Broad screening of toxic and bioactive metabolites in cyanobacterial and harmful algal blooms in Lake of the Woods (Canada and USA), 2016–2019

Cyanobacteria produce toxic/bioactive metabolites that affect human and ecosystem health via inhibition of proteases, carboxypeptidases, or phosphatases. From surface water samples collected between 2016 and 2019 inclusive (n = 78), we report intracellular concentrations of more than 30 such compounds in Lake of the Woods (LOW), a large lake system of multinational importance. Although most surface biomass blooms were dominated by the cyanobacteria Dolichospermum (max. ～50 mg/L) and Aphanizomenon (max. ～60 mg/L), there was also significant biomass of other cyanobacteria (Gloeotrichia echinulate along shoreline, max. ～40,000 mg/L; Woronichinia naegeliana max. ～100 mg/L; Lyngbya max. ～10 mg/L; Planktothrix agardhii max. ～6 mg/L) and phytoplankton (Stephanodiscus niagarae max. ～6 mg/L). Microcystins (MCs) were present in ～80 % of samples, peaking at ～33 µg/L (MC variant-LR). Approximately 50 % of samples contained MC concentrations below 0.1 µg/L. Alkaloid metabolites detected included neurotoxin anatoxin-a (～60 % < 0.1 µg/L) and cytotoxic cylindrospermopsins (～30 % < 0.1 µg/L). Anabaenopeptins A/B/F were prevalent (>96 %) and exceeded MCs by >100 fold (max. >4,000 µg/L). Aeruginosamide B was present in ～75 % of samples (max. ～10 µg/L). Cyanopeptolin 1040 MB, microginin 690 methyl ester, and oscillaginin A were not detected however, traces of micropeptin 1106 were detected. Microcystin and anabaenopeptin genes were also detected in the majority of samples (78 % and 79 %, respectively), while saxitoxin, cylindrospermopsin, and anatoxin genes occurred at lower frequencies with 59 %, 36 %, and 38 % detection, respectively. These results will aid assessment of risk from cyanobacterial blooms in LOW and inform ongoing binational lake management and policy development.     

The Dune Lakes in central coastal California: Why are they dry?

The Dune Lakes comprise 10 natural lakes in the Callender Dunes in central coastal California, USA. These lakes are wetlands in an arid environment, being important habitat for native wildlife and plants, including three occurrences of the federally endangered/State threatened wetland plant, La Graciosa thistle (Cirsium scariosum var. loncholepis; Asteraceae). This plant is known from 21 occurrences, of which only five are extant in 2019. One extant occurrence persists at the lakes and where two other occurrences are likely extirpated. Nine lakes have recently dried, one having been dry for 5 years (2012–2017). Understanding the hydrology of the Dune Lakes is essential for conservation planning and to help prevent extinction of La Graciosa thistle. The best available information points to a combination of two primary causes for drying of the lakes. The first is extensive groundwater extraction beneath Nipomo Mesa to the east. The second is severe drought. The competing demands for water and continued development on the mesa will be obstacles to restoration of the lakes and to recovery of the endangered plant.     

Erratum to: Flood Forecasting and Decision Making in the new Millennium. Where are We?

Water Resources Management -     

The choice of substation electric connection circuits: a unified or an individual approach?<Superscript>1</Superscript>

Typical substation electric connection circuits, used at the present time, are analyzed. Some versions of the use of substation distributor circuits for controlling electric network modes of operation are considered. Data on the downtimes of gas-filled circuit breakers and on the extent to which bus bypass systems are employed are analyzed. Recommendations for choosing different versions of substation electric connection circuits are formulated.     

Landscape-scale modeling of water quality in Lake Superior and Lake Michigan watersheds: How useful are forest-based indicators?

The Great Lakes watersheds have an important influence on the water quality of the nearshore environment, therefore, watershed characteristics can be used to predict what will be observed in the streams. We used novel landscape information describing the forest cover change, along with forest census data and established land cover data to predict total phosphorus and turbidity in Great Lakes streams. In Lake Superior, we modeled increased phosphorus as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, and agricultural land, and we modeled increased turbidity as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, agricultural land, and urban land. In Lake Michigan, we modeled increased phosphorus as a function of ecoregion, decrease in the proportion of forest disturbed during 1984–1999 and watershed storage, and increase in the proportion of urban land, and we modeled increased turbidity as a function of ecoregion, increase in the proportion of forest disturbed during 2000–2009, and decrease in the proportion softwood forest. We used these relationships to identify priority areas for restoration in the Lake Superior basin in the southwestern watersheds, and in west central and southwest watersheds of the Lake Michigan basin. We then used the models to estimate water quality in watersheds without observed instream data to prioritize those areas for management. Prioritizing watersheds will aid effective management of the Great Lakes watershed and result in efficient use of restoration funds, which will lead to improved nearshore water quality.     

Ecosystem modelling of data-limited fisheries: How reliable are Ecopath with Ecosim models without historical time series fitting?

Long-term time series data are not available for many of the African Great Lakes. This precludes fitting ecosystem model parameters to time series data, and we do not know how reliable non-fitted models are compared to fitted ones in terms of predicting consequences of alternative management strategies. To investigate this, we generate a historical Ecopath with Ecosim (EwE) model for Lake Victoria (East Africa), fitted to time series data (1980–2015), and a present-day EwE model (representing average conditions for the period 2010–2015). We do scenario simulations using the present-day model and the comparable 2015 end-state of the historical model, and test if incorporating information on short-term biomass trends by adjusting biomass accumulation (BA) parameter in the present-day model increases its reliability. We find that there are differences in model predictions, but those differences can be lessened by adjusting BA terms in the present-day model to reflect biomass trends from short-term empirical data. We also compare the models with and without fitted vulnerability parameters. The models generally give comparable results for the dominant commercial fisheries at low fishing pressure; when fishing mortality is increased, the models give variable predictions. This study adds to the current understanding of the limitations of EwE models that are not challenged to reproduce long-term historical fishery responses to perturbations. We conclude that for the less productive groups, as well as groups that suffer heavy mortality (either due to predation or fisheries), it may be appropriate to use negative BA as first draft assumption in present-day models.     

REGIONAL FRAMEWORKS APPLIED TO HYDROLOGY: CAN LANDSCAPE‐BASED FRAMEWORKS CAPTURE THE HYDROLOGIC VARIABILITY?

Regional frameworks have been used extensively in recent years to aid in broad‐scale management. Widely used landscape‐based regional frameworks, such as hydrologic landscape regions (HLRs) and physiographic provinces, may provide predictive tools of hydrologic variability. However, hydrologic‐based regional frameworks, created using only streamflow data, are also available and have been created at various scales; thus, relating frameworks that share a common purpose can be informative. In addition, identifying how the relative importance of variables change in governing streamflow with respect to scale can also be informative. The purpose of this study was to determine whether landscape‐based frameworks could explain variation in streamflow classifications and in the hydrologic variables used in their creation. We also evaluated how climate and watershed‐based variables govern the divergence of different flow classifications at two different scales. HLRs and physiographic provinces poorly predicted flow class affiliation within our study and for the entire USA, although physiographic provinces explained more variability. We also found that HLRs explained very little variation in individual hydrologic parameters. Using variables summarized at the watershed scale, we found that climate will play a larger role in influencing hydrology across the entire US, whereas soils may govern variation in hydrology at smaller scales. Our results suggest that predictor variables, developed at the watershed scale, may be the most appropriate at explaining hydrology and that the variables used in creating regional landscape‐based frameworks may be more useful than the frameworks themselves. In addition, managers should be careful when using landscape‐based regional classifications for stream management because the scale of their construction may be too broad to capture differences in flow variability. Copyright © 2011 John Wiley & Sons, Ltd.     

Drying Urban lakes: A consequence of climate change,urbanization or other anthropogenic causes? An insight from northern India

Urban lakes in many places around the world are rapidly becoming vulnerable because of such factors as urbanization, climate change, anthropogenic pollutant inputs, etc. The influence of such forcing factors on lakes hydrology must be correctly recognized and addressed in order to protect them over the long term. Facing similar challenges, Sukhna Lake, an urban lake in northern India, has apparently dried up frequently in the recent past. Numerous hypotheses were subsequently proposed to isolate the possible factors affecting the lake and its water budget, including the potential impacts of land use changes, climate change, anthropogenic activities and other natural processes. Using meteorological data, lake‐catchment information and a hydrologic model, these hypotheses were comprehensively analysed. Relevant data on rainfall, wind, temperature, lake inflows, groundwater, lake physical characteristics, catchment land uses, soil texture, etc., were gathered for the analysis. A temporal trend analysis of factors relevant to these hypotheses was undertaken to identify critical drivers of hydrological changes. A sensitivity analysis also was performed, using the lake water budget, to determine and prioritize the predominant factors affecting the lake, leading to the creation of an annual lake water budget for the period from 1971 to 2013, highlighting the lake inflows and outflows. The lake annual inflow (catchment run‐off) was computed by adopting a rainfall–run‐off model based on the SCS‐curve number. Lacking any anthropogenic water withdrawals, the outflow was quantified by estimating the evaporation loss (using the FAO‐based Penman–Monteith Equation). The results of the present study  indicate that the process of siltation and the construction of check dams in the catchment, rather than urbanization and climate change, were the dominating reasons contributing to changes in the lake hydrology, and affecting the lake most in recent years.     

Post‐Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat Spawning?

Repeat salmonid spawners may make large contributions to total recruitment and long term population stability. Despite their potential importance, relatively little is known about this phase of the life history for anadromous populations, and nothing has been reported for landlocked populations. Here, we studied post‐spawning behaviour and survival of landlocked Atlantic salmon in relation to downstream dam passage in the River Klarälven, Sweden. Eight hydropower stations separate the feeding grounds in Lake Vänern from the spawning grounds in the River Klarälven, and no measures to facilitate downstream migration are present in the river. Forty‐nine percent of the salmon survived spawning and initiated downstream migration. Females and small fish had higher post‐spawning survival than males and large fish. The post‐spawners migrated downstream in autumn and spring and remained relatively inactive in the river during winter. Downstream migration speed in the free flowing part of the river was highly variable with a median of 9.30 km/day. Most fish passed the first hydropower station via upward‐opening spill gates after a median residence time in the forebay of 25 min. However, no tagged fish survived passage of all eight hydropower stations to reach Lake Vänern. This result underscores the need for remedial measures to increase the survival of downstream migrating kelts. Copyright © 2015 John Wiley & Sons, Ltd.