Use of Inorganic and Organic Nitrogen by Synechococcus spp. and Diatoms on the West Florida Shelf as Measured Using Stable Isotope Probing

Abstract

The marine nitrogen (N) cycle is a complex network of biological transformations in different N pools. The linkages among these different reservoirs are often poorly understood. Traditional methods for measuring N uptake rely on bulk community properties and cannot provide taxonomic information.15 N-based stable isotope probing (SIP), however, is a technique that allows detection of uptake of individual N sources by specific microorganisms. In this study we used 15 N SIP methodology to assess the use of different nitrogen substrates by Synechococcus spp. and diatoms on the west Florida shelf. Seawater was incubated in the presence of 15 N-labeled ammonium, nitrate, urea, glutamic acid, and a mixture of 16 amino acids. DNA was extracted and fractionated using CsCl density gradient centrifugation. Quantitative PCR was used to quantify the amounts of Synechococcus and diatom DNA as a function of density, and 15 N tracer techniques were used to measure rates of N uptake by the microbial community. The ammonium, nitrate, urea, and dissolved primary amine uptake rates were 0.077, 0. N-amino acids, but no evidence indicating uptake of labeled amino acids by diatoms was detected. These data suggest that N flow in communities containing Synechococcus spp. and diatoms has more plasticity than the new-versus-recycled production paradigm suggests and that these phytoplankters should not be viewed strictly as recycled and new producers, respectively.

Phytoplankton Response to Saharan Dust Depositions in the Eastern Mediterranean Sea: A Mesocosm Study

“…Additionally, as shown by PCA analysis, it is possible that DON released from dust particles played an auxiliary role in stimulating cyanobacteria, in the first response phase. This is not suprising since there is evidence that cyanobacteria can assimilate some small labile components of DON (Zubkov et al, 2003;Wawrik et al, 2009). DIN seemed to accumulate after the first two experimental days (Figure 1) mostly influencing the larger phytoplankton cells in the second response phase as shown by PCA analysis.…”

Nutrient supply controls picoplankton community structure during three contrasting seasons in the northwestern Mediterranean Sea

“…Prochlorococcus growth has traditionally been considered to be based mainly on regenerated forms of nitrogen (Moore et al , 2007, though they are also known to assimilate nitrate (Casey et al 2007, Martiny et al 2009, Treibergs et al 2014. Synechococcus are able to use a large diversity of new and regenerated forms of nitrogen, including nitrate, nitrite, ammonium, urea and amino acids (Glibert et al 1986, Wawrik et al 2009). They can even degrade their own phycoerythrin to use as an internal nitrogen source under extreme nitrogendepleted conditions (Wyman et al 1985).…”

Screening Assessment of Cyanobacteria and Cyanotoxins in Southern California Lentic Habitats

“…ISSN 2164-7682 2015 www.macrothink.org/emsd 106 TN had the strongest linear relationship with chlorophyll-a and cyanobacterial cell counts, with the particulate and dissolved organic fraction driving the strength of the relationship, indicating that nutrients have been incorporated into cyanobacterial growth or were recycling as dissolved organic forms within the water column. Other studies have found significant relationships between CyanoHABs and organic nitrogen sources, such as DON and urea, that are utilized by phytoplankton, and stimulate cyanobacterial growth (Kudela et al 2008;Wawrik et al 2009;Altman and Paerl 2012). The significant correlations between cyanobacterial cell counts, TN, and chlorophyll-a suggest that a primary target for management and mitigation strategies should be reduction in nutrient loading.…”