HABITAT COMPLEXITY AND EDGES ON SEAGRASS EPIFAUNAL COMMUNITIES RELATIVE INFLUENCE OF HABITAT COMPLEXITY AND EDGES ON SEAGRASS EPIFAUNAL COMMUNITIES Eliza C. Moore1 and Kevin A. Hovel Department of Biology San Diego State University 1moore.eliza@gmail.com Photo credit: www.southeastmarine.org.uk

Outline Intro to seagrass habitat Covariation in structure Survey Caging experiment Conclusions

Seagrasses Soft sediment-bays and estuaries Form extensive meadows Nursery habitat Threatened Restoration efforts Photo credits: Google images 2006, www.oceanservice.noaa.gov, www.ucsb.piscoweb.org, www.ncsu.edu

Attributes of habitat structure 50 m Aerial view of seagrass beds Landscape scale – Habitat amount – Patch connectivity – Amount of edge Patch scale (Complexity) Shoot density Shoot length Surface area Biomass Photo Credit: southeastmarine.org.uk, Kevin Hovel

Sparse, short shoots at patch edge Covariation Low patch-scale complexity at edge Research goal – Relative importance Edge vs. shoot density Sparse, short shoots at patch edge

Study sites in San Diego Bay Zostera marina Water residence times Image: Port of San Diego 2000 Shelter Island North Central Bay South Central Bay N 32.70 1 Km W 117.17

Location p < 0.001 Sampling Period p < 0.001 Shoot density Location p < 0.001 Sampling Period p < 0.001 June August n = 8 SI Hotel Bridge SI Hotel Bridge 7

Fauna of eelgrass beds Epifauna (prey) Predator fishes > 500 µm Predator fishes Individuals identified and counted Epifauna variable throughout the bed Patterns inconsistent Consistent within particular species 1 mm 2 mm 1 mm 2 mm 1 mm 1 mm

Epifaunal NMDS Low clustering by “Location” June August

Epifaunal NMDS Low clustering by “Location” June August Shelter Island – Front Bay

Outline Intro to seagrass habitat Covariation in structure Survey results Shoot density low at edge Epifauna variable through bed Caging experiment Conclusions

Caging experiment – Shelter Island Research question What are the relative influences of: -Shoot density (Complexity) -Bed location -Predation on epifaunal distribution? Caging experiment – Shelter Island

Caging experiment Factors Complexity Location Predation Dense Edge Cage Sparse Interior Cage Control Open 600 shoots/m2 150 shoots/m2

Caging experiment Factors Complexity Location Predation Dense Edge Cage Sparse Interior Cage Control Open 5 m 1 m

Caging experiment Mesh size = 6 mm Factors Complexity Location Predation Dense Edge Cage Sparse Interior Cage Control Open Mesh size = 6 mm 0.71 m

Results and analysis n = 5, 42 taxa identified Total abundance and diversity Individual taxa ω2 – relative importance of each factor Taxon % Gammarid Amphipods 73% Copepods 6% Alia spp. Hippolyte spp. 5% 0.5 mm 2 mm

Relative influence Variability explained (ω2) Location Complexity Predation Total abundance 36% 22% -- Diversity 33% Alia spp. 25% 9% Hippolyte spp. 16% 49% Caprellidae 67% Copepods 12% 0.5 mm 2 mm 1 mm 0.5 mm

Conclusions Community measures (total abundance, diversity) largely influenced by bed location Patch scale complexity and predation relatively important for particular taxa Multiple scales of structure important Implications for management/restoration Plenty of habitat, variable shoot densities and patch sizes

Acknowledgements Faculty & Staff The Hovel Lab Undergraduate assistants The Hovel Lab SDSU Biology Graduate Students C. Gramlich L. Thurn J. Zimmer B. Cheng J. Coates R. Jenkinson C. Loflen K. Nichols J. Selgrath K. Tait K.Withy-Allen M. Castorani R. Lannin L. Caruso A. Chargin C. Christie S. Goldstein B. Hembrough K. Palaoro T. Pantels M. Potter T. Riccio G.York N. Dodge S. Fejtek R. Mothokakobo L. Lewis L. Komoroske H. Carson

Thank you Port of San Diego!

Locations of transects Field surveys Core samples – June and August 2007 Shore Seagrass bed 6+ m INTERIOR 5 m Locations of transects INNER EDGE 1 m OUTER EDGE Bay (Not to scale)

Epifaunal abundance Location p < 0.001 Site p < 0.001 Sampling Period p = 0.007 June August n = 8 SI Hotel Bridge SI Hotel Bridge

Field surveys - Fishes Beam trawl Shore Seagrass bed Bay INTERIOR EDGE Bay

Fish distribution n = 3 June 2007 Front Bay Mid Bay

Total epifaunal abundance location p < 0.001 ω2 – 36% complexity p < 0.001 ω2 – 22% Edge Interior Complexity

Diversity – Simpson’s Index – 42 taxa location p < 0.001 ω2 – 33% Edge Interior Simpson’s Index of Diversity Complexity

Copepods complexity p = 0.002 ω2 – 12% Copepods per ASU Complexity 1 mm 0.5 mm complexity p = 0.002 ω2 – 12% Edge Interior Copepods per ASU Complexity

Alia spp. complexity p < 0.001 ω2 – 25% predation p = 0.011 ω2 – 9% Edge Interior Snails per ASU Complexity

Hippolyte spp. predation p < 0.001 ω2 – 49% complexity p < 0.001 ω2 – 16% 2 mm Edge Interior Shrimp per ASU Dense Sparse Dense Sparse Complexity

Caprellid amphipods location p < 0.001 ω2 – 67% Caprellids per ASU 2 mm location p < 0.001 ω2 – 67% Edge Interior Caprellids per ASU Complexity Photo: www.beachwatchers.wsu.edu

Prey Biomass complexity p < 0.001 ω2 – 26% predation p < 0.001 ω2 – 27% Edge Interior Dry weight (g) Complexity