scholarly journals OXYGEN DEPLETION IN THE GULF OF MEXICO ADJACENT TO THE MISSISSIPPI RIVER

Author(s):  
Nancy N. Rabalais ◽  
R. Eugene Turner
Dead Zones ◽  
2021 ◽  
pp. 89-105
Author(s):  
David L. Kirchman

The fertilizers commonly used by gardeners have many ingredients, but the biggest two are nitrogen and phosphorus, either of which can limit plant and algal growth. The idea that only one nutrient limits growth is encapsulated by Liebig’s Law of the Minimum, named after Justus von Liebig, a 19th-century German chemist. Liebig is also called the “father of fertilizer” because of his work on formulating and promulgating commercial fertilizers. However, he wasn’t the first to discover the Law, and he was wrong about the most important ingredient of fertilizers. This chapter outlines the arguments among limnologists, oceanographers, and geochemists about whether nitrogen or phosphorus sets the rate of algal growth and thus production of the organic material that drives oxygen depletion. The chapter discusses that the limiting nutrient varies with the type of aquatic habitat. In dead zones like the Gulf of Mexico, parts of the Baltic Sea, and Chesapeake Bay, bioassay experiments have shown that nitrogen is usually limiting. The nitrogen necessary for fertilizer and ammunitions comes from the Haber-Bosch process. The chapter reviews the life of one of the two German inventors, Fritz Haber, and how it was full of contradictions if not tragedy.


2019 ◽  
Vol 11 (6) ◽  
pp. 723 ◽  
Author(s):  
Daniel Otis ◽  
Matthieu Le Hénaff ◽  
Vassiliki Kourafalou ◽  
Lucas McEachron ◽  
Frank Muller-Karger

The cross-shelf advection of coastal waters into the deep Gulf of Mexico is important for the transport of nutrients or potential pollutants. Twenty years of ocean color satellite imagery document such cross-shelf transport events via three export pathways in the Gulf of Mexico: from the Campeche Bank toward the central Gulf, from the Campeche Bank toward the Florida Straits, and from the Mississippi Delta to the Florida Straits. A catalog of these events was created based on the visual examination of 7280 daily satellite images. Water transport from the Campeche Bank to the central Gulf occurred frequently and with no seasonal pattern. Transport from Campeche Bank to the Florida Straits occurred episodically, when the Loop Current was retracted. Four such episodes were identified, between about December and June, in 2002, 2009, 2016, and 2017, each lasting ~3 months. Movement of Mississippi River water to the Florida Straits was more frequent and showed near seasonal occurrence, when the Loop Current was extended, while the Mississippi River discharge seems to play only a secondary role. Eight such episodes were identified—in 1999, 2000, 2003, 2004, 2006, 2011, 2014, and 2015—each lasting ~3 months during summer. The 2015 episode lasted 5 months.


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