Gracilaria Tikvahiae: A Feedstock for Bioenergy and Its Response to Increased Urea Concentrations.

The need to increase crop yields on ever shrinking acreage has lead to widespread utilization of N fertilizers to meet growing demands. While fertilizers have markedly improved yields, their downstream effect on sensitive coastal ecosystems was not well understood. When the link was finally made between artificial N fertilizers and eutrophication, it was already too late for many economically important bays and estuaries across the US. On the Delmarva Peninsula, bays such as the Assawoman and Chincoteage are annually subjected to large N fluxes tied to agriculture, urbanization, and precipitation events. Expansive nuisance algae blooms, including Gracilaria tikvahiae, are increasingly common, placing even further stress on these water bodies. While previously, most blooms were linked to the runoff of ammonium and nitrate, a recent shift towards urea has added a new dimension of uncertainty. The increased use of urea on system dynamics, especially for the nuisance algal species of Gracilaria has been investigated. Gracilaria tikvahiae was harvested from Assawoman and Chincoteague bays. Samples were cleaned and maintained in sterilized artificial seawater for 30 days under ambient lighting and temperature. Thereafter, 32.5cm segments, isolated from growing tips, were washed, weighed, treated with an antibiotic, and then placed in 6.6L growth tanks containing either 0µM, 1µM, 10µM, and 1mM Urea. After the trial, samples were reweighed and weight gains calculated. Initial findings indicated a significant effect of urea on Gracilaria growth (P<0.001). Greatest growth was experienced under 1mM urea although it was also found that the effects of 1mM and 10µM urea were similar, highlighting the alga’s ability to efficiently utilize available N. Based upon these findings, the implications of Gracilaria’s use in bioremediation and as a feedstock for bioenergy and food production in the region are also explored.