IB exam 2018 and a plankton swarm

Second year Marine Science students wrote the second of two papers this morning to complete their IB exam. It has been a wonderful two years – thank you!

At the same time the students were writing their exam, there was a swarm of plankton around the Pearson College dock:

I think that the zooplankton were here to wish the students well!

Many Dungeness crab megalopae have been hanging out around the dock for the past few days (helping the students revise?!).

To the Year 43 Marine Science students: I wish you all the best as you drift on out of Pedder Bay and I hope that the winds and currents are favourable so that you can drift back again some time!

Plankton light traps

At 5:45 pm on 2 November, 8 light traps designed to capture plankton were suspended off the Pearson College dock.

Marine Science students retrieved the traps the next day and examined the plankton that were captured.

We saw some very cool critters including many copepods with egg masses:

And a polychaete worm and a crab megalopa larva:

More megalopae and nifty nereids

After a question from Johan about ‘weird, somewhat disgusting, sea snake/fish slithering around the surface’ at night and from Max (Dock worker extraordinaire!) about ‘long skinny creatures’ ranging in size from 6″ to 1′, I thought I better go investigate…

Max also sent the photo above and the two below:

These creatures are what I learned as Nereis brandti but are now called Alitta brandti.  Learn more about these giant pileworms from:

Alitta brandti at Encyclopedia of Life

Nereis (Neanthes) brandti at Invertebrates of the Salish Sea

Alitta brandti at World Polychaete Database

On Sunday 2 June we hung a light off the Pearson College dock which attracted many, many megalopae (Dungeness crab, Metacarcinus magister).  Periodically a worm would also be attracted to the light.

I did pester a few of the worms and they released big clouds of sperm.  The reproductive strategy is called epitoky where the posterior end of the polychaete worm is transformed into a bag of gametes (either sperm or eggs). The epitokes swarm at the surface and then explode to release the gametes. Crazy but cool!

The megalopae are here!

While the students deserted us on 24 May, the Pearson College dock has thousands (maybe hundreds of thousands?) of visitors right now. The final larval stage of the Dungeness crab (Metacarcinus magister) is called a megalopa and there a many, many megalopae swarming around the dock.

On the dock, there are also thousands of juvenile crabs scrambling around.  The megalopae molt and metamorphose into the benthic juvenile stage seen below.

There are also many megalopae and juveniles on the succession substrates that students put in the water in September 2012.

 And Ivan thought nothing was using his wire!