Characterization of Hypoxia: Topic I Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico

Nutrient overenrichment from human activities is one of the major stresses affecting coastal ecosystems. There is increasing concern in many areas around the world that an oversupply of nutrients from multiple sources is having pervasive ecological effects on shallow coastal and estuarine areas. These effects include reduced light penetration, loss of aquatic habitat, harmfid algal blooms, a decrease in dissolved oxygen (or hypoxia), and impacts on living resources. The largest zone of oxygen-depleted coastal waters in the United States, and the entire western Atlantic Ocean, is found in the northern Gulf of Mexico on the Louisiana-Texas continental shelf. This zone is influenced by the freshwater discharge and nutrient flux of the Mississippi River system. This report describes the seasonal, interannual, and long-term variability in hypoxia in the northern Gulf of Mexico and its relationship to nutrient loading. It also documents the relative roles of natural and human-induced factors in determining the size and duration of the hypoxic zone.

Changes in nutrient structure of river-dominated coastal waters: stoichiometric nutrient balance and its consequences

We present an analysis of extensive nutrient data sets from two river-dominated coastal ecosystems, the northern Adriatic Sea and the northern Gulf of Mexico, demonstrating significant changes in surface nutrient ratios over a period of 30 years. The silicon:nitrogen ratios have decreased, indicating increased potential for silicon limitation. The nitrogen:phosphorus and the silicon:phosphorus ratios have also changed substantially, and the coastal nutrient structures have become more balanced and potentially less limiting for phytoplankton growth. It is likely that net phytoplankton productivity increased under these conditions and was accompanied by increasing bottom water hypoxia and major changes in community species composition. These findings support the hypothesis that increasing coastal eutrophication to date may be associated with stoichiometric nutrient balance, due to increasing potential for silicon limitation and decreasing potential for nitrogen and phosphorus limitation. On a worldwide basis, coastal ecosystems adjacent to rivers influenced by anthropogenic nutrient loads may experience similar alterations.

BRS Ponta Negra variedade de sorgo forrageiro.

2007

Híbrido do sorgo granífero BRS 308.

2007

Híbrido de sorgo granífero BRS 309.

2007

Identificação de genótipos de sorgo para eficiência no uso de nitrogênio.

1998

Hibrido de sorgo granifero BRS 310.

2004

BRS 610: híbrido de sorgo forrageiro para a produção de silagem de alta qualidade.

2004

BRS 801: híbrido de sorgo de pastejo.

2004

Sorgo híbrido granífero BRS 307.

2004

Caracterização de linhagens de milho quanto aos teores de minerais nos grãos.

2005

Regeneração em cultura de tecido de cultivares de Sorghum bicolor através de organogênese.

2005

Transformação genética do sorgo utilizando o bombardeamento de partículas.

2005

BRS 655: híbrido de sorgo forrageiro para produção de silagem de alta qualidade.

2008

Metodologia de avaliação de exsudados radiculares em linhagens de sorgo submetidos ao estresse de fósforo.

2009