Topic-2.3---L3-Ocean-Acidification

Coral Health and Bleaching

  • Healthy and dead coral visible on reefs can indicate environmental stress.

  • Coral Bleaching: Caused by factors such as:

    • Increase in ocean temperatures.

    • Changes in specific pH levels.

Ocean Acidification Lab Overview

  • Learning Objectives (LO):

    • Recall the term "ocean acidification".

    • Conduct experiments to investigate the impact of acidification on shelled organisms.

    • Discuss the effects of climate change and ocean acidification on aquatic ecosystems.

  • Impact of ocean acidification on coral reefs:

    • Damages coral structures, affecting overall biodiversity.

Role of Carbon in Ocean Chemistry

  • Carbon's critical role in ocean chemistry due to:

    • Absorption of carbon dioxide (CO₂) from the atmosphere.

    • Human activities (e.g., burning fossil fuels) release CO₂ into the atmosphere.

    • Excessive CO₂ can harm marine organisms.

Oceans as Carbon Sinks

  • Ocean Acidification: A major global concern.

    • Decrease in ocean pH due to human CO₂ emissions from burning fossil fuels.

    • Oceans absorb about half of produced CO₂ through wave action, mixing air into water.

    • Dissolved CO₂ forms carbonic acid, leading to acidification.

Ocean Carbon Cycle

  • Biological Pump:

    • Ocean harbors 50 times more CO₂ than the atmosphere.

    • Processes include:

      • Photosynthesis by phytoplankton consumes CO₂.

      • Microbial respiration releases CO₂.

Impact of Carbon Dioxide on Ocean pH

  • Dissolved CO₂ profiles carbonic acid in seawater, destabilizing pH levels.

  • Consequences:

    • Small pH decreases disrupt calcium carbonate deposition needed for:

      • Mollusc shells.

      • Coral skeletons (building materials for marine exoskeletons).

Ocean pH Levels

  • Decreasing mean seawater pH observed over time:

    • Historical data from Aloha station, Hawaii shows:

      • pH levels declining from 8.14 (1988) to 8.06 (2022).

Experimental Research Question

  • Research Question:

    • How do varying ocean pH levels affect the mass of clam shells (Acanthocardia tuberculata) over seven days?

  • Independent Variable (IV):

    • pH levels of ocean water through buffer solutions (8, 7, 6, 5, and 4).

  • Dependent Variable (DV):

    • Mass of shells measured with an electronic mass balance, assessed daily.

  • Controlled Variables:

    • Shell species.

    • Uniform water volume and beaker size.

    • Consistent salinity and temperature using probes.

Experimental Apparatus and Methodology

  • Equipment Needed:

    • pH probes, buffer solutions, beakers, seawater, electronic mass balance, clam shells, safety goggles, latex gloves, tongs, and paper towels.

  • Method:

    • Prepare beakers with seawater and label by pH.

    • Soak shells for 5 days to establish a baseline mass before adding pH solutions.

    • Measure mass post-treatment and collect data over a week.

Data Submission Task

  • Task: Graphing results from clam shell investigation.

    • Line graph showing average mass loss over trials.

    • Bar graph depicting % change in mass from beginning to day seven.

Ecological Impact of Climate Change

  • Bleaching Events: Climate change and ocean acidification threaten ecosystems:

    • Potential collapse of freshwater and marine populations.

  • Impact on Marine Life:

    • Sensitive ecosystems like coral reefs declining due to pH changes and slower coral exoskeleton formation.