Gulf of Mexico Hypoxia: Past, Present, and Future

These flashcards cover key concepts regarding the hypoxia in the Gulf of Mexico, addressing causes, consequences, and mitigation strategies based on the provided lecture notes.

What is hypoxia and how is it defined in the Gulf of Mexico context?

Hypoxia is defined as a condition where dissolved oxygen (DO) concentration is ≤2 mg l−1.

When did seasonal hypoxia in the Gulf of Mexico start to become problematic?

Seasonal hypoxia began in the 1950s, with worsening severity noted during the 1970s.

What has the maximum area of hypoxic waters been in the northern Gulf of Mexico by mid-summer?

The maximum area of hypoxic waters can reach up to 23,000 km2.

What are the main sources of freshwater and nutrients to the northern Gulf of Mexico?

The main sources are the Mississippi River and the Atchafalaya River.

Which years did the estimated annual nitrogen load from the Mississippi River drop to levels recorded between 1972 and 1993?

According to studies, the nitrogen load for the years 1972-1993 represents 91% of the N load.

What influences the position and extent of hypoxic waters in the Gulf of Mexico?

The position and extent of hypoxic waters are influenced by freshwater discharge and winds.

What months have low dissolved oxygen levels not been recorded?

Hypoxia has not been documented in December and January.

What factors can temporarily mix the hypoxic water layer in the Gulf?

Tropical storms, hurricanes, or sustained winds from the west can mix the water column.

What role do nutrient loading and stratification play in the Gulf of Mexico's hypoxic conditions?

Nutrient loading causes increased primary production, while stratification maintains hypoxia by preventing mixing.

What are the likely consequences of climate change projected for hypoxia in the Gulf of Mexico?

Climate change may exacerbate hypoxia due to increased nutrient runoff and stronger stratification.

What have studies indicated about the trend of nitrogen and phosphorus loads in the Mississippi River since the mid-1950s?

The total nitrogen load has increased threefold since the mid-1950s, while phosphorus loads have doubled.

What dietary suggestions have been made to reduce nitrogen loading in watersheds?

Eating less meat can reduce nitrogen overall, as livestock production is nitrogen-intensive.

What management actions are suggested to mitigate hypoxia in the Gulf of Mexico?

Key actions include reducing nitrogen and phosphorus loads through better agricultural practices.

What is a 'dead zone' in the context of the Gulf of Mexico?

A 'dead zone' refers to areas with low dissolved oxygen where bottom-dwelling species like fish and shrimp can be absent.

How does agriculture contribute to nitrogen loading in rivers?

Agricultural practices, particularly those involving fertilizers and tile drainage, contribute significantly to nitrogen loading.