DeYoe, H.R. and C.A. Suttle. 1994. A persistent bloom-forming alga that cannot use nitrate-nitrogen. Abstracts American Society Limnology and Oceanography, and Phycological Society American, Miami, FL, June 1994.

A planktonic alga similar to Aureococcus anophagefferens has caused persistent and ecologically-damaging blooms in Laguna Madre, a marine lagoon system located along the south Texas coast. In growth experiments using 100 µM nitrate, nitrite, and ammonium in artificial seawater, it was found that this alga could not grow on nitrate. The addition of nitrate to stationary phase nitrogen-limited cultures did not stimulate growth, while nitrite or ammonium spikes led to culture growth and increased yields. Doubling iron or trace metal concentrations did not permit growth on nitrate. Chemical characterization of cultures grown in the presence of excess nitrate or ammonium were consistent with nitrate-grown cells being nitrogen-starved [Nitrate- vs. Ammonium-grown cells: Nitrogen per cell, 0.19 vs. 0.56 pg N/cell; C:N, 73:1 vs. 15:1; carbon to chlorophyll a ratio, 270:1 vs. 43:1; chlorophyll a per cell, 0.043 vs. 0.16 pg/cell]. Furthermore, this isolate was chlorate-insensitive while a similar bloom-forming alga from the Northeastern USA, A. anophagefferens, was chlorate-sensitive, which suggested that nitrate reductase was non-functional in the Texas isolate, but functional in A. anophagefferens. The development of the initial Texas algal bloom was preceded by a drought and two severe freezes that led to abnormally high salinities and ammonium concentrations in the Laguna Madre. These conditions may have led to bloom development.

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