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 23, 2018
Weather Data from the Bridge
Variable winds, partially cloudy, calm seas
60.20 N, 147.57 W (Prince William Sound)
Waking Up Copepods
One of the scientists on board is interested in the life cycles of a particular species of Neocalanus copepod. Neocalanus is a remarkable looking copepod. They have long antennae with feathered forks at the ends. They have striking red-orange stripes on their bodies and antennae that reminds you a bit of a candy cane. Neocalanus is an important copepod in the Gulf of Alaska ecosystem, and it typically makes up the largest portion of zooplankton biomass in the spring.
Its life cycle is interesting. If zooplankton were cars, the Neocalanus might be a Toyota Prius. It’s not fast or fancy, but it’s efficient. Neocalanus copepods feast in the spring and early summer and then settle down several hundred meters below the surface to enter into a diapause state. Diapause is a kind of dormancy that involves slowing basic metabolic functions to near zero. It is a strategy used by other Alaskan arthropods, most notably mosquitos, to survive long winters. As for why they travel deep into the water column, the answer seems to be that they use less energy in the dark, cold, high pressure waters at depth. Inside the Neocalanus there is an unmistakable large, sausage shaped sack of oil that should provide the energy reserves needed to survive prolonged diapause.
When the Neocalanus females wake up, they have to restart their metabolism and begin meiotic development of their oocytes (egg cells.) They have previously mated and they store the male’s sperm within their bodies during diapause. Each of these biological events involves turning on several dozen genes. What our scientist wants to know is what genes get turned on, in what order, and what environmental clues tell the initial genes to start making RNA. To study all of this, she needs living copepods in diapause. Our collection process inevitably wakes them up, but it gives her a time zero for observing this transformation. For the next twelve hours, she separated and preserved copepods every hour for later genetic analysis that may give her insight into when genes turn on and in what order as the copepods wake up.
In order to get her copepods, the night team did a vertical Multi-net tow at four AM. We dropped the Multi-net down to a depth of 740 meters. The work we were doing was sensitive, as she needed the copepods alive and undamaged. I was glad to have slept a few hours as we were moving between sampling stations, because what came up in the tow was pretty amazing. Along with the Neocalanus, there were many other types of zooplankton including the copepod Metridia. Metridia produce an intense bioluminescence when disturbed. When we brought the nets to the surface, the cod ends were glowing electric blue and individual copepods could be seen producing pinpricks of light that were remarkably bright.
Bioluminescence is ubiquitous amongst deep sea species. Deep sea fishes, jellies, and plankton use it to attract prey, to camouflage their silhouette, to surprise and distract predators, and likely to communicate with members of the opposite sex. The deep oceans make up 95% of biological habitat on Earth. If you consider bioluminescence communication a kind of language, it may be the most commonly spoken language on the planet.
Luciferin production and luciferase transcription in the bioluminescent copepod Metridia lucens. Michael Tessler et al (2018)
Waking up in Prince William Sound today felt good. I was closer to home this morning than at any time since leaving Seward. The Sound feels comfortable and protected. Should bad weather come up, and it sounds like it will tomorrow, there are hundreds of sheltered bays to hide in.
Prince William Sound’s beauties are hard to describe without sounding cliché. Most striking of all are the large tidewater glaciers. In the evening, we made our way to Chenga Glacier, to do CTD cast. It was a quite a sight, as were the three hundred harbor seals hauled out on the floating ice in front of the glacier.
These glaciers directly shape the ecosystem of the Sound. They provide a large freshwater input that is high in trace minerals, while creating pockets of cold water, which serve as micro-climates within the larger area. These glaciers are melting at incredible rates, and freshwater inputs are greater than they have been at any time since the last ice age. Sampling stations that were once near the face of the Chenga and Columbia Glaciers are now miles away from their quickly receding faces. Click here to watch the satellite images of Columbia’s retreat. This ecosystem is changing, and only through long term ecological monitoring will we know exactly how or what it means.
The completion of the road to the town of Whittier has also changed the Sound. It’s late September, and most pleasure boaters have stowed their boats for the winter, but the number of boats and people coming into the sound to fish, hunt, and sight see has increased dramatically. Many Alaskans have come to recognize the coastal gem that lays just seventy miles and one long tunnel through the mountain from Anchorage.
Animals seen today
- Lots of harbor seals near Chenega Glacier
- Sea otters
- Fewer birds today, mergansers, Kittlitz’s murlets, mew gulls, goldeneyes,