Spring 2021 NGA-LTER

The Burt lab sent one member (Ben Lowin) on the spring Northern Gulf of Alaska (NGA) Long-Term Ecological Research (LTER) cruise. The Chief Scientist for this cruise was Russell Hopcroft (zooplankton), who was joined by Suzanne Strom (phytoplankton) and Ana Aguilar-Islas (trace metals) as the leaders of the cruise. The cruise started on April 20th and ended on the 7th of May.

R/V Sikuliaq – Seward Alaska May 20th, 2021

The cruse started out overcast and chilly, with snow on all the mountains surrounding Seward. Little did we know that we were going to be sampling right at the start of the spring bloom. The spring bloom is a biological phenomenon where, after winter there are ample nutrients in the water but phytotron growth is limited by light. As the water column stratifies phytoplankton are exposed to more light and are able to make use of the nutrients. This leads to exponential growth turning the waters of the NGA into a mosaic of color.

Chlorophyll-a satellite image for the NGA May 25th 2021 form VIIRS satellite
Lesser white faced goose swimming in the emerald, green waters of the Spring Bloom (May 25th, 2021)

Ben: From my perspective on the ship, it was amazing the color transformation that we steamed through. We went from Hawaiian blue and being able to see the CTD as it went down to emerald, green where you the CTD disappears as it enters the water.  

I was running the underway bio-optical system, this is a semi-autonomous system that takes measurements of chlorophyll, phytoplankton carbon and primary production every quarter of a second. This system is normally fairly low maintenance, with the cleaning and filter changing happening every other day to every few days. However, the spring bloom put a serious logistical problem on the table. I had budgeted to change the filter every 2-3 days, with some extra (including the ones for the next cruise).  The issue was that the 2um filter was clogging 2-3 times a day. This was leading to very low flow rates during the filter period, causing air injection and contaminating the optical signals we are measuring.  Fortunately, the whole ship is filled with very bright people and Tom Kelly suggested back washing the filters to extend their life. This worked fantastically.

After the filter problem was solved we cruised into Icy Bay, which lived up to its name.

After Icy Bay was the final push to get the Seward line sampled as a storm rolled in. We managed to do the whole line and ride out the storm, with only one particularly sleepless night. The journey back was smooth sailing and we made port in time for the crew to head out and receive their COVID vaccine shots.

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