Soil Nutrients and Vegetation Characteristics of a Dorset/Thule Site in the Canadian Arctic

We conducted a systematic study of soils and vegetation present at Arnaqquaksaat on Igloolik Island, Nunavut, a site occupied by Dorset and Thule people prior to 1823 and probably for over a thousand years. We compared this site to an area affected by ongoing mammal and bird activity and an area of relatively unfertilized polar semidesert. At these locations, we estimated percent cover of vegetation, identified vascular plant species, measured soil depth, and collected soil samples. The soil samples were analyzed for total nitrogen, sodium bicarbonate-extractable phosphorus, available potassium, available magnesium, and pH.Percent plant cover, abundance of plant species indicative of enrichment, and soil depth were greatest within the area of anthropogenic influence and decreased downslope to the sea. Total nitrogen level in the upslope area of anthropogenic influence (2.61% ±0.88) was similar to that in areas of bird and mammal activity (2.54% ±0.78); it was higher than the levels in the downslope area of human fertilization (0.65% ±0.82) and the unaltered polar semidesert area (0.28% ±0.38). Phosphorus levels in the influenced areas were 5 to 6 times those in the uninfluenced polar semidesert. The magnesium level was highest in the area of bird and mammal activity (766.8 mg/L ±53.35), whereas potassium levels were similar throughout the study area. The lowest pH was found in the upslope area of past human occupation, and pH differences among sites paralleled those observed for nitrogen.On a effectué une étude systématique des sols et de la végétation présents à Arnaqquaksaat dans l'île Igloolik au Nunavut, un site occupé par les peuples de Dorset et de Thulé avant 1823 et probablement durant plus de mille ans. On a comparé ce site à une zone affectée par l'activité continue de mammifères et d'oiseaux et à une zone de semi-désert polaire relativement non fertilisé. À ces endroits, on a évalué le pourcentage de couvert végétal, identifié les espèces de plantes vasculaires, mesuré la profondeur du sol et prélevé des échantillons de sol. On a analysé ces derniers pour en évaluer la teneur en azote total, phosphore extractible par le bicarbonate de soude, potassium disponible, magnésium disponible et le pH. On a trouvé que le pourcentage de couvert végétal, l'abondance d'espèces végétales révélatrice d'un enrichissement et la profondeur du sol étaient les plus importants à l'intérieur de la zone qui avait subi une influence anthropique et qu'ils décroissaient en descendant vers la mer. Le niveau d'azote total dans la zone supérieure de la pente, qui avait subi une influence anthropique (2,61 p. cent ± 0,88), était semblable à celui des zones où s'exerçait l'activité des oiseaux et des mammifères (2,54 p. cent ± 0,78); il était supérieur aux niveaux trouvés dans la partie inférieure qui avait connu une fertilisation humaine (0,65 p. cent ± 0,82) et dans la zone polaire semi-désertique non altérée (0,28 ± 0,38). Les niveaux de phosphore dans les zones ayant subi une influence étaient de 5 à 6 fois ceux des zones semi-désertiques polaires n'ayant pas subi d'influence. Le niveau de magnésium était le plus haut dans la zone où s'exerçait l'activité des oiseaux et des mammifères (766,8 mg/L ± 53,35), alors que les niveaux de potassium étaient semblables dans toute la zone d'étude. Le pH le plus bas se trouvait dans la zone supérieure de l'endroit ayant jadis été occupé par l'être humain, et les différences dans le pH parmi les sites s'alignaient sur celles observées pour l'azote

Variation in calanoid copepod resting egg abundance among lakes with different acidification histories

Abstract The maintenance of species and genetic diversity within zooplankton egg banks may be crucial to the re-establishment of zooplankton communities following historical disturbance, such as anthropogenic acidification which globally caused widespread damage to ecological communities. Despite this, no other study has described basic characteristics of zooplankton egg banks among lakes with different acidification histories, such as variation in resting egg concentration. Theoretically, habitats with frequent periods of harsh environmental conditions are expected to select for resting egg production or prolonged dormancy in zooplankton, which would increase the size of the resting egg bank in lake sediments. In this study, we compared abundances of viable and inviable calanoid copepod resting eggs among three freshwater lakes with different acidification histories. While Swan Lake underwent major chemical and biological changes from acid and metal deposition, Teardrop and Bat lakes were relatively unaffected by historical acidification and had comparatively constant, but different pH over time. We also tested the effect of age on the viability of resting eggs. As predicted, higher numbers of viable resting eggs were found in recent sediments from acid-recovering Swan Lake compared to study lakes with relatively temporally constant environments (Teardrop and Bat lakes) when the total number of eggs was held as a covariate. We detected this result in spite of similar pelagic abundances of Leptodiaptomus minutus, the dominant species in zooplankton communities of these lakes. This pattern did not necessarily hold for inviable egg concentrations since these eggs were more abundant in both Swan and Bat lakes compared to Teardrop Lake in older sediments (1939-1951, 1800s). Within study lakes, the abundance of viable resting eggs declined with increased egg age. Further study is required to test mechanisms underlying these patterns

Synthesis of core–shell polymer particles in supercritical carbon dioxide via iterative monomer addition

A new, robust methodology for the synthesis of polystyrene–poly(methyl methacrylate) (PS–PMMA) core–shell particles using seeded dispersion polymerisation in supercritical carbon dioxide is reported, where the core–shell ratio can be controlled predictably via manipulation of reagent stoichiometry. The key development is the application of an iterative addition of the MMA shell monomer to the pre-prepared PS core. Analysis of the materials with differing core–shell ratios indicates that all are isolated as single particle populations with distinct and controllable core–shell morphologies

Lake salinization drives consistent losses of zooplankton abundance and diversity across coordinated mesocosm experiments

Human-induced salinization increasingly threatens inland waters; yet we know little about the multifaceted response of lake communities to salt contamination. By conducting a coordinated mesocosm experiment of lake salinization across 16 sites in North America and Europe, we quantified the response of zooplankton abundance and (taxonomic and functional) community structure to a broad gradient of environmentally relevant chloride concentrations, ranging from 4 to ca. 1400 mg Cl- L-1. We found that crustaceans were distinctly more sensitive to elevated chloride than rotifers; yet, rotifers did not show compensatory abundance increases in response to crustacean declines. For crustaceans, our among-site comparisons indicate: (1) highly consistent decreases in abundance and taxon richness with salinity; (2) widespread chloride sensitivity across major taxonomic groups (Cladocera, Cyclopoida, and Calanoida); and (3) weaker loss of functional than taxonomic diversity. Overall, our study demonstrates that aggregate properties of zooplankton communities can be adversely affected at chloride concentrations relevant to anthropogenic salinization in lakes.Peer reviewe

Widespread variation in salt tolerance within freshwater zooplankton species reduces the predictability of community-level salt tolerance

The salinization of freshwaters is a global threat to aquatic biodiversity. We quantified variation in chloride (Cl-) tolerance of 19 freshwater zooplankton species in four countries to answer three questions: (1) How much variation in Cl- tolerance is present among populations? (2) What factors predict intraspecific variation in Cl- tolerance? (3) Must we account for intraspecific variation to accurately predict community Cl- tolerance? We conducted field mesocosm experiments at 16 sites and compiled acute LC(50)s from published laboratory studies. We found high variation in LC(50)s for Cl- tolerance in multiple species, which, in the experiment, was only explained by zooplankton community composition. Variation in species-LC50 was high enough that at 45% of lakes, community response was not predictable based on species tolerances measured at other sites. This suggests that water quality guidelines should be based on multiple populations and communities to account for large intraspecific variation in Cl- tolerance.Peer reviewe

Current water quality guidelines across North America and Europe do not protect lakes from salinization

Human-induced salinization caused by the use of road deicing salts, agricultural practices, mining operations, and climate change is a major threat to the biodiversity and functioning of freshwater ecosystems. Yet, it is unclear if freshwater ecosystems are protected from salinization by current water quality guidelines. Leveraging an experimental network of land-based and in-lake mesocosms across North America and Europe, we tested how salinization-indicated as elevated chloride (C-) concentration-will affect lake food webs and if two of the lowest Cl- thresholds found globally are sufficient to protect these food webs. Our results indicated that salinization will cause substantial zooplankton mortality at the lowest Cl- thresholds established in Canada (120 mg Cl-/L) and the United States (230 mg Cl-/L) and throughout Europe where Cl- thresholds are generally higher. For instance, at 73% of our study sites, Cl- concentrations that caused a >= 50% reduction in cladoceran abundance were at or below Cl thresholds in Canada, in the United States, and throughout Europe. Similar trends occurred for copepod and rotifer zooplankton. The loss of zooplankton triggered a cascading effect causing an increase in phytoplankton biomass at 47% of study sites. Such changes in lake food webs could alter nutrient cycling and water clarity and trigger declines in fish production. Current Cl- thresholds across North America and Europe clearly do not adequately protect lake food webs. Water quality guidelines should be developed where they do not exist, and there is an urgent need to reassess existing guidelines to protect lake ecosystems from human-induced salinization.Peer reviewe

Prioritizing taxa for genetic reference database development to advance inland water conservation

Biodiversity loss has accelerated over the past century and freshwater species overall are among those experiencing greatest declines. Genetic resources have the potential to help evaluate the full magnitude of this loss and represent a key tool to effectively allocate conservation resources and monitor the success of restoration efforts. The full power of genetic resources will be realized when the daunting task of referencing all DNA sequences of freshwater organisms is complete. Here, we quantified the availability and distribution of barcode and genome data for freshwater macroscopic organisms in Canada, a country rich in inland water resources and thus particularly vulnerable to aquatic species losses. Impressively, most inland water species (86 %) were represented by barcodes recorded in the BOLD Systems database, while very few had full genomes available (<4 %) in the NCBI database. We identified barcode data deficiencies in northern regions and for taxa assessed as most at risk or without sufficient information for conservation status classification. As expected, the speciose insect group had a lower-than-average number of records per species and a high proportion of data deficient species without adequate barcode coverage. This study highlights where future sequencing resources should be prioritized within initiatives such as the Canada BioGenome Project and BIOSCAN Canada and provides a workflow that could be applied internationally to inform conservation management plans and to mitigate biodiversity loss

Global Patterns and Controls of Nutrient Immobilization On Decomposing Cellulose In Riverine Ecosystems

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature

Causes of maladaptation

Evolutionary biologists tend to approach the study of the natural world within a framework of adaptation, inspired perhaps by the power of natural selection to produce fitness advantages that drive population persistence and biological diversity. In contrast, evolution has rarely been studied through the lens of adaptation's complement, maladaptation. This contrast is surprising because maladaptation is a prevalent feature of evolution: population trait values are rarely distributed optimally; local populations often have lower fitness than imported ones; populations decline; and local and global extinctions are common. Yet we lack a general framework for understanding maladaptation; for instance in terms of distribution, severity, and dynamics. Similar uncertainties apply to the causes of maladaptation. We suggest that incorporating maladaptation-based perspectives into evolutionary biology would facilitate better understanding of the natural world. Approaches within a maladaptation framework might be especially profitable in applied evolution contexts – where reductions in fitness are common. Toward advancing a more balanced study of evolution, here we present a conceptual framework describing causes of maladaptation. As the introductory article for a Special Feature on maladaptation, we also summarize the studies in this Issue, highlighting the causes of maladaptation in each study. We hope that our framework and the papers in this Special Issue will help catalyze the study of maladaptation in applied evolution, supporting greater understanding of evolutionary dynamics in our rapidly changing world

St. Lawrence River zones that are hostile to invasive species can be refuges for native fish

The round goby is an invasive fish that has become established in the St. Lawrence River over the past two decades, following its introduction into the Great Lakes