Nitrogen dynamics and phytoplankton community structure: the role of organic nutrients

Abstract

Dissolved organic nitrogen (DON) is recognised as an important N source for phytoplankton. However, its relative importance for phytoplankton nutrition and community composition has not been studied comprehensively. This study, conducted in a typical Scottish fjord, representative of nearpristine coastal environments, evaluates the utilisation of DON and dissolved inorganic nitrogen (DIN) by different microbial size fractions and the relationship of phytoplankton community composition with DON and other parameters. The study demonstrated that DON was important in supporting phytoplankton throughout the yearly production cycle. The higherthan-expected urea uptake rates and large fraction of the spring bloom production supported by DON suggested that organic N not only contributes to regenerated production and to the nutrition of the small phytoplankton fraction, but can also contribute substantially to new production of the larger phytoplankton in coastal waters. Multivariate statistical techniques revealed two phytoplankton assemblages with peaks in abundance at different times of the year: a spring group dominated by Skeletonema spp., Thalassiosira spp., and Pseudo-nitzschia spp. group delicatissima; and a summer/autumn group dominated by Chaetoceros spp., Scrippsiella spp., and Pseudonitzschia spp. group seriata. The multivariate pattern in community composition and abundance of these taxa was significantly correlated with the multivariate pattern of DON, urea, dissolved free amino acids, DIN, temperature, salinity, and daylength, with daylength and urea being particularly important, suggesting both physical and chemical controls on community composition.

Blooms of Dinoflagellate Mixotrophs in a Lower Chesapeake Bay Tributary: Carbon and Nitrogen Uptake over Diurnal, Seasonal, and Interannual Timescales

“…Urea and DFAA contributed significantly to the total measured N uptake during blooms (Figs. 3,4,6,7,and 8), consistent with other studies (Glibert et al 2001;Mulholland et al 2002Mulholland et al , 2009aHeil et al 2007;Anderson et al 2008;Gobler et al 2012;Boneillo and Mulholland 2014;Bronk et al 2014;Moschonas et al 2017). We also observed that high rates of DON uptake for these compounds were not limited to periods when there were blooms (Fig.…”

“…3, 4, and 8). During all years, DIN contributed substantially to N demand during both bloom and non-bloom periods, similar to what has been shown in other estuarine and coastal marine systems (Heil et al 2007;Mulholland and Lomas 2008;Mulholland et al 2009a, b;Boneillo and Mulholland 2014;Bronk et al 2014;Moschonas et al 2017 − was also a quantitatively large source of N to Gymnodinium sp. and other dinoflagellate-dominated phytoplankton communities (Fig.…”

“…During the summer of 2003, when there were no monospecific blooms observed, but dinoflagellates still dominated the phytoplankton community, uptake of DON compounds usually exceeded that of DIN. Similar observations were made in another eutrophic system during summer in the absence of algal blooms (Boneillo and Mulholland 2014) and in coastal systems where the composition of the dissolved N pool has been related to phytoplankton community composition (Heil et al 2007;Moschonas et al 2017).…”

Metagenomic characterization of the viral community of the South Scotia Ridge

“…The ecology of prokaryotes and protists, especially Antarctic phytoplankton during summer (11)(12)(13)(14)(15)(16), together with the major role of viruses in prokaryotes and eukaryotic phytoplankton mortality (17)(18)(19)(20) have been well studied. However, due to the geographical location and the difficulty of culturing viral hosts, an understanding of virus diversity and viral community structures in coastal regions of Antarctica including Sub-Antarctic areas is still lacking.…”

Influence of extractants and filter materials in the extraction of dissolved organic matter (DOM) from subtropical agricultural soil

“…Consequently, research based on DOM materials extracted by different methods may lead to different results, because various DOM components play different roles in ecological processes. For example, during the microbial degradation of DOM, components rich in N and P (i.e., amino acids and nucleotides) are transformed into inorganic nutrients (i.e., ammonium, nitrate, phosphate) (Moschonas et al, 2017;Brailsford et al, 2017). Low-molecular weight organic acids can improve the transport of metal ions in soil through the formation of metal-organic acid complexes (Wu et al, 2010 as they are less used by microorganisms (Nebbioso and Piccolo, 2013;Cotrufo et al, 2013).…”