潜水旅游对珊瑚礁生态系统影响研究的进展

早期潜水活动曾被认为是一种经济价值高且对珊瑚礁影响较小的生态旅游项目,但随着潜水旅游逐渐盛行,诸多研究结果表明,全世界潜水区的珊瑚礁均出现了不同程度的退化,一些热门潜水旅游区每年接纳的游客数量甚至远超出珊瑚礁的生态承受极限.笔者对与珊瑚礁生态系统与潜水旅游承载能力相关的研究结果进行了统计分析,总结了潜水活动影响珊瑚礁的...     

Mg/Ca Thermometry in Coral Skeletons

The magnesium-to-calcium (Mg/Ca) ratio of coral skeletons from Ishigaki Island, Ryukyu Islands, Japan, closely tracked sea surface temperature (SST) over an 8-year period. Measurements were made with the fast technique of inductively coupled plasma-atomic emission spectrometry. The variation of the coral Mg/Ca ratio with SST change is about four times that of the current, widely used coral strontium-to-calcium ratio. The temporal and geographic variation of the seawater Mg2+/Ca2+ ratio probably has little influence on coral Mg/Ca variation. Results indicate that the coral Mg/Ca ratio has the potential to provide fast, precise, high-resolution proxies for past tropical SSTs.     

Long-term region-wide declines in Caribbean corals

We report a massive region-wide decline of corals across the entire Caribbean basin, with the average hard coral cover on reefs being reduced by 80%, from about 50% to 10% cover, in three decades. Our meta-analysis shows that patterns of change in coral cover are variable across time periods but largely consistent across subregions, suggesting that local causes have operated with some degree of synchrony on a region-wide scale. Although the rate of coral loss has slowed in the past decade compared to the 1980s, significant declines are persisting. The ability of Caribbean coral reefs to cope with future local and global environmental change may be irretrievably compromised.     

Growth of Western Australian corals in the anthropocene

Anthropogenic increases of atmospheric carbon dioxide lead to warmer sea surface temperatures and altered ocean chemistry. Experimental evidence suggests that coral calcification decreases as aragonite saturation drops but increases as temperatures rise toward thresholds optimal for coral growth. In situ studies have documented alarming recent declines in calcification rates on several tropical coral reef ecosystems. We show there is no widespread pattern of consistent decline in calcification rates of massive Porites during the 20th century on reefs spanning an 11° latitudinal range in the southeast Indian Ocean off Western Australia. Increasing calcification rates on the high-latitude reefs contrast with the downward trajectory reported for corals on Australia's Great Barrier Reef and provide additional evidence that recent changes in coral calcification are responses to temperature rather than ocean acidification.     

Destruction of Pacific Corals by the Sea Star Acanthaster planci

Acanthaster planci, a coral predator, is undergoing a population explosion in many areas of the Pacific Ocean. Data on feeding rates, population movements, and stages of infestation were collected along coral reefs of Guam and Palau. Direct observations on destruction of Guam's coral reefs indicate that narrow, fringing reefs may be killed as rapidly as 1 kilometer per month. In a 2(1/2)-year period, 90 percent of the coral was killed along 38 kilometers of Guam's shoreline.     

Coral reef growth in the galapagos: limitation by sea urchins

The regular echinoid Eucidaris thouarsii is a conspicuous omnivore on coral bottoms in the Galápagos. Unlike Eucidaris in Panama and mainland Ecuador, Galápagos Eucidaris are large and abundant and graze heavily in the open on live corals day and night. These differences are probably due in large part to more intense predation by fishes on mainland compared with island urchin populations. An assessment of coral growth versus coral attrition from grazing shows that Eucidaris interferes with the establishment of pocilloporid reef frame and therefore reduces reef growth in the Galápagos.     

Caribbean reef development was independent of coral diversity over 28 million years

The relationship between natural variations in coral species diversity, reef development, and ecosystem function on coral reefs is poorly understood. Recent coral diversity varies 10-fold among geographic regions, but rates of reef growth are broadly similar, suggesting that diversity is unimportant for reef development. Differences in diversity may reflect regional differences in long-term biotic history in addition to environmental conditions. Using a combination of new and published fossil and stratigraphic data, we compared changes in coral diversity and reef development within the tropical western Atlantic over the past 28 million years. Reef development was unrelated to coral diversity, and the largest reef tracts formed after extinction had reduced diversity by 50%. High diversity is thus not essential for the growth and persistence of coral reefs.     

Turbulence, cleavage, and the naked embryo: a case for coral clones

After mass spawning events, coral embryos, lacking the protective capsule of other metazoans, are directly exposed to the environment at the ocean surface. Here, we present evidence that modest turbulence disrupts the integrity of these embryos, which fragment into totipotent cells that develop into proportionately smaller functional larvae. The level of turbulence required to fragment coral embryos can be generated from small wind-generated waves, which occur frequently during coral spawning on the Great Barrier Reef. The formation of planktonic coral clones, through natural embryo fragmentation of broadcast spawn, is a previously unknown mode of reproduction in the animal kingdom.     

Climate change,human impacts,and the resilience of coral reefs

The diversity, frequency, and scale of human impacts on coral reefs are increasing to the extent that reefs are threatened globally. Projected increases in carbon dioxide and temperature over the next 50 years exceed the conditions under which coral reefs have flourished over the past half-million years. However, reefs will change rather than disappear entirely, with some species already showing far greater tolerance to climate change and coral bleaching than others. International integration of management strategies that support reef resilience need to be vigorously implemented, and complemented by strong policy decisions to reduce the rate of global warming.     

Discovery of symbiotic nitrogen-fixing cyanobacteria in corals

Colonies of the Caribbean coral Montastraea cavernosa exhibit a solar-stimulated orange-red fluorescence that is spectrally similar to a variety of fluorescent proteins expressed by corals. The source of this fluorescence is phycoerythrin in unicellular, nonheterocystis, symbiotic cyanobacteria within the host cells of the coral. The cyanobacteria coexist with the symbiotic dinoflagellates (zooxanthellae) of the coral and express the nitrogen-fixing enzyme nitrogenase. The presence of this prokaryotic symbiont in a nitrogen-limited zooxanthellate coral suggests that nitrogen fixation may be an important source of this limiting element for the symbiotic association.     

Localized dispersal and recruitment in great barrier reef corals: the helix experiment

To examine the problem of how far coral larvae disperse from their natal reef, coral recruitment densities were experimentally determined at distances up to 5 kilometers from a small, relatively isolated platform reef, Helix Reef, on the central Great Barrier Reef for 7 months. High concentrations of recruits, accounting for up to 40 percent of all recruitment, were found downstream of the reef in areas of high water residence time, suggesting that near-field(proximal) circulation has a profound influence on dispersal and recruitment of coral larvae. Coral recruitment declined logarithmically with distance from the reef, decreasing by an order of magnitude at radial distances of only 600 to 1200 meters. On an ecological time scale, advective dispersal of semipassive marine larvae with relatively short planktonic lives(minimally days) may be extensive, but success of recruitment is highly limited. Through evolutionary time, sufficient dispersal occurs to ensure gene flow to reef tracts hundreds or possibly thousands of kilometers apart. In the short term, however, coral reefs appear to be primarily self-seeded with respect to coral larvae.     

Acanthaster: effect on coral reef growth in panama

Analysis of data on coral abundance and growth, and the population size (26 individuals per hectare) and feeding rate of Acanthaster indicates that Pocillopora reefs on the Pacific coast of Panama are undergoing vigorous growth in the presence of this predator. Prediction of the effects of a population increase in Acanthaster to plague proportions (2.5 times that presently observed) suggests that reefs could still maintain a positive growth. However, Acanthaster at ten times the present population density would lead to rapid destruction of reefs. It is argued that coral destruction due to Acanthaster represents only one of several factors affecting coral reef progression.     

Comparative species richness in fluctuating and constant environments: coral-associated decapod crustaceans

The number of decapod species associated with the coral Pocillopora damicornis is compared between two regions on the Pacific coast of Panama which are of the same geologic age but differ in environmental characteristics. The relationship between number of species and coral head size does not differ between the two regions but species composition among coral heads is more variable in the fluctuating environment. Thus there are more species (55 compared to 37) associated with corals in the fluctuating environment than in the constant environment. These data impugn the concept that environmental constancy increases species richness. They support the hypothesis that species equilibrium within habitats is maintained by measurable ecological factors-in this case, the effects of a natural physical disturbance.     

Community structure of coral reefs on opposite sides of the isthmus of panama

Competition for space amon reef corals includes interspecific destruction by extracoelenteric digestion., rapid growth. and Overtopping. No Caribbean species excela in all strategies, and on western Caribbean coral reefs there is a positive correlation between coral abudance and diversity. On eastern Pacific coral reefs, however. Pocillopora damicornis excludes other corals, and on these reefs there is an inverse relation between coral abundance and diversity, except in areas where distrubances, such as Acanthaster predation offset space monopolization.     

Coral-Eating Sea Stars Acanthaster planci in Hawaii

An aggregation of 2 x 10(4) Acanthaster planci was observed from September 1969 to November 1970. The sea stars within the aggregation were very uniform in size, and their reproduction was seasonal. Their average diameter and weight also varied seasonally in a manner that suggests a correlation between average size and breeding condition. The aggregation remained compactly situated in a band a few to tens of meters wide and about 2 kilometers long, parallel to the shore. The band did not move appreciably during the observation period. The sea stars were feeding selectively on a coral which was a minor component of the total coral cover. The coral in the area was predominantly alive, and the proportion of dead coral did not increase appreciably during our period of observation.     

The effect of algal symbionts on the accuracy of Sr/Ca paleotemperatures from coral

The strontium-to-calcium ratio (Sr/Ca) of reef coral skeleton is commonly used as a paleothermometer to estimate sea surface temperatures (SSTs) at crucial times in Earth's climate history. However, these estimates are disputed, because uptake of Sr into coral skeleton is thought to be affected by algal symbionts (zooxanthellae) living in the host tissue. Here, we show that significant distortion of the Sr/Ca temperature record in coral skeleton occurs in the presence of algal symbionts. Seasonally resolved Sr/Ca in coral without symbionts reflects local SSTs with a temperature sensitivity equivalent to that of laboratory aragonite precipitated at equilibrium and the nighttime skeletal deposits of symbiotic reef corals. However, up to 65% of the Sr/Ca variability in symbiotic skeleton is related to symbiont activity and does not reflect water temperature.     

Preindustrial to modern interdecadal variability in coral reef pH

The oceans are becoming more acidic due to absorption of anthropogenic carbon dioxide from the atmosphere. The impact of ocean acidification on marine ecosystems is unclear, but it will likely depend on species adaptability and the rate of change of seawater pH relative to its natural variability. To constrain the natural variability in reef-water pH, we measured boron isotopic compositions in a approximately 300-year-old massive Porites coral from the southwestern Pacific. Large variations in pH are found over approximately 50-year cycles that covary with the Interdecadal Pacific Oscillation of ocean-atmosphere anomalies, suggesting that natural pH cycles can modulate the impact of ocean acidification on coral reef ecosystems.     

Zonation of uplifted pleistocene coral reefs on barbados, west indies

The coral species composition of uplifted Pleistocene reefs on Barbados is very similar to Recent West Indian reefs. Acropora palmata, Acropora cervicornis, and Montastrea annularis are qtuantitatively the most important of the coral species.     

Sea-surface temperature from coral skeletal strontium/calcium ratios

Seasonal records of tropical sea-surface temperature (SST) over the past 10(5) years can be recovered from high-precision measurements of coral strontium/calcium ratios with the use of thermal ionization mass spectrometry. The temperature dependence of these ratios was calibrated with corals collected at SST recording stations and by (18)O/(16)O thermometry. The results suggest that mean monthly SST may be determined with an apparent accuracy of better than 0.5 degrees C. Measurements on a fossil coral indicate that 10,200 years ago mean annual SSTs near Vanuatu in the southwestern Pacific Ocean were about 5 degrees C colder than today and that seasonal variations in SST were larger. These data suggest that tropical climate zones were compressed toward the equator during deglaciation.     

Siphonodictidine, a Metabolite of the Burrowing Sponge Siphonodictyon sp. That Inhibits Coral Growth

Siphonodictidine is the major secondary metabolite of an undescribed Indo-Pacific sponge Siphonodictyon sp. that burrows into living coral heads. The structure of siphonodictidine was determined from spectral data. Laboratory bioassays suggest that siphonodictidine and, by analogy, the siphonodictyals from S. coralliphagum are responsible for maintaining zones of dead coral polyps around the oscular chimneys of these sponges.