Question
In the Amazon River Basin, seasonal floods are crucial for maintaining the health of the ecosystem. The floodwaters bring in sediments and nutrients that support the growth of aquatic plants, which are essential for fish populations. However, if flooding becomes too frequent or severe due to climate change, it can disrupt the delicate balance of species and lead to a shift in the ecosystem, potentially creating a new ecosystem altogether.
Seasonal flooding is a natural phenomenon that occurs in many freshwater ecosystems, such as rivers and wetlands. Positive effects include the replenishment of nutrients in the soil, which can enhance plant growth and increase food availability for herbivores. This, in turn, attracts predators, creating a diverse food web. However, extreme flooding can also displace species, destroy habitats, and lead to a decrease in the populations of some organisms.
The Amazon River basin carries a larger volume of water than any other river basin on Earth. So much, in fact, that seasonal increases and decreases in the volume of water flowing through the river have a measurable impact on the Earth’s gravity field over equatorial South America over the course of the year. Figure 1 shows monthly changes in gravity detected by NASA’s Gravity Recovery and Climate Experiment (GRACE) between March and December 2003. For this region, a geoid height anomaly of 1 millimeter implies that GRACE detected a gravity change roughly equivalent to the change that an additional 4 centimeters of water would produce.
Figure 1. Changes in the geoid height as a result of increases and decreases in the mass of the Amazon River basin as controlled by the hydrologic cycle
Figure 2. Seasonal Flooding in the Amazon River Basin
Month Water Level
(m) Nutrient Availability
(mg/kg)
Fish population
(species)
Plant growth
(kg/m2)
January 5.0 150 20 8
February 6.5 200 25 12
March 8.0 250 30 15
April 10.0 300 35 20
May 9.0 280 33 18
June 7.5 220 28 14
July 6.0 180 24 10
August 5.0 160 21 9
September 4.0 140 19 7
October 3.5 130 18 6
November 4.5 145 19 7
December 5.5 155 21 8
Question 1
Part A
Over the year, which month has the lowest fish population recorded?
Responses
A JulyJuly
B AugustAugust
C OctoberOctober
D NovemberNovember
Question 2
Part B
Based on your answer in Part A, what would be a possible cause for the decreased fish population?
Responses
A There are more predators when water levels are high.There are more predators when water levels are high.
B Decreased aquatic plants provide less food and habitat for fish. Decreased aquatic plants provide less food and habitat for fish.
C Higher water levels hamper fish growth.Higher water levels hamper fish growth.
D Increased sediments provide less nutrients for the fish.
Seasonal flooding is a natural phenomenon that occurs in many freshwater ecosystems, such as rivers and wetlands. Positive effects include the replenishment of nutrients in the soil, which can enhance plant growth and increase food availability for herbivores. This, in turn, attracts predators, creating a diverse food web. However, extreme flooding can also displace species, destroy habitats, and lead to a decrease in the populations of some organisms.
The Amazon River basin carries a larger volume of water than any other river basin on Earth. So much, in fact, that seasonal increases and decreases in the volume of water flowing through the river have a measurable impact on the Earth’s gravity field over equatorial South America over the course of the year. Figure 1 shows monthly changes in gravity detected by NASA’s Gravity Recovery and Climate Experiment (GRACE) between March and December 2003. For this region, a geoid height anomaly of 1 millimeter implies that GRACE detected a gravity change roughly equivalent to the change that an additional 4 centimeters of water would produce.
Figure 1. Changes in the geoid height as a result of increases and decreases in the mass of the Amazon River basin as controlled by the hydrologic cycle
Figure 2. Seasonal Flooding in the Amazon River Basin
Month Water Level
(m) Nutrient Availability
(mg/kg)
Fish population
(species)
Plant growth
(kg/m2)
January 5.0 150 20 8
February 6.5 200 25 12
March 8.0 250 30 15
April 10.0 300 35 20
May 9.0 280 33 18
June 7.5 220 28 14
July 6.0 180 24 10
August 5.0 160 21 9
September 4.0 140 19 7
October 3.5 130 18 6
November 4.5 145 19 7
December 5.5 155 21 8
Question 1
Part A
Over the year, which month has the lowest fish population recorded?
Responses
A JulyJuly
B AugustAugust
C OctoberOctober
D NovemberNovember
Question 2
Part B
Based on your answer in Part A, what would be a possible cause for the decreased fish population?
Responses
A There are more predators when water levels are high.There are more predators when water levels are high.
B Decreased aquatic plants provide less food and habitat for fish. Decreased aquatic plants provide less food and habitat for fish.
C Higher water levels hamper fish growth.Higher water levels hamper fish growth.
D Increased sediments provide less nutrients for the fish.
Answers
GPT-4o mini
**Question 1: Part A**
Over the year, the month with the lowest fish population recorded is:
**A. July**
In July, the fish population is recorded as 24 species, which is the lowest compared to the other months.
---
**Question 2: Part B**
Based on your answer in Part A, a possible cause for the decreased fish population is:
**B. Decreased aquatic plants provide less food and habitat for fish.**
This aligns with the pattern of declining plant growth and nutrient availability, which typically occurs during the lower water levels seen in the mid-year months, contributing to the decline in fish populations.
Over the year, the month with the lowest fish population recorded is:
**A. July**
In July, the fish population is recorded as 24 species, which is the lowest compared to the other months.
---
**Question 2: Part B**
Based on your answer in Part A, a possible cause for the decreased fish population is:
**B. Decreased aquatic plants provide less food and habitat for fish.**
This aligns with the pattern of declining plant growth and nutrient availability, which typically occurs during the lower water levels seen in the mid-year months, contributing to the decline in fish populations.