Heather Haberman: Gulf Water Health, July 12, 2011 (post #4)

  • NOAA Teacher at Sea
    Heather Haberman

    Onboard NOAA Ship Oregon II
    July 5 — 17, 2011

Mission:  Groundfish Survey
Geographical Location:  Northern Gulf of Mexico
Date:  Tuesday, July 11, 2011

Weather Data from  NOAA Ship Tracker
Air Temperature: 29.5 C   (85.1 F)
Water Temperature: 29.8 C  (85.6 F)
Relative Humidity: 76%
Wind Speed: 2.09 knots

Preface:  Scroll down the page if you would like to read my blog in chronological order.  If you have any questions leave them for me at the end of the post.

Question of the Day:  Are you seeing any oil rigs on your trip?

Answer:   There are so many oil rigs out here in the Gulf of Mexico that I can’t recall a time when I couldn’t see one.  Some are small and some are enormous.  I never realized that there were so many different engineering designs for oil rigs.  At night they are all lit up and it looks like a city in the sea out here.  All of the bright lights do pose some problems for migrating birds especially during bad weather when the are attracted to the lights.  The birds will often circle the lights to exhaustion or hit the structure so hard that it kills them.

Science and Technology Log

Topic of the Day:  How do researchers determine the health of the Gulf waters?

Science and Technology log:

You wake up in the morning and you don’t feel well.  What do you do?  Some people may stick a thermometer in their mouth to see if they have a fever.  Body temperature is a good indicator of illness or infection.  If you still don’t feel well after a few days you could visit a doctor who may check your eyes, ears, throat, blood pressure, etc.   Doctors can often figure out what’s making you sick by using certain tools and running tests.  Researchers do the same thing with the ocean.  In order to see how “healthy” the ocean is, measurements need to be taken.  Can you tell which trawl was from healthy water and which was from “sick” water?

0.5 kg (1.1 lbs) is all we got from this 30 minute trawl

Over 500 kg (1,100 lbs) of fish were collected in this 30 minute trawl.

Why aren’t we seeing a lot of marine life in certain parts of the Gulf of Mexico?  You don’t have to be a doctor to answer this question, but you do have to have some scientific tools to diagnose the problem.

On the Oregon II, a device called a CTD is used to take measurements such as conductivity (salinity), temperature, chlorophyll concentration, and dissolved oxygen (DO).  These water quality measurements let researches know what’s happening in the water just like a doctor would look at your test results to gage your health status.  Sometimes a doctor may need to do a second test just to confirm the results.  NOAA’s fisheries biologists do the same thing with their water quality assessments.  Winkler titrations and a hand-held Hack Dissolved Oxygen meter are used to confirm the dissolved oxygen readings from the CTD.  Scientists need to make sure the data they collect is accurate and the more tests they perform the better their data will be.

This large piece of equipment is a CTD sensor. The top portion of the machine contains three gray vertical cylinders which are used to collect water samples. Under the machine are sensors that test the water quality while it is submerged. Here I am washing out the sensors once it was brought back on board from a test.

When comparing data from this device to our trawl samples, it’s obvious that water with low levels of dissolved oxygen can not support much life.

Dissolved Oxygen: Marine animals need oxygen to survive just like land animals do.  The main difference is that most marine animals have gills which are able to diffuse oxygen molecules from the water directly into their blood.  Diffusion is the process of a molecule moving from an area of high concentration to low concentration.

Have you ever sprayed air freshener and noticed how the smell moves from where you sprayed it (high concentration) throughout the entire room (low concentration) until the smell is equally distributed throughout the room (equilibrium)?  That’s how diffusion works.

It’s very important to understand that the amount of dissolved oxygen MUST be higher in the water then inside of the animal’s body or diffusion of oxygen into the blood won’t take place.  This means the animals will either have to move or die.  This is what’s happening in the “Dead Zone” in the Gulf of Mexico.

The reason levels of oxygen are so low in the Gulf of Mexico are due in part to human actions.  The overuse of fertilizers that are high in nitrates and phosphates are one of the major problems.  When it rains or floods, these extra nutrients wash off of our lawns and into storm drains which then drain into the rivers.  Most of the Mississippi watershed consists of agricultural land in the breadbasket of the Midwest where a lot of fertilization takes place during the spring and summer months. All of the nutrients from the rivers in the Mississippi watershed eventually empty out into the Gulf of Mexico.

Mississippi Watershed: The area of land that drains into the Mississippi River and out into the Gulf of Mexico.

These nutrients help the aquatic plants grow, just as they helped our lawns and crops grow.  Now you may be thinking “In the last blog you talked about how important aquatic plants are when it comes to oxygen production.”  Indeed they do make oxygen, but as all of these plants die and sink to the bottom of the sea, bacteria feed on (decompose) their remains and use up the available oxygen in the process.  More oxygen is consumed by these aerobic bacteria than was made by the plants which is why oxygen levels can get so low.

Hypoxia is the term used when dissolved oxygen is below 2 mg/l or 2 parts per million.  That means for every one million molecules, only two of them are oxygen molecules.  Most marine life try to avoid water that’s this low in oxygen because they will become stressed or die.  The hypoxic zone in the Gulf occurs in one of the most important commercial fishery zones in the United States during the spring and summer months.  Why during the spring and summer?  There are a couple of answers to this question.  One is because of the fertilizer runoff which I mentioned earlier.  The other has to do with water temperature.

As water temperature increases, it naturally looses it's ability to hold gas molecules like oxygen. Cooler water naturally holds more oxygen. Source: Koi Club of San Diego

This is a map of the data we have been collecting during the Groundfish Survey. Our data gets sent in everyday and the maps are updated weekly. Check back at http://www.ncddc.noaa.gov/hypoxia/products/ for a complete map of Bottom Dissolved Oxygen after July 17th 2011.

When the data collection is complete you will notice that the “dead zone” is larger than the state of New Jersey.  It is bigger this year than in previous years due to the flooding that’s occurred in the Great Plains and Midwest this spring and summer.

Salinity (salt level):  This measurement is extremely important to the fish that live in the ocean because each species has an optimal salinity level that it requires.  Remember osmosis?  Osmosis is how cells move water in or out depending upon their environment.  If a fish ends up in an environment that’s too saline (salty), the water will begin to leave the cells of the fish through osmosis and they could “dehydrate”.  If they are in water that’s too fresh, then their cells will start to fill with water and they could “bloat”.  All of this cellular work is done by the body in order to maintain homeostasis.  Homeostasis refers to the ability of a living thing to keep its body in balance with the ever-changing environment in which it lives.

Salinity also affects the levels of dissolved oxygen in the water.  The saltier the water, the lower the oxygen levels will be.  It also creates a problem with waters ability to “mix”.

Notice how the heavier salt water settles to the bottom of the sea. The red dots represent the amount of dissolved oxygen during a hypoxia event. Notice that due to a lack of water mixing, the concentration of oxygen is much lower in the saltier bottom layer of water.

Chlorophyll Concentrations:  As the last blog mentioned, chlorophyll is a green pigment that phytoplankton and other aquatic plants have.  By calculating the concentration of chlorophyll in an a region, researchers can determine how productive the area may be for fishing.  Remember that zooplankton eat phytoplankton and bigger fish eat zooplankton, which are then eaten by bigger fish. A good general rule of thumb is that if the water is clear and blue then there won’t be as much living in it as green cloudy (turbid) water. Areas of hypoxia can also be predicted if the levels of chlorophyll get too high.

Now that you know some of the basics about ocean health, try to do your part.

*   If you must use fertilizer, do so sparingly.

*  Purchase soaps and detergents that are labeled phosphate free.

*  Be sure to make sustainable choices when purchasing seafood (visit Seafood Watch)

Personal Log

Today I found out why fishermen do not like dolphins.  A pod of dolphins were following us on a trawl and when we brought up the catch there were holes in the net.  We had to dump the sample back into the sea and try again after the holes were patched.  We went back to do a second trawl in the same area and the dolphins did the same thing.  We decided to try to “outrun” the dolphins on our way to the next station.

The reason we can’t collect data on the trawls with net holes is because we won’t get an accurate representation of the actual number of species living in that area.  In science it’s very important to make sure we collect good data.

A pod of dolphins following our ship.