Silicon Contamination in Diatom Nutrient Enrichment Experiments

1983 ◽  
Vol 40 (5) ◽  
pp. 657-664 ◽  
Author(s):  
Stephen J. Tarapchak ◽  
David R. Slavens ◽  
Michael A. Quigley ◽  
Judith S. Tarapchak
Keyword(s):  
Growth Rates ◽  
Nutrient Enrichment ◽  
Lake Michigan ◽  
Pyrex Glass ◽  
Short Term ◽  
Photosynthetic Rates ◽  
Nutrient Bioassay ◽  
Enrichment Experiments ◽  
Silicon Contamination

Large amounts of biologically available silicon (Si) were released into solution from the walls of Pyrex glass reagent bottles and Erlenmeyer flasks during nutrient bioassay experiments using Lake Michigan water. Photosynthetic rates in short-term (4–7 h) incubations and diatom growth rates and maximum yields in long-term incubations (~7 d) were affected by these extraneous Si supplies. The results of conventional nutrient enrichment bioassays performed in low-Si environments can be seriously biased unless Si contamination from glass incubation containers is avoided.

Phytoplankton responses to nutrient and grazer manipulations among northeastern lakes of varying pH

1998 ◽  
Vol 55 (4) ◽  
pp. 958-966 ◽  
Author(s):  
Paul Bukaveckas ◽  
William Shaw
Keyword(s):  
Phosphatase Activity ◽  
Nonlinear Model ◽  
Nutrient Enrichment ◽  
Grazing Intensity ◽  
Short Term ◽  
Good Correspondence ◽  
Acidic Lakes ◽  
P Limitation ◽  
Community Grazing ◽  
Enrichment Experiments

Short-term nutrient enrichment and zooplankton exclosure experiments were conducted at 14 lakes representing various stages of acidification (pH 4.6-6.8). We measured changes in chlorophyll as an indicator of the severity of nutrient limitation and grazing intensity and compared these with independent measures of P limitation (cell P quotas and phosphatase activity) and grazing (zooplankton densities and inferred community grazing rates). Results from nutrient enrichment experiments showed good correspondence to measured phosphatase activity but not cell P quotas. Phytoplankton in acidic lakes (pH < 5.0) responded more strongly to nutrient enrichment and exhibited fourfold higher biomass-specific phosphatase activity compared with nonacidic lakes. Phytoplankton responses to the removal of macrozooplankton did not exhibit any consistent pattern among lakes of varying acidity. Although the largest herbivores (Daphnia) were more abundant in nonacidic lakes, their absence in acidic lakes was compensated for by increased abundance of smaller species (principally Diaptomus minutus and Bosmina longirostris). The magnitude of the response to grazer removal was positively correlated with lake zooplankton densities at the time of the experiment, and the use of a nonlinear model enabled us to explain 84% of the variation in this response among the 14 sites.

scholarly journals Effects of Bisphosphonates on Osseointegration of Dental Implants in Rabbit Model

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Ru Qing Yu ◽  
Jing Yi Wang ◽  
Nian Jing Rao ◽  
Lei Huo ◽  
Li Wu Zheng
Keyword(s):  
Zoledronic Acid ◽  
Dental Implants ◽  
Dental Implant ◽  
Growth Rates ◽  
Acid Treatment ◽  
Bone Growth ◽  
Rabbit Model ◽  
Short Term ◽  
Calvarial Bone

This study is to investigate the effect of bisphosphonates on the osseointegration of dental implants in a rabbit model. Twenty female New Zealand White rabbits were equally assigned into control and experiment groups which received saline or zoledronic acid treatment 4 weeks prior to surgery. Titanium dental implant was placed on the calvarial bone. Zoledronic acid or saline treatment continued after surgery for 4 weeks (short-term subgroup) or 8 weeks (long-term subgroup) until sacrifice. Three different fluorochrome labeling solutions were administrated for assessing bone growth rates. Samples of the calvarial bone and mandible were subjected to microcomputed tomography (micro-CT), confocal microscope, and histology analysis. Zoledronic acid treatment significantly reduced bone growth rates in the calvarial bone, but had no significant influence in bone mineral density and trabecular microarchitecture. Significantly lower bone-to-implant contact ratios were found in zoledronic acid-treated animals compared to controls at week 4 but not at week 8. Oncologic dose zoledronic acid suppresses the bone growth rates of the calvarial bone; ZA may have an adverse effect on osseointegration of dental implant in short term, but this effect tends to diminish in long term.

scholarly journals Hyper-Nutrient Enrichment Status in the Sabalan Lake, Iran

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2874
Author(s):  
Roohollah Noori ◽  
Elmira Ansari ◽  
Yong-Wook Jeong ◽  
Saber Aradpour ◽  
Mohsen Maghrebi ◽  
...  
Keyword(s):  
Nutrient Enrichment ◽  
Management Practices ◽  
Storage Capacity ◽  
Limiting Factors ◽  
Molar Ratio ◽  
Anthropogenic Factors ◽  
Short Term ◽  
Reservoir Water ◽  
P Deficiency

Lakes/reservoirs are rapidly deteriorating from cultural eutrophication due to anthropogenic factors. In this study, we aimed to (1) explore nutrient levels in the Sabalan dam reservoir (SDR) of northwest Iran, (2) determine the reservoir water fertility using the total phosphorus (TP)based and total nitrogen (TN)based Carlson trophic state indices, and (3) specify primary limiting factors for the reservoir eutrophication. Our field observations showed a state of hyper-nutrient enrichment in the SDR. The highest variation of TN in the reservoir water column happened when the reservoir was severely stratified (in August) while the highest variation of TP took place when the thermocline was attenuated with the deepening of the epilimnion (in October). Both TP and TN based trophic indicators classified the SDR as a hypereutrophic lake. TN:TP molar ratio averaged at the epilimnion indicated a P–deficiency in the reservoir during warm months whilst it suggested a co–deficiency of P and N in cold months. Given the hyper-nutrient enrichment state in the reservoir, other drivers such as water residence time (WRT) can also act as the main contributor of eutrophication in the SDR. We found that WRT in the SDR varied from hundreds to thousands of days, which was much longer than that of other reservoirs/lakes with the same and even much greater storage capacity. Therefore, both hyper-nutrient enrichment and WRT mainly controlled eutrophication in the reservoir. Given time consuming and expensive management practices for reducing nutrients in the watershed, changes in the SDR operation are suggested to somewhat recover its hypereutrophic state in the short-term. However, strategic long-term recovery plans are required to reduce the transition of nutrients from the watershed to the SDR.

scholarly journals Short-term relative invader growth rate predicts long-term equilibrium proportion in a stable, coexisting microbial community

2020 ◽  
Author(s):  
Daniel Padfield ◽  
Meaghan Castledine ◽  
Joseph Pennycook ◽  
Elze Hesse ◽  
Angus Buckling
Keyword(s):  
Growth Rate ◽  
Microbial Community ◽  
Relative Abundance ◽  
Growth Rates ◽  
Community Dynamics ◽  
Species Coexistence ◽  
Short Term ◽  
Long Term Culture ◽  
Modelling Approach

AbstractThe ability of species to mutually invade from rare is the defining measure of species coexistence. However, it is unknown whether invasion growth rates predict any characteristic of long-term community dynamics. Here, we use a model five-species microbial community to investigate the link between short-term growth rate and long-term relative abundance. We manipulated diversity and tested the ability of species to coexist in different combinations. Across all diversity levels and species combinations, populations re-established from rare in 71 of 75 combinations and all combinations were stable in long-term culture. Moreover, short-term relative invader growth rate was positively associated with long-term equilibrium proportion, despite large variation in interactions between species and communities. This finding was confirmed using a modelling approach and suggests that the short-term invasion growth rate can predict long-term relative abundance within that community.

Ammonium and nitrate uptake lengths in a small forested stream determined by 15N tracer and short-term nutrient enrichment experiments

2000 ◽  
Vol 27 (3) ◽  
pp. 1320-1325
Author(s):  
Patrick J. Mulholland ◽  
Jennifer L. Tank ◽  
Diane M. Sanzone ◽  
Jackson R. Webster ◽  
Wilfred M. Wollheim ◽  
...  
Keyword(s):  
Nutrient Enrichment ◽  
Nitrate Uptake ◽  
15N Tracer ◽  
Short Term ◽  
Forested Stream ◽  
Enrichment Experiments

THE CAUSE OF HIGHER ECONOMIC GROWTH: ASSESSING THE LONG-TERM AND SHORT-TERM RELATIONSHIPS BETWEEN ECONOMIC GROWTH AND GOVERNMENT EXPENDITURE

2014 ◽  
Vol 20 (1) ◽  
pp. 229-250 ◽  
Author(s):  
Motasam Tatahi ◽  
Emre Ipekci Cetin ◽  
M. Koray Cetin
Keyword(s):  
Economic Growth ◽  
Growth Rate ◽  
Growth Rates ◽  
Government Expenditure ◽  
Government Expenditures ◽  
Gdp Growth ◽  
Short Term ◽  
Data Set ◽  
Dynamic Relationship

This study examines the cause of higher (5% or more) economic growth rates in countries around the world over the past 35 years. It explores the long- and short-term relationships between GDP and government expenditures in these countries. A panel data set of 60 countries over the period from 1976 to 2010 is deployed to implement pooled mean group estimation. Countries are divided into three economic growth rate groups: high, middle, and low. Panel-based/error correction models are used to estimate long-term equilibrium relationships and short-term dynamics between government expenditures and GDP growth rates. Results indicate that the hypothesis of a common long-term elasticity and a short-term dynamic relationship between GDP growth rates and government expenditures cannot be rejected for high group countries, whereas for middle group countries this is true only for the long term, not for the short term. No long-term or short-term relationship between these two variables exists for low-growth-rate countries.

Periphyton response to long-term nutrient enrichment in a shaded headwater stream

2005 ◽  
Vol 62 (9) ◽  
pp. 2033-2045 ◽  
Author(s):  
Jennifer L Greenwood ◽  
Amy D Rosemond
Keyword(s):  
Growth Rates ◽  
Nutrient Enrichment ◽  
Algal Species ◽  
Light Availability ◽  
Algal Growth ◽  
Detectable Effect ◽  
Long Term Effects ◽  
Tree Canopies ◽  
Periphyton Biomass

We maintained elevated but moderate concentrations of nitrogen and phosphorus continuously for 2 years in a heavily shaded headwater stream and compared effects on stream periphyton with a reference stream. Both streams were sampled for 1 year before treatment. Some measures of periphyton biomass (ash-free dry mass and chlorophyll a) responded positively to enrichment. Increased chlorophyll a was likely a result of higher chlorophyll per cell, as total algal biovolume did not change with enrichment. These differences were greatest during high-light months (November-May), when cellular growth rates (a proxy for production) were also highest with enrichment. Algal assemblages were dominated by diatoms and remained similar between the treatment and reference streams throughout the enrichment period. Although nutrients stimulated algal growth rates, the long-term effects of nutrient addition on periphyton biomass were small in magnitude compared with other published values and were potentially suppressed by light availability and invertebrate consumption. These and other factors may have also been important in limiting the algal species pool and thus a taxonomic response to enrichment. Our results indicate that in headwater streams with intact tree canopies, chronic nutrient enrichment at moderate concentrations may have little detectable effect on benthic algal composition or periphyton biomass. Although nutrients stimulated algal growth rates, the long-term effects of nutrient addition on periphyton biomass were small in magnitude compared with other published values and were potentially suppressed by light availability and invertebrate consumption. These and other factors may have also been important in limiting the algal species pool and thus a taxonomic response to enrichment. Our results indicate that in headwater streams with intact tree canopies, chronic nutrient enrichment at moderate concentrations may have little detectable effect on benthic algal composition or periphyton biomass.

Spring isothermal mixing in the Great Lakes: evidence of nutrient limitation and nutrient-light interactions in a suboptimal light environment

2000 ◽  
Vol 57 (9) ◽  
pp. 1901-1910 ◽  
Author(s):  
G L Fahnenstiel ◽  
R A Stone ◽  
M J McCormick ◽  
C L Schelske ◽  
S E Lohrenz
Keyword(s):  
Great Lakes ◽  
Growth Rates ◽  
Nutrient Enrichment ◽  
Light Availability ◽  
Light Limitation ◽  
Phytoplankton Communities ◽  
Growth Irradiance ◽  
Enrichment Experiments ◽  
Isothermal Mixing

During the spring isothermal mixing period (April-May) in 1993-1995, photosynthesis-irradiance and growth-irradiance experiments were conducted in Lakes Erie, Huron, Michigan, and Ontario to assess light limitation. Additionally, nutrient enrichment experiments were conducted in Lake Ontario. Results from the photosynthesis-irradiance experiments suggested that phytoplankton communities in all the lakes can be either light limited or light saturated, as the threshold parameter (Ik) was similar to mean water column irradiances (mean Iwc, ratio = 1.0). Growth-irradiance experiments also suggested the potential for light saturation; mean daily irradiance exceeded the threshold growth irradiance (Ik,g) in 95% of cases. Growth rates became light saturated at lower irradiances than photosynthetic rates. Evidence for a nutrient-light interaction in controlling in situ growth rates was also found in the nutrient enrichment experiments at incubation irradiances [Formula: see text] mean Iwc. Our results suggest that an interaction between nutrients and light is often controlling phytoplankton growth during spring mixing in the Great Lakes. The role of these nutrient-light interactions has increased in the past decade due to increased light availability in the lower lakes caused by phosphorus load reductions and the filtering activities of nonindigenous mussels.

Short- and long-term effects of irradiance and CO2 availability on carbon fixation by two marine diatoms

2003 ◽  
Vol 81 (3) ◽  
pp. 191-200 ◽  
Author(s):  
Ana Bartual ◽  
J Angel Gálvez
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Carbon Fixation ◽  
Skeletonema Costatum ◽  
Light Limitation ◽  
Long Term Effects ◽  
Short Term ◽  
Batch Cultures ◽  
Photosynthetic Rates ◽  
Long Term Trends

Unbuffered and nutrient-replete dilute batch cultures of Skeletonema costatum Cleve and Phaeodactylum tricornutum Bohlin were grown at high and low CO2 availability conditions and two incident irradiances, 150 and 30 µmol photons·m–2·s–1. Long-term combined effects of such light and CO2 availability conditions on carbon fixation rates of both diatoms were compared. At saturating light, P. tricornutum showed higher photosynthetic rates than S. costatum at both CO2 conditions. However, under subsaturating light, carbon fixation rates of P. tricornutum were higher than observed for S. costatum only at low CO2. Skeletonema costatum showed a strong reduction in photosynthetic rates only when both resources, irradiance and CO2, were low. Short-term alterations of light and CO2 availability on carbon fixation showed that the response of S. costatum differed considerably from long-term trends: the short-term reduction in CO2 availability at both light levels resulted in a considerable decrease in the maximum photosynthetic rates. This effect was much less noticeable in P. tricornutum. The results show that, at saturating light, both diatoms maintain maximum photosynthetic rates under low CO2 levels, but only P. tricornutum is well adapted to rapid changes in this resource. This capacity of adaptation seems to be light dependent, since light limitation altered the responses of both diatoms to low CO2 availability conditions.Key words: CO2, 14C fixation, irradiance, Phaeodactylum tricornutum, Skeletonema costatum.

Stochastic Investment Modelling: The Case of South Africa

1996 ◽  
Vol 2 (3) ◽  
pp. 765-801 ◽  
Author(s):  
R.J. Thomson
Keyword(s):  
South Africa ◽  
Time Series ◽  
Interest Rates ◽  
South African ◽  
Growth Rates ◽  
Time Series Models ◽  
Short Term ◽  
Model Based ◽  
Inflation Rates

ABSTRACTThe purpose of this paper is to describe a methodology for determining an appropriate structure for time-series models of inflation rates, short-term and long-term interest rates, dividend growth rates, dividend yields, rental growth rates and rental yields and to demonstrate the application of that methodology to the development of a model based on South African data. It is suggested that the methodology used in this paper may be applied to other economic environments.

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