Ammonium Excretion by Benthic Invertebrates and Sediment-Water Nitrogen Flux in the Gulf of Mexico near the Mississippi River Outflow

Estuaries ◽  
1993 ◽  
Vol 16 (4) ◽  
pp. 799 ◽  
Author(s):  
Wayne S. Gardner ◽  
Elva Escobar Briones ◽  
Elizabeth Cruz Kaegi ◽  
Gilbert T. Rowe
Author(s):  
Paul A. Montagna

ABSTRACT ID 685153 Because of death and gravity, the bottom of the sea is the memory of the ecosystem, where a record of all past events can be found as you move into deeper layers of sediment. Thus, benthos are primary indicators for environmental assessments. As hydrocarbon exploration and production moved to deeper waters, so did environmental studies. But there were only a few Gulf-wide surveys in the deepest parts of the Gulf of Mexico, and our understanding of deep-sea processes was based primarily on other regions of the world. The intensive focus on deep-sea response during and after the Deepwater Horizon (DWH) accident increased our knowledge dramatically. We learned that the deep sea is dynamic, fragile, and will take a long time to recover. There was a 50% loss of biodiversity within 9 km diameter around the DWH site, and a 10% within a 17 km of the site. But there is still much to learn. The deep-sea is a reservoir of biodiversity on Earth, but about 60% of Gulf of Mexico taxa are still unknown, which is a major hinderance to understanding the effects of oil spills. The northern Gulf of Mexico is dominated by Mississippi River outflow, but exactly how it drives deep-sea dynamics needs better resolution. Two outcomes of the last decade of research is that we know benthos diversity is a sensitive indicator of environmental change and damage, the surface sediments are the biologically active zones, and the natural process of sinking particles will eventually cover the damaged sediment leading to natural recovery. This “restoration in place” strategy must be confirmed by future monitoring and assessment studies.


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.


Zootaxa ◽  
2011 ◽  
Vol 2933 (1) ◽  
pp. 65 ◽  
Author(s):  
WILLIAM B. DRIGGERS III ◽  
ERIC R. HOFFMAYER ◽  
EMMA L. HICKERSON ◽  
TIMOTHY L. MARTIN ◽  
CHRISTOPHER T. GLEDHILL

Among the sharks inhabiting the continental shelf waters of the western North Atlantic Ocean, those within the genus Carcharhinus are the most speciose (Castro 2011). Authoritative sources agree on the presence of twelve species of carcharhinids in the northern Gulf of Mexico; however, they disagree on the presence of a thirteenth species, C. perezi (Poey), in the region (Compagno 1984, Compagno 2002, McEachran & Fechhelm 1998, Castro 2011). While the range of C. perezi is well-documented to extend from the southeastern coast of Florida and the Bahamas to Brazil (Castro 2011), published records of C. perezi occurring in the northern Gulf of Mexico are limited to two sources. In their description of Eulamia springeri, a junior synonym of C. perezi, Bigelow & Schroeder (1944) place the species in the northern Gulf of Mexico based on “a somewhat shrivelled skin with head” from a specimen collected off the west coast of Florida that was reported by the authors to be “probably of this species.” Later, Springer (1960) reported the capture of a single specimen off the Mississippi River Delta in 1947; however, no detail of the capture was provided other than it being listed within a table summarizing shark species collected during exploratory fishing operations.


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