skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Nitrate, ammonium, and phosphorus drive seasonal nutrient limitation of chlorophytes, cyanobacteria, and diatoms in a hyper‐eutrophic reservoir
Title: Nitrate, ammonium, and phosphorus drive seasonal nutrient limitation of chlorophytes, cyanobacteria, and diatoms in a hyper‐eutrophic reservoir
Abstract Nitrogen (N) and phosphorus (P) inputs influence algal community structure and function. The rates and ratios of N and P supply, and different N forms (e.g., NO3and NH4), from external loading and internal cycling can be highly seasonal. However, the interaction between seasonality in nutrient supply and algal nutrient limitation remains poorly understood. We examined seasonal variation in nutrient limitation and response to N form in a hyper‐eutrophic reservoir that experiences elevated, but seasonal, nutrient inputs and ratios. External N and P loading is high in spring and declines in summer, when internal loading because more important, reducing loading N:P ratios. Watershed NO3dominates spring N supply, but internal NH4supply becomes important during summer. We quantified how phytoplankton groups (diatoms, chlorophytes, and cyanobacteria) are limited by N or P, and their N form preference (NH4vs. NO3), with weekly experiments (May–October). Phytoplankton were P‐limited in spring, transitioned to N limitation or colimitation (primary N) in summer, and returned to P limitation following fall turnover. Under N limitation (or colimitation), chlorophytes and cyanobacteria were more strongly stimulated by NH4whereas diatoms were often equally, or more strongly, stimulated by NO3addition. Cyanobacteria heterocyte development followed the onset of N‐limiting conditions, with a several week lag time, but heterocyte production did not fully alleviate N‐limitation. We show that phytoplankton groups vary seasonally in limiting nutrient and N form preference, suggesting that dual nutrient management strategies incorporating both N and P, and N form are needed to manage eutrophication.  more » « less
Award ID(s):
1930655 1255159
PAR ID:
10457670
Author(s) / Creator(s):
 ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Limnology and Oceanography
Volume:
65
Issue:
5
ISSN:
0024-3590
Page Range / eLocation ID:
p. 962-978
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; (, Journal of Plankton Research)
    Beisner, Beatrix E (Ed.)
    Abstract Eutrophication is increasingly becoming a problem for freshwater lakes. We evaluated the effects of additions nitrate (N as NO3−) and phosphate (P as PO43−) on phytoplankton in a temperate lake reservoir (Lake Murray, South Carolina). High-performance liquid chromatography and ChemTax were used to measure concentrations of microalgal groups in the lake in 2021–2023 and bioassays. The phytoplankton community during the summer months consisted of green algae (37%), diatoms (27%), cryptophytes (20%), cyanobacteria (11%) and dinoflagellates (4%). Bioassays of N (20-μM NaNO3), P (10-μM KH2PO4) and N + P additions were conducted monthly from April to October 2023. All microalgal groups, except cyanobacteria, exhibited nutrient co-limitation with N as the primary limiting nutrient. Similarly, cyanobacteria exhibited co-limitation, but with P as the primary limiting nutrient. Nutrient additions of N + P (but not N or P singularly) also resulted in significant community shifts, with a strong response by green algae. The management implications for this study are that increases in N and P loading and ratio changes in the lake may result in major phytoplankton community changes toward dominance by green algae. However, increasing P loading relative to N may promote cyanobacterial growth over other phytoplankton groups in this lake system. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; (, Limnology and Oceanography)
    Abstract Lake Erie, USA–Canada, plays an important ecological and socioeconomic role but has suffered from chronic eutrophication. In particular, western Lake Erie (WLE) is the site of harmful algal blooms (HABs) which are suspected of being driven by excessive nutrient (phosphorus (P) and nitrogen (N)) inputs. During 2022 and 2023, in situ nutrient dilution and addition bioassays were conducted at a WLE bloom‐impacted location to investigate whether a nutrient reduction regime would be effective in limiting phytoplankton growth during the June diatom‐dominated spring blooms and August cyanobacteria‐dominated summer blooms. The primary objectives of this experiment were to (1) Determine if a proposed 40% P‐alone reduction would effectively reduce phytoplankton growth and mitigate blooms and (2) assess whether reductions in both P and N are more effective in controlling phytoplankton biomass than exclusive reductions in either N or P. Samples were analyzed for nutrient concentrations and growth rate responses for specific algal groups, utilizing diagnostic (for major algal groups) photopigments. Results indicated that although both 20% and 40% dilutions led to lower phytoplankton biomass and growth rates, 40% reductions were more effective. Our results support the USA–Canada Great Lakes Water Quality Agreement recommendation of a 40% P reduction, but also indicate that a parallel reduction of N input by 40% would be most effective in controlling bloom magnitudes. Overall, our findings underscore the recommendation that a year‐round dual N and P 40% reduction is needed for long‐term control of eutrophication and algal blooms, including cyanobacteria and diatoms, in Lake Erie. 
    more » « less
  3. ; ; ; (, Soil Science Society of America Journal)
    Abstract Douglas‐fir [Pseudotsuga menziesii(Mirb.) Franco] is the predominant forest plantation species in the Pacific Northwest (PNW), with site productivity and fertilizer response influenced by climate and soil variations. This study investigates the utility of in situ 12‐week supply measurements of nitrogen (N), calcium (Ca), and phosphorus (P) to ion‐exchange resins (specifically Plant Root Simulator [PRS] probes) to estimate carbon (C):N ratios, soil nutrient contents (0–1 m), foliar nutrient concentrations, Douglas‐fir productivity (site index and basal area mean annual increment), and fertilizer volume response. PRS nutrient supply rates were correlated with N, Ca, and P soil nutrient contents (0–1 m), C:N ratios, and foliar nutrient concentrations. Low PRS NO3supply rates (<25 mg N·m−2·burial period−1) were correlated with lower Douglas‐fir productivity and greater fertilizer volume response. PRS NO3supply rates performed as well as total soil N contents and foliar N concentrations at estimating volume growth response to fertilizer. Twelve weeks after fertilization, PRS NO3, NH4, and Ca supply rates were significantly elevated compared to the unfertilized treatment. This research found that PRS probes were an effective in situ tool and are recommended for understanding N, Ca, and P nutrient availabilities, site productivity, and fertilizer response in Douglas‐fir plantations and for developing fertilizer prescriptions. 
    more » « less
  4. ; (, Geophysical Research Letters)
    Abstract We investigated nutrient patterns and their relationship to vertical carbon export using results from 38 Lagrangian experiments in the California Current Ecosystem. The dominant mode of variability reflected onshore‐offshore nutrient gradients. A secondary mode of variability was correlated with silica excess and dissolved iron and likely reflects regional patterns of iron limitation. The biological carbon pump was enhanced in high‐nutrient and Fe‐stressed regions. Patterns in the nutrient landscape proved to be better predictors of the vertical flux of sinking particles than contemporaneous measurements of net primary production. Our results suggest an important role for Fe‐stressed diatoms in vertical carbon flux. They also suggest that either preferential recycling of N or non‐Redfieldian nutrient uptake by diatoms may lead to high PO43−:NO3−and Si(OH)4:NO3−ratios, following export of P‐ and Si‐enriched organic matter. Increased export following Fe stress may partially explain inverse relationships between net primary productivity and export efficiency. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; (, Hydrobiologia)
    Cyanobacterial harmful algal blooms (CyanoHABs) are an increasingly common feature of large, eutrophic lakes. Non-N2-fixing CyanoHABs (e.g., Microcystis) appear to be proliferating relative to N2-fixing CyanoHABs in systems receiving increasing nutrient loads. This shift reflects increasing external nitrogen (N) inputs, and a[50-year legacy of excessive phosphorus (P) and N loading. Phosphorus is effectively retained in legacy-impacted systems, while N may be retained or lost to the atmosphere in gaseous forms (e.g., N2, NH3, N2O). Biological control on N inputs versus outputs, or the balance between N2 fixation versus denitrification, favors the latter, especially in lakes undergoing accelerating eutrophication, although denitrification removal efficiency is inhibited by increasing external N loads. Phytoplankton in eutrophic lakes have become more responsive to N inputs relative to P, despite sustained increases in N loading. From a nutrient management perspective, this suggests a need to change the freshwater nutrient limitation and input reduction paradigms; a shift from an exclusive focus on P limitation to a dual N and P colimitation and management strategy. The recent proliferation of toxic non-N2-fixing CyanoHABs, and ever-increasing N and P legacy stores, argues for such a strategy if we are to mitigate eutrophication and CyanoHAB expansion globally. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email