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The Effect of the Invasive
Species Caulerpa
taxifolia among Native
Species
Lena Collins
IROP 2007
Wollongong, Australia
Sydney Opera
me
House
Wollongong, Australia
http://www.tourismwollongong.com/regions/wollongong_map.asp
Study Site: St. George’s Basin
Species of Interest
Anadara trapezia
Caulerpa taxifolia
Invasive Species
• One the of largest
environmental crises
that we face today
• Exotic species are
considered the
second greatest threat
to imperiled species in
the United States
http://images.wri.org/photo_invasivespecies_print.jpg
http://www.samab.org/Focus/Invasive/1PhotoGallery/photos.html
Before …
After …
C.tax in St. George’s Basin
http://www.fisheries.nsw.gov.au/threatened_species/general/species/caulerpa_st_georges_basin_aug_5
Research Objectives:
1. Clam Recovery Experiment
- C.taxifolia effect on predation
- C.taxifolia effect on clam metrics
2. Parasite Study
- Habitat effect on parasite damage
- Habitat effect on clam metrics
Part I: Clam Recovery
Experiment
Predators:
Octopus
Blue Swimming Crab
Experimental Design:
Habitat: Caulerpa taxifolia
Habitat: bare sediment
Results:
22/240 clams missing
14 of 22 in closed cages
• Significant effect of vegetation
(p=0.0071)
• Artifact of collection
• Not the right season for predation
study
Results Continued:
• Examine treatment effects on growth
• No significant changes in length or
mass detected
• Bare and open treatment trended
toward better growth
• Evidence that cages may act like
C.taxifolia but the effect is not additive
Average Change
in Mass (g)
Average Change in Dry Mass of
Anadara trapezia
0.20
0.15
0.10
0.05
0.00
-0.05
-0.10
-0.15
-0.20
-0.25
-0.30
-0.35
bare open
bare closed
c.tax open
c.tax closed
Australia … ahhh
Part II: Parasite Study
Dipolydora spp.1
Network
Spot
Borehole
Blister
Habitat
Clam Metrics
•Habitat significantly affected
all clam metrics
•Overall best growth occurs in
unvegetated habitat
Average Length of A. trapezia
in Different Habitats
Length (mm)
54
52
50
48
46
44
42
C.taxifolia
Halophila
Habitat
Bare
Average Dry Tissue Weight of
A. trapezia in Different Habitats
2
Weight (g)
1.6
1.2
0.8
0.4
0
C.taxifolia
Halophila
Habitat
Bare
Habitat
Parasites
• Controlled for clam metrics in this
analysis
• For most part, habitat did not affect
variables
• Interaction did play a role in
» Network Damage
» Borehole Damage
Network Damage
Transformed % Shell
Damage
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
Unveg
Halophila
Habitat
C.tax
Conclusions:
• No mortality data significant, summer
study may result in more insightful findings
• Trend that cages are acting like
C.taxifolia
• Habitat significantly affects clam metrics
• Habitat has minimal impact on parasites
• Some evidence that network parasite is
more prevalent in C.taxifolia
Finally …
• C. taxifolia is still at
large … more
questions unfold
• Hard it is to unravel
the mysterious of
nature
• Importance of
wonder in our world
CHEERS!
• Dr. James E.
Byers!!
• Dr. Jeffery Wright
• Anna, Darcy, and
Finn
• Collins family
• Mark, my lifeline