7 Environmental Systems and Ecosystem Ecology Part B PowerPoint® Slides prepared by Jay Withgott and Kristy Manning Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Ecosystems Ecosystem = all the interacting organisms and abiotic factors that occur in a particular place and time Energy and nutrients flow among all parts of an ecosystem. Conception of an ecosystem can vary in scale: small pond large forest entire planet

Landscape ecology Studies adjacent or interacting ecosystems on a larger geographic scale Many animals move between ecosystems; thus they must be studied on the landscape scale. Ecotones = transitional zones where ecosystems meet

Energy in ecosystems Energy from sun converted to biomass (matter in organisms) by producers through photosynthesis Rapid conversion = high primary productivity (coral reefs) Rapid plant biomass availability for consumers = high net primary productivity (wetlands, tropical rainforests)

Net primary productivity Different ecosystem types show varying net primary productivities.

Biogeochemical cycles Nutrients are elements and compounds that organisms consume and require for survival. Nutrients stimulate production by plants, and the lack of nutrients can limit production. Nutrients move through ecosystems in nutrient cycles or biochemical cycles.

Nutrients Macronutrients are elements and compounds required in relatively large amounts and include nitrogen, carbon, and phosphorous. Micronutrients are nutrients needed in small amounts.

The carbon cycle How carbon (C) moves through our environment • Producers pull carbon dioxide (CO2) from the air and use it in photosynthesis. • Consumers eat producers and return CO2 to the air by respiration. • Decomposition of dead organisms, plus pressure underground, forms sedimentary rock and fossil fuels. This buried carbon is returned to the air when rocks are uplifted and eroded. • Ocean water also absorbs carbon from multiple sources, eventually storing it in sedimentary rock or providing it to aquatic plants.

The carbon cycle

Human impacts on the carbon cycle We have increased CO2 in the atmosphere by burning fossil fuels and deforesting forests. Atmospheric CO2 concentrations may be the highest now than in 420,000 years. This is driving global warming and climate change.

The phosphorous cycle How phosphorus (P) flows through our environment P is most abundant in rocks. Weathering releases phosphate (PO43–) ions from rocks into water. Plants take up phosphates in water, pass it on to consumers, who return it to the soil when they die. Phosphates dissolved in lakes and oceans precipitate, settle, and can become sedimentary rock.

The phosphorous cycle

Human impacts on the phosphorus cycle We mine rocks containing phosphorus for inorganic fertilizers for use on crops and lawns. Treated and untreated sewage discharge contains phosphates, as do detergents. Those phosphates that run off into waterways can boost algal growth and cause eutrophication, altering the structure and function of aquatic ecosystems.

The nitrogen cycle How nitrogen (N) moves through our environment: • Atmospheric N2 is fixed by lightning or specialized bacteria, and becomes available to plants and animals in the form of ammonium ions (NH4+). • Nitrifying bacteria turn ammonium ions into nitrite (NO2–) and nitrate (NO3–) ions. Nitrate can be taken up by plants. • Animals eat plants, and when plants and animals die, decomposers consume their tissues and return ammonium ions to the soil. • Denitrifying bacteria convert nitrates to gaseous nitrogen that reenters the atmosphere.

The nitrogen cycle

Human impacts on the nitrogen cycle Haber and Bosch during WWI developed the Haber-Bosch process, a way to fix nitrogen artificially. Since then, synthetic nitrogen fertilizers have boosted agricultural production. Today we are fixing as much nitrogen artificially as the nitrogen cycle does naturally. We have thrown the nitrogen cycle out of whack.

Human impacts on the nitrogen cycle

Nitrogen and the dead zone Excess nitrogen flowing down the Mississippi River into the Gulf causes hypoxia, worse in some regions than others.

Nitrogen and the dead zone The size of the hypoxic zone in the northern Gulf of Mexico had grown since 1985, and was largest in 2002.

The hydrologic cycle How water flows through our environment: Water enters the atmosphere by evaporation and by transpiration from leaves. It condenses and falls from the sky as precipitation. It flows as runoff from the land surface into streams, rivers, lakes, and eventually the ocean. Water infiltrates into aquifers, becoming groundwater, the upper limit of which is the water table.

The hydrologic cycle

Impacts on the hydrologic cycle Human activity affects the water cycle. Examples: Damming rivers increases evaporation and can cause infiltration of surface water into aquifers. Altering vegetation increases surface runoff and erosion. Agricultural irrigation depletes water sources and increase evaporation.