Accession Number : ADA308367

Title :   Delayed Recovery of Seagrass Beds Along Navigable Waterways: Interaction Between Disturbance and Nuisance Algae.

Descriptive Note : Final progress rept.,

Corporate Author : PUERTO RICO UNIV MAYAGUEZ DEPT OF MARINE SCIENCES

Personal Author(s) : Holmquist, Jeff G.

PDF Url : ADA308367

Report Date : 02 MAY 1996

Pagination or Media Count : 47

Abstract : In coastal systems, patches of seagrass are frequently destroyed by propeller scarring and anchor damage near waterways, resulting in denuded 'blowouts'. Persistence of blowouts is a poorly understood phenomenon, and I proposed that (1) benthic 'drift' algae (marine analogs of terrestrial tumbleweeds) settle in blowouts and protract recovery of seagrass by shading the affected patches, and (2) that algal masses may be more easily trapped in small blowouts than in large blowouts. I tested this hypothesis with a series of field manipulations. Algal cover was much higher on disturbed plots than on controls, and there was also greater algal accumulation associated with small disturbances than with larger gaps. Algal accumulation slowed recovery of seagrasses as gauged by seagrass cover and density of seagrass shoots but caused little effect on recovery rates for standing crop, leaf area index, or canopy height. A greater intensity of disturbance fell upon the smaller plots, but recovery on these gaps was equal to or greater than exhibited by the large gaps, probably due to the small amount of vegetative recovery required to seal small gaps. There is thus evidence that large ambient populations of nuisance macroalgae can slow recovery of anthropogenously-disturbed vegetation along waterways.

Descriptors :   *PLANT GROWTH, *VEGETATION, *INVERTEBRATES, *SEA WATER, *WATERWAYS, *AQUATIC ANIMALS, *GRASSES, *AQUATIC PLANTS, RECOVERY, COASTAL REGIONS, DAMAGE, INTENSITY, RATES, POPULATION, DRIFT, NAVIGATION, CANOPIES, ANALOGS, INDEXES, HYPOTHESES, ACCUMULATION, DREDGED MATERIALS, DREDGING, HEIGHT, PLOTTING, ALGAE, BENTHONIC ZONES, PROPELLERS, FARM CROPS, ANCHORS, BLOWOUTS.

Subject Categories : Biology
      Ecology
      Hydrology, Limnology and Potamology

Distribution Statement : APPROVED FOR PUBLIC RELEASE