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Spectral differences affect solar cell performance, an effect that is especially visible when comparing different solar cell technologies. To reproduce the impact of varying spectra on solar cell performance in the lab, a unique classification of spectra is needed, which is currently missing in literature. The most commonly used classification, average photon energy (APE), is not unique, and a single APE value may represent various spectra depending on location. In this work, we propose a classification method based on an iterative use of the k-means clustering algorithm. We call this method RISE (Representative Identification of Spectra and the Environment). We define a set of 18 spectra using RISE and reproduce the spectral impact on energy yield for various solar cell technologies and locations. We explore effects on yield for commercially available solar cell technologies (Si, CdTe) in four locations: Singapore (fully humid equatorial climate), Colorado (cold arid), Brazil (warm, humid, subtropical), and Denmark (fully humid warm temperature).We then reduce our findings to practice by implementing the spectrum set into an LED current-voltage (IV)tester. We verify our performance predictions using our set of representative spectra to reproduce energyyield differences between Si solar cells and CdTe solar cells with an average error of less than 1.5 ± 0.5% ascompared to over 5% when using standard testing conditions.

For photovoltaic devices to optimally operate in high-temperature conditions, a solution must be found that addresses the device's efficiency dependence on temperature. During operation, photovoltaic devices heat up and emit low-grade waste heat, in turn, reducing performance. By affixing a thermoelectric generator to a photovoltaic device, the waste heat is utilized to generate additional electricity and partially offset photovoltaic performance loss. Through physics-driven simulation, we examine the performance and energy yield improvements that a conjoined photovoltaic and thermoelectric generator exhibits under varying operating conditions.

Solar spectra change depending on location, weather, and time of day around the world. These spectral variations affect the performance of photovoltaic (PV) cells and modules and are not captured by standard testing procedures. We introduce a method to classify spectra and use this classification to develop a testing procedure to reproduce spectral conditions of locations within various climate zones. With LED solar simulators becoming commercially available and representative sets of outdoor spectra found, the gap between real world outdoor testing and indoor testing is closing. With LED-based testing of CdTe, Si, and GaAs PV cells, we show that the effects of spectral shifts on short circuit current are captured, demonstrating the potential use of this method for more accurate testing of solar modules indoors.

High-temperature annealing, known as Tabula Rasa (TR), proves to be an effective method for dissolving oxygen precipitate nuclei in n-Cz silicon and makes this material resistant to temperature-induced and process-induced lifetime degradation. Tabula Rasa is especially effective in n-Cz wafers with oxygen concentration >15 ppma. Vacancies, self-interstitials, and their aggregates result from TR as a metastable side effect. Temperature-dependent lifetime spectroscopy reveals that these metastable defects have shallow energy levels ~0.12 eV. Their concentrations strongly depend on the ambient gases during TR because of an offset of the thermal equilibrium between vacancies and self-interstitials. However, these metastable defects anneal out at typical cell processing temperatures ≥850°C and have little effect on the bulk lifetime of the processed cell structures. Without dissolving built-in oxygen precipitate nuclei, high-temperature solar cell processing severely degrades the minority carrier lifetimes to below 0.1 millisecond, while TR-treated n-Cz wafers after the cell processing steps exhibit carrier lifetimes above 2.2 milliseconds.

Photovoltaics (PV) can provide power autonomy to sensors and communication devices comprising the Internet of Things (IoT). An outstanding challenge is to create design rules that transform intermittent and non-dispatchable solar energy into persistent, stable, and low-cost power for sensors. These design rules govern optimal system architecture design and optimal power consumption patterns. In previous work, we considered (i) the variability of solar insolation across different time scales (hourly, daily, and seasonal); (ii) the solar cell device characteristics; and (iii) the power consumption of the sensing and communication modules. From these constraints, we described a methodology to calculate the necessary energy storage capacity to reliably power the device over several years. The system size can then be optimized to minimize cost or volume. In this paper, we describe a methodology to improve the reliability of solar-powered IoT devices in the event of outlier conditions (i.e., periods of anomalously low insolation that reduce battery state-of-charge). This theoretical study, based on actual sensor and insolation data, describes how an adaptive power consumption scheme decreases the dimensions of solar cell and battery as well as system cost, assuming flexible operating scheme is allowed. The adaptive power consumption scheme means the data acquisition and transmission rate — which governs the power consumption profile — changes based on availability of stored energy in the battery and recent solar insolation. The results show for 3% reduction in average data transmission, the cost of the power components (i.e. battery and solar panel) can be reduced by 10% and the volume of the battery by 30%. The design is constrained by the available power as well as the minimum expected system performance, using the rate of acquired data from the sensor. We find that implementing an adaptive power consumption scheme based on available battery capacity for solar powered sensor can reduce battery capacity by 90%, while ensuring that data transmission rate occasionally varies but never extinguishes completely.

Impurity contamination in thin-film solar cells remains an uncertain risk due to the little-known impact of impurities on recombination. Building upon previous work, in which we intentionally contaminated lead halide perovskite (LHP) solar cells with iron, we further examine the distribution and charge state of iron-induced defects in LHP films using synchrotron-based X-ray techniques. X-ray absorption measurements suggest that iron-rich regions, which form among iron feedstock concentrations that exceed 100 ppm, most closely resemble the chemistry of Fe2O3. Iron distributed within the bulk may form a mix of Fe2+and Fe3+, the latter of which is not expected to be recombination active, potentially allowing LHPs to incorporate more iron than traditional semiconductors. X-ray beam induced current measurements show little correlation between the presence of iron-rich regions and charge collection, which further suggests low recombination activity at these sites. These results further elucidate the recombination behavior caused by iron incorporation in LHP films, revealing insight into how inhomogeneous incorporation of impurities may mitigate photovoltaic performance degradation., National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (award number DMR-1419807), United States. Department of Energy. Office of Science User Facility (Contract No. DE-AC02-06CH11357), National Science Foundation (U.S.) (NSF EECS Award No. 1541959), Martin Family Society of Fellows for Sustainability, National Science Foundation (U.S.). Graduate Research Fellowship (Grant No. 1122374), National Science Foundation (U.S.). (CA No. EEC-1041895)

Light- and elevated temperature-induced degradation (LeTID) is a detrimental effect observed under operating conditions in p-type multicrystalline silicon (mc-Si) solar cells. In this contribution, we employ synchrotron-based techniques to study the dissolution of precipitates due to different firing processes at grain boundaries in LeTID-affected mc-Si. The synchrotron measurements show clear dissolution of collocated metal precipitates during firing. We compare our observations with degradation behavior in the same wafers. The experimental results are complemented with process simulations to provide insight into the change in bulk point defect concentration due to firing. Several studies have proposed that LeTID is caused by metal-rich precipitate dissolution during contact firing, and we find that the solubility and diffusivity are promising screening metrics to identify metals that are compatible with this hypothesis. While slower and less soluble elements (e.g., Fe and Cr) are not compatible according to our simulations, the point defect concentrations of faster and more soluble elements (e.g., Cu and Ni) increase after a high-temperature firing process, primarily due to emitter segregation rather than precipitate dissolution. These results are a useful complement to lifetime spectroscopy techniques, and can be used to evaluate additional candidates in the search for the root cause of LeTID.

The noncontact crucible (NOC) method was proposed for obtaining Si single bulk crystals with a large diameter and volume using a cast furnace and solar cells with high conversion efficiency and yield. This method has several novel characteristics that originate from its key feature that ingots can be grown inside a Si melt without contact with a crucible wall. Si ingots for solar cells were grown by utilizing the merits resulting from these characteristics. Single ingots with high quality were grown by the NOC method after furnace cleaning, and the minority carrier lifetime was measured to investigate reduction of the number of impurities. A p -type ingot with a convex growth interface in the growth direction was also grown after furnace cleaning. For p -type solar cells prepared using wafers cut from the ingot, the highest and average conversion efficiencies were 19.14% and 19.0%, respectively, which were obtained using the same solar cell structure and process as those employed to obtain a conversion efficiency of 19.1% for a p -type Czochralski (CZ) wafer. Using the cast furnace, solar cells with a conversion efficiency and yield as high as those of CZ solar cells were obtained by the NOC method.

Optimizing photovoltaic (PV) devices requires characterization and optimization across several length scales, from centimeters to nanometers. Synchrotron-based micro-X-ray fluorescence spectromicroscopy (μ-XRF) is a valuable link in the PV-related material and device characterization suite. μ-XRF maps of elemental distributions in PV materials have high spatial resolution and excellent sensitivity and can be measured on absorber materials and full devices. Recently, we implemented on-the-fly data collection (flyscan) at Beamline 2-ID-D at the Advanced Photon Source at Argonne National Laboratory, eliminating a 300 ms per-pixel overhead time. This faster scanning enables high-sensitivity (∼1014 atoms/cm2), large-area (10 000s of μ m 2), high-spatial resolution ( μ m-diameter laser-fired contact of a silicon solar cell before and after lasing. While we focus on μ-XRF of mc-Si wafers for PV, our results apply broadly to synchrotron-based mapping of PV absorbers and devices.

High-throughput testing of solar modules to accurately predict energy yield (EY) is increasingly important as more of the power grid runs on photovoltaics (PV). Modules are sold based on power ratings measured under standard testing conditions, not fully considering environmental conditions of the real world. In this work, we use the k-means algorithm to extract the best representative conditions of the environment that minimizes error in EY. The work presented here is a fully scoped proof-of-concept demonstrated on a year of spectral data clustered and analyzed for every month of 2017 in Boulder, Colorado. Preliminary results demonstrate a decrease in 5 percent relative error in energy yield predictions between one standard testing condition and up to seven clusters found with this method. This can be generalized to more locations around the world as a powerful tool for EY estimation. These results demonstrate the capacity for high throughput, accurate EY prediction using clustered conditions.

Space conditioning, and cooling in particular, is a key factor in human productivity and well-being across the globe. During the 21st century, global cooling demand is expected to grow significantly due to the increase in wealth and population in sunny nations across the globe and the advance of global warming. The same locations that see high demand for cooling are also ideal for electricity generation via photovoltaics (PV). Despite the apparent synergy between cooling demand and PV generation, the potential of the cooling sector to sustain PV generation has not been assessed on a global scale. Here, we perform a global assessment of increased PV electricity adoption enabled by the residential cooling sector during the 21st century. Already today, utilizing PV production for cooling could facilitate an additional installed PV capacity of approximately 540 GW, more than the global PV capacity of today. Using established scenarios of population and income growth, as well as accounting for future global warming, we further project that the global residential cooling sector could sustain an added PV capacity between 20-200 GW each year for most of the 21st century, on par with the current global manufacturing capacity of 100 GW. Furthermore, we find that without storage, PV could directly power approximately 50% of cooling demand, and that this fraction is set to increase from 49% to 56% during the 21st century, as cooling demand grows in locations where PV and cooling have a higher synergy. With this geographic shift in demand, the potential of distributed storage also grows. We simulate that with a 1 m3 water-based latent thermal storage per household, the fraction of cooling demand met with PV would increase from 55% to 70% during the century. These results show that the synergy between cooling and PV is notable and could significantly accelerate the growth of the global PV industry.

Neutron imaging provides a route for studying the effect of environmental conditions on enzymatic electrochemical cell (EEC) performance. Here, the application of 2D and 3D neutron imaging is demonstrated as a means to investigate effects of environmental conditions on EEC performance. Changes in aqueous solutions that are vital to the operation of EECs have been directly observed in real time using neutron radiography (NR). These changes include uptake of aqueous solutions in electrode materials and in situ observation of water content during operation. The EEC structure has also been observed using ex situ neutron tomography. Initially samples constructed to simulate EEC geometry were imaged, and aqueous buffer solution uptake behavior was observed in carbon paper cell components. In follow-on studies neutron tomography was used to map regions of enzyme catalyst inks, defining active regions within the EEC electrode. The higher neutron attenuation of polymeric ink components enables this observation. Finally, in situ imaging of a prototype EEC pouch cell was performed using a standard chronoamperometry arrangement while performing real time neutron radiography. Neutron radiographs acquired during operation show a clear variation in transmission behavior, primarily due to drying. Together these studies demonstrate the applicability and attendant challenges of neutron imaging for the study of EEC performance and reliability.

Recent progress in the electronic quality of high-performance (HP) multicrystalline silicon material is reported with measurements and modeling performed at various institutions and research groups. It is shown that recent progress has been made in the fabrication at Trina Solar mainly by improving the high excess carrier lifetimes τ due to a considerable reduction of mid-gap states. However, the high lifetimes in the wafers are still reduced by interstitial iron by a factor of about 10 at maximum power point (mpp) conditions compared to mono-crystalline Cz wafers of equivalent resistivity. The low lifetime areas of the wafers seem to be limited by precipitates, most likely Cu. Through simulations, it appears that dislocations reduce cell efficiency by about 0.25% absolute. The best predictors for PERC cell efficiency from ingot metrology are a combination of mean lifetime and dislocation density because dislocations cannot be improved considerably by gettering during cell processing, while lifetime-limiting impurities are gettered well. In future, the material may limit cell efficiency above about 22.5% if the concentrations of Fe and Cu remain above 1010 and 1013 cm-3, respectively, and if dislocations are not reduced further.

In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity. Published by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. Locked until 1.1.2019 due to copyright restrictions. The following article appeared in Journal of Applied Physics and may be found at https://aip.scitation.org/doi/full/10.1063/1.5018797

The relationship between charge-carrier lifetime and the tolerance of lead halide perovskite (LHP) solar cells to intrinsic point defects has drawn much attention by helping to explain rapid improvements in device efficiencies. However, little is known about how charge-carrier lifetime and solar cell performance in LHPs are affected by extrinsic defects (i.e., impurities), including those that are common in manufacturing environments and known to introduce deep levels in other semiconductors. Here, we evaluate the tolerance of LHP solar cells to iron introduced via intentional contamination of the feedstock and examine the root causes of the resulting efficiency losses. We find that comparable efficiency losses occur in LHPs at feedstock iron concentrations approximately 100 times higher than those in p-type silicon devices. Photoluminescence measurements correlate iron concentration with nonradiative recombination, which we attribute to the presence of deep-level iron interstitials, as calculated from first-principles, as well as iron-rich particles detected by synchrotron-based X-ray fluorescence microscopy. At moderate contamination levels, we witness prominent recovery of device efficiencies to near-baseline values after biasing at 1.4 V for 60 s in the dark. We theorize that this temporary effect arises from improved charge-carrier collection enhanced by electric fields strengthened from ion migration toward interfaces. Our results demonstrate that extrinsic defect tolerance contributes to high efficiencies in LHP solar cells, which inspires further investigation into potential large-scale manufacturing cost savings as well as the degree of overlap between intrinsic and extrinsic defect tolerance in LHPs and "perovskite-inspired" lead-free stable alternatives.

Over one fourth of all monocrystalline silicon ingots suffer from a 20% performance degradation due to oxygen precipitates. Tabula Rasa (TR) is a mitigation technique that dissolves these precipitates, making them harmless. This work explores the dependence of oxygen dissolution on annealing time and temperature for the TR process to aid in solar cell process optimization. The dissolution time for oxygen precipitates was found to be more than 10 minutes for total dissolution, longer than normal TR process times in the electronics industry. The activation energy, extracted from the precipitate dissolution curves, is found to be 2.6±0.5 eV. This value when compared to the migration enthalpy of oxygen in silicon can be used to reveal the energy limiting proces in TR.

The air-conditioning (AC) sector offers an interesting synergy for photovoltaic (PV) electricity generation, because the demand for AC correlates with ideal times and locations for PV production. The AC sector is also a significant electricity consumer, currently comprising ~3 % of global electricity consumption and it is expected to grow rapidly in the future due to income and population growth in sunny countries as well as global warming. Here, we assess the potential of the residential AC sector to sustain and accelerate PV industry growth during the 21st century. We show that the residential AC sector could sustain more installed PV generation capacity than the current global PV manufacturing capacity could produce. We highlight other possible synergistic electricity consumption sectors with significant growth expected in the future.

Temperature- and injection-dependent lifetime spectroscopy (TIDLS) is employed to study the defect responsible for light- and elevated temperature-induced degradation (LeTID). In our previous analyses, titanium (Ti), molybdenum (Mo), and tungsten (W) were identified as potential candidates for LeTID. The addition of temperature dependence further constrains the defect parameters. Assuming constant defect parameters with temperature, we identify two possible sets of defect parameters: $k \pmb{=23.9+5.5}$ at $E_{\mathrm{t}}-E_{\mathrm{i}}=_{-}0.21\pm 0.06\mathrm{eV}$ and $k=23.5\pm 5.6$ at $E_{t-}E_{i}= \pmb{-0.10\pm0.07 \mathbf{eV}}$ . We consider our results in the context of published defect parameters identified by TIDLS in other LeTID samples, and we evaluate our results against reported defect parameter temperature dependencies for Ti and Mo. We conclude that Mo is most consistent with our measurements. Approaches beyond lifetime spectroscopy, including intentional contamination and chemical composition measurements, are required to determine the root cause of LeTID.

The root cause of light- and elevated temperature-induced degradation (LeTID) in multicrystalline silicon p-type passivated emitter and rear cell (PERC) devices is still unknown. Some researchers hypothesize that high temperature firing processes dissolve metal-rich precipitates which can then participate in LeTID. To address this hypothesis, synchrotron-based X-ray techniques, including fluorescence and absorption near-edge spectroscopy, are employed. In as-grown industrial material, we observe collocated copper- and nickel-rich precipitates, which persist after firing and are below the detection limit after phosphorous diffusion. We conclude that precipitates decrease in size due to the firing process and that this may result in an increase in bulk interstitial metal concentration. We further employ microphotoluminescence at a grain versus grain boundary to highlight similarities and possible differences in degradation and regeneration behavior.

In industrial silicon solar cells, oxygen-related defects lower device efficiencies by up to 20% (rel.). In order to mitigate these defects, a high-temperature homogenization anneal called tabula rasa (TR) that has been used in the electronics industry is now proposed for use in solar-grade wafers. This work addresses the kinetics of tabula rasa by elucidating the activation energy governing oxide precipitate dissolution, which is found to be 2.6 ± 0.5 eV. This value is consistent within uncertainty to the migration enthalpy of oxygen interstitials in silicon, implying TR to be kinetically limited by oxygen point-defect diffusion. This large activation energy is observed to limit oxygen precipitate dissolution during standard TR conditions, suggesting that more aggressive annealing conditions than conventionally used are required for complete bulk microdefect mitigation.

Thinner silicon wafers are a pathway to lower cost without compromising the efficiency of solar cells. In this work, we study the recombination mechanism for thin and thick silicon heterojunction solar cells, and we discuss the potential of using more defective material to manufacture high performance thin solar cells. Modelling the performance of silicon heterojunction solar cells indicates that at open-circuit voltage the recombination is dominated by Auger and surface, representing nearly 90% of the total recombination. At maximum power point, the surface is responsible for 50 to 80% of the overall recombination, and its contribution increases inversely with the wafer thickness. The expe rimental results show that for lower quality CZ material with 1 ms bulk lifetime, 60 μm-thick cells perform better than 170 μm-thick cells. The potential efficiency gain is 1% absolute. The gains in voltage of using thinner wafers are significantly higher for the lower quality CZ material, 25 mV, than for standard CZ material,10 mV., National Science Foundation (U.S.), United States. Department of Energy (CA No. EEC-1041895), National Science Foundation (U.S.). Graduate Research Fellowship, Spain. Ministry of Economy and Competitiveness (project ENE2014-56069-C4-2-R), United States. Department of Defense (DODRIF13-OEPP01-P-0020)

Synchrotron-based μ-XRF is a powerful tool to measure elemental distributions non-destructively with high spatial resolution and excellent sensitivity. Recently, we implemented on-the-fly data collection (flyscan) at Beamline 2-ID-D at the Advanced Photon Source at Argonne National Laboratory, making data acquisition faster than 300 ms per pixel practical. We show that flyscan mode at Beamline 2-ID-D enables (a) traditional elemental maps to be completed twenty times more quickly while maintaining reasonably high sensitivity, and (b) practical studies of materials with an order of magnitude lower total impurity concentration and sparser spatial density of impurities. We highlight opportunities for flyscan to enable qualitatively new forms of microscopy, leveraging the accelerated data-acquisition rate for multi-dimensional mapping.

The present study provides an assessment of the bleaching response of corals at Baker and Howland Islands (central Pacific) following the 2009-2010 El Nino-Southern Oscillation event. Nearly 35% of colonies belonging to 17 coral genera surveyed within belt transects exhibited bleaching, predominantly along east Howland Island and east and northeast Baker Island, and within the 10-18 m isobaths. Bleaching conditions differed among coral taxa, with Pocillopora, Acropora, and Fungia exhibiting the greatest percentage of affected colonies, followed by Pavona, Porites, and Psammocora; Montipora appeared to be the most resistant to bleaching with < 2.5% of colonies affected. Colony size had direct effects on bleaching responses for Acropora, Pavona, and Pocillopora, with bleached colonies exhibiting greater mean diameters than unbleached corals; mixed effects were observed for Fungia, Porites, and Psammocora. Bleaching extent was also affected by colony size, but only in Acropora; the lack of differences in the other study corals is probably due to the high variability in the extent of bleaching within taxa. In situ subsurface loggers indicated that seawater temperatures increased steadily throughout 2009, peaking at 31.2 °c in early November, and remaining above the coral bleaching threshold (29.7 °c) beyond the time when instruments were recovered on 7 February, 2010. This is the first documented mass bleaching episode at baker and Howland Islands; however, anecdotal evidence suggests recurrent, widespread bleaching may be a principal source of disturbance, affecting coral reef species composition and structural dynamics at Howland and Baker over multi-year timescales.

Serratia marcescens is an enteric bacterium that causes white pox disease in elkhorn coral, Acropora palmata; however, it remains unclear if the pathogenic strain has adapted to seawater or if it requires a host or reservoir for survival. To begin to address this fundamental issue, the persistence of strain PDL100 was compared among seawater and coral mucus microcosms. Median survival time across all conditions ranged from a low of 15 h in natural seawater [with a first-order decay constant (k) = -0.173] at 30°C to a maximum of 120 h in glucose-amended A. palmata mucus (k = -0.029) at 30°C. Among seawater and mucus microcosms, median survival time was significantly greater within Siderastrea siderea mucus compared with seawater or mucus of Montastraea faveolata or A. palmata (P < 0.0001). In seawater, the addition of phosphate and especially glucose resulted in significant improvements in survival (P < 0.001), while only the addition of glucose resulted in significant improvement in survival in A. palmata mucus (P < 0.0001). Increasing the temperature of seawater to 35°C resulted in a significantly slower decay than that observed at 30°C (P < 0.0001). The results of this study indicate that PDL100 is not well-adapted to marine water; however, survival can be improved by increasing temperature, the availability of coral mucus from S. siderea and most notably the presence of dissolved organic carbon.

Caribbean elkhorn coral, Acropora palmata, has been decimated in recent years, resulting in the listing of this species as threatened under the United States Endangered Species Act. A major contributing factor in the decline of this iconic species is white pox disease. In 2002, we identified the faecal enterobacterium, Serratia marcescens, as an etiological agent for white pox. During outbreaks in 2003 a unique strain of S. marcescens was identified in both human sewage and white pox lesions. This strain (PDR60) was also identified from corallivorious snails (Coralliophila abbreviata), reef water, and two non-acroporid coral species, Siderastrea siderea and Solenastrea bournoni. Identification of PDR60 in sewage, diseased Acropora palmata and other reef invertebrates within a discrete time frame suggests a causal link between white pox and sewage contamination on reefs and supports the conclusion that humans are a likely source of this disease.

Serratia marcescens is an enteric bacterium that causes white pox disease in elkhorn coral, Acropora palmata; however, it remains unclear if the pathogenic strain has adapted to seawater or if it requires a host or reservoir for survival. To begin to address this fundamental issue, the persistence of strain PDL100 was compared among seawater and coral mucus microcosms. Median survival time across all conditions ranged from a low of 15 h in natural seawater [with a first-order decay constant (k) = -0.173] at 30°C to a maximum of 120 h in glucose-amended A. palmata mucus (k = -0.029) at 30°C. Among seawater and mucus microcosms, median survival time was significantly greater within Siderastrea siderea mucus compared with seawater or mucus of Montastraea faveolata or A. palmata (P0.0001). In seawater, the addition of phosphate and especially glucose resulted in significant improvements in survival (P0.001), while only the addition of glucose resulted in significant improvement in survival in A. palmata mucus (P0.0001). Increasing the temperature of seawater to 35°C resulted in a significantly slower decay than that observed at 30°C (P0.0001). The results of this study indicate that PDL100 is not well-adapted to marine water; however, survival can be improved by increasing temperature, the availability of coral mucus from S. siderea and most notably the presence of dissolved organic carbon.

Caribbean elkhorn coral, Acropora palmata, has been decimated in recent years, resulting in the listing of this species as threatened under the United States Endangered Species Act. A major contributing factor in the decline of this iconic species is white pox disease. In 2002, we identified the faecal enterobacterium, Serratia marcescens, as an etiological agent for white pox. During outbreaks in 2003 a unique strain of S. marcescens was identified in both human sewage and white pox lesions. This strain (PDR60) was also identified from corallivorious snails (Coralliophila abbreviata), reef water, and two non-acroporid coral species, Siderastrea siderea and Solenastrea bournoni. Identification of PDR60 in sewage, diseased Acropora palmata and other reef invertebrates within a discrete time frame suggests a causal link between white pox and sewage contamination on reefs and supports the conclusion that humans are a likely source of this disease.