The need for conservation and management of Philippine coral reefs

Synopsis The biological diversity and productivity of Philippine coral reefs are threatened by siltation, destructive fishing methods, coral and shell collecting and overfishing. Destructive fishing includes: the widespread, illegal use of explosives; poisons such as sodium cyanide; muro-ami and kayakas fishing; and trawling. The recent decline in catch rates threatens the livelihood of 700 000 near-shore subsistence fishermen who catch 55% of the total landings. The new government under Corazon Aquino wishes to protect the marine environment through the creation of a viable marine conservation management plan, enforcement of existing laws and through cooperation between government, non-government and international agencies to provide education and research. The Department of Agriculture, which has the authority for fisheries, has designated the International Marinelife Alliance as the lead non-government agency involved with fund raising, net-training and finding alternatives to destructive fishing methods.This essay addresses the societal relationships of village fishery to government, aid organizations, and science. Vadim Vladykov always maintained close relationship with fishermen and devoted over a year of his life to helping develop fisheries in Iran.     

Black reefs: iron-induced phase shifts on coral reefs

The Line Islands are calcium carbonate coral reef platforms located in iron-poor regions of the central Pacific. Natural terrestrial run-off of iron is non-existent and aerial deposition is extremely low. However, a number of ship groundings have occurred on these atolls. The reefs surrounding the shipwreck debris are characterized by high benthic cover of turf algae, macroalgae, cyanobacterial mats and corallimorphs, as well as particulate-laden, cloudy water. These sites also have very low coral and crustose coralline algal cover and are call black reefs because of the dark-colored benthic community and reduced clarity of the overlying water column. Here we use a combination of benthic surveys, chemistry, metagenomics and microcosms to investigate if and how shipwrecks initiate and maintain black reefs. Comparative surveys show that the live coral cover was reduced from 40 to 60% to <10% on black reefs on Millennium, Tabuaeran and Kingman. These three sites are relatively large (>0.75 km²). The phase shift occurs rapidly; the Kingman black reef formed within 3 years of the ship grounding. Iron concentrations in algae tissue from the Millennium black reef site were six times higher than in algae collected from reference sites. Metagenomic sequencing of the Millennium Atoll black reef-associated microbial community was enriched in iron-associated virulence genes and known pathogens. Microcosm experiments showed that corals were killed by black reef rubble through microbial activity. Together these results demonstrate that shipwrecks and their associated iron pose significant threats to coral reefs in iron-limited regions.     

Marine pollution and coral reefs

Coral reefs are exposed to many anthropogenic stresses increasing in impact and range, both on local and regional scales. The main ones discussed here are nutrient enrichment, sewage disposal, sedimentation, oil-related pollution, metals and thermal pollution. The stress comprising the main topic of this article, eutrophication, is examined from the point of view of its physiological and ecological mechanisms of action, on a number of levels. Nutrient enrichment can introduce an imbalance in the exchange of nutrients between the zooxanthellae and the host coral, it reduces light penetration to the reef due to nutrient- stimulated phytoplankton growth, and, most harmful of all, may bring about proliferation of seaweeds. The latter rapidly outgrow, smother and eventually replace, the slow-growing coral reef, adapted to cope with the low nutrient concentrations typical in tropical seas.
Eutrophication seldom takes place by itself. Sewage disposal invariably results in nutrient enrichment, but it also enriches the water with organic matter which stimulates proliferation of oxygen-consuming microbes. These may kill corals and other reef organisms, either directly by anoxia, or by related hydrogen sulfide production. Increased sediment deposition is in many cases associated with other human activities leading to eutrophication, such as deforestation and topsoil erosion.
Realistically achievable goals to ensure conservation, and in some instances, rehabilitation of coral reefs are listed.     

Taphonomy of coral reefs: a review

This review summarises the major factors that affect the post-mortem history of skeletons in a coral reef environment. Skeletal material is traced from life, through death, breakdown, transport, burial and diagenesis to its final fossil form. The fact that most reef sediments are of skeletal composition poses problems of concentration or dilution of individual grain types in taphonomic analysis of reefs. Rates of supply of grains vary, not only with organism abundance and skeletal growth rates, but also with rates of physical and biological breakdown to transportable sediment. Physical and organic processes affect sedimentary structures and textures by mixing or segregating skeletal grains, though biogenic processes normally dominate in the protected setting of reef lagoons. The soft and hard substrates associated with reefs present different media for calcium carbonate accumulation and post-depositional disturbance, for example, loose sediments suffer bioturbation and rocks surfaces suffer bioerosion. The wide range of durability of skeletons and their susceptibility to diagenesis contribute further to the complexities of the preservation of coral reefs.     

Atlantic coral reefs: the transplantation alternative

Although all of the world’s coral reef regions have suffered degradation due to direct and indirect human influences, only the Western Atlantic reefs have declined to the extent that their continued existence appears to be in jeopardy. Of a once flourishing reef system, only about 10% is still alive and it is depauperate in terms of the food web diversity necessary to maintain a stable and productive ecosystem. The large carnivores and herbivores have become so scarce that they have failed to control the populations of smaller animals and plants, so that almost all the trophic levels have been disrupted. At the same time, the impacts of many other factors have contributed to the process of degradation resulting in a true crisis. The extent of damage, and the general impairment of regeneration, is such that a hope for natural recovery appears to be unrealistic. It is suggested that a recovery could be achieved through transplantation of corals and other reef species from areas where more diverse, relatively stable ecosystems still exist. Available data on the introduction of exotic species into marine ecosystems indicate that such species are generally accommodated and do not cause extinctions among the native species. Although some introduced species are considered to be pests, others have proved to be beneficial, and all have apparently increased the biodiversity of the invaded areas.     

Biological destruction of coral reefs

The major agents of biological destruction of coral reefs can be divided into grazers, etchers and borers. Each of these groups is reviewed on a world wide basis, together with the mechanisms by which they destroy the coral substrate. Rates of bioerosion attributed to major agents of grazers, etchers and borers are given, together with limitations of some of the measurements. Recent work is highlighting the variability in rates of bioerosion both over time and space. Factors which may be responsible for this variability are discussed. Bioerosion is a major factor influencing reef morphology and the ways in which this is achieved is discussed in some detail. Although the review concentrates mainly on present day reefs, some attempt is made to consider the impact of bioerosion on older reefs.     

Integrating connectivity science and spatial conservation management of coral reefs in north-west Australia

The geographically isolated, environmentally unique and biologically diverse coral reefs of north-west Australia are under threat from climate change and other localised human impacts. Similar to many other regions around the world, effective mitigation of these threats through ecosystem-based marine spatial planning is currently constrained by a lack of knowledge of the extent and direction of dispersal of eggs, larvae, recruits, juveniles or adults among the coral reefs (termed population connectivity). Here, we present the outcomes of a series of consultations between Marine Protected Area planners, managers and scientists aimed at facilitating the integration of this connectivity knowledge into effective management guidelines and policy in north-west Australia. Through this process, we first synthesised current knowledge of population connectivity in the fields of oceanography, larval biology and population genetics, and then identified and answered to the best of our ability the most useful questions for the spatial planning of Marine Protected Area networks. Key findings indicate that these systems are likely ecologically independent for many coral reef organisms, with hard corals exhibiting the most localised dispersal of species studied so far. Thus, given that hard corals are also the habitat forming species, and that more widely dispersing species such as fish are likely less vulnerable to small scale disturbance, we propose that no-take areas that facilitate resilience of hard coral populations should maximise biodiversity more generally. This means no-take areas that are large enough to encompass routine dispersal distances of corals (10–20 km), and are spaced at similar distances, will not only maintain self-replenishment, but also aid recovery after disturbance through connectivity between no-take areas. The results can be applied in a regional and wider context, and provide a valuable template for transfer of scientific knowledge into effective policy.     

Summit-to-sea mapping and change detection using satellite imagery: tools for conservation and management of coral reefs

Continuous summit-to-sea maps showing both land features and shallow-water coral reefs have been completed in Puerto Rico and the U.S. Virgin Islands, using circa 2000 Landsat 7 Enhanced Thematic Mapper (ETM+) Imagery. Continuous land/sea terrain was mapped by merging Digital Elevation Models (DEM) with satellite-derived bathymetry. Benthic habitat characterizations were created by unsupervised classifications of Landsat imagery clustered using field data, and produced maps with an estimated overall accuracy of>75% (Tau coefficient >0.65). These were merged with Geocover-LC (land use/land cover) data to create continuous land/ sea cover maps. Image pairs from different dates were analyzed using Principle Components Analysis (PCA) in order to detect areas of change in the marine environment over two different time intervals: 2000 to 2001, and 1991 to 2003. This activity demonstrates the capabilities of Landsat imagery to produce continuous summit-to-sea maps, as well as detect certain changes in the shallow-water marine environment, providing a valuable tool for efficient coastal zone monitoring and effective management and conservation.     

Customary management as precautionary and adaptive principles for protecting coral reefs in Oceania

Marine conservation programs in Oceania are increasingly turning to precautionary and adaptive management, particularly approaches which emphasize local participation and customary management. Although the application of community-based natural resource management is widespread in the region, the full integration of local knowledge and practices into the design, implementation, and monitoring of community-based conservation programs has been limited. There is also little empirical data to show whether or not community-based conservation projects are meeting their stated objectives. This paper summarizes an integrated method for selecting Marine Protected Area (MPA) sites and presents empirical evidence that illustrates how an MPA that was largely conceived using indigenous ecological knowledge and existing sea tenure governance (i.e., customary management practices), as part of a regional precautionary and adaptive community-based management plan, is showing signs of biological and social success. More generally, the paper shows how hybrid natural and social research approaches in tandem with customary management for designing MPAs can protect coral reefs in Oceania.     

Allozyme electrophoresis still represents a powerful technique in the management of coral reefs

Understanding genetic variability and gene flow between populations of scleractinian corals separated by one to several hundred kilometers is crucially important as we head into a century of climate change in which an understanding of the connectivity of populations is a critically important question in management. Genetic methods that directly use molecular variance in the DNA should offer greater precision in detecting differences among individuals and populations than the more traditional allozyme electrophoresis. However, this paper highlights the point that the limited number of DNA markers that have been identified for scleractinian coral genetic studies do not necessarily offer greater precision than that offered by allozymes. In fact, at present allozyme electrophoresis yields greater information than the eight different DNA markers used in this study. Given the relative ease of use of allozymes and the wealth of comparable data sets from numerous previously published studies, allozyme electrophoresis should not be dismissed for population structure and connectivity studies on coral reefs. While continued effort should be placed into searching for new DNA markers, until a more sensitive DNA marker becomes available for scleractinian corals, allozyme electrophoresis remains a powerful and relevant technique for understanding the connectivity of coral population studies.     

Biology and geology of eastern Pacific coral reefs

Coral Reefs -  The tropical eastern Pacific region has historically been characterized as devoid of coral reefs. The physical conditions of the region are apparently not conducive to reef...     

Facilitation in Caribbean coral reefs: high densities of staghorn coral foster greater coral condition and reef fish composition

Recovery of the threatened staghorn coral (Acropora cervicornis) is posited to play a key role in Caribbean reef resilience. At four Caribbean locations (including one restored and three extant populations), we quantified characteristics of contemporary staghorn coral across increasing conspecific densities, and investigated a hypothesis of facilitation between staghorn coral and reef fishes. High staghorn densities in the Dry Tortugas exhibited significantly less partial mortality, higher branch growth, and supported greater fish abundances compared to lower densities within the same population. In contrast, partial mortality, branch growth, and fish community composition did not vary with staghorn density at the three other study locations where staghorn densities were lower overall. This suggests that density-dependent effects between the coral and fish community may only manifest at high staghorn densities. We then evaluated one facilitative mechanism for such density-dependence, whereby abundant fishes sheltering in dense staghorn aggregations deliver nutrients back to the coral, fueling faster coral growth, thereby creating more fish habitat. Indeed, dense staghorn aggregations within the Dry Tortugas exhibited significantly higher growth rates, tissue nitrogen, and zooxanthellae densities than sparse aggregations. Similarly, higher tissue nitrogen was induced in a macroalgae bioassay outplanted into the same dense and sparse aggregations, confirming greater bioavailability of nutrients at high staghorn densities. Our findings inform staghorn restoration efforts, suggesting that the most effective targets may be higher coral densities than previously thought. These coral-dense aggregations may reap the benefits of positive facilitation between the staghorn and fish community, favoring the growth and survivorship of this threatened species.     

Hurricanes and coral reefs: The intermediate disturbance hypothesis revisited

A review of research on the effects of hurricanes on coral reefs suggests that the intermediate disturbance hypothesis may be applicable to shallow reef zones dominated by branching or foliaceous coral species that are especially susceptible to mechanical damage from storms. Diversity (H') increases because of an increase in evenness following destruction or removal of the species that was monopolizing the space. The intermediate disturbance hypothesis as presented by Connell focuses on changes in number of species, but should be expanded to include diversity (H') and evenness. It should also be modified to incorporate changes in living cover and the time elapsed since disturbances of varying intensities. This hypothesis predicts that when cover is high, diversity will be low. However, research on coral reefs does not consistently demonstrate an inverse correlation of coral diversity, and coral cover. An increase in cover and decrease in diversity with depth would also be expected because deeper reef zones generally experience less disturbance. However, higher diversity (both H' and species richness) is often associated with deeper zones. The effects of hurricanes on coral reefs will depend on the temporal and spatial scales under consideration, the life history characteristics and morphology of the dominant species, the depth of the reef zone, the ecological history of the site, and the influence of any additional natural or human stresses.