Planktonic nitrogen fixation in lakes is strongly related to lake trophic status, with moderate and high rates usually occurring only in eutrophic lakes. Among eutrophic lakes, nitrogen fixation is related to the ratio of nitrogen loading to phosphorus loading to the lake; significant nitrogen fixation by planktonic organisms generally occurs only when the N: P ratio of the nutrient loading is near or below the Redfield ratio of 16: 1. In contrast, nitrogen fixation by planktonic organisms is generally low in estuaries even when the N: P ratio of nutrients inputs is low.

The tendency toward less nitrogen fixation by plankton in estuaries and coastal marine ecosystems than in lakes subject to similar loadings of nitrogen and phosphorus may be due to a lower availability in oxic seawater of one or more trace elements required for nitrogen fixation, such as molybdenum and iron. Iron concentrations are generally lower in estuarine waters and seawater than in most lakes. And although molybdenum concentrations in seawater are actually higher than in lakes, molybdenum availability is probably lower, since sulfate inhibits molybdate assimilation by microbes. Molybdate is the primary form of molybdenum in oxic seawater, and the ratio of sulfate: molybdate is greater than in lakes. However, even in lakes sulfate is several orders of magnitude more abundant than molybdenum, and the ratio of dissolved sulfate to dissolved molybdenum typically is much greater than the ratio of sulfur to molybdenum apparently required by nitrogen-fixing cyanobacteria. Consequently, assimilation of molybdate by cyanobacteria is probably an energetically expensive process in all natural waters, but more so in seawater than in freshwaters. High concentrations of dissolved organic matter are known to favor blooms of cyanobacteria, perhaps by increasing iron and/or molybdenum availability through chelation.

The primary controls on nitrogen fixation in sediments, wetlands, macrophyte beds, and cyanobacterial mats may be different from those for fixation by planktonic organisms. Both molybdenum and iron are probably more available in these systems than in oxic waters, since reducing conditions and high DOC concentrations will increase iron solubility and favor the stability of reduced forms of molybdenum; sulfate should not inhibit the assimilation of these reduced molybdenum compounds. Consequently, nitrogenase synthesis (and, therefore, nitrogen fixation) in wetlands and in sediments may be less energetically expensive than in oxic water columns. A major control on nitrogen fixation in sediments may be repression of nitrogenase synthesis by high concentrations of ammonium, a factor less important to planktonic fixation because of the much lower concentrations of ammonium generally found in water columns than in sediments.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1988.33.4part2.0688

Nitrogen fixation in freshwater, estuarine, and marine ecosystems. 2. Biogeochemical controls1

Publisher Summary Besides the many species representative of the major eukaryotic algal phyla, the freshwater phytoplankton comprises a number of cyanobacteria (or blue-green algae) These aggregations have earned recognition in their own collective term, “water blooms” This chapter reviews the aspects of ecology of planktonic cyanobacreria in relation to the factors governing their buoyancy, population dynamics, and perennation in natural limnetic environments The buoyant properties of cyanobacteria are assessed in relation to the Stokes equation, drawing distinctions between the differential contributions of size, density, and form resistance among individual genera Density is altered through the erection or collapse of gas vesicles, their dilution by growth and through the maintenance of glycogen ballast The outcome of buoyancy-controlled movements in natural fields of turbulent mixing is described in empirical terms The chapter also reviews the growth requirements of cyanobacteria with respect to temperature, light, and nutrients together with their responses to deficiencies of supply The outcome of interactions between buoyancy regulation and limiting resources are proposed in a series of hypothetical model environments The circumstances under which excess buoyancy is acquired and expressed in surface bloom formation are re-examined Adaptations for perennation and re-establishment of populations after bloom formation or other adverse conditions are reviewed The evolutionary strategies of planktonic cyanobacteria are deduced

Cyanobacterial Water-Blooms

SUMMARY (1) Phytoplankton dynamics in Lake Lanao, Philippines, were studied over a 16-month period on the basis of weekly abundance measurements for seventy species and a number of physical and chemical variables. (2) An analysis of growth pulses and growth correlations in the major classes of phytoplankton provides evidence that the niche space is divided temporally on the basis of nutrient and light availability. Growth maxima of diatoms and cryptomonads occur during periods of relatively low light availability and high nutrient availability; pulses of green algae, blue-green algae and finally dinoflagellates occur successively towards the high light and low nutrient end of the spectrum. (3) Variations in total autotroph biomass over the 16-month period were more closely related to factors affecting growth than to factors affecting loss of biomass. Loss control factors nevertheless influenced succession by their differential effects on individual species. (4) Major factors controlling phytoplankton growth include light availability (computed from measurements of incident light, mixing depth and transparency) and nutrient availability (computed from measurements of nutrient concentrations, turbulence and change in depth of mixing). Individual species were arranged by statistical methods according to their growth patterns along gradients of these two factors. There is an identifiable taxonomic trend in the separation similar to that observed in the class-level analysis of succession, but a number of species showed divergent behaviour from others of their taxonomic group. (5) Measurable factors governing loss of autotroph biomass include grazing rate (analysed

Dynamics and succession of the phytoplankton in a tropical lake: lake lanao, philippines

The phytoplankton community of river–floodplain ecosystems shows significant temporal fluctuations in response to hydrosedimentological regime. The aim of our study was analyze the effect of the hydrosedimentological regime of the Parana and Ivinhema Rivers on the interannual variation in the composition, biovolume and functional groups of phytoplankton in an isolated floodplain lake (Ventura Lagoon) of the Ivinhema River State Park, located in the Upper Parana River floodplain (Mato Grosso do Sul State, Brazil). Samples of phytoplankton were taken at the sub-surface of the pelagic zone of the lake from February 2000 to December 2005. A total of 132 taxa were recorded, and the species that represented greater contributions to the phytoplankton biovolume were grouped into five functional groups (FG) (H1, H2, M, MP and Y). The distribution of the FGs were linked to the high and low water periods in Ventura lagoon. Functional groups MP and Y were the highest contributors to the phytoplankton biovolume during the high water periods, whereas FGs H1, H2 and M contributed more during the low water periods. The FGs were also useful for the interannual characterization of Ventura Lagoon by taking the changes caused by climatological factors into account. There was a strong dominance of Cyanobacteria (H2 and M) in 2000 and 2001 (La Nina periods) coincident with low precipitation and low hydrometric levels of the Parana and Ivinhema Rivers and, consequently, lower water depths of Ventura Lagoon. In 2002, 2003, 2004 and 2005 (El Nino periods), when higher precipitation, higher hydrometric levels, higher discharge of the Parana and Ivinhema Rivers and an increased depth of Ventura Lagoon were observed, Cyanobacteria (H1, H2 and M) were dominant, followed by Bacillariophyceae (MP) and Cryptophyceae (Y). These results reported here corroborate the utility of using FGs as indicators of interannual and seasonal variability in floodplain lakes.

Long-term variability of the phytoplankton community in an isolated floodplain lake of the Ivinhema River State Park, Brazil

(...) Nitrogen-fixation by the symbiont could sustain the symbiosis. Growth and nitrogenase activity demonstrated light saturation kinetics, with no photoinhibition up to 315 μE.m -2 .s -1 for growth and 780 μE.m -2 .s -1 for nitrogen fixation. The symbiosis is not obligate for Rhizosolenia, which is capable of growth independent of the symbiont if a nitrogen source is available. The symbion is contained in the periplasmic space between the Rhizosolenia plasmalemma and frustule, and preliminary evidence suggests excretion of fixed nitrogen into the medium may be occuring

Laboratory Culture and Preliminary Characterization of the Nitrogen-Fixing Rhizosolenia-Richelia Symbiosis

Nitrogen fixation at three stages of an autumnal bloom of Anabaena circinulis was measured after almost simultaneous collection at up to 32 stations in Clear Lake and algal hetcrocysts, phytoplankton cell numbers, NO,-N, NIL-N, dissolved organic-N, POh-P, Fe, primary production, particulate carbon, and chlorophyll a were also measured. Nitrogen fixation was significantly and positively correlated to Anabaena heterocyst numbers (P > 0.001 ), negatively correlated to NO,-N (P > 0.01 ), and positively correlated to dissolved organic-N (P > 0.01) and PO,-P (I’ > 0.05). A negative correlation with NH4 is probable; no significant relationship was found with the other variables mcasurcd. An cxplanation of the apparent restriction of substantial cyanophyccan Nz fixation to nonoligotrophic waters is proposed. The results arc consistent with the theory that heterocysts are responsible for Nz fixation in situ under oxic conditions.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1972.17.5.0693

Nitrogen fixation in clear lake, california. ii. synoptic studies on the autumn anabaena bloom1

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

J. E. Dillard

Author Tools

Chat about Author

Papers

Nitrogen fixation in clear lake, california. ii. synoptic studies on the autumn anabaena bloom1