| This body of work consists of a two-year field monitoring project and complementary physiological laboratory experiments designed to investigate the influence of non-point source (NPS) nutrient pollution on aquatic plant community structure and invasion in the Weeks Bay National Estuarine Research Reserve (WBNERR), AL. Vegetation was monitored monthly, while habitat data were collected bi-monthly, from July 2008 to October in eight locations throughout the watershed. Aquatic plant assemblages were dominated by Vallisneria neotropicalis, Hydrilla verticillata, Eleocharis sp. and Najas guadalupensis. Statistical analysis of biotic and abiotic data revealed that there is a strong influence of NPS nitrogen input on aquatic plant abundance and distribution in the WBNERR.;Laboratory experiments indicate that (1) both V. neotropicalis (native) and H. verticillata (non-native) possess inducible forms of nitrate reductase (NR) and (2) NR activity is influenced by season. Hydrilla exhibited high photosynthetic performance and maximum NR levels that were two to three times higher than those of Vallisneria during fall and spring. Thus, nitrogen and carbon metabolism likely play important roles with respect to competitive interactions between Hydrilla and Vallisneria in nature. |
