OPS 2-4
Using preliminary NEON data to test aquatic organismal sample timing strategies
The National Ecological Observatory Network (NEON) is a national-scale research platform designed to assess the impacts of climate change, land-use change, and invasive species on ecosystem structure and function distributed over 20 ecoclimatic domains from Alaska to Puerto Rico. Data will be collected using standardized methods, rigorously quality controlled, and made freely available to the public. The NEON Observatory will support 36 aquatic sites including streams, lakes, and large rivers. A suite of aquatic sensors and measurements will provide data on biogeochemistry, surface and groundwater discharge, and site morphology. Organismal measurements include field-based observations and collections of aquatic communities, including microbes, algae, aquatic plants, macroinvertebrates, and fish.
A significant challenge to this effort is to define standardize sampling methods and strategies that will be functional at sites across the continent spanning a variety of geomorphologic and hydrologic regimes. Temporal sampling strategy encompasses the timing of seasonal sampling over diverse ecoclimates, as well as the frequency of annual sampling, to best assess diversity of the aquatic community. Aquatic organismal sample timing will be defined using a suite of environmental variables collected from historical data, local meteorological data, and NEON in situ sensors.
Results/Conclusions
Variables identified as being most influential to aquatic community structure include stream flow or lake ice on/ice off dates (depending on site), degree days, and riparian greening and leaf abscission. Six aquatic sites in southern domains with disjunct seasonal patterns of riparian greening or leaf abscission use only stream flow and degree days to determine sampling windows. Thresholds for these variables were determined using published literature values and used to create sampling windows for each sample site. These sampling windows identify ranges of sampling dates designed to target high community diversity and capture seasonal changes in community structure. Proposed timing generally includes late winter/early spring, mid-summer, and autumn.
Before full operations activities begin at NEON aquatic sites, a limited suite of organismal samples will be collected for six months to estimate patterns of productivity at each site. This limited suite of sampling includes benthic macroinvertebrates and chlorophyll in wadeable streams, and zooplankton and water-column chlorophyll in lakes and large rivers. Macroinvertebrates and zooplankton will be sampled following the pre-determined sampling windows to determine whether the predicted timing targets seasonally different communities at each site. Chlorophyll samples will be taken up to twice per month to determine patterns of productivity at each site.