scholarly journals Tidal and seasonal forcing of dissolved nutrient fluxes in reef communities

2019 ◽  
Vol 16 (9) ◽  
pp. 1921-1935 ◽  
Author(s):  
Renee K. Gruber ◽  
Ryan J. Lowe ◽  
James L. Falter
Keyword(s):  
Mass Transfer ◽  
Nutrient Supply ◽  
Tidal Range ◽  
Nutrient Concentrations ◽  
Nutrient Fluxes ◽  
Flow Measurements ◽  
Uptake Rates ◽  
Reef Communities ◽  
Flow Speeds ◽  
Strong Control

Abstract. Benthic fluxes of dissolved nutrients in reef communities are controlled by oceanographic forcing, including local hydrodynamics and seasonal changes in oceanic nutrient supply. Up to a third of reefs worldwide can be characterized as having circulation that is predominantly tidally forced, yet almost all previous research on reef nutrient fluxes has focused on systems with wave-driven circulation. Fluxes of dissolved nitrogen and phosphorus were measured on a strongly tide-dominated reef platform with a spring tidal range exceeding 8 m. Nutrient fluxes were estimated using a one-dimensional control volume approach, combining flow measurements with modified Eulerian sampling of waters traversing the reef. Measured fluxes were compared to theoretical mass-transfer-limited uptake rates derived from flow speeds. Reef communities released 2.3 mmol m−2 d−1 of nitrate, potentially derived from the remineralization of phytoplankton and dissolved organic nitrogen. Nutrient concentrations and flow speeds varied between the major benthic communities (coral reef and seagrass), resulting in spatial variability in estimated nitrate uptake rates. Rapid changes in flow speed and water depth are key characteristics of tide-dominated reefs, which caused mass-transfer-limited nutrient uptake rates to vary by an order of magnitude on timescales of ∼ minutes–hours. Seasonal nutrient supply was also a strong control on reef mass-transfer-limited uptake rates, and increases in offshore dissolved inorganic nitrogen concentrations during the wet season caused an estimated twofold increase in uptake.

scholarly journals Tidal and seasonal forcing of dissolved nutrient fluxes in reef communities

2018 ◽  
Author(s):  
Renee K. Gruber ◽  
Ryan J. Lowe ◽  
James L. Falter
Keyword(s):  
Mass Transfer ◽  
Control Volume ◽  
Inorganic Nitrogen ◽  
Nutrient Supply ◽  
Nutrient Concentrations ◽  
Nutrient Fluxes ◽  
Uptake Rates ◽  
Reef Communities ◽  
Flow Speeds ◽  
Strong Control

Abstract. Benthic fluxes of dissolved nutrients in reef communities are controlled by oceanographic forcing including hydrodynamic regime and seasonal changes in oceanic nutrient supply. Up to a third of reefs worldwide can be characterised as having circulation that is tidally-driven, yet almost all previous research on reef nutrient fluxes has focused on systems with wave-driven circulation. Fluxes of dissolved nitrogen and phosphorus were measured on a strongly tide-dominated (spring range > 8 m) reef platform located in the Kimberley region of northwest Australia. A one-dimensional control volume approach was used, which combines continuous measurements of flow with modified Eulerian sampling of waters traversing the reef. Measured fluxes were compared to theoretical mass-transfer-limited uptake rates derived from flow speeds. Reef communities released a moderate amount of nitrate, potentially derived from the remineralization of phytoplankton and dissolved organic nitrogen. Nutrient concentrations and flow speeds varied between the major benthic communities (coral reef and seagrass), resulting in spatial variability in estimated nitrate uptake rates. Rapid changes in flow speed and water depth are key characteristics of tide-dominated reefs, which caused mass-transfer-limited nutrient uptake rates to vary by an order of magnitude on time scales of ~minutes–hours. Seasonal nutrient supply was also a strong control on reef mass-transfer-limited uptake rates, and increases in offshore dissolved inorganic nitrogen concentrations during the wet season caused an estimated twofold increase in uptake.

scholarly journals Technical Note: A comparison of two empirical approaches to estimate in-stream net nutrient uptake

2011 ◽  
Vol 8 (4) ◽  
pp. 875-882 ◽  
Author(s):  
D. von Schiller ◽  
S. Bernal ◽  
E. Martí
Keyword(s):  
Mass Balance ◽  
Nutrient Uptake ◽  
Nutrient Concentrations ◽  
Nutrient Loads ◽  
Data Set ◽  
Advantages And Disadvantages ◽  
Balance Approach ◽  
Uptake Rates ◽  
Empirical Approaches ◽  
Mass Balance Approach

Abstract. To establish the relevance of in-stream processes on nutrient export at catchment scale it is important to accurately estimate whole-reach net nutrient uptake rates that consider both uptake and release processes. Two empirical approaches have been used in the literature to estimate these rates: (a) the mass balance approach, which considers changes in ambient nutrient loads corrected by groundwater inputs between two stream locations separated by a certain distance, and (b) the spiralling approach, which is based on the patterns of longitudinal variation in ambient nutrient concentrations along a reach following the nutrient spiralling concept. In this study, we compared the estimates of in-stream net nutrient uptake rates of nitrate (NO3) and ammonium (NH4) and the associated uncertainty obtained with these two approaches at different ambient conditions using a data set of monthly samplings in two contrasting stream reaches during two hydrological years. Overall, the rates calculated with the mass balance approach tended to be higher than those calculated with the spiralling approach only at high ambient nitrogen (N) concentrations. Uncertainty associated with these estimates also differed between both approaches, especially for NH4 due to the general lack of significant longitudinal patterns in concentration. The advantages and disadvantages of each of the approaches are discussed.

Source water inputs and catchment characteristics regulate limnological conditions of shallow subarctic lakes (Old Crow Flats, Yukon, Canada)

2015 ◽  
Vol 72 (7) ◽  
pp. 1058-1072 ◽  
Author(s):  
Ann M. Balasubramaniam ◽  
Roland I. Hall ◽  
Brent B. Wolfe ◽  
Jon N. Sweetman ◽  
Xiaowa Wang
Keyword(s):  
Major Ions ◽  
Nutrient Concentrations ◽  
Source Water ◽  
Subarctic Lakes ◽  
Sparse Vegetation ◽  
Evaporative Concentration ◽  
Tall Shrub ◽  
Strong Control ◽  
Old Crow Flats ◽  
Source Waters

Climate variations exert rapid and strong control on the hydrology of shallow lake-rich subarctic landscapes, but knowledge of the associated effects on limnological conditions remains limited. Based on analysis of water isotope compositions and water chemistry at 56 lakes across Old Crow Flats (Yukon), a large thermokarst landscape, we assess if differences in source water inputs (snowmelt versus rainfall) affect limnological conditions during the ice-free season of 2007 and explore influences of catchment features. Results demonstrate that lakes with snowmelt-dominated source waters, situated in catchments that support tall shrub and woodland vegetation, possess significantly higher (p < 0.05) nutrient (N, P, SiO2) and dissolved organic carbon concentrations than lakes with rainfall-dominated source waters. Conversely, rainfall-dominated lakes, located in catchments dominated by dwarf shrubs and sparse vegetation, have significantly higher concentrations of major ions (Mg2+, Na+, SO42−) and pH. These limnological differences persisted throughout the ice-free season. We suggest that interaction of snowmelt with organic-rich detritus raises nutrient concentrations in snowmelt-dominated lakes and that evaporative-concentration, shoreline erosion and possibly rainfall runoff are processes that raise the ionic content of lakes with rainfall-dominated source waters. Knowledge of these relations improves the ability to anticipate limnological responses to ongoing and future climate and hydrological change in Arctic and subarctic regions.

Availability of nitrogen and phosphorus in the forest floors of Rocky Mountain coniferous forests

1992 ◽  
Vol 22 (4) ◽  
pp. 593-600 ◽  
Author(s):  
Cindy E. Prescott ◽  
John P. Corbin ◽  
Dennis Parkinson
Keyword(s):  
Forest Floor ◽  
Lodgepole Pine ◽  
Ammonium Phosphate ◽  
Nutrient Supply ◽  
Nutrient Concentrations ◽  
Supply Rate ◽  
Nitrogen And Phosphorus ◽  
Forest Floors ◽  
P Supply ◽  
Floor Material

Nutrient supply rate and limitation were measured in forest floors of lodgepole pine, white spruce–lodgepole pine, and Engelmann spruce–subalpine fir (pine, spruce, and fir forests, respectively) forests in the Kananaskis Valley of southwestern Alberta. Earlier analyses of the nutrient content of foliage and litter indicated low N and P supply in the pine forest, high P supply in the spruce forest, and high N–low P supply in the fir forest. Measurements of nutrient supply (insitu rates of net mineralization, extractable P, and uptake of N and P from the forest floor in pot trials) confirmed the differences in N and P supply among the forests and indicated that nutrient concentrations in needle litter were useful as an index of nutrient supply rate. Subtractive tests were useful in identifying the most limiting nutrients in each forest: lodgepole pine seedlings grown in forest floor material from the pine and spruce stands responded with increased growth to the addition of N; those in fir forest floor material responded to P addition. Vector analysis of N and P concentrations and contents in needles from trees fertilized with ammonium phosphate sulphate showed responses to both N and P in the pine site, no response at the spruce site, and response to P at the fir site.

scholarly journals 245 EFFECTS OF PLANT AGE AND CONSTANT NUTRIENT SUPPLY ON POTATO LEAF ELEMENTAL COMPOSITION

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 464f-464
Author(s):  
W.L. Berry ◽  
R.M. Wheeler ◽  
C.L. Mackowiak ◽  
G.W. Stutte ◽  
J.C. Sager
Keyword(s):  
Growth And Development ◽  
Root Zone ◽  
Leaf Tissue ◽  
Nutrient Supply ◽  
Nutrient Concentrations ◽  
Controlled Environment ◽  
Critical Levels ◽  
Potato Leaf ◽  
Elemental Concentrations ◽  
Complete Nutrient Solution

Critical levels of nutrients in leaf tissue are influenced by plant metabolism, environment, and nutrient availability. In this study, we measured the elemental concentrations in fully expanded, upper canopy potato (Solunum tuberosum cv. Norland) leaves throughout growth and development in a controlled environment. Plants were grown hydroponically (NFT) in NASA's Biomass Production Chamber using a complete nutrient solution with the electrical conductivity maintained continuously at 0.12 S m-1. Photoperiod and air and root zone temperatures were changed midseason to promote tuberization, while CO2 levels were maintained at 1000 μmol mol-1 throughout growth. During vegetative growth, leaf nutrient concentrations remained relatively constant, except for a decline in Ca. During tuber enlargement and plant maturation, overall nutrient uptake decreased. Concentrations of the less mobile nutrients such as Ca, Mg, and B increased in the leaf tissue during mature growth, but somewhat surprisingly, highly mobile K also increased. Leaf concentrations of P, Zn, and Cu decreased during maturation.

scholarly journals Bacterial chemotaxis to saccharides is governed by a trade-off between sensing and uptake

2021 ◽  
Author(s):  
Noele Norris ◽  
Uria Alcolombri ◽  
Johannes M Keegstra ◽  
Yutaka Yawata ◽  
Filippo Menolascina ◽  
...  
Keyword(s):  
Bacterial Chemotaxis ◽  
Nutrient Concentrations ◽  
Trade Off ◽  
Agent Based ◽  
E Coli ◽  
High Affinity ◽  
Cytoplasmic Transport ◽  
Uptake Rates ◽  
Methyl Aspartate ◽  
Microfluidic Assays

To swim up gradients of nutrients, E. coli senses nutrient concentrations within its periplasm. For small nutrient molecules, periplasmic concentrations typically match extracellular concentrations. However, this is not necessarily the case for saccharides, such as maltose, which is transported into the periplasm via a specific porin. Previous observations have shown that under various conditions E. coli limits maltoporin abundance so that, for extracellular micromolar concentrations of maltose, there are predicted to be only nanomolar concentrations of free maltose in the periplasm. Thus, in the micromolar regime, the total uptake of maltose from the external environment into the cytoplasm is limited not by the abundance of cytoplasmic transport proteins but by the abundance of maltoporins. Here we present results from experiments and modeling showing that this porin-limited transport enables E. coli to sense micromolar gradients of maltose despite having a high-affinity ABC transport system that is saturated at these micromolar levels. We used microfluidic assays to study chemotaxis of E. coli in various gradients of maltose and methyl-aspartate and leveraged our experimental observations to develop a mechanistic transport-and-sensing chemotaxis model. Incorporating this model into agent-based simulations, we discover a trade-off between uptake and sensing: although high-affinity transport enables higher uptake rates at low nutrient concentrations, it severely limits dynamic sensing range. We thus propose that E. coli may limit periplasmic uptake to increase its chemotactic sensitivity, enabling it to use maltose as an environmental cue.

scholarly journals Influences of water deficiency on the productivity of young plants at different sites

2018 ◽  
pp. 371-378
Author(s):  
Katalin Sárdi
Keyword(s):  
Crop Production ◽  
Production Efficiency ◽  
Field Experiments ◽  
Nutrient Supply ◽  
Limiting Factors ◽  
Nutrient Concentrations ◽  
Growth Stages ◽  
Water Deficiency ◽  
Negative Effects ◽  
Site Characteristics

Water deficiency has become one of the most limiting factors of crop production in Hungary as the tendency in annual amounts of precipitation shows a decreasing tendency; therefore, it has become similar to those of Southern Europe. The most significant decrease in precipitation occurs typically during spring, approximately 20% of the data expressed in the averages of the last century. Studying the relationship between water deficiency as a stress factor and nutrient supply is important in order to improve the production efficiency of crops. Nowadays, this problem receives outstanding attention presented in numerous papers both in Hungary and globally, however, there are several questions yet to be answered. Our pot experiments were carried out under controlled greenhouse conditions in order to establish new data on these relationships. Experimental soils were typical for Western Transdanubia, taken from long-term field experiments representing four different site characteristics of the region. It was concluded from the results that drought periods during the early growth stages (i.e. 4–5 weeks after emergence) of plants may result in significant decreases in both dry matter production, nutrient concentrations, nutrient uptake and shoot:root ratios. Better nutrient supply, especially potassium, plays a significant role in reducing the negative effects of water deficiency.

scholarly journals Investigating equations for measuring dissolved inorganic nutrient uptake in oligotrophic conditions

2020 ◽  
Author(s):  
Michael R. Stukel
Keyword(s):  
Nutrient Uptake ◽  
Ecosystem Model ◽  
Ammonium Uptake ◽  
Nutrient Concentrations ◽  
Nutrient Regeneration ◽  
Isotope Tracer ◽  
Uptake Rates ◽  
Label Incorporation ◽  
Moderate Complexity

ABSTRACTMultiple different equations have been used to quantify nutrient uptake rates from stable isotope tracer label incorporation experiments. Each of these equations implicitly assumes an underlying model for phytoplankton nutrient uptake behavior within the incubation bottle and/or pelagic environment. However, the applicability of different equations remains in question and uncertainty arising from subjective choices of which equation to use is never reported. In this study, I use two approaches to investigate the conditions under which different nutrient uptake equations should be used. First, I utilized a moderate-complexity pelagic ecosystem model that explicitly models the δ15N values of all model compartments (NEMURO+15N) to conduct simulated nitrate uptake and ammonium uptake incubations and quantify the accuracy of different nutrient uptake equations. Second, I used results of deckboard diel nutrient uptake experiments to quantify the biases of 24-h incubations relative to six consecutive 4-h incubations. Using both approaches, I found that equations that account for nutrient regeneration (i.e., isotope dilution) are more accurate than equations that do not, particularly when nutrient concentrations are low but uptake is relatively high. Furthermore, I find that if the goal is to estimate in situ uptake rates it is appropriate to use an in situ correction to standard equations. I also present complete equations for quantifying uncertainty in nutrient uptake experiments using each nutrient uptake equation and make all of these calculations available as Excel spreadsheets and Matlab scripts.

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