantially less diverse French Polynesian reefs in comparison with more diverse Japanese or Philippine reefs has not yet been demonstrated. This gradient of decrease in species, higher taxa and habitats across the Pacific allows natural experiments on large scales.

This coming June 12-18, the 21st Pacific Science Congress will be held in Okinawa.  “Biodiversity and Coral Reefs in Asia – Pacific” is a symposium at this Congress. This letter is an invitation to come and present your data and observations on the implications of patterns of biodiversity on coral reefs across the Pacific.

The second new perspective is that the total lists of species for islands or archipelagos in the Pacific are possibly increasing at a more rapid rate than ever before in the history of the Earth.  For example, as far as I know, there have been no recent extinctions in marine life in the main Hawaiian Islands, but at least 287 species of marine invertebrates have been documented as having been added to the coastal fauna in recent years. Guam has gained at least 85 additional marine species. Of course the rate of addition of introduced species possibly does not allow time for evolutionary accommodation by niche shifts, but does this added species richness increase redundancy and stability to the system? 

MacArthur, Ehrlich and Ehrlich, and numerous others have proposed that systems are more ecologically stable if the species richness or species diversity is greater because with more participating species, the greater the chance that critical ecosystem functions are accommodated. Does this dramatic drop in species diversity imply that reefs are less resilient from west to east? Are the reefs of Okinawa, Palau, and the GBR more resistant to outbreaks of Acanthaster and Drupella than reefs in American Samoa, Tahiti and Hawaii? Do reefs of Okinawa, Palau and the GBR recover more quickly from Acanthaster outbreaks, hurricanes, lava flows than those of Samoa or French Polynesia?  Or, alternatively, is resilience more strongly affected by the environmental circumstances and the presence of certain key species.

Robert Paine, Michael Soule, John Terborgh, and David Bellwood have called attention to the possibility that most critical species are not redundant. Are other Caribbean echinoids redundant with Diadema antillarum? No other parrotfishes do what Bolbometapon does. Is the pattern of urchins filling in and doing the job for herbivorous fishes on the north coast of Jamaica a result of the diversity of urchins and fishes at these sites or a result of ecological effects of particular characteristics of Diadema antillarum and the herbivorous fishes?

If an equilibrium is reached among native and introduced species, will there be a substantially greater number of species in archipelagos, with more homogeneity among archipelagos?  Will the added number of species lead to adjustments in niche dimensions, or will there be competition and local extinctions? Sam Kahng and Rick Grigg have been studying the introduced octocoral Carijoa riisei in Hawaii. It has invaded the deep reefs and has been overgrowing and killing numbers of black corals. But I think Sam Kahng has also found that the Carijoa riisei avoids lighted conditions in which black corals can survive. Perhaps Carijoa and black corals partition a range of conditions that black corals previously had for themselves. Now we have added Carijoa riisei to the species list. Black corals are still here, but I think Sam is finding that they soon may have a more restricted niche space and lower abundance. But the species list may be growing for Hawaii.

A number of small-scale experiments by Tilman and others in the terrestrial realm have shown that more diverse systems can be slightly more efficient at the ecosystem level of function, but there was increased instability at the population level.  However, Don Kinsey, in D.J. Barnes’ 1983 book on Perspectives on Coral Reefs, documented the relatively consistent ecosystem level functions of primary production and carbonate turnover in Atlantic and Pacific reefs with studies at widely varying levels of species richness. Ewel and Bigelow and others likewise found in the terrestrial realm that simple agroecosystems and other areas across a range of species richness performed ecosystem processes similarly to neighboring tropical rainforests. Does the decreasing diversity of reef biota from Okinawa towards French Polynesia indicate that nutrient recycling more efficient in Japanese, Indonesian and Philippine waters than in French Polynesia? The diversity of both reef constructors 
and bioeroders also decreases from west to east. Does this suggest that carbonate turnover is different from west to east? Whether coral-reef ecosystem processes are substantially influenced by species richness and redundancy are questions that need to be resolved.

A few possible questions: 

•	Do efficiencies or rates of ecosystem processes such as nutrient recycling, reef accretion, and gross and net productivity decrease along the decreasing gradient of biodiversity from west to east across the Pacific?

•	Are reefs in the western Pacific more resistant and resilient (more rapid recovery) to damage by hurricanes, large-scale bleaching events, lava flows, outbreaks of predators (Acanthaster, Drupella) than are less diverse reefs in the eastern Pacific? 

•	Are reefs in the western Pacific more resistant to invasion of introduced species than are reefs in the eastern Pacific?

•	Relatively few introduced species spread from harbors to outer reefs. Is this because the more diverse outer coral reefs resist invasion, or because the introduced species that spread by initially attaching to ships at anchor more adapted to backwaters of harbors than to outer reefs?

•	Do introduced species cause local extinctions or reduced niches of native species, or is it a first come first serve lottery with just more species in the association?

(This letter is just to provoke you into participating in the symposium. Let’s not burden CoralList with discussion of these topics.)

If interested in participating in the symposium on Biodiversity and Coral Reefs in Asia – Pacific at the 21st Pacific Science Congress, the scientific program, schedule, registration, hotel accommodations, and necessary information on Abstract submission and the online Abstract Form are available on 


The deadline for Abstracts is January 15.

We hope you will participate.

Makoto Tsuchiya   tsuchiya at sci.u-ryukyu.ac.jp

Charles Birkeland   charlesb at hawaii.edu

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