An annual cycle of biomass and productivity of Vallisneria americana in a subtropical spring-fed estuary

An annual cycle of biomass and productivity of wild celery (Vallisneria americana) was studied in Kings Bay, FL, USA. In situ growth rates were measured monthly between March 2001 and June 2002 in high-density stands, using a modified hole-punching technique, and applied to shoot density data to obtain areal estimates of production. Mean shoot density varied greatly over the study period, ranging between 200 and 800 shoots m−2. Mean total biomass ranged between 162 and 1013 g m−2, with aboveground material comprising, on average, 70% of total biomass. Total annual estimated production of new attached shoots was 519 g m−2. Leaf growth rates peaked at >50 mg shoot−1 d−1, and mass-specific leaf growth ranged 0.6-1.8% d−1. Annually, individual shoots produced 7.4 g of leaf material and completely replaced standing leaf biomass 3.5 times. Areal leaf production was highest in late spring/summer of 2001, and ranged between 3.6 and 23.0 g m−2 d−1. Annual total leaf production was 2704 g m−2. Seasonality was not apparent in most variables monitored monthly; only 1 of the 64 relationships we examined between environmental variables (nutrients, chlorophyll a, and irradiance) and Vallisneria biological variables were significant, with relative growth rate increasing linearly with irradiance. Peak biomass and productivity of Vallisneria in Kings Bay were high compared to literature values for other Vallisneria populations as well as global averages for well-studied seagrasses, emphasizing the potential importance of Vallisneria to whole ecosystem functioning in springs, lakes, and oligohaline reaches of many estuaries.