Turtle grass herbivory and the effect of nutrient enhancement – Gary and Kevin

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Setting out the turtle grass tethers (in low visibility conditions).

Due to the fresh groundwater infiltrating into the lagoon of Discovery Bay, the Thalassia Testudinum in the area is naturally enriched with nitrogen. In our study, we collected samples of grass from both nitrogen enriched areas and from areas of normal conditions. We enriched some of the blades with phosphorus to determine a preference from marine life grazers. This was accomplished by securing the blades of grass to tethers using clothes pins, and by fastening those tethers to tiles with zip-ties. To get a complete understanding of the herbivory in the area, we sampled the grass from both the lagoon and bay to determine the bites on each blade. Many blades of grass appeared scared by what seems to be urchins. These blades were discarded, since we are counting only clear bites in the grass. Although the data did not show significant differences between the phosphorus enriched blades and naturally occurring blades of grass, there was a slight preference shown toward the phosphorus enriched grass. The toughness of the grass was also tested in each area by using a tensometer, and no significant difference was found.

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