Pacific Science (1992), vol. 46, no. 3: 374-382© 1992 by Un iversity of Ha waii Press. All rights reserved

Coral Reefs and Environmental Change-The Next 100 Years:A Synopsis and Abstracts of Papers Presented at a Symposium of

the XVII Pacific Science Congress1

RICHARD W. GRIGG2

Abstracts of 14papers presented in a symposium held at the XVII PacificScienceCongress in Honolulu in Ma y 1991 follow. The symposium, sponsored by thePacific Science Association's Scientific Committee on Coral Reefs and theWestern Society of Naturalists, addressed the problems of man-induced andnatural environmental change to coral reefs on both short- and long-term timescales.

The plenary address by Donald W. Kinsey on the greenhouse effect and coralreefs pro vided an overview of how change associated with global warming mightaffect coral reefs over the next several centuries. In the papers that followed , theeffects of sea-level change on atoll s were discussed by Colin Woodroffe andRoger McLean, who showed how the growth form of micro atolls might be usedto interpret average water level and hence past and present trends in sealevel. In another paper on sea-level change, F . J . Murphy, D. R. Stoddart, C. E.Cook, and C. A. Cartier illustrated how dating and geomorphological analysisof motus can be used to determine past sea-level history. Two papers dealing withclimate variability on the order of decades focused on the effects of EINino- southern oscillation (ENSO) events on coral reefs. C. M. Eakin describedthe severe mortality and bioerosion that took place in the eastern Pacificfollowing the ENSO event in 1982-1983 and warned that if global warming leadsto an increase in the magnitude and frequency of ENSO events, coral reefs inthe eastern Pacific might be threatened with extinc tion. The effect of ENSOevent s in Indonesia was examined by Lisa Wells, Michael Moore, and RichardFairbanks, who, by analyzing humic acids and oxygen-l 8 in the annual bandsof coral colonies (Porites lobata) in Indonesia, showed that the characteristics ofENSO events in that area are virtually the opposite of those in the eastern Pacific:drought, low river discharge, and cool high-salinity surface water.

Three papers in the symposium dealt with change on coral reefs caused byanthropogenic sources of stress : heated effluents from power plants andpoint-source discharges from ocean sewer outfalls and sugar mills. Tsu-ChangHung, Che-Chung Huang, and Kuang-Lung Fan described the impact ofeffluent from a nuclear power plant in southern Taiwan where coral mortalityoccurred in areas where water temperature exceeded 31°C but the effectswere highly localized. The effects of hot water effluent from a diesel-fired powerplan t averaging 34°C on a fringing reefin Guam were described by H. G. Siegrist,K. G . Bowman, R. H. Randall, and P. B. Stifel: scleractinian corals were killedover an area about 10,000 m square. R. W. Grigg, dealing with point-sourcepollutants, showed that impacts of sugar mill effl uents discharged in Hawaii are

1 Manu script accepted 9 September 1991.2 Depar tment of Oceanography, University of Hawaii

at Manoa, Honolulu , Hawaii 96822.

374

Coral Reefs and Environmental Change-ABsTRACTS

significant but localized; in contrast, ocean outfalls in Hawaii apparentlyproduce no negative environmental impacts.

Another series of papers dealt with the need to monitor long-term environ­mental change on coral reefs globally. Bernard Salvat argued for a world coralreef site network to establish a global database. On this scale, impacts to coralreefs might serve as a means of assessing global climate warming. S. L.Olhorst, W. D. Liddell, and R. J. and J. M. Taylor offered several approachesto reef censuses and concluded that no one census method could be utilized onall reefs. C. W. Evans described patterns of recovery and change of coral reefsin Kaneohe Bay, Hawaii, and C. Hunter and J. Maragos discussed the potentialof using recreational divers to conduct large-scale long-term monitoring studiesof coral reefs.

In the final paper, Susan M. Wells provided an overview of human impact onmodern reefs worldwide , arguing that over the short term coral reefs must beviewed as fragile ecosystems in need of conservation, while at the same timerecognizing that on longer time scales, coral reefs have weathered and survivedsignificant climate changes including cycles of sea level rise and fall.

The most difficult challenge faced by coral reef biologists to emerge duringthe symposium is the problem of separating anthropogenic change from naturalvariability on coral reefs. Long-term monitoring studies in a variety of reefsettings are needed to establish baselines against which anthropogenic impactscan be measured. Coping with this problem on a global scale and developingsuccessful management strategies will be the challenge of the future to coral reefscience.

The Greenhouse Effect and Coral Reefs

D. W. KINSEy3

375

Current predictions concerning the green­house effect contain many uncertainties.However , some significant sea-level risereaching at least 6-8 mm/yr by 2050 seemslikely. Coral reefs can achieve vertical growthof perhaps 15 mm/yr for short periods anda sustainable modal maximum of about 8rum/yr. Thus they could keep pace with anylikely short-term greenhouse scenario. Wheth­er they will, in fact, respond with recoloniza­tion of presently depauperate reef flats andrenewed vertical growth is subject to contro­versy. In the past, reefs have both succeededand failed to do so without clear explanation.Most other attributes of the greenhouse effectcould discourage renewed growth -tempera-

3 Great Barrier Reef Marine Authority, Townsville,Australia.

ture increase, increased storminess, fresh­water and nutrient run-off, decreased in­solation. However, these predictions relateprincipally to subtropical latitudes. Presently,temperature is receiving the most attention.Recent worldwide coral bleaching is com­monly attributed to early indications of thegreenhouse effect. It seems more probablethat it should be attributed to a period oftemperature instability unrelated to the green­house effect. In fact there is little reason topredict that a slow, steady temperature in­crease of I-2°C over 50 yr or more could notbe tolerated by all but reefs in the mostextreme locations. Increased storminess couldact to slow down recolonization. Increasedrun-off is certainly a negative influence, but atleast most open-water reefs are not particu­larly vulnerable. On balance, it seems that the

376

short-term response to the greenhouse effectis likely to encourage increased reef growthprovided weather and temperature changesare not too erratic. The role of reefs as carbonsinks has received some popular attention.They are portrayed as majo r sinks for CO2and therefore as potential saviors from in­creases in greenho use gases. In fact, theypresently act as a sink for the equivalent ofonly about 2% of the anthropogenic CO2 ,

Although this could double in the most opti­mistic 100-yr scenario, this is still of limitedsignificance. More important, the marine de­posit ion of limesto ne actually decreases the

PACIFIC SCIENCE, Volume 46, July 1992

ability of the ocean to absorb CO 2 from theatmosphere . The fate ofcoral cays is probablyless controversial. Redistribution of reef sedi­ment reserves will facilitate island perimetersgenerally keeping pace with rising sea leveluntil the sand reserves are depleted. The cayswill then erode rapidly. The time scale forthese respon ses is varia ble, reef to reef. Not­withstanding the positive value of this earlydynamic respo nse to sea level, the penetrationof salinity into the freshwate r lenses of theislands will be a majo r negative effect forisland comm unit ies even in the short term .

Coral Atoll Development: A Holocene Perspective on Responseto Sea-level Change

R. F . M cLEAN4 AND C. D . WOODROFFE5

Coral atoll s in the Indian and Pacific oceansconsist of sheltered lagoons encircled by reefsupon which are low-lying islands of generallyunconsolidated sand or shingle. These reefislands appear particularly vulnerable to in­undation should the sea level rise as is antici ­pated as a result of the greenhouse effect.Entire atoll rims, with associated islands ,have developed under conditions of chang ingsea level. Investigation of the stratigraphy,chronology, and pattern of Holocene geo-

morphological development of coral atollsallows us to decipher some of the responses todifferent rates of sea-level change in the past.The complex surface morphology of mostatoll s results from a period of sea-level stabil­ity, if not sea-level fall over the last 3000-6000years. The landforms are likely to exhibitsome resilience in the face of gradual sea levelrise, but are unlikely to be preserved in theirpresent form if the sea rises at the most rapidof the rates predicted.

Coral Microatolls and Recent Sea-level Change on Atolls

C. D. WOODROFFE6 AND R. F . M cLEAN7

Microatolls are colonies of massive coralsthat generally are dead on their upper surface

4 Departm ent of Geography and Oceanography, Aus­tralian Defense Force Academy, Canberra, Austral ia.

5 Department of Geograph y, University of Wollon ­gong, P. O. Box 1144, Wollongong, N.S.W. 2500,Australia.

6 Department of Geography, University of Wollon­gong, P. O. Box 1144, Wollongong, N.S.W. 2500,Austra lia.

7 Department of Geograph y and Oceanograph y, Aus­tralian Defense Force Academ y, Canberra, Australia.

but alive around their perimeter. Their up­ward growt h is constrained by the water levelof exposure during low spring tides. X raysof vertical slices through these corals revealannual density banding that can be inter­preted to reconstruct year-to-year changesin the upper limit of coral growth, indicatingtren ds in sea level. Microatolls thus act aslong-term water-level recorders and are ofspecial significance on low-lying coral atollswhere sea-level rise could have devastatingeffects.

Coral Reefs and Environmental Change-ABsTRACTS

Geomorphology of the Motus of Moorea, French Polynesia

F. J. MURPHY, D. R. STODDART, C. E. COOK, AND C . A. CARTIERs

377

The physical structure of motus is highlysensitive to environmental influences. Precisefield surveying and laboratory analysis ofrock and sediment samples allow a categoriza­tion of geomorphologic features in both timeand space and a reconstruction of the evolu­tionary history of the motus with respect tosea-level fluctuations , storm activity , and tidalcycles. In this paper, geomorphological datacollected from three of the five mot us on theisland of Moorea are presented . Geomorpho-

logical features on these motus include con­glomerate platforms, beachrock, cay sand­stone, and sedimentary environments rangingfrom fine-grained sandy beaches to boulderfields. Mapping was carried out using lasersurveying equipment (EDM), which producesexactly vertical and horizontal coordinates foreach point surveyed and is the most accuratemethod available for determining the posi­tions of coastal features .

The 1982-1983 El Nino: Impact of Eastern Pacific Reef Carbonate Budgetsand Implications for Severe Bleaching Disturbances

C. M. E AKIN9

Sea surface warming during the severe andprolonged 1982-1983 El Nino- southern os­cillation (ENSO) event resulted in bleachingand mortality of over 50% of reef coral coverat Uva Island, Panama. Subsequently, densi­ties of the eroding echinoid Diadema mexi­canum increased from pre-ENSO values of 3individuals/m" to at least 50 individuals/rrr'in the seaward reef base zone, where erosionof the reef framework currently exceeds 13 kgCaC03 /m 2/yr , producing a vertical loss of22mm of framework per year . A preliminary

8 Department of Geograph y, University of Californiaat Berkeley, Berkeley, California 94720.

9 Rosenstiel School of Marine and Atm ospher ic Sci­ence, Division of Marin e Biology and Fisheries, Univer­sity of Miami, Miami , Florida.

CaC03 budget of Uva Island reef has beencalculated from estimates of production bycorals and coralline algae, framework de­struction by D. mexicanum, infaunal eroders,fishes and other motile eroders, and sedimentretention within the framework. Damse1fishand their algal lawns protect portions of thereef from erosion, contributing significantlyto the budget. The combination of coralmortality and increased densities of erodingechinoids resulted in a 60% decline in netCaC03 deposition. The budget for the sea­ward reef base has shifted from net carbonatedepo sition to a net loss ofalmost 3 kg CaC03 /

m2/yr. Mortality due to thermal stress such assevere ENSO events may not only alter thestructure of coral reef communities, but alsolead to destruction of reef frameworks .

378 PACIFIC SCIENCE, Volume 46, July 1992

Climate Variability of the Indonesian Low and Southern OscillationReconstructed from the Geochemistry of Annually Banded Reef Corals

L. WELLS, 10M. MOORE/lAND R. FAIRBANKS 12

Precipitation and sea surface temperature(SST) in Southeast Asia are closely coupled tothe southern oscillation (SO) because theirvariability is a function of the intensity andposition of the Indonesia Low, itself a mea­sure of the heat flux that drives Walker Circu­lation. SO positive phases produce heavyrainfall; high river discharge; and anoma­lously warm, low-salinity surface waters. SOnegative phases (ENSO) produce drought;low river discharge; and cool, high-salinitysurface waters. Precipitation records substan­tiate the correlation between Southeast Asianrainfall and the SO: wet-season peak rainfallis at or below the annual mean , indicatingfailure of the wet-season monsoon during64% ofhistorical ENSOs; only two significantfailures of the monsoon occurred during years

not recognized as ENSOs. Because the posi­tion of the Indonesia Low is an index of theSO, proxy data recording fluctuations of theIndonesian Low also serve as proxies for theSO. Annual bands in Indonesian reef corals(from Sulawesi, Bali, Lombok, and Ambon)are sampled every mm to reconstruct near­monthly climate variability. Stable isotopevariations record SST and salinity: c5 180 time­series display maxima during ENSO and min­ima during SO positive phases. Chemicalfluorescence variations record freshwater dis­charge into the littoral: fluorescent bandingshows strong minima during ENSa and max­ima during SO positive phases. Coral proxydata are used to present a regional picture ofvariability of the Indonesian Low and the SOfor the past 100 yr.

Factors Affecting Shallow Coral near the Taiwan Third Nuclear Power Plant

TSU-CHANG HUNG, 13,14 CHE-CHUNG HUANG,13 AND KUANG-LUNG F AN 13

Since the Third Nuclear Power Plant inTaiwan started to operate in January 1987,two incidents of massive but localized deathof corals have occurred. Heated water dis­charged from the outlet was the major factor

10Department of Geography, University of Californiaa1 Berkeley, Berkeley, California 94720.

I I Museum of Paleontology , University of Californiaat Berkeley, Berkeley. Californ ia 94720.

12Lamont Doherty Geological Observatory, Pali­sades, New York.

13Institute of Oceanography, Nat ional Taiwan Uni­versity, Taipei , Taiwan .

14Institute of Chemistry, Academia Sinica, Taipei,Taiwan .

causing mortality. Therefore, since July 1987,we have closely followed the thermal effectson coral reefs along the shallow-water coast.In general, except for temperature, the watersampled along the shallow bay meets thecriteria set by the Taiwan EnvironmentalProtection Administration. Temperature ofthe surface water (to 3 m) near the outletusually exceeds 31°C. Growth rate of coralsin the shallow bay showed a steady decreaseduring the period July 1987 to October 1988.However, after the discharge rate was in­creased by 10% in May 1989, coral growthrates stabilized. In this paper we summarizethe results and discuss data collected up toSeptember 1990.

Coral Reefs and Environmental Change-ABsTRACTS 379

Diagenetic Effects Related to Hot-water Effluent in a Modern Reef on Guam

H. G. SIEGRIST, 15 R. G . BOWMAN,! 6 R. H. RANDALL,! 7 AND P. B. STIFEL 16

Hot-water effluent, averaging nearly 34°C,from a diesel-fired power plant has beendischarging onto a fringing reef along thenorth-central leeward coast ofGuam for near­ly 20 yr. Early estimates of coral mortalityshowed that the plume was ca . 10,000 m2

in area. Recent reexamination of the affectedreef suggests that major differences appearto be biological. Highly significant increasesin bioeroders (principally sipunculans, poly­chaetes, and clionid sponges) and persistentbut less significant increases in encrustion

(by coralline and blue-green algae , vermetids,and Homotrema) mark all substrates of theaffected reef. Diagenetic cemen ts at affectedsites show no significant difference in styles,diversity, volume, or trace-element composi­tion in compa rison to cements forming at thecontrol site; however, whole-rock strontiumshowed major depletions on the affected reefowing to encruster s replacing coral popula­tion s. These results show that hot-water efflu­ents produce both biological and geochemicalchanges on fringing reefs.

Environmental Impacts of Point-source Pollution on Coral Reef Ecosystemsin Hawaii

R. W. GRIGG 18

In 1989, the State of Hawaii initiated along-term mult idisciplinary cooperative re­search program called the Main HawaiianIslands Marine Resource Investigations. Thepurpose of this program is to assess the statusof nearshore marine resources in Hawaii andto improve methods of management. Theresults of one of the projects in the programthat deals with environmental impacts ofman-induced point-source pollution on near-

ISWERI- UOG, Mangilao, Gu am 96923.16Department of Geology, University of Maryland ,

College Park , Maryland 20742.17 Mar ine Laborat ory, University ofGu am, Mangilao ,

Guam 96923.18Department of Oceanography, University of Hawaii

at Manoa, Honolulu , Hawaii 96822.

shore coral reef ecosystems is describ ed in thispaper. Two major sources of point-sourcepollution exist in Ha waii. These consist ofdischarges from ocean sewage outfalls andsugar mills. Surveys show that the impactsassociated with each are highly localized.In the case of sewer outfalls, no significantchanges in surrounding benthic ecosystemshave occurred. Fish populations near theoutfalls and outfall pipelines are substa ntiallyenhanced. Impacts from sugar mills on ben­thic ecosystems and reef-fish populations arelargel y confined to within I mile (1.6 km) ofdischarge points. Within these areas, whichare designated zones of mixing by the StateDepartment of Health, the diversity andabundance of coral and reef-fish populationsare dep ressed. Sedimentation appears to bethe cause.

380 PACIFIC SCIENCE, Volume 46, July 1992

World Coral Reef Site Network: A Long-term Global Plan to Monitor CoralReefs for Natural and Anthropogenic Change

BERNARD SALVAT l 9

Coral reefs have been described alterna­tively as "delicately adjusted climax ecosys­tems" or "successional temporal mosaic s."Stability or instability in time and space is thequestion. Also there is a need to discriminatebetween natural and anthropogenic, andshort- and long-term population changes inreef communities. Global climate change maycause sea-level rise, as well as increased precip­itation and sedimentation on reefs, increasedfrequency of cyclones and typhoons, andrising sea temperature. Clearly there is a need

to monitor these changes over the long termon coral reefs worldwide. It is recommendedthat a Coral Reef Site Network be establishedand that it be internationally coordinated andmaintained over many decades . Major sitesneed to be selected and a standardized moni ­toring program needs to be developed. Coralreefs can serve as sentinels of future an­thropogenic and natural change. As such theymay assist mankind in understanding andcoping with global climate change.

An Evaluation of Coral Reef Census Strategies:Implications for Monitoring Programs

S. L. OLHORST,z° W. D. LIDDELL,z1 R. J. TAYLOR,22 AND J. M. TAYLOR2 2

Development of efficient and accurate cen­sus strategies for coral reefs and other marineenvironments is of the utmost importance,particularly now, as coastal settings are in­creasingly impacted by the harvesting of re­sources, development, and recreation. Wehave evaluated a number of the commonlyused census methodologies through the useof computer simulations and field studies. Theformer allowed the sampling of "known"reefs of differing diversities , spatial hetero-

19 E.P.H.E, Universite Perpignan, Fr ance.20 Department of Fisheries and Wildlife, Utah State

University, Logan, Utah 84322-5210.2 1 Department of Geology, Utah State University,

Logan, Utah 84322.22 Logan, Utah 84321.

geneities, and size ranges of organisms, whilethe latter provided the amount of real timerequired to perform the various methods andrevealed practical limitations in the applica­tion of certain methods. Our results indicatethat no one census method is universallyapplicable to all community types. Prelimi­nary evaluation of population and commu­nity parameters is essential to the develop­ment of the optimal census strategy. Giventhis caveat, certain generalizations may bemade ; for example , with increasing commu­nity complexity (increased species numberand variation in size and spatial patterns),point methods (linear point intercept, planarpoint intercept) appear to provide better esti­mates of community parameters than othermethods. Examples of the influence of com­munity structure on census method perfor­mance are presented.

Coral Reefs and Environmental Change-ABsTRACTS

Patterns of Recovery and Change of Coral Reef Communitiesin Kaneohe Bay, Hawaii

C. W. EVANS23

381

Kaneohe Bay offers an excellent example ofa large coral reef ecosystem disturbed byfactors associated with urbanization. Earlyresearch in the 1970s showed that eutrophica­tion and sedimentation caused declines incoral reef communities and an explosivegrowth ofthe green alga Dictyosphaeria caver­nosa. In 1983, 6 yr after major sewagedischarges were diverted from the bay, sur­veys showed a significant decrease in theDictyosphaeria algal cover and a remarkablerecovery ofcoral reef communities. Research­ers hoped that this pattern of recovery wouldcontinue; however , re-surveys in 1990indicate

that algal populations may once again beincreasing and coral recovery rates may haveslowed or , in some places, reversed. Periodicsewage bypasses and overflows from the oldsewage-treatment facilities in combinationwith non -point source sewage dischargesmay be the cause . Alternatively, natural fluc­tuations and/or other environmental factorsmay explain these changes. Continued moni­toring of water quality and more extensivesampling of coral reef communities areneeded before the question can be answereddefinitively.

Methodology for Involving Recreational Divers in Long-term Monitoringof Coral Reefs

C. HUNTER24 AND J. MARAGOS25

The health and protection of coral reefs areessential to the economic well-being as wellas the maintenance of biological diversityof island states and nations throughout thePacific. Widespread concern about coral-reefdeterioration has arisen in response to in­creasingly numerous reports of coral mor­tality resulting from various environmentalinfluences. However, long-term monitoringdata to base quantification of perceivedchanges and to provide early warning ofdegradation of reefs are notably sparse. Inlight of global climatic changes as well asrapidly accelerating urbanization pressures,

23 Department of Geography, University of Hawaiiat Manoa, Honolulu, Hawaii 96822.

24 Hawaii Institute of Marine Biology, University ofHawaii, Kaneohe, Hawaii 96744.

2 5 Environment and Policy Institute, East-West Cen­ter, Honolulu, Hawaii 96848.

we believe that there is an immediate need toimplement a permanent reef monitoring pro­gram in Hawaii and other tropical Pacificareas. In the past, accurate censusing of reefhabitats required the labor, time, and cost­consumptive work of highly trained profes­sionals. Studies done to date have thereforebeen sporadic, geographically scattered, andof short duration, lasting only as long asvarious or temporary funding allowed andinvolving a variety of techniques that wereoften inconsistent. New technologies in under­water video and computer software have beendeveloped within the past year that allowprecise, quantitative surveys to be conductedrapidly and with high resolution. We suggestthat a great untapped resource exists amongrecreational divers that can be utilized toconduct video surveys of reefs. Many of thesedive groups visit reefs on a daily basis andhave an economic as well as a personal interest

382

in ensuring that reefs are protected. A focusof effort should be applied to train theseenthusiastic divers in proper survey tech­niques , water-quality sampling, and aware­ness of potential reef problems. Monitoringshould be conducted under the guidance ofprofessional scientists and in conjunction withstandard field-survey techniques for supple­mental data collection and quality control.Long-term monitoring of changes in species

PACIFIC SCIENCE,Volume 46, July 1992

abundance, diversity, and cover within andbetween reef communities will provide anecessary database from which to developimproved management decisions, and mayprovide an early warning system for possibledegradation of reef habitats. Community in­volvement in conducting such a research en­deavor will allow the public to "own" theresponsibility for fostering and protecting reefresources for generations to come.

Human Impact on Pacific Reefs Today: Priorities for Conservation in an Eraof Global Climate Change

S. M. WELLS2 6

Coral reefs in the Pacific region have comeunder increasing pressure in recent years fromimpacts associated with a variety of humanactivities. An overview of the major problemsis given. These may seem to be small scale inthe context of potential long-term changes onreefs from climate changes. Nevertheless, theymay be significant. Human-induced damageto reefs exacerbates damage caused by naturalevents such as hurricanes, predator outbreaks,and disease, and impairs regeneration. Reefs

2 6 56 Oxford Road , Cambridge, CB4 3PW, UnitedKingdom.

with lowered diversity , topography, and livingcover result in reduced fishery yields andpotentially reduced income from recreationalactivities. With many Pacific countries depen­dent on reef resources for subsistence orincome , and with the expansion of the touristindustry in this region , the importance ofmaintaining healthy reefs becomes self-evi­dent. Furthermore, healthy reefs may be ableto withstand the negative impact of globalwarming more successfully than reefs understress from other factors. Conservationpriorities in the region are discussed in thislong-term context.