Are freshwater communities subject to local environmental stress more vulnerable to the regional impacts of climate change?

ARE FRESHWATER COMMUNITIES SUBJECT TO LOCAL ENVIRONMENTAL STRESS MORE VULNERABLE TO THE REGIONAL IMPACTS OF CLIMATE CHANGE?

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

COMPLETE

Funding Source

HATCH

Reporting Frequency

Annual

Accession No.

1001932

Grant No.

(N/A)

Cumulative Award Amt.

(N/A)

Proposal No.

(N/A)

Multistate No.

(N/A)

Project Start Date

Jan 14, 2014

Project End Date

Sep 30, 2015

Grant Year

(N/A)

Program Code

[(N/A)]- (N/A)

Project Director
Greig, HA.

Recipient Organization
UNIVERSITY OF MAINE
(N/A)
ORONO,ME 04469

Performing Department
School of Biology & Ecology

Non Technical Summary
Freshwater ecosystems are heavily impacted by a combination of ongoing and accelerating global climate changes and a suite of localized environmental stressors linked to increasing human resource use. These impacts have the potential to strongly degrade freshwater ecosystems and the cultural, economic, and social services (e.g., fisheries) they provide the people of Maine. Although water managers can do little about changes in temperature and hydrological cycles expected with the regional effects of climate change, they can mitigate impacts by prioritizing the maintenance of resilient freshwater ecosystems when making decisions on the sustainability of localized environmental stressors. However the ability to make these decisions is limited by a lack of understanding of how local stressors influence the vulnerability of freshwaters to climate change. My research will reveal mechanisms controlling how local environmental conditions alter the vulnerability of food webs to the regional impacts of climate change. Specific knowledge includes: (1) the identification of physicochemical thresholds across human-modified environmental gradients that identify critical transitions in the vulnerability of stream food webs to climate change perturbations. These thresholds can be used to guide water quality targets for managing changes to local environmental conditions to maximize ecosystem resilience; (2) Analytical tools to detect changes in food-web structure using proxies that are readily available in current biological monitoring data. This information will provide a sound scientific basis for incorporating food-web properties into monitoring and impact assessment of Maine freshwaters, and in doing so, build risks associated with increasing the vulnerability of freshwaters to climate change into water management decisions. Information gained during this study will therefore help maintain robust ecological communities that minimize the negative effects of climate change on Maine freshwater ecosystems and the services they provide.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
135	0899	1070	50%
135	0210	1190	50%

Knowledge Area
135 - Aquatic and Terrestrial Wildlife;

Subject Of Investigation
0899 - Wildlife and natural fisheries, general/other; 0210 - Water resources;

Field Of Science
1070 - Ecology; 1190 - Limnology;

Keywords

freshwater ecosystem health

ecosystem vulnerability

biological monitoring

Goals / Objectives
I will address three objectives in determining how local sources of natural and anthropogenic environmental stress influence the regional effects of climate changes on freshwater ecosystems. Objective 1: a) Utilize existing DEP biomonitoring databases in wetland and riverine habitats to reveal the key natural and anthropogenic gradients affecting freshwater trophic structure in Maine; and b) to determine whether current biomonitoring classifications detect adverse changes in trophic structure. Objective 2: Explore the relative effects of natural disturbance (spates and drying) and human land-use (urbanization and agriculture) on streams and vernal pool food webs. Objective 3: Experimentally investigate how changes in food-web structure that result from local environmental stress influence the vulnerability of freshwater ecosystems to the regional perturbations from climate change.

Project Methods
Objective 1: In collaboration with freshwater ecologists from Maine DEP, I will analyze the current biological monitoring database to investigate the impact of natural and anthropogenic environmental gradients on freshwater food webs. I will use the database in a novel way by partitioning the abundance of commonly-assayed organisms into three trophic levels (predators, herbivores and algae) to quantify how the trophic structure of food webs (e.g., relative abundance of predators and prey) change with local environmental stress. I will use a combination of existing physical data and variables derived from GIS and other databases (e.g., USGS hydrological data) to quantify gradients of natural (hydrology, elevation, habitat size, eco-region) and human-modified (% urbanization, % agricultural land use, % forestry, proximity to road networks) environmental conditions. I will perform hierarchical mixed-effects model selection (Zuur et al. 2009) to assess the key environmental gradients driving trophic structure, and determine whether natural and human stressors have independent or interactive effects. This analysis of existing data will enable the rapid completion of two short-term outcomes (Outcome Measures 1a, b), and provide critical background information that underlies Objectives 2 & 3. Objective 2: Although the DEP database enables the quantification of some aspects of trophic structure, a more complete picture of food-web stability requires higher resolution sampling in a subset of habitat types. Building upon current research programs in vernal pools and data gathered from Maine streams in Objective 1, I will survey multiple components of food-web structure in freshwaters spanning gradients of urban (Morse et al. 2003) and agricultural impact (Cronan et al. 1999), and natural gradients of hydrological disturbance (spates and drying). I will quantify the properties of food webs based upon a combination of quantitative community sampling and stable nitrogen-15 and carbon-13 isotope analysis of species' body tissue (Thompson et al. 2012a). The structure of food webs will be characterized using five complementary metrics that are linked to food-web stability: (i) the size of food webs as determined by number of species detected at each site; (ii) food-web shape based on predator:prey species richness ratios; (iii) food-chain length based on the 15N enrichment of top consumers (Post 2002); (iv) basal resource diversity quantified by the range in d13C observed in a community (Layman et al. 2007); and (v) total trophic area given by the d13C-d15N range observed across a community (Layman et al. 2007). Quantifying food webs across multiple environmental gradients in multiple freshwater types will produce a broadly applicable understanding of the natural and anthropogenic factors driving changes in food webs. Objective 3: Many aspects of freshwater ecosystems can be realistically replicated and manipulated in mesocosms, with observed effects that scale-up to natural ecosystems. I will use experiments in artificial streams and ponds to test how the changes in food-web properties with environmental stress (i.e., objectives 1 & 2) alter the vulnerability of ecosystems to manipulations of regional-scale climate change perturbations (warming, and altered flood and drought frequency). Experiments will be conducted at three complementary spatiotemporal scales: (a) 24 hour trials in indoor aquaria measuring the effects of temperature and hydrological change on of feeding rates. These rates can be scaled up to understand the dynamics of whole food webs under climate change by using a modeling framework my collaborators and I have developed (Gilbert et al. In review); (b) direct manipulations of food-webs and temperature in artificial ecosystems that test how food-web structures associated with local environmental stress affect ecosystem vulnerability to warming; (c) experiments in bank-side channels/pools that enable the quantification of the variability, resistance and resilience of food webs to temperature and flow perturbations over long temporal scales (ice-free months). Objective 3 represents an ongoing program of work that builds on the system-specific understanding generated by the first two objectives, and will form the basis of subsequent MAFES and external funding proposals.

Progress 01/14/14 to 09/30/15

Outputs
Target Audience:Although the primary target audiences are state (Maine DEP) and national (EPA) water managers and international freshwater ecologists, outputs will also target community groups by communicating the importance of maintaining robust food webs that support freshwater ecosystems. Examples of community groups include the Penobscot River Restoration Trust, local communities associated with vernal pools conservation, the Downeast Salmon Federation and a range of other local salmon and fly fishing associations. Research will also be communicated to industry groups (e.g., Maine fishing guides, water districts and hydropower companies) that utilize freshwaters, and thus benefit from its sustainable use. Changes/Problems:Synthesis of biological monitoring data to assess Objective 1a is still underway and is being analyzed in collaboration with a M.S student. This work will fold in to the current project ME021607. What opportunities for training and professional development has the project provided?This project has trained two graduate students and two undergraduate honors in the applied food-web ecology of freshwaters. This training has included professional skill development in addition to mentoring research and scientific communication skills. Our research team has also mentored and trained eight undergraduate research assistants and two Wabanaki Youth in Science program high school interns over the course of the project. As a result, graduate and undergraduate students have received training and experience in mentoring students and coordinating research teams. How have the results been disseminated to communities of interest?In addition to the products listed in this report, results have been disseminated via community engagement, media coverage, inclusion of results into undergraduate and graduate teaching, and participation in collaborative working groups. Specific instances include: Scientific workshops attended I was an invited member of a Stream Sensitivity Focus Group run by MS student Kristen Weil. This group brought together state and local stream ecologists and water managers to develop a Bayesian Belief Network based on expert opinion to determine which streams in Maine are most susceptible to degradation. Member of the Stream Temperature Working Group, which is a collaboration of freshwater and fisheries scientists and resource managers from Maine DEP, Maine IFW, NOAA, USFWS, Penobscot Nation and the Atlantic Salmon Federation. We are developing a coordinated and consistent stream temperature monitoring network statewide, and building platforms for the wider dissemination of Maine stream temperature data. Community outreach that resulted in information transfer 2014 - 2015: Mentored two Native American high school students during summer research internships as part of the Wabanaki Youth Science Program. Guest Speaker, Gorges River Trout Unlimited, 3/9/2015. The talk discussed introduced the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Guest Speaker, Brewer Cabin Fever Reliever event, 2/28/2015. The talk discussed introduced the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Guest Speaker, Maine Sportsman's Show, 2/21/2015. The talk discussed introduced the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Developed and ran the session on "Bugs and Flies" for the Penobscot Fly Fishers introductory fly fishing course. April 2014 and April 2015. The interactive class featured live material demonstrations, preserved insects, and a presentation of photographs and videos. Guest Speaker, MDI High School Adult Education fly fishing class. March 2014. I presented material introducing the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Participated in discussion group with the Kezar Lake Watershed Association, Greater Lovell Land Trust, and FB Environmental to help develop a Climate Change Observatory in the western Maine -Kezar Lake Watershed in 2014, and build a long-term citizen-led climate-change program in Maine. Guest Speaker, Penobscot Fly Fishers, May 2014. The talk discussed introduced the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Ran the entomology competition of the Maine section of the 2014 Science Olympiad. This was an inaugural year of the event at UMaine. Guest Speaker, Penobscot Fly Fishers, November 2013. The talk discussed the links between freshwater science and fly fishing for New Zealand trout. What do you plan to do during the next reporting period to accomplish the goals?Although this is a final report for this project, many of the objectives will be continue to be addressed in my current NIFA project ME021607. Moreover, publications arising from the experiments addressing Objectives 2 and 3, including both peer-reviewed manuscripts and two M.S. theses, are in progress and will be completed within the next 12 months.

Impacts
What was accomplished under these goals? Objective 1 was completed with a literature synthesis investigating whether freshwater biomonitoring programs were sufficient to detect adverse changes in food webs and other measures of freshwater integrity. This publication, which was an invited book chapter co-authored by Aram Calhoun (UMaine Department of Wildlife, Fisheries and Conservation Biology), made a series of recommendations on how to improve the use of biological information in wetland assessment. Recommendations aligned with this project included i) developing closer links between structural and functional measures of ecosystems, and ii) incorporating the confounding effects of spatial and temporal drivers of ecological processes. Objective 2: Progress on this objective included both field surveys and manipulative experiments. Results from a field survey of the impact of urbanization on the structure and function of vernal pool food webs revealed that the more open canopies of urban vernal pools produced communities more dependent on algal resources, whereas the heavily shaded vernal pools in unmodified forest were dominated by detritivores consuming terrestrial leaf litter. We are continuing to explore the implications these changes have for the complexity of food webs and the diversity of energy sources upon which these ecosystems are based. For example, Honors student Cara Rudnicki completed an investigation of the effects of road salt on feeding relationship common to both stream and vernal pond food webs. These experiments revealed that increasing concentrations of road salt impairs the feeding rates of consumers on both algae and detritus, potentially reducing the flows of energy through stream food webs. Assessing the effects of natural disturbances on stream food webs was completed with a series of field experiments that manipulated the frequency of substrate-moving disturbances in artificial channels placed within natural streams. Results indicated that disturbances directly dislodged biota and had indirect effects via reductions in food resources. These impacts increased in severity as the frequency of disturbance events increased, resulting in the reduction in the diversity and abundance of invertebrates and the loss of larger predators. Objective 3: This objective has been investigated with parallel experiments in artificial stream channels and pond mesocosms. These experiments used staggered dates of installation to establish communities that reflect different periods of recolonization following a disturbance. We then subject communities to a standardized disturbance (flooding in streams and drying in ponds) to assess the effects of community age on ecosystem vulnerability to climate-linked hydrological disturbances. Experiments in both pond mesocosms and stream channels reveled that communities arising from differing historical disturbance regimes differed in their resilience to new disturbance events, suggesting that changing disturbance regimes may affect ecosystem vulnerability. Moreover the consistency in outcomes between pond and stream experiments suggests that the influence of disturbance history on ecosystem vulnerability may be consistent across different freshwater systems. This objective will form the basis of a MS thesis (writing underway) and will continue to be investigated in my subsequent MAFES project.

Publications

Type: Journal Articles Status: Published Year Published: 2015 Citation: Atwood, T. B., E. Hammill, P. Kratina, H. S. Greig, J. B. Shurin, and J. S. Richardson. 2015. Warming alters food web-driven changes in the CO2 flux of experimental pond ecosystems. Biology Letters 11: 20150785. DOI: 10.1098/rsbl.2015.0785
Type: Book Chapters Status: Awaiting Publication Year Published: 2016 Citation: Greig, H. S. and M. L. Galatowitsch. In press. Hydrology and ecology of ponds.in C. P. Pearson, T. Davie, P. G. Jellyman, and J. S. Harding, editors. Advances in New Zealand freshwater science: New Zealand Hydrological Society and New Zealand Limnological Society, Christchurch, New Zealand.
Type: Book Chapters Status: Awaiting Publication Year Published: 2016 Citation: Greig, H. S. and A. J. K. Calhoun. In press. Searching for the holy grail of wetland integrity: are biological indicators still relevant in conservation planning? in D. Lindenmayer, J. Pierson, and P. Barton, editors. Surrogates and Indicators in Ecology, Conservation and Environmental Management. CSIRO Publishing, Melbourne, CRC Press, London.
Type: Journal Articles Status: Published Year Published: 2015 Citation: *Lindenmayer, D., J. Pierson, P. Barton, M. Beger, C. Branquinho, A. Calhoun, T. Caro, H. Greig, J. Gross, J. Heino, M. Hunter, P. Lane, C. Longo, K. Martin, W. H. McDowell, C. Mellin, H. Salo, A. Tulloch, and M. Westgate. 2015. A new framework for selecting environmental surrogates. Science of the Total Environment. doi:10.1016/j.scitotenv.2015.08.056
Type: Journal Articles Status: Published Year Published: 2015 Citation: McHugh, P. A., R. M. Thompson, H. S. Greig, H. J. Warburton , and A. R. McIntosh. 2015. Habitat size influences food web structure in drying streams. Ecography. 38: 700-712.
Type: Journal Articles Status: Published Year Published: 2015 Citation: Kitto, J.A.J., D.P. Gray, H.S. Greig, D.K. Niyogi, and J.S. Harding. 2015. Meta?community theory and stream restoration: evidence that spatial position constrains stream invertebrate communities in a mine impacted landscape. Restoration Ecology 23:284-291.
Type: Journal Articles Status: Published Year Published: 2015 Citation: DeLong, J.P., B. Gilbert, J.B. Shurin, V.M. Savage, T.B. Brandon, C.F. Clements, A.I. Dell, H.S. Greig, C.D.G. Harley, P. Kratina, K.S. McCann, T.D. Tunney, D.A. Vasseur, and M.I. OConnor. 2015. The Body Size Dependence of Trophic Cascades. The American Naturalist 185:354-366.
Type: Journal Articles Status: Published Year Published: 2015 Citation: Gilbert, B., T.D. Tunney, K.S. McCann, J.P. DeLong, D.A. Vasseur, V. Savage, J. B. Shurin, A.I. Dell, B.T. Barton, C.D.G. Harley, H.M. Kharouba , P. Kratina, J.L. Blanchard, C. Clements, M. Winder, H.S. Greig, & M.I. OConnor. 2014. A bioenergetic framework for the temperature dependence of trophic interaction strength. Ecology Letters. 17:902-914.
Type: Journal Articles Status: Published Year Published: 2014 Citation: Vasseur, D.A., J.P. DeLong, B. Gilbert, H.S. Greig, C.D.G. Harley, K.S. McCann, V. Savage, T.D. Tunney , & M.I. OConnor. 2014. Increased temperature variation poses a greater risk to species than climate warming. Proceedings of the Royal Society B: Biological Sciences.281: 2013-2612.
Type: Theses/Dissertations Status: Published Year Published: 2015 Citation: Veitch, E. M. 2015. Evidence for aquatic ecosystem augmentation across a gradient of increasing terrestrial subsidy quality. B.Sc. Honors thesis. University of Maine.
Type: Theses/Dissertations Status: Published Year Published: 2015 Citation: Rudnicki, C. 2015. Effects of road salt on the feeding rates of macroinvertebrates. B. Sc. Honors thesis. University of Vermont.
Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Greig H.S. 2015. Experimental evidence that hemlock decline changes the role of detrital subsidies in freshwater food webs. Invited talk for the special session Effects of disturbance on consumer mediated habitat linkages. 100th Annual Meeting of the Ecological Society of America, Baltimore, MD.
Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Greig, H. S. 2015. Unraveling the multiple impacts of climate change on forested freshwater ecosystems. Invited talk for the special session The science and management of cumulative effects of multiple stressors on forested landscapes. Northeastern Ecosystems Research Co-operative biennial meeting, Saratoga Springs, NY.
Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Jackson, R., N. Tomczyk, L. Podzikowski, H.S. Greig, K. Capps. Patterns in macro-invertebrate community composition in vernal pools in the northeastern United States. 2014 Joint Aquatic Sciences Meeting, Portland, OR. Abstract ID: 13122.
Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Wissinger, S.A., A.J. Klemmer, E.J. Thornton, M. Perchik, R.J. Burns, H.S. Greig, and C. Eddy. Density-dependent nutrient cross-links between detritus processing and benthic algae in shallow ponds and wetlands. 2014 Joint Aquatic Sciences Meeting, Portland, OR. Abstract ID: 14028.
Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: McIntosh, A.R., S.E. Graham, J.M. O'Brien, C.M. Febria, P.A. McHugh, H.S. Greig and J.S.; Harding. Using food-web theory to enhance the effectiveness of aquatic restoration. 2014 Joint Aquatic Sciences Meeting, Portland, OR. Abstract ID: 14171
Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Greig, H.S. Understanding the contingencies: how environmental context alters the effects of warming on freshwater food webs. 2014 Joint Aquatic Sciences Meeting, Portland, OR. Abstract ID: 14399.
Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Weil, K., C.S. Cronan, R.J. Lilieholm, C.S. Loftin, H.S. Greig, M. Johnson and S.R. Meyer. A spatial analysis of biophysical watershed characteristics affecting stream response to land-use changes in Maine, U.S.A. 2014 Ecological Society of America Annual Meeting, Sacramento, CA.

Progress 01/14/14 to 09/30/14

Outputs
Target Audience: Although the primary target audiences of my project are state (Maine DEP) and national (EPA) water managers and international freshwater ecologists, outputs will also target community groups by communicating the importance of maintaining robust food webs that support freshwater ecosystems. In addition to directly collaborating with Maine DEP scientist from the Biological Monitoring Program, my work has reached abroad target audience of freshwater and fisheries scientists and resource managers from Maine DEP, Maine IFW, NOAA, USFWS, Penobscot Nation and the Atlantic Salmon Federation during participation in working groups and focus groups. I have reached International audience of aquatic scientists and ecologists by presenting and co-presenting research at the Joint Aquatic Sciences Meeting, Portland, Oregon, 2014, and 2014 Ecological Society of America Annual Meeting, Sacramento, CA, and submitting scientific publications for review in peer-reviewed outlets.Finally, I have interacted with a number of community groups through solicited consultation, delivering presentations and organizing education events. These groups include high school students from the Wabanaki Youth Science Program and participants in the 2014 Maine Science Olympiad, local recreation groups including Penobscot Fly Fishers and Mount Desert Island fly fishing classes, and lake watershed groups including the Kezar Lake Watershed Association, Greater Lovell Land Trust. . Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? In addition to strongly contributing to the professional development of the project director, this project has provided opportunities to train two graduate students and two BS Honors students in the use of experimental and observational approaches for understanding the response of freshwater ecosystems to climate change. In addition, summer internships have provided opportunities for high school students connected to the Wabanaki Youth Science Program to experience the process of field based ecological research. How have the results been disseminated to communities of interest? In addition to the publications listed herein, the results of this research have been disseminated to widespread audiences through participation freshwater resource management workshops, focus groups, and through public presentations. These interactions include: Working group participation I was an invited member of a Stream Sensitivity Focus Group run by UMaine MS student Kristen Weil. This group brought together state and local stream ecologists and water managers to develop a Bayesian Belief Network based on expert opinion to determine which streams in Maine are most susceptible to degradation. *Member of the Stream Temperature Working Group, which is a collaboration of freshwater and fisheries scientists and resource managers from Maine DEP, Maine IFW, NOAA, USFWS, Penobscot Nation and the Atlantic Salmon Federation. We are developing a coordinated and consistent stream temperature monitoring network statewide, and building platforms for the wider dissemination of Maine stream temperature data. Community outreach that resulted in information transfer Guest Speaker, Penobscot Fly Fishers, November 2013. The talk discussed the links between freshwater science and fly fishing for New Zealand trout. Guest Speaker, MDI High School Adult Education fly fishing class. March 2014. I presented material introducing the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Ran the entomology competition of the Maine section of the 2014 Science Olympiad. This was an inaugural year of the event at UMaine. Developed and ran the session on "Bugs and Flies" for the Penobscot Fly Fishers introductory fly fishing course. April 2014. The interactive class featured live material demonstrations, preserved insects, and a presentation of photographs and videos. Guest Speaker, Penobscot Fly Fishers, May 2014. The talk discussed introduced the common aquatic insects of Maine, how they are identified, and their importance to recreational fish diets. Participated in discussion group with the Kezar Lake Watershed Association, Greater Lovell Land Trust, and FB Environmental to help develop a Climate Change Observatory in the western Maine -Kezar Lake Watershed in 2014, and build a long-term citizen-led climate-change program in Maine. Media coverage September 2014: Collaborative research on the impacts of past and present hemlock declines on aquatic ecosystems featured by The Republic, Sun Journal, SFGate, WABI (Channel 5) WVII (Channel 7). What do you plan to do during the next reporting period to accomplish the goals? Planned work for the period prior to the next reporting period will focus on competing the analysis of the Maine biological monitoring database to investigate the impact of natural and anthropogenic environmental gradients on freshwater food webs (Objective 1a), and completing a mesocosm experiments outlined in Objective 3 investigating the interactive effects of temperature change and disturbance on food webs. Additional activities will focus on data analysis and publication of the work reported in this progress report.

Impacts
What was accomplished under these goals? Objective 1b was completed with a literature synthesis investigating whether freshwater biomonitoring programs were sufficient to detect adverse changes in food webs and other measures of freshwater integrity. This publication, which was an invited book chapter co-authored by Aram Calhoun (UMaine Department of Wildlife, Fisheries and Conservation Biology), made a series of recommendations on how to improve the use of biological information in wetland assessment. Recommendations aligned with this project included i) developing closer links between structural and functional measures of ecosystems, and ii) incorporating the confounding effects of spatial and temporal drivers of ecological processes. Objective 2: Progress on this objective included both field surveys and manipulative experiments. Results from a field survey of the impact of urbanization on the structure and function of vernal pool food webs revealed that the more open canopies of urban vernal pools produced communities more dependent on algal resources, whereas the heavily shaded vernal pools in unmodified forest were dominated by detritivores consuming terrestrial leaf litter. Analysis is underway on the implications these changes have for the complexity of food webs and the diversity of energy sources upon which these ecosystems are based. Assessing the effects of natural disturbances on stream food webs was completed with a field experiment that manipulated the frequency of substrate-moving disturbances in artificial channels placed within natural streams. Results indicated that disturbances directly dislodged biota and had indirect effects via reductions in food resources. These impacts increased in severity as the frequency of disturbance events increased, resulting in the reduction in the diversity and abundance of invertebrates and the loss of larger predators. Finally, laboratory experiments on the effects of urbanization of stream organisms showed that increasing concentrations of road salt reduced feeding rates of consumers on both algae and detritus, potentially reducing the flows of energy through stream food webs. Objective 3: The primary focus of this objective was building the capacity to of conduct experimental investigations of how changes in food-web structure as a result of local disturbances alter ecosystem vulnerability to climate change. This objective will continue to be investigated in my subsequent MAFES project. Outcomes from Objective 2 have provided a significant step towards this capacity by providing the basis for designing manipulative experiments to investigate how localized environmental stresses alter ecosystem responses to climate change manipulations. Furthermore, we trialed the use in in-stream mesocosm experiments to directly manipulate flow disturbance, and I secured funding to develop both indoor and outdoor experimental arenas suitable for temperature manipulations.

Publications

Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: *Jackson, R., N. Tomczyk, L. Podzikowski, H.S. Greig, K. Capps. Patterns in macro-invertebrate community composition in vernal pools in the northeastern United States. 2014 Joint Aquatic Sciences Meeting, Portland, OR. Abstract ID: 13122
Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: *Greig, H.S. Understanding the contingencies: how environmental context alters the effects of warming on freshwater food webs. 2014 Joint Aquatic Sciences Meeting, Portland, OR. Abstract ID: 14399.