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									  The Effects of Varying
Levels of Propeller Scarring
 on Seagrass Associated
           Fauna

           Megan Reese
      Advisor: Dr. Greg Stunz
Texas A&M University-Corpus Christi
What is Seagrass?



 • Valuable habitat
 • Highly productive
 • Important food
   source
 • Nutrient cycling
 • Stabilizes sediments
     Seagrass Species
• Halodule wrightii
• Thalassia testudinum
• Syringodium filiforme
• Ruppia maritima
• Halophila englemannii
                          Source: Phillips, R. C. and E. Meñez, 1988. Seagrasses,
                          Smithsonian Contributions to the Marine Sciences, No. 34.
                          http://www.botany.hawaii.edu/seagrass/spppages/spp_hawr.
                          htm
What’s the Problem?
Propeller Scars!!
    What Are Propeller Scars?

• Increased boating
  activity
• Propeller cuts through
  rhizosomal mat of
  seagrass
• Seagrass will not grow
  back for many years (If
  ever!)
• Causes habitat
  fragmentation
• Disrupts seagrass beds
Possible Solution

          • June 2000:
            Marine Protected
            Areas
          • Voluntary Prop-
            up Zones and No
            Motor Zones
Boater Compliance???
      ZERO!!!!
             Purpose
• Examine the impact of propeller
  scars on fish and decapod
  crustacean abundance
• Varying levels of scarring:
  – Severe scarring = Greater than
    15%
  – Moderate scarring = 5% - 15%
  – Light scarring = Less than 5%
  – Reference = NO scarring
     Levels of Scarring
            Modified from Sargent et al. 1995



Low: Less than 5%                    Moderate: 5%-15%




         Severe: Greater than 15%
          Objectives
• Identify 40 sites (10 per each
  treatment level)
• Complete the summer seasonal
  sampling for the fauna in each
  site
• Use ANOVA to examine
  differences in scarring levels
              Hypothesis:
  Varying intensity of propeller scarring may
  affect abundance of marine life

• Propeller scars
  influence:
  – increase the edge
  – decreases refuge
    value of
    seagrasses
  – alter habitat
  – affects some
    organisms more
    than others
Methods to our Madness
   Finding the Sites:
     •   By Plane
     •   By Boat
     •   By Foot
     •   By Touch
By Plane
By Boat
By Foot
By Touch
Site Location
       • Aransas Bay
       • 40 Sites
          – 10m x 25m
            quadrants
         – 10 Blocks
           Block 1

Severe: 18.70%
Moderate: 12.60%
Light: 1.06%
Reference: 0%
Sampling
     • Epibenthic Sled
       – quantitative
     • 10 m2
     • 2 simultaneous
       tows per site
     • Samples were
       bagged and
       stored on ice
Sorting
Results????
           Discussion


Problems:
•Weather
•Vast waters
•Time
           Conclusions

•Part of a large
study
•Sampling for
another year
•Examine growth
rate and mortality
rate
Acknowledgements
        •   Dr. Greg Stunz
        •   Dana Burfeind
        •   Amanda Bushon
        •   Paul Gonzales
        •   Ramiro Cervantes
        •   NSF Grant #0139195

								
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