Lake Kapowsin Biological Inventory
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Final Report Lake Kapowsin Biological Inventory Prepared for: Washington Department of Natural Resources Aquatic Reserves Program 1111 Washington Street SE, PO Box 47016 Olympia, WA 98504-7016 Prepared by: Hamer Environmental L.P. P.O. Box 2561 Mount Vernon, WA 97273 www.HamerEnvironmental.com 30 June 2015 EXECUTIVE SUMMARY The biological inventory of Lake Kapowsin was conducted with the goal of providing a baseline snapshot of lake conditions, and of the habitats and wildlife associated with the lake system. Lake Kapowsin is the first freshwater aquatic system to be considered for enrollment in the state Aquatic Reserves Program. The intent of this report is to provide baseline information on the lake to Washington State Department of Natural Resources (WDNR) for development of lake management and monitoring plans. Highlighted Findings Limnology: Physical habitat: The riparian canopy along the banks of Lake Kapowsin was varied, dominated by deciduous forest along the western shores and conifer or mixed forest along the eastern shores. Within the lake there was a large amount of tree stumps, floating logs and macrophytic vegetation. The littoral substrate cover at the physical habitat sampling stations was dominated by silt, clay or muck, followed by woody debris and organic material. Water chemistry: Preliminary data suggest that Lake Kapowsin is a mesotrophic to eutrophic lake system that thermally and chemically stratifies in the spring and summer potentially leading to anoxic and low pH conditions in the deeper portions of the lake. Additional sampling during summer and fall months is recommended to test these hypotheses. Macroinvertebrates: Twenty-seven unique invertebrate taxa in 7 orders were documented at Lake Kapowsin, including one non-native aquatic mollusk, the Chinese mystery snail (Cipangopaludina chinensis malleata). Seventy-six percent of the macroinvertebrates collected were crustaceans: among these, the isopod Caecidotea sp. and the amphipod Crangonyx sp. were the dominant taxa. Macroinvertebrate communities found in the lake were dominated by detritivores, due to the large amounts of woody debris found in the lake. Aquatic plants: No aquatic invasive or rare plants were documented on Lake Kapowsin, though this effort was not a complete survey. A total of 45 aquatic plant species (submerged, floating & emergent) were documented, indicating high species diversity. Wetlands: Several wetland sites at the north end of the lake and Jaybird Island, contained plant communities exclusive to bogs, but only a portion of one wetland met the plant cover requirements to be rated as a bog. However, these wetlands are in the process of becoming bogs, which are specialized habitats containing unique species, acidic water conditions, and are highly susceptible to degradation from human impacts. Lake fringe wetlands dominated by common cat-tail (Typha latifolia), yellow flag iris (Iris pseudoacorus), and yellow pond lily (Nuphar lutea) were also documented along all shores of the lake. Fish: Lake Kapowsin and adjacent Kapowsin and Ohop Creeks support a variety of cold and warm water fish species, including: Coho salmon (Oncorhynchus kisutch), Chinook salmon (Oncorhynchus tshawytscha), pink salmon (Oncorhynchus gorbuscha), steelhead (Oncorhynchus mykiss), bull trout (Salvelinus confluentus), and cutthroat trout (Oncorhynchus clarki), largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus) and numerous other warmwater fish species. Amphibians: Five amphibian species were identified at Lake Kapowsin during the March and April visual encounter surveys and included two native frog species (Pacific treefrog [Pseudacris regilla] and northern red-legged frog [Rana aurora aurora]); one non-native frog (American bullfrog [Lithobates catesbeianus]); and two native salamanders (northwestern salamander [Ambystoma gracile] and rough-skinned newt [Taricha granulosa]). The northern red- legged frog is listed as a federal species of concern. Additional survey efforts are recommended for verifying presence or absence of Oregon spotted frog (Rana pretiosa) and western toad (Bufo boreas). Mammals: A total of 51 mammals were predicted to occur within the Lake Kapowsin region by the 2004 Pierce County Biodiversity Network Assessment. The state and federal-listed mammal species predicted to occur in this region included the brush prairie pocket gopher (Thomomys mazama douglasii), fisher (Martes pennanti), long-eared myotis (Myotis septentrionalis), long-legged myotis (Myotis volans), Pacific water shrew (Sorex bendirii), Townsend’s big-eared bat (Corynorhinus townsendii), and Yuma myotis (Myotis yumanensis). This region had the third highest predicted mammal diversity of any of the mapped 17 biodiversity management areas in Pierce County. Beaver lodges and river otter scat were documented on the Lake. WDFW priority species documentations for the lake and adjacent habitats included state endangered, federally threatened grizzly bear (Ursus arctos), migratory elk (Cervus elaphus) and other species. Birds: A total of 116 avian species (or species groups) have been documented on Lake Kapowsin during Christmas bird counts, including numerous with federal and/or state conservation status: Bald Eagle (Haliaeetus leucocephalus), Peregrine Falcon (Falco peregrinus), Western Grebe (Aechmorphorus occidentalis), Pileated Woodpecker (Dryocopus pileatus), Purple Martin (Progne subis), Wood Duck (Aix sponsa), Osprey (Pandeon haliaetus), and Great Blue Heron (Ardea Herodias). When comparing the number of bird species detected at the lake itself during the summer and during the Christmas Bird Counts, the Lake Kapowsin area had 127 overall species compared to the predicted 113 species identified by the 2004 Pierce County Biodiversity Network Assessment for this region. The Lake Kapowsin area had the 2nd highest predicted number of bird species in the Biodiversity Network Assessment Region of Pierce County, out of the 17 biodiversity regions assessed. Potential Management Concerns Eutrophic Lake Conditions Several different measurements and observations at Lake Kapowsin indicate this is a mesotrophic to eutrophic lake system, with high nutrient inputs (woody detritus, aquatic vegetation) and shallow water depths as contributory factors. Eutrophic lakes have high nutrient levels, high plant production rates, and an abundance of plant life. They are naturally occurring and can be biologically diverse with abundant fish, plant and wildlife. Human activities, such as lakeshore development and poorly managed agriculture, however, can result in excessive nutrient concentrations, accelerated eutrophication and can cause undesirable effects such as nuisance algae, excessive plant growth, murky water, odor and fish kills. Water chemistry: Lake Kapowsin was mesotrophic in October 2014 and eutrophic in April 2015 based on chlorophyll-a concentration (algal productivity) and water clarity measurements. Based on total phosphorus concentrations in both October 2014 and April 2015, the lake would be considered eutrophic. Additional sampling during the summer growing season is recommended to better understand biological productivity in Lake Kapowsin. Macroinvertebrates: macroinvertebrate community composition suggests that Lake Kapowsin: 1) has relatively high organic nutrient concentrations and is dominated by a detrital- based food web; 2) water temperatures are warm; 3) water is mildly acidic; and 3) benthic substrates may be hypoxic. Algae blooms: several small algae blooms were identified in still water areas during June 2015. These blooms are likely filamentous green algae, which is not toxic to humans, but is indicative of high nutrients in the lake. Invasive Species Six Class C noxious weed species were documented on Lake Kapowsin, which included Himalayan blackberry (Rubus armeniacus), yellow flag iris (Iris pseudoacorus) most commonly, as well as evergreen blackberry (Rubus laciniatus), reed canary grass (Phalaris arundinacea), common St. Johnswort (Hypericum perforatum) and Canada thistle (Cirsium arvense) in small or isolated infestations. As Class C noxious weeds, these species are considered widespread and well established in Washington, so management is recommended but not required. A non-native aquatic mollusk, the Chinese mystery snail was documented and regularly observed throughout Lake Kapowsin. This snail, while very abundant at Lake Kapowsin, is considered to be a mostly benign species (non-invasive) where it has been studied in the Great Lakes region. American bullfrog (Lithobates catesbeianus or Rana catesbeiana) was commonly encountered on Lake Kapowsin. Exotic species such as bullfrogs, and nonnative, warmwater fish species act as aquatic predators and have played a role in losses of Oregon spotted frog and northern red- legged frog populations in the Pacific Northwest. Fishery Management Warmwater fish, especially largemouth bass (Micropterus salmoides) and rock bass (Ambloplites rupestris), provide a popular and apparently significant recreational sport fishery on Lake Kapowsin. This makes managing for successful juvenile coho lake and side-channel rearing, and outmigration of juvenile coho, steelhead, and possibly sea-run cutthroat trout and bull trout through the lake difficult. Warmwater fish predation on salmonid juveniles, particularly from largemouth bass, is potentially significant on the lake. The amount of predation on juvenile salmonids in Lake Kapowsin is not known, however, based on studies in other similar