Methylmercury exposure and health effects in humans: a worldwide concern

The paper builds on existing literature, highlighting current understanding and identifying unresolved issues about MeHg exposure, health effects, and risk assessment, and concludes with a consensus statement. Methylmercury is a potent toxin, bioaccumulated and concentrated through the aquatic food chain, placing at risk people, throughout the globe and across the socioeconomic spectrum, who consume predatory fish or for whom fish is a dietary mainstay. Methylmercury developmental neurotoxicity has constituted the basis for risk assessments and public health policies. Despite gaps in our knowledge on new bioindicators of exposure, factors that influence MeHg uptake and toxicity, toxicokinetics, neurologic and cardiovascular effects in adult populations, and the nutritional benefits and risks from the large number of marine and freshwater fish and fish-eating species, the panel concluded that to preserve human health, all efforts need to be made to reduce and eliminate sources of exposure.     

A typology of time‐scale mismatches and behavioral interventions to diagnose and solve conservation problems

Ecological systems often operate on time scales significantly longer or shorter than the time scales typical of human decision making, which causes substantial difficulty for conservation and management in socioecological systems. For example, invasive species may move faster than humans can diagnose problems and initiate solutions, and climate systems may exhibit long‐term inertia and short‐term fluctuations that obscure learning about the efficacy of management efforts in many ecological systems. We adopted a management‐decision framework that distinguishes decision makers within public institutions from individual actors within the social system, calls attention to the ways socioecological systems respond to decision makers’ actions, and notes institutional learning that accrues from observing these responses. We used this framework, along with insights from bedeviling conservation problems, to create a typology that identifies problematic time‐scale mismatches occurring between individual decision makers in public institutions and between individual actors in the social or ecological system. We also considered solutions that involve modifying human perception and behavior at the individual level as a means of resolving these problematic mismatches. The potential solutions are derived from the behavioral economics and psychology literature on temporal challenges in decision making, such as the human tendency to discount future outcomes at irrationally high rates. These solutions range from framing environmental decisions to enhance the salience of long‐term consequences, to using structured decision processes that make time scales of actions and consequences more explicit, to structural solutions aimed at altering the consequences of short‐sighted behavior to make it less appealing. Additional application of these tools and long‐term evaluation measures that assess not just behavioral changes but also associated changes in ecological systems are needed.     

Multiple spawning events and sexual reproduction in the octocoral Sarcophyton elegans (Cnidaria: Alcyonacea) on Lizard Island, Great Barrier Reef

Sarcophyton elegans is a common symbiotic (zooxanthellate) octocoral species in the shallow waters of the Great Barrier Reef (GBR). Study of a population at Lizard Island (14°40′S, 145°28′E) on the GBR from October 1991 to January 1994 revealed that, as is typical of tropical alcyonarian corals, S. elegans is a gonochoric broadcast spawner with a 1:1 sex ratio. Sexual reproduction was closely correlated with colony size, with first reproduction at 13-cm basal stalk circumference for females and 12 cm for males. Oogenesis took 19–24 months, with a new cycle commencing every year, and spermatogenesis took 10–12 months. The majority of gametes were released during the annual austral mass coral spawning event after the full moon in November, but gametes were also released after the full moon in each month between August and February. All autozooid polyps participated in reproduction, but those at the outer edge of a colony released their gametes first. During subsequent months, the polyps closer to the center of the colony released their gametes. This is a novel strategy of gamete release, reported here for the first time, which accommodates the demands of feeding and reproduction in a different way than other corals where individual polyps have separate feeding or reproductive roles. Colonies upstream in the prevailing current spawned up to 1 month earlier than those downstream and ceased 1 month earlier. The mechanism controlling this spatial differentiation in spawning time, repeatedly observed over three seasons, is unknown. Sarcophyton elegans appears to have a dual strategy of providing protection for its gametes by releasing most of them concurrently with the single, annual mass spawning of a large number of cnidarians, while also hedging its bets by individual colonies spawning a fraction of their gametes over an extended period of 6 months.     

Pyrethroid insecticides in bed sediments from urban and agricultural streams across the United States

Pyrethroid insecticides are hydrophobic compounds that partition to streambed sediments and have been shown to cause toxicity to non-target organisms; their occurrence is well documented in parts of California, but there have been limited studies in other urban and agricultural areas across the United States. To broaden geographic understanding of pyrethroid distributions, bed sediment samples were collected and analyzed from 36 streams in 25 states, with about 2/3 of the sites in urban areas and 1/3 in agricultural areas. At least one pyrethroid (of the 14 included in the analysis) was detected in 78% of samples. Seven pyrethroids were detected in one or more samples. Bifenthrin was the most frequently detected (58% of samples), followed by permethrin (31%), resmethrin (17%), and cyfluthrin (14%). The other three detected pyrethroids (cyhalothrin, cypermethrin and delta/tralomethrin) were found in two or fewer of the samples. Concentrations ranged from 0.3 to 180 ng g(-1) dry weight. The number of pyrethroids detected were higher in the urban samples than in the agricultural samples, but the highest concentrations of individual pyrethroids were split between urban and agricultural sites. The pyrethroids detected in the agricultural areas generally followed use patterns. Predicted toxicity was greater for urban areas and attributed to bifenthrin, cyfluthrin and cypermethrin, while in agricultural areas the toxicity was mainly attributed to bifenthrin.     

Hydrology of Clay Settling Areas and Surrounding Landscapes in the Phosphate Mining District,Peninsular Florida1

Abstract: The objective of this study was to use applied and naturally occurring geochemical tracers to study the hydrology of clay settling areas (CSAs) and the hydrological connectivity between CSAs and surrounding hydrological landscapes. The study site is located on the Fort Meade Mine in Polk County, Florida. The CSA has a well‐developed, subangular‐blocky, clay‐rich surface layer with abundant desiccation cracks and other macropores, and a massive, clay‐rich sublayer that is saturated below ～1.0‐2.5 m. A bromide tracer was applied to study hydrological processes in the upper part of the CSA. Bromide infiltrated rapidly and perched on a massive, clay‐rich sublayer. Bromide concentrations decreased in the upper part of the profile without being transported vertically down through the lower part of the profile suggesting that bromide was lost to lateral rather than to vertical transport. Infiltration and lateral flow were rapid suggesting that preferential flow through desiccation cracks and other macropores likely dominates flow in the upper part of the CSA. Naturally occurring solute and stable isotope tracers were used to study the hydrological connectivity between the CSA and the surrounding hydrological landscape. Three‐end mass‐balance mixing model results indicate that shallow and/or deep CSA water can be found in all downgradient waters and must be as much as ～50% of some downgradient waters. Discharge from the CSA to the surrounding surface water‐bodies and surficial aquifer occurs laterally through the berms and/or vertically through the massive, clay‐rich sublayer. However, the precise flow paths from the CSA to the surrounding hydrological landscape are unclear and the fluxes remain unquantified, so the precise effects of CSAs on the hydrology of the surrounding hydrological landscape also remain unquantified.     

Palaeoecology: A tool to improve the management of Australian estuaries

Addressing environmental problems in estuaries is a worldwide problem. Establishing benchmarks and targets for management is critical, whether the aim is conservation, restoration or sustainable use. Palaeoecological techniques have rapidly improved during the past decade, particularly with advances in methods that allow high resolution quantitative assessments of environmental change. Palaeoecology is a useful tool in environmental management as it allows pre-impact conditions, the rate, extent, direction and cause of change, and range of natural variability to be determined. Australian estuarine ecosystems are qualitatively different from the often more well-studied estuaries in North America and Europe, which means site-specific studies of Australian estuaries are needed to inform management. While a potentially useful and valuable tool, palaeoecological techniques have not yet been widely adopted and practically implemented as part of estuarine management strategies and policy frameworks in Australia.     

Seasonal timing of first rain storms affects rare plant population dynamics

A major challenge in forecasting the ecological consequences of climate change is understanding the relative importance of changes to mean conditions vs. changes to discrete climatic events, such as storms, frosts, or droughts. Here we show that the first major storm of the growing season strongly influences the population dynamics of three rare and endangered annual plant species in a coastal California (USA) ecosystem. In a field experiment we used moisture barriers and water addition to manipulate the timing and temperature associated with first major rains of the season. The three focal species showed two- to fivefold variation in per capita population growth rates between the different storm treatments, comparable to variation found in a prior experiment imposing eightfold differences in season-long precipitation. Variation in germination was a major demographic driver of how two of three species responded to the first rains. For one of these species, the timing of the storm was the most critical determinant of its germination, while the other showed enhanced germination with colder storm temperatures. The role of temperature was further supported by laboratory trials showing enhanced germination in cooler treatments. Our work suggests that, because of species-specific cues for demographic transitions such as germination, changes to discrete climate events may be as, if not more, important than changes to season-long variables.     

The effect of a natural environmental disturbance on maternal investment and pup behavior in the California sea lion

Summary Observed changes in maternal investment due to an environmentally induced decrease in food supply (the 1983 El Ni?o-Southern Oscillation) are compared witha priori predictions for the California sea lion (Zalophus californianus). Changes in behavior, growth and mortality of off-spring were also examined. Data collected in the first two months postpartum for the years before (PRE), during (EN), and the two years after (POST1 and POST2) the 1983 El Ni?o indicate that females initiated postpartum feeding trips earlier during the food shortage, and spent more time away on individual feeding trips in both the El Ni?o year and the year after. Perinatal sex ratios (♀:♂) in the years PRE, EN, POST1 and POST2 were 1:1, 1.4:1, 1.1:1 and 1:1.4, respectively. Fewer copulations were observed during the El Ni?o year, but this difference was not statistically significant. Pups spent less time suckling in the food shortage year and the year following, but attempted to sneak suckle more. Pups were less active and played on land less in the El Ni?o and following year. Finally, maternal investment as measured by milk intake of offspring was decreased, pups grew more slowly, and suffered increased mortality during the food shortage year. Despite expected sex differences in maternal investment and pup behavior in response to food shortage, there were no sex-biased differences in response in either females or pups. As expected, the food shortage did not affect adult males since they migrate north during the non-breeding season where the environmental perturbation was less severe.     

Evaluation of a combined macrophyte–epiphyte bioassay for assessing nutrient enrichment in the Portneuf River,Idaho, USA

We describe and evaluate a laboratory bioassay that uses Lemna minor L. and attached epiphytes to characterize the status of ambient and nutrient-enriched water from the Portneuf River, Idaho. Specifically, we measured morphological (number of fronds, longest surface axis, and root length) and population-level (number of plants and dry mass) responses of L. minor and community-level (ash-free dry mass [AFDM] and chlorophyll a [Chl a]) responses of epiphytes to nutrient enrichment. Overall, measures of macrophyte biomass and abundance increased with increasing concentrations of dissolved phosphorus (P) and responded more predictably to nutrient enrichment than morphological measures. Epiphyte AFDM and Chl a were also greatest in P-enriched water; enrichments of N alone produced no measurable epiphytic response. The epiphyte biomass response did not directly mirror macrophyte biomass responses, illustrating the value of a combined macrophyte–epiphyte assay to more fully evaluate nutrient management strategies. Finally, the most P-enriched waters not only supported greater standing stocks of macrophyte and epiphytes but also had significantly higher water column dissolved oxygen and dissolved organic carbon concentrations and a lower pH. Advantages of this macrophyte–epiphyte bioassay over more traditional single-species assays include the use of a more realistic level of biological organization, a relatively short assay schedule (~10 days), and the inclusion of multiple biological response and water-quality measures.