Weather Details from Bridge: (at 19:45 GMT)
Air Temperature: 29.90 ◦C
Water Temperature: 29.40 ◦C
Relative Humidity: 64%
Wind Speed: 3.56 kts
Barometric Pressure: 1,014.90 mb
Science and Technology Log
This device is the first to be deployed at every sampling station. CTD stands for *Conductivity *Temperature *Depth. The salinity (the amount of salt in the water) is measured by looking at the conductivity. Salt has ions. Ions are like little electrical charges that are either positively charged or negatively charged. By measuring how many electrical charges (ionic charges) there are in the salt, we can measure how conductive the water is which will also tell us how much salt is in the water. This data is measured by the CTD and is transmitted by an electrical pulse. The depth is measured by the amount of pressure being pressed upon the device as it is lowered into the water. The temperature is measured by a temperature gauge. All of the data collection devices are attached to a large metal rosette wheel.
The frame is lowered into the water using a thick cable that is attached to a J-Frame (a large yellow arm that can be raised and lowered.) The cable runs through a pulley attached to the J-Frame to make sure the deployment of the CTD runs smoothly.
The CTD also measures dissolved oxygen levels (the amount of oxygen in the water). There is also a fluorometer which measures the amount of chlorophyll (phytoplankton activity) in the water.
As soon as the CTD is released into the water it begins collecting data. Data is collected continuously as it is lowered toward the ocean bottom. The data is sent through a very thin wire that transmits the data to one of the computers in the dry lab where it is documented for later analysis.
The CTD has three water collection Niskin bottles (large grey cylinders). Niskins are named after Shale Niskin who developed this bottle. Water collections using the Niskins are controlled by a computer in the dry lab. One click on a computer and the CTD will automatically snap shut the bottles. Older versions that were not controlled by computers had heavy metal messengers that were lowered down a string toward the collection bottle. When the messenger reached the top of the bottle, it would hit a trigger and snap the bottle shut.
Water collection does not occur at every sampling station, but when it is planned, the water is collected at the bottom. This is because we are focusing on the bottom of the ocean during this survey. We want to test the water at this depth to better understand the environment in which the organisms we are collecting live in and make predictions as to how human and nonhuman influences may harm this benthic (bottom) community. The water can be used for several different tests, but we use it to test the dissolved oxygen levels of the water.
Measuring dissolved oxygen levels is important because if it is extremely low — called “hypoxia” (2 mg/L or lower) — animals fail to survive. If dissolved oxygen is not present (0 mg/L) it is called “anoxia”. Hypoxic or anoxic areas are frequently referred to as “dead zones”.
Although the CTD has a digital device that measures the dissolved oxygen (DO) levels, we manually test the water for DO once a day to make sure that the CTD is calibrated correctly and that there are no malfunctions that need to be fixed. There are two different ways we manually test the water. One is by using a hand-held dissolved oxygen meter. This meter digitally calculates the dissolved oxygen levels. We lower this meter directly into one of the Niskins.
We also collect water samples from each of the three Niskins in glass beakers. We use these samples to run what’s called a Winkler’s tritration test. This is a chemical-based test that tells us how much dissolved oxygen is in the water.It is important to run so many different tests because if we only used one method, we couldn’t know if it was accurate or not. By running three different tests, we can compare the results from all three. If the result from one test comes up differently than the others, we know that test was not accurate but the other two tests were.
After the CTD is brought back up on deck, it is important to rinse it off with fresh water. This is because the salt from the ocean can damage the equipment and corrode (eat away at) the metal. Once a day we also run Triton-X (a type of soap) through the hoses of the CTD to keep the sensors clean and salt-free.
Day 5 – July 9th
Today was a bit slower because our sampling sites were father apart than they were on previous days. We continued collecting and preserving plankton, but trawling is the most exciting because you get to see so many different species. We conducted only one trawl today and it was a very small catch. It didn’t take long to collect all of the data we needed before we were back to waiting for our next plankton collection site. We had some interesting fish in our trawl including a small bat fish, a couple of starfish, several sea urchins, and a honeycomb moray eel. The highlight of my shift was during our last plankton trawling. It was around 21:00 (or 9:00 pm) so it was pitch black out with the only light coming from the ship and the stars. We started seeing a lot of flying fish jumping out of the water. We soon realized it was because a pod of spotted dolphin had found them. It was fun watching them jump and fly though the water to catch the fish. The group also had a couple young dolphins that stuck close to their mothers. I’d seen dolphins before, mostly in captivity or ones too far away from a boat to see clearly, so it was really neat to see them so close up!
Day 6 – July 10th
Today started out great. I woke up to get ready for my shift by heading down to the mess for lunch. It was one of my favorite meals – Mexican! When I read about other teacher’s experiences on NOAA ships and how great the food was I now understand what they were talking about! There is so much yummy food at all of the meals that it is frequently hard to decide what NOT to eat! And there is so much food available at each meal that you’ll never go hungry! I always end up walking away stuffed!
The weather was great up until the sun set. We were stuck in quite the thunderstorm. When there are storms with lightning in the area, no one is allowed out on deck for safety reasons.
We had to postpone a couple of our sampling stations until the storm passed over us, so we tried our best to keep ourselves occupied until the storm passed. Our internet went down for length of time, so we were left with books, movies, or just some relaxation time.
By the time the storm had passed, we had only one sampling station to complete before it was time for the next watch team to switch in.
Day 7 – July 11th
The first thing I noticed today was the panoramic view of large cumulus and cumulonimbus clouds – those are the clouds that produce thunderstorms. We managed to steer clear of them, but they certainly made some pretty skies.
We had a couple trawling stations which was great because it is always fun to discover and examine more species. While the trawls were small, we had some cool finds including a frogfish, a butterfly fish, and a black-nose shark.
A highlight from today was the full rainbow that graced our skies after dinner. I can’t recall ever seeing a full rainbow before so it was really cool to see one!
Did You Know?
Our CTD weighs about 200 pounds. On its current settings it can be deployed to a depth of up to 5,000 meters, but if we adjusted the settings it could go as far down as 10,000 meters! With all of the attachments and the steel cage, our CTD costs roughly around $100,000 to purchase. That’s why we have to handle it with care!