San Juan Islands
San Juan Islands
[TESC 431 Home][Introduction] [Methods] [Results/Discussion] [Summary] [Data Repository]

Methods

Samples were collected April 29th in the Strait of Juan de Fuca and April 30th in the San Juan Channel. All field measurements were conducted aboard the Centennial research vessel at Friday Harbor Laboratories, shown in the pictures below. The parameters measured at each station were CTD profile, dissolved oxygen (DO), nutrients, chlorophyll and secchi depth readings.

Plankton analysis was done at selected stations only. A deep zooplankton tow was conducted at station one, while surface phytoplankton samples were collected at stations one, three, four and the pier at Friday Harbor Laboratories.

Friday Harbor Labs

The CTD took a depth profile of oxygen, temperature, salinity, density, and fluorescence. An onboard winch controlled descent and ascent of the machine. The CTD was lowered into the water at approximately one meter per second until it reached near bottom. Though data was recorded on both the descent and ascent, only the data from the descent was processed. Niskin bottles were attached to a CTD Rosette to collect water samples at various depths. Water samples were collected for the purpose of analyzing dissolved oxygen, nutrients and chlorophyll levels. Please see the Methods and Equipment section for a detailed description of sampling techniques and lab analysis.

UW's Rosette CTD
Secchi disk readings were taken to measure transparency of the water. A standard freshwater secchi disk was lowered overboard into the water. The disk was lowered until it was no longer visible and the depth recorded. This procedure was completed three times and an average secchi disk reading was recorded.

Plankton samples were collected at predetermined stations offering a biological profile throughout the area. The plankton nets and collection depths varied at each station. All samples were taken back to the lab for qualitative and/or quantitative analysis. Quantitative analysis of zooplankton was recorded for the deepwater samples by counting the number of zooplankton observed in a one mL sample. This data was then extrapolated to obtain the density of the water column sampled. For the surface samples, the number of phytoplankton was recorded by counting phytoplankton observed in a .1 mL slide. This data was also extrapolated. Sediment samples were collected in the Strait of Juan de Fuca at station one using a Van Veen sediment grab. Once collected, the samples were placed into a Ziploc bag and taken back to the lab for grain size analysis. Grain size analysis was completed using a Coulter LS 200 Partical Size Analyzer (PSA) and mechanical sieving. Please see the Methods and Equipment section for a detailed description of plankton and grain size analysis.

A summary table of sampling activities can be found below.

Plankton Tow Net



Van Veen



Sampling Summary Table
St. # Depth (m) Chlorophyll Dissolved Oxygen Nutrients Plankton Deep Plankton Tow Sediment
1 1 y y y y n n
10 y y y n n n
49 y y y n n n
109 y y y n 120-80m y
2 1 y y y y n n
8 y y y n n n
47 y y y n n n
130 y y y n n n
3 1 y y y y n n
7 y y y n n n
130 y y y n n n
4 1 y y y y n n
33 y y y y n n
100 y y y y n n



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[TESC 431 Home][Introduction] [Methods] [Results/Discussion] [Summary] [Data Repository]

Website created by Levi Keesecker and Laura Nokes, June 2005