Venus-dinos and blaming your equipment (9/3/09)

 

Anyway, As we steamed south this morning on our way to begin mapping (and sampling the depths of) the Columbia River plume, the water turned a murky reddish-brown, convincing more than one of us that we had, in fact, entered the plume. However, our circulation models were predicting that we were nowhere near plume waters, and the ships salinometer, whose virtues had just recently been described as "questionable", was reporting salinities far in excess of what we would expect had we been plowing through the plume. Of course, our first thought was "our gear is busted" (it's sooo hard not to do this, really!) Chief Scientist Tawnya Peterson had also noticed a large increase in fluorescence associated with the murky water (fluorescence increases with the concentration of chlorophyll, so we use it to gauge how many phytoplankton are floating about), so she asked Natalja Kuvaldina to grab a surface sample and throw it through the FlowCAM (now that it works. Thanks leatherman!) to see who was in the water.

 

Imagine our surprise to discover that the murky brown color wasn't fine river sediments, but actually a dense bloom of the dinoflagellate Akashiwo sanguinea -- we weren't in the plume at all!

A close up of some of the critters shown above. Akashiwo are the big guys that look like bloomers (I think they look like  the Venus of Willendorf, myself...plus I like the whole Venus-sea association...yes, I'm a dork)

We aren't sure what caused the bloom, but a few hypotheses were discussed. Perhaps the recent switch in winds to downwelling conditions have blown a moderate but widespread concentration of Akishiwo towards the edge of the Columbia River plume, where they have stacked up to form a dense aggregation? Perhaps the recent upwelling conditions drove a bloom of diatoms and now that it's over the changed water chemistry is facilitating a dino-bloom? Or we might just be seeing the results of a higher than usual level of stratification, or some impact of the reduced levels of oxygen at ~20m we observed on the Columbia River Hydroline. All very interesting possibilities! The nice thing about science as a technique for generating knowledge is that it's actually a bit better at generating more questions! One thing's for sure, that old maxim "trust your compass" has value beyond orienteering. I learned my lesson.