AQUATIC MACROINVERTEBRATE and DIATOM SURVEYS in TETLIN NATIONAL WILDLIFE REFUGE, AK Final Report December 2012
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AQUATIC MACROINVERTEBRATE AND DIATOM SURVEYS IN TETLIN NATIONAL WILDLIFE REFUGE, AK Final Report December 2012 Prepared by: Daniel Rinella, Daniel Bogan, and Rebecca Shaftel Alaska Natural Heritage Program University of Alaska Anchorage Beatrice McDonald Hall 3211 Providence Dr. Anchorage, AK 99508 Tetlin Macroinvertebrate and Diatom Surveys Table of Contents INTRODUCTION 1 METHODS 1 Stream habitat measurements 3 Macroinvertebrate and diatom sampling 4 Sample processing 4 Data analysis 5 RESULTS AND DISCUSSION 6 CONCLUSIONS 16 REFERENCES 17 i Tetlin Macroinvertebrate and Diatom Surveys Tables Table 1. Selected habitat characteristics for Desper, Gardiner, and Scottie Creeks. ........................................ 8 Table 2. Average taxa richness for macroinvertebrate and diatom quantitative and multi-habitat samples over the four year sampling period. Quantitative samples were pooled to calculate richness. ................... 8 Table 3. Jaccard (persistence) and Bray-curtis (stability) distances for macroinvertebrate communities from Desper, Gardiner, and Scottie creeks based on three inter-annual comparisons from 2007 to 2010. ...............................................................................................................................................................................................15 Table 4. Jaccard (persistence) and Bray-curtis (stability) distances for diatom communities from Desper, Gardiner, and Scottie creeks based on three inter-annual comparisons from 2007 to 2010. .......................15 Figures Figure 1. Sampling sites in Tetlin National Wildlife Refuge. ....................................................................2 Figure 2. Photos of Desper Creek (A), Gardiner Creek (B), and Scottie Creek (C). ...................................7 Figure 3. Hydrologic conditions at the time of sampling as indicated by stage and discharge readings for Desper, Gardiner, and Scottie creeks. ..................................................................................................9 Figure 4. Macroinvertebrate abundances from the quantitative samples for the six most frequently encountered taxa in Desper, Gardiner, and Scottie creeks from 2007 to 2010. ..................................... 11 Figure 5. Diatom abundances from the quantitative samples for the six most frequently encountered taxa in Desper, Gardiner, and Scottie creeks from 2007 to 2010. ......................................................... 12 Figure 6. NMS ordination for macroinvertebrates at Desper, Gardiner, and Scottie creeks over four year sampling period. ............................................................................................................................... 13 Figure 7. NMS ordination for diatoms at Desper, Gardiner, and Scottie creeks over four year sampling period. .............................................................................................................................................14 Appendices Appendix 1. Macroinvertebrate taxa list Appendix 2. Diatom taxa list ii Tetlin Macroinvertebrate and Diatom Surveys INTRODUCTION This report summarizes the results from macroinvertebrate and diatom surveys conducted in Desper, Gardiner, and Scottie creeks; lowland streams in Tetlin National Wildlife Refuge, interior Alaska. These three streams were sampled repeatedly during the summers of 2007 through 2010. The objectives of this study were to characterize the stream biological communities for streams in the Tetlin Refuge where data currently does not exist. Sites were sampled over several years in order to describe inter-annual changes in community composition. Macroinvertebrates and diatoms have been used in biomonitoring to indicate the quality of the aquatic ecosystems in which they reside. Since they integrate attributes of their chemical and physical environments over their lifespans, taxa presence and abundance can be better predictors of past environmental conditions than snapshot water quality measurements. Potential disturbances to streams in this region include climate change, development along the Alaska Highway system, and the proposed Alaska natural gas pipeline. In addition to describing macroinvertebrate and diatom community composition, the inter- annual persistence and stability of macroinvertebrate and diatom assemblages are important considerations for monitoring programs. Persistence measures the presence or absence of individual taxa over time, while stability includes both the presence/absence and the abundance of taxa over time. Aquatic habitats characterized by high community persistence and stability facilitate the detection of ecological changes over time. Low persistence and stability among macroinvertebrate communities in montane streams of Denali National Park, also in interior Alaska, was found to limit their applicability for ecological monitoring (Milner et al. 2006). Macroinvertebrate persistence and stability in the Denali streams was related to winter snow depth and channel stability (Milner et al. 2006), factors which may also affect streams in the Tetlin refuge. To our knowledge, no prior published studies have examined persistence and stability among diatom communities. METHODS Sites were selected based on their accessibility via the Alaska Highway. Figure 1 shows the location of the three sampling sites within the Tetlin National Wildlife Refuge. 1 Tetlin Macroinvertebrate and Diatom Surveys Figure 1. Sampling sites in Tetlin National Wildlife Refuge. 2 Tetlin Macroinvertebrate and Diatom Surveys Stream habitat measurements Stream habitat measurements were collected in the first year of sampling (2007) to characterize differences in channel morphology, riparian vegetation, and substrate composition between the three streams. We conducted habitat assessments using protocols from EPA’s Environmental Monitoring and Assessment Program (EMAP, Kaufman and Robinson 1998) to characterize in-stream and riparian habitat at each of 11 evenly spaced transects along the stream reach. Each stream reach was 150 m in length. Measurements collected at each transect included channel wetted width, bankfull width, bank height, bank angle, and bank undercut distance. We measured riparian canopy coverage with six densiometer readings along each transect. We recorded water depth, substrate size class, and embeddedness at five points along each transect. To characterize fish cover we estimated the extent of filamentous algae, macrophytes, big and small woody debris, live trees or roots, overhanging vegetation, undercut banks, and boulders at each transect using five areal cover classes (0%, <10%, 10-40%, 40-75%, or >75%). Between each of the 11 transects, we counted pieces of large woody debris within and above the bankfull channel according to several size classes. We characterized riparian vegetation cover separately for canopy, understory, and ground cover along the entire stream reach using five areal cover classes (0%, <10%, 10-40%, 40-75%, or >75%) and several types (deciduous, coniferous, mixed, or none). To characterize channel slope and sinuosity, we recorded the compass azimuth (aspect) and channel slope between each pair of transects. The U.S. Fish and Wildlife Service collects continuous hydrologic stage measurements at each of these creeks in order to estimate discharge, in addition to collecting periodic water quality samples throughout the year. For Scottie and Desper creeks, stage measurements were provided for each sampling date and for Gardiner Creek, preliminary discharge measurements were provided. These measurements will enable comparisons within each creek between the hydrologic conditions and the aquatic biological communities over the four year sampling period. A total of 15, 17, and 18 water quality samples were collected at Desper, Gardiner, and Scottie creeks from June 2006 to September 2009. The suite of constituents measured included hardness, pH, nutrients, dissolved organic carbon, specific conductance, numerous metals, and various inorganic salts. For this report, water quality parameters known to affect stream biological communities were summarized for the three streams to qualitatively describe differences in their chemistry. 3 Tetlin Macroinvertebrate and Diatom Surveys Macroinvertebrate and diatom sampling For both macroinvertebrates and diatoms we collected five quantitative subsamples from the benthic habitat in order to characterize variation in taxa abundance within a stream. Stream substrates were targeted for the quantitative subsamples so that the sampling area could be easily defined and measured, which is more difficult when sampling other habitats, such as streambanks or overhanging vegetation. Quantitative macroinvertebrate samples were collected using either a modified Surber sampler with 350-µm mesh in shallow water or an Eckman grab for deep water with fine substrates. Quantitative diatom samples were collected by scrubbing a fixed area (delineated by a bedrock sampler) on submerged woody snags or by skimming the top layer of streambed sediments (delineated by a sediment sampler). We also collected semi-quantitative multi-habitat samples of macroinvertebrates and diatoms that we expected might provide a more comprehensive characterization of the biological communities. For both macroinvertebrates and diatoms, the multi-habitat sample was composed of 20 subsamples taken throughout the stream reach. All substrate types (i.e., sand/fine substrates, gravel/cobble substrates, undercut streambanks, woody