Mark Van Arsdale: What Makes Up an Ecosystem? Part IV – Jellies, September 16, 2018

NOAA Teacher at Sea

Mark Van Arsdale

Aboard R/V Tiglax

September 11 – 26, 2018


Mission: Long Term Ecological Monitoring

Geographic Area of Cruise: North Gulf of Alaska

Date: September 16, 2018

Weather Data from the Bridge

Mostly cloudy, winds variable 10 knots, waves four to six feet during the day, up to eight feet at night

57.27 N, 150.10 W (Kodiak Line)

Science Log

What Makes Up an Ecosystem? Part IV Jellies

Ever seen a jellyfish washed up on the beach? Ever gotten stung by one?  Most people don’t have very favorable views of jellyfish.  I’m getting to spend a lot of time with them lately, and I am developing an appreciation. We have a graduate student on board studying the interactions between fish and jellies.  Her enthusiasm for them is infectious.

Graduate student Heidi photographing a phacellophora (fried egg) jelly
Graduate student Heidi photographing a phacellophora (fried egg) jelly

Jellyfish really aren’t fish.  They belong to a group called Cnidarians, along with corals, sea anemones, and hydras.   It’s one of the most primitive groups of animals on the planet.  Ancient and simple, Cnidarians have two tissue layers, a defined top and bottom, but no left and right symmetry and no defined digestive or circulatory systems.  Jellies have simple nerves and muscles.  They can move, but they are unable to swim against oceanic currents and therefore travel at the whim of those currents.  Jelly tissue is made of a collagen protein matrix and a lot of water.  I have heard one scientist call jellies “organized sea water.”  That’s really not too far off.  Seawater has a density close to one kilogram per liter, and when you measure jellies, their mass to volume ratio almost always approaches one.

Despite their simplicity, jellies are incredible predators.  When we scoop them up with the Methot net, they often come in with small lantern fish paralyzed and dangling from their tentacles.  Jellies possess one of the more sophisticated weapons in the animal kingdom. Located in their tentacles are stinging cells, called cnidocytes. These cells contain tiny, often toxic harpoons, called nematocysts. The nematocysts are triggered by touch and can deploy as fast as a rifle bullet, injecting enough venom to kill small fish or to give the person weighing the jellies a nasty sting.

Me holding a Chrysaora (sea nettle) jelly.
Holding up a Chrysaora (sea nettle) jelly.

Jellies have not been thoroughly studied in the Gulf of Alaska, and the work onboard the Tiglax may take us closer to answering some basic questions of abundance and distribution.  How many jellies are there, where are they, and are their numbers increasing in response to increasing ocean temperatures?

In order to sample jellies each night, four times a night we deploy a Methot net. The Methot net is a square steel frame, two and a half meters on each side and weighing a few hundred pounds.   It is attached to a heavy mesh net, ten meters long. Even in relatively calm seas, getting it in and out of the water takes a lot of effort.  We have already deployed it in seas up to eight feet and winds blowing 20 knots, and that was pretty crazy. The net is attached by steel bridle cables to the main crane on the Tiglax.  As the crane lifts it, four of us guide it overboard and into the water.  We leave it in the water for 20 minutes, and it catches jellies – sometimes lots of jellies.  On still nights, you can sometimes see jellies glow electric blue as they hit the net.

As we retrieve the net there are a few very tense moments where we have to simultaneously secure the swinging net frame and lift the jelly-filled cod end over the side of the boat. A few of the hauls were big enough that we had to use the crane a second time to lift the cod end into the boat.

Smaller ctenophores (comb jellies) caught in the Methot net.
Smaller ctenophores (comb jellies) caught in the Methot net.

Once on board, the jellies have to be identified, measured, and weighed.  Assuming catches stay about the same, we will measure over one thousand jellies while on this cruise.  I don’t know how all of this data compares with similar long-term ecological projects, but on this trip the trend is clear.  Jellies are true oceanic organisms, the further we go offshore the larger and more numerous they get.  Go much beyond the continental shelf and you have entered the “jelly zone.”

Personal Log

Seasick teacher

Last night was tough.  During our transit from the Seward line to the Kodiak line, things got sloppy.  The waves got bigger, and their periods got shorter.  To make things more uncomfortable, we were running perpendicular to the movement of the waves.  I retreated to my bunk to read, but eventually the motion of the ocean got the better of me and I made my required donations to the fishes.  The boat doesn’t stop for seasick scientist (or teacher) and neither does the work; at 11:00 last night I dragged myself from bed and reported for duty.

The work on the Tiglax is nonstop.  The intensity of labor involved with scientific discovery has been an eye-opener to me.  We live in a world where unimaginable knowledge is at our fingertips. We can search up the answer to any question and get immediate answers.  Yet we too easily forget that the knowledge we obtain through our Google searches was first obtained through the time and labor of seekers like the scientists aboard the Tiglax.

The goal of this project is to understand the dynamics of the Gulf of Alaska ecosystem, but one of the major challenges in oceanography is the vastness of its subject.  This project contains 60-70 sampling stations and 1,800 nautical miles of observational transects, but that is just a few pin pricks in a great wide sea. Imagine trying to understand the plot of a silent movie while watching it through a darkened curtain that has just a few specks of light passing through.


Transect lines for the North Gulf of Alaska Long-term Ecological Research Program.
“Pinpricks in the ocean,” Transect lines for the North Gulf of Alaska Long-term Ecological Research Program.

Did You Know?

Storm petrels periodically land on ships to seek cover from winds or storms.  They are one of the smaller sea birds, at just a few ounces they survive and thrive in the wild wind and waves of the Gulf of Alaska.

Last night we had a forked-tailed storm petrel fly into the drying room as I was removing my rain gear between zooplankton tows.  A softball-sized orb of grey and white feathers, it weighed almost nothing and stared at me with deep black and nervous eyes as I picked it up, wished it well, and released it off the stern of the boat.  It was a cool moment.

Animals Seen Today

  • Fin whales
  • Lots of seabirds including Storm Petrels, tufted puffins, Laysan and black-footed and short-tailed albatross, flesh footed shearwater, and an osprey that followed the boat for half the night
  • Mola mola (ocean sunfish), which was far north of its normal range







Richard Chewning, June 8, 2010

NOAA Teacher at Sea
Richard Chewning
Onboard NOAA Ship Oscar Dyson
June 4 – 24, 2010

NOAA Ship Oscar Dyson
Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska (Kodiak) to eastern Bering Sea (Dutch Harbor)
Date: June 7 – 8, 2010

Weather Data from the Bridge

Position: Just southwest of the Semidi Islands, Alaska
Time: 1400 hrs
Latitude: N 55 54.331
Longitude: W 156 54.606
Cloud Cover: mostly cloudy
Wind: 9.2 knots from E
Temperature: 7.2 C
Barometric Pressure: 1019.6 mbar

Science and Technology Log

Calming seas greeted our arrival at Snake Head Bank around 1800 hours on Sunday. Snake Head Bank is an area of the Gulf of Alaska that has been designated as untrawlable habitat. Trawling is a fishing technique where a net is towed behind one or more boats. The Dyson will be using this technique later in our cruise to catch pollock. Fishermen trawl on the bottom or somewhere in the water column depending on what fish is being targeted. Previous NOAA surveys using both acoustic and ROV (remotely operated vehicle) data have indicated that the ocean bottom in this area contains terrain such as large rocks that could snag a trawl net skimming along the bottom.

Snake Head Bank
Snake Head Bank

Our mission was to further study select areas of Snakehead Bank to better understand the seafloor where acoustic research had been conducted but the bottom composition had not been verified. NOAA scientists call this ground-truthing. To accomplish this task, the Dyson deployed a self-contained camera to the seafloor to collect video footage. This operation requires both a specially designed rig to film on the ocean floor and the coordinated efforts from crew members from various departments throughout the ship.

Success! Video footage from the bottom of the Gulf of Alaska

You might be surprised to learn that an over-the-shelf handheld camcorder and lens were used to record the footage of Snake Head Bank. Both the camera and lens are mounted to and protected by a heavy metal frame. Similar to a roll cage of a car, this cage protects the video camera from the weights used to send the rig to the bottom and from any hazards on the seafloor such as large rocks. Since we are sampling areas beyond the depth sunlight penetrates, a light must also be included to reveal the bottom. This means our camera operations can be conducted both during the day and night! The camera and the battery for the light are protected in a waterproof case that can easily be opened to change tapes and batteries.

Deployments are conducted day and night
Deployments are conducted day and night

In addition to darkness and unknown obstacles, filming at depth is also complicated by water pressure. Water pressure refers to the weight of the water pressing down (think about the pressure in your ears build as you dive to the bottom of a swimming pool). A tight seal must be maintained as water will force its way through the smallest opening. Water pressure can be enlisted to serve a useful purpose. Water pressure activates a switch once the rig reaches a certain depth turning the camera and light on and off. This conserves the batteries and ensures only the video at the bottom is recorded.

Richard waiting on the hero deck for camera recovery

The entire rig is deployed using one of the Dyson’s powerful winches using a long wire cable. The wire cable is threaded through a block attached to a metal support structure called the A-frame that can be extended over the side of the ship. The entire rig was constructed to be neutrally buoyant so the rig would hover just off the bottom. Plastic floats tied on top and metal chains hanging down from the rig ensured the camera was angled correctly towards bottom.

In order for a successful deployment, crew members from throughout the ship must work together. Just like any successful workplace or athletic team, these deployments require coordinated efforts, communication, and clearly defined job responsibilities.

The Officer of the Deck and Navigation officer positions the ship at each station and must keep the ship as stationary as possible when the camera is deployed so the camera is not dragged along the bottom. A member of the deck crew operates the winch and raises and lowers the A-frame. Another member of the deck crew assists a survey technician casting and retrieving the camera rig over the side. Two scientists change out the tapes and batteries, transfer and log the video, and adapt the rig as necessary.

Deployments require teamwork and coordination
Recovering remote camera rig at Snakehead

Finally, the unsung hero of this camera deployments was the science team’s IT (Information and Technology) Specialist. The IT specialist on th  is cruise is Rick Towler. If you like to solve problems and develop a wide range of skills, then this is the job for you. Rick saved the day on more than one occasion during the camera operations. Using some creative engineering, Rick overcame some technical difficulties with the pressure switch and wiring on the control circuit board for the camera and light. Rick is an indispensible member of the science team and is responsible for maintaining the equipment brought onboard by the scientists. When you are miles from the nearest hardware store or electronics shop, you have to be able to make do with what you have and be able to think outside the box. I think of Rick as the science team’s MacGyver! By the end of the survey’s 42 stations, the crew of the Dyson was a well-oiled machine and had overcome every challenge.

Rick, the Dyson’s MacGyver, is on the job!

Personal Log

The weather continues to improve by the hour. I am starting to find my rhythm after recovering from my drowsiness resulting from the combined effects of jet lag and the seasickness medication from the beginning of the cruise. I was surprised and pleased to learn that the Dyson has a large roll stabilization tank located just in front of and below the bridge. Tall buildings built near earthquake prone areas also use large containers of water to counter the swaying motion that damages buildings during earthquakes.

Meals aboard the Dyson are a key part of any ship routine. Meals are served for one hour starting at 0700, 1100, and 1200 hours. Meals are an interesting time to visit with people. Some crew members at meals are tired as they are just coming off watch, others are wide awake and in a hurry as they are grabbing a quick bite between deployments or projects, and others are still trying to wake up as they have just left their rack even though the meal might be dinner! Dinner Monwas very satisfying: roast beef and game hen with broccoli, steamed rice, and noodles.

Dinner is served

You might also see someone headed for their morning workout. I discovered that the little physical exercise. I haven’t tried the treadmill yet as I hear running can be a littletricky on the rolling seas!

After completing our deployments around 0545, we turned southwest for Unimak Pass. We are leaving the Gulf of Alaska behind and now heading for the Bering Sea. I am looking forward to seeing the Aleutian Islands up close as we will be sailing among the islands rather than the open sea. This will give us the benefit of smoother sailing and the added bonus of beautiful scenery along the way!

Headed to the Bering Sea!

Animals Observed from Snake Head Bank Seafloor
Rock Fish
Brittle stars
Skate (similar to a sting ray minus the barb)
Euphausiids (commonly called krill)