The Global Ecosystem

46

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

One aspect of ecosystem function:

Net primary productivity (NPP)—rate at which an ecosystem produces primary-producer biomass.

NPP can be estimated by instruments on satellites that measure wavelengths of light reflected from the Earth’s surface.

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

NPP varies among ecosystem types, mostly due to variation in climate and nutrient availability.

Tropical forests, swamps, and marshlands are the most productive.

Cultivated land is less productive than many natural ecosystems.

Figure 46.1 NPP Varies among Ecosystem Types

Figure 46.2 Terrestrial NPP Corresponds to Climate

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

Discuss why NPP (net primary productivity), usually measured as grams of primary-producer biomass produced per unit of area per year, is a measure of ecosystem function.

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

NPP (net primary productivity), usually measured as grams of primary-producer biomass produced per unit of area per year, is a measure of ecosystem function because

a. NPP measures the rate of exchange of materials (especially carbon) between biotic and abiotic components of ecosystems.

b. NPP measures the net rate with which solar energy is captured by an ecosystem’s primary producers.

c. Both a and b

d. None of the above

e. I don’t understand the question.

Figure 46.3 Terrestrial NPP Varies with Temperature and Precipitation

Figure 46.3 Terrestrial NPP Varies with Temperature and Precipitation (Part 1)

Figure 46.3 Terrestrial NPP Varies with Temperature and Precipitation (Part 2)

Figure 46.4 Marine NPP Is Highest around Coastlines

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

Compare the following maps of terrestrial and marine NPP.

With a partner or group, discuss:

• What does the terrestrial pattern suggest determines terrestrial NPP?

• What does the marine pattern suggest determines marine NPP?

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

Compare the following maps of terrestrial and marine NPP.

The patterns for terrestrial NPP suggest it is linked to

a. temperature.

b. precipitation.

c. latitude.

d. All of the above

e. None of the above

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

Compare the following maps of terrestrial and marine NPP.

The patterns for marine NPP suggest it is limited by

a. latitude.

b. distance from shore.

c. upwelling.

d. runoff.

e. b, c, and d

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

As winds push water across the ocean surface, water rises up from underneath the displaced water to replace it. This is called “upwelling.” Upwelling occurs in the open ocean and especially along coastlines. The water that rises up from deeper levels of the ocean is colder and rich in nutrients. These nutrients fertilize the surface waters and result in higher biological productivity. Algal blooms provide more food for fish, resulting in growth in fish populations when and where upwelling is strong.

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

Fisheries are directly impacted by the strength of upwelling. Without nutrients from the upwelling, there are few phytoplankton, and with few phytoplankton, little food for fish.

Off California, upwelling of cold water has become less common since 1975. What do you predict will result if less upwelling is indeed a long-term trend?

Concept 46.1 Climate and Nutrients Affect Ecosystem Function

Fisheries are directly impacted by the strength of upwelling. Without nutrients from the upwelling, there are few phytoplankton, and with few phytoplankton, little food for fish.

Off California, upwelling of cold water has become less common since 1975. Which of the following scenarios might you predict if less upwelling is indeed a long-term trend?

a. Fisheries will benefit.

b. Fish populations will decline as the strength of upwelling decreases.

c. More nutrients will likely rise to the surface.

d. Phytoplankton growth will decrease as upwelling weakens.

e. Both b and d

Figure 46.5 Chemical Elements Cycle among Compartments of the Biosphere

Figure 54.20 Review: Generalized scheme for biogeochemical cycles

Figure 46.6 The Global Water Cycle

Figure 46.7 The Global Nitrogen Cycle

Figure 46.8 Where Does the Extra Nitrogen Come From?

Figure 46.8 Where Does the Extra Nitrogen Come From? (Part 1)

Figure 46.8 Where Does the Extra Nitrogen Come From? (Part 2)

Figure 46.9 High Nutrient Input Creates Dead Zones

Figure 46.9 High Nutrient Input Creates Dead Zones

Figure 46.10 The Global Carbon Cycle

Figure 46.11 Earth’s Radiation Balance

Figure 46.12 Atmospheric Greenhouse Gas Concentrations Are Increasing

Figure 46.12 Atmospheric Greenhouse Gas Concentrations Are Increasing (Part 1)

Figure 46.12 Atmospheric Greenhouse Gas Concentrations Are Increasing (Part 2)

Figure 46.13 Global Temperatures Are Increasing

Figure 46.14 Global Precipitation Patterns Have Changed

Apply the Concept, Ch. 46, p. 905

Figure 46.15 Climate Change Affects Life Histories

Concept 46.2 Biological, Geological, and Chemical Processes Move Materials through Ecosystems

Discuss which of the following processes results in a net flux that removes carbon from the atmospheric pool of carbon:

• Plant respiration

• Plant photosynthesis (gross primary productivity)

• Burning of fossil fuels

Concept 46.2 Biological, Geological, and Chemical Processes Move Materials through Ecosystems

Which of the following processes results in a net flux that removes carbon from the atmospheric pool of carbon?

a. Plant respiration

b. Plant photosynthesis (gross primary productivity)

c. Burning of fossil fuels

d. All of the above

e. None of the above

Concept 46.3 Certain Biogeochemical Cycles Are Especially Critical for Ecosystems

The Northern Hemisphere of Earth has a greater land surface than that of the Southern Hemisphere, and more of Earth’s plants (especially forests) occur in the Northern Hemisphere.

Discuss the pattern of seasonal variation in CO2 levels seen in this Mauna Loa, Hawaii graph, and discuss how plant photosynthesis and respiration can explain this predictable seasonal pattern.

Concept 46.3 Certain Biogeochemical Cycles Are Especially Critical for Ecosystems

Which of the following statements could explain the seasonal variation in CO2 levels in the atmosphere?

a. Atmospheric CO2 levels increase during the Northern Hemisphere summer because plants respire more at this warmer time.

b. Atmospheric CO2 levels decrease during the Northern Hemisphere winter because plants photosynthesize more at this colder time.

c. The greater total terrestrial biomass in the Northern Hemisphere compared with the Southern Hemisphere drives these seasonal CO2 patterns.

d. All of the above

e. None of the above

Concept 46.3 Certain Biogeochemical Cycles Are Especially Critical for Ecosystems

Do the seasonal shifts in CO2 levels that result from seasonal differences in photosynthetic rates predominating in the Northern Hemisphere explain the trend for annual CO2 levels (increasing over time, in this graph from 2006 to 2011)?

a. Yes

b. No

c. I don’t understand the question.

Concept 46.4 Biogeochemical Cycles Affect Global Climate

Discuss the validity of the following statements regarding the greenhouse effect:

• Prior to the industrial revolution (starting around 1880), Earth had no carbon dioxide in its atmosphere.

• The composition and thickness of a planet’s atmosphere affect its surface temperatures.

• Air temperature is the only factor influenced by the changing composition of Earth’s atmosphere.

Concept 46.4 Biogeochemical Cycles Affect Global Climate

Which of the following statements are true regarding the greenhouse effect?

a. Prior to the industrial revolution (starting around 1880), Earth had no carbon dioxide in its atmosphere.

b. The composition and thickness of a planet’s atmosphere affect its surface temperatures.

c. Air temperature is the only factor influenced by the changing composition of Earth’s atmosphere.

d. All of the above

e. None of the above

Concept 46.5 Rapid Climate Change Affects Species and Communities

Corals, which secrete calcareous skeletons that over time form the large physical structure of reef communities, rely on a mutualism with a photosynthetic alga, and without this mutualism they cannot grow. Reefs have the highest biodiversity within marine ecosystems, and are important for supporting fisheries. Reef organisms have evolved over hundreds of millions of years to cope with recurring disturbance, damage, and destruction, followed by recovery or regrowth. However, recent climate change appears to be occurring at rates faster than reefs can tolerate.

Reefs are temperature-sensitive and a rise in temperature as small as 1 degree Celsius can result in “bleaching,” as algae react to the warmer water by producing oxygen compounds that are toxic to the coral, resulting in the coral ejecting their algal support system, leaving the reefs starved of nutrients and deathly white.

Concept 46.5 Rapid Climate Change Affects Species and Communities

If climate change is predicted to raise ocean temperatures by 1–3°C by the year 2050, what impact do you expect this might have on coral reef ecosystems?

Discuss.

Concept 46.5 Rapid Climate Change Affects Species and Communities

If climate change is predicted to raise ocean temperatures by 1–3°C by the year 2050, which of the following outcomes might you expect?

a. More bleaching events will occur.

b. Corals will be less able to grow.

c. Coral reefs may almost entirely disappear by 2050.

d. Fisheries will decline.

e. All of the above

Concept 46.6 Ecological Challenges Can Be Addressed through Science and International Cooperation

Do you think that indefinite economic growth is possible given the ecological limits of our planet?

a. Yes

b. No

c. I don’t understand this question.