Rolf D. Vinebrooke

Aquatic invasive species are among the greatest threats to freshwater biodiversity. Crayfish are especially robust freshwater invaders that can compete on various trophic levels simultaneously. The Northern Crayfish ( Faxonius virilis ) was introduced to the North Saskatchewan River basin circa 1990. Their impact on Alberta’s native fish communities remains unknown. We sampled 10 North Saskatchewan River basin tributaries for F. virilis and six common native fishes. We used stable isotope analysis to investigate if there exists resource partitioning and/or competition between F. virilis and native fishes and whether F. virilis sympatry is related to differences in isotopic metrics/body condition of native fishes. Overlap (0.14–31.2%) of F. virilis and native species basin-wide isotopic niches indicated that F. virilis can potentially consume the same dietary resources as secondary consumer fishes. However, segregation of realized isotopic niches indicated no actual consumption of the same resources. Similarity in isotopic metrics/body condition of allopatric and sympatric native fish populations indicated that F. virilis sympatry did not have detectable negative trophic effects on native fishes. Thus, F. virilis may be using dietary plasticity to exploit a different trophic niche than native fishes, ergo, avoiding interspecific competition through resource partitioning.

A mounting task in the aquatic sciences is to better monitor harmful algal blooms (HABs). In Canada, satellite Earth Observation is used to meet this challenge in a few large lakes (e.g., Lake Erie, Lake Winnipeg). Here, we highlight the novel ground truthing of an algorithm for multivariate analyses of HABs in a smaller Canadian prairie lake (Pigeon Lake, Alberta) using Sentinel 2 satellite-based data and confirmatory evidence from in situ concentrations of chlorophyll a and taxonomically diagnostic algal pigments. Calibration ( r² = 0.90, n = 73) and validation ( r² = 0.91, n = 86) of our model enabled testing for trends and discovery of within-lake sources of HABs using archival satellite imagery spanning a period of 6 years. Significant seasonality of the intensity, spatial extent, and severity of HABs in the study lake underscored our discovery of their origins near inflowing streams within the northwestern littoral zone. These findings highlight the potential of our remote-sensing approach to identify “hotspots” of HABs and help guide remediation strategies in small prairie lakes.

Catastrophic state changes often occur in ecosystems as consequences of shifts in the dominant life forms, such as in the case of sportfish introduction into naturally fishless mountain lakes. While the pronounced ecological displacement of native communities by these novel predators (i.e., weak resistance) is well documented, few studies have also examined the dynamics of their recovery rates (i.e., “engineering resilience”) following stressor removal. We addressed this knowledge gap by quantifying the taxonomic and species trait‐based ordination trajectories of crustacean zooplankton communities in stocked alpine lakes, which differed in how they were restored to a natural fishless state over a period of six decades. Resilience and resistance trajectories differed in each lake as the ecological importance of trait‐based species recolonization potential (e.g., asexual vs. sexual reproduction) replaced that of tolerance of size‐selective predation by fish (e.g., body size, pigmentation, motility). As a result, re‐establishment of large‐bodied zooplankton following the elimination of fish restored annual secondary production. In contrast, a more gradual unidirectional ordination trajectory toward smaller zooplankton body size and a decline in total zooplankton biomass occurred in a nearby alpine lake containing a protected native bull trout population. Although recovery trajectories returned via routes that differed from those of earlier resistance trajectories (i.e., hysteresis), we discovered that full taxonomic and functional recovery was realized in all the restored fishless lakes within three decades, regardless of the approach used to achieve ecosystem restoration.

Toxic cyanobacterial blooms (CBs) are becoming more frequent globally, posing a threat to freshwater ecosystems. While making long‐range forecasts is overly challenging, predicting imminent CBs is possible from precise monitoring data of the underlying covariates. It is, however, infeasibly costly to conduct precise monitoring on a large scale, leaving most lakes unmonitored or only partially monitored. The challenge is hence to build a predictive model that can use the incomplete, partially‐monitored data to make near‐future CB predictions. By using 30 years of monitoring data for 78 water bodies in Alberta, Canada, combined with data of watershed characteristics (including natural land cover and anthropogenic land use) and meteorological conditions, we train a Bayesian network that predicts future 2‐week CB with an area under the curve (AUC) of 0.83. The only monitoring data that the model needs to reach this level of accuracy are whether the cell count and Secchi depth are low, medium, or high, which can be estimated by advanced high‐resolution imaging technology or trained local citizens. The model is robust against missing values as in the absence of any single covariate, it performs with an AUC of at least 0.78. While taking a major step toward reduced‐cost, less data‐intensive CB forecasting, our results identify those key covariates that are worth the monitoring investment for highly accurate predictions.

Remote mountain lakes in protected areas are sentinels of the ecological impacts of extreme and novel environmental changes occurring at broad regional scales. Ecosystem responses to such stressors are often first detected as shifts in community composition. We surveyed phytoplankton communities across 82 mountain lakes to test the hypothesis that taxonomic composition is indicative of more environmental changes than are aggregate properties, such as total biomass. Phosphorus was the only significant predictor of chlorophyll-inferred algal biomass, a correlative finding supported by evidence from our nutrient amendment bioassays. Interlake variances in taxonomically diagnostic algal pigments and 78 genera were indicative of changes in total phosphorus, glacial coverage, underwater light availability, and dissolved organic carbon. Lack of concordance was observed between ordinations of pigment- and genus-based data as environmental variables captured more variance in the pigment data. Our findings provide a baseline for future lake monitoring programs in the Canadian Rockies as they increasingly experience interactive effects involving climate change and landscape features, such as variation in turbid glacial meltwaters and aeolian phosphorus deposition from wildfires.

Cumulative impacts of multiple extreme and novel environmental changes on communities are often the result of asynchronous rather than simultaneous exposures to such stressors. Yet, the importance of temporal dynamics remains a major knowledge gap in multiple stressor ecology, lacking theory or evidence. We provide a conceptual template for predicting the ecological importance of the order in which consecutive stressors occur (i.e. an exposure order effect) based on correlated species responses. Negative correlation of species responses is hypothesized to increase, while positive correlation is expected to reduce, exposure order effects of consecutive stressors on communities. Towards a proof of concept, we experimentally exposed planktonic communities from fishless mountain lakes to different temporal sequences of two stressors, namely invasive sportfish and elevated water temperatures. Both stressors suppressed the same resident top predator and large grazers while eliciting positive responses from smaller tolerant taxa, attesting to their interchangeable effects across species based on size selection. As a result, reversal of the order of exposure to the two stressors did not alter their combined effects on community composition and function. Our findings highlight how the order in which consecutive stressors occur may not matter to a community if ecological memory of either stressor induces tolerance of the other.

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change.