Corals survive severe bleaching event in refuges related to taxa, colony size, and water depth

Marine heatwaves are increasing in frequency and duration, threatening tropical reef ecosystems through intensified coral bleaching events. We examined a strikingly variable spatial pattern of bleaching in Moorea, French Polynesia following a heatwave that lasted from November 2018 to July 2019. In July 2019, four months after the onset of bleaching, we surveyed > 5000 individual colonies of the two dominant coral genera, Pocillopora and Acropora, at 10 m and 17 m water depths, at six forereef sites around the island where temperature was measured. We found severe bleaching increased with colony size for both coral genera, but Acropora bleached more severely than Pocillopora overall. Acropora bleached more at 10 m than 17 m, likely due to higher light availability at 10 m compared to 17 m, or greater daily temperature fluctuation at depth. Bleaching in Pocillopora corals did not differ with depth but instead varied with the interaction of colony size and Accumulated Heat Stress (AHS), in that larger colonies (> 30 cm) were more sensitive to AHS than mid-size (10-29 cm) or small colonies (5-9 cm). Our findings provide insight into complex interactions among coral taxa, colony size, and water depth that produce high spatial variation in bleaching and related coral mortality.

Regional differences in fishing behavior determine whether a marine reserve network enhances fishery yield

A network of marine reserves can enhance yield in depleted fisheries by protecting populations, particularly large, old spawners that supply larvae for interspersed fishing grounds. The ability of marine reserves to enhance sustainable fisheries is much less evident. We report empirical evidence of a marine reserve network improving yield regionally for a sustainable spiny lobster fishery, apparently through the spillover of adult lobsters and behavioral adaptation by the fishing fleet. Results of a Before-After, Control-Impact analysis found catch, effort, and Catch-Per-Unit Effort increased after the establishment of marine reserves in the northern region of the fishery where fishers responded by fishing intensively at reserve borders, but declined in the southern region where they vacated once productive fishing grounds. The adaptation of the northern region of the fishery may have been aided by a history of collaboration between fishers, scientists, and managers, highlighting the value of collaborative research and education programs for preparing fisheries to operate productively within a seascape that includes a large marine reserve network.

Aging of Copper Nanoparticles in the Marine Environment Regulates Toxicity for a Coastal Phytoplankton Species

Environmental conditions in aquatic ecosystems transform toxic chemicals over time, influencing their bioavailability and toxicity. Using an environmentally relevant methodology, we tested how exposure to seawater for 1-15 weeks influenced the accumulation and toxicity of copper nanoparticles (nano-Cu) in a marine phytoplankton species. Nano-Cu rapidly agglomerated in seawater and then decreased in size due to Cu dissolution. Dissolution rates declined during weeks 1-4 and remained low until 15 weeks, when the large agglomerates that had formed began to rapidly dissolve again. Marine phytoplankton species were exposed for 5-day periods to nano-Cu aged from 1 to 15 weeks at concentrations from 0.01 to 20 ppm. Toxicity to phytoplankton, measured as change in population growth rate, decreased significantly with particle aging from 0 to 4 weeks but increased substantially in the 15-week treatment due apparently to elevated Cu dissolution of reagglomerated particles. Results indicate that the transformation, fate, and toxicity of nano-Cu in marine ecosystems are influenced by a highly dynamic physicochemical aging process.

Coral reef structural complexity loss exposes coastlines to waves

Coral reefs offer natural coastal protection by attenuating incoming waves. Here we combine unique coral disturbance-recovery observations with hydrodynamic models to quantify how structural complexity dissipates incoming wave energy. We find that if the structural complexity of healthy coral reefs conditions is halved, extreme wave run-up heights that occur once in a 100-years will become 50 times more frequent, threatening reef-backed coastal communities with increased waves, erosion, and flooding.

Size-dependent mortality of corals during marine heatwave erodes recovery capacity of a coral reef

For many long-lived taxa, such as trees and corals, older, and larger individuals often have the lowest mortality and highest fecundity. However, climate change-driven disturbances such as droughts and heatwaves may fundamentally alter typical size-dependent patterns of mortality and reproduction in these important foundation taxa. Working in Moorea, French Polynesia, we investigated how a marine heatwave in 2019, one of the most intense marine heatwaves at our sites over the past 30 years, drove patterns of coral bleaching and mortality. The marine heatwave drove island-wide mass coral bleaching that killed up to 76% and 65% of the largest individuals of the two dominant coral genera, Pocillopora and Acropora, respectively. Colonies of Pocillopora and Acropora ≥30 cm diameter were ~3.5× and ~1.3×, respectively, more likely to die than colonies <30-cm diameter. Typically, annual mortality in these corals is concentrated on the smallest size classes. Yet, this heatwave dramatically reshaped this pattern, with heat stress disproportionately killing larger coral colonies and equalizing annual mortality rates across the size spectrum. This shift in the size-mortality relationship reduced the overall fecundity of these genera by >60% because big corals are disproportionately important for reproduction on reefs. Additionally, the survivorship of microscopic coral recruits, critical for the recovery of corals following disturbances, declined to 2%, over an order of magnitude lower compared to a year without elevated thermal stress, where 33% of coral recruits survived. While other research has shown that larger corals can bleach more frequently than smaller corals, we show the severe impact this phenomenon can have at the reef-wide scale. As marine heatwaves become more frequent and intense, disproportionate mortality of the largest, most fecund corals and near-complete loss of entire cohorts of newly-settled coral recruits will likely reduce the recovery capacity of these iconic ecosystems.

Juvenile corals underpin coral reef carbonate production after disturbance

Sea-level rise is predicted to cause major damage to tropical coastlines. While coral reefs can act as natural barriers for ocean waves, their protection hinges on the ability of scleractinian corals to produce enough calcium carbonate (CaCO₃ ) to keep up with rising sea levels. As a consequence of intensifying disturbances, coral communities are changing rapidly, potentially reducing community-level CaCO₃ production. By combining colony-level physiology and long-term monitoring data, we show that reefs recovering from major disturbances can produce 40% more CaCO₃ than currently estimated due to the disproportionate contribution of juvenile corals. However, the buffering effect of highly productive juvenile corals is compromised by recruitment failures, which have been more frequently observed after large-scale, repeated bleaching events. While the size structure of corals can bolster a critical ecological function on reefs, climate change impacts on recruitment may undermine this buffering effect, thus further compromising the persistence of reefs and their provision of important ecosystem services.

Evidence that spillover from Marine Protected Areas benefits the spiny lobster (Panulirus interruptus) fishery in southern California

Marine Protected Areas (MPAs) are designed to enhance biodiversity and ecosystem services. Some MPAs are also established to benefit fisheries through increased egg and larval production, or the spillover of mobile juveniles and adults. Whether spillover influences fishery landings depend on the population status and movement patterns of target species both inside and outside of MPAs, as well as the status of the fishery and behavior of the fleet. We tested whether an increase in the lobster population inside two newly established MPAs influenced local catch, fishing effort, and catch-per-unit-effort (CPUE) within the sustainable California spiny lobster fishery. We found greater build-up of lobsters within MPAs relative to unprotected areas, and greater increases in fishing effort and total lobster catch, but not CPUE, in fishing zones containing MPAs vs. those without MPAs. Our results show that a 35% reduction in fishing area resulting from MPA designation was compensated for by a 225% increase in total catch after 6-years, thus indicating at a local scale that the trade-off of fishing ground for no-fishing zones benefitted the fishery.

Conventional and nano-copper pesticides are equally toxic to the estuarine amphipod Leptocheirus plumulosus

Modern nano-engineered pesticides have great promise for agriculture due to their extended, low dose release profiles that are intended to increase effectiveness but reduce environmental harm. Whether nanopesticides, including copper (Cu) formulations, cause reduced levels of toxicity to non-target aquatic organisms is unclear but important to assess. Predicting how aquatic species respond to incidental exposure to Cu-based nanopesticides is challenging because of the expected very low concentrations in the environment, and the two forms of exposure that may occur, namely to Cu ions and Cu nanoparticles. We conducted Cu speciation, tissue uptake, and 7-day toxicity laboratory experiments to test how a model estuarine organism, the amphipod Leptocheirus plumulosus, responded to two popular Cu-based nanopesticides, CuPRO and Kocide, and conventional CuCl₂. Exposure concentrations ranged from 0 to 2.5 ppm, which were similar to those found in estuarine water located downstream of agricultural fields. Cu dissolution rates were much slower for the nanopesticides than the ionic formula, and Cu body burden in amphipods increased approximately linearly with the nominal exposure concentration. Amphipod survival declined in a normal dose-response manner with no difference among Cu formulations. Growth and movement rates after 7 days revealed no difference among exposure levels when analyzed with conventional statistical methods. By contrast, analysis of respiration rates, inferred from biomass measurements, with a bioenergetic toxicodynamic model indicated potential for population-level effects of exposure to very low-levels of the two nanopesticides, as well as the control contaminant CuCl₂. Our results indicate that toxicity assessment of environmental trace pollutant concentrations may go undetected with traditional ecotoxicological tests. We present a process integrating toxicity test results and toxicodynamic modeling that can improve our capacity to detect and predict environmental impacts of very low levels of nanomaterials released into the environment.

Perceptions and responses of Pacific Island fishers to changing coral reefs

The transformation of coral reefs has profound implications for millions of people. However, the interactive effects of changing reefs and fishing remain poorly resolved. We combine underwater surveys (271 000 fishes), catch data (18 000 fishes), and household surveys (351 households) to evaluate how reef fishes and fishers in Moorea, French Polynesia responded to a landscape-scale loss of coral caused by sequential disturbances (a crown-of-thorns sea star outbreak followed by a category 4 cyclone). Although local communities were aware of the disturbances, less than 20% of households reported altering what fishes they caught or ate. This contrasts with substantial changes in the taxonomic composition in the catch data that mirrored changes in fish communities observed on the reef. Our findings highlight that resource users and scientists may have very different interpretations of what constitutes 'change' in these highly dynamic social-ecological systems, with broad implications for successful co-management of coral reef fisheries.

Photosynthetic efficiency predicts toxic effects of metal nanomaterials in phytoplankton

High Throughput Screening (HTS) using in vitro assessments at the subcellular level has great promise for screening new chemicals and emerging contaminants to identify high-risk candidates, but their linkage to ecological impacts has seldom been evaluated. We tested whether a battery of subcellular HTS tests could be used to accurately predict population-level effects of engineered metal nanoparticles (ENPs) on marine phytoplankton, important primary producers that support oceanic food webs. To overcome well-known difficulties of estimating ecologically meaningful toxicity parameters, we used novel Dynamic Energy Budget and Toxicodynamic (DEBtox) modeling techniques to evaluate impacts of ENPs on population growth rates. Our results show that population growth was negatively impacted by all four ENPs tested, but the HTS tests assessing many cell/physiological functions lacked predictive power at the population level. However, declining photosynthetic efficiency, a traditional physiological endpoint for photoautotrophs, was a good predictor of population level effects in phytoplankton. DEBtox techniques provided robust estimates of EC₁₀ for population growth rates in exponentially growing batch cultures of phytoplankton, and should be widely useful for ecotoxicological testing. Adoption of HTS approaches for ecotoxicological assessment should carefully evaluate the predictive power of specific assays to minimize the risk that effects at higher levels of biological organization may go undetected.

Considerations of Environmentally Relevant Test Conditions for Improved Evaluation of Ecological Hazards of Engineered Nanomaterials

Engineered nanomaterials (ENMs) are increasingly entering the environment with uncertain consequences including potential ecological effects. Various research communities view differently whether ecotoxicological testing of ENMs should be conducted using environmentally relevant concentrations-where observing outcomes is difficult-versus higher ENM doses, where responses are observable. What exposure conditions are typically used in assessing ENM hazards to populations? What conditions are used to test ecosystem-scale hazards? What is known regarding actual ENMs in the environment, via measurements or modeling simulations? How should exposure conditions, ENM transformation, dose, and body burden be used in interpreting biological and computational findings for assessing risks? These questions were addressed in the context of this critical review. As a result, three main recommendations emerged. First, researchers should improve ecotoxicology of ENMs by choosing test end points, duration, and study conditions-including ENM test concentrations-that align with realistic exposure scenarios. Second, testing should proceed via tiers with iterative feedback that informs experiments at other levels of biological organization. Finally, environmental realism in ENM hazard assessments should involve greater coordination among ENM quantitative analysts, exposure modelers, and ecotoxicologists, across government, industry, and academia.

Fishing diseased abalone to promote yield and conservation

Past theoretical models suggest fishing disease-impacted stocks can reduce parasite transmission, but this is a good management strategy only when the exploitation required to reduce transmission does not overfish the stock. We applied this concept to a red abalone fishery so impacted by an infectious disease (withering syndrome) that stock densities plummeted and managers closed the fishery. In addition to the non-selective fishing strategy considered by past disease-fishing models, we modelled targeting (culling) infected individuals, which is plausible in red abalone because modern diagnostic tools can determine infection without harming landed abalone and the diagnostic cost is minor relative to the catch value. The non-selective abalone fishing required to eradicate parasites exceeded thresholds for abalone sustainability, but targeting infected abalone allowed the fishery to generate yield and reduce parasite prevalence while maintaining stock densities at or above the densities attainable if the population was closed to fishing. The effect was strong enough that stock and yield increased even when the catch was one-third uninfected abalone. These results could apply to other fisheries as the diagnostic costs decline relative to catch value.

Impacts of Silver Nanoparticles on a Natural Estuarine Plankton Community

Potential effects of metal nanoparticles on aquatic organisms and food webs are hard to predict from the results of single-species tests under controlled laboratory conditions, and more realistic exposure experiments are rarely conducted. We tested whether silver nanoparticles (Ag NPs) had an impact on zooplankton grazing on their prey, specifically phytoplankton and bacterioplankton populations. If Ag NPs directly reduced the abundance of prey, thereby causing the overall rate of grazing by their predators to decrease, a cascading effect on a planktonic estuarine food web would be seen. Our results show that the growth rates of both phytoplankton and bacterioplankton populations were significantly reduced by Ag NPs at concentrations of ≥500 μg L(-1). At the same time, grazing rates on these populations tended to decline with exposure to Ag NPs. Therefore, Ag NPs did not cause a cascade of effects through the food web but impacted a specific trophic level. Photosynthetic efficiency of the phytoplankton was significantly reduced at Ag NPs concentrations of ≥500 μg L(-1). These effects did not occur at relatively low concentrations of Ag that are often toxic to single species of bacteria and other organisms, suggesting that the impacts of Ag NP exposure may not be apparent at environmentally relevant concentrations due to compensatory processes at the community level.

Species sensitivity distributions for engineered nanomaterials

Engineered nanomaterials (ENMs) are a relatively new strain of materials for which little is understood about their impacts. A species sensitivity distribution (SSDs) is a cumulative probability distribution of a chemical's toxicity measurements obtained from single-species bioassays of various species that can be used to estimate the ecotoxicological impacts of a chemical. The recent increase in the availability of acute toxicity data for ENMs enabled the construction of 10 ENM-specific SSDs, with which we analyzed (1) the range of toxic concentrations, (2) whether ENMs cause greater hazard to an ecosystem than the ionic or bulk form, and (3) the key parameters that affect variability in toxicity. The resulting estimates for hazardous concentrations at which 5% of species will be harmed ranged from <1 ug/L for PVP-coated n-Ag to >3.5 mg/L for CNTs. The results indicated that size, formulation, and the presence of a coating can alter toxicity, and thereby corresponding SSDs. Few statistical differences were observed between SSDs of an ENM and its ionic counterpart. However, we did find a significant correlation between the solubility of ENMs and corresponding SSD. Uncertainty in SSD values can be reduced through greater consideration of ENM characteristics and physiochemical transformations in the environment.

Cellular partitioning of nanoparticulate versus dissolved metals in marine phytoplankton

Discharges of metal oxide nanoparticles into aquatic environments are increasing with their use in society, thereby increasing exposure risk for aquatic organisms. Separating the impacts of nanoparticle from dissolved metal pollution is critical for assessing the environmental risks of the rapidly growing nanomaterial industry, especially in terms of ecosystem effects. Metal oxides negatively affect several species of marine phytoplankton, which are responsible for most marine primary production. Whether such toxicity is generally due to nanoparticles or exposure to dissolved metals liberated from particles is uncertain. The type and severity of toxicity depends in part on whether phytoplankton cells take up and accumulate primarily nanoparticles or dissolved metal ions. We compared the responses of the marine diatom, Thalassiosira weissflogii, exposed to ZnO, AgO, and CuO nanoparticles with the responses of T. weissflogii cells exposed to the dissolved metals ZnCl2, AgNO3, and CuCl2 for 7 d. Cellular metal accumulation, metal distribution, and algal population growth were measured to elucidate differences in exposure to the different forms of metal. Concentration-dependent metal accumulation and reduced population growth were observed in T. weissflogii exposed to nanometal oxides, as well as dissolved metals. Significant effects on population growth were observed at the lowest concentrations tested for all metals, with similar toxicity for both dissolved and nanoparticulate metals. Cellular metal distribution, however, markedly differed between T. weissflogii exposed to nanometal oxides versus those exposed to dissolved metals. Metal concentrations were highest in the algal cell wall when cells were exposed to metal oxide nanoparticles, whereas algae exposed to dissolved metals had higher proportions of metal in the organelle and endoplasmic reticulum fractions. These results have implications for marine plankton communities as well as higher trophic levels, since metal may be transferred from phytoplankton through food webs vis à vis grazing by zooplankton or other pathways.

Common strategies and technologies for the ecosafety assessment and design of nanomaterials entering the marine environment

The widespread use of engineered nanomaterials (ENMs) in a variety of technologies and consumer products inevitably causes their release into aquatic environments and final deposition into the oceans. In addition, a growing number of ENM products are being developed specifically for marine applications, such as antifouling coatings and environmental remediation systems, thus increasing the need to address any potential risks for marine organisms and ecosystems. To safeguard the marine environment, major scientific gaps related to assessing and designing ecosafe ENMs need to be filled. In this Nano Focus, we examine key issues related to the state-of-the-art models and analytical tools being developed to understand ecological risks and to design safeguards for marine organisms.

Deposition of carbon nanotubes by a marine suspension feeder revealed by chemical and isotopic tracers

Carbon nanotubes (CNTs) are one of the few truly novel nanomaterials and are being incorporated into a wide range of products, which will lead to environmental release and potential ecological impacts. We examined the toxicity of CNTs to marine mussels and the effect of mussels on CNT fate and transport by exposing mussels to 1, 2, or 3mg CNTsl(-1) for four weeks and measuring mussel clearance rate, shell growth, and CNT accumulation in tissues and deposition in biodeposits. We used metal impurities and carbon stable isotope ratios of the CNTs as tracers of CNT accumulation. Mussels decreased clearance rate of phytoplankton by 24% compared with control animals when exposed to CNTs. However, mussel growth rate was unaffected by CNT concentrations up to 3mgl(-1). Based on metal concentrations and carbon stable isotope values, mussels deposited most CNTs in biodeposits, which contained >110mg CNTsg(-1) dry weight, and accumulated about 1mg CNTsg(-1) dry weight of tissue. We conclude that extremely high concentrations of CNTs are needed to illicit a toxic response in mussels but the ability of mussels to concentrate and deposit CNTs in feces and pseudofeces may impact infaunal organisms living in and around mussel beds.

Accumulation and Toxicity of Copper Oxide Engineered Nanoparticles in a Marine Mussel

Cu is an essential trace element but can be highly toxic to aquatic organisms at elevated concentrations. Greater use of CuO engineered nanoparticles (ENPs) may lead to increased concentrations of CuO ENPs in aquatic environments causing potential ecological injury. We examined the toxicity of CuO ENPs to marine mussels and the influence of mussels on the fate and transport of CuO ENPs. We exposed marine mussels to 1, 2, or 3 mg L^-1 CuO ENPs for four weeks, and measured clearance rate, rejection, excretion and accumulation of Cu, and mussel shell growth. Mussel clearance rate was 48% less, and growth was 68% less, in mussels exposed to 3 mg L^-1 than in control animals. Previous studies show 100% mortality at 1 mg Cu L^-1, suggesting that CuO ENPs are much less toxic than ionic Cu, probably due to the slow dissolution rate of the ENPs. Mussels rejected and excreted CuO ENPs in biodeposits containing as much as 110 mg Cu g^-1, suggesting the potential for magnification in sediments. Mussels exposed to 3 mg L^-1 CuO ENPs accumulated 79.14 ± 12.46 µg Cu g^-1 dry weight, which was 60 times more Cu than in control animals. Our results suggest that mussels have the potential to influence the fate and transport of CuO ENPs and potentially cause magnification of CuO ENPs in mussel bed communities, creating a significant source of Cu to marine benthos.

Effects and implications of trophic transfer and accumulation of CeO2 nanoparticles in a marine mussel

Bivalves are hypothesized to be key organisms in the fate and transport of engineered nanomaterials (ENMs) in aquatic environments due to their ability to filter and concentrate particles from water, but how different exposure pathways influence their interactions with ENMs is not well understood. In a five-week experiment, we tested how interactions between CeO2 ENMs and a marine mussel, Mytilus galloprovincialis, are affected through two exposure methods, direct and through sorption to phytoplankton. We found that phytoplankton sorbed ENMs in <1 h. The exposure methods used did not result in significantly different mussel tissue or pseudofeces Ce concentrations. Approximately 99% of CeO2 was captured and excreted in pseudofeces and average pseudofeces mass doubled in response to CeO2 exposure. Final mean dry tissue Ce concentration (±SE) for treatments exposed to 3 mg L(-1) CeO2 directly was 33 ± 9 μg g(-1) Ce, and 0 ± 0, 19 ± 4, 21 ± 3, and 28 ± 5 μg g(-1) for treatments exposed to 0, 1, 2, and 3 mg L(-1) CeO2 sorbed to phytoplankton. Clearance rates increased with CeO2 concentration but decreased over time in groups exposed to CeO2 directly, indicating stress. These results show the feedback between ENM toxicity and transport and the likelihood of biological mediation in the fate and transport of ENMs in aquatic environments.

Fishery management priorities vary with self‐recruitment in sedentary marine populations

Fisheries science often uses population models that assume no external recruitment, but nearshore marine populations harvested on small scales of <200 km often exhibit an unknown mix of self-recruitment and recruitment from external sources. Since empirical determination of self-recruitment vs. external recruitment is difficult, we used a modeling approach to examine the sensitivity of fishery management priorities to recruitment assumptions (self [closed], external [open]) in a local population of harvested giant clams (Tridacna maxima) on Mo'orea, French Polynesia. From 2006 to 2010, we measured growth, fecundity, recruitment, and survival (resulting from natural and fishing mortality). We used these data to parameterize both a closed (complete self-recruitment) and an open (no self-recruitment) integral projection model (IPM), and then calculated elasticities of demographic rates (growth, survival, recruitment) to future population abundance in 20 years. The models' lowest projected abundance was 93.4% (95% CI, [86.5%, 101.8%]) of present abundance, if the local population is entirely open and the present level of fishing mortality persists. The population will exhibit self-sustaining dynamics (1 ≤ λ ≤ 1.07) as for a closed population if the ratio of self-recruits per gram of dry gonad is >0.775 (equivalent to 52.85% self-recruitment under present conditions). Elasticity analysis of demographic parameters indicated that future abundance can most effectively be influenced by increasing survival of mid-sized clams (∼80–120 mm) if the population is self-sustaining, and by increasing survival of juvenile clams (∼40–70 mm) if the population is non-self-sustaining (as for an open population). Our results illustrate that management priorities can vary depending on the amount of self-recruitment in a local population.

Accumulation and toxicity of metal oxide nanoparticles in a soft-sediment estuarine amphipod

Estuarine and marine sediments are a probable end point for many engineered nanoparticles (ENPs) due to enhanced aggregation and sedimentation in marine waters, as well as uptake and deposition by suspension-feeding organisms on the seafloor. Benthic infaunal organisms living in sediments encounter relatively high concentrations of pollutants and may also suffer toxic effects of ENPs. We tested whether three heavily used metal oxide ENPs, zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO) were toxic to an estuarine amphipod, Leptocheirus plumulosus. We used results from 10-day laboratory bioassays to estimate potential demographic impacts of ENP exposure. We also evaluated fate and transport pathways of the ENPs in the experiments to elucidate routes of uptake and exposure. Dissolved Zn was found in sediment pore water and overlying water samples at 10 fold the concentrations of Cu or Ni, a pattern indicative of the relatively high dissolution rate of ZnO ENPs compared with CuO and NiO ENPs. Accumulation of metals in amphipod tissues increased with exposure concentrations for all three ENPs, suggesting possible exposure pathways to higher taxa. Amphipods accumulated ≤600 μg Zn and Cu g(-1) and 1000 μg Ni g(-1). Amphipod mortality increased with ZnO and CuO concentrations, but showed no significant increase with NiO to concentrations as high as 2000 μg g(-1). The median lethal concentration in sediment (LC50) of ZnO was 763 μg g(-1) and 868 μg g(-1) for CuO ENPs. Our results indicate that ZnO and CuO ENPs, but not NiO ENPs, are toxic to L. plumulosus and that ZnO toxicity primarily results from Zn ion exposure while CuO toxicity is due to nanoparticle exposure.

Variable intertidal temperature explains why disease endangers black abalone

Epidemiological theory suggests that pathogens will not cause host extinctions because agents of disease should fade out when the host population is driven below a threshold density. Nevertheless, infectious diseases have threatened species with extinction on local scales by maintaining high incidence and the ability to spread efficiently even as host populations decline. Intertidal black abalone (Haliotis cracherodii), but not other abalone species, went extinct locally throughout much of southern California following the emergence of a Rickettsiales-like pathogen in the mid-1980s. The rickettsial disease, a condition known as withering syndrome (WS), and associated mortality occur at elevated water temperatures. We measured abalone body temperatures in the field and experimentally manipulated intertidal environmental conditions in the laboratory, testing the influence of mean temperature and daily temperature variability on key epizootiological processes of WS. Daily temperature variability increased the susceptibility of black abalone to infection, but disease expression occurred only at warm water temperatures and was independent of temperature variability. These results imply that high thermal variation of the marine intertidal zone allows the pathogen to readily infect black abalone, but infected individuals remain asymptomatic until water temperatures periodically exceed thresholds modulating WS. Mass mortalities can therefore occur before pathogen transmission is limited by density-dependent factors.

Toxicity of ZnO nanoparticles to the copepod Acartia tonsa, exposed through a phytoplankton diet

Zinc oxide (ZnO) nanoparticles are being increasingly utilized in a variety of products and applications and are therefore commonly discharged into aquatic environments, increasing exposure and potentially impacting aquatic organisms. Zinc oxide nanoparticles can depress growth of some marine phytoplankton, and several examples of nanoparticle trophic transfer have been documented, although not within planktonic communities. The authors test whether feeding on ZnO-exposed phytoplankton could cause toxic effects in a widespread and ecologically important marine grazer, the copepod Acartia tonsa. The authors exposed the diatom Thalassiosira weissflogii to ZnO nanoparticles for 7 d and measured growth, zinc accumulation, and zinc distribution within the algal cells to elucidate bioavailability to grazing copepods. Thalassiosira weissflogii cultured with nano-ZnO were continuously fed to A. tonsa for 7 d, and reproduction and survival were quantified. A dose-dependent growth reduction was observed in T. weissflogii exposed to nano-ZnO, with a 20% effective concentration (EC20) of 70 µg/L Zn and a lowest observed effect concentration (LOEC) of 99 µg/L Zn. Zinc accumulation in the algae occurred dose-dependently over time, with the majority of the zinc partitioning into the cell wall fraction. Feeding on ZnO-exposed diatoms led to a decrease in copepod survival and reproduction. The EC20s corresponding to the dissolved zinc concentration in the T. weissflogii exposure media were 112 µg/L (13 µg/g dry wt) and 143 µg/L (16 µg/g dry wt), and the LOECs were 168 µg/L (17 µg/g dry wt) and 263 µg/L (21 µg/g dry wt) for copepod survival and reproduction, respectively. These results provide evidence of trophic transfer of metal contaminants associated with metal oxide nanomaterials within a marine plankton community, leading to a reduction in individual demographic performance of an important coastal marine grazer.

Implementation of a multidisciplinary approach to solve complex nano EHS problems by the UC Center for the Environmental Implications of Nanotechnology

UC CEIN was established with funding from the US National Science Foundation and the US Environmental Protection Agency in 2008 with the mission to study the impact of nanotechnology on the environment, including the identification of hazard and exposure scenarios that take into consideration the unique physicochemical properties of engineered nanomaterials (ENMs). Since its inception, the Center has made great progress in assembling a multidisciplinary team to develop the scientific underpinnings, research, knowledge acquisition, education and outreach that is required for assessing the safe implementation of nanotechnology in the environment. In this essay, the development of the infrastructure, protocols, and decision-making tools that are required to effectively integrate complementary scientific disciplines allowing knowledge gathering in a complex study area that goes beyond the traditional safety and risk assessment protocols of the 20th century is outlined. UC CEIN's streamlined approach, premised on predictive hazard and exposure assessment methods, high-throughput discovery platforms and environmental decision-making tools that consider a wide range of nano/bio interfaces in terrestrial and aquatic ecosystems, demonstrates the implementation of a 21st-century approach to the safe implementation of nanotechnology in the environment.

Impact of engineered zinc oxide nanoparticles on the individual performance of Mytilus galloprovincialis

The increased use of engineered nanoparticles (ENPs) in consumer products raises the concern of environmental release and subsequent impacts in natural communities. We tested for physiological and demographic impacts of ZnO, a prevalent metal oxide ENP, on the mussel Mytilus galloprovincialis. We exposed mussels of two size classes, <4.5 and ≥ 4.5 cm shell length, to 0.1-2 mg l(-1) ZnO ENPs in seawater for 12 wk, and measured the effect on mussel respiration, accumulation of Zn, growth, and survival. After 12 wk of exposure to ZnO ENPs, respiration rates of mussels increased with ZnO concentration. Mussels had up to three fold more Zn in tissues than control groups after 12 wk of exposure, but patterns of Zn accumulation varied with mussel size and Zn concentrations. Small mussels accumulated Zn 10 times faster than large mussels at 0.5 mg l(-1), while large mussels accumulated Zn four times faster than small mussels at 2 mg l(-1). Mussels exposed to 2 mg l(-1) ZnO grew 40% less than mussels in our control group for both size classes. Survival significantly decreased only in groups exposed to the highest ZnO concentration (2 mg l(-1)) and was lower for small mussels than large. Our results indicate that ZnO ENPs are toxic to mussels but at levels unlikely to be reached in natural marine waters.

Ecological nanotoxicology: integrating nanomaterial hazard considerations across the subcellular, population, community, and ecosystems levels

Research into the health and environmental safety of nanotechnology has seriously lagged behind its emergence in industry. While humans have often adopted synthetic chemicals without considering ancillary consequences, the lessons learned from worldwide pollution should motivate making nanotechnology compatible with environmental concerns. Researchers and policymakers need to understand exposure and harm of engineered nanomaterials (ENMs), currently nanotechnology's main products, to influence the ENM industry toward sustainable growth. Yet, how should research proceed? Standard toxicity testing anchored in single-organism, dose-response characterizations does not adequately represent real-world exposure and receptor scenarios and their complexities. Our approach is different: it derives from ecology, the study of organisms' interactions with each other and their environments. Our approach involves the characterization of ENMs and the mechanistic assessment of their property-based effects. Using high throughput/content screening (HTS/HCS) with cells or environmentally-relevant organisms, we measure the effects of ENMs on a subcellular or population level. We then relate those effects to mechanisms within dynamic energy budget (DEB) models of growth and reproduction. We reconcile DEB model predictions with experimental data on organism and population responses. Finally, we use microcosm studies to measure the potential for community- or ecosystem-level effects by ENMs that are likely to be produced in large quantities and for which either HTS/HCS or DEB modeling suggest their potential to harm populations and ecosystems. Our approach accounts for ecological interactions across scales, from within organisms to whole ecosystems. Organismal ENM effects, if propagated through populations, can alter communities comprising multiple populations (e.g., plant, fish, bacteria) within food webs. Altered communities can change ecosystem services: processes that cycle carbon, nutrients, and energy, and regulate Earth's waters and atmosphere. We have shown ENM effects on populations, communities, and ecosystems, including transfer and concentration of ENMs through food chains, for a range of exposure scenarios; in many cases, we have identified subcellular ENM effects mechanisms. To keep pace with ENM development, rapid assessment of the mechanisms of ENM effects and modeling are needed. DEB models provide a method for mathematically representing effects such as the generation of reactive oxygen species and their associated damage. These models account for organism-level effects on metabolism and reproduction and can predict outcomes of ENM-organism combinations on populations; those predictions can then suggest ENM characteristics to be avoided. HTS/HCS provides a rapid assessment tool of the ENM chemical characteristics that affect biological systems; such results guide and expand DEB model expressions of hazard. Our approach addresses ecological processes in both natural and managed ecosystems (agriculture) and has the potential to deliver timely and meaningful understanding towards environmentally sustainable nanotechnology.

Small-scale spatial variation in population dynamics and fishermen response in a coastal marine fishery

A major challenge for small-scale fisheries management is high spatial variability in the demography and life history characteristics of target species. Implementation of local management actions that can reduce overfishing and maximize yields requires quantifying ecological heterogeneity at small spatial scales and is therefore limited by available resources and data. Collaborative fisheries research (CFR) is an effective means to collect essential fishery information at local scales, and to develop the social, technical, and logistical framework for fisheries management innovation. We used a CFR approach with fishing partners to collect and analyze geographically precise demographic information for grass rockfish (Sebastes rastrelliger), a sedentary, nearshore species harvested in the live fish fishery on the West Coast of the USA. Data were used to estimate geographically distinct growth rates, ages, mortality, and length frequency distributions in two environmental subregions of the Santa Barbara Channel, CA, USA. Results indicated the existence of two subpopulations; one located in the relatively cold, high productivity western Channel, and another in the relatively warm, low productivity eastern Channel. We parameterized yield per recruit models, the results of which suggested nearly twice as much yield per recruit in the high productivity subregion relative to the low productivity subregion. The spatial distribution of fishing in the two environmental subregions demonstrated a similar pattern to the yield per recruit outputs with greater landings, effort, and catch per unit effort in the high productivity subregion relative to the low productivity subregion. Understanding how spatial variability in stock dynamics translates to variability in fishery yield and distribution of effort is important to developing management plans that maximize fishing opportunities and conservation benefits at local scales.

Trophic cascades induced by lobster fishing are not ubiquitous in southern California kelp forests

Fishing can trigger trophic cascades that alter community structure and dynamics and thus modify ecosystem attributes. We combined ecological data of sea urchin and macroalgal abundance with fishery data of spiny lobster (Panulirus interruptus) landings to evaluate whether: (1) patterns in the abundance and biomass among lobster (predator), sea urchins (grazer), and macroalgae (primary producer) in giant kelp forest communities indicated the presence of top-down control on urchins and macroalgae, and (2) lobster fishing triggers a trophic cascade leading to increased sea urchin densities and decreased macroalgal biomass. Eight years of data from eight rocky subtidal reefs known to support giant kelp forests near Santa Barbara, CA, USA, were analyzed in three-tiered least-squares regression models to evaluate the relationships between: (1) lobster abundance and sea urchin density, and (2) sea urchin density and macroalgal biomass. The models included reef physical structure and water depth. Results revealed a trend towards decreasing urchin density with increasing lobster abundance but little evidence that urchins control the biomass of macroalgae. Urchin density was highly correlated with habitat structure, although not water depth. To evaluate whether fishing triggered a trophic cascade we pooled data across all treatments to examine the extent to which sea urchin density and macroalgal biomass were related to the intensity of lobster fishing (as indicated by the density of traps pulled). We found that, with one exception, sea urchins remained more abundant at heavily fished sites, supporting the idea that fishing for lobsters releases top-down control on urchin grazers. Macroalgal biomass, however, was positively correlated with lobster fishing intensity, which contradicts the trophic cascade model. Collectively, our results suggest that factors other than urchin grazing play a major role in controlling macroalgal biomass in southern California kelp forests, and that lobster fishing does not always catalyze a top-down trophic cascade.

Toxicity of nano-zero valent iron to freshwater and marine organisms

We tested whether three commercial forms (uncoated, organic coating, and iron oxide coating) of nano zero-valent iron (nZVI) are toxic to freshwater and marine organisms, specifically three species of marine phytoplankton, one species of freshwater phytoplankton, and a freshwater zooplankton species (Daphnia magna), because these organisms may be exposed downstream of where nZVI is applied to remediate polluted soil. The aggregation and reactivity of the three types of nZVI varied considerably, which was reflected in their toxicity. Since levels of Fe²⁺ and Fe³⁺ increase as the nZVI react, we also evaluated their toxicity independently. All four phytoplankton species displayed decreasing population growth rates, and Daphnia magna showed increasing mortality, in response to increasing levels of nZVI, and to a lesser degree with increasing Fe²⁺ and Fe³⁺. All forms of nZVI aggregated in soil and water, especially in the presence of a high concentration of calcium ions in groundwater, thus reducing their transports through the environment. However, uncoated nZVI aggregated extremely rapidly, thus vastly reducing the probability of environmental transport and potential for toxicity. This information can be used to design a risk management strategy to arrest the transport of injected nZVI beyond the intended remediation area, by injecting inert calcium salts as a barrier to transport.

Uptake, accumulation, and biotransformation of metal oxide nanoparticles by a marine suspension-feeder

A growing body of evidence indicates that some engineered nanoparticles (ENPs) are toxic to organisms that perform important ecosystem services in terrestrial and aquatic ecosystems. However, toxicity can be influenced by the biotransformation of contaminants, including ENPs, as it may alter the fate and transport of these substances. In turn, fate and transport can influence their bioavailability. To understand how biotransformation influences the fate and transport of ENPs in marine ecosystems, we exposed suspension-feeding mussels, Mytilus galloprovincialis, to two common nano-metal oxides, CeO(2) and ZnO, over a range of concentrations from 1mg L(-1) to 10mg L(-1), in a laboratory experiment. Mussels exposed to 10mg L(-1) accumulated 62μg g(-1) of Ce and 880μg g(-1) of Zn on a dry tissue basis but rejected 21,000μg g(-1) for Ce and 63,000μg g(-1) for Zn in pseudofeces. Scanning electron microscope evidence indicates CeO(2) remained as ENPs but ZnO did not after being rejected by the mussels. Mussels filtered most of the CeO(2) from the aqueous media, while a significant fraction of Zn remained in solution. Differences in ENP solubility affect ENP uptake, excretion, and accumulation in mussels. Our study highlights the potential role of marine suspension feeders in biotransformation of ENPs.

TiO2 nanoparticles are phototoxic to marine phytoplankton

Nanoparticulate titanium dioxide (TiO₂) is highly photoactive, and its function as a photocatalyst drives much of the application demand for TiO₂. Because TiO₂ generates reactive oxygen species (ROS) when exposed to ultraviolet radiation (UVR), nanoparticulate TiO₂ has been used in antibacterial coatings and wastewater disinfection, and has been investigated as an anti-cancer agent. Oxidative stress mediated by photoactive TiO₂ is the likely mechanism of its toxicity, and experiments demonstrating cytotoxicity of TiO₂ have used exposure to strong artificial sources of ultraviolet radiation (UVR). In vivo tests of TiO₂ toxicity with aquatic organisms have typically shown low toxicity, and results across studies have been variable. No work has demonstrated that photoactivity causes environmental toxicity of TiO₂ under natural levels of UVR. Here we show that relatively low levels of ultraviolet light, consistent with those found in nature, can induce toxicity of TiO₂ nanoparticles to marine phytoplankton, the most important primary producers on Earth. No effect of TiO₂ on phytoplankton was found in treatments where UV light was blocked. Under low intensity UVR, ROS in seawater increased with increasing nano-TiO₂ concentration. These increases may lead to increased overall oxidative stress in seawater contaminated by TiO₂, and cause decreased resiliency of marine ecosystems. Phototoxicity must be considered when evaluating environmental impacts of nanomaterials, many of which are photoactive.

Collaborative assessment of California spiny lobster population and fishery responses to a marine reserve network

Assessments of the conservation and fisheries effects of marine reserves typically focus on single reserves where sampling occurs over narrow spatiotemporal scales. A strategy for broadening the collection and interpretation of data is collaborative fisheries research (CFR). Here we report results of a CFR program formed in part to test whether reserves at the Santa Barbara Channel Islands, USA, influenced lobster size and trap yield, and whether abundance changes in reserves led to spillover that influenced trap yield and effort distribution near reserve borders. Industry training of scientists allowed us to sample reserves with fishery relevant metrics that we compared with pre-reserve fishing records, a concurrent port sampling program, fishery effort patterns, the local ecological knowledge (LEK) of fishermen, and fishery-independent visual surveys of lobster abundance. After six years of reserve protection, there was a four- to eightfold increase in trap yield, a 5-10% increase in the mean size (carapace length) of legal sized lobsters, and larger size structure of lobsters trapped inside vs. outside of three replicate reserves. Patterns in trap data were corroborated by visual scuba surveys that indicated a four- to sixfold increase in lobster density inside reserves. Population increases within reserves did not lead to increased trap yields or effort concentrations (fishing the line) immediately outside reserve borders. The absence of these catch and effort trends, which are indicative of spillover, may be due to moderate total mortality (Z = 0.59 for legal sized lobsters outside reserves), which was estimated from analysis of growth and length frequency data collected as part of our CFR program. Spillover at the Channel Islands reserves may be occurring but at levels that are insufficient to influence the fishery dynamics that we measured. Future increases in fishing effort (outside reserves) and lobster biomass (inside reserves) are likely and may lead to increased spillover, and CFR provides an ideal platform for continued assessment of fishery-reserve interactions.

Influence of corallivory, competition, and habitat structure on coral community shifts

The species composition of coral communities has shifted in many areas worldwide through the relative loss of important ecosystem engineers such as highly branched corals, which are integral in maintaining reef biodiversity. We assessed the degree to which the performance of recently recruited branching corals was influenced by corallivory, competition, sedimentation, and the interactions between these factors. We also explored whether the species-specific influence of these biotic and abiotic constraints helps to explain recent shifts in the coral community in lagoons of Moorea, French Polynesia. Population surveys revealed evidence of a community shift away from a historically acroporid-dominated community to a pocilloporid- and poritid-dominated community, but also showed that the distribution and abundance of coral taxa varied predictably with location in the lagoon. At the microhabitat scale, branching corals grew mainly on dead or partially dead massive Porites ("bommies"), promontories with enhanced current velocities and reduced sedimentation. A demographic study revealed that growth and survival of juvenile Pocillopora verrucosa and Acropora retusa, the two most common branching species of each taxon, were affected by predation and competition with vermetid gastropods. By 24 months of age, 20-60% of juvenile corals suffered partial predation by corallivorous fishes, and injured corals experienced reduced growth and survival. A field experiment confirmed that partial predation by corallivorous fishes is an important, but habitat-modulated, constraint for branching corals. Competition with vermetid gastropods reduced growth of both branching species but unexpectedly also provided an associational defense against corallivory. Overall, the impact of abiotic constraints was habitat-specific and similar for Acropora and Pocillopora, but biotic interactions, especially corallivory, had a greater negative effect on Acropora than Pocillopora, which may explain the local shift in coral community composition.

Influence of corallivory, competition, and habitat structure on coral community shifts

The species composition of coral communities has shifted in many areas worldwide through the relative loss of important ecosystem engineers such as highly branched corals, which are integral in maintaining reef biodiversity. We assessed the degree to which the performance of recently recruited branching corals was influenced by corallivory, competition, sedimentation, and the interactions between these factors. We also explored whether the species-specific influence of these biotic and abiotic constraints helps to explain recent shifts in the coral community in lagoons of Moorea, French Polynesia. Population surveys revealed evidence of a community shift away from a historically acroporid-dominated community to a pocilloporid- and poritid-dominated community, but also showed that the distribution and abundance of coral taxa varied predictably with location in the lagoon. At the microhabitat scale, branching corals grew mainly on dead or partially dead massive Porites ("bommies"), promontories with enhanced current velocities and reduced sedimentation. A demographic study revealed that growth and survival of juvenile Pocillopora verrucosa and Acropora retusa, the two most common branching species of each taxon, were affected by predation and competition with vermetid gastropods. By 24 months of age, 20-60% of juvenile corals suffered partial predation by corallivorous fishes, and injured corals experienced reduced growth and survival. A field experiment confirmed that partial predation by corallivorous fishes is an important, but habitat-modulated, constraint for branching corals. Competition with vermetid gastropods reduced growth of both branching species but unexpectedly also provided an associational defense against corallivory. Overall, the impact of abiotic constraints was habitat-specific and similar for Acropora and Pocillopora, but biotic interactions, especially corallivory, had a greater negative effect on Acropora than Pocillopora, which may explain the local shift in coral community composition.

Nanomaterials in the environment: from materials to high-throughput screening to organisms

One of the challenges in the field of nanotechnology is environmental health and safety (EHS), including consideration of the properties of engineered nanomaterials (ENMs) that could pose dangers to the environment. Progress in the field of nanomaterial development and nanotoxicology was presented at the International Conference on the Environmental Implications of Nanotechnology at the California NanoSystems Institute (CNSI) on the UCLA campus on May 11-14, 2010. This event was cohosted by the University of California Center for the Environmental Implications of Nanotechnology (UC CEIN) and the Center for the Environmental Implications of NanoTechnology (CEINT) based at Duke University. Participants included scientists and scholars from various backgrounds, including chemistry, biology, engineering, nanomaterial science, toxicology, ecology, mathematics, sociology, and policy makers. The topics of discussion included safety evaluation of ENMs from an environmental perspective, nanotoxicology, ecotoxicology, safe design of ENMs, environmental risk assessment, public perception of nanotechnology, application of ENMs in consumer products, and many more. The UC CEIN presented data on their predictive toxicological approach to the assessment of ENM libraries, which were designed and synthesized to develop an understanding of the material properties that could lead to hazard generation at the cellular and organismal levels in the environment. This article will focus on the first metal oxide ENM library that was introduced to harmonize research activities in the UC CEIN, with particular emphasis on the safety assessment of ZnO on cells and organisms. Methods of decreasing the observed toxic effects will also be discussed as an integral component of the UC CEIN's activity in developing safer nanomaterials to lessen their environmental impacts.

Impacts of metal oxide nanoparticles on marine phytoplankton

Information on the toxicity of environmentally relevant concentrations of nanoparticles in marine ecosystems is needed for informed regulation of these emerging materials. We tested the effects of two types of metal oxide nanoparticles, TiO(2) and ZnO, on population growth rates of four species of marine phytoplankton representing three major coastal groups (diatoms, chlorophytes, and prymnesiophytes). These metal oxide nanoparticles (NPs) are becoming common components in many industrial, household, and cosmetic products that are released into coastal ecosystems. Titania NPs showed no measurable effect on growth rates of any species, while ZnO NPs significantly depressed growth rate of all four species. ZnO NPs aggregated rapidly in seawater, forming particles >400 nm hydrodynamic diameter within 30 min, and dissolved quickly, reaching equilibrium concentrations within 12 h. Toxicity of ZnO NPs to phytoplankton was likely due to dissolution, release, and uptake of free zinc ions, but specific nanoparticulate effects may be difficult to disentangle from effects due to free zinc ions. A modeling approach based on a Dynamic Energy Budget (DEB) framework was used to estimate sublethal effects of the two NPs on phytoplankton populations. Concentrations that were estimated to have no effect on population growth (NEC) were (one standard error in parentheses) 428 (58) μg L(-1) ZnO for the diatom Skeletonema marinoi and 223 (56) μg L(-1) for Thalassiosira pseudonana. NEC could not be estimated for the other taxa but were within the range of 500-1000 μg L(-1). Our results suggest that effects of metal oxide NPs on marine organisms is likely to vary with particle type and organism taxonomy.

Stability and aggregation of metal oxide nanoparticles in natural aqueous matrices

There is a pressing need for information on the mobility of nanoparticles in the complex aqueous matrices found in realistic environmental conditions. We dispersed three different metal oxide nanoparticles (TiO(2), ZnO and CeO(2)) in samples taken from eight different aqueous media associated with seawater, lagoon, river, and groundwater, and measured their electrophoretic mobility, state of aggregation, and rate of sedimentation. The electrophoretic mobility of the particles in a given aqueous media was dominated by the presence of natural organic matter (NOM) and ionic strength, and independent of pH. NOM adsorbed onto these nanoparticles significantly reduces their aggregation, stabilizing them under many conditions. The transition from reaction to diffusion limited aggregation occurs at an electrophoretic mobility from around -2 to -0.8 microm s(-1) V(-1) cm. These results are key for designing and interpreting nanoparticle ecotoxicity studies in various environmental conditions.

Stability and aggregation of metal oxide nanoparticles in natural aqueous matrices

There is a pressing need for information on the mobility of nanoparticles in the complex aqueous matrices found in realistic environmental conditions. We dispersed three different metal oxide nanoparticles (TiO(2), ZnO and CeO(2)) in samples taken from eight different aqueous media associated with seawater, lagoon, river, and groundwater, and measured their electrophoretic mobility, state of aggregation, and rate of sedimentation. The electrophoretic mobility of the particles in a given aqueous media was dominated by the presence of natural organic matter (NOM) and ionic strength, and independent of pH. NOM adsorbed onto these nanoparticles significantly reduces their aggregation, stabilizing them under many conditions. The transition from reaction to diffusion limited aggregation occurs at an electrophoretic mobility from around -2 to -0.8 microm s(-1) V(-1) cm. These results are key for designing and interpreting nanoparticle ecotoxicity studies in various environmental conditions.

Effect of sub-lethal damage to juvenile colonies of massive Porites spp. under contrasting regimes of temperature and water flow

In this study, juvenile colonies of massive Porites spp. (a combination of P. lutea and P. lobata) from the lagoon of Moorea (W 149°50', S 17°30') were damaged and exposed to contrasting conditions of temperature and flow to evaluate how damage and abiotic conditions interact to affect growth, physiological performance, and recovery. The experiment was conducted in April and May 2008 and consisted of two treatments in which corals were either undamaged (controls) or damaged through gouging of tissue and skeleton in a discrete spot mimicking the effects of corallivorous fishes that utilize an excavating feeding mode. The two groups of corals were incubated for 10 days in microcosms that crossed levels of temperature (26.7 and 29.6°C) and flow (6 and 21 cm s^-1), and the response assessed as overall colony growth (change in weight), dark-adapted quantum yield of PSII (F_v/F_m), and healing of the gouged areas. The influence of damage on growth was affected by temperature, but not by flow. When averaged across flow treatments, damage promoted growth by 25% at 26.7°C, but caused a 25% inhibition at 29.6°C. The damage also affected F_v/F_m in a pattern that differed between flow speeds, with a 10% reduction at 6 cm s^-1, but a 4% increase at 21 cm s^-1. Regardless of damage, F_v/F_m at 21 cm s^-1 was 11% lower at 26.7°C than at 29.6°C, but was unaffected by temperature at 6 cm s^-1. The lesions declined in area at similar rates (4-5% day^-1) under all conditions, although the tissue within them regained a normal appearance most rapidly at 26.7°C and 6 cm s^-1. These findings show that the response of poritid corals to sub-lethal damage is dependent partly on abiotic conditions, and they are consistent with the hypothesis that following damage, calcification and photosynthesis can compete for metabolites necessary for repair, with the outcome affected by flow-mediated mass transfer. These results may shed light upon the ways in which poritid corals respond to biting by certain corallivorous fishes.

The University of California Center for the Environmental Implications of Nanotechnology

Assessing nanomaterialsfor human health and ecotoxicological impact can be well aided by using high-throughput laboratory methods.