Nitellopsis obtusa (starry stonewort) is a macroalga in the Characeae family first documented in North America c. 1974. Since initial introduction, N. obtusa clonal populations quickly established in inland lakes as early as 2005. Despite increased N. obtusa monitoring over the last decade, only sterile or male specimens were documented in North America, however; during routine monitoring in Lake Simcoe and Lake Scugog in 2022, we discovered the presence of female gametangia on N. obtusa. In addition, two other Characeae genera had prevalent antheridia and oogonia, co-occurring with oogonia-presenting N. obtusa, which had not been observed previously despite intensive monitoring since 2008. Further studies in North America are required to confirm the proportion of female populations present within invaded regions, as well as to identify plausible causes shifting gametangia development across non-native and native Characeae, especially within the context of climate change. The presence of oogonia on N. obtusa represents a major change to our understanding of this species and its reproductive ecology in North America.
Although the negative impacts of roads on herpetiles are well documented, broad‐scale implementation of effective mitigation measures to address these impacts remains limited. Here, we evaluated whether a novel, cost‐effective, retrofit ecopassage design can reduce road mortality of herpetiles in the Lake Simcoe Watershed, using a before‐after‐control‐impact study. We also examined whether the ecopassages impacted the movement of turtles across the landscape using wildlife cameras. Our study indicated that the ecopassages significantly reduced turtle road mortality at the treatment sites but were not effective at mitigating road mortality of other herpetiles. Most turtle road‐kill at the ecopassages sites occurred at fence ends, highlighting the need for solutions to address fence‐end effects for herpetiles. There was no evidence that the ecopassages reduced turtles' ability to move between habitats as individuals were observed crossing through the ecopassages. Our results suggest that inexpensive solutions can effectively mitigate road mortality for turtles and taller fencing could improve the design for other species. Ecopassages, such as the ones tested in this study, should be widely implemented in road‐kill hotspots across all regions, especially in habitats of rare or at‐risk species, in order to protect turtles and other wildlife from the increasing threat of roads. Cost‐effective retrofit ecopassages reduce road mortality of turtles, but not other herpetiles, without impacting movement between habitats.
To date, environmental flow strategies have predominantly been used in cases where a lack of available water has degraded the ecological quality and natural functioning of a river system. In this study, we used environmental flows on an urbanized watershed where flow volumes and flow rates have increased, and large (e.g. 100-year) event return periods become more frequent (~10 years). Using an environmental flows strategy to model the amount of hydrological alteration, we assessed whether urban development and land cover changes have impacted the flow regime and the ecological health of this watershed. We reconstructed the flow regime at Lovers Creek (Barrie, Ontario, Canada) using three scenarios of urban development: a pre-settlement reference condition with 100% natural cover, mid-development with 6% urban cover, and the current condition with 21% urban cover. We found that, in contrast to many other studies, increased urban cover has coincided with increased baseflow volumes, as well as increased volumes in other components of the flow regime. Of particular concern were the increased flow rate and volume of large events such as channel forming and riparian flows; an increased rate of change in event hydrographs, and a much shorter return period of large event storms (e.g. a 100-year event under reference conditions, is now a 10-year event in the current urbanized condition). In this watershed, restoration of flow to the reference condition is not practical; however, using improved stormwater management such as low-impact development technologies and green infrastructure may offset some of the alteration to the flow regime and mitigate future further alterations due to increased urbanization. As Lovers Creek has been identified as a critical coldwater stream habitat with brook trout, the results of this study are being used to assess changes in the ecological health due to increased urban cover, and to develop management strategies that assist in restoring a more natural flow regime in order to better protect both natural habitats and human infrastructure that are vulnerable to flooding caused by more frequent, increased volume flow events.
Ginn BK, Dias EFS, Fleischaker T. 2021. Trends in submersed aquatic plant communities in a large, inland lake: impacts of an invasion by starry stonewort (Nitellopsis obtusa). Lake Reserv Manage. XX:XXX–XX. Aquatic plant and macroalgae (collectively, macrophyte) communities from Lake Simcoe (Ontario, Canada) were studied in lakewide, >200 site surveys in 2008, 2013, and 2018. Over this period, mean macrophyte biomass increased 5-fold, from 29.9 g (dry)/m² in 2008 to 153.9 g (dry)/m² in 2018, due to the arrival and expansion of invasive starry stonewort (Nitellopsis obtusa). First recorded in Lake Simcoe in 2009, starry stonewort has greatly altered the macrophyte community, particularly in shallow (<3 m) water where it outcompeted invasive Eurasian watermilfoil (Myriophyllum spicatum). By 2018, starry stonewort comprised 67.6% of the total macrophyte biomass in Lake Simcoe. In shallow, mesotrophic Cook’s Bay, comparison to studies from the 1980s shows an increased plant biomass due to increased water clarity, from phosphorus (P) abatement and invasive dreissenid mussels, with further increases after 2011 due to starry stonewort. Starry stonewort may continue to impact nearshore ecology, with shallow-water fish species losing habitat and refugia as the “forest-like” structure of the plant community is replaced by large, dense aggregations of starry stonewort. Recreational uses will also be impaired and landowner complaints of macrophyte wash-ups will increase, with municipalities and lake-based businesses bearing the cost of mitigation and control strategies. Future research should consider the impacts of starry stonewort to P cycling as, unlike aquatic plants that uptake sediment P, macroalgae use dissolved P as a nutrient source. A lack of communication and reporting on starry stonewort has enabled its spread through south-central Ontario and the Great Lakes Region. Moving forward, we need a better understanding of starry stonewort biology and need to develop effective control and management strategies.
Chloride (Cl‐) in urban waterways largely originates from runoff containing deicing salts. Cl‐ is retained in watersheds after deicing ends, resulting in deleterious effects on aquatic biota. Stormwater management ponds (SWMPs), designed to mitigate ‘flashy’ urban runoff response, are known to impact pollutant transport. However, there is little information on what role SWMPs play in the timing and magnitude of Cl‐ transport over different timescales. This study quantifies the mass of Cl‐ retained in two SWMPs over varying timescales. Both ponds are in an urbanizing watershed in south‐central Ontario; one drains a commercial area, the other, a residential area. High frequency measurements of water level and specific conductivity, from which flow and Cl‐ concentration were derived, were taken with sensors at pond inlets and outlets. For one SWMP, data were also collected upstream and downstream of the confluence of the pond outflow and the receiving creek to quantify the in‐stream response to Cl‐‐laden pond outflows. The findings suggest that SWMPs likely play a role in watershed‐scale Cl‐ retention; one SWMP consistently retained Cl‐ while the other had variable retention and release of Cl‐. In the receiving creek, Cl‐ concentrations downstream of the pond exceeded the acute toxicity threshold for aquatic organisms twice as often as concentrations upstream of the pond, and Cl‐ pulses corresponded to Cl‐ release events from the pond. The results of this study suggest that SWMPs concentrate spatially distributed salt inputs and modify the timing and magnitude of their release to receiving streams. Stream reaches that receive water inputs from SWMPs may be more vulnerable to Cl‐ toxicity than reaches that do not receive flow via SWMPs. The results of this study will help parameterize the role of SWMPs in watershed‐scale Cl‐ transport models and geospatial models of salt vulnerable areas. This article is protected by copyright. All rights reserved.
To determine whether invasive round goby (Neogobius melanostomus) from Lake Ontario were establishing a year‐round population in a tributary stream or migrating to the lake, we assessed population and individual movement patterns using mark–recapture assessment generated from weekly backpack electrofishing from May until November 2016. Round goby abundance was low in spring, peaked in summer and decreased again in autumn, suggesting seasonal inward stream migration and outward migration back to the lake. Adult round goby movement patterns were positively associated with changes in water temperature, but this was not the case for juveniles. Juveniles displayed a preference for shallow, upstream habitats. Observations of reproductive individuals coupled with a peak in juvenile abundance following the peak in adult abundance indicate that the tributary was used for reproduction and recruitment. The individual movement was primarily upstream in spring, and there was little net movement in summer, likely during reproduction. Downstream movement occurred in autumn over a short time period, suggesting rapid outmigration to the lake. The combined observations of seasonal population structure and individual movement suggest that tributary streams connected to large, infested waterbodies can be used for round goby reproduction and recruitment, rather than year‐round residence. This study provides evidence of round goby seasonal migration and their individual movement patterns within tributary streams, which complements an earlier study in Lake Erie tributaries and may be a common occurrence in other Great Lakes tributaries.
Hilsenhoff’s family-level index (FBI) combines information about the relative abundances of taxa and their tolerances to pollution. Versions of this index are used extensively in North America to assess water quality. When faced with constraints on time, money, or expertise, bioassessment practitioners have been tempted to calculate a version of the FBI with very coarse (e.g., order-level) taxonomy. Such an approach requires a degree of within-taxon averaging of tolerance values and raises questions about the degree to which accuracy is compromised and bias is introduced. Data from thousands of streams in Ontario (Canada) demonstrated that such tolerance-value averaging produces index scores and associated water-quality classifications that are not equivalent to those calculated with the standard family-level taxonomic precision. Two methods were used in an attempt to correct the order-level FBI scores to equivalence with the family-level index: (1) tolerance scores for the orders included in the calculation were calculated as abundance-weighted means of the scores of their component families, and (2) order-level FBI scores were estimated as predicted values from a polynomial regression of the two versions of the index. The use of abundance-weighted mean tolerance scores greatly improved the accuracy of the order-level index, and the regression-based correction reduced bias by equalizing the distribution of errors across the range of observed FBI values. Nonetheless, equivalence of scores was not demonstrated, and water quality was misclassified in 12 to 80% of cases. Practitioners are discouraged from the practice of tolerance-value averaging and are advised to adhere to the standard family-level FBI.
Water agencies from 7 of the 10 Canadian provinces shared their experiences regarding history, successes, challenges and lessons learned with integrated watershed management. Based on these contributions, it is clear that an integrated approach does not mean ‘all-encompassing’. Rather, it proposes desirable and feasible solutions through a systems approach based on sound technical information (e.g. biophysical and socio-economic), public engagement and monitoring. The roles of all participants must be clearly defined in order to promote success and facilitate implementation. Enduring and emerging challenges, such as adequate capacity and financing, engagement with Aboriginal communities and other stakeholders, and successful implementation, are identified.
The Grand River watershed is the largest in southern Ontario. Poor water quality, floods and drought experienced in the 1930s prompted the formation of the Grand River Conservation Authority. While significant water improvements have been achieved, the Grand River faces chronic stress from the impacts of rapid population growth, land use intensification and changing climate. There is renewed commitment to address evolving water issues through integrated watershed management. This article summarizes the lessons learnt in the Grand River watershed and contends that integrated watershed management, although difficult to implement, provides a useful framework for practical application and positive results.
Moos MT, Ginn BK. 2016. Developing a lake management strategy by dovetailing lake monitoring with paleolimnological techniques: a case study from a kettle lake on the Oak Ridges Moraine (Ontario, Canada). Lake Reserv Manage. 32: 234–245. In response to concerns about declining water quality, increased aquatic plant biomass, and harmful algal blooms, a lake monitoring program was undertaken on a suburban kettle lake near Toronto, Canada. We identified environmental conditions consistent with eutrophication, and the largest source of phosphorus (P) loading was from sediment release during an extended period of low dissolved oxygen during thermal stratification of the water column. To put these current environmental conditions in perspective, account for long-term limnological trends, and develop a sustainable lake management strategy, we also undertook paleolimnological analysis of a sediment core. Using diatoms as proxy indicators, historic limnological conditions were reconstructed. Although pre-European settlement conditions were typical of lakes with forested catchments in this region, the lake was mesotrophic (total phosphorus [TP] ∼17.5 µg/L), likely from P bound to dissolved organic carbon. P concentrations increased with the use of chemical fertilizers and establishment of seasonal lakeside cottages and resorts starting in the 1920s (the beginning of the diatom-inferred (DI-) TP upward trend). With the conversion of these cottages into year-round homes (since 1960) and further urbanization of the catchment, including servicing with municipal water supply but continued reliance on septic tanks, P has increased further (TP ∼26.1 µg/L). For restoration to a sustainable state, methods of preventing sediment P release (capping the sediment surface or oxygenation of the hypolimnion) should be considered, along with installation of municipal wasterwater servicing and stewardship projects to prevent further P loading from septic systems and surface runoff.
The Lake Simcoe Watershed (LSW) is an important natural resource, supporting varied agricultural, recreational, and tourism activities for millions of people. Historically, major alterations to land uses have occurred throughout the watershed, resulting in increases of nutrients and contaminants, and alteration of hydrological and thermal regimes. The combination of these stressors has the potential to elicit greater impacts on ecosystem health than any one stressor in isolation, yet no studies have examined their effects on stream health and aquatic biota in the LSW. In this study, we quantified the impacts of multiple stressors on indices of biotic integrity, as well as assessments of benthic invertebrate and fish community composition from 2004 to 2012. Using a suite of multivariate analyses, we examined stressors across three categories of environmental variables: water quality, temperature, and hydrology. Water quality explained the largest amount of variation in stream health and biological community composition, followed by water temperature and hydrological variables, respectively. Total phosphorus, dissolved oxygen, and iron concentrations, as well as the 7-day low flow and the mean summer temperature, were identified as predictors of both fish and benthic invertebrate variance. Multiple stressor interactions were detected for fish communities, although these interactions were of lower relative importance than for individual stressors. In contrast, no significant stressor interactions were found to influence benthic invertebrate communities. Overall, our results reinforce the importance of ecosystem monitoring, and the need to consider the influence of multiple aspects of ecosystem function, when examining the health of aquatic systems.
A methodology has been developed to delineate recharge areas that support groundwater-dependent ecological features such as wetlands and coldwater streams. Numerical groundwater models are employed together with particle tracking techniques to link recharge areas to specific ecological features. Kernel density estimation methods are used to identify areas that contain the maximum number of particle endpoints per unit area. These high-density endpoint clusters are subsequently mapped as ecologically significant groundwater recharge areas (ESGRAs). The technique can be utilized with either finite-element or finite-difference groundwater models which are loosely coupled or fully integrated with a distributed hydrologic model. A good representation of both the surface water and the shallow groundwater system is required and the models should be based on a rigorous understanding of the regional, watershed and local-scale geologic, hydrogeologic and hydrologic setting. This manuscript describes how the methodology was employed to delineate ESGRAs for the Oro North, Oro South and Hawkestone Creeks subwatersheds, located in the northwest portion of the Lake Simcoe watershed in southern Ontario, Canada. The three study subwatersheds are connected to the Oro Moraine complex, a high-recharge feature that supports multiple watersheds and the regional groundwater flow system. A transient, integrated surface water/groundwater model was developed for the watersheds flanking the moraine and was calibrated to daily streamflow and groundwater-level observations. Particle tracking was then used to define the groundwater flow system between all streams and wetlands and the areas of recharge, and provided insight into the hydrologic function of the Oro Moraine. After optimization of the cluster analysis procedure, 24% of the 125-km² study area was mapped as having recharge areas that support significant ecological features. As required by the Lake Simcoe Protection Plan, the ESGRAs will be protected from future development to ensure the maintenance of the groundwater-fed ecosystems they support. The methodology described in this paper provides a consistent, objective and technically sound means of identifying and delineating ESGRAs, and has recently been applied to other watersheds in southern Ontario.
To determine pre-disturbance limnological conditions, evaluate the impact of environmental stressors (surface water acidification, nutrient inputs, climate change, and winter deicing salt), and set realistic recovery targets for lake management strategies, a rapid assessment paleolimnological approach was used to determine the amount (and likely causes) of environmental changes over the past ∼100-150 years in 51 urban lakes from Halifax, Nova Scotia (Canada). Diatom assemblages from lake sediment cores were used with “top” (recently deposited, surface) samples being matched to measured limnological conditions, and “bottom” (generally from >15 cm deep) samples used to infer pre-disturbance limnological conditions such as pH, total phosphorus (TP), specific conductance, and shifts due to changing climatic conditions. Environmental change was assessed by calculating the metric of change in species composition between present-day and pre-disturbance diatom assemblages, and inferences from quantitative estimates of diatom-inferred pH, specific conductance, and TP. All 51 study lakes have experienced floristic changes in diatom species composition since pre-disturbance times, but different environmental stressors were implicated: 8 of the 51 lakes underwent significant (i.e., >2 times the root mean-squared error [2X RMSE] of the inference model) decreases in diatom-inferred pH; 8 lakes had significant increases in diatom-inferred TP; and 19 otherwise relatively pristine lakes had increases in planktonic taxa consistent with observations linked to changes in lake seasonality and limnological changes most closely linked to climate warming in Nova Scotia and other regions. The remaining 16 lakes did not have large and consistent changes in diatom flora or changes in diatom-inferred TP or pH >2X RMSE of the prediction of the models. Lake-specific factors were related to these inferences, and the lakes that acidified were mainly the currently most acidic sites, whereas those that experienced issues related to eutrophication were generally among the most alkaline sites. Of our 51 lakes, 22 (including some experiencing pH, TP, or showing floristic changes linked to climate changes) had increases in measured conductivity (1980-2002) and, correspondingly, increased relative abundances of halophilic diatom taxa. These lakes, often with catchments containing high surface areas of impervious surfaces, are examples of a trend of increasing salinity in northeastern North American lakes likely related to winter application of deicing (road) salt. The application of this paleolimnological approach enabled us to identify which lakes have undergone significant changes in diatom assemblages, as well as which environmental stressor(s) were most probable. This information can help lake managers develop more targeted and effective management strategies.
This study examined the effect of invasive dreissenid mussels on nutrient and carbon dynamics in a large lake (Lake Simcoe, Ontario). We measured rates of nutrient (phosphorus and nitrogen) and carbon excretion and biodeposition by zebra and quagga mussels and the P, N and C content of their soft tissues and shells at different depths throughout the open-water season. Measurements were combined with detailed information about dreissenid biomass and lakewide distribution to examine the impacts of dreissenids on whole-lake dynamics of P, N and C.Mussel tissue P, N and C content and rates of excretion and biodepositon varied among species, seasons and depths, apparently driven by metabolic and stoichiometric factors.Dreissenid mussels excreted, deposited and stored large quantities of P, N and C when compared to lake standing stocks and loadings, and represent an important driver of nutrient cycling in the lake. Living and discarded mussel shell material is shown to represent a potentially important, and hitherto largely overlooked, long-term sink for P, N and C.The concentration of dreissenid biomass in the well-mixed and illuminated littoral portion of L. Simcoe results in redirection of nutrients and carbon from offshore areas to the nearshore zone of the lake.Changes in nutrient and carbon distribution and cycling patterns caused by dreissenid establishment in L. Simcoe and other ecosystems can have implications for the distribution of primary and secondary production and should be considered in the context of water quality and nutrient input management.
Recreational disturbance associated with trails has been identified as one of the major factors causing a decline of native biodiversity within protected areas. However, despite the negative impacts that recreation can have on biodiversity, providing public access to nature is critical for the future of the conservation of biodiversity. As such, many protected area managers are looking for tools to help maintain a balance between public access and biodiversity conservation. The objectives of this study were to examine the impacts of recreational trails on forest-dwelling bird communities in eastern North America, identify functional guilds which are particularly sensitive to recreational trails, and derive guidelines for trail design to assist in managing the impacts of recreational trails on forest-dwelling birds. Trails within 24 publicly owned natural areas were mapped, and breeding bird communities were described with the use of point count surveys. The density of forest birds, particularly of those species which nest or forage on the ground, were significantly positively influenced by the amount of trail-free refuge habitat. Although management options to control trail use in non-staffed protected areas are limited, this study suggests that protected area managers could design and maintain a trail network that would minimize impacts on resident wildlife, while providing recreational opportunities for visitors, by designing their trail network to maximize the area of trail-free habitat.
Innovative management strategies for nutrient enrichment of freshwater are important in the face of this increasing global problem, however many strategies are not assessed over long enough time periods to establish effectiveness. Paleolimnological techniques using diatoms as biological indicators were utilized to establish ecological reference conditions, environmental variation, and the effectiveness of lanthanum-saturated bentonite clay (brand name: Phoslock(®)) applied to reduce water column phosphorus (P) concentrations in four waterbodies in Ontario, Canada, and eastern Australia. In sediment cores from the two Canadian sites, there were short-lived changes to diatom assemblages, relative to inferred background conditions, and a temporary reduction in both measured and diatom-inferred total phosphorus (TP) before returning to pre-application conditions (particularly in the urban stormwater management pond which has a high flushing rate and responds rapidly to precipitation and surface run-off). The two Australian sites (a sewage treatment pond and a shallow recreational lake), recorded no reduction in diatom-inferred TP. Based on our pre-application environmental reconstruction, changes to the diatom assemblages and diatom-inferred TP appeared to be driven by larger, climatic factors. While laboratory tests involving this product showed sharp reductions in water column TP, management strategies require detailed information on pre-application environmental conditions and variations in order to accurately assess the effectiveness of new technologies for lake management.
The extraction of bitumen from the Athabasca oil sands is rapidly expanding, and emission of sulphur and nitrogen oxides has substantially increased. To determine whether lakes downwind of this development in northwest Saskatchewan have been detrimentally impacted since development of the oil sands, a paleolimnological assessment of ten lakes was carried out. Analysis of diatom valves and inferences of diatom-inferred pH indicated that emissions have not resulted in widespread chronic acidification of acid-sensitive lakes ~80–250 km east and northeast of the oil sands development around Fort McMurray and Fort Mackay. However, one of the closest sites to the development indicated a slight decline in diatom-inferred pH, but the two next closest sites, both of which had higher alkalinity, did not show any evidence of acidification. There were also no consistent trends in the concentration or flux of total or individual priority pollutants including lead, mercury, copper, zinc and vanadium. The sedimentation rates in most lakes increased since the mid-1900s, along with increased flux of both diatoms and scaled chrysophytes. Subtle changes in the species assemblages of diatoms and increased flux of diatoms and chrysophyte scales are consistent with recent climate change in this region.
Hypoxia and cyanobacterial blooms were extensive in Lake Simcoe during the 1980s and are still a problem to a lesser degree despite extensive nutrient load reduction from the catchment basin. The continuing signs of productivity indicate a potential internal phosphorus (P) source. Internal P load, as a redox-dependent release from bottom sediments, is hard to determine in a large, relatively shallow and partially unstratified lake such as Lake Simcoe. Of the lake's three major basins, only Kempenfelt Bay stratifies long enough to develop hypoxia in the stagnant summer hypolimnion. The following indications of sediment P release are available from historic data: 1) hypolimnetic hypoxia still occurs in Kempenfelt Bay although the hypoxic factor (number of days that an area equal to the bay's surface area is overlain by water of <= 2 mg/L dissolved oxygen, DO) has decreased substantially and significantly from 15.8 d/yr (1980-1994) to 4.0 d/yr (1995-2011); 2) hypoxic factors for other lake sections and at different DO levels also indicate widespread hypoxia; 3) concentrations of redox dependent metals, Fe and Mn, increase with depth; and 4) euphotic zone P and chlorophyll concentrations increase and water clarity decreases during fall turnover. Cyanobacterial blooms appear to occur in response to internal load as supported by occasional cyanobacteria counts. These indicators provide evidence that internal loading is likely occurring and affecting the water quality in Lake Simcoe. We expect that further monitoring, specific for internal load, will corroborate these results.
We report results from a spatially intensive monitoring and modelling study to assess phosphorus (P) dynamics in the Beaver River, a tributary of Lake Simcoe, Ontario. We established multiple monitoring stations (9 flow and 24 water quality stations) from headwaters to near the outflow that were operated for 2 field seasons, complementing longer term data from a flow monitoring site and water chemistry monitoring site. We applied the Branched-INCA-P model, which allows fully distributed simulations supported by highly distributed monitoring data. Using spatially distributed data helped better understand variable P and sediment dynamics across the catchment and identify key model uncertainties and uncertainties related to catchment P management. Measured and modelled total P concentrations often exceeded provisional water quality thresholds in many areas of the catchment and highlight the value of studying water quality across multiple subcatchments rather than at a single site. Total P export coefficients differed widely among subcatchments, ranging from 2.1–21.4 kg km-2 y-1 over a single year. Export coefficients were most strongly (negatively) related to the proportion of wetland cover in subcatchments. The INCA-P model captured spatial variation in P concentrations relatively well, but short-term temporal variability in the observed data was not well simulated across sites, in part due to unmodelled hydrological phenomena including beaver activity and unknown drivers of P peaks that were not associated with hydrological events.
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