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General (Natural)

1 . Global (2004)
GLOBAL THREATS TO CORAL REEFS

  • Many coral reefs continue to recover after the 1998 El Niño/La Niña global coral bleaching event, with stronger recovery in well-managed and remote reefs; however, the recovery is not uniform and many reefs virtually destroyed in 1998 show minimal signs of recovery. This recovery could be reversed if the predicted increases in ocean temperatures occur as a result of increasing global climate change;

  • There has been no recurrence of the major global-scale climate change pressures of 1998; although there have been some more localised bleaching events in 2000 and 2003 causing damage to reefs;

  • The coral bleaching in 1998 was a 1 in a 1000-year event in many regions with no past history of such damage in official government records or in the memories of traditional cultures of the affected coral reef countries. Also very old corals around 1000 years old died during 1998. Increasing sea surface temperatures and CO2 concentrations provide clear evidence of global climate change in the tropics, and current predictions are that the extreme events of 1998 will become more common in the next 50 years, i.e. massive global bleaching mortality will not be a 1/1000 year event in the future, but a regular event;

  • Coral disease and major coral predators like the crown-of-thorns starfish continue to threaten reefs and evidence points to human disturbance as a contributing and catalytic factor behind these increases.
  • Source: Wilkinson, C. , 2004 , Foreword, Countries, States and Territories Acknowledgements, Co-sponsors and supporters of GCRMN, Introduction and Executive Summary. . p: I-66. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

    Diseases

    2 . Global (2004)
    DISEASES, PLAGUES AND INVASIVES


    The other major global threat to coral reefs is through an apparent proliferation of coral reef diseases and plagues of destructive organisms. The major worrying feature is the very strong suspicion and apparent close correlation that the increased incidence and severity of these threats is directly linked to damaging human activities, whether through pollution washing off the land, heat stress to corals, or through over-.fishing of the organisms that can control plagues.

    Coral diseases are now known to affect more than 150 species of Caribbean and Indo-Pacific corals; and new diseases are being added to the 29 described diseases. Diseases have caused more damage to the coral reefs of the wider Caribbean, than the Indo-Pacific region. The recent increases in marine diseases worldwide emphasizes the need for more research and also points to potential linkages to other stresses on the corals as possible instigators of disease.
    Source: Wilkinson, C. , 2004 , Foreword, Countries, States and Territories Acknowledgements, Co-sponsors and supporters of GCRMN, Introduction and Executive Summary. . p: I-66. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

    Biological infestations

    3 . Global (2004)
    It is apparent that plagues of predators, such as COTS, are increasingly reported around areas of human activities with the possibility that either the plagues are initiated or exacerbated by over-fishing; and/or increases in nutrients from the land favour the planktonic stages of the starfish. Unfortunately, definitive explanations for the outbreaks do not exist after decades of intensive research. There have been widespread, large-scale losses of coral cover and biodiversity on many reefs and these plagues can be added as another large-scale threat to the integrity of coral reefs. The highest densities of COTS in recent years have been in Tanzania, Kenya and on the GBR.

    The potential threats from invasive species have largely been ignored until recently. While there is the likelihood that such invasives could disrupt the ecological balance of coral reefs, there is little evidence of significant deleterious effects on ecosystem processes or biodiversity. The most serious incidence was the suspected introduction through the Panama Canal of a disease that killed the sea urchin, Diadema antillarum, in the Caribbean in the early 1980s. There is now evidence of invasive species causing damage in Hawaii and parts of the Caribbean. The most likely causes of invasive introductions are through ballast-water or the hulls of cargo ships, or through the release of aquarium specimens in the wrong habitat.
    Source: Wilkinson, C. , 2004 , Foreword, Countries, States and Territories Acknowledgements, Co-sponsors and supporters of GCRMN, Introduction and Executive Summary. . p: I-66. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

    Diseases

    4 . Global (2004)
    CORAL AND OTHER DISEASES

    There has been a worldwide increase in reports of diseases of marine organisms including fish, sea urchins, shellfish, sponges, marine mammals, and especially corals. Since the 1990s, coral diseases have increased in number, affected species, and geographic range, with diseases affecting over 150 species from the Caribbean and Indo-Pacific alone. The rate of discovery of new diseases has also increased considerably, with more than 29 coral diseases now described. Coral diseases can potentially produce severe population declines, threaten biodiversity, and shift the structure of reef communities by challenging the resilience of these systems. This has been emphasised in the wider Caribbean when several outbreaks of coral diseases resulted in massive losses in corals, particularly the dominant reef builders the Acropora species in 1970s and 90s.

    Although coral disease is emerging as a major threat to Caribbean coral reef health, we currently know very little about the ecology or pathology of coral disease on Indo-Pacific reefs, despite the region encompassing more than 80% of reefs worldwide. The relatively few reports of coral disease from Indo-Pacific reefs suggest that either disease is genuinely more prevalent in the Caribbean or a lack of research in other regions is underestimating influence and severity. The rising incidence of marine diseases worldwide in the past few decades emphasises the need for increased assessment of the status of disease in order to identify the origins and reservoirs of pathogens and the vectors involved in disease transmission (from Bette Willis, bette.willis@jcu.edu.au).

    Stress appears to lower a coral’s resistance to disease and thus affects its ability to survive. Because elevated temperature is a coral stress, increasing predictions of global climate change may also result in increasing incidence of coral disease. It is possible that proximity to human population centres may increase the likelihood of infection. Disease outbreaks are nearly impossible to manage because the connectivity of the marine environment increases the speed of disease transmission and renders standard response such as quarantine and vaccines ineffective. Preventing nutrient runoff into coastal areas by managing water quality could be an important measure and the relationship between increased nutrients and disease severity
    should be viewed as a top priority for ecologists and resource managers.
    Source: Goldberg, J. and C. Wilkinson , 2004 , Global Threats to Coral Reefs: Coral Bleaching, Global Climate Change, Disease, Predator Plagues, and Invasive Species. . p: 67-92. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

    Alien species

    5 . Global (2004)
    INVASIVE SPECIES

    Invasions of non-native species in marine ecosystems can be ecologically damaging as well as economically costly should they become established into their new habitats. Although invasive species introductions have been documented on coral reefs, there have been no incidences of deleterious effects or other significant negative impacts on ecosystem processes or biodiversity. The most likely causes of invasive species introductions are:

  • the necessary ballast-water exchange for cargo ships traveling long distances between ports releasing gametes, larvae, or juvenile individuals into new systems; and

  • aquaria related incidents whereby individuals import specimens from all over the world and release them into the wild after a time in captivity.

    With increasing global trade and exportation of marine aquaria species around the world, caution must be taken in coming years to monitor these introductions and to act as soon as they are observed in order to prevent economic and environmental consequences similar to those documented in freshwater and terrestrial systems. Prevention is undoubtedly the best management strategy and anticipation of further releases and subsequent nvasions resulting from marine aquarists and the aquarium industry requires education, community outreach, and enforcement efforts. One potentially useful solution involves identification of ‘hot-spots’ of non-native species and their sources of introduction which can maximize the effectiveness of
    invasion quarantine programs.

    Since Indo-Pacific live rock is exported widely and there are live reef tank enthusiasts at low as well as high latitudes, the risk of introduction of Pacific organisms to the tropical Atlantic is high. If fishes can do it, and they have, certainly invertebrates can.
    Source: Goldberg, J. and C. Wilkinson , 2004 , Global Threats to Coral Reefs: Coral Bleaching, Global Climate Change, Disease, Predator Plagues, and Invasive Species. . p: 67-92. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

    Biological infestations

    6 . Eastern Africa (2002)
    In December 2001-February 2002, a number of medium to large-scale Harmful Algal Blooms (HAB) impacted the northen coasts of East Africa, in Somalia, Kenya and Tanzania, as well as being reported in the Gulf of Aden, in Oman and Yemen (Table 2). The largest blooms appeared to impact Oman and Yemen, and Somalia and Kenya, in January-February 2002. Sampling of waters in the last stages of the Somali-Kenya bloom enabled identification of the toxic alga as Karenia mikimoto (formerly variously known as Gymnodinium nagasakiense and G. aureolum) by G. Pitcher (South Africa). The event coincided with stronger than normal upwelling in the Somali Current system and stronger onshore winds of the northeast monsoon, resulting in high phytoplankton concentrations onshore in southern Somalia and northern Kenya (D. Robins,Table 2 ) This coincidence of events may have caused the bloom, but to now no cause has been confirmed.

    Extensive fish kills were reported for both blooms, including surgeon fish, parrot fish, snappers, puffers, triggerfish, eels, rays and more. The blooms were also associated with changes in billfish and tuna distributions. Human health effects were reported but unconfirmed, including stinging eyes and sore throats, but mortalities were not confirmed. As a precaution, however, reef fisheries were halted in northern Kenya for 3 weeks, with considerable economic consequences to families in the region.
    Source: Obura, D. , 2002 , Status of Coral Reefs in East Africa. . in Linden, O., D. Souter, D. Wilhelmsson, and D. Obura (eds.). Coral degradation in the Indian Ocean: Status Report 2002. CORDIO, Department of Biology and Environmental Science, University of Kalmar, Kalmar, Sweden.pp 15-20 (See Document)

    Diseases

    7 . Eastern Africa (2002)
    Shortly after the HAB dissipated in Kenya, an unknown coral disease was first reported in northern Kenya, and subsequently observed in southern Kenya and northern Tanzania (Table 2). The disease primarily impacted the genera Montipora, Astreopora and Echinopora, in some aras causing near 100% mortality (Obura, this volume). Many other coral genera were affected but to a lesser extent and more variably among regions, including Pocillopora, Acropora and Platygyra. The disease was subsequently identified by electron microscopy as a fungus (T. McClanahan, pers.comm.), though of unknown identity.
    Source: Obura, D. , 2002 , Status of Coral Reefs in East Africa. . in Linden, O., D. Souter, D. Wilhelmsson, and D. Obura (eds.). Coral degradation in the Indian Ocean: Status Report 2002. CORDIO, Department of Biology and Environmental Science, University of Kalmar, Kalmar, Sweden.pp 15-20 (See Document)

    General (Natural)

    8 . Southwest Indian Ocean (2004)
    The natural threats include cyclones (cyclone period November – February), coral bleaching (occurring during the warmest months from February to April) and COTS outbreaks that occur very rarely.
    Source: Ahamada, S., J. Bijoux, L. Bigot, B. Cauvin, M. Kooonjul, J. Maharavo, S. Meunier, M. Moine-Picard, J.-P. Quod and R. Pierre-Louis , 2004 , Status of the Coral Reefs of the South West Indian Ocean Island States. . p: 189-212. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

    Diseases

    9 . Pacific (2005)
    Johnston Atoll

    In January 2004, surveys were conducted at 12 sites at Johnston Atoll to quantify and characterize coral disease. Surveys were limited to sites within the lagoon due to harsh weather conditions. Signs of coral disease were evident at 92% of the sites surveyed. The average prevalence of disease (no. of diseased colonies/total no. of colonies) was estimated at 3.1%, which is higher than what has been reported for the NWHI (average estimated prevalence=0.5%; Aeby, NWHI chapter). Types of diseases included growth anomalies on Acropora and Montipora, white syndrome on the table coral, Acropora cytherea, Montipora tissue loss syndrome, and Montipora patchy tissue loss. These diseases have also been observed in the NWHI. One disease that has not yet been found in the NWHI was Montipora ring syndrome, where affected corals have abnormal growths with tissue death in the center producing a ring-like lesion (Figure 12.3). Work etal. (2001) found similar disease signs at Johnston Atoll during a qualitative assessment of coral disease.

    Howland and Baker Islands

    A qualitative assessment of coral disease was conducted at six sites around Howland Island and six sites around Baker Island during January 2004. The corals were found to be in good condition with few colonies having any signs of disease. Small patches of denuded skeleton were frequently observed on acroporids and seemed to be associated with damselfish (Plectroglyphididon sp.) activities.
    Source: Brainard, R., J. Maragos, R. Schroeder, J. Kenyon, P. Vroom, S. Godwin, R. Hoeke, G. Aeby, R. Moffitt, M. Lammers, J. Gove, M.Timmers, S. Holzwarth, and S. Kolinski , 2005 , The State of Coral Reef Ecosystems of the Pacific Remote Island Areas. . p.338-372 in Waddell, J. (ed.), 2005. The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005. NOAA Technical Memorandum NOS NCCOS 11. NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team. Silver Spring, MD. 522 pp. (See Document)

    Alien species

    10 . Pacific (2005)
    Aquatic Invasive Species

    The efforts by the PIFSC-CRED and the USFWS sponsored Pacific Biological Survey performed by the Bishop Museum, both based in Hawaii, have provided information concerning marine alien species in the PRIAs. Documentation of marine alien species occurred through regular survey and monitoring activities by the PIFSC-CRED in 2002 and 2004. These surveys involved 27 sites at the U.S. Phoenix Islands, 33 sites at the U.S. Line Islands, and 12 at Johnston Atoll. An intensive inventory focusing on marine alien species was conducted at 11 sites at Johnston Atoll by the Bishop Museum.

    Compiled data from these efforts reveal that marine alien species exist in these remote islands and that 85% are at either Johnston or Palmyra Atoll. Both of these sites were active military installations with many of the alien species reaching the atolls via the hulls and ballast waters of arriving vessels. These two remote atolls have experienced the greatest physical alteration historically and the majority of alien species documented are associated with these altered habitats. A compiled list from the combined efforts is provided in Table 12.1, including species name, native range (if determined) and a status of either alien or cryptogenic. The cryptogenic term refers to species of unknown status that are most likely introduced. Comparable data for Wake Island, an active military base, are not available.

    Marine alien species in these remote areas have just recently become an issue of interest, due to survey efforts in other parts of the tropical Pacific. Efforts should be focused on minimizing the likelihood of coral reef habitats being exposed to marine alien species through the spread of organisms already established in altered habitats and transport of new species from outside of the PRIAs. This can be achieved by management efforts
    directed towards all activities that have the potential for acting as mechanisms of transport, especially visiting ships and airplanes as well as the shoes and clothing of visitors.
    Source: Brainard, R., J. Maragos, R. Schroeder, J. Kenyon, P. Vroom, S. Godwin, R. Hoeke, G. Aeby, R. Moffitt, M. Lammers, J. Gove, M.Timmers, S. Holzwarth, and S. Kolinski , 2005 , The State of Coral Reef Ecosystems of the Pacific Remote Island Areas. . p.338-372 in Waddell, J. (ed.), 2005. The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005. NOAA Technical Memorandum NOS NCCOS 11. NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team. Silver Spring, MD. 522 pp. (See Document)

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