Oceanographic Factors Affecting Phytoplankton Distribution in Monterey Bay, CA LT Adria McClain

Outline Intro to Phytoplankton Measuring Phytoplankton Concentration Factors Affecting Phytoplankton Distribution Physical Upwelling Nutrient Availability Dissolved Gas Topographic References Questions

Phytoplankton Autotrophic component of the plankton Obtain energy thru photosynthesis; must live in euphotic zone (midlats: sfc to ~70m) Primary Producers Create oxygen and organic compounds 6 H2O + 6 CO2 ----------> C6H12O6 + 6 O2 Depend on macronutrients (nitrates, phosphates) for growth Form base of marine trophic pyramid

Measuring Primary Productivity Fluorometer affixed to an Autonomous Underwater Vehicle (AUV) or to a CTD Chlorophyll concentration used to estimate biomass Expose chlorophyll in phytoplankton cells to wavelengths of light that cause the pigment to fluoresce Intensity of fluorescence read electronically to give direct measure of chlorophyll and quantity of plant material in water

Fluorometer Data Monterey Bay Aquarium Research Institute (MBARI) AUV Survey for BIOLUME Campaign Period of survey: 1/29/2007 1318 PST to 1/30/2007 0925 PST CTD-AUV collected water temperature, salinity, pressure, dissolved gas concentration, chlorophyll concentration, etc AUV programmed to follow sinusoidal course through water column (alternatively diving and surfacing) along grid pattern CTD data from OC3570 student cruise aboard R/V Pt. Sur

Upwelling NorCal: Northwesterly winds lead to upwelling Cold, nutrient-rich water rises to surface Phytoplankton blooms occur 6-10 days after an upwelling event (Service et al., 1998 and Fiedler et al., 1998)

Upwelling

Phytoplankton Bloom? Wind direction and wind speed from MBARI M1: 36.7oN 122.0oW NW winds of 8-10m/s on or around 17 Jan Winter n’westerlies less strong than summer n’westerlies (weaker upwelling events in winter) NOAA Image: appears to be an upwelling event Jan 18-21 AUV Chlorophyll concentration data from 29/30 Jan “Bloom” w/in 10 day period following upwelling event Increased wind-forcing linked to increases in primary production and surface chlorophyll (Croll et al.,2005)

Nutrient Availability Increasing nitrogen in ocean linked to high productivity (Sverdrup, pp. 389) Inorganic nutrients required for primary production include nitrate (NO3-) and phosphate (PO43-) Nitrogen and phosphorus depleted by photosynthesizing organisms during times of high productivity and rapid reproduction (Garrison, pp. 234)

Dissolved Gas Generally, colder water contains more gas at saturation Photosynthesis near the surface increases the amount of dissolved oxygen O2 least abundant just below euphotic zone due to marine animals respiring at middle depths (Garrison, pp. 235-236)

Topography (Ryan et al., 2005) Observed during 2005 MBARI AUV Survey Internal tides and wind-driven currents caused cold, dense water to flow from Monterey Canyon Water flowing over continental shelf produced a plume of turbid water Increased phytoplankton concentration observed above plume; plume likely carried macronutrients upward

Topography (Ryan et al., 2005) Observed during 2000 MBARI AUV Survey Incoming tide flowed over edge of canyon; produced 10m internal wave (“lee wave”) Phytoplankton layer 10-20m below surface to the north; highly concentrated phytoplankton layer nearest canyon Wave crest “bisected” phytoplankton layer thereby changing its properties

References Canyons, currents, and algal blooms— How Monterey Canyon influences the growth of microscopic marine algae http://www.mbari.org/news/homepage/2005/ryan-blooms.html April 2005 Croll, D.A., et al., 2005. From wind to whales: trophic links in a coastal upwelling system. Marine Ecology Progress Series, 289, 117-130. --, et al., 1998. An integrated approach to the foraging ecology of marine birds and mammals. Deep-Sea Research II, 45, 1353-1371. Fiedler, P.C., et al., 1998. Blue whale habitat and prey in the California Channel Islands. Deep Sea Research II, 45, 1781-1801. Garrison, T., 2001. Essentials of oceanography (2nd Ed.). Brooks/Cole, Pacific Grove, CA. NOAA Fisheries Service: Live access to ERD environmental data http://las.pfeg.noaa.gov/las6_5/servlets/constrain?var=176 Olivieri, R.A., F.P. Chavez, 1999. A model of plankton dynamics for the coastal upwelling system of Monterey Bay, California. Deep-Sea Research II, 47, 1077-1106. Ryan, J.P., F.P. Chavez, J.G. Bellingham, 2005. Physical-biological coupling in Monterey Bay California: topographic influences on phytoplankton ecology. Marine Ecology Progress Series, 287, 23-32.

References Service, S.K., J.A. Rice, F.P. Chavez, 1998. Relationship between physical and biological variables during the upwelling period in Monterey Bay, CA. Deep-Sea Research II, 45, 1669-1685. Sverdrup, K.A., A.C. Duxbury, A.B. Duxbury, 2005. An introduction to the world’s oceans (8th Ed.), McGraw-Hill, New York, NY.

Questions?