Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river
Anthropogenic alteration of the form and concentration of nitrogen (N) in aquatic ecosystems is widespread. Understanding availability and uptake of different N sources at the base of aquatic food webs is critical to establishment of effective nutrient management programs. Stable isotopes of N (...
Main Authors: | , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-01-01
|
Series: | Biogeosciences |
Online Access: | https://www.biogeosciences.net/15/353/2018/bg-15-353-2018.pdf |
id |
doaj-4e6d8841efb046c983b0039269d93a78 |
---|---|
record_format |
Article |
spelling |
doaj-4e6d8841efb046c983b0039269d93a782020-11-24T22:59:32ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-01-011535336710.5194/bg-15-353-2018Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich riverC. M. Schmidt0T. E. C. Kraus1M. B. Young2C. Kendall3University of San Francisco, 2130 Fulton St, San Francisco, CA 94117, USAUSGS California Water Science Center, 6000 J Street, Placer Hall, Sacramento, CA 95819, USAUSGS National Research Program, 345 Middlefield Rd, Menlo Park, CA 94025, USAUSGS National Research Program, 345 Middlefield Rd, Menlo Park, CA 94025, USAAnthropogenic alteration of the form and concentration of nitrogen (N) in aquatic ecosystems is widespread. Understanding availability and uptake of different N sources at the base of aquatic food webs is critical to establishment of effective nutrient management programs. Stable isotopes of N (<sup>14</sup>N, <sup>15</sup>N) are often used to trace the sources of N fueling aquatic primary production, but effective use of this approach requires obtaining a reliable isotopic ratio for phytoplankton. In this study, we tested the use of flow cytometry to isolate phytoplankton from bulk particulate organic matter (POM) in a portion of the Sacramento River, California, during river-scale nutrient manipulation experiments that involved halting wastewater discharges high in ammonium (NH<sub>4</sub><sup>+</sup>). Field samples were collected using a Lagrangian approach, allowing us to measure changes in phytoplankton N source in the presence and absence of wastewater-derived NH<sub>4</sub><sup>+</sup>. Comparison of <i>δ</i><sup>15</sup>N-POM and <i>δ</i><sup>15</sup>N-phytoplankton (<i>δ</i><sup>15</sup>N-PHY) revealed that their <i>δ</i><sup>15</sup>N values followed broadly similar trends. However, after 3 days of downstream travel in the presence of wastewater treatment plant (WWTP) effluent, <i>δ</i><sup>15</sup>N-POM and <i>δ</i><sup>15</sup>N-PHY in the Sacramento River differed by as much as 7 ‰. Using a stable isotope mixing model approach, we estimated that in the presence of effluent between 40 and 90 % of phytoplankton N was derived from NH<sub>4</sub><sup>+</sup> after 3 days of downstream transport. An apparent gradual increase over time in the proportion of NH<sub>4</sub><sup>+</sup> in the phytoplankton N pool suggests that either very low phytoplankton growth rates resulted in an N turnover time that exceeded the travel time sampled during this study, or a portion of the phytoplankton community continued to access nitrate even in the presence of elevated NH<sub>4</sub><sup>+</sup> concentrations.https://www.biogeosciences.net/15/353/2018/bg-15-353-2018.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
C. M. Schmidt T. E. C. Kraus M. B. Young C. Kendall |
spellingShingle |
C. M. Schmidt T. E. C. Kraus M. B. Young C. Kendall Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river Biogeosciences |
author_facet |
C. M. Schmidt T. E. C. Kraus M. B. Young C. Kendall |
author_sort |
C. M. Schmidt |
title |
Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river |
title_short |
Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river |
title_full |
Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river |
title_fullStr |
Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river |
title_full_unstemmed |
Use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river |
title_sort |
use of flow cytometry and stable isotope analysis to determine phytoplankton uptake of wastewater derived ammonium in a nutrient-rich river |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2018-01-01 |
description |
Anthropogenic alteration of the form and concentration of nitrogen (N) in
aquatic ecosystems is widespread. Understanding availability and uptake of
different N sources at the base of aquatic food webs is critical to
establishment of effective nutrient management programs. Stable isotopes of N
(<sup>14</sup>N, <sup>15</sup>N) are often used to trace the sources of N fueling aquatic
primary production, but effective use of this approach requires obtaining a
reliable isotopic ratio for phytoplankton. In this study, we tested the use
of flow cytometry to isolate phytoplankton from bulk particulate organic
matter (POM) in a portion of the Sacramento River, California, during
river-scale nutrient manipulation experiments that involved halting
wastewater discharges high in ammonium (NH<sub>4</sub><sup>+</sup>). Field samples were
collected using a Lagrangian approach, allowing us to measure changes in
phytoplankton N source in the presence and absence of wastewater-derived
NH<sub>4</sub><sup>+</sup>. Comparison of <i>δ</i><sup>15</sup>N-POM and
<i>δ</i><sup>15</sup>N-phytoplankton (<i>δ</i><sup>15</sup>N-PHY) revealed that their
<i>δ</i><sup>15</sup>N values followed broadly similar trends. However, after 3 days
of downstream travel in the presence of wastewater treatment plant (WWTP)
effluent, <i>δ</i><sup>15</sup>N-POM and <i>δ</i><sup>15</sup>N-PHY in the Sacramento River
differed by as much as 7 ‰. Using a stable isotope mixing model
approach, we estimated that in the presence of effluent between 40 and
90 % of phytoplankton N was derived from NH<sub>4</sub><sup>+</sup> after 3 days of
downstream transport. An apparent gradual increase over time in the
proportion of NH<sub>4</sub><sup>+</sup> in the phytoplankton N pool suggests that either
very low phytoplankton growth rates resulted in an N turnover time that
exceeded the travel time sampled during this study, or a portion of the
phytoplankton community continued to access nitrate even in the presence of
elevated NH<sub>4</sub><sup>+</sup> concentrations. |
url |
https://www.biogeosciences.net/15/353/2018/bg-15-353-2018.pdf |
work_keys_str_mv |
AT cmschmidt useofflowcytometryandstableisotopeanalysistodeterminephytoplanktonuptakeofwastewaterderivedammoniuminanutrientrichriver AT teckraus useofflowcytometryandstableisotopeanalysistodeterminephytoplanktonuptakeofwastewaterderivedammoniuminanutrientrichriver AT mbyoung useofflowcytometryandstableisotopeanalysistodeterminephytoplanktonuptakeofwastewaterderivedammoniuminanutrientrichriver AT ckendall useofflowcytometryandstableisotopeanalysistodeterminephytoplanktonuptakeofwastewaterderivedammoniuminanutrientrichriver |
_version_ |
1725644883550535680 |