The science of hypoxia in the Northern Gulf of Mexico: A review

Bianchi, Thomas S.; DiMarco, Steven F.; Cowan, Jr H.; Hetland, Robert D.; Chapman, Piers; Day, John W.; Allison, Mead A.

doi:10.1016/j.scitotenv.2009.11.047

Cited by 333 publications

(265 citation statements)

References 151 publications

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“…The shift of the transition time for the seasonal wind can influence the distribution of the river plume in the mid-summer, thereby influencing the hypoxic area. Although Bianchi et al [2010] speculate on how changing regional wind fields may impact hypoxia on the Louisiana Shelf under some climate change scenarios, the details of how the winds may change as a result of the evolving global system are not presently understood and are worth further investigation.…”

Section: Discussionmentioning

confidence: 99%

Relative role of wind forcing and riverine nutrient input on the extent of hypoxia in the northern Gulf of Mexico

Feng¹,

DiMarco

Jackson

2012

Geophysical Research Letters

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[1] Seasonal hypoxia of the northern Gulf of Mexico has been observed for more than 25 years. It is generally accepted that the variation in the areal extent of hypoxia is determined by changes in nutrient addition from the Mississippi River. In this study, we investigate the statistical relation between the hypoxic area and a new variable, the duration of west wind, using the available measurements for the period 1985-2010. Special consideration was paid to the 1993-2010 period, a time when a large shift in the seasonal hypoxia pattern has been reported. When excluding the years in which hurricanes directly impacted the hypoxic area observation, we find that the duration of west wind is correlated with the hypoxic area at r 2 = 0.32 for the 1985-2010 period, and r 2 = 0.52 for the 1993-2010 period. Multilinear regressions using both wind duration and May-June nitrate loading improve the statistical relationships for both periods to r 2 = 0.69 and 0.74 for the long and short time periods, respectively. Mechanistically, the statistical relationships reflect the movement and changes in horizontal river plume position associated with the wind and the influence of stratification on the hypoxic area. Citation: Feng, Y., S. F. DiMarco, and G. A.Jackson (2012), Relative role of wind forcing and riverine nutrient input on the extent of hypoxia in the northern Gulf of Mexico, Geophys. Res. Lett., 39, L09601,

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Section: Discussionmentioning

confidence: 99%

Relative role of wind forcing and riverine nutrient input on the extent of hypoxia in the northern Gulf of Mexico

Feng¹,

DiMarco

Jackson

2012

Geophysical Research Letters

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“…eutrophication) and, during periods with a stratified water column, the development of a large anoxic region on this shelf, also referred to as a dead zone. The dead zone on the Northern Gulf of Mexico shelf recurs every summer and has grown in size since 1985 (Rabalais et al, 2007) with considerable interannual variability (Bianchi et al 2010). The occurrence of dead zones is rising globally (Diaz and Rosenberg, 2008), as are other consequences of increased nutrient inputs to shelf regions, such as shifts in community structure and rising occurrence of harmful algal blooms (Glibert et al, 2008).…”

Section: Nitrogen Cyclingmentioning

confidence: 99%

The role of continental shelves in nitrogen and carbon cycling: Northwestern North Atlantic case study

Fennel

2010

Ocean Sci.

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Abstract. Continental shelves play a key role in the cycling of nitrogen and carbon. Here the physical transport and biogeochemical transformation processes affecting the fluxes into and out of continental shelf systems are reviewed, and their role in the global cycling of both elements is discussed. Uncertainties in the magnitude of organic and inorganic matter exchange between shelves and the open ocean is a major source of uncertainty in observation-based estimates of nitrogen and carbon fluxes. The shelf-open ocean exchange is hard to quantify based on observations alone, but can be inferred from biogeochemical models. Model-based nitrogen and carbon budgets are presented for the Northwestern North Atlantic continental shelf. Results indicate that shelves are an important sink for fixed nitrogen and a source of alkalinity, but are not much more efficient in exporting organic carbon to the deep ocean than the adjacent open ocean for the shelf region considered.

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“…However, a number of findings and ideas have been articulated recently that suggest the classic concept is too simplistic and that other factors are important as well (Rowe and Chapman, 2002;Hetland and DiMarco, 2008;Sylvan et al, 2006;Bianchi et al, 2010;Lehrter et al, 2009). For example, terrestrial organic matter load probably contributes significantly to oxygen consumption (Bianchi et al, 2010(Bianchi et al, , 2009, stratification is important for hypoxia formation in preventing supply of oxygen below the pycnocline (Wiseman et al, 1997), sediment oxygen demand is not directly related to river nutrient load (Morse and Rowe, 1999;Rowe and Chapman, 2002), and spatially varying rates of macrozooplankton grazing affect the rate of phytoplankton accumulation and the amount of organic matter reaching the bottom (Dagg, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…For example, terrestrial organic matter load probably contributes significantly to oxygen consumption (Bianchi et al, 2010(Bianchi et al, , 2009, stratification is important for hypoxia formation in preventing supply of oxygen below the pycnocline (Wiseman et al, 1997), sediment oxygen demand is not directly related to river nutrient load (Morse and Rowe, 1999;Rowe and Chapman, 2002), and spatially varying rates of macrozooplankton grazing affect the rate of phytoplankton accumulation and the amount of organic matter reaching the bottom (Dagg, 1995). Walker and Rabalais (2006) found no significant relationship between satellite-derived surface chlorophyll and hypoxia development.…”

Section: Introductionmentioning

confidence: 99%

A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability

et al. 2011

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Abstract. The Texas-Louisiana shelf in the Northern Gulf of Mexico receives large inputs of nutrients and freshwater from the Mississippi/Atchafalaya River system. The nutrients stimulate high rates of primary production in the river plume, which contributes to the development of a large and recurring hypoxic area in summer, but the mechanistic links between hypoxia and river discharge of freshwater and nutrients are complex as the accumulation and vertical export of organic matter, the establishment and maintenance of vertical stratification, and the microbial degradation of organic matter are controlled by a non-linear interplay of factors. Unraveling these interactions will have to rely on a combination of observations and models. Here we present results from a realistic, 3-dimensional, physical-biological model with focus on a quantification of nutrient-stimulated phytoplankton growth, its variability and the fate of this organic matter. We demonstrate that the model realistically reproduces many features of observed nitrate and phytoplankton dynamics including observed property distributions and rates. We then contrast the environmental factors and phytoplankton source and sink terms characteristic of three model subregions that represent an ecological gradient from eutrophic to oligotrophic conditions. We analyze specifically the reasons behind the counterintuitive observation that primary production in the light-limited plume region near the Mississippi River delta is positively correlated with river nutrient input, and find that, while primary production and phytoplanktonCorrespondence to: K. Fennel (katja.fennel@dal.ca) biomass are positively correlated with nutrient load, phytoplankton growth rate is not. This suggests that accumulation of biomass in this region is not primarily controlled bottom up by nutrient-stimulation, but top down by systematic differences in the loss processes.

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The science of hypoxia in the Northern Gulf of Mexico: A review

Cited by 333 publications

References 151 publications

Relative role of wind forcing and riverine nutrient input on the extent of hypoxia in the northern Gulf of Mexico

Relative role of wind forcing and riverine nutrient input on the extent of hypoxia in the northern Gulf of Mexico

The role of continental shelves in nitrogen and carbon cycling: Northwestern North Atlantic case study

A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability

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