3 August 2022 Water Sifting

Sea Surface Temperature: 41.36 F

The Spaceship onboard

In other photos you might have noticed the large object on deck that looks like a spaceship. It's actually the multicore. You can check out this video showing how we use it!

Needles in a haystack

Almost any time you swim in the ocean, plankton are swimming beside you. They might be too small to see, but they are there. To understand what drives harmful algal blooms, we need to know what species make up the plankton community in different areas. This is quite a challenge. The Bering and Chukchi Seas are huge. PhytoplanktonSmall or microscopic aquatic plants that float or drift in fresh or salt water. are microscopic and are in constant motion. Not only do they drift with the currents but they also embark on a daily vertical migration between the abundant sunlight of the sea surface and the nutrients and safety of the lower depths.

It would be nice if you could go out on deck, glance at the seawater, and say “yup, there are 160 Alexandrium cells right here.” Sadly, it doesn’t work that way, because Alexandrium are so small that that you could line up 20 Alexandrium cells side-by-side on the tip of a pencil. Luckily, there are tools out there that let us collect water from different depths and separate out the plankton.

Sifting for Alexandrium

We collect water samples with the Niskin bottles mounted on the CTDA research tool that is submerged in the water to measure conductivity (salinity), temperature, and depth. rosette. The bottles are open while the CTDA research tool that is submerged in the water to measure conductivity (salinity), temperature, and depth. descends to the seafloor (it actually stops descending 5 meters above the seafloor, so that it does not hit the bottom). As the CTDA research tool that is submerged in the water to measure conductivity (salinity), temperature, and depth. is winched back to the surface, each bottle is closed at a different depth. This lets us find out what plankton and chemicals are in the water at those depths.

There do not have to be huge amounts of Alexandrium in the water to create enough saxitoxin to cause a problem. Even seemingly small concentrations in the ocean (1000 cells per liter) can be enough to cause shellfish toxicity, which when consumed causes paralytic shellfish poisoning (PSP). This means that it is very important to know how many Alexandrium cells are in the seawater. We measure this in cells per liter by collecting 2 liters of water from several depths at each station. Then we pour this water through a filter to gather all the Alexandrium. The final step is to store the Alexandrium in a test tube so that they can be counted back at the lab with the assistance of a powerful microscope.

Flitering out Pseudo-nitzschia

There are many different species of Pseudo-nitzschia. Some produce domoic acid, which cause amnesic shellfish poisoning (ASP), and others are harmless. Knowing which species live in these waters and how toxic they are would help local communities manage the risk of HABs. Kate Hubbard, a scientist who loves to garden, is trying to figure out which species live in northern Alaska and how toxic they are. To answer these questions, she collects water from different depths and filters it. When she gets back to her lab in Florida, she will extract DNA and Domoic acid from the samples. The DNA will tell her what species of Pseudo-nitzschia are present in these waters. The Domoic acid will tell her what parts of the ocean have the toxin, and will help her to understand which species of Pseudo-nitzschia produce the toxin.