Understanding biological factors that govern ecosystem processes and functions in freshwater habitats is critical for maintaining water quality and conserving freshwater biodiversity. Using pre-existing data sets from 15N isotope addition studies in headwater streams in various regions of the world, this synthesis workshop will identify relationships between biodiversity, food web structure, and nitrogen cycling in headwater streams. As part of the NSF-funded Lotic Intersite Nitrogen eXperiment (LINX) project and subsequent related studies, investigators used 15N additions to headwater streams in North America, Central America, Europe, Iceland, and New Zealand to trace and model nitrogen cycling in different regions and climates. These tracer studies also generated considerable data on food web structure in these systems, much of which remains unanalyzed. This workshop will assemble a team of seventeen stream ecologists, ranging from graduate students to professors, to analyze and synthesize food web structure and nitrogen cycling in these streams. These analyses will allow for a robust, quantitative examination how food web structure and biodiversity influence nutrient uptake and retention, processes that are critical to water quality, across gradients of precipitation and latitude.
Information generated from this workshop will further our understanding of the consequences of biodiversity losses, exotic species, and climate change to freshwater ecosystem health and function. Results of this synthesis effort will be presented at national meetings, published in the peer-reviewed literature, and made available on the NSF-Long Term Ecological Network (LTER) and LINX project web sites. Many of the workshop participants are early career scientists, who will benefit greatly from their involvement in this effort. This effort will also broaden the scope of LTER research by bringing together LTER and non-LTER investigators and data sets.
This project resulted in two workshops, one held at the Konza Prairie Biological Station in January 2011, and a follow-up in conjunction with the annual meetings of the North American Benthological Society meetings in Providence, RI in June, 2011. Through these workshops, twenty six participants, including numerous graduate students and junior faculty members, standardized datasets from isotope tracer releases (15N) performed in streams in North America, Central America, New Zealand, and Europe. A total of 16 datasets were standardized and compiled. After compiling the datasets, the group worked on developing a spreadsheet based model for estimating nitrogen flux through consumers using changes in 15N levels in consumers and their food sources over time since the tracer addition in each stream. Once this model was developed and tested by all participants, each group ran the models for their sites and data were again compiled in to one large spreadsheet. At this point, the models of nitrogen cycling through consumers in the 16 sites have been completed and the group is beginning to examine large scale patterns of stream nitrogen cycling across the different represented regions. Results of this large-scale, synthetic study will allow for an assessment of the contributions of consumers such as aquatic insects to nitrogen cycling in small streams. Nitrogen uptake and processing in streams is a critical ecosystem function linked to water quality; understanding how consumers influence this process is thus central to water resource management. The datasets and model developed through this workshop will allow for a comprehensive assessment of how consumers influence nitrogen uptake and processing in streams.
