Assessment of Propeller Scarring in Seagrass Beds of the South Texas Coast

Distribution and intensity of scarring in approximately 5,700 ha of seagrass beds were quantified using high resolution (1:2,400) aerial photography taken in January 1997 in the Corpus Christi Bay National Estuary Program (CCBNEP) study area along the south Texas coast. Scarring levels were defined...

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Bibliographic Details
Published in:Journal of coastal research 2002-10, p.100-110
Main Authors: Dunton, Kenneth H., Schonberg, Susan V.
Format: Article
Language:English
Subjects:
Aerial photography
Boats
Coasts
Estuaries
Flood damage
Geographic regions
Habitat conservation
Polygons
Propellers
Scars
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Summary:Distribution and intensity of scarring in approximately 5,700 ha of seagrass beds were quantified using high resolution (1:2,400) aerial photography taken in January 1997 in the Corpus Christi Bay National Estuary Program (CCBNEP) study area along the south Texas coast. Scarring levels were defined as light (20%) based on the percentage of area covered by propeller scars within each of eight distinct regions. Surveys by boat and aircraft were used to verify aerial photography and collect Differential Global Positioning System (DGPS) coordinates for rectification and registration procedures. Distribution and levels of scarring were digitally transferred onto USGS topographical charts and analyzed using Geographic Information System (GIS) techniques. Within the survey area, 2,200 ha (39%) of seagrass meadows were identified as either moderately or severely scarred. Scarring of grassbeds was greatest in Estes Flats, where over 97% of the grassbed was scarred, with 75% rated as severe. Moderate and severe scarring was also prevalent in the East Flats (49%), Shamrock Island (35%), and Redfish Bay (23%) regions. Propeller scarring of seagrasses by boating activity is caused by misjudgment of water depth or channel location, taking shortcuts across shallow flats, maintenance of channels through grassbeds using illegal navigational aids, and ignorance with respect to the damage caused by propellers. Management priorities should focus on public education and the marking of secondary channels to minimize damage to adjacent grassbeds. Future research efforts should be directed toward understanding the long-term effects of seagrass scarring in an effort to develop local management strategies to minimize continued damage to this valuable resource.
ISSN:0749-0208
1551-5036