Structural complexity mediates functional structure of reef fish assemblages among coral habitats

Coral community composition varies considerably due to both environmental conditions and disturbance histories. However, the extent to which coral composition influences associated fish assemblages remains largely unknown. Here an ecological trait-based ordination analysis was used to compare functional richness (range of unique trait combinations), functional evenness (weighted distribution of fishes with shared traits), and functional divergence (proportion of total abundance supported by species with traits on the periphery of functional space) of fish assemblages among six distinct coral habitats. Despite no significant variation in species richness among habitats, there were differences in the functional richness and functional divergence, but not functional evenness, of fish assemblages among habitats. Structural complexity of coral assemblages was the best predictor of the differences in functional richness and divergence among habitats. Functional richness of fish assemblages was highest in branching Porites habitats, lowest in Pocillopora and soft coral habitats, and intermediate in massive Porites, staghorn Acropora, and mixed coral habitats. Massive and branching Porites habitats displayed greater functional divergence in fish assemblages than the Pocillopora habitat, whilst the remaining habitats were intermediate. Differences in functional richness and divergence were largely driven by the presence of small schooling planktivores in the massive and branching Porites habitats. These results indicate that differential structural complexity among coral communities may act as an environmental filter, affecting the distribution and abundance of associated species traits, particularly those of small-bodied schooling fishes

Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes

Copyright: © 2011 Mora et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas

Variation in calcification rate of Acropora downingi relative to seasonal changes in environmental conditions in the northeastern Persian Gulf

There is a strong interest in understanding how coral calcification varies with changing environmental conditions, especially given the projected changes in temperature and aragonite saturation due to climate change. This study explores in situ variation in calcification rates of Acropora downingi in the northeastern Persian Gulf relative to seasonal changes in temperature, irradiance and aragonite saturation state (Xarag). Calcification rates of A. downingi were highest in the spring and lowest in the winter, and intra-annual variation in calcification rate was significantly related to temperature (r2 = 0.30) and irradiance (r2 = 0.36), but not Xarag (r2 = 0.02). Seasonal differences in temperature are obviously confounded by differences in other environmental conditions and vice versa. Therefore, we used published relationships from experimental studies to establish which environmental parameter(s) (temperature, irradiance, and/or Xarag) placed greatest constraints on calcification rate (relative to the maximum spring rate) in each season. Variation in calcification rates was largely attributable to seasonal changes in irradiance and temperature (possibly *57.4 and 39.7% respectively). Therefore, we predict that ocean warming may lead to increased rates of calcification during winter, but decelerate calcification during spring, fall and especially summer, resulting in net deceleration of calcification for A. downingi in the Persian Gulf

Avoiding conflicts and protecting coral reefs: Customary management benefits marine habitats and fish biomass

One of the major goals of coral reef conservation is to determine the most effective means of managing marine resources in regions where economic conditions often limit the options available. For example, no-take fishing areas can be impractical in regions where people rely heavily on reef fish for food. In this study, we test whether coral reef health differed among areas with varying management practices and socioeconomic conditions on Pulau Weh, in the Indonesia province of Aceh. Our results show that gear restrictions, in particular, prohibiting the use of nets, were remarkably successful in minimizing habitat degradation and maintaining fish biomass despite ongoing access to the fishery. Reef fish biomass and hard-coral cover were two to eight-fold higher at sites where fishing nets were prohibited. Most interestingly, the guiding principle of the local customary management system, Panglima Laot, is to reduce conflict among community members over access to marine resources. Consequently, conservation benefits in Aceh have arisen from a customary system which lacks a specific environmental ethic or the means for strong resource based management. Panglima Laot includes many of the features of successful institutions, such as clearly defined membership rights and the opportunity of resource users to be involved in making, enforcing, and changing the rules. Such mechanisms to reduce conflict are the key to success of marine resource management, particularly, in settings which lack resources for enforcement

Disturbance to coral reefs in Aceh, Northern Sumatra: impacts of the Sumatra-Andaman tsunami and pre-tsunami degradation

The Sumatra-Andaman tsunami of 26 December 2004 was the first to occur in areas for which good ecological data existed prior to the event and consequently provided\ud a unique opportunity to assess the effects of this type of natural disturbance in tropical marine ecosystems. Less than 100 days after the event we visited 49 sites on coral reefs\ud in northern Aceh, Indonesia, all within 300 km of the epicentre, to determine the nature and extent of tsunami damage and pre-tsunami disturbance. Reef fish diversity and\ud abundance were also assessed in relation to tsunami impact and existing marine resource management regulations. At these sites, the initial damage to corals, while occasionally spectacular, was surprisingly limited and trivial when compared to pre-existing damage most probably caused by destructive fishing practices. The abundance of up-turned corals was highly dependent on habitat and largely restricted to corals growing in unconsolidated substrata at depth, a feature we believe unique to tsunami disturbance.\ud Other evidence of tsunami damage, including the abundance of broken corals and recently killed corals was patchy and varied unpredictably between sites: reef aspect, geographic location and management regime had no significant effect on these variables with the exception of broken live corals which were more abundant at locations where the tsunami was larger. Interestingly, there was little correlation between damage variables, suggesting the type of damage observed was strongly influenced by which corals were present at a particular site or depth. In contrast, reef condition was clearly correlated with the management regime. Coral cover was on average 2-3 times higher on reefs managed under the traditional Acehnese system, Panglima Laut, and in the Pulau Rubiah Marine Park when compared to open access areas. Turf algae and coral rubble were 2-3 times more abundant in open access sites compared with managed areas. These results are\ud consistent with a history of destructive fishing practices, such as bombing and cyanide fishing in open access areas. Coral reef fish abundance and diversity did not differ among\ud management zones, despite the fact that Pulau Rubiah Marine Park has been closed to fishing for 10 years. However, there were consistent differences in the structure of the reef fish assemblages among these zones. For example, the near absence of chaetodontids at open access sites is probably the result of low coral cover. The high abundance of\ud scarids and acanthurids in the Marine Park, suggests that while management efforts have failed to allow fish to increase in abundance, they have been effective at protecting certain species. The tsunami had no detectable affect on reef fish assemblages at these sites. This lack of major damage means that neither the conservation priorities nor the risks to reefs have been changed by the tsunami and it is vitally important that resources are not directed to short term, small scale, rehabilitation programs which will not reverse long term declines in reef condition which were evident at many of our sites

Acehnese reefs in the wake of the Asian tsunami

The Sumatra-Andanaman tsunami was one of the greatest natural disasters in recorded human history. Here, we show that on the northwest coast of Aceh, Indonesia, where the tsunami was most ferocious [1], the damage to corals, although occasionally spectacular, was surprisingly limited. We detected no change in shallow coral assemblages between March 2003 and March 2005, with the exception of one site smothered by sediment. Direct tsunami damage was dependent on habitat and largely restricted to corals growing in unconsolidated substrata, a feature unique to tsunami disturbance. Reef condition, however, varied widely within the region and was clearly correlated with human impacts prior to the tsunami. Where fishing has been controlled, coral cover was high. In contrast, reefs exposed to destructive fishing had low coral cover and high algal cover, a phase shift the tsunami may exacerbate with an influx of sediments and nutrients [2]. Healthy reefs did not mitigate the damage on land. Inundation distance was largely determined by wave height and coastal topography. We conclude that although chronic human misuse has been much more destructive to reefs in Aceh than this rare natural disturbance [3], human modification of the reef did not contribute to the magnitude of damage on land

Geographically conserved rates of background mortality among common reef-building corals in Lhaviyani Atoll, Maldives, versus northern Great Barrier Reef, Australia

Even in the absence of major disturbances (e.g., cyclones and bleaching), corals are consistently subject to high levels of background mortality, which under-mines individual fitness and resilience of coral colonies. Most studies of coral mortality however only focus on catastrophic mortality associated with major acute disturbance events, neglecting to consider background levels of chronic mortality that have a significant influence on population structure and turnover. If, for example, there are geo-graphic differences in the prevalence of injuries and rates of background mortality, coral communities may vary in their susceptibility to acute large-scale disturbances and environmental change. This study quantified the prevalence and severity of partial mortality for four dominant and widespread coral taxa (massive Porites, encrusting Montipora, Acropora hyacinthus,and branching Pocillopora) at Lhaviyani Atoll, Maldives, and on the northern Great Barrier Reef, Australia. The prevalence and severity of sublethal injuries varied greatly among taxa, but was generally similar between locations; on the Great Barrier Reef, 99.4 % Porites colonies, 66 % of A. hyacinthus, and 64 % of Pocillopora had conspicuous injuries, compared to 92.4 % of Porites, 47.5 % of A. hyacinthus, and 44 % of Pocillopora colonies in Lhaviyani Atoll. These results suggest that background rates of mortality and injury, and associated resilience of coral populations and communities to large-scale disturbances, are conserved at large geo-graphic scales, though adjacent colonies can have markedly different injury regimes, likely to lead to strong intraspecific variation in colony fitness and resilience

CMEP Pacific Marine Climate Change Report Card 2018

Reliance on marine biodiversity is high across Pacific nations, thus reducing human pressures on habitats is vital to promote diverse and productive ecosystem which are more resilient to climate change. Climate change is putting the fundamental needs of ocean dependent Pacific communities at risk, including living space and housing, food and water security, culture, health and wellbeing. Pollution and marine waste, population growth, resource over-exploitation and overfishing, invasive species, damage to key ecosystems, and coastal development are all magnifying the effects of climate change. Flexible management systems and adaption projects which build climate resililence are urgently needed, that are adaptive over time, connect terrestrial and marine systems and link different sectors. Engaging communities is a fundamental part of successful climate change action and the intentional inclusion of social and cultural groups will benefit efforts to build climate resilence