The role of marine aggregates in the ingestion of picoplankton-size particles by suspension-feeding molluscs

Suspension-feeding molluscs are important members of coastal communities and a large body of literature focuses on their feeding processes, including the efficiency of particle capture. Some molluscs, such as bivalves, capture individual picoplankton cells (0.2–2.0 μm) with a retention efficiency of less than 50%, leading to the assumption that such particles are not an important food resource. Picoplankton, however, are often concentrated in particle aggregates of much larger size. This study investigates the ability of suspension feeders to ingest picoplankton-size particles (0.2–2.0 μm) bound in marine aggregates. We fed clams (Mercenaria mercenaria), mussels (Mytilus edulis), oysters (Crassostrea virginica), scallops (Argopecten irradians) and slipper snails (Crepidula fornicata) 1.0- and 0.5-μm fluorescent particles (either polystyrene beads or bacteria) that were (1) dispersed in seawater, or (2) embedded within laboratory-made aggregates. Dispersed 10-μm beads were also delivered so that feeding activity could be determined. Ingested fluorescent particles were recovered in feces or isolated digestive glands and quantified. Results indicate that aggregates significantly enhance the ingestion of 1.0- and 0.5-μm beads by all species of bivalves, and enhance the ingestion of bacteria (greatest cell dimension ca. 0.6 μm) by all suspension feeders examined. Differences among species in their ability to ingest aggregates and picoplankton-size particles, however, were evident. Compared to mussels and clams, scallops and oysters ingested fewer aggregates with 1.0-μm beads or bacteria, and slipper snails ingested the most dispersed beads and bacteria. These differences may be a consequence of variations in gill structure and mechanisms of particle processing. Our data demonstrate that suspension feeders can ingest picoplankton-size particles that are embedded within aggregates, and suggest that such constituent particles may be an important food resource.     

Offspring size variation within broods as a bet-hedging strategy in unpredictable environments

Offspring size is strikingly variable within species. Although theory can account for variation in offspring size among mothers, an adaptive explanation for variation within individual broods has proved elusive. Theoretical considerations of this problem assume that producing offspring that are too small results in reduced offspring viability, but producing offspring that are too large (for that environment) results only in a lost opportunity for increased fecundity. However, logic and recent evidence suggest that offspring above a certain size will also have lower fitness, such that mothers face fitness penalties on either side of an optimum. Although theory assuming intermediate optima has been developed for other diversification traits, the implications of this idea for selection on intra-brood variance in offspring size have not been explored theoretically. Here we model the fitness of mothers producing offspring of uniform vs. variable size in unpredictably variable environments and compare these two strategies under a variety of conditions. Our model predicts that producing variably sized offspring results in higher mean maternal fitness and less variation in fitness among generations when there is a maximum and minimum viable offspring size, and when many mothers under- or overestimate this optimum. This effect is especially strong when the viable offspring size range is narrow relative to the range of environmental variation. To determine whether this prediction is consistent with empirical evidence, we compared within- and among-mother variation in offspring size for five phyla of marine invertebrates with different developmental modes corresponding to contrasting levels of environmental predictability. Our comparative analysis reveals that, in the developmental mode in which mothers are unlikely to anticipate the relationship between offspring size and performance, size variation within mothers exceeds variation among mothers, but the converse is true when optimal offspring size is likely to be more predictable. Together, our results support the hypothesis that variation in offspring size within broods can reflect an adaptive strategy for dealing with unpredictably variable environments. We suggest that, when there is a minimum and a maximum viable offspring size and the environment is unpredictable, selection will act on both the mean and variance of offspring size.     

A New Open‐Access HUC‐8 Based Downscaled CMIP‐5 Climate Model Forecast Dataset for the Conterminous United States

Watershed‐scale hydrologic simulation models generally require climate data inputs including precipitation and temperature. These climate inputs can be derived from downscaled global climate simulations which have the potential to drive runoff forecasts at the scale of local watersheds. While a simulation designed to drive a local watershed model would ideally be constructed at an appropriate scale, global climate simulations are, by definition, arbitrarily determined large rectangular spatial grids. This paper addresses the technical challenge of making climate simulation model results readily available in the form of downscaled datasets that can be used for watershed scale models. Specifically, we present the development and deployment of a new Coupled Model Intercomparison Project phase 5 (CMIP5) based database which has been prepared through a scaling and weighted averaging process for use at the level of U.S. Geological Survey (USGS) Hydrologic Unit Code (HUC)‐8 watersheds. The resulting dataset includes 2,106 virtual observation sites (watershed centroids) each with 698 associated time series datasets representing average monthly temperature and precipitation between 1950 and 2099 based on 234 unique climate model simulations. The new dataset is deployed on a HydroServer and distributed using WaterOneFlow web services in the WaterML format. These methods can be adapted for downscaled General Circulation Model (GCM) results for specific drainage areas smaller than HUC‐8. Two example use cases for the dataset also are presented.     

Offspring size effects mediate competitive interactions in a colonial marine invertebrate

Over the past 30 years, numerous attempts to understand the relationship between offspring size and fitness have been made, and it has become clear that this critical relationship is strongly affected by environmental heterogeneity. For marine invertebrates, there has been a long-standing interest in the evolution of offspring size, but there have been very few empirical and theoretical examinations of post-metamorphic offspring size effects, and almost none have considered the effect of environmental heterogeneity on the offspring size/fitness relationship. We investigated the post-metamorphic effects of offspring size in the field for the colonial marine invertebrate Botrylloides violaceus. We also examined how the relationship between offspring size and performance was affected by three different types of intraspecific competition. We found strong and persistent effects of offspring size on survival and growth, but these effects depended on the level and type of intraspecific competition. Generally, competition strengthened the advantages of increasing maternal investment. Interestingly, we found that offspring size determined the outcome of competitive interaction: juveniles that had more maternal investment were more likely to encroach on another juvenile's territory. This suggests that mothers have the previously unrecognized potential to influence the outcome of competitive interactions in benthic marine invertebrates. We created a simple optimality model, which utilized the data generated from our field experiments, and found that increasing intraspecific competition resulted in an increase in predicted optimal size. Our results suggest that the relationship between offspring size and fitness is highly variable in the marine environment and strongly dependent on the density of conspecifics.     

Methyl bromide as a building disinfectant: interaction with indoor materials and resulting byproduct formation

Several buildings were contaminated with Bacillus anthracis in the fall of 2001. These events required consideration of how to disinfect large indoor spaces for continued worker occupation. The interactions of gaseous disinfectants with indoor materials may inhibit the disinfection process, cause persistence of the disinfectant, and lead to possible byproduct formation and persistence. Methyl bromide (CH3Br) is a candidate for disinfection/deactivation of biological agents in buildings. In this study, 24 indoor materials were exposed to CH3Br for 16 hr at concentrations ranging from 100 to 2500 ppm in 48-L electropolished stainless steel chambers. CH3Br concentrations were measured during and after disinfection. Its interactions with materials were observed to be small, with nearly complete and rapid desorption. Between 3% and 8% of CH3Br adsorbed to four materials (office partition, ceiling tile, particle-board, and gypsum wallboard with satin paint), and the degree of adsorption decreased with increasing relative humidity. The percentage of adsorption to all other materials was <2%. This result suggests that when designing disinfection events with CH3Br, loss to indoor materials can be neglected in terms of disinfectant dose calculations. Possible reaction products were identified and/or quantified before and after exposure to CH3Br. Several monomethylated and dimethylated aliphatic compounds were observed in chamber air at low concentrations after the exposures of six materials to CH3Br. Concentration increases also occurred for chemicals that were observed to naturally off-gas from materials before exposure to CH3Br, suggesting that CH3Br may play a role in enhancing the natural off-gassing of chemicals, for example, by competitive displacement of compounds that already existed in the materials. The results described in this paper should facilitate the design of building disinfection systems involving CH3Br.     

Phosphorus removal with by-products in a flow-through setting

Phosphorus (P) losses to surface waters can result in eutrophication. Some industrial by-products have a strong affinity for dissolved P and may be useful in reducing nonpoint P pollution with landscape-scale runoff filters. Although appreciable research has been conducted on characterizing P sorption by industrial by-products via batch isotherms, less data are available on P sorption by these materials in a flow-through context integral to a landscape P filter. The objectives of this study were to evaluate several industrial by-products for P sorption in a flow-through setting, to determine material chemical properties that have the greatest impact on P sorption in a flow-through setting, and to explore how retention time (RT) and P concentration affect P removal. Twelve materials were characterized for chemical properties that typically influence P removal and subjected to flow-through P sorption experiments in which five different RTs and P concentrations were tested. The impact of RT and P concentrations on P removal varied based on material chemical properties, mainly as a function of oxalate-extractable aluminum (Al), iron (Fe), and water-soluble (WS) calcium (Ca). Statistical analysis showed that materials elevated in oxalate-extractable Al and Fe and WS Ca and that were highly buffered above pH 6 were able to remove the most P under flow-through conditions. Langmuir sorption maximum values from batch isotherms were poorly correlated with and overestimated P removal found under flow-through conditions. Within the conditions tested in this study, increases in RT and inflow P concentrations increased P removal among materials most likely to remove P via precipitation, whereas RT had little effect on materials likely to remove P via ligand exchange.     

TROPHIC STATE EVALUATION FOR SELECTED LAKES IN GRAND TETON NATIONAL PARK1

ABSTRACT: Increased visitation at Grand Teton National Park (GTNP) has raised concerns about impacts on surface water in the park. The purposes of this study are to perform a benchmark trophic state survey for comparison to future evaluations and to identify possible areas of concern. Four watershed regions based on geographic and geologic features were delineated for study. Six Alpine lakes, six Moraine lakes, three Valley lakes, and two Colter Bay lakes are evaluated. Lakes were sampled for total phosphorus (TP), chlorophyll‐a, and transparency. The water quality, as defined by trophic state, in the park is generally good. Oligotrophic to mesotrophic conditions were found in the Alpine and Moraine lakes and mesotrophic to eutrophic conditions were found in the Colter Bay and Valley lakes. High inflow TP concentrations in the park's northeast side may be due to the presence of natural geologic phosphate from the Phosphoria Formation.     

Exposing males to female scent increases the cost of controlling <Emphasis Type=Italic>Salmonella</Emphasis> infection in wild house mice

Secondary sexual characters often provide indicators of a male’s resistance to infectious diseases to rivals and potential mates, but it is unclear why. It is often suggested that males honestly signal their health due to energetic and other physiological trade-offs between investing into secondary sexual traits vs resistance to infectious diseases. Our aim was to determine whether such a trade-off exists using wild-derived male house mice (Mus domesticus). We exposed male mice to female scent, a manipulation that induces elevations in testosterone concentration and the expression of a variety of testosterone-mediated secondary sexual traits, and tested whether this sexual stimulation impaired the males’ ability to resolve or cope with an experimental infection (Salmonella enterica). We kept the males on a controlled diet to prevent them from compensating by eating more food. We found that sexually stimulated males were able to control bacterial growth as effectively as sham-stimulated controls; however, to do so, they lost more body mass during infection compared to the controls. In contrast, we found no evidence that sexual stimulation reduced the body mass of uninfected male mice. These results indicate that males’ responses to female odor are not immunosuppressive per se, yet they increase the energetic costs of controlling infection. Our findings support the idea that there is a physiological trade-off between secondary sexual signaling vs resistance to infectious diseases and suggest that studies using only immunocompetence assays might fail to detect such energetic trade-offs. We dedicate this paper to the late Professor Chris Barnard who conducted pioneering research on this topic.     

Sisters in sustainability: municipal partnerships for social,environmental, and economic growth

While debates about sustainable development tend to focus on national- and international-scale problems, sustainability programs and research generally focus on the regional, county, municipal, or even household level. Less research has focused on evaluating the benefits of pairing two cities (i.e., sister city partnerships) with different needs and capabilities to jointly enhance the potential for sustainable practices between the cities. Given shrinking state and federal budgets and the nascent national climate policy, how might US cities use existing resources to achieve greater levels of sustainability? This paper presents a new data-driven mathematical tool—the partnership assessment for intra-regional sustainability—that city planners can use to explore the prospects for improving sustainability practices by leveraging existing resources and establishing synergistic partnerships with neighboring cities. The efficacy of the tool is assessed through the presentation of a Southern California case study and the results of a psychological survey of Southern California residents. Results indicate that cities of different size and scale would benefit from synergistic sustainability programs that pool the resources and needs of both cities. The paper concludes with a discussion of potential societal implications, methodological issues, and barriers to implementation.