Empirical Research

We have long been interested in the intersection of energetics, behavior and food webs. These aspects come together to govern the structure of food webs in time and space. Below, I highlight a few areas of empirical research that behavior, bioenergetics and food web structure under global change.

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1) Fish behavior in Time and Space (telemetry)
Recently, we have been involved in a NSERC Alliance in Alqonquin park with a great group of scientists. Here, 3 lakes (Canoe, Tea and Smoke) have been filled with receivers, and we have tagged individual fish from a suite of species. The study has been carrying on for multiple years and so we have almost moment to moment data on fish activity (depth, x-y positioning) for years. The data is remarkable and presents a super interesting take on the activity patterns in different species. We are only just getting at the amount of analysis we can do as the variation across years in climate etc. allow us to use these lakes in a variety of ways to predict the role of climate on behaviour. Fig. 1 shows the response of lake trout and smallmouth bass across seasons. They almost are completely asynchronous in their activity patterns (depth, movement rate) with lake trout moving fairly regularly annual (cold adapted) and smallmouth bass (warm water guild) reducing winter movement strongly.

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Fig. 1 from McMeans et al. 2020. Ecology Letters. Winter in Water. Acoustic telemetry data for lake trout (blue locations and black triangles) and smallmouth bass (red locations and white circles) from Lake of the Two Rivers (Ontario, Canada). (a) Spatial locations of fish in summer (top plot; July and August) and winter (bottom plot; January and February). (b) Mean daily depth (m) of fish within the water column overlaid over the thermal profile (°C) of the lake across the time series. (c) Mean daily bathymetric depth (m) (i.e. depth of water over which fish was positioned). (d) Mean daily activity rates (m min−1). For details on the acoustic telemetry data and analyses, see Supporting Information S1.​​

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We are following lines of research related to this including the modelling of attack rates through predator-prey or consumer-resource activity rates.

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ii) Making Food Web Hotspots and Global Change
Mobile organisms respond to local conditions. We can view global change within this very simple framework, with species being potentially repelled from or attracted to human alterations. Here, we have become fascinated by anthropocentric change that attracts organisms like the way a birdfeeder can attract songbirds (and then hawks). Recent work on lake trout food webs responding to a deep water (in the cold pelagic) cage culture in Georgian Bay has found that lake trout derive a lot of carbon from these pens. Stable isotope and fatty acids have suggested that lakers may be feeding on cold-water pelagic prey that are using escaped feed or carbon derived from DOC pathways generated by the excess nutrients. In this sense, the cage culture attracts prey (cold-water forage fish) and their predators (lake trout) akin to the hawks that follow songbirds to birdfeeders (Johnson et al. 2018). We have since found that warm water, cool water and cold-water fish may be all visiting the cage culture (Gutgesell et al. 2022) although from what we can tell at this point the cold-water community is differentially getting more than the cool and warmwater fish (Fig. 2).

 

Fig. 2. Conceptual figure of food web interactions within (a) natural temperate lake food web and (b) a temperate lake food web with a pelagic point‐source anthropogenic subsidy input, which here is released net‐pen feed. It is predicted that net‐pen feed will be asymmetrically accessible to the surrounding food web depending on the recipient species; thermal preference. It is predicted that cold‐water species will have high subsidy accessibility that will increase cold‐water species biomass, reducing the degree of omnivory exhibited by cold‐water top predators and therefore increasing trophic position. It is expected that accessibility will decrease with increasing thermal guild, in which cool‐water fish have some accessibility and warm‐water fish have the least, and that this pattern will be reflected in their changes in biomass distribution and trophic position. ColdTP, cold‐water mobile top predators; ColdFF, cold‐water forage fish; CoolTP, cool‐water mobile top predators; CoolFF, cool‐water forage fish; WarmTP, warm‐water top predators.

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Similarly, we are now working on the role of a thermal effluent in attracting organisms. Here, a power plant is generating a warm large thermal plume in Lake Huron that may be “heating” up species interactions. Interestingly, the plume runs through areas that have been lake whitefish nurseries and so this intensification could play a role in the suppression of lake whitefish recruitment. This remains to be seen but it is something we are beginning to work on in collaboration with the Saugeen Ojibway Nation.

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Citations
Gutgesell, M., McMeans, B.C., Guzzo, M.M., de Groot, V., Fisk, A.T., Johnson, T.B. and
McCann, K.S., 2022. Subsidy accessibility drives asymmetric food web
responses. Ecology, 103(12), pp.1-12.
Johnson, Laura E., Bailey McMeans, Neil Rooney, Marie Gutgesell, Richard Moccia,
and Kevin S. McCann. "Asymmetric assimilation of an anthropogenic resource subsidy
in a freshwater food web." Food Webs 15 (2018): e00084.
McMeans, B.C., McCann, K.S., Guzzo, M.M., Bartley, T.J., Bieg, C., Blanchfield, P.J.,
Fernandes, T., Giacomini, H.C., Middel, T., Rennie, M.D. and Ridgway, M.S., 2020.
Winter in water: differential responses and the maintenance of biodiversity. Ecology
Letters, 23(6), pp.922-938.