ItemRadio- and Stable Carbon Isotope Analysis Reveals Minimal Assimilation of Petrogenic Carbon Into an Oligotrophic Freshwater Food Web After Experimental Spills of Diluted Bitumen(Elsevier, 2023-04-05) Graves, Stephanie; Mason, Johanna; Rodriguez-Gil, Jose Luis; Seguin, Jonathan Y.; Blais, Jules; Hanson, Mark; Hollebone, Bruce P.; Palace, Vince; Clark, Ian; Cundall, Leah; Layton-Matthews, Daniel; Leybourne, Matthew; Orihel, DianeFollowing an oil spill into water, bacteria can biodegrade petroleum hydrocarbons which could lead to petrogenic carbon assimilation by aquatic biota. We used changes in the isotope ratios of radio- (Δ14C) and stable (δ13C) carbon to examine the potential for assimilation of petrogenic carbon into a freshwater food web following experimental spills of diluted bitumen (dilbit) into a boreal lake in northwestern Ontario, Canada. Different volumes (1.5, 2.9, 5.5, 18, 42, 82, and 180 L) of Cold Lake Winter Blend (a heavy crude blend of bitumen and condensate) dilbit were applied to seven 10-m diameter littoral limnocorrals (approximate volume of 100 m3), and two additional limnocorrals had no added dilbit to serve as controls. Particulate organic matter (POM) and periphyton from oil-treated limnocorrals had lower δ13C (up to 3.2‰ and 2.1‰ for POM and periphyton, respectively) than the control at every sampled interval (3, 6 and 10 weeks for POM and 6, 8 and 10 weeks for periphyton). Dissolved organic and inorganic carbon (DOC and DIC, respectively) had lower Δ14C in the oil-treated limnocorrals relative to the control (up to 122‰ and 440‰ lower, respectively). Giant floater mussel (Pyganodon grandis) housed for 25 days in aquaria containing oil-contaminated water from the limnocorrals did not show significant changes in δ13C values of muscle tissue compared to mussels housed in control water. Overall, the changes in δ13C and Δ14C observed indicated small amounts (up to 11% in DIC) of oil carbon incorporation into the food web. The combined δ13C and Δ14C data provide evidence for minimal incorporation of dilbit into the food web of this oligotrophic lake, suggesting that microbial degradation and subsequent incorporation of oil C into the food web may play a relatively small role in the ultimate fate of oil in this type of ecosystem. ItemExperimental Iron Amendment Suppresses Toxic Cyanobacteria in a Hypereutrophic Lake(Wiley, 2016-02-25) Orihel, Diane; Schindler, David; Ballard, Nathaniel; Wilson, Lindsey; Vinebrooke, RolfThe effects of reducing nutrient inputs to lakes and reservoirs are often delayed by hysteresis resulting from internal phosphorus (P) loading from sediments. Consequently, controlling harmful algal blooms (HABs) in many eutrophic ecosystems requires additional management to improve water quality. We manipulated iron (Fe) concentrations in a hypereutrophic lake to determine if Fe amendment would suppress HABs by inhibiting P release from sediments. Our experiment consisted of 15 in situ mesocosms, 12 of which each received a different dose of Fe (ranging from 2 to 225 g/m2); the remaining three were unmanipulated to serve as controls. Iron amendment decreased P accumulation in porewaters and the flux of P from sediments, which significantly lowered P concentrations in the water column. Iron exerted significant dose-dependent negative effects on the biomass of phytoplankton and periphyton, and reduced the dominance of cyanobacteria. Even at the lowest doses, Fe appeared to reduce the toxicity of cyanobacterial blooms, as measured by concentrations of hepatotoxic microcystins. Overall, our findings highlight the potential for Fe treatment as an effective strategy for minimizing HABs in eutrophic lakes and reservoirs. More broadly, our study reinforces the importance of Fe in regulating the trophic state of freshwaters, and the sensitivity of certain ecosystems to changes in Fe supply. Finally, we hypothesize that decreases in natural Fe supplies to lakes associated with anthropogenic activities may worsen outbreaks of toxic cyanobacteria. ItemNaphthenic Acid Fraction Compounds Reduce the Reproductive Success of Wood Frogs (Rana Sylvatica) By Affecting Offspring Viability(Elsevier, 2022-10-18) Robinson, Chloe; Elvidge, Chris; Frank, Richard A.; Headley, John V.; Hewitt, L. Mark; Little, Alexander; Robinson, Stacey A; Trudeau, Vance; Vander Meulen, Ian; Orihel, DianeUnderstanding the toxicity of organic compounds in oil sands process-affected water (OSPW) is necessary to inform the development of environmental guidelines related to wastewater management in Canada's oil sands region. In the present study, we investigated the effects of naphthenic acid fraction compounds (NAFCs), one of the most toxic components of OSPW, on mating behaviour, fertility, and offspring viability in the wood frog (Rana sylvatica). Wild adult wood frogs were exposed separately from the opposite sex to 0, 5, or 10 mg/L of OSPW-derived NAFCs for 24 h and then combined in outdoor lake water mesocosms containing the same NAFC concentrations (n = 2 males and 1 female per mesocosm, n = 3 mesocosms per treatment). Mating events were recorded for 48 h and egg masses were measured to determine adult fertility. NAFC exposure had no significant effect on mating behaviour (probability of amplexus and oviposition, amplexus and oviposition latency, total duration of amplexus and number of amplectic events) or fertility (fertilization success and clutch size). Tadpoles (50 individuals per mesocosm at hatching, and 15 individuals per mesocosm from 42 d post-hatch) were reared in the same mesocosms under chronic NAFC exposure until metamorphic climax (61–85 d after hatching). Offspring exposed to 10 mg/L NAFCs during development were less likely to survive and complete metamorphosis, grew at a reduced rate, and displayed more frequent morphological abnormalities. These abnormalities included limb anomalies at metamorphosis, described for the first time after NAFC exposure. The results of this study suggest that NAFCs reduce wood frog reproductive success through declines in offspring viability and therefore raise the concern that exposure to NAFCs during reproduction and development may affect the recruitment of native amphibian populations in the oil sands region. ItemExperimental Evidence from the Field that Naturally Weathered Microplastics Accumulate Cyanobacterial Toxins in Eutrophic Lakes(Wiley, 2022-09-23) Hataley, Eden K.; Shahmohamadloo, Rene; Ortiz Almirall, Xavier; Harrison, Anna L.; Rochman, Chelsea M.; Zou, Shan; Orihel, DianeFreshwater ecosystems with recurring harmful algal blooms can also be polluted with plastics. As such, the two environmental problems may interact. To test if microplastics influence the partitioning of microcystins in freshwater lakes, we examined the sorption of four microcystin congeners to different polymers of commercially available plastics (low-density polyethylene, polyethylene terephthalate, polyvinyl chloride, and polypropylene). We conducted three experiments: a batch sorption experiment in the laboratory with pristine microplastics of four different polymers, a second batch sorption experiment in the laboratory to compare pristine and naturally weathered microplastics of a single polymer, and a 2-month sorption experiment in the field with three different polymers experiencing natural weathering in a eutrophic lake. This series of experiments led to a surprising result: microcystins sorbed poorly to all polymers tested under laboratory conditions (less than 0.01% of the initial amount added), irrespective of weathering, yet, in the field experiment, all polymers accumulated microcystins under ambient conditions in a eutrophic lake (range: 0-84.1 ng/g). Furthermore, the sorption capacity for microcystins differed among polymers in the laboratory experiment yet were largely the same in the field. We also found that the affinity for plastic varied among microcystin congeners, namely more polar congeners demonstrated a greater affinity for plastic than less polar ones. This study improves our understanding of the role of polymer and congener type in microplastic-microcystin sorption, and moreover, provides novel evidence from the field, showing that naturally weathered microplastics in freshwater lakes can accumulate microcystins. Consequently, we caution that microplastics may alter the persistence, transport, and bioavailability of microcystins in freshwaters, which could have implications for human and wildlife health. ItemTemporal Evolution of Critical Traits and their Relationship to Cod Stock Collapse and Recovery(Canadian Science Publishing, 2022-06-08) Petrie, Brian; Frank, Kenneth T; Leggett, William CThe North Atlantic Fisheries Organization response to a precipitous decline of the Flemish Cap cod (Gadus morhua) stock during the 1990s was the imposition of an 11-y moratorium on directed fishing for cod; recovery followed. Over the three decades that encompassed the pre-collapse, collapse and recovery stages, we found that the cod stock status was characterized by four traits: spawning stock biomass, maturity- and weight-at age, and recruitment. The temporal evolution of these traits was consistent with a density dependent conceptual model suggesting phenotypic plasticity was at play during the rebuilding of the stock. The temporal progression of the broader fish community paralleled that of cod, underlying its key ecosystem position. The same demographic variables defined the state of the adjacent Northern Cod stock which underwent a similar pattern of decline, an intermittent moratorium but only partial recovery. This partial recovery is possibly related, in part, to declines of prey species brought about by excessive harvesting after the cod collapse and an apparent collapse of capelin, a major dietary component.