Jump to main content
US EPA
United States Environmental Protection Agency
Search
Search
Main menu
Environmental Topics
Laws & Regulations
About EPA
Health & Environmental Research Online (HERO)
Contact Us
Print
Feedback
Export to File
Search:
This record has one attached file:
Add More Files
Attach File(s):
Display Name for File*:
Save
Citation
Tags
HERO ID
91918
Reference Type
Journal Article
Title
Does nitrogen or silicon limit phytoplankton production in the Mississippi River plume and nearby regions?
Author(s)
Dortch, Q; Whitledge, TE
Year
1992
Is Peer Reviewed?
Yes
Journal
Continental Shelf Research
ISSN:
0278-4343
Volume
12
Issue
11
Page Numbers
1293-1309
Language
English
DOI
10.1016/0278-4343(92)90065-R
Web of Science Id
WOS:A1992JR20600003
Abstract
The Mississippi River carries very high concentrations of nutrients into the otherwise oligotrophic Gulf of Mexico, resulting in high primary production and hypoxia along the Louisiana continental shelf. The hypothesis that nitrogen availability controls and ultimately limits phytoplankton production on the shelf was tested by measuring an indicator of nitrogen deficiency, the ratio of intracellular free amino acids/particulate protein (AA/Pr), in the area of the Mississippi River plume on a spring and a summer cruise. Neither AA/Pr ratios or nutrients in the water showed nitrogen limitation to be widespread. Ammonium concentrations were generally quite high, so the lack of phytoplankton nitrogen deficiency can be explained by rapid regeneration rates. Nitrogen limitation was most likely in the summer at high salinities. However, ratios of dissolved nutrient concentrations suggested that silicate was as likely, or sometimes more likely, to be a limiting nutrient than nitrogen. Although silicate depletion may not cause a decrease in productivity, it could result in major changes in phytoplankton size and species composition, and ultimately influence trophodynamics, regeneration, the fate of carbon, and severity and extent of hypoxia.
Tags
•
ISA NOxSOxPM Ecology (2018)
Cited in First Draft
Chapter 10
Cited in the Second Draft
Appendix 10
•
ISA NOxSOxPM Ecology (2020- Final Project Page)
Cited
Appendix 10
Home
Learn about HERO
Using HERO
Search HERO
Projects in HERO
Risk Assessment
Transparency & Integrity