Restoring seagrass in northern Gulf of Mexico waters: A test of the birdstake method

Background/Question/Methods

We examined the fertilizing effect of bird feces on seagrass (shoalgrass, Halodule wrightii) regrowth in propeller scars by studying three locations where birdstakes had been established 1, 2, and 5 years ago in northern Gulf of Mexico waters. Birdstakes are a piece of PVC and wood roosting block for birds to roost on. While birds are roosting they defecate their phosphorus rich feces into the water. Our study location was phosphorous limited which is why birdstakes were placed in propeller scars.

Results/Conclusions

 There was no significant change in seagrass species composition, biomass, percent cover, or shoot density compared to birdstake controls at any location. A significant decrease in the C:P and N:P ratios occurred at the location where birdstakes had been established 5 years prior, indicating phosphorous enrichment. There was no significant change in C:N:P ratios for animals collected adjacent to the birdstakes however, nor were  there significant differences in epiphyte biomass on seagrass leaves. Overall, birdstakes had little effect on shoalgrass beds in Northern Gulf of Mexico waters, in contrast to their positive effects on turtlegrass regrowth in South Florida.