Carolyn concluded her artificial seagrass unit (ASU) experiment in Florida Bay last week (despite TS Fay's best efforts to deter us). The objective of the study was to determine if seagrass epifauna responded to nutrient additions because of changes in the food resources (epiphytes) or because of changes in the canopy complexity as faster-growing, highly branched species proliferated. We are particularly interested in grazing crustaceans like grass shrimp (left), but other species like nudibranchs (below) were also present.
We installed ASUs with dense and sparse canopies made from polypropylene ribbon. Half were enriched and half were not. After 3 months, it seems that epifauna were more abundant in enriched plots, regardless of canopy density. This is a qualitative assertion, however--canopy effects may not be as strong (and therefore not as visually obvious) as nutrient effects. Carolyn is looking forward to many weeks of sorting, identifying, and enumerating these creatures to find more definitive answers to our questions.
Thursday, August 21, 2008
The water and sky meet seamlessly--only a few mangrove islands and cotton ball clouds reveal the transition. Such was the scene in Florida Bay last week, before TS Fay swept us out of our study site. This is the third tropical storm to hit one of my study sites in the last month: Dolly in Pt Aransas, Edouard in Pt Aransas, and now Fay. None of the storms have been serious, and aside from the disruptions, our work has gone on. Heroic efforts on Carolyn's part ensured that the artificial seagrass experiment was brought to completion (pictures here), despite the storm. Did nutrients or canopy density have a stronger impact on epifaunal communities? Stay tuned...