Phytoplankton Primary Production in the California Current Ecosystem

 

The California Cooperative Oceanic Fisheries Investigations (CalCOFI) and California Current Ecosystem Long-Term Ecological Research (CCE LTER) programs work together to study the broad coastal upwelling biome along the California Coast.  Their study area encompasess three distinct regions: a nutrient, rich high productivity area along the coast, the lower-nutrient Southern California Bight, and a portion of the low-nutrient North Pacific Subtropical Gyre (one of the great ocean deserts).  The CalCOFI program has been going to multiple sites in this region since the late 1940s, when it was started to try to understand why the sardine fishery had collapsed.  Among other measurements, they have been measuring net primary productivity (NPP) to determine the total phytoplankton (algae) production in the euphotic zone (the sunlit upper region of the ocean) since 1970.  These scientists measure NPP using a technique known as C-14 bicarbonate uptake.  Using this method, the scientists collect a sample of water from a specific depth in the ocean.  This water sample (including the natural phytoplankton and zooplankton communities) is put in a clear bottle and the scientists add some carbon-14 labeled bicarbonate (HCO3-).  Bicarbonate is the form of dissolved inorganic carbon that is most common in the ocean.  In other words, it is basically the form of carbon dioxide that is most available to phytoplankton.  So when the phytoplankton conduct photosynethesis, they must take up bicarbonate from their environment.  After the scientists have added the carbon-14 labeled bicarbonate they will place their samples in incubators on deck that are kept at natural light levels.  The phytoplankton will take up the carbon-14 labeled bicarbonate at the same time that they take up natural bicarbonate.  After 24 hours the scientists will end their experiment and filter all of the phytoplankton from the seawater.  They can then measure how much carbon-14 was taken up by the phytoplankton, because carbon-14 is radioactive.  This allows them to measure the NPP of the entire phytoplankton community.  The scientists make this data freely available and if you want to download it for yourself you can access it at the CCE LTER DataZoo website.

 

The CalCOFI and CCE LTER scientists measure NPP at multiple depths (and hence different light levels) in the ocean at multiple sites along a regular grid in the ocean approximately four times per year.  They also make a suite of other measurements, such as phytoplankton pigments, nutrient concentrations, and temperature.  I have compiled some of these other data in the excel spreadsheet below.  These measurements might be useful in trying to understand what drives variability in primary production in this ocean region.

 

Please note that in this dataset the letters "NaN" means that a measurement was not taken.  Time-series evolve over time and logistical issues (e.g., 20-foot waves and 40-knot winds) can make it impossible to make every measurement every time.

 

CalCOFI Primary Productivity Data.xlsx

 

Data Columns:

 Cruise = the name of the CalCOFI cruise from which the data came

 Longitude = longitude at which the samples were collected (units = degrees west)

 Latitude = latitude at which the samples were collected (units = degrees west)

 Distance from shore = the distance from land (units = kilometers)

 Date

 Depth = depth from which the sample was collected (unit = meters)

 Temperature = temperature at which the sample was collected (unit = degrees Celsius)

 Salinity = salinity at which the sample was collected.  Unit = Practical Salinity Units

 Light Intensity = Intensity of photosynethetically-active radiation.  Unit = fraction of irradiance at the sea surface

 Oxygen = oxygen concentration (unit = milliliters of oxygen per liter of seawater)

 Oxygen Saturation = oxygen saturation relative to equilibrium with the atmosphere.  Note that oxygen saturation >100% means net oxygen production by the plankton community, while oxygen saturation <100% means net oxygen consumption by the plankton community

 Oxygen = oxygen concentration (unit = micromoles per kilogram)

 Chlorophyll a = the most important photosynthetic pigment found in nearly all plants and phytoplankton (unit = micrograms of chlorophyll per liter of seawater)

 Phaeopigments = a byproduct of chlorophyll a that is most frequently created when zooplankton consume phytoplankton and the chlorophyll gets acidified in their guts (unit = micrograms of chlorophyll per liter of seawater)

 Phosphate = the most abundant phosphorus-containing nutrient available to phytoplankton (unit = micromoles phosphate per liter of seawater)

 Silicic acid = the most abundant silicon-containing nutrient available to phytoplankton (unit = micromoles silicon per liter of seawater).  Note that only some phytoplankton (including diatoms) need silicon.

 Nitrite = a nitrogen-containing nutrient available to phytoplankton that is usually produced from ammonium during the process of nitrification (unit = micromoles nitrate per liter of seawater)

 Nitrate = the most abundant nitrogen-containing nutrient available to phytoplankton (unit = micromoles nitrate per liter of seawater)

 Ammonium = the most easily-utilized nitrogen-containing nutrient available to phytoplankton (unit = micromoles nitrate per liter of seawater).  Ammonium is given off by many heterotrophic bacteria and zooplankton.

 Net primary productivity (volume) = net bicarbonate uptake by phytoplankton in samples incubated at natural light levels (units = milligrams of carbon per miter cubed of seawater per day)

 Net primary productivity (vertically-integrated) = net bicarbonate uptake by phytoplankton in samples incubated at natural light levels vertically-summed from the surface down to the dark ocean (units = milligrams of carbon per meter squared of seawater per day).  This is basically the total photosynethesis of all phytoplankton in one vertical column of water.  Net primary productivity (vertically-integrated) is calculated from the data in Net primary productivity (volume).