Effects of environmental change on freshwater zooplankton
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Effects of environmental change on freshwater zooplankton. Dr. Sandra L. Cooke Thompson Writing Program & Biology Department Duke University Durham, North Carolina Download this file: http://www.duke.edu/~sc153/research.html. Aquatic Ecosystems & Environmental Change. climate change.

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Effects of environmental change on freshwater zooplankton

Dr. Sandra L. Cooke

Thompson Writing Program &

Biology Department

Duke University

Durham, North Carolina

Download this file: http://www.duke.edu/~sc153/research.html


Aquatic Ecosystems & Environmental Change

  • climate change

1

temperature

UV

  • land use change

CDOM

2

  • invasive species

3

Daphnia lumholtzi


UV in Aquatic Ecosystems

UV-B

UV-A

wavelength (nm)

  • biological damage  lethality

  • vision & behavior

  • pathogens

  • photochemistry

Photo by Dr. Patrick Neale


UV & Temperature

Photoenzymatic repair

warmer

more light, UV

cooler

darker, low UV


Diel Vertical Migration (DVM)


How does zooplankton DVM vary across UV and temperature gradients?

UV-sensitive species

UV-tolerant species

Daphnia catawba

Leptodiaptomusminutus


Field Site – Lake Giles

located in Poconos (northeastern PA)

very transparent => high UV levels


-UV treatment: 6 columns made of plastic that blocks UV

+UV treatment: 6 columns made of plastic that allows UV through

(all columns let visible light through)


Depth (m)

1

2

3

4

5

6

7

8

9

Ran a nighttime experiment (9 pm – 3 am)

Ran a daylight experiment (11:15 am – 4:30 pm)

10

11


UV-B

PAR

Cooke et al., 2008 CJFAS


Daphnia catawba

-UV

+UV

Cooke et al., 2008 CJFAS


Leptodiaptomus minutus

-UV

+UV

Cooke et al., 2008 CJFAS


Implications

  • UV may constrain some zooplankton species to sub-optimal temperatures, which may compromise fitness.

  • Climate change context – research suggest that in some lakes:

    • UV transparency may increase

    • Thermal gradients may steepen


Potential student-centered projects

Are warm-water zooplankton sensitive to UV?

Does temperature influence their UV-sensitivity?

Doable with minimal equipment!

Cooke et al., 2006 FWB


Potential student-centered projects

  • Do zooplankton use low oxygen zones as refugia from predation?

    • If so, which species?

    • If so, does body size matter?

    • How low can they go?

http://www.ncsu.edu/wq/RTRM/dp15/dp15cc.html


Potential student-centered projects

Doable for undergraduates


Aquatic Ecosystems & Environmental Change

  • climate change

1

temperature

UV

  • land use change

CDOM

2

  • invasive species

3

Daphnia lumholtzi


UV & CDOM

CDOM = Chromophoric Dissolved Organic Matter

Chromophoric – absorbs UV, short visible light

Dissolved – <0.7 μm

Organic – plant-derived, mostly terrestrial

Matter – “stuff” – mostly carbon (DOC), but also nutrients, ions, acids, etc.

Quantified as concentration of

dissolved organic carbon (DOC)


CDOM and Environmental Change

  • Temperature

  • Precipitation

  • Watershed land use

  • Biome/ climate shifts

Global trend of ↑CDOM


Potential Ecological Effects of Increased CDOM

  • UV attenuation ↑ (less UV)

  • DOC, DON, etc.  food web stimulation

  • pH(humic & fulvic acids)


How does ↑CDOM in a UV-transparent lake influence zooplankton?


Potential Effects of CDOM on Zooplankton

CDOM Effects

Leptodiaptomus minutus

Daphnia catawba

more UV-tolerant

less UV-tolerant

UV-attenuation

microbial food web-stimulation

acidic

benefits from ciliates, algae

benefits from bacteria, HNANs, ciliates, algae

less acid-tolerant

more acid-tolerant


Hypothesis

CDOM


- CDOM

+CDOM

Microcosm Experiment

2 weeks

-UV

+UV


Cooke et al., 2006 Hydrobiol.


Cooke et al., 2006 Hydrobiol.


Implications

  • CDOM may have “sunscreen” and pH effects

  • Non-irradiated CDOM may be harmful (photochemical interactions important)

  • CDOM could alter plankton community composition

NOTE: a longer-term, larger-scale experiment corroborates this and also points to

food-web effects


Potential student-centered projects

  • Effects of different CDOM sources on zooplankton

  • Positive effects of UV – does CDOM play a role?

Density (L-1)

Cooke & Williamson, 2006 JPR


Lacawac Sanctuary


Aquatic Ecosystems & Environmental Change

  • climate change

1

temperature

UV

  • land use change

CDOM

2

  • invasive species

3

Daphnia lumholtzi


North Carolina reservoirs

Image from http://www.americanrivers.org/


Daphnia lumholtzi

1 mm

D. lumholtzi distribution in U.S. – collected and established


Potential Ecological Effects of D. lumholtzi

  • May be more tolerant of mid-late summer conditions (tends to thrive in large rivers and reservoirs, temps ~30 C) compared to natives.

  • May be more resistant to predation compared to natives.

larval & juvenile fish

macroinvertebrates

1 mm

1 mm

Largemouth bass image: George Burgess; http://www.flmnh.ufl.edu/fish/gallery/Descript/LargemouthBass/LargemouthBass.html


Objectives

Determine foraging efficiencies of juvenile fishes on D. lumholtzi vs. native Daphnia.

Monitor the seasonal abundance and spatial distribution of D. lumholtzi and other zooplankton throughout Falls Lake.

Determine if D. lumholtzi is present in B. Everett Jordan Lake (and monitor its seasonal abundance if it is)

Falls

~15-20 mi.

Jordan


  • Found D. lumholtziin Jordan Lake:

  • Farrington Point

  • Vista Point

  • New Hope Overlook

Project for my aquatic invasive species class: Monitor D. lumholtzi abundance and dominance (% of total zooplankton) at Farrington Point over the fall and spring semesters


WordPress blog was helpful…


Image from http://www.aslo.org/photopost/showphoto.php/photo/163/title/leptodora-kindii/cat/518

Finn et al., in press, JNCAS

(5 student co-authors!)


Potential student-centered projects

Objective 1: Determine foraging efficiencies of juvenile fishes on D. lumholtzi vs. native Daphnia.

juvenile black crappie

Cooke & Johnsen, 2011 NCWRC tech. report


Potential student-centered projects

Objective 2: Monitor the seasonal abundance and spatial distribution of D. lumholtzi and other zooplankton throughout Falls Lake.

4 sites visited at least 1x/month Jun. 09 – Feb. 12

6 additional sites ~1x/month Jun. 09 – Dec. 11


Potential student-centered projects

Are spatial and temporal trends correlated with algal dynamics (e.g., cyanobacteria) or other parameters (e.g., temperature, turbidity) in Falls Lake?

Cooke & Johnsen, 2011 NCWRC tech. report


Potential student-centered projects

Zooplankton monitoring in Oak Hollow Lake and City Lake

Algal-nutrient dynamics are important…so are algal-grazer dynamics!

Cooke & Johnsen, 2011 NCWRC tech. report


Potential student-centered projects

Daphnia lumholtzi distribution across NC and southeastern U.S.


Acknowledgments

  • My colleagues and collaborators, especially:

    • Dr. JoAnn Burkholder & Dr. Robert Reed at the CAAE at NCSU

    • Dr. SonkeJohnsen and lab group in the Biol. Dept. at Duke

    • Dr. Craig Williamson at Miami University

  • My students, especially:

    • Caitlin Finn, Ming Leung, Hannah Naughton, Xiangyu Wang, Andre May

    • Cole Arora

  • Funding from:

    • NC Wildlife Resources Commission

    • NSF (DEB program)

    • The Duke Endowment (Duke University)

    • Paletz Innovative Teaching Fund (Duke University)

    • Thompson Writing Program (Duke University)

Thanks for your attention!


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