On April 20 and 21, 2006 The University of Washington – Tacoma estuaries class sampled at old town dock and then utilized the City of Tacoma’s jet sled Captained by Rick Fuller to sample in Commencement Bay.  We separated into two groups and collected data from seven stations in the southern portion of commencement bay.  At old Town Dock on the waterfront in Commencement bay night sampling was done on April 20, 2006 to compare results during the following day.   A horizontal tow of 100 meters was done with a twenty-micron mesh and a vertical tow of fifteen meters was also done with 153-micron mesh.  A Niskin bottle was used at the surface for water collection to be used for chlorophyll, nutrients and dissolved oxygen.   

The following day there were seven sites where we sampled in Commencement bay.  At each station the later mentioned tools and techniques were used to gather the data.  A CTD was lowered into the water with the use of a gas powered wench and depth reader and it measured conductivity, temperature, density, oxygen concentration, transmission and fluorescence on its way down through the water continuously and relayed the information to a computer onboard the vessel.  A Niskin bottle was positioned one meter above the CTD on the same line to collect chlorophyll, nutrients and dissolved oxygen.   At each station a secchi disc was lowered and recorded for visibility readings.  Last, a grab sampler was used to collect sediment off of the mouth of the Puyallup River and at station two. 

Later, both groups came back to the lab to analyze the data.  Dissolved oxygen was analyed with the use of Winkler automated titration procedure (Carpenter 1966).  Chlorophyll-a was analyzed by the use of the flourometer (Strickland and Parsons 1972).  The nutrient samples were sent to the University of Washington Seattle Marine Lab to be examined.  Total sediment was weighed then sieved on a shaker  through screens to figure out percent grain size. Plankton samples were collected at both day and night time using plankton net tow.  Surface plankton samples were collected with a 20 µm mesh net, and 153 µm mesh at appropriate depth at station 2.  Both nets were deployed at each station to collect phytoplankton and zooplankton in a continuous vertical water column and horizontal surface water.  The collected specimens were brought back into the lab and examined under a compound microscope and dissecting scope for identification. A Palmer .1ml counting slide was used to count the phytoplankton and a Sedgewick Rafter .1ml counting slide was used to count and categorize zooplankton.

Click here! for more information on the basic collection and analysis methods

Niskin Bottle

Secchi Disk

CTD

References

Carpenter, J.H. 1966. New measurements of oxygen solubility in pure and natural waters. Limnology and Oceanography 11: 264-277.

Winkler, L.S. 1888. The determination of dissolved oxygen. Ber. Dtsche. Chem. Ges. 21: 2843-2855.

Strickland, J.D.H. and T.R. Parsons. 1972. A Practical Handbook of Seawater Analysis. Fisheries Research Board of Canada.