Identifying Limiting Nutrients in Galveston Bay Seagrass Communities



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Seagrasses, an ecologically important group of marine plants, have declined in worldwide areal extent by 29% since 1879, in part due to nutrient enrichment. To reduce this decline, it is important to discover the limiting nutrient of a system and regulate its input. We examined the effects of nutrient addition on Galveston Bay seagrass communities by fertilizing with nitrogen (N) and phosphorus (P). We utilized 12 ‐ 1 m2 plots, which we monitored for 20 days after fertilization. Benthic microalgal biomass was significantly higher in plots that had both N and P addition, suggesting co‐limitation. P fertilization increased P levels of Halodule wrightii only on day 11, while N levels were unaltered by any treatment. Neither seagrass nor macroalgae cover changed in response to nutrients. Given the changes observed in this study, it is possible that the seagrass and microalgae in the bay system are limited by different nutrients. We believe there were stronger nutrient responses in microalgae relative to seagrass because algae are faster growing plants that could quickly adjust to the new nutrient levels. Alternatively, the seagrass community may be nitrogen and phosphorus saturated, but limited instead by another factor, such as space or light availability.


Final report of the summer research experience. 20 page Word document includes bibliography, tables and graphs


Galveston Bay, seagrass, limiting nutrients