GROWTH, PRIMARY PRODUCTIVITY, AND NITROGEN FIXATION POTENTIAL OF NODULARIA SPP. (CYANOPHYCEAE) IN WATER FROM A SUBTROPICAL ESTUARY IN THE UNITED STATES

Abstract

Nodularia is a halotolerant, filamentous, dinitrogen-fixing cyanobacterium that forms massive blooms in some coastal oceans, estuaries, and saline lakes worldwide. Although the genus is globally distributed, its blooms are sporadic and appear to be confined to certain water bodies. Blooms are frequently associated with phosphorus enrichment; therefore Nodularia may benefit from increased anthropogenic nutrient loading to coastal waters. We studied the potential for Nodularia to grow in the nitrogen-limited Neuse River Estuary (North Carolina, U.S.A.) with laboratory growth experiments in Neuse River Estuary water and by examining physico-chemical data from the estuary. Analysis of nutrients (nitrogen and phosphorus), salinity, and temperature data from the Neuse River Estuary between 1994 and 1998 revealed that suitable conditions for Nodularia prevailed during the summer of each of these years for time spans ranging from 1.5 to 5 months. Growth of two laboratory strains in Neuse River Estuary water was as fast or slightly slower than in artificial growth medium, as long as the culture inoculum had phosphorus reserves. Phosphorus addition did not stimulate growth of already phosphorus-sufficient inocula. Phosphorus starvation of the inoculum before the experiment decreased growth rates in the estuarine water unless additional phosphorus was supplied. Although phosphorus addition had a stimulatory effect on dinitrogen fixation and productivity, the effect differed for the two Nodularia strains. Results suggest that growth of Nodularia in North Carolinian estuaries is possible, and that such growth would be phosphorus-limited at times. Phosphorus availability may determine the times and locations for potential establishment of Nodularia in this and similar estuarine ecosystems.

Diversity of Toxic and Nontoxic Nodularia Isolates (Cyanobacteria) and Filaments from the Baltic Sea

“…The divergence of nontoxic N. sphaerocarpa from the nodularin-producing strains has been shown by 16S rRNA sequences (20,26) and whole-genome techniques (20). In addition, physiological experiments have indicated differences between nodularin-producing planktic Nodularia and nontoxic N. sphaerocarpa strains (19,27).…”

Small‐scale shear effects on heterocystous cyanobacteria

“…Resolving this question is important because these phytoplankton form toxic blooms and can be a significant water quality concern (Edler et al 1985;Codd et al 1994;Harding et al 1995). Moreover, heterocystous cyanobacteria include genera that are adapted to a wide range of salinities and therefore have the potential to substantially expand their present geographic range (Moisander and Paerl 2000). One explanation for their limited geographic range is that shear is controlling their growth in high shear environments that are otherwise suitable.…”

Fingerprinting Diazotroph Communities in the Chesapeake Bay by Using a DNA Macroarray

“…N 2 -fixing microorganisms are one component of aquatic microbial communities that can be important in providing fixed nitrogen in nitrogen-limited systems. In nitrogen-limited estuaries, blooms of nitrogen (N 2 )-fixing cyanobacteria can occur (4,22). Diverse heterotrophic N 2 -fixing bacteria are found in estuaries (1), but the roles that these microorganisms play in estuarine nutrient dynamics and the factors that determine the distribution of N 2 -fixing microorganisms (36) have not been defined.…”