Background - The invasive diatom Didymosphenia geminata (didymo) has historically been a wide-spread, but rare, micro algae found in moderately flowing cold-water streams of North America, Europe, Asia, and (more recently) New Zealand. Demographic patterns of didymo have recently changed resulting in greater spatial coverage and temporal persistence (e.g. blooms) in streams worldwide. Didymo blooms can form dense “woven fabric” aggregate up to 20 cm think, that trap algae, macroinvertebrates, detritus and other debris. The recent discovery of didymo in parts of New York State, including the Upper Esopus Creek in 2009, is concerning because blooms can affect benthic habitat, river hydraulics, the structure and function of lotic ecosystems (primary production and periphyton, macroinvertebrate, and fish communities), local recreation (fishing and tubing), and regional economies. Although some relations between didymo blooms and stream flow, velocity, temperature, and nutrients are being developed, the basic knowledge necessary to devise management strategies and control nuisance blooms does not exist. Thus, environmental cues that cause local nuisance blooms, reasons for its expansion into the Esopus, severity of ecosystem impacts, influence of waters from the Shandaken Portal, and various management and control strategies are uncertain, and cannot be predicted in this stream, or in nearby sub-basins.
Objectives - Primary objectives of this study are to collect information needed to better understand and possibly control nuisance didymo blooms and to minimize ecosystem impacts in the Upper Esopus Creek and other streams of the region. Related goals are to: (a) quantify relations between didymo densities and water quality, hydrology, temperature, and turbidity; (b) identify factors that influence/cause didymo blooms; (c) assess the impacts of didymo on local biotic communities; and (d) determine if alternate management strategies for supplemental (portal) flows could be used to control didymo blooms in the Upper Esopus Creek.
Approach - Triplicate didymo (periphyton) samples will be collected from 6 to 8 main stem sites in the Upper Esopus Creek (Figure 2) at least three times (fall, early spring, and late spring) and consist of quantitative and qualitative rock scrapes from riffles generally following standard methods without transects or multiple habitats. Comparable data from 20 sites sampled in August will also be compiled and used to assemble one or more USGS reports or peer-reviewed journal articles that assess patterns of didymo distributions and potential controlling factors in the watershed. These reports will also quantify the relations among didymo density, periphyton standing crop and fatty acid content, and indicators of fish, diatom, and macroinvertebrate community health to characterize potential adverse effects of didymo blooms on local aquatic ecosystems in the Upper Esopus Creek watershed. Findings may also be used to evaluate various water-management strategies that could help control nuisance blooms of didymo in the Upper Esopus, in other streams in NYC Water-Supply Watersheds, and other areas impacted by this invasive species.
Publications - George SD, Baldigo BP (2015) Didymosphenia geminata in the Upper Esopus Creek: Current Status, Variability, and Controlling Factors. PLoS ONE 10(7): e0130558. doi:10.1371/journal.pone.0130558