Characterization of nutrient, organic carbon, and sediment loads and concentrations from the Mississippi River into the northern Gulf of Mexico

2007 ◽  
Vol 30 (5) ◽  
pp. 773-790 ◽  
Author(s):  
R. E. Turner ◽  
N. N. Rabalais ◽  
R. B. Alexander ◽  
G. McIsaac ◽  
R. W. Howarth
Keyword(s):  
Organic Carbon ◽  
Gulf Of Mexico ◽  
Mississippi River ◽  
Northern Gulf Of Mexico ◽  
Sediment Loads

scholarly journals Sediment Chemistry and Meiofauna from the Northern Gulf of Mexico Continental Shelf

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ceil C. Martinec ◽  
Jonathan M. Miller ◽  
Nathan K. Barron ◽  
Rui Tao ◽  
Kewei Yu ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Gulf Of Mexico ◽  
Continental Shelf ◽  
Mississippi River ◽  
Coarse Sand ◽  
Sediment Chemistry ◽  
Mississippi River Delta ◽  
Northern Gulf Of Mexico ◽  
Total Pahs ◽  
Carbon Concentrations

This study examined sediment chemistry, granulometry, and meiofauna on the northern Gulf of Mexico continental shelf from central Louisiana to Apalachicola, Florida. Sediment samples were collected in October/November 2012 with a Shipek grab sampler from 26 locations (extending from 28°18′46.079′′N, 91°10′44.471′′W to 29°3′48.383′′N, 85°28′25.679′′W) at depths ranging from 49 to 361 m. Sediment analysis revealed two distinct profiles to the east and west of the Mississippi River Delta at approximately 88°30′W. The concentrations of silt + clay, organic carbon, Ba, Cr, Cu, Fe, Ni, Pb, V, and Zn were higher in western sites and positively correlated with Al concentrations. Eastern sites contained sandier sediments with lower organic carbon concentrations and higher Sr and Ca concentrations. Nematode densities were higher at western sites and positively correlated with Al, Cr, Cu, Fe, Ni, Pb, Zn, silt + clay, and organic carbon concentrations. Copepod densities correlated with very coarse + coarse sand, exhibiting higher densities at eastern sites. PAH concentrations were relatively low, with all sites having <1700 µg/kg total PAHs. This study has revealed two distinct sediment profiles in the eastern and western zones of the study, which appear to influence the nematode and copepod densities.

Characterization of a toxic Pseudo-nitzschia spp. bloom in the Northern Gulf of Mexico associated with domoic acid accumulation in fish

Harmful Algae ◽  
2013 ◽  
Vol 26 ◽  
pp. 20-32 ◽  
Author(s):  
Justin D. Liefer ◽  
Alison Robertson ◽  
Hugh L. MacIntyre ◽  
William L. Smith ◽  
Carol P. Dorsey
Keyword(s):  
Gulf Of Mexico ◽  
Domoic Acid ◽  
Northern Gulf Of Mexico ◽  
Acid Accumulation

Validating the occurrence of Caribbean reef sharks, Carcharhinus perezi (Poey), (Chondrichthyes: Carcharhiniformes) in the northern Gulf of Mexico, with a key for sharks of the family Carcharhinidae inhabiting the region

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
Keyword(s):  
Gulf Of Mexico ◽  
North Atlantic ◽  
Mississippi River ◽  
North Atlantic Ocean ◽  
Shark Species ◽  
Mississippi River Delta ◽  
The Bahamas ◽  
Northern Gulf Of Mexico ◽  
The Family ◽  
Reef Sharks

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.

scholarly journals Extensive reproductive disruption, ovarian masculinization and aromatase suppression in Atlantic croaker in the northern Gulf of Mexico hypoxic zone

2011 ◽  
Vol 279 (1726) ◽  
pp. 28-38 ◽  
Author(s):  
Peter Thomas ◽  
Md. Saydur Rahman
Keyword(s):  
Gulf Of Mexico ◽  
Mississippi River ◽  
Aromatase Activity ◽  
Northern Gulf Of Mexico ◽  
Hypoxia Exposure ◽  
Hypoxic Zone ◽  
Seasonal Hypoxia ◽  
Reproductive Disruptions ◽  
Reproductive Disruption

The long-term impacts on marine ecosystems of the recent dramatic worldwide increase in the incidence of coastal hypoxia are unknown. Here, we show widespread reproductive disruption in Atlantic croakers collected from hypoxic sites approximately 120 km apart in the extensive northern Gulf of Mexico continental shelf hypoxic zone. Gonadal growth and gamete production were impaired in croakers from hypoxic sites compared with fish from reference normoxic sites east of the Mississippi River Delta. Male germ cells were detected in approximately 19 per cent of croaker ovaries collected in the hypoxic region, but were absent in ovaries from normoxic sites. In addition, the sex ratio was skewed towards males at the hypoxic sites. The masculinization and other reproductive disruptions were associated with declines in neuroendocrine function, as well as ovarian and brain expression of aromatase (the enzyme that converts androgens to oestrogens). A similar incidence of ovarian masculinization and decline in ovarian aromatase expression were observed in croaker after chronic laboratory hypoxia exposure, indicating that ovarian masculinization is a specific hypoxia response and is due to decreased aromatase activity. The results suggest severe reproductive impairment can occur over large coastal regions in marine fish populations exposed to seasonal hypoxia, with potential long-term impacts on population abundance.

scholarly journals Variations in primary production of northern Gulf of Mexico continental shelf waters linked to nutrient inputs from the Mississippi River

1997 ◽  
Vol 155 ◽  
pp. 45-54 ◽  
Author(s):  
SE Lohrenz ◽  
GL Fahnenstiel ◽  
DG Redalje ◽  
GA Lang ◽  
X Chen ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Primary Production ◽  
Continental Shelf ◽  
Mississippi River ◽  
Nutrient Inputs ◽  
Northern Gulf Of Mexico

scholarly journals Ensemble modeling informs hypoxia management in the northern Gulf of Mexico

2017 ◽  
Vol 114 (33) ◽  
pp. 8823-8828 ◽  
Author(s):  
Donald Scavia ◽  
Isabella Bertani ◽  
Daniel R. Obenour ◽  
R. Eugene Turner ◽  
David R. Forrest ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Mississippi River ◽  
Task Force ◽  
Weather Conditions ◽  
Nitrogen Loading ◽  
Load Reduction ◽  
Nutrient Inputs ◽  
Northern Gulf Of Mexico ◽  
Water Column Stratification ◽  
Hypoxic Area

A large region of low-dissolved-oxygen bottom waters (hypoxia) forms nearly every summer in the northern Gulf of Mexico because of nutrient inputs from the Mississippi River Basin and water column stratification. Policymakers developed goals to reduce the area of hypoxic extent because of its ecological, economic, and commercial fisheries impacts. However, the goals remain elusive after 30 y of research and monitoring and 15 y of goal-setting and assessment because there has been little change in river nitrogen concentrations. An intergovernmental Task Force recently extended to 2035 the deadline for achieving the goal of a 5,000-km2 5-y average hypoxic zone and set an interim load target of a 20% reduction of the spring nitrogen loading from the Mississippi River by 2025 as part of their adaptive management process. The Task Force has asked modelers to reassess the loading reduction required to achieve the 2035 goal and to determine the effect of the 20% interim load reduction. Here, we address both questions using a probabilistic ensemble of four substantially different hypoxia models. Our results indicate that, under typical weather conditions, a 59% reduction in Mississippi River nitrogen load is required to reduce hypoxic area to 5,000 km2. The interim goal of a 20% load reduction is expected to produce an 18% reduction in hypoxic area over the long term. However, due to substantial interannual variability, a 25% load reduction is required before there is 95% certainty of observing any hypoxic area reduction between consecutive 5-y assessment periods.

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