Image sources  http://www.geocities.com/SiliconValley/6603/animal.htm and http://www.stanford.edu/group/Urchin/GIFS\c-urchin.gif

Biological Blooms

In Learning Activity 1 you learnt about phytoplankton and how it causes 'red tides'. In this Activity you are going to learn how environmental variables such as water temperature and depth, salinity and nutrients affect the distribution of these plants. This is important for scientists to be be able to predict when and where red tide blooms will occur.

You are going to focus on one region near the Gulf of Alaska called the Cook Inlet that has already been the focus for study by biologists from the Alaskan Science Centre. All of the information and data for this Learning Activity has been taken from the Centre's marine habitat webpage http://www.absc.usgs.gov/research/seabird_foragefish/ marinehabitat/ index.html

Firstly consider what kinds of animals make up an Alaskan marine habitat. After looking at the food web below read about the importance of phytoplankton as producers, upon which all animals rely for transfer of energy. This link also contains information on how phytoplankton concentration is measured.

An Example of an Alaskan Food Web

http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/index.html

Consider other ways in which phytoplankton blooms in turn affect the rest of the food web. For example, the vertical distribution of phytoplankton in the water column affects how light distributes further down in the water column to marine algae.

Biologists have already collected data on salinity, nutrients, water temperature, depth and zooplankton numbers from twelve stations across Cook Inlet, shown below. You are going to use the data collected from Station numbers 3, 6, 9 and 12 and relate this to the distribution of phytoplankton using an Excel spreadsheet.

Map of Cross-Inlet Transect in Lower Cook Inlet. Stations are labelled 1-12.

http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/index.html

First however you will need some more background information to help you think about the questions below after you have plotted the data. Read about how the contour or bathymetry of the ocean floor greatly influences what animals live where.

Note that when you link to the `bathymetry' and other pages below you should resist reading the "What we learned" sections. You will be required to write a point form summary of each link paragraph in the first lesson on this activity. Remember your teacher will be watching very closely!

Water Depth

Now, look at the Excel spreadsheet below. The data for water depth have already been entered for you. You will see when you look at the transect profiles for each of the temperature, salinity and other parameters, that water depth is displayed as a grey area along the bottom of every profile. Water depth does vary a little between profiles, but for the purpose of this exercise you will plot data for the other variables at the assigned depths for each of the 4 sites.

Zooplankton

Now read more about zooplankton, their role in this food web and how the concentration of zooplankton can be measured in water samples. Read values for zooplankton concentration, measured as settled volume of animals in the collected water samples, off the following graph for each of the four sites. Enter  the data in cells B4-E4 in the spreadsheet.

http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/index.html

Nutrients and Phytoplankton (chlorophyll a) Concentrations

Now read about nutrient cycling in ocean waters. Enter the values for chlorophyll A shown in the graph in cells B5 to E5. Then add the values for total N + SiO4 below to work out the total concentration of nutrients to enter into the spreadsheet above (cells B6 to E6).

Concentrations of Nitrogen (N), Silica (SiO4), and Phytoplankton (Chlorophyll a)

across Cook Inlet.

http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/index.html

Temperature

You have already read that upwelling regions of cold water favour the concentration of nutrients and phytoplankton. Look at the following profile of water temperature across the Inlet. Remember that the grey area denotes the water depth across the transect. Therefore the inlet is deep at CIT-1 and shallow at CIT-12.

Profile of Ocean Temperatures across Cook Inlet

http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/index.html

To enter the data in the Excel spreadsheet for temperature, simply read what line of temperature above matches with the depth at each of the four stations. So at CIT-3 where the depth has been assigned as -55m, the corresponding temperature line is 9.4 degrees. Enter this value in cell B7 above. Site CIT-6 that has a depth of -40m assigned, is in a relatively cool region (denoted by the darkest green) with a temperature of 8.6 degrees. Enter this value into cell C7 above. Continue filling in the temperature data at site-9 and site-12 in cells D7 and E7.

Salinity

Read the background information on salinity, then plot the salinity data in the spreadsheet (cells B8 to E8) for the four sites, as you did for temperature, using the following profile:

http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/index.html

You are now ready to plot the data. Follow the `Excel Exercise' link.

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Copyright © March 2003.

Website designed by Bronwyn Atcheson, Student at Queensland University of Technology, Queensland. Email b.atcheson@student.qut.edu.au