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September 17, 2013

Acidifying Waters Pose Threat to Alaska’s Crab Populations

Crab fishing is one of the most lucrative businesses in Alaska’s frigid waters, but the changing chemistry of the North Pacific could soon cause disruption in Alaska’s two signature crab species, red king crab and snow crab.

The culprit: ocean acidification caused by carbon dioxide emissions.

Jeremy Mathis, a scientist at the National Oceanic and Atmospheric Administration (NOAA) said, “Anything in the ocean that builds a shell, whether it’s a crustacean like a crab, or a coral reef, need a certain amount of dissolved minerals that naturally exist in the ocean in order to build and maintain those shells. But as ocean acidification happens, it reduces the amount of those minerals that are available for those organisms.”

He and other NOAA scientists have found that the oceans have become 30 percent more acidic since the beginning of the Industrial Revolution.

To determine the effects of acidic water on crab populations, the scientists ran an experiment where they exposed baby red king crab to sea chemistry conditions that they predict will occur later this century. The results showed a significant increase in the crabs’ mortality rates, a loss in growth rate and a loss in calcification, or how quickly the crab was able to build its shell.

While there is no indication yet that the wild crabs are dying more rapidly than in the past, scientists fear what a more acidic future might bring, both for crabs and for other marine species.


Warm up questions
  1. What are carbon dioxide emissions? What produces them?
    • Answer: Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. Some of these human driven activities are electricity, transportation and industry.
    •  For a more thorough answer visit the EPA website
  2. “Carbon dioxide is constantly being exchanged among the atmosphere, ocean, and land surface as it is both produced and absorbed by many microorganisms, plants, and animals. However, emissions and removal of CO2 by these natural processes tend to balance. Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change by adding CO2 and other heat-trapping gases to the atmosphere.” (source: US Environmental Protection Agency)
    • Question: How do you think this trend has effected forests, our weather, and oceans?
  3. Hypothetical Question: What would happen if you put your hand in a giant vat of acid- specifically what would happen to your finger nails and bones?
Discussion questions
  1. How can we prove that ocean acidification is caused by an increase in carbon dioxide emissions?
  2. Why are crabs specifically sensitive to ocean acidification? What other species do you think are particularly ill-equipped to deal with the ocean’s changing PH?
  3. What other species of animals could suffer from ocean acidification? How does the loss of one species effect the food chain?
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