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https://mymasonportal.gmu.edu/bbcswebdav/users/klargen/EVPP%20110%20Lecture%20-%20Case%20Study%20-%20The%20Dead%20Zone%20-%20Ecology%20and%20Oceanography%20in%20the%20Gulf%20of%20Mexico.pdf
Use the link above to answer the questions below :
1. Based on Figure 4 and Figure 5, which of the following statements is true?
the greatest rates of primary production occur at the same time of the year as the greatest rates of respiration
primary production peaks earlier in the year than respiration
respiration rates are highest in July and August
choices 2 and 3 are true
QUESTION 2
According to the station profiles in Figure 2, on which date was there the greatest difference in salinity concentration between the surface and a depth of ~7.5 meters?
April 10, 1992
June 17, 1992
August 12, 1992
September 19, 1992
QUESTION 3
According to the station profile for April 10, 1992, in Figure 2, what was the dissolved oxygen concentration at a depth of 15 meters?
1 mg/L
5 mg/L
8 mg/L
10 mg/L
QUESTION 4
According to Figure 8, which nitrogen source has added the greatest amount of nitrogen to the land in the Mississippi River basin in the years since 1970?
fertilizer
fixation
manure
none of the above
QUESTION 5
According to the document, an influx of which nutrient is most likely responsible for the increase in primary productivity noted in Figure 4?
carbon dioxide
nitrate-nitrogen
phosphate-phosphorus
potassium
QUESTION 6
A goal has been established to increase the area of the Dead Zone to approximately 10,000 square kilometers by the year 2015, roughly twice the size of the zone between 2003-2007.
True
False
QUESTION 7
According to the station profiles in Figure 2, on which date was the dissolved oxygen concentration most consistently low between the surface and 20 meters depth?
April 10, 1992
June 17, 1992
August 12, 19992
September 19, 1992
QUESTION 8
Which of the following is a strategy being considered by state and federal agencies to reduce nutrient pollution from farmlands before it enters the Mississippi River system.
voluntary reduction in fertilizer application
restoring wetlands along waterways
establishment of vegetated buffering zones to absorb nutrients before they enter rivers and streams
all of the above are being considered
QUESTION 9
Most scientists examining the data from numerous studies have concluded that fertilizer application in farms of the Mississippi River basin are the source of nitrogen that leads to the Dead Zone.
True
False
QUESTION 10
Which of the following statements is not true?
photosynthesis by phytoplankton decreased sharply in the spring months (as evidenced by an increase in primary productivity)
following the spring peak in primary productivity, photosynthetic rates declined as the phytoplankton died and respiration rates rose dramatically
organic matter from dead phyotplankton sank, providing a rich food source for marine bacteria at the base of the water column
as bacterial populations climbed, they depleted the oxygen available in the water, especially at the bottom of the water
photosynthesis by phytoplankton increased sharply in the spring months (as evidenced by an increase in primary productivity)
QUESTION 11
According to Figure 4, which of the following statements about primary productivity in the Gulf of Mexico is true?
primary productivity is constant (the same every month) throughout the year
primary productivity is highest in April
primary productivity is highest in July
primary productivity is lowest in October
choices 2 and 4 are true
0.2 points
QUESTION 12
According to the document, which of the following help explain the fact the the Dead Zone is a temporary phenomenon each year?
The discharge of the Mississippi River is constant throughout the year.
The Dead Zone gets flushed out by the turbulence of fall and winter storms.
The rates of primary productivity and respiration are constant throughout the year.
There is an increase in nitrogen input in the spring during peak river discharge and this drives increases in primary productivity.
Both 2 and 4 are correct.
Both 1 and 3 are correct.
0.2 points
QUESTION 13
According to the station profiles in Figure 2, there was an increase in salinity concentration with depth on all four sampling dates.
True
False
0.2 points
QUESTION 14
Light and nutrients are known to be limiting factors for phytoplankton growth. Why was light ruled out as the factor leading to the observed increase in phytoplankton population growth (as evidenced by increased rates of primary productivity) ?
the sun shines year-round but the primary productivity rates vary throughout the year
a reduction was seen in primary productivity in May and June even though the length of the day was still increasing during those months
the sun shines year-round and the primary productivity rates are the same throughout the year
none of the above
0.2 points
QUESTION 15
Water that has a dissolved oxygen concentration of less that 2 mg/L is called hypoxic. According to the station profiles in Figure 2, on which date did the water become hypoxic at the most shallow depth?
April 10, 1992
June 17, 1992
August 12, 1992
September 19, 1992
0.2 points
QUESTION 16
According to Figure 7, the amount of nitrogen and nitrate (in millions of tons per year) dischared into the Gulf of Mexico by the Mississippi River was less in the year 2000 thatn in the year 1960.
True
False
0.2 points
QUESTION 17
The "dead zone" is an area in the Gulf of Mexico where _________________.
all life of all types has permanently disappeared
there is very litle in the way of marine macro-organisms during the summer
the dissolved oxygen levels in the water get so depleted that the water can't support life
choices 2 and 3 are correct
0.2 points
QUESTION 18
According to Figure 6, what are the peak months for nitrate-nitrogen discharge from the Mississippi River into the Gulf?
July, August, September
April, May, June
March, April, May
October, November, December
0.2 points
QUESTION 19
The data in Figures 7 and 8 are consistent with the idea that nitrogen naturally present in
rich prairie soils is the source of nitrogen carried into the Gulf of Mexico.
True
False
0.2 points
QUESTION 20
Which of the following statements is true?
the lowest rate of nitrate-nitrogen discharge from the Mississippi River into the Gulf occurs in the same month that the highest rate of primary productivity occurs
the highest rate of nitrate-nitrogen discharge from the Mississippi River into the Gulf occurs in the same month that the highest rate of primary productivity occurs
the highest rate of nitrate-nitrogen discharge from the Mississippi River into the Gulf occurs in the same month that the lowest rate of primary productivity occurs
the lowest rate of nitrate-nitrogen discharge from the Mississippi River into the Gulf occurs in the same month that the lowest rate of primary productivity occurs
the greatest rates of primary production occur at the same time of the year as the greatest rates of respiration
primary production peaks earlier in the year than respiration
respiration rates are highest in July and August
choices 2 and 3 are true
Explanation / Answer
1. Choices 2 and 3 are true. It can be clearly seen from the figures.
2 September 19, 1992. On this day the difference between the slainity concentration at the depth and at the surface is maximum.
3. 5 mg/L. The dissolved oxygen concentration is indicated by the circles. and from the graph at depth 15 m the dissolved oxygen concentration is 5 approx.
4. Fertilizer. The amount of nitrogen by from fertilizer is increasing and maximum among all three since 1970.
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