Potential effects of climate change and rising CO2 on ecosystem processes in northeastern U.S. forests

Forest ecosystems represent the dominant form of land cover in the northeastern United States and are heavily relied upon by the region’s residents as a source of fuel, fiber, structural materials, clean water, economic vitality, and recreational opportunities. Although predicted changes in climate have important implications for a number of ecosystem processes, our present understanding of their long-term effects is poor. In this study, we used the PnET-CN model of forest carbon (C), nitrogen (N) and water cycling to evaluate the effects of predicted changes in climate and atmospheric carbon dioxide (CO₂) on forest growth, C exchange, water runoff, and nitrate ( $ {\text{NO}}^{ - }_{3} $ ) leaching at five forest research sites across the northeastern U.S. We used four sets of statistically downscaled climate predictions from two general circulation models (the Hadley Centre Coupled Model, version 3 and the Parallel Climate Model) and two scenarios of future CO₂ concentrations. A series of model experiments was conducted to examine the effects of future temperature, precipitation, CO₂, and various assumptions regarding the physiological response of forests to these changes. Results indicate a wide range of predicted future growth rates. Increased growth was predicted across deciduous sites under most future conditions, while growth declines were predicted for spruce forests under the warmest scenarios and in some deciduous forests when CO₂ fertilization effects were absent. Both climate and rising CO₂ contributed to predicted changes, but their relative importance shifted from CO₂-dominated to climate-dominated from the first to second half of the twenty-first century. Predicted runoff ranged from no change to a slight decrease, depending on future precipitation and assumptions about stomatal response to CO₂. Nitrate leaching exhibited variable responses, but was highest under conditions that imposed plant stress with no physiological effects of CO₂. Although there are considerable uncertainties surrounding predicted responses to climate change, these results provide a range of possible outcomes and highlight interactions among processes that are likely to be important. Such information can be useful to scientists and land managers as they plan on means of examining and responding to the effects of climate change.     

Rapid prenatal diagnosis of 14 cases of triploidy using fish with multiple probes

Fluorescence in situ hybridization (FISH) of chromosome-specific probes to interphase nuclei can rapidly identify aneuploidies in uncultured amniotic fluid cells. Using DNA probe sets specific for chromosomes 13, 18, 21, X, and Y, we have identified 14 fetuses where the hybridization pattern was consistent with a triploid chromosome constitution. In each case, the identification of fetal abnormalities by ultrasound examination initiated a request for rapid determination of ploidy status via prenatal FISH analysis of uncultured amniocytes. FISH produced a three-signal pattern for the three autosomes in combination with signals indicating an XXX or XXY sex chromosome complement. This hybridization pattern was interpreted to be consistent with triploidy. Results were reported to the physician within 2 days of amniocentesis and subsequently confirmed by cytogenetics. These cases demonstrate the utility of FISH for rapid prenatal identification of triploidy, particularly when fetal abnormalities are seen with ultrasonographic examination.     

Endocrine disrupting chemicals accumulate in earthworms exposed to sewage effluent

Endocrine disrupting chemicals (EDCs) can alter endocrine function in exposed animals. Such critical effects, combined with the ubiquity of EDCs in sewage effluent and potentially in tapwater, have led to concerns that they could be major physiological disruptors for wildlife and more controversially for humans. Although sewage effluent is known to be a rich source of EDCs, there is as yet no evidence for EDC uptake by invertebrates that live within the sewage treatment system. Here, we describe the use of an extraction method and GC-MS for the first time to determine levels of EDCs (e.g., dibutylphthalate, dioctylphthalate, bisphenol-A and 17beta-estradiol) in tissue samples from earthworms (Eisenia fetida) living in sewage percolating filter beds and garden soil. To the best of our knowledge, this is the first such use of these techniques to determine EDCs in tissue samples in any organism. We found significantly higher concentrations of these chemicals in the animals from sewage percolating filter beds. Our data suggest that earthworms can be used as bioindicators for EDCs in these substrates and that the animals accumulate these compounds to levels well above those reported for waste water. The potential transfer into the terrestrial food chain and effects on wildlife are discussed.     

Detecting improvement in ambient air toxics: An application to ambient benzene measurements in Houston,Texas

Traditional regulatory methods for evaluating air toxics have several limitations. Two common methods rely either on self-reported industrial emissions from the Toxics Release Inventory or a single summary statistic such as the average or arithmetic mean. A novel statistical approach for detecting overall long term improvement in ambient air quality is demonstrated using measurements of the air toxic benzene evaluated over five years in Houston, Texas. Through trends of seven key statistical measures, long term improvements were detected at more monitors than would have been found using traditional methods while lack of improvement is highlighted at other monitors. This new approach includes analysis of high and low end concentrations, as well as central tendency, evaluated at specific air toxic human health risk thresholds.     

Environmental information sharing: a means to support the legitimization of oyster farmers’ stewardship over water quality management in NSW,Australia

Oyster farmers depend on good water quality. Activities upstream from estuaries result in externalities that impact water quality. Over the last 10 years, oyster farmers have been developing estuary‐wide environmental management systems ( EMSs ) to tackle internal (i.e. industry‐related) and external (i.e. catchment) issues in N ew S outh W ales, A ustralia. Drawing on interview‐based research and document analyses, this paper shows that the process of creating an EMS for the oyster industry, as well as the creation of the EMS itself, resulted in legitimizing the industry's stewardship over the natural resource it depends on (water). For the oyster industry, this result was due to a change in the scale on which EMSs have been developed: instead of viewing issues at the individual business level, the systems expanded their viewpoint to the entire catchment, and included every oyster business in the estuary, as well as all other activities in the upper catchment. By providing a means of communicating internal efforts and with the support of local government bodies, EMSs provided a mechanism with which influence over upstream actors and activities could be exerted. We demonstrate this by using the ‘social‐ecological systems’ and ‘ ENCORE ’ frameworks, emphasizing the transitions that allowed for this change of scale to take place.     

Habitat selection increases the isolating effect of habitat fragmentation on the gopher tortoise

Habitat selection requires choice, which differentiates it from habitat use, and choice, in turn, is dependent upon the responses of organisms to the environmental, social, and other cues that they perceive. Habitat selection by the gopher tortoise (Gopherus polyphemus) was investigated by translocating tortoises and monitoring their movements within two sites in central Florida. The first site supported a stable preponderance of high-quality habitat, and tortoises avoided areas with a dense tree canopy cover caused by fire exclusion. The second site was badly invaded by an introduced weed, and tortoises avoided areas where the weed had formed a dense monoculture. At both sites, individuals appeared to be responding to visual cues to avoid areas that were relatively dark. In landscapes with relatively large amounts of high-quality habitat, this avoidance behavior serves the gopher tortoise well by keeping individuals within the dominant habitat type. In degraded areas, high-quality habitat often becomes increasingly uncommon, and the avoidance behavior exhibited by the tortoises will result in individuals becoming confined to small patches, causing a significant reduction in fitness and hence questioning their long-term survival in such areas. The results from our study show that in order to maintain viable tortoise populations in areas increasingly subjected to human fragmentation and degradation, it is crucial not only to suppress tree canopy cover continually and prevent invasion by exotic weeds, but also to be mindful that the avoidance behavior of the gopher tortoise could prevent individuals from fully occupying a high-quality habitat in response to restoration and management efforts.     

Removal processes for arsenic in constructed wetlands

Arsenic pollution in aquatic environments is a worldwide concern due to its toxicity and chronic effects on human health. This concern has generated increasing interest in the use of different treatment technologies to remove arsenic from contaminated water. Constructed wetlands are a cost-effective natural system successfully used for removing various pollutants, and they have shown capability for removing arsenic. This paper reviews current understanding of the removal processes for arsenic, discusses implications for treatment wetlands, and identifies critical knowledge gaps and areas worthy of future research. The reactivity of arsenic means that different arsenic species may be found in wetlands, influenced by vegetation, supporting medium and microorganisms. Despite the fact that sorption, precipitation and coprecipitation are the principal processes responsible for the removal of arsenic, bacteria can mediate these processes and can play a significant role under favourable environmental conditions. The most important factors affecting the speciation of arsenic are pH, alkalinity, temperature, dissolved oxygen, the presence of other chemical species - iron, sulphur, phosphate -, a source of carbon, and the wetland substrate. Studies of the microbial communities and the speciation of arsenic in the solid phase using advanced techniques could provide further insights on the removal of arsenic. Limited data and understanding of the interaction of the different processes involved in the removal of arsenic explain the rudimentary guidelines available for the design of wetlands systems.     

Modifying native and exotic species richness correlations: the influence of fire and seed addition.

An important goal in restoration is to increase the richness of native species while reducing exotic species. However, native species richness is often positively correlated with exotic species richness. In a grassland-savanna system in Michigan (USA), we show that management that focuses on changing the nature of the exotic-native richness relationship can be used to restore native communities. Native and exotic species richnesses were positively correlated, likely due to a shared coupling with aboveground live biomass (a surrogate for productivity). The addition of native seed shifted the exotic-native richness relationship from a linear positive to a monotonic relationship: in areas of intermediate levels of exotic species richness, seed addition increased native diversity without an associated effect on exotic diversity, but in areas of high or low exotic richness, it did not affect native species richness. Prescribed burning broke the correlation between native and exotic richness with no consistent effect on the richness of either group. However, when burning was combined with native-seed addition, the relationship between native and exotic richness was maintained and was shifted upwards, enhancing native recruitment. Although aboveground productivity was strongly related to species richness across the landscape, changes in productivity did not drive these shifts.     

Testing isosource: stable isotope analysis of a tropical fishery with diverse organic matter sources

We sampled consumers and organic matter sources (mangrove litter, freshwater swamp-forest litter, seagrasses, seagrass epiphytes, and marine particulate organic matter [MPOM]) from four estuaries on Kosrae, Federated States of Micronesia for stable isotope (sigma13C and sigma34S) analysis. Unique mixing solutions cannot be calculated in a dual-isotope, five-endmember scenario, so we tested IsoSource, a recently developed statistical procedure that calculates ranges in source contributions (i.e., minimum and maximum possible). Relatively high minimum contributions indicate significant sources, while low maxima indicate otherwise. Litter from the two forest types was isotopically distinguishable but had low average minimum contributions (0-8% for mangrove litter and 0% for swamp-forest litter among estuaries). Minimum contribution of MPOM was also low, averaging 0-13% among estuaries. Instead, local marine sources dominated contributions to consumers. Minimum contributions of seagrasses averaged 8-47% among estuaries (range 0-88% among species). Minimum contributions of seagrass epiphytes averaged 5-27% among estuaries (range 0-69% among species). IsoSource enabled inclusion of five organic matter sources in our dual-isotope analysis, ranking trophic importance as follows: seagrasses > seagrass epiphytes > MPOM > mangrove forest > freshwater swamp-forest. IsoSource is thus a useful step toward understanding which of multiple organic matter sources support food webs; more detailed work is necessary to identify unique solutions.     

Organochlorines and selenium in California night-heron and egret eggs

Exceptionally high concentrations of DDE were found in black-crowned night-heron (Nycticorax nycticorax) (geometric mean 8.62 g g^–1 wet wt.) and great egret (Casmerodius albus) (24.0 g g^–1) eggs collected from the Imperial Valley (Salton Sea), California in 1985. DDE concentrations in 14 of the 87 (16%) randomly selected night-heron eggs from six colonies (two in San Francisco Bay, three in the San Joaquin Valley, and one at Salton Sea) were higher than those associated with reduced reproductive success of night-herons (8 g g^–1). In addition, mean shell thickness of night-heron eggs collected from the San Joaquin Valley and from San Francisco Bay during 1982–1984 was significantly less than pre-DDT thickness and was negatively correlated (r=–0.50, n=75, P<0.0001) with DDE concentration. Mean selenium concentration in night-heron eggs from Salton Sea (1.10 g g^–1) was significantly higher than in eggs from three locations in the San Joaquin Valley, and in egret eggs from Salton Sea.