Anna Levy: What Tummies Tell Us, July 15, 2017


NOAA Teacher at Sea

Anna Levy

Aboard NOAA Ship Oregon II

July 10 – 20, 2017

 

Mission: Groundfish Survey

Geographic Area of Cruise: Gulf of Mexico

Date: July 15, 2017

 

Weather Data from the Bridge

Scattered, mild storms continue, causing some delays in our fishing. However, they do lead to beautiful sunsets!

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Beautiful Gulf of Mexico sunset

Latitude: 29 18.790 N

Longitude: 84 52.358 W

 

Air temp: 28.7 C

Water temp: 29.7 C

Wind direction: light and variable

Wind speed: light and variable

Wave height: 0.3 meter

Sky: 80% cloud cover, no rain

 

Science and Technology Log

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TAS Anna Levy removes the stomach of a red snapper.

Data about the number and size of individual organisms can tell us a lot about the health of an overall population of a species. However, it doesn’t tell us much about the role that species plays in its community. If we want to understand that better, we need to know more about how it fits into its food web – what it eats and what eats it. If you were trying to collect information about what a fish eats, where would you look first? Its stomach!

So, after we measure certain species, we dissect them and remove their stomachs. We place each stomach in its own tiny bag, with a bar code that identifies which individual fish it belonged to. Back at a lab on land, scientists will carefully examine the contents of the stomachs to better understand what each species was eating.

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The bar codes that we use to label specimens.

 

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This map shows the native range of lionfish. Credit: http://oceanservice.noaa.gov/facts/lionfish-facts.html

For example, one of the fish currently under investigation in the Gulf of Mexico is the lionfish. This is an invasive species, which means that it is not native to the area. Its natural habitat is in parts of southern Pacific and Indian oceans, but it was first spotted in the Atlantic, off the coast of North Carolina, in 2002. Lionfish were most likely introduced to this area by humans, when they no longer wanted the fish as an aquarium pet. By 2010, its range had expanded to include the Gulf. And, with no natural predators in this area and rapid rates of reproduction, its numbers have increased exponentially.

Early dietary studies, which were focused on the lionfish in the Atlantic, show that the lionfish is a generalist. This means that, while it prefers to eat small reef fish, it is able to eat a wide variety of organisms including benthic invertebrates (like crabs) and other fish. This flexibility makes lionfish even more resilient and able to spread. These studies also found that lionfish stomachs were rarely empty, suggesting that they are highly successful predators, able to out-compete other top predators for food.

This has wildlife experts concerned about the impact lionfish will have on natural ecosystems. It is possible that lionfish will over-consume native species, causing native ecosystems to collapse. It is also possible that lionfish will out-compete and displace native, high level predators, like snapper and grouper. Scientists are working now to develop methods to try to manage this invasion.

Because ecosystems here are different from those in the Atlantic, scientists are now turning their attention to studying the lionfish in the Gulf of Mexico. The work that we did on the boat today should help them do just that!

To see the results of one such study, completed in 2014, see:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0105852

For more information and photos about the lionfish, please see:

https://oceanservice.noaa.gov/education/stories/lionfish/lion02_invade.html

https://oceanservice.noaa.gov/facts/lionfish-facts.html

http://www.fisheries.noaa.gov/mediacenter/2015/05/21_05.html

 

Personal Log

Often times, we teachers struggle to convince our students that, while all of the modern technology we have is great, they also need to understand how to solve problems without relying on it. (Most of us have probably been on at least one side of the old, “no, you don’t need a calculator to multiply by 10!” argument at some point in life.)   Well, in the past couple of days, I’ve seen two great examples of this onboard the ship.

The first relates directly to our survey work. Our CTD, the equipment mentioned in last post, has two sensors that both detect how much dissolved oxygen is in the water. Having two instruments collecting the same information (sometimes called redundancy) is important, not only so that there is a back-up in case one breaks, but also so that we can tell if they are measuring accurately.

The two oxygen sensors have been reading differently – one was about 0.7 mg/L lower than the other. This is an indication that one needs to be calibrated – but which one? To find out, Alonzo Hamilton, one of the senior NOAA scientists, used a classical chemical analysis technique called titration.

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This is the titration equipment found in the chemical lab on board the ship.

In a chemical titration, one substance is slowly added to another, while the scientist watches for a chemical reaction to occur. If you know how the two substances react, you can determine how much of the second substance is present, based on how much of the first was added to make the reaction happen.

Based on the results of his titration, Alonzo was able to determine which of the oxygen sensors was reading accurately. So, it definitely goes to show that there are important applications for that classic high school chemistry!

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The binnacle that houses the ship’s magnetic compass.

The other example relates more to the ability to navigate the ship. NOAA Ship Oregon II is equipped with advanced electronic navigation software, Gyro compass, radar, and GPS systems. However, when I was exploring the top deck (flying bridge) of the ship, I came upon this strangely low-tech looking instrument. I asked ENS Chelsea Parrish, a NOAA Corps Officer and member of the wardroom, about it. She explained that it is called a “binnacle,” a safeguard that houses a magnetic compass! The magnetic compass is the same type of technology used by mariners back in the 1300’s. It is critical to have in case of a power outage or other disruption to the ship’s electronic navigation technology.

 

 

Did You Know?

While they typically live in cold waters, there is one pod of orca whales (aka killer whales) that resides, year-round, in the Gulf of Mexico. It’s rare to see them, but I’m keeping my eyes peeled!

Dolphins, on the other hand, seem to be everywhere out here. I’ve caught at least a glimpse of them every day so far. In fact, a group of them swam up to investigate our CTD today as it was being lowered into the water.

 

Questions to Consider:

Research: Some other famous invasive species in our oceans include the green crab (Carcinus maenas), killer algae (Caulerpa taxifolia), a jellyfish-like animal called a sea walnut (Mnemiopsis leidyi), a marine snail called rapa whelk (Rapana venosa), and the zebra mussel (Dreissena polymorpha). Where did each of these originate? How did they come to inhabit their invaded areas? What impact are they having?

Brainstorm: What measures could you imagine taking to manage some of these species?

Research: The specific type of titration used to determine the amount of dissolved oxygen in water is called the Winkler method. How does the Winkler method work?

 

 

 

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