We observed so much in the short space of a week -- darting copepods and copepod-like forms, gently floating jellies, neatly geometric phytoplankton and enigmatic fish and invertebrate eggs.  At first the diversity overwhelmed us.  Then we began to see the same forms time and again, and to recognize the movements of certain creatures.  We tried to capture these forms and movements.  Our pictures pale a bit in comparison to those taken by seasoned professionals, but through the process of trying to cast the best light on our subjects and to understand how plankton make their livings, we learned a great deal about what is involved in studying animals in the plankton.

Much can be learned through careful sorting and observation of planktonic organisms, provided one has a couple of key field guides, a simple microscope, and patience to keep looking.  As we sampled the plankton with different nets and at different times of day, we gained hints of the multitude of environmental factors that shape the distribution and abundances of planktonic organisms.  We caught copepods in great numbers during the day, while we lured more crab zoea than we ever wanted during the night-lit vertical tow from the FHL docks.  Jellies seemed more abundant in areas where slicks occurred--places where currents concentrate larvae and other organic material at the water's surface.  Ctenophores were not abundant, but seemed more often caught during the day.  We did not find any echinoderm larvae in our samples, but are uncertain whether that was due to their relative rarity or their small size.

To document trends in diversity and abundance in response to environmental cues, we would want to sample over a greater time period and in replicated areas.  We would need to quantify the amount of water sampled during each tow, and to consider known influential factors, such as time of day or tidal stage, in our sampling design and analysis.  Now that we have gained some skills identifying planktonic organisms and operating the equipment needed to sample them, it would be interesting to pursue specific questions, such as:

• How does the plankton species assemblage in the vicinity of Friday Harbor vary with the tidal cycle?
• Do the assemblages sampled at various depths differ?
• Do the types or abundances of organisms found in areas with and without slicks differ?
• What mechanisms, such as passive transport within tidal bores, predation avoidance, or vertical migration, or some combination of factors, account for the observed patterns?
• How do plankton assemblages in this area change seasonally and annually?

These questions could quickly escape the realm of reasonable projects, but with some practice identifying plankton and fair knowledge of local currents and seasonal cycles, both of which can be gained through practice and conversation at FHL, some very interesting short studies could be done.
 

Acknowledgments

We would like to thank our instructors - Mike Hart, Bob Podolsky, Marney Pratt, and Russell Wyeth - for their enthusiastic and helpful input.  Additional thanks to Margaret for contributing much-needed photos, to Tom for his Clione video and information, to Darren for marine support, and to the FHL staff for logistical support.  Our classmates good-naturedly shared computers, meals and the invertebrate course experience, and for that we thank them.