Marine Biology Unit 16 Review: Climate Change Effects on Marine Ecosystems

Key Concepts and Terminology

• Climate change refers to long-term shifts in global or regional climate patterns, primarily attributed to increased levels of atmospheric carbon dioxide produced by the use of fossil fuels
• Greenhouse gases, such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), trap heat in the Earth's atmosphere, leading to global warming
• Ocean acidification occurs when the ocean absorbs excess atmospheric CO2, causing a decrease in seawater pH and carbonate ion concentration
• Sea level rise is the increase in the average level of the Earth's oceans due to the melting of glaciers and ice sheets, as well as the thermal expansion of seawater
• Ocean circulation patterns, such as the global conveyor belt, redistribute heat and nutrients around the planet, influencing climate and marine ecosystems
• Marine biodiversity encompasses the variety of life in the ocean, including species richness, genetic diversity, and ecosystem diversity
• Resilience is the ability of an ecosystem or species to recover from disturbances and adapt to changing environmental conditions
• Adaptation strategies involve the adjustment of natural or human systems in response to actual or expected climate change effects, aiming to moderate harm or exploit beneficial opportunities

Climate Change Basics

• The Earth's climate is regulated by the balance between incoming solar radiation and outgoing infrared radiation
• Human activities, primarily the burning of fossil fuels and deforestation, have increased the concentration of greenhouse gases in the atmosphere
• The greenhouse effect is the process by which greenhouse gases absorb and re-emit infrared radiation, trapping heat in the Earth's atmosphere
• Global warming refers to the long-term increase in the Earth's average surface temperature due to the enhanced greenhouse effect
• Climate change impacts various aspects of the Earth's systems, including the atmosphere, oceans, cryosphere, and biosphere
• Positive feedback loops, such as the ice-albedo feedback and the permafrost carbon feedback, can amplify the effects of climate change
• Tipping points in the Earth's climate system, such as the collapse of the West Antarctic Ice Sheet or the shutdown of the Atlantic Meridional Overturning Circulation, could lead to abrupt and irreversible changes

Ocean Warming and Its Impacts

• The ocean absorbs over 90% of the excess heat trapped by greenhouse gases, leading to rising ocean temperatures
• Increasing ocean temperatures cause thermal expansion of seawater, contributing to sea level rise
• Warmer oceans lead to more frequent and intense tropical cyclones and hurricanes
• Ocean warming alters the distribution and abundance of marine species, with many species shifting their ranges towards the poles or to deeper waters
• Coral bleaching occurs when high water temperatures stress coral reefs, causing the expulsion of symbiotic algae and potentially leading to coral mortality
  • Mass coral bleaching events, such as those in the Great Barrier Reef, can result in widespread coral reef degradation
• Ocean warming reduces the solubility of oxygen in seawater, leading to the expansion of oxygen minimum zones and affecting marine life
• Warmer temperatures can disrupt the timing of biological events, such as phytoplankton blooms and fish spawning, leading to mismatches in marine food webs

Ocean Acidification

• Ocean acidification is the ongoing decrease in the pH of the Earth's oceans, primarily caused by the absorption of atmospheric CO2
• When CO2 dissolves in seawater, it forms carbonic acid (H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-)
  • The increased concentration of H+ ions lowers the pH of seawater, making it more acidic
• Ocean acidification reduces the availability of carbonate ions (CO32-), which are essential for calcifying organisms to build their shells and skeletons
• Calcifying organisms, such as corals, mollusks, and some plankton, are particularly vulnerable to ocean acidification
  • Reduced calcification rates can lead to weaker shells and skeletons, increased vulnerability to predation, and reduced growth and survival
• Ocean acidification can alter the behavior, physiology, and gene expression of marine organisms, affecting their fitness and survival
• The impacts of ocean acidification can propagate through marine food webs, potentially affecting fisheries and ecosystem services
• Some marine organisms, such as seagrasses and certain phytoplankton species, may benefit from increased CO2 levels, leading to changes in community composition

Sea Level Rise and Coastal Ecosystems

• Sea level rise is caused by the thermal expansion of seawater and the melting of land-based ice, such as glaciers and ice sheets
• Coastal ecosystems, such as wetlands, mangroves, and salt marshes, are particularly vulnerable to sea level rise
• Rising sea levels can lead to increased coastal flooding, erosion, and saltwater intrusion into freshwater aquifers
• Coastal wetlands act as natural buffers against storm surges and provide critical habitats for many species
  • As sea levels rise, coastal wetlands may be submerged or forced to migrate inland, depending on the rate of sea level rise and the availability of suitable habitat
• Mangrove forests are important carbon sinks and provide nursery grounds for many marine species
  • Sea level rise can cause mangrove forests to retreat inland or become submerged, leading to the loss of these valuable ecosystems
• Saltwater intrusion into freshwater habitats can alter the distribution and abundance of species, favoring salt-tolerant organisms
• Coastal infrastructure, such as roads, buildings, and ports, is at risk from sea level rise and increased coastal flooding
• Nature-based solutions, such as the restoration of coastal wetlands and the construction of living shorelines, can help mitigate the impacts of sea level rise

Changes in Ocean Circulation

• Ocean circulation patterns, driven by wind, density differences, and the Earth's rotation, play a crucial role in redistributing heat, nutrients, and dissolved gases around the planet
• The global conveyor belt, also known as the thermohaline circulation, is a large-scale ocean circulation pattern that transports warm surface waters towards the poles and cold, deep waters towards the equator
  • Changes in the global conveyor belt can have significant impacts on global climate and marine ecosystems
• Climate change can alter ocean circulation patterns by affecting the density of seawater through changes in temperature and salinity
• The Atlantic Meridional Overturning Circulation (AMOC) is a major component of the global conveyor belt, transporting warm, salty water from the tropics to the North Atlantic
  • A slowdown or collapse of the AMOC could lead to cooling in Europe, changes in rainfall patterns, and a reduction in ocean carbon uptake
• Changes in wind patterns, such as the strengthening or weakening of trade winds, can affect surface ocean currents and upwelling systems
• Upwelling systems, such as those along the west coasts of continents, bring nutrient-rich deep waters to the surface, supporting high biological productivity
  • Changes in the intensity or frequency of upwelling events can affect the productivity and composition of marine ecosystems
• Altered ocean circulation patterns can affect the distribution and dispersal of marine organisms, particularly those with planktonic larvae

Effects on Marine Biodiversity

• Climate change is a major driver of changes in marine biodiversity, affecting species distribution, abundance, and interactions
• Ocean warming leads to poleward shifts in the distribution of many marine species, as they seek cooler waters
  • Species with limited dispersal abilities or specific habitat requirements may be unable to keep pace with the rate of climate change, leading to local extinctions
• Ocean acidification can negatively impact the survival, growth, and reproduction of calcifying organisms, such as corals, mollusks, and some plankton
  • The decline of these organisms can have cascading effects on marine food webs and ecosystem functioning
• Changes in ocean circulation patterns can alter the distribution of nutrients and dissolved oxygen, affecting primary productivity and species distribution
• Climate change can lead to the expansion or contraction of suitable habitats for marine species, influencing their abundance and interactions
• Shifts in the timing of biological events, such as phytoplankton blooms and fish spawning, can lead to mismatches in marine food webs
  • These mismatches can affect the survival and recruitment of commercially important fish species
• Invasive species may benefit from changing environmental conditions, allowing them to expand their ranges and outcompete native species
• The cumulative impacts of climate change, along with other stressors such as overfishing and pollution, can lead to the loss of marine biodiversity and the degradation of ecosystem services

Adaptation and Resilience Strategies

• Adaptation strategies aim to reduce the vulnerability of marine ecosystems and human communities to the impacts of climate change
• Marine protected areas (MPAs) can serve as refugia for species and help maintain ecosystem resilience
  • Designing MPA networks that consider future climate conditions and species range shifts can enhance their effectiveness
• Ecosystem-based management approaches, which consider the complex interactions between species and their environment, can help build resilience to climate change
• Restoring and protecting coastal ecosystems, such as mangroves, seagrasses, and salt marshes, can provide natural buffers against sea level rise and storm surges
• Nature-based solutions, such as living shorelines and artificial reefs, can help mitigate the impacts of climate change while providing habitat for marine species
• Assisted migration, which involves the intentional movement of species to more suitable habitats, may be necessary for some species unable to keep pace with climate change
• Reducing other stressors, such as overfishing, pollution, and habitat destruction, can increase the resilience of marine ecosystems to climate change
• Incorporating climate change projections into fisheries management and coastal planning can help anticipate and mitigate future impacts
• Engaging local communities and stakeholders in adaptation planning and decision-making can help build social resilience and ensure the equitable distribution of resources

Future Projections and Research Directions

• Climate models project continued warming of the Earth's surface and oceans under various greenhouse gas emission scenarios
  • The rate and magnitude of future climate change will depend on the effectiveness of global efforts to reduce greenhouse gas emissions
• Sea level rise is projected to accelerate in the coming decades, with estimates ranging from 0.3 to 1.1 meters by 2100, depending on the emission scenario
  • The collapse of the West Antarctic Ice Sheet or the rapid melting of the Greenland Ice Sheet could lead to even higher sea level rise
• Ocean acidification is expected to intensify as atmospheric CO2 levels continue to rise, with potentially severe consequences for calcifying organisms and marine ecosystems
• Changes in ocean circulation patterns, such as the weakening of the Atlantic Meridional Overturning Circulation, are projected to have significant impacts on global climate and marine ecosystems
• Species distribution models predict continued poleward shifts and changes in the abundance of marine species in response to ocean warming
  • The ability of species to adapt to rapid climate change remains a critical uncertainty
• Projections indicate an increased risk of coral bleaching and mortality, with the potential loss of most coral reefs under high emission scenarios
• The cumulative impacts of climate change and other anthropogenic stressors are expected to lead to further declines in marine biodiversity and ecosystem functioning
• Future research should focus on improving our understanding of the complex interactions between climate change, marine ecosystems, and human activities
  • This includes refining climate models, developing new monitoring technologies, and studying the adaptive capacity of marine organisms and ecosystems
• Interdisciplinary research, integrating natural and social sciences, is necessary to develop effective adaptation and mitigation strategies that consider the needs of both marine ecosystems and human communities