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- OPEN ACCESSTotal Zn concentrations and Zn isotope ratios were measured, using multicollector inductively coupled plasma (ICP)-mass spectrometry (MS), in three species of aquatic insects collected from a stream in Peterborough, Ontario, Canada. Total Zn levels averaged 193 ± 88 μg/g dry weight (dw) in water striders (Heteroptera: Gerridae, Aquarius remigis) and were significantly higher than the concentrations measured in stonefly nymphs (Plecoptera: Perlidae, Acroneuria abnormis) and caddisfly larvae (Trichoptera: Limnephilidae, Pycnopsyche guttifer), i.e., 136 ± 34 μg/g dw and 125 ± 26 μg/g dw, respectively. Average delta values for 66Zn/64Zn in the water striders were approximately 0.7‰ lighter (−1.2‰ ± 1.0‰) and were significantly different than those measured for stoneflies (−0.45‰ ± 0.62‰) and caddisflies (−0.51‰ ± 0.54‰). Nitrogen isotope ratios were significantly different (P < 0.05) among the three species suggesting differences in trophic positioning. Similar to the Zn isotope ratios, δ 13C values for the water striders (−28.61‰ ± 0.98‰) were significantly different than those of the stoneflies and caddisflies, i.e., −30.75‰ ± 1.33‰ and −30.68‰ ± 1.01‰, respectively. The data suggest that the differences observed in Zn ratios relate to food source for these insects. Similar to their carbon sources, Zn in water striders appears to be primarily of terrestrial origin, and of aquatic origin for the other two species.
- OPEN ACCESSOceanic circulation patterns shape both the distribution of species and spatial patterns of intraspecific genetic variation by influencing passively dispersed marine invertebrates. In the northwest Atlantic, strong and consistent currents at the mouth of the Bay of Fundy are expected to restrict dispersal in this region, but the relationship between populations of high dispersal species along the surrounding coastal regions has been largely underrepresented in the phylogeographic literature. We analyzed phylogeographic patterns in two intertidal invertebrates with high dispersal abilities, Tritia obsoleta (Mollusca: Gastropoda) and Macoma petalum (Mollusca: Bivalvia), between Cape Cod and the Gulf of St. Lawrence using mitochondrial DNA (mtDNA). Hierarchical analysis of molecular variance revealed population structuring among regions defined by circulation patterns, highly divergent lineages within M. petalum, and strong concordant genetic subdivision in both species between the Bay of Fundy and Gulf of Maine. Our results suggest that the gyre at the mouth of the bay is influential in restricting alongshore dispersal, allowing genetic divergence between regions to arise through genetic drift. These findings are concordant with biogeographic and phylogeographic studies of other marine organisms, suggesting that the genetic isolation of widely distributed species may be a common feature of intertidal invertebrate communities in the Bay of Fundy.
- OPEN ACCESSMicroplastic pollution is prevalent in the Ottawa River, with all open water samples (n = 62) and sediment samples (n = 10) containing microplastics. The median microplastic concentration of nearshore 100 L water samples was 0.1 fragments per L (ranged between 0.05 and 0.24 fragments per L). The larger volume Manta trawls samples taken in the middle of the Ottawa River had an overall mean concentration of plastics of 1.35 fragments per m3. Plastic concentrations were significantly higher downstream of the wastewater treatment plant (1.99 fragments per m3) compared with upstream of the effluent output (0.71 fragments per m3), suggesting that the effluent plume is a pathway for plastic pollution to the Ottawa River. The mean concentration of microplastic fragments recovered in the sediment samples was 0.22 fragments per g dry weight. The abundance of microplastics in the sediment was not significantly related to the mean particle size or the organic content of the sediment. The most common form of plastic particles found was microfibers. These made up between 70% and 100% of all plastic particles observed, although plastic microbeads and secondary plastic fragments were also recovered.
- OPEN ACCESSLife history theory predicts selection for higher reproductive investment in response to increased mortality among mature individuals. We tested this prediction over the period from 1978 to 2013 for three populations of Atlantic cod (Gadus morhua) off Newfoundland. These populations were heavily fished for a long period. We considered changes in standardized gonad weight as a proxy for changes in gonadal investment. We accounted for the allometry between gonad and body weight, individual body condition, water temperature, and potential spatial and density-dependent effects. Males display significant temporal trends in gonadal investment in all populations; in agreement with theoretical predictions, these trends show increased gonadal investments during the earlier part of the time series when mortality was high, with the trends leveling off or reversing after the later imposition of fishing moratoria. In contrast, females display patterns that are less consistent and expected; significant trends are detected only when accounting for density-dependent effects, with females in two populations unexpectedly showing a long-term decline in gonadal investment. Our results support the hypothesis that fisheries-induced evolution has occurred in gonadal investment in males, but not in females, and suggest that gonadal investment is more important for male reproductive success than expected in this lekking species.
- OPEN ACCESS
- Michael R.S. Coffin,
- Simon C. Courtenay,
- Kyle M. Knysh,
- Christina C. Pater, and
- Michael R. van den Heuvel
In this study, we examined the effects of dissolved oxygen, via metrics based on hourly measurements, and other environmental variables on invertebrate assemblages in estuaries spanning a gradient of nutrient loading and geography in the southern Gulf of St. Lawrence, Canada. Upper areas (15–25 practical salinity units (PSU)) of 13 estuaries that were dominated by either seagrass (Zostera marina Linnaeus, 1753) or macroalgae (Ulva spp. Linnaeus, 1753) were sampled from June to September 2013. Macroinvertebrate assemblages from Z. marina were found to be distinct from Ulva assemblages for both epifauna and infauna. Small snails dominated each vegetation type, specifically cerithids in Z. marina and hydrobids in Ulva. Although Z. marina had higher species richness, approximately 70% of species were common to both habitats. Faunal communities differed among estuaries with large, within-estuary, temporal variance only observed at Ulva sites impacted by hypoxia and particularly at sites with long water residence time. Indeed, abundances varied by several orders of magnitude in Ulva ranging from zero to thousands of macroinvertebrates. There was a strong negative correlation between hypoxic or anoxic water, 48 h prior to sampling, with relative abundances of amphipods, and a positive correlation with the relative abundances of snails. As one of the first studies to use high-frequency oxygen monitoring, this study revealed probable impacts and the transient nature of hypoxia in eutrophication. - OPEN ACCESS
Age matters: Submersion period shapes community composition of lake biofilms under glyphosate stress
The phosphonate herbicide glyphosate, which is the active ingredient in the commercial formulation Roundup®, is currently the most globally used herbicide. In aquatic ecosystems, periphytic biofilms, or periphyton, are at the base of food webs and are often the first communities to be in direct contact with runoff. Microcosm experiments were conducted to assess the effects of a pulse exposure of glyphosate on community composition and chlorophyll a concentrations of lake biofilms at different colonization stages (2 months, 1 year, and 20 years). This is the first study that uses such contrasting submersion periods. Biofilms were exposed to either environmental levels of pure analytical grade glyphosate (6 μg/L, 65 μg/L, and 600 μg/L) or to corresponding phosphorus concentrations. Community composition was determined by deep sequencing of the 18S and 16S rRNA genes to target eukaryotes and cyanobacteria, respectively. The results showed that submersion period was the only significant contributor to community structure. However, at the taxon level, the potentially toxic genus Anabaena was found to increase in relative abundance. We also observed that glyphosate releases phosphorus into the surrounding water, but not in a bioavailable form. The results of this study indicate that environmental concentrations of glyphosate do not seem to impact the community composition or metabolism of lake biofilms under pulse event conditions. - OPEN ACCESS
- Beth C. Norman,
- Paul C. Frost,
- Graham C. Blakelock,
- Scott N. Higgins,
- Md Ehsanul Hoque,
- Jennifer L. Vincent,
- Katarina Cetinic, and
- Marguerite A. Xenopoulos
Silver nanoparticles (AgNPs) are an emerging class of contaminants with the potential to impact ecosystem structure and function. AgNPs are antimicrobial, suggesting that microbe-driven ecosystem functions may be particularly vulnerable to AgNP exposure. Predicting the environmental impacts of AgNPs requires in situ investigation of environmentally relevant dosing regimens over time scales that allow for ecosystem-level responses. We used 3000 L enclosures installed in a boreal lake to expose plankton communities to chronic and pulse AgNP dosing regimens with concentrations mimicking those recorded in natural waters. We compared temporal patterns of plankton responses, Ag accumulation, and ecosystem metabolism (i.e., daily ecosystem respiration, gross primary production, and net ecosystem production) for 6 weeks of chronic dosing and 3 weeks following a pulsed dose. Ag accumulated in microplankton and zooplankton, but carbon-specific Ag was nonlinear over time and generally did not predict plankton response. Ecosystem metabolism did not respond to either AgNP exposure type. This lack of response corresponded with weak microplankton responses in the chronic treatments but did not reflect the stronger microplankton response in the pulse treatment. Our results suggest that lake ecosystem metabolism is somewhat resistant to environmentally relevant concentrations of AgNPs and that organismal responses do not necessarily predict ecosystem-level responses. - OPEN ACCESS
- Alison Mikulyuk,
- Ellen Kujawa,
- Michelle E. Nault,
- Scott Van Egeren,
- Kelly I. Wagner,
- Martha Barton,
- Jennifer Hauxwell, and
- M. Jake Vander Zanden
Invasive species are known to have negative ecological effects. However, few studies have evaluated the impacts of invasive species relative to the effects of invasive species control, thereby limiting our ability to make informed decisions considering the benefits and drawbacks of a given management approach. To address this gap, we compared the ecological effects of the invasive aquatic plant Eurasian watermilfoil (Myriophyllum spicatum L.) with the effects of lake-wide herbicide treatments used for M. spicatum control using aquatic plant data collected from 173 lakes in Wisconsin, USA. First, a pre–post analysis of aquatic plant communities found significant declines in native plant species in response to lake-wide herbicide treatment. Second, multi-level modeling using a large data set revealed a negative association between lake-wide herbicide treatments and native aquatic plants, but no significant negative effect of invasive M. spicatum. Taken together, our results indicate that lake-wide herbicide treatments aimed at controlling M. spicatum had larger effects on native aquatic plants than did the target of control—invasive M. spicatum. Our comparison reveals an important management tradeoff and encourages careful consideration of how we balance the real and perceived impacts of invasive species and the methods used for their control. - OPEN ACCESSRoad salt runoff is a leading cause of secondary freshwater salinization in north temperate climates. Increased chloride concentrations in freshwater can be toxic and lead to changes in organismal behavior, lethality, biotic homogenization, and altered food webs. High chloride concentrations have been reported for winter months in urban centers, as road density is highest in cities. However, summer chloride conditions are not typically studied as road salt is not actively applied outside of winter months, yet summer is when many taxa reproduce and are most sensitive to chloride. In our study, we test the spatial variability of summer chloride conditions across four watersheds in Toronto, Canada. We find 89% of 214 sampled sites exceeded the federal chronic exposure guidelines for chloride, and 13% exceeded the federal acute guidelines. Through a model linking concentration to cumulative proportion of impacted species, we estimate 34% of sites show in excess of one-quarter of all species may be impacted by their site-specific chloride concentrations, with up to two-thirds of species impacted at some sites. Our results suggest that even presumed low seasons for chloride show concentrations sufficient to cause significant negative impacts to aquatic communities.
- OPEN ACCESS
- Jessica Garzke,
- Ian Forster,
- Sean C. Godwin,
- Brett T. Johnson,
- Martin Krkošek,
- Natalie Mahara,
- Evgeny A. Pakhomov,
- Luke A. Rogers, and
- Brian P.V. Hunt
Migrating marine taxa encounter diverse habitats that differ environmentally and in foraging conditions over a range of spatial scales. We examined body (RNA/DNA, length-weight residuals) and nutritional (fatty acid composition) condition of juvenile sockeye salmon (Oncorhynchus nerka) in British Columbia, while migrating through oceanographically variable waters. Fish were sampled in the stratified northern Strait of Georgia (NSoG); the highly mixed Johnstone Strait (JS); and the transitional zone of Queen Charlotte Strait (QCS). In 2015, body and nutritional condition were high in the NSoG but rapidly declined to reach lowest levels in JS where prey availability was low, before showing signs of compensatory growth in QCS. In 2016, juvenile salmon had significantly lower condition in the NSoG than in 2015, although zooplankton biomass was similar, condition remained low in JS, and no compensatory growth was observed in QCS. We provide evidence that differences in juvenile salmon condition between the two years were due to changes in the food quality available to juvenile fish. We propose that existing hypotheses about fish survival need to be extended to incorporate food quality in addition to quantity to understand changes in fish condition and survival between years. - OPEN ACCESSHuman access to surface water resources in the Northern Great Plains (NGP) is challenged by availability and quality, and ecosystem health objectives for these characteristics have not been well developed. Here, we present a predictive multivariate model using the reference condition approach to inform goals for ecosystem health assessment. Benthic communities and abiotic variables were collected at 280 potential reference sites and 8 test sites, and of these, reference sites with least amount of human activity (n = 83) were classified into three community groups and summary metrics. Discriminant function analysis and cross-validation determined that stream order and ecoregion predicted 68.7% of the sites correctly, thus enabling comparison of sites with unknown condition to reference site groups. We then evaluated metrics through Test Site Analysis and stressor gradient analysis in each biological group. Beetle and amphipod fauna were found to be important for condition assessment in addition to traditional metrics of species richness, abundance, detritivory, Ephemeroptera/Plecoptera/Trichoptera dominance, and assemblage composition. These results provide least disturbed reference condition and ecological insights into land use impacts in the NGP. Ultimately, this model is an effective tool for evaluating biotic condition, enables prioritizing river management strategies, and can quantify the efficacy of mitigation measures.
- OPEN ACCESS
- Travis G. Gerwing,
- Lily Campbell,
- Diana J. Hamilton,
- Myriam A. Barbeau,
- Gregory S. Norris,
- Sarah E. Dudas, and
- Francis Juanes
While trophic and habitat-related abiotic variables (predation, competition, tolerance, etc.) are known to influence community structure in many ecosystems, some systems appear to be only minimally influenced by these variables. Sampling multiple tidal flat communities in northern BC, Canada, we investigated the relative importance of top-down and middle-out (mesopredators) variables, competition for resources (bottom up), and abiotic variables in structuring an infaunal community (invertebrates living in sediment). Similar to previous studies on mudflats in the Bay of Fundy (also at a north temperate latitude), we determined that these variables accounted for a minor (0%–9%) proportion of the observed variation in this infaunal community, suggesting that these variables play a small role in structuring this community. Based on the results of our study and in combination with previous experiments on infaunal recovery patterns post disturbance, we posit that the main factors influencing these infaunal communities likely operate at a scale of sites (kilometres) and(or) plot (metres or less) but not transects (10–100 m within site). Candidate forces structuring these intertidal communities that need future examination include regional species pools and the variables that affect these pools, sediment biogeochemistry, and disturbance/recovery history of a site. The similarity of our Pacific coast findings to those from the north temperate Atlantic coast suggests some similarity in the processes structuring these distinct infaunal communities. - OPEN ACCESSBenthic macroinvertebrate communities, which include unionid freshwater mussels, enhance the health of river ecosystems. Human impacts have driven declines within freshwater mussel communities and due to their complex life cycles, mussel recovery efforts are complex. In Canada, conservation of imperiled species has focused on biodiversity hotspots such as the Sydenham River in the Laurentian Great Lakes Basin. In practice, species conservation and habitat monitoring are siloed between federal agencies and local conservation authorities, limiting the potential for alignment of conservation policy and practice. Here we bring together federal, local, and our own survey data to explore patterns of co-occurrences between mussel species and other macroinvertebrate taxa to explore the extent to which knowledge of one benthic community informs the other. Mussel communities (species richness, community composition) differed between sites where imperiled mussel species were present and/or absent. Benthic macroinvertebrate metrics (e.g., family richness, percent Ephemeroptera, Plecoptera, and Trichoptera taxa) and specific indicator taxa were correlated with mussel species richness and the presence of imperiled mussel species. We show that benthic macroinvertebrate diversity indicators provided insight into imperiled species occurrences that warrant further investigation. These findings underscore support for coordinated watershed monitoring efforts and could be crucial for more successful freshwater mussel conservation.
- OPEN ACCESS
- Emily M. Rubidge,
- Carrie K. Robb,
- Patrick L. Thompson,
- Chris McDougall,
- Karin M. Bodtker,
- Katie S.P. Gale,
- Stephen Ban,
- Kil Hltaanuwaay Tayler Brown,
- Vicki Sahanatien,
- Sachiko Ouchi,
- Sarah K. Friesen,
- Natalie C. Ban,
- Karen L. Hunter,
- Angelica Pena,
- Amber Holdsworth, and
- Rebecca Martone
Marine protected area (MPAs) networks can buffer marine ecosystems from the impacts of climate change by allowing species to redistribute as conditions change and by reducing other stressors. There are, however, few examples where climate change has been considered in MPA network design. In this paper, we assess how climate change considerations were integrated into the design of a newly released MPA network in the Northern Shelf Bioregion in British Columbia, Canada, and then evaluate the resulting network against projected physical and biogeochemical changes and biological responses. We found that representation, replication, and size and spacing recommendations integrated into the design phase were met in most cases. Furthermore, despite varying degrees of projected changes in temperature, dissolved oxygen, and aragonite saturation across the MPA network, suitable habitat for demersal fish species is projected to remain in the network despite some redistribution among sites. We also found that mid-depth MPAs are particularly important for persistence, as fish are projected to move deeper to avoid warming in shallower areas. Our results highlight that a representative MPA network with adequate replication, that incorporates areas of varying climate change trajectory, should buffer against the impacts of climate change.