Oysters and Carbon Dioxide?

If you’ve been to SERC lately, you may have seen this strange plot off the right side of the dock:

Maybe you thought, ‘Why are those blue and green pool noodles arranged so elegantly in square formation? Why are there interns in SCUBA gear pulling up oyster shells? What is going on?!’

Thanks to Chesapeake Quarterly, we have answers. That square plot is the where Whitman Miller, a SERC scientist, is doing research on how ocean acidification affects oyster populations.

At the water testing station of Estuary Chesapeake, we measure the pH of the Rhode River and discuss how any deviation from neutral conditions can have a negative effect on aquatic biological processes. Whitman has taken this question and turned it into a full-blown scientific investigation.

Here’s a link to a preliminary study:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0005661.

Let’s break down his study into the 6 parts of the scientific method:
Question, Background Research, Hypothesis, Test the Hypothesis/Method, Analyze, Report your findings 

Question: Since all good scientific study starts with a question, here’s Whitman’s: What would happen to oysters in an acidifying Chesapeake? 

Background Research: What information and observations lead him to ask this question?

SERC is home to the longest running CO2 study on plant communities. In that study scientists created marsh chambers with elevated levels of CO2 to simulate what the atmosphere could be like in the future.  Now Tom Arnold, a chemical ecologist from Dickinson College, and Whitman Miller are taking the same idea and applying it to an aquatic animal: the oyster.

Research has revealed that higher levels of CO2 in the atmosphere are changing Earth’s climate. About a third of that CO2 ends up getting absorbed into the world’s oceans, causing reactions to change the chemistry of the water. When CO2 absorbs into water, it creates carbonic acid, which could make it hard for organisms like oysters to form their shells made of calcium carbonate. Here’s how it works:

To make matters worse, in areas like the Chesapeake Bay, an excess of nutrients like nitrogen and phosphorus can cause higher levels of CO2. Studies have investigated this issue in a marine (or ocean) settings, but there isn’t enough research on coastal and estuarine settings (like the Rhode River).

Hypothesis: If the acidity of the Bay’s waters continue to increase, then the growth rate of young oyster shells will decrease.

Test the Hypothesis/Method: Whitman and Tom used tanks to pump CO2 into the river bottom where baskets of young oysters were set up in order to raise the CO2 levels and simulate future conditions. They then measure the surface area of the shells, how fast the shells are growing, how fast the larvae are growing, and the chemical makeup of the shells.

Analyze: Data has shown that estuarine shell-forming organisms are vulnerable to the effects of more CO2 in the water, and that the effects are different across species- meaning, the conditions affect different types of oysters and other shelled organisms differently. However, Whitman has had to postpone research due to increased precipitation in early summer.

Report Your Findings: When charting the data he has so far, Whitman has found a 16% decrease in how fast native oyster mature in conditions simulating CO2 levels of the year 2100, and a 42% decrease in the amount of calcium in the shells. Whitman is still collecting data, so more conclusions will come in the future.

This kind of study deserves a lot of attention. For one, it attacks a hole in aquatic chemical ecology. Before this study, research on acidification in oceans had been just beginning, but acidification in coastal and estuarine zones was barely existent.

The study also deserves attention because it has implications for both economic and restoration efforts surrounding the Bay’s oyster populations. If oysters aren’t going to be able to grow their shells as strong or large, there will be less to sell AND there will be less places for new baby oysters to hook onto (check out this video to learn more about the life of oysters).

On the Estuary Chesapeake Field trip, we tell you how you are investigating an estuary alongside SERC researchers. This study shows you just that-

We test pH, they test pH— Scientists use some of the same methods we use to test pH to answer some of the questions we hypothesize about in our discussions at Station 2: Water Testing.

We use oyster baskets, they use oyster baskets— The same kinds of baskets we use, the ones that are hanging off the dock at Station 3: Oyster Bar Community, are the same kinds that Whitman and his team used to house the young oysters that were receiving extra CO2 gas.

We examine oyster shells, they examine oyster shells— The way we carefully make observations about the shape, size and organisms present on the oyster shells at Station 3: Oyster Bar Community is similar to how researchers examine the oysters that are part of their study.

If you and/or your class are interested in learning more about Whitman’s study, comment and ask some questions. We challenge you to trail blaze the issue of acidification in estuaries: come up with some great science questions that could lead to new research questions. Let these few questions get your brain moving…..

What other organisms might be affected? What other processes and conditions could make the situation worse? What can we do to help?

(Check out the original article published in Chesapeake Quarterly: An Acidifying Estuary? The “Other CO2 Problem”)

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