Physiological responses of transplants of the freshwater angiosperm Vallisneria americana along a salinity gradient in the Caloosahatchee Estuary (Southwestern Florida)
- 111 Downloads
Fluctuations in freshwater input may affect the physiology and survival of submerged aquatic vegetation (SAV) occurring in oligoaline to mesohaline estuarine regions. Controls on the distribution of the freshwater angiosperm Vallisneria americana, were investigated by transplanting ramets. Pots (3.8-1) containing ramets were distributed among four sites (upstream site [least saline], donor site, near downstream site, and far downstream site [most saline]) in the Caloosahatchee Estuary (Southwest Florida) during wet (May–August) and dry (October–February) seasons. During 2–4 mo of each season, physiological indicators were monitored, including photosynthesis, glutamine synthetase activity, and protein content in shoots, and carbohydrates and total nitrogen and carbon in shoot and subterranean tissues. Where the physical environment (light or salinity) was suboptimal, all physiological indices, except photosynthetic rate, showed similar stress responses, which ranged from a slow decline to a rapid drop in physiological function. Levels of soluble carbohydrates decreased in response to unfavorable conditions more rapidly than did insoluble carbohydrates. Shoot protein of V. americana declined prior to transplant death, suggesting that measuring protein content may provide a rapid assessment of physiological health. V. americana transplants at the low-salinity upstream site died during both wet and dry season experiments, likely in response to light limitation and/or partial burial by sediments. At the far downstream site, death occurred within 2–4 wk, and was attributable to elevated salinities (>ca. 15‰). Comparison of physiological responses with salinity and light regimes at the donor and near downstream sites suggest that light may ameliorate salinity stress. This study demonstrates that V. americana, nominally classed as a freshwater macrophyte, is capable of a remarkable degree of halotolerance.
KeywordsSoluble Carbohydrate Submerged Aquatic Vegetation Downstream Site South Florida Water Management District Insoluble Carbohydrate
Unable to display preview. Download preview PDF.
- Appenroth, K. J. and H. Augsten. 1987. An improvement of protein determination in plant tissues with the dye-binding method according to Bradford. Biochemie und Physiologie der Pflanzen 182:85–89.Google Scholar
- Barko, J. W., R. M. Smart, and D. G. McFarland. 1982. Interactive effects of environmental conditions on the growth of submersed aquatic macrophytes. Journal of Freshwater Ecology 6: 199–209.Google Scholar
- Bourn, W. S. 1932. Sea-water tolerance of Vallisneria spiralis L. and Potamogeton foliosus Raf. Contributions of the Boyce Thompson Institute 6:303–308.Google Scholar
- Day, J. W., C. A. S. Hall, W. M. Kemp, and A. Yáñez-Arancibia. 1989. Estuarine Ecology. John Wiley & Sons, New York.Google Scholar
- Kozlowski, T. T. 1984. Flooding and Plant Growth. Academic Press, Cambridge.Google Scholar
- Knox, G. A. 1986. Estuarine Ecosystems: A Systems Approach. Volume I. CRC Press, Boca Raton, Florida.Google Scholar
- Kraemer, G. P. and R. S. Alberte. 1995. Impact of daily photosynthetic period on protein synthesis and carbohydrate stores in Zostera marina L. (eelgrass) roots: Implications for survival in light-limited environments. Journal of Experimental Marine Biology and Ecology 185:191–202.CrossRefGoogle Scholar
- Kraemer, G. P., L. Mazzella, and R. S. Alberte. 1997. Nitrogen assimilation and partitioning in the Mediterranean seagrass Posidonia oceanica. Marine Ecology, Publication of the Stazione Zoological di Napoli. 18(2):175–188.Google Scholar
- Macler, B. A. 1988. Salinity effects on photosynthesis, carbon allocation, and nitrogen assimilation in the red alga Gelidium coulteri. Plant Physiology 88:690–694.Google Scholar
- United States National Ocean Service. 1996. High and low water prediction, East Coast of North and South America. United States National Ocean Service, Silver Springs, Maryland.Google Scholar
- Yemm, E. W. and A. J. Willis. 1954. The estimation of carbohydrates in plant extracts by anthrone. Biochemical Journal 57: 508–514.Google Scholar