Biogeography: A deep dive on reefs

A new analysis of the structure of coral-reef fish assemblages worldwide reveals biogeographic, taxonomic, and ecological patterns vary substantially with depth.

Global inequities between polluters and the polluted: climate change impacts on coral reefs

For many ecosystem services, it remains uncertain whether the impacts of climate change will be mostly negative or positive and how these changes will be geographically distributed. These unknowns hamper the identification of regional winners and losers, which can influence debate over climate policy. Here, we use coral reefs to explore the spatial variability of climate stress by modelling the ecological impacts of rising sea temperatures and ocean acidification, two important coral stressors associated with increasing greenhouse gas (GHG) emissions. We then combine these results with national per capita emissions to quantify inequities arising from the distribution of cause (CO2 emissions) and effect (stress upon reefs) among coral reef countries. We find pollution and coral stress are spatially decoupled, creating substantial inequity of impacts as a function of emissions. We then consider the implications of such inequity for international climate policy. Targets for GHG reductions are likely to be tied to a country's emissions. Yet within a given level of GHG emissions, our analysis reveals that some countries experience relatively high levels of impact and will likely experience greater financial cost in terms of lost ecosystem productivity and more extensive adaptation measures. We suggest countries so disadvantaged be given access to international adaptation funds proportionate with impacts to their ecosystem. We raise the idea that funds could be more equitably allocated by formally including a metric of equity within a vulnerability framework.

Transforming management of tropical coastal seas to cope with challenges of the 21st century

Over 1.3 billion people live on tropical coasts, primarily in developing countries. Many depend on adjacent coastal seas for food, and livelihoods. We show how trends in demography and in several local and global anthropogenic stressors are progressively degrading capacity of coastal waters to sustain these people. Far more effective approaches to environmental management are needed if the loss in provision of ecosystem goods and services is to be stemmed. We propose expanded use of marine spatial planning as a framework for more effective, pragmatic management based on ocean zones to accommodate conflicting uses. This would force the holistic, regional-scale reconciliation of food security, livelihoods, and conservation that is needed. Transforming how countries manage coastal resources will require major change in policy and politics, implemented with sufficient flexibility to accommodate societal variations. Achieving this change is a major challenge - one that affects the lives of one fifth of humanity.

The growing need for sustainable ecological management of marine communities of the Persian Gulf

The Persian Gulf is a semi-enclosed marine system surrounded by eight countries, many of which are experiencing substantial development. It is also a major center for the oil industry. The increasing array of anthropogenic disturbances may have substantial negative impacts on marine ecosystems, but this has received little attention until recently. We review the available literature on the Gulfs marine environment and detail our recent experience in the United Arab Emirates (U.A.E.) to evaluate the role of anthropogenic disturbance in this marine ecosystem. Extensive coastal development may now be the single most important anthropogenic stressor. We offer suggestions for how to build awareness of environmental risks of current practices, enhance regional capacity for coastal management, and build cooperative management of this important, shared marine system. An excellent opportunity exists for one or more of the bordering countries to initiate a bold and effective, long-term, international collaboration in environmental management for the Gulf.

Fish communities on the world's warmest reefs: what can they tell us about the effects of climate change in the future?

To examine the role of climatic extremes in structuring reef fish communities in the Arabian region, reef fish communities were visually surveyed at four sites within the southern Persian Gulf (also known as the Arabian Gulf and The Gulf), where sea-surface temperatures are extreme (range: 12-35° C annually), and these were compared with communities at four latitudinally similar sites in the biogeographically connected Gulf of Oman, where conditions are more moderate (range: 22-31° C annually). Although sites were relatively similar in the cover and composition of coral communities, substantial differences in the structure and composition of associated fish assemblages were apparent. Fish assemblages in the southern Persian Gulf held significantly lower estimates of abundance, richness and biomass, with significantly higher abundances of smaller sized individuals than Gulf of Oman assemblages. Functionally, southern Persian Gulf sites held significantly lower abundances of nearly all the common fish trophic guilds found on Gulf of Oman sites, although higher abundances of herbivorous grazers were apparent. These results suggest the potential for substantial changes in the structure of reef-associated fish communities, independent of changes in habitat within an environment of increasing fluctuations in oceanic climate.

Management of coral reefs: where we have gone wrong and what we can do about it

Globally, our current management of coral reefs is inadequate and becoming more so as we place new and greater stresses on these ecosystems. The future looks very dim, and yet we have the capacity to do a far more effective job of reef management if we want to. Making substantial improvements to the condition of these enormously valuable coastal marine ecosystems does not require new scientific discoveries, but a new commitment to apply the knowledge we already possess to manage our impacts so that sustainability becomes possible.

Coral reefs under rapid climate change and ocean acidification

Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2 degrees C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved. Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs increasingly toward the tipping point for functional collapse. This review presents future scenarios for coral reefs that predict increasingly serious consequences for reef-associated fisheries, tourism, coastal protection, and people. As the International Year of the Reef 2008 begins, scaled-up management intervention and decisive action on global emissions are required if the loss of coral-dominated ecosystems is to be avoided.

Critical science gaps impede use of no-take fishery reserves

As well as serving valuable biodiversity conservation roles, functioning no-take fishery reserves protect a portion of the fishery stock as insurance against future over-fishing. So long as there is adequate compliance by the fishing community, it is likely that they will also sustain and even enhance fishery yields in the surrounding area. However, there are significant gaps in scientific knowledge that must be filled if no-take reserves are to be used effectively as fishery management tools. Unfortunately, these gaps are being glossed over by some uncritical advocacy. Here, we review the science, identify the most crucial gaps, and suggest ways to fill them, so that a promising management tool can help meet the growing challenges faced by coastal marine fisheries.

Patterns and processes in reef fish diversity

A central aim of ecology is to explain the heterogeneous distribution of biodiversity on earth. As expectations of diversity loss grow, this understanding is also critical for effective management and conservation. Although explanations for biodiversity patterns are still a matter for intense debate, they have often been considered to be scale-dependent. At large geographical scales, biogeographers have suggested that variation in species richness results from factors such as area, temperature, environmental stability, and geological processes, among many others. From the species pools generated by these large-scale processes, community ecologists have suggested that local-scale assembly of communities is achieved through processes such as competition, predation, recruitment, disturbances and immigration. Here we analyse hypotheses on speciation and dispersal for reef fish from the Indian and Pacific oceans and show how dispersal from a major centre of origination can simultaneously account for both large-scale gradients in species richness and the structure of local communities.

Recruitment, loss and coexistence in a guild of territorial coral reef fishes

Eupomacentrus apicalis, Plectroglyphidodon lacrymatus, and Pomacentrus wardi are territorial pomacentrid fishes which occupy contiguous individual territories within rubble patches on the shallow reef slope. Loss of residents, which is non-seasonal (except for juvenile Po. wardi), results in reallocation of space in rubble patches among the species. This reallocation is random in the sense that sites previously held by one species will not be more likely than any other sites to be reoccupied by that species or to be occupied by any other particular species. The results of a 38 month study of three neighbouring patches are used to determine patterns of recruitment, survivorship, and loss for each species. The rate of recruitment of fish is proportional to the area of the rubble patch, and is seasonal in at least one of the species. About half the recruits are juveniles and young adults from other sites. The others are newly settled from the plankton. Total space used in a rubble patch does not vary significantly during the 38 month period. Po. wardi recruits and is lost at higher rates than the other species and its survivorship is significantly lower. Juvenile Po. wardi are lost at a greater rate than are adults, and their loss rate varies seasonally. The other species are similar to one another in having low recruitment and loss rates, and correspondingly high survivorship. The data are used in a critical assessment of several competing hypotheses to explain the coexistence of these fish. The available data are most closely compatible with the chance allocation or lottery hypothesis, but a definitive conclusion is not possible, and is probably beyond current experimental techniques.

Sexual Discrimination in the Siamese Fighting Fish (Betta Splendens Regan)

Abstract

I. We recorded the responses of male Betta splendens when presented with various stimuli behind a transparent partition. The stimuli comprised i) live male and female B. splendens; ii) lifelike (motionless) models of male and female B. splendens; and iii) six stylised model B. splendens. The stylised models consisted of three pairs, one member of which had long male-like fins and raised opercula, and the other with short female-like fins and lowered opercula. The first pair had "aggressive", the second, "submissive", and the third, "reproductive" colouration. 2. The use of two techniques for comparing responses to the different stimuli was compared. Principal component analysis of unscaled data produced more satisfactory results than did clustering by single linkage on the basis of taxonomic distances calculated on scaled data. 3. The response by a male to a stimulus consisted of two categories of behaviour: "agonistic" display and nest-oriented activities. 4. The responses towards live males and females differed only in the relative amounts of "agonistic" and nest-oriented behaviour performed to each. A greater amount of "agonistic" behaviour was performed towards males. 5. Three main influences were found affecting a male's response to a conspecific: i) a tendency to perform all components of "agonistic" display and to inhibit performance of nest-oriented behaviour; ii) and iii) tendencies to perform particular components of the "agonistic" display. Thus the "agonistic" display was found to be complex and governed by at least three separate motivations. 6. The first influence varied according to the (perceived) sex of the stimulus, being great when the stimulus was a male, and slight when it was a female. The other two influences were independent of the nature of the stimulus. 7. Responses to lifelike, motionless models were very similar to those to live fish. 8. All male models and the "aggressive" female model were treated similarly to the live male. The other models were treated similarly to the live female. 9. A mechanism for sexual discrimination was proposed, in which a male is characterised by long fins and/or raised opercula, or, an unpatterned body. A female is characterised by short fins and a patterned body. Discrimination can be accomplished solely by use of visual stimuli.

A Suggested Mechanism for Habitat Selection By the Juvenile Manini Acanthurus Triostegus Sandvicensis Streets

Abstract

The Hawaiian manini, Acanthurus triostegus sandvicensis Streets, shows a continuing selection of habitat throughout juvenile life, and the selected habitat changes in character as the fish grows in size. Habitat selection of this kind is a complex type of choice behaviour in which the animal makes a selection from a number of (at least partly) configurational stimulus situations experienced separately over time. This sort of behaviour cannot be satisfactorily explained by reference to concepts of taxes or kineses. A mechanism is proposed to explain this process. It suggests that intensity of habitat exploration is regulated through a negative feedback mechanism by the character of the immediate environment with respect to the pertinent stimuli. A fish in an inadequate environment will show a high intensity of habitat exploration. One in an adequate environment will show a much reduced level of exploration. Twenty manini were exposed singly to four test environments of known relative value as habitats. Each fish received all four, and order of exposure was randomised. Analysis of thirteen components of behaviour showed that exploration did vary in the manner predicted. A control experiment showed that the nature of the holding environment prior to testing did not influence this variation. The variation in exploration was not a response to relative novelty of the test environments. The proposed mechanism is discussed as a general behaviour pattern. It seems an applicable approach to the study of habitat selection in other organisms.

A RE-EXAMINATION OF THE TAXONOMIC POSITION OF THE AURORA TROUT

Results of a field study are used in considering the taxonomic position of the aurora trout. Coloration and morphology of aurora and brook trout are compared. There are at best only minor differences—in some aspects of coloration, in epidermal thickness, and in behavior—between these fish. These differences are genetically controlled. Aurora trout fill the brook trout niche in lakes which they inhabit. Characteristics of the home range lakes are given. Aurora and brook trout are fully interfertile, but reproductively isolated sympatric populations existed in one lake. It is suggested that the aurora trout is a race of the brook trout worthy of nomenclatural recognition as a subspecies, and that it should be classified as Salvelinus fontinalis timagamiensis Henn and Rickenbach.