1. 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
Photo credit:

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

3. Seagrasses Soft sediment-bays and estuaries Form extensive meadows
Nursery habitat
Threatened
Restoration efforts
Photo credits: Google images 2006,

4. 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

5. 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

6. 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

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

8. 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

9. Epifaunal NMDS
Low clustering by “Location”
June August

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

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

12. 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

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

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

15. 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

16. 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

17. 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

18. 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

19. 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

20. Thank you Port of San Diego!

22. 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)

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

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

25. Fish distribution
n = 3 June 2007
Front Bay
Mid Bay

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

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

28. 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

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

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

31. 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:

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