1. SeaWiFS image
July 9th, 2003

2. May 1967

3. Phytoplankton of Puget Sound (most photos by Jan Rines)
Diatoms:
Chaetoceros debilis
Skeletonema costatum
Thalassiosira
aestivalis
Chaetoceros convolutus

4. Phytoplankton of Puget Sound Diatoms:
Ditylum brightwellii
Actinoptychus senarius
Rhizosolenia pungens
Pseudo-nitzschia fraudulenta

5. Phytoplankton of Puget Sound
Dinoflagellates:
Protoperidinium
divergens
Ceratium fusus
Noctiluca miliaris
Alexandrium catenella
Gyrodinium britannicum

6. Phytoplankton of Puget Sound
Silicoflagellates:
Internal siliceous skeleton.
Small size: 5-20 microns
Distephanus speculum

7. Phytoplankton of Puget Sound Other flagellates:
Dictyocha Heterosigma akashiwo
Heterosigma – toxic to fish, but mechanism unknown, Phaeocystis – non-toxic, but produces mucus that can clog nets and fish gills, Dictyocha - common
Phaeocystis

8. Cyanobacteria major forms
Synechococcus (1-3mm)
Prochlorococcus (~0.5 mm)
Trichodesmium (1-3mm)
In Hood Canal: >70% of cells and ~20% spring biomass is Synechococcus

9. Phytoplankton distributions
Thin layers – marine snow
Alldredge et al. 1996

10. Thin layers Alldredge et al. 1996
Odontella longicuris – diatom makes up most of the aggregates in the thin layer
Alldredge et al. 1996

11. Species associations within thin layers:
Pseudo-nitschia fraudulenta and Chaetoceros socialis
Chaetoceros provides substrate in the water column within which pseudo-nitschia can move. P-N bloom might go undetected by hiding within Chaetoseros in a thin layer
Rines et al. 2002

12. Is grazing important in Puget Sound?
Importance of microzooplankton grazers
Numerous
Rapid reproduction (can keep up with phytoplankton)
Method of studying grazing effects
Dilution technique
Collect water samples to create a dilution series
Herbivore dilution allows phytoplankton growth

13. Dilution experiments Growth equation: dp/dt = mp – czp
dp/dt = mp – czDp = mp – gDp
Solution: 1/t ln(p(t)/p0) = m – gD
Y-intercept= “infinite dilution”
GROWTH RATE
Slope = linear relationship with dilutions
HERBIVORY RATE
Net Growth Rate (per time)
Decreasing # of Grazers
Dilution factor (fraction SW) 1

14. Phytoplankton growth and grazing at a station in the San Juan Islands
Grazing (g)
Strom et al. 2001
Grazing rates high during blooms (periods with high growth rates)

15. Small phytoplankton grazed at higher rates than large phytoplankton
Strom et al. 2001
Could grazing contribute to diatom dominance in Puget Sound?