test prep 2/6/25 test

Salinity

• Definition of Salinity: The concentration of salt dissolved in seawater. Important for understanding ocean currents and climate.

Importance of Salinity

• Drives ocean circulation: Saltwater is denser than freshwater; it sinks, creating currents.

• Essential for marine life: Affects the habitat and survival of aquatic organisms.

Impact of Salinity Monitoring

• Understanding environmental changes: Monitoring salinity helps discern weather patterns and climate changes.

Units of Measurement

• Expressed in parts per thousand (ppt).

• Average seawater salinity: About 35 ppt (3.5%), with variations from 34 to 37 ppt.

• Conversion: 35 ppt is equal to 3.5 parts per hundred (3.5%).

• Example calculations: A salinity of 35 ppt means there are 35 grams of salt in every kilogram of seawater.

Composition of Ocean Salts

• Major ions include sodium (Na+) and chloride (Cl-), together making up 85-90% of ocean salts.

• Three main salts in seawater:

  • Sodium chloride (NaCl) - ~85%

  • Magnesium chloride (MgCl2) - ~10%

  • Calcium sulfate (CaSO4) - ~4%

Sources of Ocean Salinity

• Natural Processes:

  • Rain dissolves salts from rocks, transporting them via rivers to the ocean.

  • Hydrothermal vents release sea salts and minerals into the ocean.

Measuring and Calculating Salinity

• Measures to calculate salinity: Sea Surface Temperature (SST) and the density of seawater.

• Instruments:

  • Thermometer for SST.

  • Hydrometer for density.

  • Refractometer for measuring salinity.

• Salinity charts: Cross-reference temperature and density to find salinity values.

Effects of Temperature and Salinity on Marine Life

• Temperature: Affects metabolic rates and habitat suitability; extreme temperatures threaten species survival.

• Salinity: Regulates osmotic balance in marine organisms; changes in salinity can lead to cellular stress and death in sensitive species.

Climate Change and Ocean Acidification

Climate Change

• Definition: Long-term shifts in temperature and weather patterns primarily caused by human activities, including fossil fuel combustion.

• Greenhouse Gases: Major contributors include carbon dioxide (CO2) and methane (CH4).

  • Effects: Leads to global warming, impacting weather, sea levels, and ecosystems.

Ocean Acidification

• Definition: Decrease in ocean pH due to increased CO2 absorption from the atmosphere.

• Chemical Mechanism:

  • CO2 + H2O -> H2CO3 (carbonic acid) -> HCO3- + H+ (bicarbonate and hydrogen ions).

  • Increased H+ ions lower pH, making ocean water more acidic.

• Impact on Marine Life:

  • Especially affects shell-forming organisms; they rely on carbonate (CO3^2-) ions for shell production.

  • As more CO2 is absorbed, carbonate ions are depleted, making it harder for organisms to build shells.

Importance of pH in Ocean Chemistry

• Normal seawater pH: Ranges from 8.1 to 8.3 (slightly alkaline).

• Small changes in pH can significantly impact marine ecosystems and organisms, especially coral reefs.