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 14, 2018
Weather Data from the Bridge
Mostly cloudy, winds variable 10 knots, waves to four feet
58.27 N, 148.07 W (Gulf of Alaska Line)
What Makes Up an Ecosystem? Part II Phytoplankton
Most of my students know that the sun provides the foundational energy for almost all of Earth’s food webs. Yet many students will get stumped when I ask them, where does the mass of a tree comes from? The answer of course is carbon dioxide from the air, but I bet you already knew that.
Scientists use the term “primary productivity” to explain how trees, plants, and algae take in carbon dioxide and “fix it” into carbohydrates during the process of photosynthesis. Out here in the Gulf of Alaska, the primary producers are phytoplankton (primarily diatoms and dinoflagellates). When examining diatoms under a microscope, they look like tiny golden pillboxes, or perhaps Oreos if you are feeling hungry.
One of the teams of scientists on board is trying to measure the rates of primary productivity using captive phytoplankton and a homemade incubation chamber. They collect phytoplankton samples, store them in sealed containers, and then place them into the incubator. Within their sample jars, they inject a C13 isotope. After the experiment has run its course, they will use vacuum filtration to separate the phytoplankton cells from the seawater. Once the phytoplankton cells are captured on filter paper they can measure the ratios of C12 to C13. Almost all of the carbon available in the environment is C12 and can be distinguished from C13. The ratios of C12 to C13 in the cells gives them a measurement of how much dissolved carbon is being “fixed” into sugars by phytoplankton. Apparently using C14 would actually work better but C14 is radioactive and the Tiglax is not equipped with the facilities to hand using a radioactive substance.
During the September survey, phytoplankton numbers are much lower than they are in the spring. The nutrients that they need to grow have largely been used up. Winter storms will mix the water and bring large amounts of nutrients back to the surface. When sunlight returns in April, all of the conditions necessary for phytoplankton growth will be present, and the North Gulf of Alaska will experience a phytoplankton bloom. It’s these phytoplankton blooms that create the foundation for the entire Gulf of Alaska ecosystem.
Interesting things to see
The night shift is not getting any easier. The cumulative effects of too little sleep are starting to catch up to me, and last night I found myself dosing off between plankton tows. The tows were more interesting though. Once we got past the edge of the continental shelf, the diversity of zooplankton species increased and we started to see lantern fish in each of the tows. Lantern fish spend their days below one thousand feet in the darkness of the mesopelagic and then migrate up each night to feed on zooplankton. The have a line of photophores (light producing cells) on their ventral sides. When they light them up, their bodies blend in to the faint light above, hiding their silhouette, making them functionally invisible.
Once I am up in the morning, the most fun place to hang out on the Tiglax is the flying bridge. Almost fifty feet up and sitting on top of the wheelhouse, it has a cushioned bench, a wind block, and a killer view. This is where our bird and marine mammal observers work. Normally there is one U.S. Fish and Wildlife observer who works while the boat is transiting from one station to the next. On this trip, there is a second observer in training. The observers’ job is to use a very specific protocol to count and identify any sea bird or marine mammal seen along the transect lines.
Today we saw lots of albatross; mostly black-footed, but a few Laysan, and one short-tailed albatross that landed next to the boat while were casting the CTD. The short-tailed albatross was nearly extinct a few years ago, and today is still considered endangered. That bird was one of only 4000 of its species remaining. Albatross have an unfortunate tendency to follow long-line fishing boats. They try to grab the bait off of hooks and often are drowned as the hooks drag them to the bottom. Albatross are a wonder to watch as they glide effortlessly a few inches above the waves. They have narrow tapered wings that are comically long. When they land on the water, they fold their gangly wings back in a way that reminds me of a kid whose growth spurts hit long before their body knows what to do with all of that height. While flying, however, they are a picture of grace and efficiency. They glide effortlessly just a few inches above the water, scanning for an unsuspecting fish or squid. When some species of albatross fledge from their nesting grounds, they may not set foot on land again for seven years, when their own reproductive instincts drive them to land to look for a mate.
Our birders seem to appreciate anyone who shares their enthusiasm for birds and are very patient with all of my “What species is that?” questions. They have been seeing whales as well. Fin and sperm whales are common in this part of the gulf and they have seen both.
Did You Know?
Albatross, along with many other sea birds, have life spans comparable to humans. It’s not uncommon for them to live sixty or seventy years, and they don’t reach reproductive maturity until well into their teens.
Animals Seen Today
- Fin and sperm whales
- Storm Petrels, tufted puffins, Laysan and black-footed and short-tailed albatross, flesh footed shearwater