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Ocean 410/430 Thompson Cruise Name:________________________________________ 30 September 2013

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GOALS 1

1. PLANKTON SAMPLING 2

1A. ZOOPLANKTON VERTICAL NET TOW 3 1B. PHYTOPLANKTON NET TOW 4 1C. PHOTOSYNTHESIS & RESPIRATION: BOTTLE INCUBATIONS. 5

2. WATER COLUMN STRUCTURE 7

3. MORPHOLOGIC FEATURE IDENTIFICATION 8

5. BOX AND KASTEN CORING 10

6. MULTIBEAM SONAR EXERCISE 11

Goals -‐ Learn to identify phytoplankton and zooplankton in Elliot bay -‐ Measure phytoplankton respiration rates with a bottle incubation experiment -‐ Understand the morphologic and sub-‐bottom features in Elliot Bay through the

examination of two landslides -‐ Interpret different kinds of sediment cores -‐ Learn to plan a multibeam survey -‐ Be safe and have fun! (you’re on a boat!)


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1. Plankton Sampling What are plankton? Plankton consist of plants and animals that drift with water currents and can make no significant swimming movements against a current. Plankton are not uniformly distributed in the sea, instead they tend to have patchy distributions (i.e. they show clumped or aggregated distribution). In general, plankton may be categorized according to size (picoplankton, nanoplankton, microzooplankton, etc.). They may also be characterized by functional role in the environment: Phytoplankton – the plant-‐like photosynthesizing component of the plankton (microscopic, mainly unicellular algae) Zooplankton – the animal component of the plankton, which range from microzooplankton to megaplankton (i.e. jellyfish!) Phytoplankton and zooplankton distributions in the water column are commonly sampled using plankton nets. Many plankton nets are conical in shape, tend to be made of nylon (or nitex) and are woven into a consistent mesh size so that the holes between the threads are of equal size. The mesh size of the net determines what type of plankton is retained when towing the net. Nets with a finer mesh size retain phytoplankton and small zooplankton and nets with a coarser mesh size retain larger zooplankton. In order to estimate the concentration of different types of plankton, it is necessary to take counts of plankton species of interest caught in the nets and also have an idea of the volume of water filtered by the net. Beyond the scope of this cruise (but still totally cool!), there are also bacterioplankton (bacteria) in the water column. They are diverse in their functions in the environment and are sampled using water bottle (niskin) samples. For the exercise, we are going to attempt to identify several species in the sample and estimate their concentrations in the water column.


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1a. Zooplankton Vertical Net Tow Station #:_____________ Latitude:________________ Longitude:_____________

Depth of tow: _____________________________

Diameter of net: ____________________________

Volume of water filtered, in liters (area of mount of net x distance towed): __________________

Mesh size of net:___________________________

Take a known volume of the sample (maybe 2-3 ml) and estimate the abundance of two types of zooplankton in this sample using the following steps: Identify 2 organisms of interest and sketch them. Name: Name: Abundance in _______ ml: Abundance in _______ ml: Now, scale these abundances back to the total volume to determine abundance in the area of the water column sampled. To do this, first you have to figure out abundance in the total sample. This can be determined by first figuring out what fraction of the total sample you examined and then dividing the number of organisms you observed by this fraction. Then to figure out how many zooplankton are in 1 liter of water all you have to do is divide this value by volume of water filtered to get organisms/L. Zooplankter 1: Zooplankton 2:

DON’T FORGET: Record your results on the cruise datasheet!!


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1b. Phytoplankton Net Tow Station #:_____________ Latitude:________________ Longitude:_____________

Diameter of net: ____________________________

Volume of water filtered, in liters (area of mount of net x distance towed): __________________

Mesh size of net:___________________________

Draw and identify four phytoplankton you observed in the sample. Name: Name:

Name: Name:

Phytoplankton require light to photosynthesize so it is extremely important that you stay up in the well-lit portion of the water column. Examine the structures of the different phytoplankton you observed. List and explain possible adaptations, if any, each phytoplankton has to help them resist sinking out of the photic zone.


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1c. Photosynthesis & Respiration: Bottle Incubations. The total amount of organic material produced through photosynthesis is termed gross primary productivity (GPP). Because phytoplankton respire some of their organic matter, not all of the organic matter they produce is available for consumption by higher trophic levels. The total carbon fixed during photosynthesis minus that part which is respired is termed net primary productivity (NPP). A method to measure the respiration and photosynthetic rates is to incubate in ambient light and temperature conditions a portion of a water sample in a clear bottle (“light bottle”) and another portion in an opaque bottle which light cannot penetrate (“dark bottle”). We will measure oxygen concentrations in the bottles, and how the oxygen concentration changes from the start until the end of the incubation period. 1.) What process(es) is/are occurring in the “light bottles”? (Circle all that apply)

Photosynthesis Respiration

2.) What process(es) is/are occurring in the “dark bottles”? (Circle all that apply)

Photosynthesis Respiration

3.) The change in O2 concentration in the light bottle indicates: (Circle answer)

Gross Primary Production Net Primary Production Total Respiration

4.) The change in O2 concentration in the light bottle – Final O2 concentration in the dark bottle

indicates: (Circle answer)


5.) The change in O2 concentration in the dark bottle indicates: (Circle answer):


6.) What was the initial oxygen concentration of the sample water? _____________________

7.) What is the final O2 concentration in the “light bottle”? __________________________

8.) What is the final O2 concentration in the “dark bottle”? __________________________

9.) Using the results of your experiment, calculate the respiration rate. Your answer should be in

mg O2 L-1 hr-1.


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10.) Using the results of your experiment, calculate net primary production (NPP). Your

answer should be in mg O2 L-1 hr-1.

11.) Using the results of your experiment, calculate gross primary production (GPP). Your

answer should be in mg O2 L-1 hr-1.


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2. Water column structure Station #: Latitude: Longitude: Secchi disk: The secchi disk is a very simple device used to measure the transmission of visible light in the upper watch column. It is basically a white and black disk about 30 cm in diameter (although size can very) attached to a rope that is marked off at some depth interval (perhaps 0.5 or 1 meter). To estimate how well light is transmitted in the water column you lower the secchi disk over the sunny side of the boat until it can just no longer be seen. As you pull the disk back up, record how deep you could see the secchi disk. This provides a simple measure of turbidity, which can be used for a relative comparison from station to station. Secchi disk reading: _____ m Does this seem like a lot or a little visibility? And What are some factors that might influence the transmission of light in the water column? CTD cast: Sketch the water column profile you observed during the CTD cast. Include: Salinity, Temperature, Transmissivity, PAR and Fluorescence. You might need to make a couple sketches – one with salinity and temperature and another with transmissivity, fluorescence and PAR Do you think the weather of the past week has had any influence on the water column structure you observed today? Why or why not? Does the water column appear to be well mixed or stratified? Explain.


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3. Morphologic feature identification Identify and label morphologic features such as dredge spoils, canyon, landslide scarp, etc. on the following two bathymetric maps.


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5. Box and Kasten coring Is there any physical layering present in the cores we collected? What would be an effective approach to investigate layering? Describe the sediment properties observed in at least one of the cores. What mechanisms caused these properties? In the core logs below, sketch the major features from one of the cores we collected (e.g., layering if present, grain size, color). Is there anything else you notice that could be important when interpreting geological significance? Core location:

Date:

Water depth:

Depth in core cm

cm

cm

cm

cm

cm


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6. Multibeam sonar exercise Multibeam sonars are used to map the seafloor by sending out a fan of beams to measure depth in a profile in the across-‐ship direction. The maps on pages 8-‐9 were created using data collected using a multibeam sonar. For this exercise, you will determine how long it would take do a multibeam survey of Elliot Bay using an EM302 (the same system that is on the Thompson). The survey will be conducted to the right (East) of the red line below. For simplicity, you may assume an average water depth of 100m.

1 nm You need 100% overlap between adjacent swaths. This means that the edge of your swath must “touch” the center of the line beside it (see the following figure for an illustration of this concept).


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1) What is the swath width of the EM302 system, as a multiple of water depth? Hint: you can find this in the EM302 specifications, or if you ask the multibeam operator nicely, he/she may help you out. 2) Using the swath width specification from the previous question, calculate the swath coverage (S) for your assumed water depth. Use S to calculate H, the horizontal spacing between lines. 3) Using approximate dimensions from the map above, calculate how many North-‐South survey lines you would need to do (an approximate is fine, this is just to get the concept). 4) What would be the average length of the lines (again, a decent approximate is fine here)? 5) From the previous two questions, calculate the total length of the survey, in meters. 6) If the ship can survey at 4.5 kts, how long would it take to run your survey? (Just the lines, don’t worry about turning time).

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