Summer Field Program 2008
Adventures in Botany: Water Quality, Seagrasses, and Saltmarsh Nurseries
Patrick D. Biber
Seagrasses are marine plants that occur in many shallow coastal areas of the world. They are located at the bottom of the water column and are sensitive to changes in water quality that result in reduced light penetration. An optical water quality analysis has been developed to assess habitat suitability (water clarity) for the seagrasses Zostera marina (eelgrass) and Halodule wrightii (shoalgrass) and will improve early detection of unsuitable conditions. The approach focuses on determining the amount of total suspended solids (TSS), phytoplankton chlorophyll (chl a), and colored dissolved organic matter (CDOM) in the water. Regional and local differences in water quality result in changes to the threshold conditions, with eutrophication driving the system to a potentially unsuitable state.
Responses by Zostera and Halodule grown under two different light environments were tested. Experiments were designed to test (a) constant light limitation stress, and (b) pulsed light limitation events followed by various duration recovery intervals. Under the press experiment (a) growth and photosynthesis responses were found to be similar in the two species. Under pulsed conditions (b) Zostera was more robust to perturbations than Halodule. The implications of these experimental findings are that different species will be able to withstand eutrophication to various degrees, and that shifts in species composition are likely in areas where multiple species co-occur.
Botany operates a 3000 sq. foot greenhouse that is being used as a Plant Nursery to grow saltmarsh plants, which are being used to restore coastal wetlands. This program is growing the two most common coastal marsh plants: Juncus roemerianus (black needlerush) and Spartina alterniflora (smooth cordgrass). The tidal marshes in Mississippi are dominated by these two species. The Plant Nursery is growing plants only from native seeds to avoid problems that could arise from interbreeding the genetic stock of Mississippi with other (e.g., Florida or Louisiana) plant sources. This will help to avoid potential disease risk introduced from other plant stocks.
Presentation Slides
