Name: understanding dissolved organic matter biogeochemistry through in situ nutrient manipulations in stream ecosystems
Uploaded: 2016-10-29T15:00:00
Description: Watch this Scientific Journal Video about Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems at JoVE.com

The authors acknowledge the Water Quality Analysis Laboratory at the University of New Hampshire for assistance with sample analysis. The authors also thank two anonymous reviewers whose comments have helped to improve the manuscript. This work is funded by the National Science Foundation (DEB-1556603). Partial funding was also provided by the EPSCoR Ecosystems and Society Project (NSF EPS-1101245), New Hampshire Agricultural Experiment Station (Scientific Contribution #2662, USDA National Institute of Food and Agriculture (McIntire-Stennis) Project (1006760), the University of New Hampshire Graduate School, and the New Hampshire Water Resources Research Center.

1. Identifying and Characterizing the Ideal Experimental Stream Reach
<ol>
	<li>Ensure that experimental stream reaches are long enough to promote complete mixing of solutes11 and long enough where biological uptake can occur. Reach lengths can vary among streams and experiments. In small first-order headwater streams, reach length may vary from 20-150 m (or longer if the system requires it) depending on discharge and other physical properties of the stream.
	<ol>
		<li>Exclude large pools from experimental ...

<ol>
	<li>Brookshire, E. N. J., Valett, H. M., Thomas, S. A., Webster, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atmospheric+N+deposition+increases+organic+N+loss+from+temperate+forests.">Atmospheric N deposition increases organic N loss from temperate forests.</a> Ecosystems. 10 (2), 252-262 (2007).</li><li>Bernhardt, E. S., McDowell, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Twenty+years+apart:+Comparisons+of+DOM+uptake+during+leaf+leachate+releases+to+Hubbard+Brook+Valley+streams+in+1979+and+2000.">Twenty years apart: Comparisons of DOM uptake during leaf leachate releases to Hubbard Brook Valley streams in 1979 and 2000.</a> J Geophys Res. 113, G03032 (2008).</li><li>Taylor, P. G., Townsend, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stoichiometric+control+of+organic+carbon-nitrate+relationships+from+soils+to+sea.">Stoichiometric control of organic carbon-nitrate relationships from soils to sea.</a> Nature. 464, 1178-1181 (2010).</li><li>Mulholland, P. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stream+denitrification+across+biomes+and+its+response+to+anthropogenic+nitrate+loading.">Stream denitrification across biomes and its response to anthropogenic nitrate loading.</a> Nature. 452, 202-205 (2008).</li><li>Tank, J. L., Rosi-Marshall, E. J., Baker, M. A., Hall, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Are+rivers+just+big+streams?+A+pulse+method+to+quantify+nitrogen+demand+in+a+large+river.">Are rivers just big streams? A pulse method to quantify nitrogen demand in a large river.</a> Ecology. 89 (10), 2935-2945 (2008).</li><li>Covino, T. P., McGlynn, B. L., McNamara, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracer+additions+for+spiraling+curve+characterization+(TASCC):+quantifying+stream+nutrient+uptake+kinetics+from+ambient+to+saturation.">Tracer additions for spiraling curve characterization (TASCC): quantifying stream nutrient uptake kinetics from ambient to saturation.</a> Limnol Oceanogr. 8, 484-498 (2010).</li><li>Johnson, L. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+the+production+of+dissolved+organic+nitrogen+in+headwater+streams+using+15+N+tracer+additions.">Quantifying the production of dissolved organic nitrogen in headwater streams using 15 N tracer additions.</a> Limnol Oceanogr. 58 (4), 1271-1285 (2013).</li><li>Rosemond, A. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+nutrient+additions+accelerate+terrestrial+carbon+loss+from+stream+ecosystems.">Experimental nutrient additions accelerate terrestrial carbon loss from stream ecosystems.</a> Science. 347 (6226), 1142-1145 (2015).</li><li>Diemer, L. A., McDowell, W. H., Wymore, A. S., Prokushkin, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nutrient+uptake+along+a+fire+gradient+in+boreal+streams+of+Central+Siberia.">Nutrient uptake along a fire gradient in boreal streams of Central Siberia.</a> Freshwater Sci. 34 (4), 1443-1456 (2015).</li><li>Wymore, A. S., Rodr&#237;guez-Cardona, B., McDowell, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+response+of+dissolved+organic+nitrogen+to+nitrate+availability+in+headwater+streams.">Direct response of dissolved organic nitrogen to nitrate availability in headwater streams.</a> Biogeochemistry. 126 (1), 1-10 (2015).</li><li>Stream Solute Workshop. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concepts+and+methods+for+assessing+solute+dynamics+in+stream+ecosystems.">Concepts and methods for assessing solute dynamics in stream ecosystems.</a> J N Am Benthol Soc. 9 (2), 95-119 (1990).</li><li>Kilpatrick, F. A., Cobb, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Measurement of discharge using tracers: U.S Geological Survey Techniques of Water-Resources Investigations. , (1985).</li><li>Rodr&#237;guez-Cardona, B., Wymore, A. S., McDowell, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DOC:+NO3-+and+NO3-+uptake+in+forested+headwater+streams.">DOC: NO3- and NO3- uptake in forested headwater streams.</a> J Geophys Res - Biogeo. 121, (2016).</li><li>Kilpatrick, F. A., Wilson, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Book+3+Chapter+A9,+Measurement+of+time+of+travel+in+streams+by+dye+tracing.">Book 3 Chapter A9, Measurement of time of travel in streams by dye tracing.</a> Techniques of Water-Resources Investigations of the United States Geological Survey. , (1989).</li><li>Lutz, B. D., Bernhardt, E. S., Roberts, B. J., Mulholland, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Examining+the+coupling+of+carbon+and+nitrogen+cycles+in+Appalachian+streams:+the+role+of+dissolved+organic+nitrogen.">Examining the coupling of carbon and nitrogen cycles in Appalachian streams: the role of dissolved organic nitrogen.</a> Ecology. 92 (3), 720-732 (2011).</li><li>Michalzik, B., Matzner, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+dissolved+organic+nitrogen+and+carbon+in+a+Central+European+Norway+spruce+ecosystem.">Dynamics of dissolved organic nitrogen and carbon in a Central European Norway spruce ecosystem.</a> Eur J Soil Sci. 50 (4), 579-590 (1990).</li><li>Solinger, S., Kalbitz, K., Matzner, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controls+on+the+dynamics+of+dissolved+organic+carbon+and+nitrogen+in+a+Central+European+deciduous+forest.">Controls on the dynamics of dissolved organic carbon and nitrogen in a Central European deciduous forest.</a> Biogeochemistry. 55 (3), 327-349 (2001).</li><li>Kaushal, S. S., Lewis, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterns+in+chemical+fractionation+of+organic+nitrogen+in+Rocky+Mountain+streams.">Patterns in chemical fractionation of organic nitrogen in Rocky Mountain streams.</a> Ecosystems. 6 (5), 483-492 (2003).</li><li>Kaushal, S. S., Lewis, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fate+and+transport+of+organic+nitrogen+in+minimally+disturbed+montane+streams+of+Colorado,+USA.">Fate and transport of organic nitrogen in minimally disturbed montane streams of Colorado, USA.</a> Biogeochemistry. 74 (3), 303-321 (2005).</li></ol>

The objective of the nutrient pulse method, as presented here, is to characterize and quantify the response of the highly diverse pool of ambient stream water DOM across a dynamic range of an added inorganic nutrient. If the added solute sufficiently increases the concentration of the reactive solute, a large inferential space can be created to understand how the biogeochemical cycling of DOM is linked to nutrient concentrations. This nutrient pulse approach is ideal as it involves none of the machinery associated with p...

Dissolved organic matter (DOM) provides an important energy and nutrient source to freshwater ecosystems and is defined as organic matter that passes through a 0.7 &#181;m filter. Within aquatic ecosystems, DOM can also influence light attenuation and metal complexation. DOM is a highly diverse and heterogeneous mixture of organic compounds with various functional groups, as well as essential nutrients such as nitrogen (N) and phosphorous (P). While the term &#34;DOM&#34; describes the entire pool including its C, N and P components, its concentration is measured as dissolved organic carbon (DOC). The inherent molecular complexity of the DOM pool however, creates challenges to its study. For example, there is no direct way to measure the fraction of the total DOM pool comprised of organic nutrients such as dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP). Instead, the concentration of organic nutrients must be determined by difference (e.g. [DON] = [total dissolved nitrogen] - [dissolved inorganic nitrogen]).
Adding a realistic DOM amendment to a stream is difficult due to the diversity of the ambient DOM pool. Previous studies have added single carbon sources (e.g. glucose, urea1) or a particular source such as leaf litter leachate2 to manipulate concentrations in the field. However, these sources are not particularly representative of the ambient DOM pool. Trying to refine or concentrate ambient DOM for subsequent experimentation is also wrought with difficulties including the loss of certain fractions (e.g. highly labile components) during processing. As a result, it is difficult to understand the controls on the ambient DOM pool as we currently do not possess any method to directly manipulate the ambient DOM pool. However, since the biogeochemistry of DOM is linked to nutrients commonly found in the environment (e.g. nitrate [NO3-]3), we can add other solutes to stream ecosystems and measure the response of the DOM pool to these manipulations. By examining how the DOM pool responds to a wide range of experimentally imposed nutrient concentrations we hope to gain better insight into how DOM responds to fluctuating environmental conditions.
One method commonly used in stream biogeochemistry is the nutrient addition method. Nutrient addition experiments have traditionally been used to understand uptake kinetics or the fate of the added solute4,5,6,7. Nutrient additions can be short-term on the hr6 to day scale4, or longer-term manipulations over the course of multiple years8. Nutrient additions can also include isotopically labelled nutrients (e.g. 15N-NO3-) to trace added nutrient through biogeochemical reactions. However, isotope-based studies are often expensive and require challenging analyses (e.g. digestions) of the multiple benthic compartments where isotopically-labeled nutrients may be retained. Recent experimentation has revealed the utility of short-term nutrient pulses to elucidate the controls on non-added and ambient solutes such as DOM9,10, revealing a new way by which to examine real-time in situ biogeochemical reactions. Here we describe and demonstrate the key methodological steps to conducting short-term nutrient pulses with the objective of understanding the coupled biogeochemistry of C and N and specifically the controls on the highly diverse DOM pool. This easily reproducible method involves adding a nutrient pulse to an experimental stream reach and measuring changes in the concentration of both the manipulated solute and the response variable of interest (e.g. DOC, DON, DOP). By directly manipulating nutrient concentrations in situ we are able to indirectly alter the DOM pool and examine how DOM concentration changes across a dynamic range of nutrient concentrations10.

<table border="0" cellpadding="0" cellspacing="0" width="593">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium Nitrate</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium Chloride</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td>Store purchased table salt can be used as well, however, it does contain trace levels of impurities</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Whatman GFF glass-fiber filters</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">BD Filtering Syringe</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">EMD Millipore Swinnex Filter Holders</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Syringe stop-cock</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">YSI Multi-parameter probe</td>
			<td style="width:91px;">Yellow Springs International</td>
			<td>556-01</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Wide mouth HDPE 125 ml bottles</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">60 ml HDPE bottles</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">20 L bucket</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Field measuring tape</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Lab labeling tape</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stir stick</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cooler</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sharpie pen</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Field notebook</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tweezers</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Zip-lock bags</td>
			<td style="width:91px;">Any</td>
			<td style="width:119px;">Any</td>
			<td></td>
		</tr>
	</tbody>
</table>

understanding dissolved organic matter biogeochemistry through in situ nutrient manipulations in stream ecosystems

Dissolved organic matter (DOM) is a highly diverse mixture of molecules providing one of the largest sources of energy and nutrients to stream ecosystems. Yet the in situ study of DOM is difficult as the molecular complexity of the DOM pool cannot be easily reproduced for experimental purposes. Nutrient additions to streams however, have been shown to repeatedly alter the in situ and ambient DOM pool. Here we demonstrate an easily replicable field-based method for manipulating the ambient pool of DOM at the ecosystem scale. During nutrient pulse experiments changes in the concentration of both dissolved organic carbon and dissolved organic nitrogen can be examined across a wide-range of nutrient concentrations. This method allows researchers to examine the controls on the DOM pool and make inferences regarding the role and function that certain fractions of the DOM pool play within ecosystems. We advocate the use of this method as a technique to help develop a deeper understanding of DOM biogeochemistry and how it interacts with nutrients. With further development this method may help elucidate the dynamics of DOM in other ecosystems.

<img alt="Figure 3" src="/files/ftp_upload/54704/54704fig3.jpg" /> 
Figure 3: Example Results from Nitrate (NO3-) Additions with Dissolved Organic Nitrogen (DON) as the Response Variable. Analyses are linear regressions. Asterisks represent statistical significance at &#945; = 0.05. Note the dynamic range in NO3- concentration that was achieved with the nutrient pulse method. Different pane...

Watch this Scientific Journal Video about Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems at JoVE.com

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

Dissolved organic matter provides an important source of energy and nutrients to stream ecosystems. Here we demonstrate a field-based method to manipulate the ambient pool of dissolved organic matter in situ through easily replicable nutrient pulses.

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

Dissolved organic matter (DOM) is a highly diverse mixture of molecules providing one of the largest sources of energy and nutrients to stream ecosystems. ...

The overall goal of this nutrient pulse method is to indirectly manipulate the ambient pool of dissolved organic matter to understand how this pool of organic matter responds to changes in nutrient concentration. This method can help answer key questions in the stream biogeochemistry field, such as how organic matter and nutrient cycling are linked. The main advantage of this method is that it represents a whole ecosystem manipulation and can be easily replicated.The implications of this technique extend to watershed export of carbon and nitrogen as the interaction of these elements determines how they are retained within the stream. We first had the idea for this technique when we realized that the nutrient slug approach created a dynamic range of nutrient concentrations and that the concentrations of dissolved organic matter were sensitive to these changes. To begin, deploy the field conductivity meter, selecting a location approximately 0.5 to 1.0 meters upstream of the sample collection site.The meter will remain in place throughout the experiment. Next rinse acid-washed, high-density polyethylene bottles three times and use them to collect 125 milliliters of background grab samples in triplicate at the addition site and then at the collection site of the experimental reach. These are used to determine ambient concentrations prior to the addition of the solution.Record the instream background conductivity prior to the addition of solutes. Then record the time of collection and the conductivity of the collected background samples. First collect stream water with a large container.Then add all of the reagents and ensure that the solutes are completely dissolved. Keep track of the amount of water added. Rinse the reagent vessels three times with additional stream water and pour the rinse into the solution container.Stir the solution with a clean stir stick until all the reagents have dissolved. Label a 60 milliliter high-density, polyethylene bottle appropriately and into it, collect the 60 milliliter aliquot of the addition solution. Store it separately from other samples to avoid contamination.Next, pour the sample into the addition site in a smooth and quick motion to minimize travel lag time and to avoid splashing. Immediately rinse the container and stir the stick in the stream three times to release all reagents. Record the time in hours, minutes, and seconds.Record the masses of tracers added, alongside the time of release and take care not to disturb the stream benthos or solution until the conclusion of the experiment. At the collection site, first order labeled sampling bottles in ascending order while waiting for the solution. Use the field conductivity meter to take readings at the collection site.Arrival of the solution will be detected by an increase in conductivity. Once solution arrival has been detected, take a clean 125 milliliter bottle and rinse it in the stream water. Discard the rinse downstream of the sampling site, and then collect the sample by holding the bottle into the main flow of the water at the sampling point.Repeat this collection process, using one new bottle after another throughout the passage of the solution, and record the collection time and conductivity of each sample. Continue sampling until conductivity returns to within five microsiemens per centimeter of background level. Cap the samples and store them in a cooler.First arrange the samples for filtration so that the rising lim is filtered in ascending specific conductivity until the peak. Next arrange the falling lim samples to be filtered in ascending order of specific conductivity. To filter samples, take a 60 milliliter syringe, remove the plunger and then close the stopcock.Pour around 10 milliliters of sample into the syringe and replace the plunger. Shake the syringe so the sample rinses the internal walls. Next, attach a filter holder to the syringe and open the stopcock.Push the sample through the filter by depressing the plunger and discard the rinse. Remove the plunger and close the stopcock. This time, pour 30 milliliters of the same sample into the syringe and replace the plunger.With the syringe positioned to expel into a clean 60 milliliter sample bottle, open the stopcock and push around 10 milliliters through the filter. Cap the bottle, swirl it, and discard the filtrate. Repeat three times to ensure impurities are removed from the bottle and the walls are coated with sample.Remove the plunger again and close the stopcock. Pour around a 60 milliliter sample into the syringe and replace the plunger. Push the sample through the filter holder into the 60 milliliter sample bottle.Filling bottles no higher than the shoulder, cap the bottles and place the samples into a cooler. Finally, analyze samples for dissolved organic carbon and nitrogen and any other parameters of interest in order of low to high conductivity. These plots are linear regressions of measurements of dissolved organic nitrogen concentrations, or DON, after addition of nitrate via the pulse method.Results show that dissolved organic nitrogen concentrations change in response to nitrate addition. Variation in the response of dissolved organic nitrogen was also observed within sites at different sampling times, which suggests that aquatic microbial communities may be using different components of the dissolved organic matter at different times of the growing season. Positive correlations are interpreted to reflect dissolved organic nitrogen's role as a nutrient source, while negative correlations are interpreted to reflect dissolved organic nitrogen acting as an energy source.Experiments that showed non-significant relationships reflect a non-responsive DON pool or one in which the nutrient-based processes and energy-based processes are off-setting. Here, the plots show linear regressions of dissolved organic carbon, or DOC, after nitrate addition. Contrary to the DON plots, these show few instances of significant changes in the DOC concentration due to nitrate addition.This may indicate that the nitrogen-rich and carbon-rich fractions of the dissolved organic matter pool have their own particular set of ecological and biogeochemical controls and that the ambient pool of DOC is highly recalcitrant. Once mastered, this technique can take between three to six hours depending on the system. While performing this method, it is important to avoid contamination of low conductivity samples by high conductivity samples.Following this procedure, other methods, such as nutrient uptake connectics can be calculated to determine how the rate and flux of nutrient uptake determines the concentrations of dissolved organic carbon and dissolved organic nitrogen. After its development, this technique paved the way for researchers in the field of aquatic biogeochemistry to explore the controls on nutrient retention within stream ecosystems. Although this method can provide insights into stream nutrients cycling, it can potentially be applied to other environments, such as groundwater and estuarine systems.After watching this video, you should have a good understanding of how to perform nutrient addition experiments in headwater stream ecosystems.

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