The Chemical Connection Between Wind and Whales It is the supply of nutrients, driven by winds and coastal upwelling, that allows the remarkable productivity to occur in much of the Monterey Bay area. Ken Bruland’s component of the CIMT Program - prepared by Ken Bruland - presented by Raphe Kudela Our group participates on the survey cruises and we are now responsible for the determination of: Macronutrients: Nitrate, Phosphate, and Silicic acid Micronutrients: Dissolved Iron (along with other metals) Leachable Particulate Iron (along with other metals)

Coastal upwelling in different regimes Fe Replete Extensive blooms of large Diatoms High Biomass Uncoupled from grazers High variability High Export Production Fe Deplete Non bloom conditions large diatoms rare Relatively low biomass Tightly coupled with grazing Low variability Regeneration

Typical late spring/early summer sea surface temperature image in June 2004 under upwelling conditions. Note the cold, 10 degree C water off Davenport that advects out into the middle of Monterey Bay. Typical surface Chlorophyll image during this same time period. Note low chlorophyll in the freshly upwelled water and the bloom occurring as the water ages and warms. Fe-replete Gulf of the Farallons Monterey Bay ? Fe-deplete Big Sur Coast

Davenport Santa Cruz Monterey Location of a surface transect carried out in June 2004 Davenport Santa Cruz Ship’s Track Monterey

The cold temperatures in surface waters near Davenport indicate an upwelling region. Freshly upwelled waters in this area are on the order of 10.4 degrees Celsius and have a salinity approaching 33.8. The surface transect was carried out on June 21, 2004. Davenport

The cold upwelled waters off Davenport are nutrient rich The cold upwelled waters off Davenport are nutrient rich. Dissolved nitrate concentrations in excess of 20 M, along with silicate concentrations of 30 M are adequate to support extensive blooms of large diatoms. By the time the water has aged and warmed near Capitola, the dissolved nitrate and silicate have been assimilated.

Along with the high concentration of dissolved nitrate and silicate, there is a few nM of dissolved iron in the upwelled water feeding this area. This iron is adequate for an extensive diatom bloom to occur. The high fluorescence signal that occurs where the nitrate and iron are assimilated indicates the high phytoplankton biomass. Upwelling center Phytoplankton bloom

Location of CIMT stations within Monterey Bay Upwelled “source water” for the Bay

Davenport upwelling “source” water for the Monterey Bay Salinity Temperature Silicate Nitrate Dissolved Fe and especially leachable particulate Fe appear to peak in the March to May upwelling season and are lower during summer upwelling. This supports what Ken Johnson and Steve Fitzwater at MBARI have observed. A potential scenario is that in April/May the system would be Fe-replete, but that in summer it may be Fe-deplete

Summary, The nutrient data from the various cruises can be correlated with temperature and/or salinity to obtain relationships that will facilitate modeling efforts. During upwelling in March through May, there appears to be high dissolved and leachable particulate Fe brought to the surface with the upwelled macronutrients. During this time, the Bay should be Fe-replete. During upwelling in June to August, there appears to be low dissolved and extremely low leachable particulate Fe entrained with the upwelled macronutrients. This may lead to Fe-limited systems, particularly in the central Bay. The near shore areas may be particularly important during these times as they could have an extra source of iron from the near shore sediments. During summer, there may be cases where Fe-limitation could also influence domoic acid production.

Chlorophyll a