Study Guide on Human Impacts on Ecosystems

Topic 8.2 - Human Impacts on Ecosystems

Enduring Understanding

  • STB-3: Human activities, including the use of resources, have physical, chemical, and biological consequences for ecosystems.

Learning Objective

  • STB-3.B: Describe the impacts of human activities on aquatic ecosystems.

Essential Knowledge

  • STB-3.B.1: Organisms have a range of tolerance for various pollutants. Each organism has an optimal range for factors like temperature and chemical composition that allows it to maintain homeostasis.

    • Outside of this optimal range, organisms may experience:

    • Physiological stress

    • Limited growth

    • Reduced reproduction

    • Death in extreme cases.

  • STB-3.B.2: Coral reefs are suffering damage due to multiple factors:

    • Increased ocean temperatures

    • Sediment runoff

    • Destructive fishing practices.

  • STB-3.B.3: Oil spills in marine waters cause the death of organisms due to hydrocarbons in oil:

    • Oil covering the surface can coat the feathers of birds and fur of marine mammals.

    • Components of oil that sink can destroy bottom-dwelling organisms.

  • STB-3.B.4: Oil on beaches can lead to economic repercussions for industries such as fishing and tourism.

  • STB-3.B.5: Oceanic dead zones are regions of low oxygen in oceans, primarily caused by nutrient pollution.

  • STB-3.B.6: The oxygen sag curve is a graphical representation of dissolved oxygen levels plotted against distance from a pollution source featuring excess nutrients and biological refuse.

  • STB-3.B.7: Heavy metals from industry (especially mining and fossil fuel combustion) can contaminate groundwater, affecting drinking water supplies.

  • STB-3.B.8: Litter affects aquatic ecosystems:

    • It creates intestinal blockages and choking hazards for wildlife.

    • It introduces toxic substances into the food chain.

  • STB-3.B.9: Increased sediment in waterways impairs light infiltration, affecting primary producers and disrupting habitats.

  • STB-3.B.10: Elemental mercury entering aquatic environments can be converted by bacteria into highly toxic methylmercury.

Organisms and Range of Tolerance

  • Aquatic organisms demonstrate varying tolerances to pollutants.

  • Examples:

    • Many aquatic insects, such as stonefly nymphs, need clear, cold water with low nutrient levels to thrive and are good bioindicators of clean water.

Oxygen Sag Curve

  • The species composition in a river shifts with changes in dissolved oxygen due to organic matter levels, linking diversity directly to oxygen levels.

Coral Reefs: Background

  • Coral reefs develop in clear, warm coastal waters in tropical regions and are among the oldest and most productive ecosystems.

  • In Michigan, large limestone deposits originated from ancient coral reefs, with the state stone, the Petoskey Stone, representing fossilized coral (Hexagonaria percarinata).

Coral Reefs Formation

  • Coral reefs are built by coral polyps (related to jellyfish) that secrete calcium carbonate, forming protective crusts.

  • Upon the death of polyps, their remains contribute to the reef structure, which serves as a habitat for various marine life.

Coral and Zooxanthellae

  • Coral reefs thrive due to a symbiotic relationship between polyps and zooxanthellae (single-celled algae).

    • Zooxanthellae provide food via photosynthesis and assist corals in producing calcium carbonate, contributing to their coloration.

    • Polyps provide a protective habitat for zooxanthellae and supply some nutrients.

Vulnerability of Coral Reefs

  • Coral reefs are at high risk due to slow growth and sensitivity to disturbances.

    • Runoff can block sunlight, essential for zooxanthellae's photosynthesis.

    • Optimal temperatures are between 18-30 °C (64-86 °F); acidity levels must remain low.

    • Climate change poses a long-term threat by raising ocean temperatures.

Importance of Coral Reefs

  • Coral reefs offer critical ecosystem services:

    • They protect coastlines (15% of the world's coastlines) from erosion and floods.

    • They ensure habitats, food, and spawning grounds for marine life and contribute significantly to global fish catches.

    • They stimulate industries (tourism, fishing) worth billions each year.

Coral Reefs Ecosystem Services

  • Food & Fishing: Coral reefs sustain fish and shellfish populations that provide protein for over a billion people.

  • Tourism & Recreation: Attract millions yearly, generating substantial income.

  • Coral Reef Medicine: Coral species are being explored for medical compounds, particularly in cancer research.

  • Coastal Protection: Natural barriers against storm damage.

  • Biodiversity: Support 25% of all marine life, though they cover less than 1% of the ocean floor, housing about 250,000 known species including over 4,000 fish species and 700 coral species.

Coral Bleaching

  • Increased pollution and ocean temperature can lead to coral bleaching, where algae die off, leaving corals without nourishment and leading to their eventual death.

Ocean Acidification

  • Rising CO2 levels lead to ocean acidification:

    • CO2 reacts with water to form carbonic acid (H2CO3), decreasing carbonate ion availability essential for coral and marine organisms.

    • Increased acidity threatens reproduction and survival of species; potential for gradual dissolution of corals and shells.

Ocean Acidification Summary

  • Key processes:

    • CO2 from fossil fuels increases ocean absorption, generating significant acidity.

    • Increased hydrogen ion concentration diminishes shell-building capabilities, impacting marine biodiversity.

Other Threats to Coral Reefs

  • Anthropogenic activities such as:

    • Overfishing (destructive practices like dynamite and cyanide fishing)

    • Land runoff from agricultural development, urbanization, and pollution discharge.

Ocean Pollution from Oil

  • Crude oil and refined petroleum reach oceans from both natural and human sources:

    • Notable sources include tanker accidents and offshore drilling.

Exxon Valdez Disaster

  • In 1989, the Exxon Valdez spill released 11 million gallons of crude oil off Alaska:

    • Consequences included severe ecological impact:

    • Death of 250,000 seabirds, 2,800 sea otters, and 300 harbor seals.

  • Regulations were established post-disaster requiring tankers to have double-hull designs to minimize spill risk.

Oil Spills in Cold Environments

  • Oil degrades slowly in cold waters, potentially remaining for over 100 years post-spill.

Offshore Oil Drilling and Pollution

  • Thousands of offshore oil platforms exist globally, often experiencing leaks that contribute to ocean pollution.

Temperature and Recovery from Oil Spills

  • Recovery is typically quicker in warmer waters, as seen in comparative oil spill incidents (e.g., Gulf and Exxon Valdez).

Effects of Oil on Aquatic Organisms

  • Heavy oil components can smother organisms and harm bottom-dwellers. \n- Immediate fatalities occur from volatile hydrocarbons present in oil spills, specifically targeting larval forms.

Impact Mechanism of Oil Coating

  • Oil destroys insulation and buoyancy in birds and mammals, leading to drowning or death from hypothermia.

Human-Made Oil Spills on Land

  • Significant spills also occur on land, such as the significant 2010 Kalamazoo River oil spill in Michigan.

Oxygen-Demanding Waste

  • Organic debris decomposing in bodies of water requires oxygen, leading to decreased dissolved oxygen levels and potentially creating hypoxic zones.

BOD (Biochemical Oxygen Demand)

  • Measured in water to reflect pollution levels; determines organic matter decomposition effectiveness in water bodies.

Inorganic Plant Nutrients

  • Nutrients like nitrates and phosphates lead to excessive algal growth and subsequent decay, depleting oxygen levels in water.

Eutrophication

  • Natural or cultural nutrient enrichment of water bodies due to runoff from land, causing algal blooms and oxygen depletion.

Cultural Eutrophication Effects

  • Accelerated algal blooms followed by hypoxic conditions leading to dead zones.

Reducing Cultural Eutrophication

  • Preventative measures include reducing nutrient inputs, enhancing sewage treatments, and mechanical removal of excess plant life.

Agricultural Runoff Management

  • Implementing sustainable agricultural techniques and creating buffer zones around water bodies can reduce runoff.

Solid Waste Pollution

  • Includes discarded materials and municipal waste; often improperly disposed of in oceans, leading to marine debris accumulation.

Great Pacific Garbage Patch

  • A large concentration of solid waste, primarily plastic, discovered in the North Pacific, raising concerns about pollution impacts.

Plastic Waste Impact

  • Marine organisms mistake plastics for food, leading to ingestion and potential toxic exposure within food chains.

Microplastics

  • Defined as plastic fragments less than 5mm, originating from a variety of sources, harming ecosystems and potentially entering human food systems.

Solutions to Plastic Pollution

  • Small actions to reduce usage and waste, such as selecting eco-friendly materials and reducing plastic consumption.