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Vallisneria americana grows in sandy to clay soils of estuarine habitats (Jarvis & Moore, 2008: 284).
In southern areas as in Kings Bay, FL, V.americana grows year round which contrasts to northern populations that pass the winter as belowground tubers (Hauxwell et al., 2007: 65). V. americana is better adapted to getting resources found in the soil than it is competing for sunlight. In oligotrophic(low nutrients) conditions, V.americana is a dominant species (Van et al., 1999: 231-232). Though V.americana is able to increase in size with added nutrients it does not grow as fast as the competitor Hydrilla verticillata (Van et al., 1999: 228-229).
Salinity has negative effects on the aquatic plant. In 2001, 590 Vallisneria americana plugs were taken out of the lower St. John’s River in Jacksonville, Florida (Boustany et al., 2009: 205). The plugs were exposed to 1 ppt, 8 ppt, and 18 ppt salinity levels and their growth was recorded for 20 weeks. By the end of the study, aboveground biomass increased by 34% in the 1 ppt treatment and decreased by 16% in the 8 ppt treatment (Boustany et al. 2009: 207). In the middle of this study, biomass of the 1ppt treatments had gone from 324 gdw m2 to 379 gdw m2 (Boustany et al., 2009: 208). Biomass in the 8 ppt salinity had decreased from 191 gdw m2 to 164.5 gdw m2. The plants in the 18 ppt salinity levels died by the 13th week (Boustany et al., 2009: 207-208).
Germination of Vallisneria americana seeds collected from Nanjemoy Creek, MD was studied (Jarves & Moore 2008: 283). At 15 psu mean seed germination was 9% as compared to 76 and 63% at 0 and 5 psu, respectively (Jarvis & Moore, 2008: 290). Temperature also affected seed germination with 97% germination at 29 °C as compared to 75% at 22 °C (Jarvis & Moore, 2008: 290).
In the St. John’s River, Florida, grazers such as sheepshead (Cyprinodon varegatus) shrimp (Palaemonetes spp.), snails (Neritina usnea), and manatees feed on the eel-grass. The aquatic plant also contributes to the detritivore web (Hauxwell et al., 2007: 66).
Boustany, R. G., Michot, T.C. & Moss, R.F. 2010. Effects of salinity and light on biomass and growth of Vallisneria americana from lower St. Johns River FL, USA. Wetlands Ecology and Management 18: 203-217.
Jarvis, J. C., Moore, K. A. 2008. Influence of environmental factors on Vallisneria americana seed germination. Aquatic Botany 88: 283-294.
Hauxwell, J., Frazer, T. K., & Osenberg, C. W. 2007. An annual cycle of biomass and productivity of Vallisneria americana in a subtropical spring-fed estuary. Aquatic Botany 87: 61-68
Van, T. K., Wheeler, G. S. & Center, T. D. 1999. Competition between Hydrilla verticillata and Vallisneria americana as influenced by soil fertility. Aquatic Botany 62: 225-233.