Study Notes 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. Organisms have an optimum range for each factor where they can maintain homeostasis. Outside of this range, organisms may experience:

    • Physiological stress

    • Limited growth

    • Reduced reproduction

    • In extreme cases, death.

  • STB-3.B.2: Coral reefs suffer damage due to various factors, including:

    • Increasing ocean temperature

    • Sediment runoff

    • Destructive fishing practices.

  • STB-3.B.3: Oil spills in marine waters result in organism death due to hydrocarbons in oil:

    • Oil floats on water can coat feathers of birds and fur of marine mammals.

    • Some components of oil sink, killing bottom-dwelling organisms.

  • STB-3.B.4: Oil washing up on beaches poses economic consequences for fishing and tourism industries.

  • STB-3.B.5: Oceanic dead zones are low oxygen areas caused by increased nutrient pollution.

  • STB-3.B.6: An oxygen sag curve is a plot of dissolved oxygen levels versus distance from a source of pollution, often due to excess nutrients and biological refuse.

  • STB-3.B.7: Heavy metals, often from industrial activities such as mining and burning fossil fuels, can reach groundwater, impacting drinking water supply.

  • STB-3.B.8: Litter reaching aquatic ecosystems, while unsightly, can:

    • Create intestinal blockages and choking hazards for wildlife

    • Introduce toxic substances into the food chain.

  • STB-3.B.9: Increased sediment in waterways can:

    • Reduce light infiltration, affecting primary producers and visual predators

    • Settle and disrupt habitats.

  • STB-3.B.10: Elemental sources of mercury enter aquatic environments, where bacteria convert it to highly toxic methylmercury.

Organisms and Range of Tolerance

  • Aquatic organisms possess a range of tolerance for pollutants:

    • Many aquatic insects are intolerant to low levels of dissolved oxygen (DO), high water temperatures, and high levels of sediment, leading to physiological stress.

    • Example: Stonefly nymphs need clear, cold water with low nutrients to survive and thrive. Their presence indicates clean water.

Oxygen Sag Curve

  • Different aquatic species have varying tolerances for oxygen:

    • The species found in a river changes as the dissolved oxygen levels increase or decrease based on organic matter present.

Coral Reefs – Background

  • Coral reefs are formed in clear, warm coastal waters of tropical areas.

    • Among the world’s oldest, most diverse, and productive ecosystems.

    • Michigan’s geological composition includes limestone beds from ancient coral reefs, exemplified by the state stone, the Petoskey Stone composed of fossilized coral (Hexagonaria percarinata).

Coral Reefs – Formation

  • Coral reefs are created by massive colonies of tiny animals (polyps):

    • Polyps secrete a protecting crust of calcium carbonate (limestone) around their bodies.

    • Upon death, their empty crusts remain, supporting further reef growth.

    • This forms a network providing habitat for a variety of marine organisms.

Coral and Zooxanthellae

  • Coral reefs exist due to a mutually beneficial relationship between:

    • Polyps and single-celled algae (zooxanthellae):

    • Algae provide food and oxygen through photosynthesis and assist in calcium carbonate production.

    • Provide stunning coloration to reefs.

    • Polyps offer a protected home and some nutrients to algae.

Vulnerability of Coral Reefs

  • Coral reefs are easily disrupted and grow slowly:

    • Soil and material runoff clouds water, blocking sunlight necessary for algae photosynthesis.

    • Need a water temperature between 18-30 degrees Celsius (64-86°F) and low acidity.

    • Climate change poses a long-term threat by raising water temperatures beyond tolerance limits.

Importance of Coral Reefs

  • Ecosystem services offered:

    • Natural barriers against flooding and erosion for 15% of coastlines.

    • Habitat and food source for many ocean organisms, contributing to a significant portion of global fish catch.

    • Tourism and fishing industry contribute billions of dollars annually.

    • Coral reefs support:

    • 25% of all marine life despite covering less than 1% of ocean floor.

    • Approximately 250,000 known species, including over 4,000 fish and 700 coral species.

    • Scientists estimate over 1 million species are associated with coral reefs.

Coral Bleaching

  • Pollution and rising water temperatures lead to coral bleaching, causing the death of algae that provide essential nutrients to corals:

    • Resulting in the death of coral polyps and leaving behind a white calcium carbonate skeleton.

Ocean Acidification

  • Ocean acidification occurs as oceans absorb CO₂ from the atmosphere:

    • CO₂ reacts with seawater to form carbonic acid (H₂CO₃), which reduces carbonate ions (CO₃²⁻), vital for coral formation and shells of marine organisms.

    • Increased acidity may dissolve corals and impact biodiversity and food webs of coral reefs.

Mechanisms of Ocean Acidification

  • Ocean absorbs CO₂ from burning fossil fuels, transforming it into carbonic acid:

    • Low concentrations of carbonate hinder calcifiers, affecting growth and reproduction of corals and other shellfish.

    • Waters exhibiting acidic conditions affect organisms' ability to flourish and reproduce, disrupting marine ecosystems.

Effects of Acidification on Marine Life

  • Acidification results in:

    • Increased mortality in various marine species including clams, lobsters, scallops, and some fish.

    • Alters behavior of finfish.

    • Susceptibility of plankton (base of the food chain) impaired by decreased carbonate levels, leading to significant implications for all marine trophic levels.

Other Threats to Coral Reefs

  • Anthropogenic activities harm coral reefs, including:

    • Overfishing, destructive fishing practices (e.g., dynamite, cyanide), and collection for aquarium trade.

    • Land-based runoff from dredging, coastal development, agricultural activities, and sewage treatment generates sediments, nutrients, and pollutants, promoting algal growth that can smother corals.

Ocean Pollution from Oil

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

    • Human sources include tanker accidents and offshore drilling rig blowouts.

Natural Sources of Ocean Oil Pollution

  • Natural releases from oceanic seeps account for significant oil presence in waters:

    • Scientists estimate approximately 60% in North America and 45% worldwide from natural sources.

Case Study: Exxon Valdez Oil Spill

  • One of the most notorious oil spills occurred in 1989, resulting from a tanker running aground and spilling 11 million gallons of crude oil along the Alaskan coastline:

    • Consequences included the death of 250,000 seabirds, 2,800 sea otters, 300 harbor seals, and impact on commercial fishing industries.

  • Recovery challenges:

    • Many affected populations rebounded; however, killer whale and sea otter populations struggled.

Factors Affecting Oil Breakdown

  • Oil breaks down slower in cold environments:

    • Estimates show oil from the Exxon Valdez spill could take over 100 years to fully decompose.

Offshore Oil Drilling

  • An estimated 5,000 offshore oil platforms exist in North America:

    • Drilling activities often lead to leaks.

Oil Pollution from Surface Runoff

  • A considerable amount of oil pollution originates from land runoff:

    • Factors include industrial activities and urban runoff.

Factors Influencing Oil Spill Impact

  • The type of oil (crude vs refined), ecosystem type affected, distance from shore, season, weather conditions, temperature, and ocean currents play critical roles in oil's environmental effects.

Temperature's Role in Recovery from Oil Spills

  • Recovery from oil spills is usually faster in warmer waters compared to colder ones:

    • Anticipated faster dissipation for recent events like the BP Gulf oil spill than the Exxon Valdez disaster.

Long-Term Effects on Recovery from Oil Spills

  • Recovery duration varies, with gulfs and bays taking longer to recover than open oceans:

    • Many marine life forms recover quickly (within 3 years), while marine mammals may take 10-15 years post-exposure.

Cleanup Methods for Oil Spills

  • Three main approaches exist for oil spill remediation:

    • Mechanical Methods: Use of barriers to contain oil and suction off from the water's surface.

    • Chemical Methods: Involves dispersing oil to facilitate easier removal or sinking.

    • Biological Methods: Natural bacterial action can biodegrade oil, with ongoing research exploring genetically modified bacteria for more efficient clean-up.

Challenges in Shoreline Oil Spill Cleanup

  • Various factors including beach type, water temperature, and ecosystem type impact the effectiveness of oil spill response strategies.

Consequences for Shoreline Ecosystems

  • Shoreline cleaning methods may destroy local plant and animal life and nutrient-rich sediments, hindering recovery.

Effects of Oil Pollution on Marine Life

  • Oil's impact on organisms includes:

    • Debris from oil spills can smother bottom-dwelling organisms and render them inedible.

    • Volatile hydrocarbons cause immediate deaths in many aquatic species, especially in their larval stages.

    • Oil coatings disrupt insulation and buoyancy in birds and mammals, leading to deaths through drowning or exposure.

Additional Oil Spill Events

  • In 2010, a substantial oil spill occurred in Michigan's Kalamazoo River, releasing nearly a million gallons of crude oil from a ruptured pipeline:

    • Concerns about aging pipelines in regions like the Straits of Mackinac raised alarms about potential environmental impacts.

Oxygen-Demanding Waste

  • Organic matter entering water bodies increases microbial growth, leading to oxygen depletion:

    • Major sources include sewage, animal wastes, and organic residues from industrial processes.

Effects of High Oxygen-Demand Waste

  • Decomposing organic matter can create hypoxic (low oxygen) or anoxic (no oxygen) zones, causing lethal conditions for fish and other aquatic organisms:

    • Raw sewage dumping leads to severe oxygen depletion and dead zones in both freshwater and marine environments.

Biochemical Oxygen Demand (BOD)

  • BOD: Measures oxygen consumption in a water body over time, indicating pollution levels:

    • Low values signify less pollution; high values indicate significant pollution.

Inorganic Plant Nutrients

  • Water-soluble compounds (nitrates, phosphates) from sewage and fertilizers boost algae growth, leading to oxygen depletion upon decomposition:

    • Two most common inorganic plant nutrients are nitrates (NO₃⁻) and phosphates (PO₄³⁻).

Eutrophication

  • Eutrophication refers to nutrient enrichment of lakes from surrounding runoff:

    • Phosphorus is often the limiting factor in freshwater ecosystems.

  • Cultural Eutrophication occurs from anthropogenic nutrient inputs:

    • Resulting in algal blooms, oxygen depletion, and subsequent dead zones.

Example of Famous Dead Zones

  • The Gulf of Mexico's dead zone arises from nutrient influx from the Mississippi River, disrupting local marine life every summer:

    • Lake Erie experiences similar issues due to its shallow and highly populated watershed.

Reducing Cultural Eutrophication

  • Strategies include reducing nutrient inputs into waterways and enhancing sewage treatment efficiency:

    • Management practices for agriculture and effective farming techniques can further mitigate risks.

Managing Agricultural Runoff

  • Best practices involve minimizing fertilizer use, alternation of crops, implementing buffer zones, and runoff controls:

    • Addressing livestock waste management involves constructing lined lagoons to prevent groundwater contamination.

Characterization of Degradable Wastes

  • Degradable wastes, meaning organic matter that bacteria can break down, are termed oxygen-demanding wastes:

    • Rivers typically recover from moderate levels unless diluting non-degradable pollutants.

Oxygen-Sag Curve Dynamics

  • An oxygen-sag curve visualization indicates how dissolved oxygen levels fluctuate in relation to organic waste:

    • Consists of zones such as clean, septic, and recovery zones illustrating the impact of waste on aquatic habitats.

Recovery Process Factors

  • Stream recovery relates significantly to currents, water volume, and the inputs of heat or pollutants:

    • Fast flowing and voluminous waters recover from disturbances more effectively.

Temperature and Oxygen Proportions

  • As temperature rises, dissolved oxygen levels in rivers decrease:

    • The relationship between temperature and dissolved oxygen levels is inverse.

Impacts of Non-Degradable Waste

  • Polluted streams hold limited capacity to dilute slowly degradable pollutants:

    • Heavy metals (e.g., PCBs) cannot be adequately managed through natural processes due to persistence.

Mountaintop Coal Removal

  • Strip mining practices include dumping debris into stream valleys:

    • Streams sourced from these mines may become significantly acidic, posing threats to aquatic life.

Acid Mine Drainage Effects

  • Acidic water resulting from abandoned mines degrades quality of surrounding aquatic resources:

    • Acid mine drainage leads to low pH and can release toxic metals into surfaces or groundwater, harming the ecosystem.

Addressing Acidic Mine Drainage

  • Methods to resolve acid mine drainage impacts involve stream water treatment through limestone applications to enhance pH levels:

    • Issues stem from accountability as many responsible mining entities no longer operate.

Heavy Metals Overview

  • Heavy metals pose potential health threats due to their toxicity and ability to accumulate in biological systems:

    • Common pollutants include arsenic, cadmium, chromium, copper, nickel, lead, and mercury.

Lead Contamination Sources

  • Lead enters water via aging pipes and plumbing systems:

    • Notable cases like Flint highlight the risks of lead exposure to communities and infrastructure vulnerabilities.

Health Effects of Lead Exposure

  • Especially detrimental effects on fetuses and children include brain, nervous system, and kidney damage:

    • Long-term exposure can have severe implications, affecting health over time.

Arsenic Origins

  • Arsenic, naturally present in the Earth’s crust, can contaminate groundwater:

    • Mining activities can exacerbate these concentrations and pose health risks, including various cancers.

Regulating Arsenic in Water

  • Limitations on arsenic levels in drinking water are enforced by agencies like the EPA:

    • The historical reduction of the arsenic acceptable limit from 50 ppb to 10 ppb reflects ongoing health and safety concerns.

Global Arsenic Issues

  • In regions like Bangladesh, drinking groundwater poses substantial risks due to naturally occurring arsenic:

    • Affected populations have faced severe health problems due to prolonged consumption.

Coal Combustion Effects

  • Burning coal emits fly ash, which contains harmful heavy metals:

    • Coal ash disposal methods lack strict regulations, leading to widespread contamination risks.

Coal Ash Management

  • Coal ash is considered special waste and is poorly regulated, permitting hazardous disposal practices:

    • Problems culminate in spills and environmental risks associated with improper coal ash management.

Consequences of Heavy Metal Accumulation

  • Heavy metals accumulate in aquatic organisms causing health risks and environmental impacts:

    • Bioaccumulation in species poses threats to human health upon consumption through biomagnification.

Mercury Source and Impact

  • Mercury from burning fossil fuels constitutes the majority of anthropogenic releases:

    • Inorganic mercury is transformed into methylmercury in aquatic systems, posing toxicity risks to mammals and humans.

Human Consumption of Methylmercury

  • The primary exposure route for humans is through consuming contaminated fish:

    • Consumption advisories recommend caution particularly for vulnerable groups (children, pregnant women).

Regulatory Framework for Mercury Management

  • Importance of enforcing agreements to curb mercury emissions to enhance public health and environmental safety.

Sediment Dynamics

  • Sediments are particles from erosion and sedimentation contributing to various ecosystems:

    • While sediment transport is natural, human activity can exacerbate sedimentation, disrupting aquatic habitats.

Sediment Pollution Sources

  • Human-induced activities increase sediment volume entering waterways:

    • Activities include construction, agriculture, and land usage changes which contribute to increased erosion.

Effects of Sediment Clouding

  • Increased sediment load in water bodies cause:

    • Aesthetic degradation of waterways and reduced visibility affecting aquatic life.

Impacts of Sediment on Aquatic Life

  • Sedimentation impacts light penetration essential for photosynthesis:

    • Clogging of gills in aquatic organisms, making respiration difficult.

Nutrient Enrichment from Sediments

  • Sediments often carry nutrients that can contribute to further pollution, creating a negative feedback loop:

    • Significant economic costs are linked to sediment pollution and environmental damage.

Mitigation Strategies for Sediment Pollution

  • Strategies include maintaining vegetation buffers and minimizing soil erosion through appropriate agricultural practices:

    • Protection of riparian habitats plays a critical role in preserving water quality.

Solid Waste Pollution Overview

  • Consists of improperly disposed of materials that pose direct toxicity risks:

    • Address disposal in landfills and the implications of solid waste exposure to aquatic systems.

Solid Waste Disposal Practices

  • Highlighting disparity in solid waste treatment between regions, leading to pollution incidents:

    • Examples include recurring plastic debris issues in marine ecosystems.

Great Pacific Garbage Patch

  • A major concentration of plastics located in the North Pacific Ocean, illustrating persistent waste management issues:

    • Represents a portion of the larger issue surrounding marine debris accumulation.

Dangers of Solid Waste in Waterways

  • Marine debris endangers wildlife and damages ecosystems:

    • Public safety concerns arise from medical waste washes ashore and general pollution from discarded materials.

Microplastics Introduction

  • Microplastics are plastic particles smaller than 5mm, derived from various sources:

    • Health implications are still under investigation, highlighting the need for awareness of pollutants in the human food chain.

Concluding Thoughts on Plastic Pollution

  • Emphasizing personal responsibility in reducing plastic use and considering consumption habits:

    • Calls for community actions to address plastic waste effectively.