Tsunami Survey Expedition: Preliminary Investigation of Maldivian Coral Reefs Two Weeks After the Event

On December 26th 2004, a earthquake west of Sumatra generated a devastating tsunami. Hundreds of thousands of people fell victim. Economic losses were greatest in those countries dependant on tourism. The impact in the Maldives on persons and things was modest. Immediately following the event and notwithstanding the lack of scientific data, the mass media gave catastrophic reports on the state of coral reefs in the area. This paper reports on the first survey on coral reefs in the Maldives after the Tsunami. Ocean walls, passes, inner reefs, and shoals in the North and South Malé atolls, were surveyed two weeks after the event. Significant damage was recorded in the passes in the South Malé atoll. Our observations showed that the damage was more or less extensive depending on latitude and topography. Sri Lanka may have broken the wave’s rush, reducing the extent of the impact on northern atolls. The water’s acceleration inside the passes was so intense as to cause reef collapses. The observed damage represents a minimum fraction of the entire coral reef system. Tourist perception of the area seems unchanged. These data may be used to disseminate correct information about the state of Maldives coral reefs, which would be useful in relaunching local economy.     

A numerical model of wave- and current-driven nutrient uptake by coral reef communities

We developed a numerical model capable of simulating the spatial zonation of nutrient uptake in coral reef systems driven by hydrodynamic forcing (both from waves and currents). Relationships between nutrient uptake and bed stress derived from flume and field studies were added to a four-component biogeochemical model embedded within a three-dimensional (3-D) hydrodynamic ocean model coupled to a numerical wave model. The performance of the resulting coupled physical-biogeochemical model was first evaluated in an idealized one-dimensional (1-D) channel for both a pure current and a combined wave-current flow. Waves in the channel were represented by an oscillatory flow with constant amplitude and frequency. The simulated nutrient concentrations were in good agreement with the analytical solution for nutrient depletion along a uniform channel, as well as with existing observations of phosphate uptake across a real reef flat. We then applied this integrated model to investigate more complex two-dimensional (2-D) nutrient dynamics, firstly to an idealized coral reef-lagoon morphology, and secondly to a realistic section of Ningaloo Reef in Western Australia, where nutrients were advected into the domain via alongshore coastal currents. Both the idealized reef and Ningaloo Reef simulations showed similar patterns of maximum uptake rates on the shallow forereef and reef crest, and with nutrient concentration decreasing as water flowed over the reef flat. As a result of the cumulative outflow of nutrient-depleted water exiting the reef channels and then being advected down the coast by alongshore currents, both reef simulations exhibited substantial alongshore variation in nutrient concentrations. The coupled models successfully reproduced the observed spatial-variability in nitrate concentration across the Ningaloo Reef system.     

Assesment of Trace Elements and Organic Pollutants from a Marine Oil Complex into the Coral Reef System of Cayo Arcas, Mexico

Possible contaminants produced by the Petroleos Mexicanos (PEMEX) marine oil complex in the vicinity of the Cayo Arcas (Mexico) coral reef ecosystem were evaluated by analyzing sediments and sea water for hydrocarbons and metal elements. We found that the concentrations of aliphatic hydrocarbons in the sea water were generally low, with the highest values detected near the oil station; the concentration of polycyclic aromatic hydrocarbons (PAHs) was generally below the detection limit. The hydrocarbons found in the sediments seem to have a pyrogenic origin, and were probably produced by marine traffic in the study area. The total PAH concentration did not exceed the NOAA criteria, although levels of some individual PAHs did. The only metal detected in the sea water at high concentrations was nickel. The Ni/V ratio in the sediments indicates the contribution of crude oil to the system. The high content of Ni and Zn was attributed to the ballast waters from the oil tankers that load at the station's monobuoys. The presence of fine sediments that commonly originate from terrestrial ecosystems supported this assumption.     

Potential of Marine Reserves to Cause Community-Wide Changes beyond Their Boundaries

Abstract:  Fishing and other human activities can alter the abundances, size structure, and behavior of species playing key roles in shaping marine communities (e.g., keystone predators), which may in turn cause ecosystem shifts. Despite extensive evidence that cascading trophic interactions can underlie community-wide recovery inside no-take marine reserves by protecting high-level predators, the spatial extent of these effects into adjacent fished areas is unknown. I examined the potential for community-wide changes (i.e., the transition from overgrazed coralline barrens to macroalgal beds) in temperate rocky reefs within and around a no-take marine reserve. For this purpose I assessed distribution patterns of predatory fishes, sea urchins, and barrens across the reserve boundaries. Predatory fishes were significantly more abundant within the reserve than in adjacent locations, with moderate spillover across the reserve edges. In contrast, community-wide changes of benthic assemblages were apparent well beyond the reserve boundaries, which is consistent with temporary movements of predatory fishes (e.g., foraging migration) from the reserve to surrounding areas. My results suggest that no-take marine reserves can promote community-wide changes beyond their boundaries.     

初始pH值对连续投加铝盐混凝去除小分子有机物的影响机制

以污水厂二级出水中小分子有机物强化混凝去除为目的,提出了连续投加混凝工艺(CDC),并以水杨酸为模型小分子有机物,研究了初始pH值对CDC工艺去除效果的影响以及铝离子与水杨酸的络合特性.结果表明,初始pH值6时CDC工艺的去除率最高,比常规混凝工艺提升了13.8%.但是初始pH值5和7时CDC工艺的提升效果较小.三维荧光结果表明,不同pH值下水杨酸和铝离子的络合特性不同.X射线光电子能谱和电喷雾质谱结果表明,pH值5时CDC工艺前期主要生成1:1络合物Al(OH)(C₇H₄O₃)(H₂O)₂.其络合作用强烈,稳定性较高,难以从水中去除.pH值6时前期主要生成中等聚合铝(如原位Al₁₃),其与水杨酸形成的络合物可以参与到铝离子的生长过程,最终生成表面崎岖形态松散的珊瑚礁状絮体,强化了水杨酸的去除.pH值7时,主要生成不定形氢氧化铝,通过絮体表面吸附小分子有机物.     

Use of environmental DNA in assessment of fish functional and phylogenetic diversity

Assessing the impact of global changes and protection effectiveness is a key step in monitoring marine fishes. Most traditional census methods are demanding or destructive. Nondisturbing and nonlethal approaches based on video and environmental DNA are alternatives to underwater visual census or fishing. However, their ability to detect multiple biodiversity factors beyond traditional taxonomic diversity is still unknown. For bony fishes and elasmobranchs, we compared the performance of eDNA metabarcoding and long-term remote video to assess species’ phylogenetic and functional diversity. We used 10 eDNA samples from 30 L of water each and 25 hr of underwater videos over 4 days on Malpelo Island (pacific coast of Colombia), a remote marine protected area. Metabarcoding of eDNA detected 66% more molecular operational taxonomic units (MOTUs) than species on video. We found 66 and 43 functional entities with a single eDNA marker and videos, respectively, and higher functional richness for eDNA than videos. Despite gaps in genetic reference databases, eDNA also detected a higher fish phylogenetic diversity than videos; accumulation curves showed how 1 eDNA transect detected as much phylogenetic diversity as 25 hr of video. Environmental DNA metabarcoding can be used to affordably, efficiently, and accurately census biodiversity factors in marine systems. Although taxonomic assignments are still limited by species coverage in genetic reference databases, use of MOTUs highlights the potential of eDNA metabarcoding once reference databases have expanded.     

Quantifying parameter uncertainty in a coral reef model using Metropolis-Coupled Markov Chain Monte Carlo

Coral reefs are threatened ecosystems, so it is important to have predictive models of their dynamics. Most current models of coral reefs fall into two categories. The first is simple heuristic models which provide an abstract understanding of the possible behaviour of reefs in general, but do not describe real reefs. The second is complex simulations whose parameters are obtained from a range of sources such as literature estimates. We cannot estimate the parameters of these models from a single data set, and we have little idea of the uncertainty in their predictions.We have developed a compromise between these two extremes, which is complex enough to describe real reef data, but simple enough that we can estimate parameters for a specific reef from a time series. In previous work, we fitted this model to a long-term data set from Heron Island, Australia, using maximum likelihood methods. To evaluate predictions from this model, we need estimates of the uncertainty in our parameters. Here, we obtain such estimates using Bayesian Metropolis-Coupled Markov Chain Monte Carlo. We do this for versions of the model in which corals are aggregated into a single state variable (the three-state model), and in which corals are separated into four state variables (the six-state model), in order to determine the appropriate level of aggregation. We also estimate the posterior distribution of predicted trajectories in each case.In both cases, the fitted trajectories were close to the observed data, but we had doubts about the biological plausibility of some parameter estimates. We suggest that informative prior distributions incorporating expert knowledge may resolve this problem. In the six-state model, the posterior distribution of state frequencies after 40 years contained two divergent community types, one dominated by free space and soft corals, and one dominated by acroporid, pocilloporid, and massive corals. The three-state model predicts only a single community type. We conclude that the three-state model hides too much biological heterogeneity, but we need more data if we are to obtain reliable predictions from the six-state model. It is likely that there will be similarly large, but currently unevaluated, uncertainty in the predictions of other coral reef models, many of which are much more complex and harder to fit to real data.     

Starting point or solution? Community-based marine protected areas in the Philippines

In 1985, in response to declining coral reef conditions, local residents and officials established small, no-take marine sanctuaries on Balicasag and Pamilacan Islands through a community-based process. The implementation of marine protected areas (MPAs) on Balicasag and Pamilacan Islands has been a partial success. As a direct result of protection, living hard coral cover has increased by 119% in Balicasag's sanctuary and by 67% in the non-sanctuary during the period 1984 to 1999, but Balicasag's reef is increasingly affected by breakage from anchors from dive boats and Crown-of-thorns starfish infestations. During the same period, living hard coral cover decreased by 20% in Pamilacan's sanctuary and by 45% in the non-sanctuary from 1984 to 1999. The decrease in living hard coral cover in Pamilacan's sanctuary is most likely a result of the 1998 bleaching event, Crown-of-thorn starfish and possible storm damage. Although there was an initial increase in the economically important target fish abundance in the Balicasag sanctuary and non-sanctuary and in the Pamilacan sanctuary during the first two years of implementation in the mid-1980s, there has since been a significant decline. Mean target fish abundance for the Balicasag non-sanctuary at 230 (+/- 65) individuals per 500 m2 is not significantly different from control sites without MPAs on nearby Panglao and Cabilao Islands at 164 (+/- 67) individuals per 500 m2. In general, fish abundance and diversity inside and outside the sanctuaries peaked in 1986, a year after the establishment of the sanctuaries when enforcement was strictest. Therefore, despite considerable success in enforcing regulations associated with these small MPAs at Balicasag and Pamilacan Islands, a trend of declining fish abundance and species richness among economically valuable species immediately outside the no-take areas highlights the limitations of small and isolated MPAs. This study contributes to the growing sentiment that it is not realistic for scattered, small no-take areas to maintain fish abundance and diversity on surrounding reefs when intensive fishing effort immediately adjacent to no-take areas removes most fish that exit these areas. This finding emphasizes the importance of nesting individual MPAs within broader management regimes that lead to overall fishing effort reduction and networking of MPAs. Among other recommendations, the authors advocate for continued support for community-based MPAs, a network of MPAs, reduced fishing effort in areas surrounding the MPAs and other management measures to improve the quality of the coral reef habitats.     

三亚湾春夏季初级生产力的分布特征及环境影响研究

2006年春季和夏季对三亚湾水域初级生产力进行了调查,结果表明:三亚湾春季和夏季表层潜在初级生产力(以C计)平均值分别为7.54 mS/(m<'3>·h)和6.66 mg/(m<'3>·h);两个季节初级生产力的水平分布特征相似.在三亚河口近岸水域始终存在叶绿素及初级生产力的高值区,这与河口近岸营养物质输入密切相关,并...