Ruppia maritima seed and Thalassia testudinum seedling responses to fluctuations in salinity and ammonium

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Amanda E. Kahn (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Michael Durako

Abstract: Six species of seagrasses are present in Florida Bay ranging from stenohaline to euryhaline species. The dominant species, Thalassia testudinum Banks ex. König, has optimum growth around marine salinity. The second species examined in this study was Ruppia maritima L, which tends to grow near fresh water outflows. Although many studies have examined the responses of mature plants to environmental stresses, this study examined the impacts on seeds and seedlings. As the focus behind the study was altered water flow into Florida Bay, it examined hypo- and hyper-salinity, as well as depleted and elevated ammonium concentrations. This study was conducted in mesocosms on material collected in Florida Bay. R. maritima seed germination and T. testudinum seedling survival, growth, photosynthesis and osmolality were investigated over a two-year study. Year one focused on direct introductions into hyper- and hypo-saline conditions and year two examined the impact of gradual increase/decrease in salinity as well as the addition of ammonium. R. maritima seeds did not germinate above 28 PSU and the highest percent germination occurred between 0 and 10 PSU. Elevated levels of ammonium decreased germination. Hypo-saline conditions were, however, detrimental to the fitness of T. testudinum seedlings, as were hyper-saline conditions. Plants at 0 and 70 PSU showed 100% mortality and decreased survival in the 60, 50 and 10 PSU treatments. Increased levels of ammonium decreased growth in the lower salinity treatments. Plants grown around 30-40 PSU showed the greatest growth (i.e. most productivity). Measurements of quantum yields as well as relative electron transport rate using PAM fluorometry showed a decrease in photosynthetic performance on either side of this 30-40 PSU optimum. Tissue osmolality increased significantly with increased salinity and tissue remained distinctly and consistently hyperosmotic to the media. Results suggest that a change in fresh water flow as well as possible increase in ammonium may negatively impact the ability of T. testudinum seedlings to establish and possibly cause a shift in the floral composition of Florida Bay, favoring euryhaline species such as Ruppia maritima.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Ruppia maritima--Effect of ammonium on--Florida--Florida Bay, Ruppia maritima--Effect of salt on--Florida--Florida Bay, Ruppia maritima--Seeds, Thalassia--Effect of ammonium on--Florida--Florida Bay, Thalassia--Seedlings
Ruppia maritima -- Seeds
Ruppia maritima -- Effect of salt on -- Florida -- Florida Bay
Ruppia maritima -- Effect of ammonium on -- Florida -- Florida Bay
Thalassia -- Seedlings
Thalassia -- Effect of ammonium on -- Florida -- Florida Bay

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