Journal ArticleDOI
Gulf of Mexico Hypoxia, A.K.A. “The Dead Zone”
TLDR
P Paleoindicators in dated sediment cores indicate that hypoxic conditions likely began to appear around the turn of the last century and became more severe since the 1950s as the nitrate flux from the Mississippi River to the Gulf of Mexico tripled.Abstract:
The second largest zone of coastal hypoxia (oxygen-depleted waters) in the world is found on the northern Gulf of Mexico continental shelf adjacent to the outflows of the Mississippi and Atchafalaya Rivers. The combination of high freshwater discharge, wind mixing, regional circulation, and summer warming controls the strength of stratification that goes through a well-defined seasonal cycle. The physical structure of the water column and high nutrient loads that enhance primary production lead to an annual formation of the hypoxic water mass that is dominant from spring through late summer. Paleoindicators in dated sediment cores indicate that hypoxic conditions likely began to appear around the turn of the last century and became more severe since the 1950s as the nitrate flux from the Mississippi River to the Gulf of Mexico tripled. Whereas increased nutrients enhance the production of some organisms, others are eliminated from water masses (they either emigrate from the area or die) where the...read more
Citations
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Supporting Online Material for Spreading Dead Zones and Consequences for Marine Ecosystems
Robert J. Diaz,Rutger Rosenberg +1 more
TL;DR: The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels as discussed by the authors.
Journal ArticleDOI
Spreading Dead Zones and Consequences for Marine Ecosystems
Robert J. Diaz,Rutger Rosenberg +1 more
TL;DR: Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning, exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels.
Journal ArticleDOI
Thresholds of hypoxia for marine biodiversity.
TL;DR: A broad comparative analysis showed that hypoxia thresholds vary greatly across marine benthic organisms and that the conventional definition of 2 mg O2/liter to designate waters as hypoxic is below the empirical sublethal and lethal O2 thresholds for half of the species tested.
Journal ArticleDOI
Roots of the Second Green Revolution
TL;DR: Crop genotypes with greater yield in infertile soils will substantially improve the productivity and sustainability of low-input agroecosystems, and in high-input agricultural systems will reduce the environmental impacts of intensive fertilisation.
Journal ArticleDOI
Nitrogen in Agriculture: Balancing the Cost of an Essential Resource
TL;DR: A number of technologies are available today to reduce nitrogen loss in agricultural cropping systems, such as adding rotational complexity to cropping system to improve N capture by crops, providing farmers with decision support tools for better predicting crop fertilizer N requirements, improving methods for optimizing fertilizer timing and placement, and developing watershed-level strategies to recapture N lost from fields as mentioned in this paper.
References
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Journal ArticleDOI
Human alteration of the global nitrogen cycle: sources and consequences
Peter M. Vitousek,John D. Aber,Robert W. Howarth,Gene E. Likens,Pamela A. Matson,David W. Schindler,William H. Schlesinger,David Tilman +7 more
TL;DR: In this article, a review of available scientific evidence shows that human alterations of the nitrogen cycle have approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing; increased concentrations of the potent greenhouse gas N 2O globally, and increased concentration of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth.
Journal ArticleDOI
Historical overfishing and the recent collapse of coastal ecosystems.
Jeremy B. C. Jackson,Jeremy B. C. Jackson,Michael Xavier Kirby,Wolfgang H Berger,Karen A. Bjorndal,Louis W. Botsford,Bruce J. Bourque,Roger Bradbury,Richard G. Cooke,Jon M. Erlandson,James A. Estes,Terry P. Hughes,Susan M. Kidwell,Carina B. Lange,Hunter S. Lenihan,John M. Pandolfi,Charles H. Peterson,Robert S. Steneck,Mia J. Tegner,Robert R. Warner +19 more
TL;DR: Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of over-fished species until they too were overfished or died of epidemic diseases related to overcrowding as mentioned in this paper.
Journal ArticleDOI
Our evolving conceptual model of the coastal eutrophication problem
TL;DR: For example, a recent review of the early phase of the coastal eutrophication problem can be found in this article, where the authors suggest that the early (phase I) con- ceptual model was strongly influenced by limnologists, who began intense study of lake eutrophicication by the 1960s.
Journal ArticleDOI
Coastal marine eutrophication: A definition, social causes, and future concerns
TL;DR: There is a need in the marine research and management communities for a clear operational definition of the term, eutrophication, and the following are proposed: this definition is consistent with historical usage and emphasizes that eUTrophication is a process, not a trophic state.
Journal ArticleDOI
Harmful Algal Blooms and Eutrophication: Nutrient Sources, Composition, and Consequences
TL;DR: The relationship between harmful algal blooms and eutrophication of coastal waters from human activities has been investigated in this paper, focusing on sources of nutrients, known effects of nutrient loading and reduction, new understanding of pathways of nutrient acquisition among HAB species, and relationships between nutrients and toxic algae.
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Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna
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