Congruence Among Encounters,Norms, Crowding,and Management in a Marine Protected Area

Over the past few decades, recreation and tourism use has increased at many marine protected areas, generating concerns about impacts of this increasing use on experiences and conditions at these areas (e.g., crowding, conflict). This article uses data from Molokini Shoal Marine Life Conservation District in Hawai’i to examine: (a) reported encounters, crowding, normative tolerances for various use levels, and support of use related management strategies at this site; and (b) whether users who encounter higher use levels than their norms feel more crowded and are more supportive of restrictive management strategies. Data were obtained from onsite pre-trip and post-trip questionnaires of 712 passengers on commercial snorkel and dive tours visiting this site. Norms were measured with acceptance of 12 photographs depicting levels of boat use. On average, users would accept seeing no more than approximately 16 boats at one time at Molokini and this number was observed on over 20% of trips to the site. Although the majority of users expected to escape crowds at Molokini, 67% felt crowded and up to 79% supported actions that would directly restrict use at this site (e.g., limit number of boats). Users who encountered more boats than their normative tolerance felt more crowded and were more supportive of these management strategies. Findings suggest that this marine protected area is operating over its capacity and management is needed to improve experiences and conditions.     

Experience with chemotactile cues indicating female feeding history impacts male courtship investment in the wolf spider <Emphasis Type="BoldItalic">Schizocosa ocreata</Emphasis>

Male fitness is often determined by the ability of the male to gain access to multiple mates, although in species that exhibit sexual cannibalism, males might increase their likelihood of being cannibalized with each encounter. This risk should create selection for males who are able to perceive potential risks associated with mating encounters. We studied male Schizocosa ocreata wolf spiders to determine whether they use female chemotactile cues (silk, excreta) as indicators of potential risks and how these cues affected subsequent male courtship behaviors. Female treatments included satiated females vs. starved females, as well as a treatment where females had recently cannibalized a male S. ocreata. We performed experiments to assess (1) if males use female chemotactile cues to determine potential risks associated with differing female feeding treatments and alter courtship investment, and 2) how male experience with female chemotactile cues affected courtship investment in subsequent female encounters. At first encounter, males do not vary courtship investment (number of bouts, duration, and vigor) with different female feeding treatments. However, male behaviors during subsequent encounters with female chemotactile cues varied in complex ways, depending on female feeding treatment and male first encounter experience. These data suggest that male experience impacts perception of female chemical cues and offers the male opportunity to avoid sexual cannibalism in high-risk situations.     

Two-dimensional wavelet analysis of spruce budworm host basal area in the Border Lakes landscape

Increases in the extent and severity of spruce budworm (Choristoneura fumiferana Clem.) outbreaks over the last century are thought to be the result of changes in forest structure due to forest management. A corollary of this hypothesis is that manipulations of forest structure and composition can be used to reduce future forest vulnerability. However, to what extent historical forest management has influenced current spatial patterns of spruce budworm host species is unknown. To identify landscape-scale spatial legacies of forest management in patterns of spruce budworm host species (i.e., Abies balsamea and Picea spp.), we analyzed remotely sensed forest data from the Border Lakes landscape of northern Minnesota and northwestern Ontario. Our study area contains three regions with different management histories: (1) fine-scale logging patterns in Minnesota, (2) coarse-scale logging patterns in Ontario, and (3) very limited logging history in the Boundary Waters Canoe Area and adjacent Quetico Provincial Park. We analyzed forest basal-area data using wavelets and null models to identify: (1) at which scales forest basal area is structured, (2) where those scales of pattern are significantly present, and (3) whether regions of local significance correspond to regional boundaries that separate the study area. Results indicate that spatial patterns in host basal area are created by nonstationary processes and that these processes are further constrained by lakes and wetlands. Wavelet analysis combined with significance testing revealed a bimodal distribution of scale-specific wavelet variance and separate zones of host species basal area that partially correspond with regional boundaries, particularly between Minnesota and the Wilderness region. This research represents one of the first comparisons of forest spatial structure in this region across an international border and presents a novel method of two-dimensional wavelet analysis that can be used to identify significant scale-specific structure in spatial data.     

Solid-phase extraction using hierarchical organosilicates for enhanced detection of nitroenergetic targets

A novel porous organosilicate material was evaluated for application as a solid phase extraction sorbent for preconcentration of nitroenergetic targets from aqueous solution prior to HPLC analysis. The performance of the sorbent in spiked deionized water, groundwater, and surface water was evaluated. Targets considered included 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, RDX, HMX, and nitroglycerin. The sorbent was shown to provide improved performance over Sep-Pak RDX. The impact of complex matrices on target preconcentration by the sorbent was also found to be less dramatic than that observed for LiChrolut EN. The impact of changes in pH on target preconcentration was considered. Aqueous soil extracts generated from samples collected at sites of ordnance testing were also used to evaluate the materials. The results presented here demonstrate the potential of this novel sorbent for application as a solid phase extraction material for the preconcentration of nitroenergetic targets from aqueous solutions.     

Use of a low‐cost substrate in a continuous recirculation process to stimulate plumewide anaerobic dechlorination of chlorinated solvents

Over the past 20 years, significant time and money have been spent on better understanding and successfully applying bioremediation in the field. The results of these efforts provide a deeper un‐derstanding of aerobic and anaerobic microbial processes, the microbial species and environ‐mental conditions that are desirable for specific degradation pathways, and the limitations that may prevent full‐scale bioremediation from being successfully applied in heterogeneous subsur‐face environments. Numerous substrates have been identified as effective electron donors to stimulate anaerobic dechlorination of chlorinated ethenes, but methods of delivering these sub‐strates for in situ bioremediation (direct‐push injections, slug injections, high‐pressure injections, fracture wells, etc.) have yet to overcome the main limitation of achieving contact between these substrates and the contaminants. Therefore, although it is important (from a full‐scale remedia‐tion standpoint) to select an appropriate, low‐cost substrate that can be supplied in sufficient quantity to promote remediation of a large source area and its associated plume, it is equally im‐portant to ensure that the substrate can be delivered throughout the impacted plume zone. Failure to achieve substrate delivery and contact within the chlorinated solvent plume usually re‐sults in wasted money and limited remediation benefit. Bioremediation is a contact technology that cannot be effectively implemented on a large scale unless a method for rapidly delivering the low‐cost substrate across the entire source and plume areas is utilized. Unfortunately, many cur‐rent substrate delivery methods are not achieving sitewide distribution or treatment of the sorbed contaminant mass that exists in the organic fraction of a soil matrix. The following discussion sum‐marizes substrate delivery using an aggressive groundwater recirculation approach that can achieve plumewide contact between the contaminants and substrate, thus accelerating dechlori‐nation rates and shortening the overall remediation time frame. © 2006 Wiley Periodicals, Inc.     

Anticoagulant rodenticide exposure in raptors from Ontario,Canada

Environmental Science and Pollution Research - Anticoagulant rodenticides (ARs) are used globally to control rodent pest infestations in both urban and agricultural settings. It is well documented...     

On estimating the exponent of power-law frequency distributions

Power-law frequency distributions characterize a wide array of natural phenomena. In ecology, biology, and many physical and social sciences, the exponents of these power laws are estimated to draw inference about the processes underlying the phenomenon, to test theoretical models, and to scale up from local observations to global patterns. Therefore, it is essential that these exponents be estimated accurately. Unfortunately, the binning-based methods traditionally used in ecology and other disciplines perform quite poorly. Here we discuss more sophisticated methods for fitting these exponents based on cumulative distribution functions and maximum likelihood estimation. We illustrate their superior performance at estimating known exponents and provide details on how and when ecologists should use them. Our results confirm that maximum likelihood estimation outperforms other methods in both accuracy and precision. Because of the use of biased statistical methods for estimating the exponent, the conclusions of several recently published papers should be revisited.     

Glucosinolates and trichomes track tissue value in two sympatric mustards

Glucosinolates, trichomes, nitrogen, and carbon are not distributed uniformly through the canopies of mustards. In this study, we asked whether glucosinolate concentrations and trichome densities in two sympatric mustards, Brassica kaber and B. nigra, are highest in tissues of greatest value to the plant. We also asked whether nitrogen or carbon content is the stronger predictor of tissue value, and what fraction of each resource is incorporated in glucosinolates. To quantify tissue values, we removed three equal-area fractions (lower, middle, and upper) from the canopies of B. kaber and B. nigra in the greenhouse, as well as whole canopies of naturally growing B. nigra in the field, at two times during growth and measured reductions in their performance relative to controls. We also measured trichome density in both experiments, as well as glucosinolate, nitrogen, and carbon concentrations for the equal-area fractions in the greenhouse. We found that upper leaves had the highest glucosinolate concentrations, trichome densities, and tissue values. Furthermore, young plants in the field had higher trichome densities and tissue values than did older plants. Collectively, these data provide strong support for optimal defense theory and are among the first such evidence for glucosinolates and for physical defenses. The positive relationship between trichome density and tissue value was strong even after we accounted for the effects of leaf expansion. While nitrogen and carbon have both received attention as currencies for trade-offs, our data suggest that nitrogen concentration is a significantly better predictor of tissue value in these two mustard species. Interestingly, <1% of the nitrogen or carbon in leaves was incorporated in glucosinolates, which may explain why glucosinolates lack a consistent response to nitrogen fertilization.     

Estimating survival rates of uncatchable animals: the myth of high juvenile mortality in reptiles

Survival rates of juvenile reptiles are critical population parameters but are difficult to obtain through mark-recapture programs because these small, secretive animals are rarely caught. This scarcity has encouraged speculation that survival rates of juveniles are very low, and we test this prediction by estimating juvenile survival rates indirectly. A simple mathematical model calculates the annual juvenile survival rate needed to maintain a stable population size, using published data on adult survival rates, reproductive output, and ages at maturity in 109 reptile populations encompassing 57 species. Counter to prediction, estimated juvenile survival rates were relatively high (on average, only about 13% less than those of conspecific adults) and highly correlated with adult survival rates. Overall, survival rates during both juvenile and adult life were higher in turtles than in snakes, and higher in snakes than in lizards. As predicted from life history theory, rates of juvenile survival were higher in species that produce large offspring, and higher in viviparous squamates than in oviparous species. Our analyses challenge the widely held belief that juvenile reptiles have low rates of annual survival and suggest instead that sampling problems and the elusive biology of juvenile reptiles have misled researchers in this respect.     

Habitat-mediated foraging limitations drive survival bottlenecks for juvenile salmon

Realistic population models and effective conservation strategies require a thorough understanding of mechanisms driving stage-specific mortality. Mortality bottlenecks for many species occur in the juvenile stage and are thought to result from limitation on food or foraging habitat during a "critical period" for growth and survival. Without a way to account for maternal effects or to measure integrated consumption rates in the field, it has been virtually impossible to test these relationships directly. Hence uncertainties about mechanisms underlying such bottlenecks remain. In this study we randomize maternal effects across sites and apply a new method for measuring consumption integrated over weeks to months to test the hypothesis that food limitation drives early-season juvenile mortality bottlenecks in Atlantic salmon (Salmo salar). Using natural signatures of geologically derived cesium (133Cs), we estimated consumption rates of >400 fry stocked into six streams. Two to four weeks after stocking, consumption was extremely low across sites (0.005 g x g(-1) x d(-1)) and was predicted to be below maintenance rations (i.e., yielding negative energy balances) for the majority of individuals from five of six sites. However, consumption during this time was positively correlated with growth rates and survival (measured at the end of the growing season). In contrast, consumption rates increased in mid- (0.030 g x g(-1) x d(-1)) and late (0.035 g x g(-1) x d(-1)) seasons, but juvenile survival and consumption were not correlated, and correlations between growth and consumption were weak. These findings are consistent with predictions of a habitat-based bioenergetic model constructed using the actual stream positions of the individual fish in the present study, which indicates that habitat-based models capture important environmental determinants of juvenile growth and survival. Hence, by combining approaches, reducing maternal effects and controlling initial conditions, we offer a general framework for linking foraging with juvenile survival and present the first direct consumption-based evidence for the early season bottleneck hypothesis.