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Dreissena veligers in western Lake Superior -- inference from new low-density detection
Citation:
Trebitz, A., C. Hatzenbuhler, J. Hoffman, C. Meredith, Greg Peterson, E. Pilgrim, J. Barge, A. Cotter, AND M. Wick. Dreissena veligers in western Lake Superior -- inference from new low-density detection. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, 45(3):691-699, (2019). https://doi.org/10.1016/j.jglr.2019.03.013
Impact/Purpose:
This survey is the first to report consistent detection of planktonic Dreissena mussel veligers in Lake Superior waters, and will hopefully motivate additional efforts to understand their prevalence and distribution. The early-detection monitoring survey described in this paper was motivated by a request for help from the National Park Service (NPS) in understanding the distribution and potential impacts of dreissenid (zebra and quagga) mussels in waters surrounding the Apostle Island National Lakeshore. This work falls under SSWR research area 3.01A-2.1, and builds on previous EPA/ORD case studies concerning early-detection monitoring strategies aimed at developing more refined and robust sampling strategies for non-native species in different coastal systems across the Great Lakes.
Description:
The notion that Lake Superior is inhospitable to Dreissenid (either zebra, Dreissena polymorpha or quagga, Dreissena bugensis) mussel survival seems to have been repudiated by recent finds on shipwrecks, commercial fishing gear, and rocky reefs in the Apostle Islands (APIS) National Lakeshore region. Motivated by concerns surrounding these finds, we conducted an intensive sampling campaign of APIS coastal waters in 2017, aimed at understanding Dreissena prevalence and distribution and providing baseline data for potential impacts on native zooplankton and benthic invertebrate communities. The 100-site effort combined random and targeted sites (e.g., dock and mooring areas), at which we collected zooplankton, benthic macroinvertebrates, video footage, and supporting environmental data. We did not find settled Dreissena in any benthos samples or videos. Dreissena veligers were found in almost half the zooplankton samples but at orders-of-magnitude lower densities than reported from other Laurentian Great Lakes. Veliger were most prevalent in western APIS, and sites with veligers had shallower depths and slightly higher phosphorus and chlorophyll concentrations than sites without veligers, but locations with veligers did not spatially match known (and still very localized) settled Dreissena colonies. This is the first study to report consistent detection of veligers from western Lake Superior waters, but also the first to conduct veliger-targeted sampling there. We lack information to establish whether the APIS veligers are locally spawned and thus a new component of the zooplankton community, or are transported from an established population in the St. Louis River estuary (~100 km to the west) by longshore currents and thus reflect low-density propagule pressure that may have been present for years. Small-mesh zooplankton data collected along a gradient from APIS to the St. Louis River estuary and enumerated with thorough veliger searching would help elucidate these alternatives.
URLs/Downloads:
DOI: Dreissena veligers in western Lake Superior -- inference from new low-density detection