Question

the gulf of america dead zone is an area of hypoxic waters at the mouth of the mississippi river. its area varies in size, but can cover up to 6,000 - 7,000 square miles. the zone occurs between the inner and mid - continental shelf in the northern gulf of america, beginning at the mississippi river delta and extending westward to the upper texas coast. thousands of farms are located along the mississippi river and its tributaries and as water washes into the river after a heavy rain, it brings with it nutrients from fertilizers added to farmland. these materials flow downriver and eventually enter the gulf of america, where they create conditions for a dead zone: an area of low to no oxygen that results in the death of fish and other marine life. the gulf of america is a major source area for the seafood industry. the gulf supplies 72% of u.s. harvested shrimp, 66% of harvested oysters, and 16% of commercial fish. consequently, if the hypoxic zone continues or worsens, fishermen and coastal state economies will be greatly impacted. what can be done to minimize the gulf dead zone? choose all that could apply.
a control of animal wastes so that they are not allowed to enter into waterways.
b adjust the timing of fertilizer applications to limit runoff of excess nutrients from farmland.
c monitor septic systems and sewage treatment facilities to reduce discharge of nutrients to surface water and groundwater.
d restrict land use in the areas surrounding the mississippi delta to exclude industrial sites.
e counter the effects of fertilizers on algal growth in the gulf with the use of chemical herbicides.

Explanation:

• Option A: Animal wastes can also introduce nutrients (like nitrogen/phosphorus) into waterways. Controlling them reduces nutrient input, helping minimize the dead zone.
• Option B: The dead zone is caused by nutrient runoff (especially from fertilizers) into the river. Adjusting fertilizer application timing (e.g., avoiding rainy periods) limits excess nutrients entering waterways, reducing algal blooms and hypoxia.
• Option C: Septic systems and sewage treatment facilities can release nutrients. Monitoring them reduces nutrient discharge, aiding in dead zone reduction.
• Option D: Industrial sites aren’t the main source of nutrients for the dead zone (agriculture is). Restricting industrial land use won’t address the nutrient runoff issue.
• Option E: Using chemical herbicides in the Gulf could harm marine life and disrupt ecosystems, and it doesn’t address the root cause (nutrient runoff) but treats a symptom (algal growth) in a damaging way.

Answer:

A. Control of animal wastes so that they are not allowed to enter into waterways.
B. Adjust the timing of fertilizer applications to limit runoff of excess nutrients from farmland.
C. Monitor septic systems and sewage treatment facilities to reduce discharge of nutrients to surface water and groundwater.