Monday, June 5, 2017
11:00 - 12:30

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11:00 - 11:15: / 305A FOOD WEB DYNAMICS ON BRANCHING RIVER NETWORKS

6/05/2017  |   11:00 - 11:15   |  305A

FOOD WEB DYNAMICS ON BRANCHING RIVER NETWORKS River geometry influences processes such as population persistence, genetic structure, and species diversity. Most related previous work has focused on within trophic-level dynamics, with less emphasis on food web interactions. Yet, river food webs are influenced by processes that may interact with network structure and position. Using spatially-explicit predator-prey models, we explore how trophic dynamics are influenced by the branching nature of river networks. Our models are capable of producing many patterns, including stability, fluctuations, and extinctions. In cases where the predator-prey interaction is prone to cycles and local extinctions, the influence of network structure and dispersal can increase regional persistence and community stability. Regional stability results from asynchrony among dynamics of local habitats: when asynchronous local fluctuations are averaged, predatory-prey dynamics and persistence become less variable at larger spatial scales. Fluctuations synchronize across clusters of linked local habitats; headwater branches typically vary independently of other patches and show high variability, while mainstem habitats show greater clustering and less variability. These patterns suggest than headwater versus mainstem locations in river networks may show differential responses to management and restoration efforts.

Kurt Anderson (Primary Presenter/Author), University of California, Riverside, kurt.anderson@ucr.edu;


Sean Hayes ( Co-Presenter/Co-Author), University of California, Riverside, sean.hayes@email.ucr.edu;


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11:15 - 11:30: / 305A EFFECTS OF FLOW VARIABILITY ON RIVER METACOMMUNITIES IN A CHANGING CLIMATE

6/05/2017  |   11:15 - 11:30   |  305A

EFFECTS OF FLOW VARIABILITY ON RIVER METACOMMUNITIES IN A CHANGING CLIMATE Freshwater flow dynamics are studied with several metrics in the context of global climate change, and one of these approaches involves quantifying flow variation. Though floods and droughts are the primary disturbances studied in relation to macroinvertebrates, inter and intra-annual flow variation has been shown to exert unique pressures on the biological community. In the Sierra Nevada mountains, areas with porous volcanic terrain supply stable spring-fed flow, resulting in less variability than runoff-dominated granite sites. We investigated trends in intra-annual flow variation along ~600km of the Sierra Nevada and related it to the geology. Then, we related regional coefficients of variation to benthic macroinvertebrates and other abiotic variables. In general, we see lower flow variability in areas dominated by volcanic terrain, and the corresponding metacommunities in these regions are more diverse, though with less overall abundance. However, some communities within the same watershed exhibit conflicting abundance and diversity, indicating importance of local processes in dictating flow variability and corresponding community structure, such as agricultural runoff and human diversions. Preliminary results suggest the importance of quantifying patterns of temporal variability in understanding spatial differences in communities.

Parsa Saffarinia (Primary Presenter/Author), University of California, Riverside, psaff001@ucr.edu;


Kurt Anderson ( Co-Presenter/Co-Author), University of California, Riverside, kurt.anderson@ucr.edu;


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11:30 - 11:45: / 305A SPATIAL CONSTRAINTS ON CONSUMER COMMUNITY STRUCTURE AND ASSOCIATED CARBON PROCESSING IN A RIVER NETWORK

6/05/2017  |   11:30 - 11:45   |  305A

SPATIAL CONSTRAINTS ON CONSUMER COMMUNITY STRUCTURE AND ASSOCIATED CARBON PROCESSING IN A RIVER NETWORK River networks have a branching configuration with some reaches more connected to the regional species pool, while other locations, such as headwaters, are more relatively isolated. Evidence is mounting that network position can drive community structure. However, less work has focused on if there are implications for consumer-mediated ecosystem processes. We implemented a study to learn if consumer-resource associations shifted with stream network location. We manipulated resource quality in the form of different leaf litter species in isolated (headwaters) and connected (mainstem) stream reaches, then followed detritivore colonization and litter breakdown rate. While community structure was similar between network locations, richness and abundance were affected by resource quality and network location. Furthermore, headwater environments supported stronger consumer-resource associations that in mainstem environments. Mainstems were likely harsher, thus not conferring the same degree of consumer-resource associations. We conclude that detritivores did not actively feeding on the resources, but rather using the leaf litter as habitat. This suggests that the invertebrate contribution to carbon processing depends not only on resource palatability, but also environmental constraints imposed by network location.

Christopher Swan (Primary Presenter/Author), University of Maryland, cmswan@umbc.edu;


Bryan Brown ( Co-Presenter/Co-Author), Virginia Tech, stonefly@vt.edu;


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11:45 - 12:00: / 305A LONG-TERM IMPACTS OF CACTHMENT CHANGE HISTORY ON NEOTROPICAL METACOMMUNITIES: IMPLICATIONS FOR STREAM RESTORATION

6/05/2017  |   11:45 - 12:00   |  305A

LONG-TERM IMPACTS OF CACTHMENT CHANGE HISTORY ON NEOTROPICAL METACOMMUNITIES: IMPLICATIONS FOR STREAM RESTORATION Metacommunity theory suggests that effective re-colonization and maintenance of viable populations in restored streams require active pathways to a source of colonists. Although there has been advance in metacommunity and stream restoration research recently, observational studies still fail to explain large amounts of variation in metacommunities. One underappreciated concept that needs to be integrated to this filed is historical contingency, as the order and timing of species arrival during community assembly might influence community structure. However, such data is hard to get. But, if what happens in the stream is partly a consequence of the surrounding catchment, then contemporary communities may still respond to characteristics of past landscapes. I modern multivariate statistics to analyzed macroinvertebrate communities in watersheds differing in their land use history. I found that metacommunity structure was explained by a complex combination of local, spatial and land use history variables, but that an interaction between current vegetation cover and land use history was the best predictor. These results suggest that community responses to catchment changes might be delayed due to priority effects and persistent changes in dispersal events, which should matter when choosing streams to be restored.

Tadeu Siqueira (Primary Presenter/Author), Universidade Estadual Paulista - UNESP, Brazil, tsiqueira@rc.unesp.br;


Edineusa Santos ( Co-Presenter/Co-Author), Univerisdade Estadual Paulista (UNESP), edineusa86@gmail.com ;


Anita Costa ( Co-Presenter/Co-Author), Univerisdade Estadual Paulista (UNESP), anitavalentedacosta@gmail.com ;


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12:00 - 12:15: / 305A NATURAL LAND COVER INCREASES STREAM STABILITY FOLLOWING WATER QUALITY PERTURBATIONS

6/05/2017  |   12:00 - 12:15   |  305A

Natural Land Cover Increases Stream Stability Following Water Quality Perturbations Variation in stream recovery rates may be affected by both the choice of methods used to measure recovery and surroundings of the individual stream. After a perturbation, more natural cover may help a stream recover either by improving resilience (providing colonists such that the stream is able to recover quickly) or by improving resistance (providing subsidies and complex habitat for stability through time). We conducted a global meta-analysis to assess 1) which aspects of stream condition recover following a water quality perturbation, and 2) how land cover type impacts stream recovery. Studies primarily focused on recovery of fish, algae, or macroinvertebrate communities as metrics of stream condition. We found that on average, stream condition improves, but fails to reach the pre-perturbation condition. Metric type affected observed recovery: biotic integrity indices recovered more completely than diversity or abundance. Using model selection, we found that more natural riparian cover improves the ability of a stream to resist a water quality perturbation, but also reduces recovery completeness. Preservation of natural land cover may affect stream recovery primarily through improving the stability of aquatic communities.

Bronwen Stanford (Primary Presenter/Author), University of California, Santa Cruz, bstanfor@ucsc.edu;


Erika Zavaleta ( Co-Presenter/Co-Author), UCSC, zavaleta@ucsc.edu;


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