Lake Marianne Denton, Sudeep Chandra, Marion E. Wittmann, John - - PowerPoint PPT Presentation

Reproduction and Population Structure of Corbicula fluminea in an Oligotrophic Subalpine Lake

Marianne Denton, Sudeep Chandra, Marion E. Wittmann, John Reuter and Jeffrey G. Baguley Tahoe Science Consortium 23 May 2012

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Outline

• C. fluminea Reproduction
• 2009 Preliminary Study
• 2010 Complete Study

– Locations – Food Availability – Temperature – Reproductive Effort – Population Structure

• Results & Conclusions

– Thougths About Temperature

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How Does C. fluminea Reproduce?

Illustrations modified from Invertebrate Anatomy OnLine. Richard Fox, Lander University.

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Simultaneously hermaphaditic producing gametes (eggs & sperm) in the gonads. Gametes (eggs & sperm) move into the demibranches (gills). Sperm is released into the water column and either self-fertilizes or fertilizes a close neighbor. Egg fertilized in the demibranches. Developing juveniles are brooded in the marsupial gills.

Illustrations modified from Invertebrate Anatomy OnLine. Richard Fox, Lander University.

How Does C. fluminea Reproduce?

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Adult, simultaneous hermaphroditic Asian Clam.

6 to 14 Day Developmental Cycle

Black and White images from Kraemer, L.R. and M.L. Galloway, 1986.

Ovum with jelly coating embedded with sperm Fertilized egg Blastula 24 hours Gastrula 12 – 24 hours Trochophore 24 – 48 hours Trochophore 24 – 48 hours Veliger 24 – 48 hours Pediveliger 24 – 96 hours Straight-Hinged Juvenile

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Gills are a Great Place!

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2009: Marla Bay

Egg Veliger

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2009: Nevada Beach

Egg Veliger

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(Tahoe Environmental Research Center)

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Summer 2010 on Lake Tahoe

Lakeside 5 m Marla Bay 5 m Nevada Beach 5 m Nevada Beach 20 m

Map courtesy of Dave Rios, 2011

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2010 Study Design

Temperature would have the greatest influence on the timing of reproduction In situ temperature at each site (°C) Food availability would influence overall reproductive effort

• Total Organic Carbon (mg/L)
• Sediment Particulate Organic

Matter (g/mg) Reproductive efforts would be similar in both shallow and deeper populations resulting in a source of veligers for populating the nearshore environment Reproductive Effort

• Number of Eggs
• Number of Veligers

Population Structure

• Mean Abundance (#clams/m2)

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Bivoltine Reproduction

1st Spawn 2nd Spawn Increase in Temperature Suppresses Spawning Juveniles Spawned in the Spring are Reproductive Adults by Fall

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It’s Warm Enough for C. fluminea to Reproduce

0.0 5.0 10.0 15.0 20.0 25.0 11-May 29-May 16-Jun 28-Jun 7-Jul 20-Jul 2-Aug 16-Aug 30-Aug 13-Sep 8-Oct 5-Nov Temperature (°C) Date 2010 LS 5m MB 5m NVB 5m NVB 20m Release of Juveniles (16-18°C) Fertilization (14-15°C) Spermatogenesis (10°C)

Food Availability is Important for Reproduction

Reid et al, 1992. Rajagopal et al, 2000.

15 30 45 60 20 40 60 80 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Chlorophyll-a (g/l) Spawning Animals (%) 1992

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8 10 12 11-May 29-May 16-Jun 28-Jun 7-Jul 20-Jul 2-Aug 16-Aug 30-Aug 13-Sep 8-Oct 5-Nov TOC (mg/L) Date 2010 LS 5m MB 5m NVB 5m NVB 20m

Food Availability : Total Organic Carbon

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Food Availability: Sediment Particulate Organic Matter

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Veligers Dark Bars Eggs Light Bars

Reproductive Effort

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Others Studies Show Populations Have a Lot of Juveniles

Hall, 1984.

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Lakeside 5 m 1252144 Marla Bay 5 m 1664202 Nevada Beach 5 m 1689162 Nevada Beach 20 m 2541291

Abundance Number of Clams/m2

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What’s Going on with Nevada Beach 20 m?

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Dispersal via Floatation

Prezant and Chalermwat, 1984

Foot Siphons Mucus Thread Stained with Carbon

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Physical Action within Tahoe

Wittmann et al. 2011

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How are Tahoe’s C. fluminea different?

Aldridge and McMahon. 1978. Doherty, et al. 1987.

• 588 (Spring) and 735 (Fall) per clam per

day

• Annual high of 1,800 (late June) to 1200

(early October) per clam per day

• 102 (n=603)
• 28628 (4% with 100)
• 202 (12% with <100)
• 498 had no veligers (84%)

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Results & Conclusions

• Hypothesis: Temperature would influence reproductive timing

– Univoltine beginning in mid-August – Delay in spawn

• Hypothesis: Locations with greater food availability would have an increased

reproductive effort – Sediment particulate organic matter was greater at Lakeside, this did not influence overall reproductive effort – Total organic carbon was not different between sites

• Hypothesis: Deeper water population would have similar reproductive effort

as shallow populations – No reproductive effort – High abundances

• Population structure shows a strong adult population with a minimal juvenile

population indicating that deeper water populations are likely a sink population rather than a source

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Acknowledgments

Funding SNPLMA Science funding via the USDA PSW Research Station Nevada License Plate Funds from the Nevada Division of State Lands Aquatic Ecosystems Analysis Laboratory, University of Nevada, Reno Annie Caires Joe Sullivan John Umek Robert Barnes Jessica Rassmussen Alex Denton Christine Ngai Tahoe Environmental Research Center, UCDavis Geoff Schaldow Katie Webb Raph Townsend Steve Sesma California Fish and Game Jim Moore, Bodega Marine Laboratory, UCDavis Tahoe-Baikal Institute SEE 2009 Asian Clam Project Group

Questions?

Marianne Denton mariannedenton@sbcglobal.net