Salmon subsidies alleviate nutrient limitation of benthic biofilms in southeast Alaska streams

Using nutrient-diffusing substrata (NDS) in seven streams in southeast Alaska, USA, we tested whether (i) nutrient limitation of autotrophic and heterotrophic biofilms was alleviated by salmon resource subsidies, and (ii) whether the degree of alleviation could be predicted by environmental variables. Before salmon spawners arrived, autotrophic biofilms were nitrogen (N)-limited, or co-limited by N and phosphorus (P), whereas heterotrophic biofilms were either P-limited, or co-limited by N and P. Combined N and P amendments resulted in a 2.6-fold increase in biofilm chlorophyll a, and a 3.2-fold increase in community respiration. After salmon arrived, autotroph nutrient limitation was alleviated in six of the seven streams. Heterotrophs still exhibited nutrient limitation in six streams, but most streams shifted from co-limitation to P-limitation. Nutrient-diffusing substrata amended with salmon tissue indicated that salmon could also be an important source of organic carbon for biofilms. Autotrophs responded less to N and P amendments as streamwater ammonium concentration increased with the arrival of salmon. For heterotrophs, ammonium concentration and N:P ratio best predicted changes in response following the arrival of salmon. We provide the first direct evidence that biofilm nutrient limitation can be alleviated by salmon spawners in nutrient-poor streams.

Download Full-text

Phytoplankton productivity across prairie saline lakes of the Great Plains (USA): a step toward deciphering patterns through lake classification models

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f09-083 ◽

2009 ◽

Vol 66 (9) ◽

pp. 1435-1448 ◽

Cited By ~ 17

Author(s):

Courtney R. Salm ◽

Jasmine E. Saros ◽

Sherilyn C. Fritz ◽

Christopher L. Osburn ◽

David M. Reineke

Keyword(s):

Primary Production ◽

Nutrient Limitation ◽

Great Plains ◽

Saline Lakes ◽

Information Criterion ◽

The United States ◽

Northern Great Plains ◽

Classification Models ◽

Phytoplankton Productivity ◽

P Limitation

We investigated patterns of primary production across prairie saline lakes in the central and northern Great Plains of the United States. Based on comparative lake sampling in 2004, seasonal predictors of algal primary productivity were identified within subsets of similar lakes using a combination of Akaike’s information criterion (AIC) and classification and regression trees (CART). These models indicated complex patterns of nutrient limitation by nitrogen (N), phosphorus (P), and iron (Fe) within different lake groups. Nutrient enrichment assays (control, + Fe, + N, + P, + N + P) were performed in spring and summer of 2006 to determine if phytoplankton in selected lakes followed predicted patterns of nutrient limitation. Both the comparative lake sampling and experimental results indicated that N limitation was widespread in these prairie lakes, with evidence for secondary P limitation in certain lakes. In the experiments, iron did not stimulate primary production. Our results suggest that given the diverse geochemical nature of these lakes, classification models that separate saline lakes into subsets may be an effective method for improving predictions of algal production.

Download Full-text

Biomass production, N:P ratio and nutrient limitation in a Caucasian alpine tundra plant community

Journal of Vegetation Science ◽

10.1111/j.1654-1103.2005.tb02379.x ◽

2005 ◽

Vol 16 (4) ◽

pp. 399-406 ◽

Cited By ~ 51

Author(s):

N.A. Soudzilovskaia ◽

V.G. Onipchenko ◽

J.H.C. Cornelissen ◽

R. Aerts

Keyword(s):

Nutrient Limitation ◽

Plant Community ◽

Biomass Production ◽

N:P Ratio ◽

Alpine Tundra

Download Full-text

Plants increase silicon content as a response to nitrogen or phosphorus limitation: a case study with Holcus lanatus

Plant and Soil ◽

10.1007/s11104-020-04667-1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Vanessa Minden ◽

Jörg Schaller ◽

Harry Olde Venterink

Keyword(s):

Nutrient Limitation ◽

Plant Performance ◽

Light Limitation ◽

Grass Species ◽

Holcus Lanatus ◽

P Deficiency ◽

Plant Organs ◽

N Limitation ◽

P Limitation ◽

Si Content

Abstract Aims Silicon (Si) has been shown to beneficially affect plant performance under stressful environmental conditions, such as water or nutrient deficiency. Here we tested the effects of two important plant nutrients, nitrogen (N) and phosphorus (P), on Si content in different plant organs in the grass species Holcus lanatus. Methods We studied trait responses to N limitation, balanced nutrient availability and P limitation. Single plant individuals were grown in sand-filled pots in a greenhouse for 2 months. Nitrogen, phosphorus, carbon and silicon contents were determined in leaves, stems and roots, as were leaf and roots traits, biomass production and root enzyme activity. Results Si content was lowest under balanced nutrient supply in all plant organs. Under P limitation Si content was highest in leaves and stems, in roots it was highest under N limitation. Si:C ratios were lowest under balanced conditions, and highest under nutrient limitation. Root phosphatase activity was highest under P limitation and chlorophyll content was lowest under N limitation. Conclusions Our model species assimilated less ‘high cost C’ and took up more ‘low cost Si’ under nutrient limitation, especially under P deficiency. Si potentially plays an important role in different environments, such as nutrient or light limitation, which in turn may be related to different plant strategies, for example higher stem rigidity in high Si plants versus higher stem flexibility in low Si plants. More research is needed to further elucidate the role of silicon in different concepts of trait-environment relationships.

Download Full-text

N and P limitation shapes plant-AMF interactions across an aridity gradient

10.5194/egusphere-egu2020-12829 ◽

2020 ◽

Author(s):

Svenja Stock ◽

Moritz Köster ◽

Jens Boy ◽

Roberto Godoy ◽

Francisco Nájera ◽

...

Keyword(s):

Nutrient Limitation ◽

Drought Resistance ◽

Plant Nutrition ◽

Water Shortage ◽

Aridity Gradient ◽

P Limitation ◽

Mediterranean Conditions ◽

Mediterranean Woodland ◽

Semiarid Conditions

Arbuscular mycorrhizal fungi (AMF) are important partners in plant nutrition, as they increase the range to scavenge for nutrients and can access resources otherwise occlude for plants. Under water shortage, when mobility of nutrients in soil is limited, AMF are especially important to acquire resources and can modulate plant drought resistance. Strategies of plants to cope with water and nutrient restrictions are shaped by the intensity of aridity. To investigate the effect of aridity on plant-AMF associations regarding drought resistance and plant nutrient acquisition, a 13CO2 pulse labeling was conducted across an aridity gradient. In a semiarid shrubland (66 mm a-1), a Mediterranean woodland (367 mm a-1), and a humid temperate forest (1500 mm a-1), root and soil samples were taken from 0-10 cm and 20-30 cm soil depth before labeling and at 1 day, 3 days, and 14 days after labeling. Carbon (C), nitrogen (N), and phosphorus (P) stocks as well as AMF root colonization, extraradical AMF biomass (phospho- and neutral lipid fatty acids (PLFA and NLFA) 16:1w5c), specific root length (SRL), and root tissue density (RTD) were measured. Plant C investment into AMF and roots was determined by the 13C incorporation in 16:1w5c (PLFA and NLFA) and root tissue, respectively. Soil C:N:P stoichiometry indicated a N and P limitation under humid conditions and a P limitation in the topsoil under Mediterranean conditions. N stocks were highest in the Mediterranean woodland. A strong correlation of the AMF storage compound NLFA 16:1w5c to C:P ratio under semiarid conditions pointed to a P limitation of AMF, likely resulting from low P mobility in dry and alkaline soils. With increasing aridity, the AMF abundance in root (and soil) decreased from 45% to 20% root area. 13C incorporation in PLFA 16:1w5c was similar across sites, while relative AMF abundance in topsoil (PLFA 16:1w5c:SOC) was slightly higher under semiarid and humid than under Mediterranean conditions, pointing to the importance of AMF for plant nutrition under nutrient limitation. Additionally, PLFA 16:1w5c contents in soil were higher with lower P availability in each site, underlining the role of AMF to supply P for plants under P deficiency. Under humid conditions (with strong N and P limitation) and semiarid conditions (with strong water limitation), root AMF colonization increased with lower N availability, displaying the role of AMF for plant N nutrition under nutrient and/or water shortage. Under humid and Mediterranean conditions, SRL decreased (0.5 and 0.3 times, respectively) and RTD increased (1.9 and 1.7 times, respectively) with depth, indicating a drought tolerance strategy of plants to sustain water shortage. Under semiarid conditions, SRL increased with depth (2.3 times), while RTD was consistently high, suggesting an increasing proportion of long-living fine roots with depth as scavenging agents for water. These relations point to a drought avoidance strategy of plants as adaptation to long-term water limitation. Under strong nutrient limitation, as under humid and semiarid conditions, AMF are crucial to sustain plant nutrition and to enhance plant resistance to water shortage.

Download Full-text

Microbial nutrient limitation in arctic lakes in a permafrost landscape of southwest Greenland

Biogeosciences Discussions ◽

10.5194/bgd-12-11863-2015 ◽

2015 ◽

Vol 12 (14) ◽

pp. 11863-11890

Author(s):

B. Burpee ◽

J. E. Saros ◽

R. M. Northington ◽

K. S. Simon

Keyword(s):

Nutrient Limitation ◽

Enzyme Activities ◽

Arctic Lakes ◽

The Arctic ◽

Nutrient Concentrations ◽

Nutrient Inputs ◽

P Limitation ◽

Microbial P ◽

Microbial Nutrient Limitation ◽

Southwest Greenland

Abstract. Permafrost is degrading across regions of the Arctic, which can lead to increases in nutrient concentrations in surface freshwaters. The oligotrophic state of many arctic lakes suggests that enhanced nutrient inputs may have important effects on these systems, but little is known about microbial nutrient limitation patterns in these lakes. We investigated microbial extracellular enzyme activities (EEAs) to infer seasonal nutrient dynamics and limitation across 24 lakes in southwest Greenland during summer (June and July). From early to late summer, enzyme activities that indicate microbial carbon (C), nitrogen (N), and phosphorus (P) demand increased in both the epilimnia and hypolimnia by 74 % on average. Microbial investment in P acquisition was generally higher than that for N. Interactions among EEAs indicated that bacteria were primarily P limited. Dissolved organic matter (DOM, measured as dissolved organic carbon) was strongly and positively correlated with microbial P demand (R2 = 0.84 in July), while there were no relationships between DOM and microbial N demand. Microbial P limitation in June epilimnia (R2 = 0.67) and July hypolimnia (R2 = 0.57) increased with DOM concentration. The consistency of microbial P limitation from June to July was related to the amount of DOM present, with some low DOM lakes becoming N-limited in July. Our results suggest that future changes in P or DOM inputs to these lakes are likely to alter microbial nutrient limitation patterns.

Download Full-text

Bioprocess Optimization for the Production of Arthrospira (Spirulina) platensis Biomass Enriched in the Enzyme Alkaline Phosphatase

Bioengineering ◽

10.3390/bioengineering8100142 ◽

2021 ◽

Vol 8 (10) ◽

pp. 142

Author(s):

Giorgos Markou

Keyword(s):

Alkaline Phosphatase ◽

Single Cell ◽

Protein Content ◽

Fold Increase ◽

Arthrospira Platensis ◽

P Availability ◽

Alp Activity ◽

P Limitation ◽

Protein Rich ◽

Enzyme Alkaline Phosphatase

The enzyme alkaline phosphatase (ALP) is gaining interest because it exerts bioactive properties and may be a potentially important therapeutic agent for many disorders and diseases. Microalgae are considered an important novel source for the production of diverse bio-compounds and are gaining momentum as functional foods/feeds supplements. So far, studies for the production of ALP are limited to mammalian and partly to some heterotrophic microbial sources after its extraction and/or purification. Methods: Arthrospira was cultivated under P-limitation bioprocess and the effect of the P-limitation degree on the ALP enrichment was studied. The aim of this work was to optimize the cultivation of the edible and generally-recognized-as-safe (GRAS) cyanobacterium Arthrospira platensis for the production of single-cell (SC) biomass enriched in ALP as a potential novel functional diet supplement. Results: The results revealed that the relationship between intracellular-P and single-cell alkaline phosphatase (SC-ALP) activity was inverse; SC-ALP activity was the highest (around 50 U g−1) when intracellular-P was the lowest possible (around 1.7 mg-P g−1) and decreased gradually as P availability increased reaching around 0.5 U g−1 in the control cultures. Under the strongest P-limited conditions, a more than 100-fold increase in SC-ALP activity was obtained; however, protein content of A. platensis decreased significantly (around 22–23% from 58%). Under a moderate P-limitation degree (at intracellular-P of 3.6 mg-P g−1), there was a relatively high SC-ALP activity (>28 U g−1) while simultaneously, a relative high protein content (46%) was attained, which reflects the possibility to produce A. platensis enriched in ALP retaining though its nutritional value as a protein rich biomass source. The paper presents also results on how several parameters of the ALP activity assay, such as pH, temperature etc., and post-harvest treatment (hydrothermal treatment and biomass drying), influence the SC-ALP activity.

Download Full-text

Impacts of the non-native alga Sargassum horneri on benthic community production in a California kelp forest

Marine Ecology Progress Series ◽

10.3354/meps13231 ◽

2020 ◽

Vol 637 ◽

pp. 45-57 ◽

Cited By ~ 2

Author(s):

GH Sullaway ◽

MS Edwards

Keyword(s):

Temporal Dynamics ◽

Kelp Forest ◽

Fold Increase ◽

Sargassum Horneri ◽

Community Respiration ◽

Ecosystem Change ◽

Rocky Reef ◽

Net Community Production ◽

Benthic Chambers ◽

Community Production

The arrival of Sargassum horneri throughout the Southern California Bight and the Baja Peninsula has raised concern regarding kelp forest resilience and ecosystem function following the invasion of this non-native species. To understand how S. horneri impacts native algal abundance and community production, we removed S. horneri from experimental plots over a period of 11 mo. We measured impacts on native algal communities and community productivity using SCUBA surveys and benthic chambers equipped with oxygen, temperature, and light sensors. We observed a nearly 4-fold increase in recruitment of Macrocystis pyrifera and a 9-fold increase in adult M. pyrifera stipe density in S. horneri removal plots, but no discernable changes in net community production among treatments. We found ephemeral increases in gross community production and community respiration in the non-removal plots that coincided with periods of peak S. horneri biomass. To understand the temporal dynamics of community production, we deployed benthic chambers across a rocky reef dominated by S. horneri. Here, temporal variation in community production was most strongly related to corresponding variation in water temperature and changes in S. horneri biomass related to its annual lifecycle. Overall, our study indicates that S. horneri presence contributed to ephemeral increases in gross community production and community respiration, but it did not affect net community production. Moreover, S. horneri removal can lead to increases in native algal abundances given favorable abiotic conditions. We suggest that S. horneri thrives in a disturbed ecosystem rather than being a driver of ecosystem change.

Download Full-text

Nitrification and its oxygen consumption along the turbid Chang Jiang River plume

Biogeosciences ◽

10.5194/bg-11-2083-2014 ◽

2014 ◽

Vol 11 (7) ◽

pp. 2083-2098 ◽

Cited By ~ 47

Author(s):

S. S.-Y. Hsiao ◽

T.-C. Hsu ◽

J.-w. Liu ◽

X. Xie ◽

Y. Zhang ◽

...

Keyword(s):

Ammonia Oxidation ◽

River Mouth ◽

Amoa Gene ◽

Free Water ◽

River Plume ◽

Community Respiration ◽

Ammonium Concentration ◽

Nitrification Rate ◽

Nitrification Process ◽

Iron And Manganese

Abstract. Nitrification is a series of processes that oxidizes ammonia to nitrate, which contributes to hypoxia development in coastal oceans, especially in eutrophicated regions. The nitrification rate of bulk water (NRb) and particle free water (NRpf, particle > 3 μm eliminated) were determined along the Chang Jiang River plume in August 2011 by nitrogen isotope tracer technique. Measurements of dissolved oxygen (DO), community respiration rate (CR), nutrients, dissolved organic nitrogen (DON), total suspended matter (TSM), particulate organic carbon/nitrogen (POC / PON), acid-leachable iron and manganese on suspended particles and both archaeal and β-proteobacterial ammonia monooxygenase subunit A gene (amoA) abundance on size-fractioned particles (> 3 μm and 0.22–3 μm) were conducted. The NRb ranged from undetectable up to 4.6 μmol L−1 day−1, peaking at a salinity of ~ 29. NRb values were positively correlated with ammonium concentration, suggesting the importance of substrate in nitrification. In the river mouth and the inner plume, NRb was much higher than NRpf, indicating that the nitrifying microorganism is mainly particle associated, which was supported by its significant correlation with amoA gene abundance and TSM concentration. The estimated oxygen demands of nitrification accounted for 0.32 to 318% of CR, in which 50% samples demanded more oxygen than that predicted by by the Redfield model (23%), indicating that oxygen might not be the sole oxidant though DO was sufficient (> 58 μmol kg−1) throughout the observation period. The excess nitrification-associated oxygen demand (NOD) showed a tendency to occur at lower DO samples accompanied by higher acid-leachable Fe / Mn, which implied reactive Fe3+ / Mn4+ may play a role as oxidant in the nitrification process. Stoichiometric calculation suggested that reactive Fe on particles was 10 times the oxidant demand required to complete ammonia oxidation in the entire plume. The potential involvement of reactive iron and manganese in the nitrification process in oxygenated water further complicated nitrogen cycling in the turbid river plume.

Download Full-text