The following are the field sampling methods used by the class:

Secchi: Turbidity was determined by using a secchi disk. By lowering this disk into the water and watching until one person can no longer see it. The depth at which the disk can last be seen is then recorded. One must note that only one person should watch the secchi at all times. This will help ensure the data is more accurate since everyone has a least a minor difference in their vision. Also, when measuring the depth it is important that the line on the rope be level with the surface of the water since the depth is taken from the surface of the water downwards. If the line is out of the water, or under the surface the secchi depth with be off.

CTD: The CTD instrument is a Seabird 19 instrument which records pressure, temperature, salinity, conductivity, dissolved oxygen and light transmission.  The CTD is suspended right below the water line for three minutes. This ensures that all the air has been forced out of the tubes and the water is properly circulating through the instrument.  At the end of three minutes the CTD is lowered at a rate of approximately one meter per second because as the CTD is being lowered it records data at approximately meter intervals. The instrument is lowered to a predetermined depth ranging from approximately one to five meters above the sea floor. It is extremely important to make sure that the depth is gauged right before the CTD is lowered and even while it is being lowered if there is a strong current as the boat could drift to a more shallow area. If the CTD were to hit the floor it could be damaged depending on how hard it hits the bottom, the type of sediment and if larger quantities of sediment were sucked into the CTD tubing causing a blockage.

Nisken bottle: a Nisken bottle was attached to the cable the CTD was connected to at a meter above the CTD instrument.  From this Nisken bottle bottom water samples were collected.  The way a Nisken bottle works is that when a Nisken bottle is in the water its ends are open. When bottle is at the right point in the water the bottle is “tripped” so the ends snap shut.  For the bottom Nisken bottle when the bottle is at desired depth a copper weight called a messenger is sent down the line and it trips the bottle casing the ends to snap close therefore, capturing the water at that exact depth about a meter above the bottom

Nisken bottle on a rosette: On larger boats a CTD with a rosette may be used.  This rosette has several Nisken bottles surrounding the CTD. Both the CTD and rosette has a cable running from it back to the boat computer. From here each bottle can be tripped at different depths and does not require the use of a messenger like a single Nisken bottle does.

Thoreson bottle:  A Thoreson bottle works similar to a Nisken bottle. It is used to capture water at a specific depth. However, the Thoreson bottle is used to collect surface and thermocline water samples. And rather than the use of a copper messenger the bottle is tripped by jerking on the rope quickly to close.  It can be tricky to do, and often takes several tries to close the bottle. Though it can be tricky, one must take care not to raise the bottle too much or else the sample will contain water from a different depth. This is especially true at the surface. The operator must take great care to not pull the bottle out of the water and including excess air in the sample as this will taint the dissolved oxygen analysis.

Plankton Net: Plankton samples were also collected at each station using a mesh net by pulling the net horizontally at the surface and pouring the water from the cod end into a glass sample jar.  Samples from the 20-micrometer net tow were then prepared and counted under a microscope at the University of Washington Tacoma lab.

Plankton sample collection:  A labeled glass jar is filled with water from the Thoreson bottle at the surface and thermocline. To ensure accurate data and to prevent a growth in population the jars are then put on ice in the dark.

Dissolved oxygen sample collection: Oxygen samples were collected by first attaching a small rubber hose to the spout of the Nisken bottle.  The water was allowed to run for a bit to make sure there were no air bubbles in the hose.  Then the hose was put into the Erlenmeyer flask, the flask was then held upside down and the flask rotated twice to clean the flask.  Next the flask was held upright and filled to overflowing and with water still running the flask was pulled down till it cleared the tube and then the water was turned off.  This was done to prevent any additional air getting into the sample.  Immediately, the sample was fixed with 1 ml manganese chloride and 1 ml NaOH-NaI, the flask lid put on and flask shaken and then stored in a dark place. Two samples of dissolved oxygen samples were taken at surface, thermocline and bottom depths of the water column.

Chlorophyll sample collection: Chlorophyll samples were collected using 145ml bottles. Each bottle was washed 3 times with the sample water. Then bottle was filled to the top and then stored in the ice chest.  Chlorophyll is later analyzed the same day as collection to ensure accurate data as measuring chlorophyll indirectly measures the amount of photosynthetic organism in the water. If the samples were left to be analyzed at a later time the organisms may begin to break down due to the using up the oxygen present in the water and lack of light. Two chlorophyll samples were taken at surface, thermocline and bottom depths of the water column.

Nutrient sample collection: The sample water from the Nisken bottle is put into a tube with a filter attached and the filtered water is used to rinse out the collection bottle twice.  Then the collection bottle is then filled about half way with the filtered water and then stored in the ice chest.  When return to the lab the samples are then frozen and later the samples are sent to UW Seattle and analyzed. Two nutrient samples were taken at surface, thermocline and bottom depths.

LiCor readings: LiCor measurements are used to determine the amount of light penetrating the water at varying depths. The first reading was taken holding the Li-cor instrument just above the water, the next reading was taken at holding the instrument just below the surface of the water and then readings recorded at meter intervals until the either a reading of zero was reached or the reading leveled off and did not continue to change.

van Veen: Take note that this instrument should be used after all other measurements and samples are taken to prevent the data/sample from being tainted if the Vanveen opens on the way up releasing the sediment. To use this piece of equipment first, ensure that the collector is open and the pin is in place to keep it open. Lower the collector into the water making sure to keep constant tension on it. Once it reaches the bottom (the operator should be able to tell because there will be some slack in the line) pull the instrument up and out of the water. Make sure to keep a constant tension on it. The container is more likely to stay closed if it is hauled up quickly and steadily. Once it is out of the water place it into a tub releasing all of the sediment. Once it is empty transfer enough sediment into a pre-labeled, one gallon plastic bag, to fill it two-thirds of the way. Immediately place it in the dark on ice to avoid the breakdown of any organisms within the sediment or the formation of algae.  The sediment is then returned to the lab to be analyzed for grain size and total organic carbon.

Zooplankton catch net: The Zooplankton catch net works by being placed into the water open. It descends to a predetermined depth, and then rises to another, more shallow depth (usually approximately 30 meters above the deepest point it descended).  At this point a messenger is put on to close it. This ensures that only the zooplankton that is present within a certain number of meters is caught in the net allowing the operator to sample at only certain depths. The net itself is 153 micrometers to ensure it captures the zooplankton but is large enough that the small phytoplankton can pass through.

Analysis Methods: For laboratory standard operating procedures click here.