Resilience of Soft-Sediment Communities after Geoduck Harvest in - PowerPoint PPT Presentation

Resilience of Soft-Sediment Communities after Geoduck Harvest in Samish Bay, Washington Micah Horwith, Department of Biology, University of Washington

Fisk Bar

Fisk Bar = Eelgrass = Bare = Channel

Timeline 1 - Pre-harvest Geoduck crop Geoduck crop planted harvested Eelgrass colonizes Fisk Bar farm Summer May ??? 2002 2008

Timeline 1 - Pre-harvest 2 - Post-harvest

Geoduck harvest May 2008

Tube installation June 2008 7

Net installation July 2008

How does geoduck farming affect eelgrass?

How does geoduck farming affect eelgrass? 1 - Reduced size

How does geoduck farming affect eelgrass? 1 - Reduced size Harvest 25 Unfarmed Farmed 20 Mean sheath length (cm ± SE) 15 Mean sheath length (cm ± SE) 10 5 0 4/9/08 6/30/08 7/29/08 11/12/08 4/26/09 7/18/09 11/4/09 4/30/10

How does geoduck farming affect eelgrass? 1 - Reduced size Harvest Unfarmed Farmed 25 Unfarmed Farmed 20 Mean sheath length (cm ± SE) 15 April 2008 10 5 0 4/9/08 6/30/08 7/29/08 11/12/08 4/26/09 7/18/09 11/4/09 4/30/10

How does geoduck farming affect eelgrass? 1 - Reduced size Harvest Unfarmed Farmed 25 Unfarmed Farmed 20 Mean sheath length (cm ± SE) 15 April 2008 10 5 0 4/9/08 6/30/08 7/29/08 11/12/08 4/26/09 7/18/09 11/4/09 4/30/10 April 2009

How does geoduck farming affect eelgrass? 1 - Reduced size 2 - Reduced reproductive activity

How does geoduck farming affect eelgrass? 1 - Reduced size 2 - Reduced reproductive activity Frequency of # of branches April 2008 Unfarmed Farmed

How does geoduck farming affect eelgrass? 1 - Reduced size 2 - Reduced reproductive activity Frequency of # of branches April 2008 April 2009 Unfarmed Farmed

How does geoduck farming affect eelgrass? 1 - Reduced size 2 - Reduced reproductive activity 3 - Decline and loss

How does geoduck farming affect eelgrass? 1 - Reduced size Harvest 2 - Reduced reproductive activity 3 - Decline and loss 500 Unfarmed Farmed 400 Mean shoot density (per m^2) 300 Mean eelgrass density (shoots m -2 ± SE) 200 100 0 4/9/08 6/30/08 7/29/08 11/12/08 4/26/09 7/18/09 11/4/09 4/30/10

How does geoduck farming affect sediment?

How does geoduck farming affect sediment? 1 - Reduced sediment organic content

How does geoduck farming affect sediment? 1 - Reduced sediment organic content Harvest 2.5 Unfarmed Farmed 2.0 Mean sediment organic content (% ± SE) 1.5 Mean sediment organic content (% ± SE) 1.0 0.5 0.0 4/9/08 6/30/08 7/29/08 11/12/08 4/26/09 7/18/09 11/4/09 4/30/10

How does geoduck farming affect sediment? 1 - Reduced sediment organic content 2 - Elevation loss and recovery

How does geoduck farming affect sediment? 1 - Reduced sediment organic content 2 - Elevation loss and recovery 2 Unfarmed Farmed 1 Mean Point ! Elevation (cm ± SE) Mean Point 0 ∆ Elevation (cm ± SE) -1 -2 6/4/08 6/25/08 7/29/08 11/12/08 4/26/09

Does geoduck farming have ‘spillover’ effects?

Does geoduck farming have ‘spillover’ effects? 1 - Reduced eelgrass size near farm

Does geoduck farming have ‘spillover’ effects? 1 - Reduced eelgrass size near farm Rsquared = 0.132 F1,23 = 3.484 p =0.075 18 16 4/9/08 Mean sheath length (cm) 6/30/08 7/29/08 11/12/08 14 4/26/09 7/18/09 11/4/09 12 4/30/10 10 0 20 40 60 80 Distance from farm (m)

Does geoduck farming have ‘spillover’ effects? 1 - Reduced eelgrass size near farm 2 - Increased eelgrass density near farm

Does geoduck farming have ‘spillover’ effects? 1 - Reduced eelgrass size near farm 2 - Increased eelgrass density near farm Rsquared = 0.23 F1,23 = 6.882 p = 0.015 500 4/9/08 400 6/30/08 Shoots per m^2 7/29/08 11/12/08 300 4/26/09 7/18/09 11/4/09 4/30/10 200 100 0 20 40 60 80 Distance from farm (m)

Does geoduck farming have ‘spillover’ effects? 1 - Reduced eelgrass size near farm 2 - Increased eelgrass density near farm 3 - Possible increased sediment organic content, reduced standing biomass near farm

Does geoduck farming have ‘spillover’ effects? 1 - Reduced eelgrass size near farm 2 - Increased eelgrass density near farm 3 - Possible increased sediment organic content, reduced standing biomass near farm Sediment organic content Standing biomass 4/9/08 0.4 6/30/08 Dry eelgrass biomass (g per m^2) 7/29/08 0.3 11/12/08 4/26/09 0.2 7/18/09 11/4/09 0.1 4/30/10 0 20 40 60 80 Distance from farm (m)

How do predator-exclosure tubes affect eelgrass?

How do predator-exclosure tubes affect eelgrass? 1 - Reduced eelgrass seedling success

How do predator-exclosure tubes affect eelgrass? 1 - Reduced eelgrass seedling success 1.0 Tubes No Tubes 0.8 Proportion of surviving seedlings 0.6 Proportion of surviving seedlings 0.4 0.2 0.0 5/22/09 5/28/09 6/23/09 8/18/09

How do predator-exclosure tubes affect eelgrass? 1 - Reduced eelgrass seedling success 2 - No effect on sediment organic content

How do predator-exclosure tubes affect eelgrass? 1 - Reduced eelgrass seedling success 2 - No effect on sediment organic content 1.5 Tubes No Tubes 1.0 ! Sediment organic content (% ± SE) 0.5 ∆ Sediment organic 0.0 content (% ± SE) -0.5 -1.0 -1.5

How do predator-exclosure tubes affect eelgrass? 1 - Reduced eelgrass seedling success 2 - No effect on sediment organic content 3 - No effect on sediment stability

How do predator-exclosure tubes affect eelgrass? 1 - Reduced eelgrass seedling success 2 - No effect on sediment organic content 3 - No effect on sediment stability 40 Tubes No Tubes 20 Cumulative ! Elevation (cm ± SE) Cumulative ∆ Elevation 0 (cm ± SE) -20 -40

Geoduck farming effects to date

Geoduck farming effects to date Within farm • Loss of eelgrass • Reduced size and reproductive activity prior to loss • Reduced sediment organic content • Short-term loss of elevation

Geoduck farming effects to date Within farm Spillover • Loss of eelgrass • Reduced eelgrass size • Reduced size and reproductive activity prior to loss • Increased eelgrass density • Reduced sediment organic content • Possible increase in sediment • Short-term loss of elevation organic content and decrease in standing biomass

Support Field Assistance Julianna Chen Julie Nicol Katie Cochrane Dr. Fernanda Oyarzun Audrey Djunaedi Emily Palm Giorgio Guerra Adam Parast Caleb Hecker Sascha Troiano Kelsey Hinton Chaochung Tsai Isaac Horwith Chaowei Tsai Henry Howes Dr. Ursula Valdez Sarah Jubinski Brady Walkinshaw Ailene Kane Kyle Wataya Satprit Kaur Inness Wragg Max Maliska Sylvia Yang Claire Miccio Dr. Jae-Won Yoo Gia Nguyen Guidance Dr. Janneke Hille Ris Lambers Dr. Jennifer Ruesink