High Impact Sites Research Articles

Salt Belt Index (SBI): A biotic index for streams within the North American “salt belt,” with proposed baseline chloride thresholds

Road salt (commonly NaCl, CaCl2, and MgCl2) is widely used in the northern United States as a deicing agent for roadways and other byways. Millions of tons of road salt are used annually in the United States, resulting in drastic increases in freshwater salinity. This study aims to determine the chloride optima and tolerance ranges of macroinvertebrates using publicly accessible stream monitoring data from the US EPA. We assigned taxa region-specific tolerance values, which we then used to calculate the Salt Belt Index (SBI). In addition to the SBI, we determined new, region-specific, chronic Cl− thresholds, determined using threshold indicator taxa analysis (TITAN). Using generalized linear models, we found the SBI was highly accurate at estimating chloride concentration (mg/L Cl−) across the salt belt states. Macroinvertebrate community richness exhibited a significant negative relationship with increasing chloride concentrations. Newly proposed chloride thresholds, based on the richness-chloride relationship, were far lower than current thresholds. The SBI was able to differentiate between Low-, Medium-, and High-Impact sites, grouped based on proposed chloride thresholds. Based on our findings, it is clear current salinity thresholds are too high, and management practices should factor in regional variability, taxon-specific physiology, and historical instream chemistry when implementing salinity thresholds.

Reduced amino acid alphabet-based encoding and its impact on modeling influenza antigenic evolution

Currently, vaccination is one of the most efficient ways to control and prevent influenza infection. Vaccine production largely relies on the results of laboratory assays, including hemagglutination inhibition and microneutralization assays, which are time-consuming and laborious. Viruses can escape from the immune response that results in the need to revise and update vaccines biannually. The hemagglutination inhibition assay can measure how effectively antibodies against a reference strain bind and block an antigen of the test strain. Various computer-aided models have been developed to optimize candidate vaccine strain selection. A general problem in modeling of antigenic evolution is the representation of genetic sequences for input into the research model. Our motivation stems from the well-known problem of encoding genetic information for modeling antigenic evolution. This paper introduces a two-fold encoding approach based on reduced amino acid alphabet and amino acid index databases called AAindex. We propose to apply a simplified amino acid alphabet in modeling of antigenic evolution. A simplified alphabet, also called a sub-alphabet or reduced amino acid alphabet, implies to use the 20 amino acids being clustered and divided into amino acid groups. The proposed encoding allows to redefine mutations termed for amino acid groups located in reduced alphabets. We investigated 40 reduced amino acid sets and their performance in modeling antigenic evolution. The experimental results indicate that the proposed reduced amino acid alphabets can achieve the performance of the standard alphabet in its accuracy. Moreover, these alphabets provide deeper insight into various aspects of the relationship between mutation and antigenic variation. By checking identified high-impact sites in the Influenza Research Database, we found that not only antigenic sites have a significant influence on antigenicity, but also other amino acids located in close proximity. The results indicate that all selected non-antigenic sites are related to immune responses. According to the Influenza Research Database, these have been experimentally determined to be T-cell epitopes, B-cell epitopes, and MHC-binding epitopes of different classes. This highlighted a caveat: while simulating antigenic evolution, the model should consider not only the genetic information on antigenic sites, but also that of neighboring positions, as they may indirectly impact antigenicity. Additionally, our findings indicate that structural and charge characteristics are the most beneficial in modeling antigenic evolution, which is in agreement with previous studies.

Biotic resistance of native fouling communities to bioinvasions could not be demonstrated by transplant experiments in Northern Italy

Biotic resistance is considered an important driver in the establishment of non-indigenous species (NIS), but experiments in the marine environment have led to contradictory results. In this context, a transplant experiment of fouling communities was carried out over five months. Settlement panels were moved from low impact (species-rich native communities) to high impact sites by NIS in two Italian areas to test the biotic resistance hypothesis. Fouling communities displayed significant differences among treatments before and after the transplant, thus indicating the maintenance of a peculiar fouling community in transplanted panels. On the other hand, newly recruited species were similar between treatments and neither a facilitation nor a mitigation role from native fouling communities on NIS was observed. Our results highlight the importance to better investigate the factors affecting the high variability obtained in experiments testing this hypothesis, with the aim to identify potential solutions for NIS management in ports.

Spread rates do not necessarily predict outbreak dynamics in a broadly distributed invasive insect

Biological invasions by insects entail several processes including spread and outbreaks that can cause widespread tree mortality. These processes are commonly viewed as a linear sequence because we often lack the mechanistic understanding needed to partition them. We explored an invasion that occurred over a large enough spatial scale and time frame to examine the conditions under which spread rates may be uncoupled from outbreak severity. Lymantria dispar is an invasive generalist folivore that has spread continuously from its initial point of introduction in North America at variable rates. Since its establishment in Wisconsin, USA in 1998, L. dispar has spread more rapidly there than any other region, but has never irrupted into regionwide outbreaks. In contrast, L. dispar spread more slowly elsewhere, in part due to strong mate-finding Allee effects, but periodically undergoes highly damaging, landscape-scale outbreaks in susceptible forest types. We conducted a 10-year study across 45 stands in northern Wisconsin with a high composition of favorable hosts. We quantified population trends of life stages, natural enemy abundance and impacts, and radial tree growth increment, and assessed biotic and abiotic factors as putative drivers of the decoupling between spread rates and outbreak severity. We then compared the results from these rapid-spread, low-impact sites with those from slow-spread, high-impact sites in Michigan and Pennsylvania, USA. The abundance and richness of natural enemy communities in Wisconsin were either equivalent to or less than those communities reported elsewhere, reducing the likelihood that greater top-down control explains the absence of outbreaks. We also found no differences in larval developmental time or drought that could increase the effects of natural enemies among the different regions. Rather, higher overwintering mortality due to more extreme and frequent lethal minimal temperatures in Wisconsin appeared most responsible for the lack of outbreaks. Overall, it appears that the combination of strong mate-finding Allee effects and low overwintering mortality elsewhere is a more substantial hindrance to spread than are weak mate-finding Allee effects and high overwintering mortality in Wisconsin. Once populations are established, the net contributions of these constraints become reversed: mate-finding limitations become only a minimal challenge whereas regional differences in winter survival best explain differences in outbreak frequency. These results suggest that spread rates of invasive insects should not be used as a proxy for predicting their local or overall impact, and that management efforts should be tailored to underlying processes determining their region-specific relative importance.

Woody Plant Communities after 40 Years of Pollution Control and Restoration in Smelter-Denuded Landscapes

Restoration of degraded ecosystems requires assessing the status of the recovery and identifying key factors limiting the recovery. Nearly 4 decades of the reduction in smelter emissions, soil amelioration, and planting of ∼10 million trees and shrubs have led to extensive revegetation of emission-denuded landscapes in the Sudbury area, ON, Canada. To evaluate the state of recovery and identify factors affecting it, we surveyed woody plants and environmental correlates (soil pH, soil nutrient content, and soil metal content) along gradients of historical smelting impacts. Species richness declined from reference sites to high-impact sites, with impact sites having 23–33% fewer species compared to reference sites. Species composition varied along gradients of historical smelting impacts, with the difference attributable to low abundances or absences of one third of the 43 species found in the reference sites. Species richness and composition were associated with soil toxicity (as measured by metal content and pH) but not soil nutrients. However, the negative relationships between soil toxicity and plant community were attributable to the mediation effect of canopy cover, rather than the direct effect of soil toxicity. Sixty three percent of species that were uncommon or absent in impact sites (Abies balsamea [Balsam Fir], Acer pensylvanicum [Striped Maple], Acer spicatum [Mountain Maple], Betula alleghaniensis [Swamp Birch], Fraxinus nigra [Black Ash], Gaultheria procumbens [American Wintergreen], Linnaea borealis [Twinflower], Lonicera canadensis [Fly Honeysuckle], Lonicera hirsute [Hairy Honeysuckle], and Ostrya virginiana [American Hophornbeam]) were shade-tolerant and declined with declining canopy cover. These species were reported to be absent or uncommon in impact sites nearly 4 decades ago. Together, these results suggest that woody plant community has undergone limited recovery and that the recovery is hampered by poorly developed canopy cover rather than direct soil toxicity or nutrient deficiency. Accordingly, strategic interventions of canopy cover-mediated processes (e.g., shading and soil moisture) is needed to facilitate the recovery of the woody plant community in the smelter-denuded landscapes.

“This Class Is Not Just a Class. It Really Is a Community”: The Potential of Online Forums as High-Impact Practices and Sites of Agile Teaching and Learning

“This Class Is Not Just a Class. It Really Is a Community”: The Potential of Online Forums as High-Impact Practices and Sites of Agile Teaching and Learning

PlantDeepSEA, a deep learning-based web service to predict the regulatory effects of genomic variants in plants.

Characterizing regulatory effects of genomic variants in plants remains a challenge. Although several tools based on deep-learning models and large-scale chromatin-profiling data have been available to predict regulatory elements and variant effects, no dedicated tools or web services have been reported in plants. Here, we present PlantDeepSEA as a deep learning-based web service to predict regulatory effects of genomic variants in multiple tissues of six plant species (including four crops). PlantDeepSEA provides two main functions. One is called Variant Effector, which aims to predict the effects of sequence variants on chromatin accessibility. Another is Sequence Profiler, a utility that performs ‘in silico saturated mutagenesis’ analysis to discover high-impact sites (e.g., cis-regulatory elements) within a sequence. When validated on independent test sets, the area under receiver operating characteristic curve of deep learning models in PlantDeepSEA ranges from 0.93 to 0.99. We demonstrate the usability of the web service with two examples. PlantDeepSEA could help to prioritize regulatory causal variants and might improve our understanding of their mechanisms of action in different tissues in plants. PlantDeepSEA is available at http://plantdeepsea.ncpgr.cn/.

Multi-trophic level responses to environmental stressors over the past ~150 years: Insights from a lake-rich region of the world

Multiple stressors affect water quality and biodiversity in lakes worldwide. However, our understanding of which combinations of stressors are of greatest impact and how lakes have shifted from their pre-industrial baselines is fragmented. Questions remain regarding how multiple trophic groups are affected by global change stressors and whether region-specific differences need to be considered. Here, we apply multiple factor analyses together with latent variable modeling to quantify potential interactions within and among taxa that span multiple trophic levels (i.e. diatoms, cladocerans and chironomids) to improve our understanding of paleo-environmental dynamics from a suite of Canadian lakes spanning four ecozones: the Boreal Shield, the Mixedwood Plains, the Atlantic Highlands, and the Atlantic Maritimes. Across all ecozones, multi-trophic assemblages were distinguished in a multiple factor analysis along a land-use gradient, with mesotrophic/eutrophic diatoms and profundal chironomids tolerant of low bottom-water oxygen concentrations recorded in more disturbed sites. Functional units across three indicator groups formed distinct networks of co-responses to key environmental and land-use gradients, although cladocerans seemed to be driven by additional (i.e., residual) gradients. Applying a temporal beta-diversity approach between modern and pre-industrial assemblages, we detected significantly greater turnover of diatom functional groups in high versus low human impact sites (p = 0.03, n = 57), with similar but non-significant trends apparent with the chironomid and cladoceran groups. Ecozonal differences in temporal turnover were also evident in diatom (p = 0.003, n = 57) and chironomid functional groups (p = 0.04, n = 41). The ecozonal differences may be partially due to differential sensitivities of the pre-industrial assemblages and may also be driven by historical disturbances. Our work highlights how the magnitude and direction of ecological change vary across ecozones and can modify responses to human impacts, with a general trend of higher species turnover in sites with greater human disturbance.

Pycnogonida (Arthropoda) from Northern Adriatic Corallina officinalis Linnaeus, 1758 belts

We studied Pycnogonida, sea spiders, collected from 54 samples of Corallina officinalis belts in the vicinity of Pula and the Brijuni National Park representing both exposed and sheltered localities as well as different levels of human impact. Seven species were identified, namely Achelia echinata, A. langi, Tanystylum conirostre, Anoplodactylus angulatus, A. pygmaeus, Trygaeus communis, and Callipallene tiberi. As we used a quantifiable standard sample size of 5 cm2, we could perform a statistical analysis of species richness and abundances. The exposed low human impact sites showed a significantly higher amount of both, specimens and species than the sheltered high impact sites. C. tiberi and A. echinata showed a significant preference for exposed low impact sites while T. conirostre was equally distributed among the habitat subtypes.

InSAR Campaign Reveals Ongoing Displacement Trends at High Impact Sites of Thessaloniki and Chalkidiki, Greece

We studied the broader area of Thessaloniki in northern Greece and Chalkidiki and performed an InSAR campaign to study the surface deformation phenomena that have been known to exist for at least two decades. Sentinel-1 data (2015–2019) together with drill measurements were exploited to focus on specific sites of interest. Our results indicate an ongoing displacement field. At the region of Kalochori and Sindos—where intense subsidence in the 1990s was previously found to have had a natural surface rebound in the 2000s—a new period of subsidence, caused by the enlivenment of the groundwater overexploitation, was reported. The uplifting trend of Oreokastro is still active and subsidence in Anthemountas graben is ongoing; special focus was set on the Makedonia Airport, where significant displacement is occurring. The study also reveals a new area at Nea Moudania, that was not known previously to deform; another case corresponding to anthropogenic-induced surface displacement. Thessaloniki is surrounded by different persistent displacement phenomena, whose main driving mechanisms are anthropogenic. The sensitivity of the surface displacements to the water trends is highlighted in parts of the study area. Results highlight the plan of a water resources management as a high priority for the area.

Exploring the use of nuclear alterations, motility and ecological guilds in epipelic diatoms as biomonitoring tools for water quality improvement in urban impacted lowland streams

Abstract In this study we explored the use of less conventional diatom metrics (motility, nuclear abnormalities and ecological guilds) to measure changes in diatom assemblages related to the transfer of epipelic communities from urban impacted streams to less impacted sites. Three lowland streams in the Argentine Pampean plain were selected, and two sites were established per stream for a total of six sites. Three sites were referenced as low urban impact (LI), as they run through peri-urban areas, and three downstream sites were referenced as high impact sites (HI), since they run through a dense urban area. Six germination trays filled with stream sediment were placed at each HI site, and three at each LI site, and left to be colonized for 30 days before transferring three trays from the HI sites to their respective LI site upstream. Samples were collected at days 0, 15, 30 and 45 days from each tray, and diatom species were identified and classified into ecological guilds. Motility variables were measure per individual of the genera Nitzschia (path length, velocity and maximum velocity) through video recording. Also, the frequency of abnormal nuclear locations and nuclear membrane breakage were determined. Results showed that there were no significant differences in any motility metrics, while the nuclei variables exhibited higher proportion of abnormally positioned nuclei and nuclear membrane breakage at the HI sites. The proportion of nuclear membrane breakage decreased over time in the translocated assemblage, indicating that it could be a sensitive indicator of water quality improvement, while the ecological guilds showed significant differences on the proportion of high profile and motile diatoms. The improvement in water quality produced a significative increase in the proportion of the high profile guild in the translocated biofilm. Despite the motile forms being the dominant group, the water quality improvement allowed the high profile forms, to colonize the substrate. These results emphasize the possible use of the ecological guilds as a suitable indicator of water quality improvement in Pampean streams, especially in nutrient rich environment. These tools can provide a rapid assessment of diatom condition and could be considered supplementary to biomonitoring protocols in lowland streams.

Deer Indirectly Alter the Reproductive Strategy and Operational Sex Ratio of an Unpalatable Forest Perennial.

Environmental conditions impose restrictions and costs on reproduction. Multiple reproductive options exist when increased reproductive costs drive plant populations toward alternative reproductive strategies. Using 4 years of demographic data across a deer impact gradient, where deer alter the abiotic environment, we parameterize a size-dependent integral projection model for a sexually labile and unpalatable forest perennial to investigate the demographic processes driving differentiation in the operational sex ratio (OSR) of local populations. In addition to a relative increase in asexual reproduction, our results illustrate that nontrophic indirect effects by overabundant deer on this perennial result in delayed female sex expression to unsustainably large plant sizes and lead to more pronounced plant shrinkage following female sex expression, effectively increasing the cost of reproduction. Among plants of reproductive age, increased deer impact decreases the size-dependent probability of flowering and reduces reproductive consistency over time. This pattern in sex expression skews populations toward female-biased OSRs at low deer impact sites and male-biased OSRs at intermediate and high deer impact sites. While this shift toward a male-biased OSR may ameliorate pollen limitation, it also decreases the effective population size when coupled with increased asexual reproduction. The divergence of reproductive strategies and reduced lifetime fitness in response to indirect deer impacts illustrate the persistent long-term effects of overabundant herbivores on unpalatable understory perennials.

Responses by Atlantic Ghost Crab (Ocypode quadrata) Populations to Hurricane Impacts on a Texas Beach: A 10-Year Study

The Atlantic ghost crab (Ocypode quadrata) is a widely distributed predator and scavenger along Atlantic Ocean and Gulf Coast beaches. A long-term study was initiated on the Bolivar Peninsula of Texas in 2006 to assess the impact of human activity on ghost crabs. Line transects were used to determine crab burrow arrangement at a high-impact site and a low-impact site. Differences were found between the two sites in number of active burrows per transect, burrow density, the diameter of burrow openings, burrow distance to the high-water line, and nearest-neighbor distances. In Fall 2008, Hurricane Ike struck the study sites. Re-examinations of the sites in 2010 showed changes in ghost crab burrows. The high-impact site experienced a decline in human activity – beach width increased by > 50%, the number of burrows/transect tripled, and nearest-neighbor distances decreased by one-third. The hurricane also reshaped the low-impact site on the western tip of the peninsula as beach width decreased by two-thirds, burrow density increased by sevenfold, and nearest-neighbor distances decreased by one-half. Sampling in 2012, 2014, and 2016 show that some of the physical characteristics of the beach gradually returned to near pre-hurricane status. However, reduced beach space at the low-traffic site remained, with higher burrow density and reduced crab size persisting 8 years after the hurricane, and the post-storm reduction in human traffic in the high-impact site has maintained higher burrow density there even as traffic increased. Monitoring the ecological impact of hurricanes is of growing importance as global climate change could lead to increased frequency and severity of tropical storms.

Transplant Trials of the Fan MusselPinna nobilisInside the Coastal Lagoon of Capo Peloro (Central Mediterranean, Italy)

The fan mussel Pinna nobilis is threatened by several anthropogenic disturbances that are only partially mitigated by current conservation measures. In the Faro Lake Natural Reserve, the fan mussel population suffers from insufficient recruitment while, due to periodic dredging, a high larval supply within the canals does not support a stable population. In the present study, a robust number of fan mussel specimens were transplanted from a high-impact site to a guarded area to test the effects of transplantation on future conservation efforts. Over a 12-mo period, high survival and elevated growth were observed in the test population in comparison with the local population, demonstrating transplantation as a feasible and efficient method to prevent P. nobilis population decline. Such small-scale experiments provide useful indications for better management approaches for both of the threatened species and the natural hosting environment.

Returning to normal? Assessing transcriptome recovery over time in male rainbow darter (Etheostoma caeruleum) liver in response to wastewater-treatment plant upgrades.

The present study measured hepatic transcriptome responses in male rainbow darter (Etheostoma caeruleum) exposed to 2 municipal wastewater-treatment plants (MWWTPs; Kitchener and Waterloo) over 4 fall seasons (2011-2014) in the Grand River (Ontario, Canada). The overall goal was to determine if upgrades at the Kitchener MWWTP (in 2012) resulted in transcriptome responses indicative of improved effluent quality. The number of differentially expressed probes in fish downstream of the Kitchener outfall (904-1223) remained comparable to that downstream of Waterloo (767-3867). Noteworthy was that year and the interaction of year and site explained variability in more than twice the number of transcripts than site alone, suggesting that year and the interaction of year and site had a greater effect on the transcriptome than site alone. Gene set enrichment analysis revealed a gradual reduction in the number of gene ontologies over time at exposure sites, which corresponded with lower contaminant load. Subnetwork enrichment analysis revealed that there were noticeable shifts in the cell pathways differently expressed in the liver preupgrade and postupgrade. The dominant pathways altered preupgrade were related to genetic modifications and cell division, whereas postupgrade they were associated with the immune system, reproduction, and biochemical responses. Molecular pathways were dynamic over time, and following the upgrades, there was little evidence that gene expression profiles in fish collected from high-impact sites postupgrade were more similar to those in fish collected from reference site. Environ Toxicol Chem 2017;36:2108-2122. © 2017 SETAC.

Water quality following extensive beetle-induced tree mortality: Interplay of aromatic carbon loading, disinfection byproducts, and hydrologic drivers

The recent bark beetle epidemic across western North America may impact water quality as a result of elevated organic carbon release and hydrologic shifts associated with extensive tree dieback. Analysis of quarterly municipal monitoring data from 2004 to 2014 with discretization of six water treatment facilities in the Rocky Mountains by extent of beetle impact revealed a significant increasing trend in total organic carbon (TOC) and total trihalomethane (TTHM) production within high (≳50% areal infestation) beetle-impacted watersheds while no or insignificant trends were found in watersheds with lower impact levels. Alarmingly, the TTHM concentration trend in the high impact sites exceeded regulatory maximum contaminant levels during the most recent two years of analysis (2013–14). To evaluate seasonal differences, explore the interplay of water quality and hydrologic processes, and eliminate variability associated with municipal reporting, these treatment facilities were targeted for more detailed surface water sampling and characterization. Surface water samples collected from high impact watersheds exhibited significantly higher TOC, aromatic signatures, and disinfection byproduct (DBP) formation potential than watersheds with lower infestation levels. Spectroscopic analyses of surface water samples indicated that these heightened DBP precursor levels are a function of both elevated TOC loading and increased aromatic character. This association was heightened during precipitation and runoff events in high impact sites, supporting the hypothesis that altered hydrologic flow paths resulting from tree mortality mobilize organic carbon and elevate DBP formation potential for several months after runoff ceases. The historical trends found here likely underestimate the full extent of TTHM shifts due to monitoring biases with the extended seasonal release of DBP precursors increasing the potential for human exposure. Collectively, our analysis suggests that while water quality impacts continue to rise nearly one decade after infestation, significant increases in TOC mobilization and DBP precursors are limited to watersheds that experience extensive tree mortality.

Differential proteomic response of Sydney rock oysters (Saccostrea glomerata) to prolonged environmental stress

Exposure to prolonged environmental stress can have impacts on the cellular homeostasis of aquatic organisms. The current study employed two-dimensional electrophoresis (2-DE) to test whether exposure to impaired water quality conditions in the Sydney Harbour estuary has significantly altered the proteomes of the resident Sydney rock oyster (Saccostrea glomerata). Adult S. glomerata were sampled from four bays in the estuary. Each bay consisted of a “high-impact” site adjacent to point sources of chemical contamination (e.g., storm drains/canals or legacy hotspots) and a “low-impact” site located ∼5km away from point sources. A mixture of environmental stressors differed significantly between high- and low-impact sites. Specifically, PAHs, PCBs, tributyltin, Pb, and Zn were significantly elevated in oyster tissues from high-impact sites, together with depleted dissolved oxygen and low pH in the water column. A 2-DE proteomics analysis subsequently identified 238 protein spots across 24 2-DE gels, of which 27–50 spots differed significantly in relative intensity between high- and low-impact sites per bay. Twenty-five percent of the differential spots were identified in more than one bay. The identities of 80 protein spots were determined by mass spectrometry. HSP 70, PPIB, and radixin were the three most highly expressed differential proteins. Despite the largely unique proteomes evident in each bay, functional annotations revealed that half of the differentially expressed proteins fell into just two subcellular functional categories—energy metabolism and the cytoskeleton. These findings provide a framework to further investigate adaptation of cellular mechanisms to prolonged stress in S. glomerata.

A meta-analysis reveals a positive correlation between genetic diversity metrics and environmental status in the long-lived seagrass Posidonia oceanica.

The seagrass Posidonia oceanica is a key engineering species structuring coastal marine systems throughout much of the Mediterranean basin. Its decline is of concern, leading to the search for short- and long-term indicators of seagrass health. Using ArcGIS maps from a recent, high-resolution (1-4 km) modelling study of 18 disturbance factors affecting coastal marine systems across the Mediterranean (Micheli et al. 2013, http://globalmarine.nceas.ucsb.edu/mediterranean/), we tested for correlations with genetic diversity metrics (allelic diversity, genotypic/clonal diversity and heterozygosity) in a meta-analysis of 56 meadows. Contrary to initial predictions, weak but significantly positive correlations were found for commercial shipping, organic pollution (pesticides) and cumulative impact. This counterintuitive finding suggests greater resistance and resilience of individuals with higher genetic and genotypic diversity under disturbance (at least for a time) and/or increased sexual reproduction under an intermediate disturbance model. We interpret the absence of low and medium levels of genetic variation at impacted locations as probable local extinctions of individuals that already exceeded their resistance capacity. Alternatively, high diversity at high-impact sites is likely a temporal artefact, reflecting the mismatch with pre-environmental impact conditions, especially because flowering and sexual recruitment are seldom observed. While genetic diversity metrics are a valuable tool for restoration and mitigation, caution must be exercised in the interpretation of correlative patterns as found in this study, because the exceptional longevity of individuals creates a temporal mismatch that may falsely suggest good meadow health status, while gradual deterioration of allelic diversity might go unnoticed.

Body size, nuptial pad size and hormone levels: potential non-destructive biomarkers of reproductive health in wild toads (Bufo bufo)

Amphibians are declining and fertility/fecundity are major drivers of population stability. The development of non-destructive methods to assess reproductive health are needed as destructive measures are fundamentally at odds with conservation goals for declining species. We investigated the utility of body size, nuptial pad size and forelimb width as non-destructive biomarkers of internal reproductive physiology, by analysing correlations with commonly used destructive methods in adult male toads (Bufo bufo) from a low human impact and a high human impact site. Principal component analyses revealed that size was the most important variable for explaining inter-individual differences in other measured endpoints, both non-destructive and destructive, except for hormone levels and nuptial pad, which were independent of size. Toads from the LI and the HI site differed in almost all of the measured endpoints; this was largely driven by the significantly smaller size of toads from the HI site. Correlational analyses within sites revealed that size was correlated with several reproductive endpoints in toads from the HI site but not the LI site, indicating a possible limiting effect of size on reproductive physiology. Intersex was observed in 33% of toads from the HI site and incidence was not related to any other measured endpoint. In conclusion, we provide evidence that size is associated with reproductive physiology and that nuptial pad/hormone levels have potential as additional markers due to their independence from size. We also show that human activities can have a negative effect on reproductive physiology of the common toad.

Density, Shell Use and Species Composition of Juvenile Fiddler Crabs (Uca spp.) at Low and High Anthropogenic Impact Salt Marsh Sites

Coastal wetlands worldwide have been negatively impacted by humans, causing decreases in the vegetation used as a refuge from predation by juveniles of many species. This study examined juvenile fiddler crab densities and species composition (Uca pugnax, Uca pugilator, and Uca minax), and their use of gastropod shells (Littorina littoraria), at three low and three high impact sites on barrier islands in southeast Georgia. On six dates in June–August 2010, samples were taken from 10 quadrats (1 m2) at each site to determine juvenile fiddler crab densities and species composition, as well as gastropod shell densities and percent shell use. Multiplex PCR was used to identify juvenile fiddler crabs to species. Juvenile fiddler crab densities were lower at high impact sites, while gastropod shell densities and shell use were similar at both low and high impact sites. Species compositions differed between low and high impact sites on the substrate and in shells, with more U. pugilator and U. minax at high impact sites. A change in fiddler crab densities and species composition could cause a substantial change in southeastern salt marshes.