The effects of ocean acidification

This exercise is a part of Educator Guide: Rising Carbon Dioxide Threatens Lake Food Webs / View Guide

1. Search for an article about the effects of ocean acidification on fish. Explain some of the research and results found by scientists.

Possible student response: The Science News article “Acid test points to coming fish troubles,” published 12/13/2011, describes the effects of increased ocean CO2 concentrations on fish eggs and hatchlings. In 2011 study, approximately 50 percent of silverside fish eggs hatched when they were incubated in water with a pH value equivalent to 410 parts per million (ppm) of CO2. In contrast, only 10 percent of eggs incubated in water with a pH value equivalent to 1,000 ppm CO2 hatched, and the resulting fish were smaller and more frequently malformed. In a separate experiment, larval cod that were raised in tanks with elevated CO2 concentrations (compared to the global average at the time) exhibited higher rates of death and severe organ damage to the liver, pancreas, kidney, gut and other organs.

2. How does ocean acidification affect oyster shell formation? Search for an article about the topic, and summarize the results.

Possible student response: The Science News article “Oysters may struggle to build shells as carbon dioxide rises,” published 6/17/2013, discusses how increased CO2 affects oysters. Oysters and many other marine organisms build shells out of calcium carbonate. Calcium carbonate is a solid in the normally alkaline ocean environment but is more soluble in an acidic environment. Researchers showed that as CO2 increases and ocean alkalinity decreases, the energy required for an oyster to build its shell increases exponentially. As of 2013, oyster hatcheries in the Pacific Northwest have already experienced severe production declines likely due to this factor.

3. How does ocean acidification affect phytoplankton? Find an article and summarize it.

Possible student response: The Science News article “Acidifying ocean may stifle phytoplankton,” published 1/14/2010, explores how increased ocean CO2 affects phytoplankton. The researchers tested the ability of four different species of phytoplankton to take up dissolved iron, an essential nutrient, in ocean water with various pH values. The results showed that if ocean pH drops by approximately 0.3 pH units, as is expected within a century, the ability of phytoplankton to metabolize iron will drop by 10 to 20 percent.

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