Identifying high value areas for conservation: Accounting for connections among terrestrial,freshwater, and marine habitats in a tropical island system

Functional ecosystems depend on biotic and abiotic connections among different environmental realms, including terrestrial, freshwater, and marine habitats. Accounting for such connections is increasingly recognized as critical for conservation of ecosystems, especially given growing understanding of the way in which anthropogenic landscape disturbances can degrade both freshwater and marine habitats. This need may be paramount in conservation planning for tropical island ecosystems, as habitats across realms are often in close proximity, and because endemic organisms utilize multiple habitats to complete life histories. In this study, we used Marxan analysis to develop conservation planning scenarios across the five largest islands of Hawaii, in one instance accounting for and in another excluding habitat connectivity between inland and coastal habitats. Native vegetation, perennial streams, and areas of biological significance along the coast were used as conservation targets in analysis. Cost, or the amount of effort required for conservation, was estimated using an index that integrated degree and intensity of anthropogenic landscape disturbances. Our results showed that when connectivity is accounted for among terrestrial, freshwater, and marine habitats, areas identified as having high conservation value are substantially different compared to results when connectivity across realms is not considered. We also showed that the trade-off of planning conservation across realms was minimal and that cross-realm planning had the unexpected benefit of selecting areas with less habitat degradation, suggesting less effort for conservation. Our cross-realm planning approach considers biophysical interactions and complexity within and across ecosystems, as well as anthropogenic factors that may influence habitats outside of their physical boundaries, and we recommend implementing similar approaches to achieve integrated conservation efforts.     

珊瑚礁白化研究进展

珊瑚礁白化是由于珊瑚失去体内共生的虫黄藻和（或）共生的虫黄藻失去体内色素而导致五彩缤纷的珊瑚礁变白的生态现象。近年来,频繁发生的珊瑚礁白化导致了珊瑚礁生态系统严重退化,并已经影响到全球珊瑚礁生态系统的平衡,受到了人们的高度重视。研究认为：（1）大范围珊瑚礁白化主要是全球环境变化引起的,尤其是全球变暖和紫外辐射增强;（2）导致珊瑚礁白化的机制主要在于细胞机制和光抑制机制;（3）珊瑚礁白化后的恢复与白化程度有关,大范围白化的珊瑚礁完全恢复需要几年到几十年;（4）珊瑚礁白化的后果在于降低珊瑚繁殖能力、减缓珊瑚礁生长、改变礁栖生物的群落结构,导致大面积珊瑚死亡和改变珊瑚礁生态类型,如变为海藻型等;（5）与珊瑚共生的D系群虫黄藻更适应高温环境,珊瑚礁有可能通过D系群逐渐取代C系群的方式适应全球环境变化。     

Bioerosion caused by foraging of the tropical chiton Acanthopleura gemmata at One Tree Reef, southern Great Barrier Reef

The bioerosive potential of the intertidal chiton Acanthopleura gemmata on One Tree Reef was determined by quantification of CaCO₃ in daily faecal pellet production of individuals transplanted into mesocosms after nocturnal-feeding forays. Mean bioerosive potential was estimated at 0.16 kg CaCO₃ chiton⁻¹ yr⁻¹. Bioerosion rates were estimated for populations on two distinct chiton habitats, reef margin (0.013 kg CaCO₃ m⁻² yr⁻¹) and beachrock platform (0.25 kg CaCO₃ m⁻² yr⁻¹). Chiton density on the platform was orders of magnitude greater than on the reef margin. The surface-lowering rate (0.16 mm m⁻² yr) due to bioerosion by the beachrock population is a substantial contribution to the total surface-lowering rate of 2 mm m⁻² yr⁻¹ previously reported for One Tree Reef across all erosive agents. At high densities, the contribution of A. gemmata to coral reef bioerosion budgets may be comparable to other important bioeroders such as echinoids and fish.     

Reconstruction of coral reef fisheries catches in American Samoa, 1950–2002

Fisheries catches from Pacific Island coral reefs are rarely recorded in official statistics. Reconstruction of catch estimates with limited hard data requires interpolation and assumptions, justifiable only by the unsatisfactory alternative of continued substitution of zero catches, a common policy interpretation for ‘no data’. Uncertainties associated with reconstructions are high, requiring conservative estimation. American Samoan domestic fisheries consist of an artisanal, small-boat sector, whose commercial catches are reported, and a shore-based subsistence sector, with no regular reporting. Our catch reconstruction (with large pelagic species removed) suggested a 79% decrease in catches between 1950 (752 t) and 2002 (155 t). Accounting for rapid human population growth on the main island, the per capita catch rate may have declined from 36.3 kg·person⁻¹ year⁻¹ in 1950 to 1.3 kg·person⁻¹ year⁻¹ by 2002, while the catch rate for the inhabited outer islands has been independently reported as 58.6 kg·person⁻¹ year⁻¹. Catch per area of coral reef (to 50-m depth) may have declined from 5.5 to 0.7 t km⁻² year⁻¹ for the main island, and from 9.1 to 4.9 t km⁻² year⁻¹ for the outer islands, for 1950 and 2002, respectively. Summed for 1950–2002, our reconstruction suggested a 17-fold difference between reconstructed estimates and reported statistics.     

Suppression of herbivory by macroalgal density: a critical feedback on coral reefs?

Coral reefs globally are in decline, with some reefs undergoing phase shifts from coral-dominance to degraded states dominated by large fleshy macroalgae. These shifts have been underpinned by the overharvesting of herbivorous fishes and represent a fundamental change in the physical structure of these reefs. Although the physical structure provided by corals is regarded as a key feature that facilitates herbivore activity, the influence of the physical structure of macroalgal stands is largely unknown. Using transplanted Sargassum, the largest coral reef macroalga, we created habitat patches of predetermined macroalgal density (0.25-6.23 kg m(-2)). Remote video cameras revealed both grazing and browsing fishes avoided high density patches, preferring relatively open areas with low macroalgal cover. This behaviour may provide a positive feedback leading to the growth and persistence of macroalgal stands; increasing the stability of phase shifts to macroalgae.     

A review of hybridization in marine angelfishes (Perciformes: Pomacanthidae)

Synopsis Although hybridization of terrestrial and freshwater organisms has been well-studied, very little work has focused on hybridization among coral reef fish species. In the present paper, eleven examples of probable hybrids between marine angelfishes (Pomacanthidae) are reviewed. Evidence is presented which strongly suggests that the nominal speciesApolemichthys armitagei is invalid and that specimens previously identified as this species represent hybrids betweenA. trimaculatus andA. xanthurus. Of the remaining ten probable pomacanthid hybrids, five are inCentropyge (C. eibli x C. flavissimus, C. eibli x C. vrolikii, C. flavissimus x C. vrolikii, C. loricu0lus x C. potteri, andC. multifasciatus x C. venustus); one inHolacanthus (H. bermudensis x H. ciliaris), and four inPomacanthus (P. arcuatus x P. paru, P. chrysurus x P. maculosus, P. maculosus x P. semicirculatus, andP. sexstriatus x P. xanthometapon). An additional five examples of possible pomacanthid hybrids are described, two inCentropyge, two inChaetodontoplus and one inPomacanthus. Examination of hybrids may provide clues on reproductive behavior, dispersal capabilities, and phylogenetic relationships of species. More studies on hybridization in coral reef fish species, particularly those involving molecular techniques, are needed.     

Oxidative stress indicators and trace elements in the blue shark (Prionace glauca) off the east coast of the Mexican Pacific Ocean

Trace element concentrations and oxidative stress indicators (including production of reactive oxygen species (ROS), antioxidant enzyme activities and oxidative damage) were measured in muscle of blue sharks collected along the west coast of Baja California Sur to determine potential differences by sex and maturity cohorts. Mercury (Hg) concentration in muscle samples from larger sharks (>200 cm LT) exceeded the permissible limit (>1 ppm wet weight) for human consumption set by numerous international agencies. Significant differences were found in Hg concentrations (mature>immature; males>females), and in protein carbonyl concentrations (male>female); however, except for carbonyl protein levels, no significant differences by sex or maturity stage were found in the oxidative stress indicators. Differences between sexes and maturity stages in trace element concentration and carbonyl protein levels in blue shark muscle may be related to variations in diet within different cohorts.     

Environmental variables affecting the sexual segregation of great white sharks Carcharodon carcharias at the Neptune Islands South Australia

The seasonal temporal sexual segregation of white sharks Carcharodon carcharias , at the Neptune Islands, South Australia, is described in relation to environmental variables. A significant sexual segregation was found at this site with sex ratios strongly favouring males overall. Males were more prevalent than females in all months in a 3 year sampling period, aside from April and May. There was a significant difference between the sexes in terms of mean daily numbers over the months of the study. It was also observed that sexual segregation fluctuated for unknown reasons on a temporal scale. Predictive models for estimating male and female numbers based on a series of abiotic factors were generated. Sea surface temperature, tidal height, tidal range, moon phase, cloud cover, underwater visibility and swell height were related to daily sightings of male and female white sharks to determine the influence of these variables on sexual segregation. Visibility and sea surface temperature affected male numbers, however, visibility did not affect sexual segregation. Tidal height was significantly different between males and females. Sea surface temperature also appeared to be related to sexual segregation in this species. Females were present when temperatures ranged from 15·7 to 18·1° C whereas males were observed at temperatures ranging from 14·3 to 17·8° C, with a peak in sightings in September, when sea surface temperatures were at their lowest. Since parturition is thought to occur in spring or summer, it is suggested that females are absent at this time and only return during prime feeding periods or times at which temperatures are elevated in order to increase developmental growth rates of their young. The significantly lower temperatures in 2003 may explain the absence of females in this year. Hypotheses related to temperature regulation in this species are put forward to explain the sexual segregation observed.