Spatial and seasonal dynamics of nonindigenous Daphnia lumholtzi and other crustacean zooplankton in Falls Lake (central North Carolina)

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1 Spatial and seasonal dynamics of nonindigenous Daphnia lumholtzi and other crustacean zooplankton in Falls Lake (central North Carolina) Sandra L. Cooke Postdoctoral Fellow Duke University Durham, NC

2 Zooplankton in Falls Lake Has not been monitored recently or regularly Why study zooplankton dynamics?

3 Zooplankton in Falls Lake Why study zooplankton dynamics? interested in effects of climate change interested in effects of drought

4 Objectives To determine macrozooplankton species composition in Falls Lake To determine how zooplankton community varies across seasons and sites To determine if these differences correlate to changes in the algal community

5 Methods sampled crustacean zooplankton via whole-water column net tows (48 m)

6 Methods 3 sites visited at least 1x/month Jun 9 - Feb 1 6 additional sites ~1x/month Jun 9 - Oct 9 FL4 FL5 FL6 FL3 5 FL2 FL1 LBC INT

7 Results Observed the nonindigenous water flea Daphnia lumholtzi Native to tropical regions of Australia, Asia, and Africa Accidentally introduced to a Texas reservoir in 1991 Found in a reservoir in western N.C. in 1996 Found in Falls Lake in 1993 (not documented) Tends to thrive in large rivers and reservoirs, high temperatures (3 C)

8 collected and established

9 Potential Ecological Effects of May be more resistant to predation vertebrate invertebrate Largemouth bass image: George Burgess;

10 Potential Ecological Effects of May be more tolerant of mid-late summer conditions in reservoirs Pattinson et al. 23 Soeken-Gittenger et al. 29

11 across sites and seasons density (m -3 ) FL4 FL5 FL6 HWY5 FL2 FL3 FL1 LBC INTAKE 5/17/29 7/6/29 8/25/29 1/14/29 12/3/29 1/22/21

12 vary with transparency? summer autumn summer autumn density (m -3 ) 15 1 density (m -3 ) Secchi depth (m) attenuation length at 55 nm (cm)

13 More Results open water sites dominated by cyclopoid 4 Hwy 5 4 Intake May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9 22-Jan-1 17-May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9 22-Jan-1

14 More Results shallower, nearshore sites dominated by 1 FL May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9

15 More Results Shallow, turbid, upstream sites tended to have more zooplankton 1 FL May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9 1 FL FL FL May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec FL4 17-May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9 FL May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9 17-May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9 LBC May-9 6-Jul-9 25-Aug-914-Oct-9 3-Dec-9 22-Jan-1 17-May-9 6-Jul-9 25-Aug-9 14-Oct-9 3-Dec-9

16 Future Work Do juvenile fishes feed less efficiently on? Largemouth bass image: George Burgess;

17 Future Work Is presence and abundance significantly related to transparency/ turbidity/ light levels in Falls Lake? If so, is this due to: Food quality (e.g., Wang et al. 29) Interference w/ foraging (e.g., Shulze et al. 26) Predation pressure Avoiding visual feeders (planktivorous fishes) Suspended solids interfere w/ foraging by tactile invertebrate predators (Chaoborus)

18 Acknowledgements Dr. JoAnn Burkholder, Dr. Robert Reed, Eric Morris, other NCSU CAAE colleagues Dr. Sonke Johnsen and lab group Funding Thompson Writing Program NC Wildlife Resources Commission Thanks for your attention!