Compiling Nutrient Data on Cal COFI Line 67

Compiling Nutrient Data on Cal. COFI Line 67 for a Spring and Fall Cruise. LT Anna C. (Christy) Bryant

Objective • Analyze data regarding nutrients taken during the CTD casts during Leg 1 of OC 3570 cruise. • Unfortunately. . .

Solution • Use data from a September, 2000 cruise • And just to see the differences…added in a data set from a May 2000 cruise

Background

Cal. COFI Grid Monterey Cal. COFI Line 67 Bay

Upwelling Index Location

The Data • Occasional instances of ‘no data’ – Bottles not measured – Depth of last bottle varied • None of the data was “square” – Linear interpolation was used to square it • Cruises covered different distances – One was 425 km, one was 275 km

Some Data Points “no data”

Other “no data” points were treated. . .

“Squaring Data” * Collection Points - Interpolated line

Nutrients • Consistently tested were: – Si. O 4 (Silicate) – PO 4 (Phosphate) – NO 3 (Nitrate) • Nitrate is the limiting macronutrient for phytoplankton in these waters (typically). » (Pennington and Chavez, 2000)

NO 3 in M/l May 2000 Sept 2000

May 2000 Sept 2000

NO 3 Profiles May 2000 Sept 2000 NO 3 M/l D E P T H (m) Profiles progress from C 1 towards the west. Sept goes to 425 km off the coast, while May only goes to 275 km.

Sept-May 2000 NO 3 Contour September has more off -shore September has less near shore

Upwelling Index taken from Upwelling Index Update, U. S. West Coast, 33 N-48 N Latitude Units in Cubic Meters per Second per 100 Meters of Coastline April/May Significantly Higher than Sept nearshore

PO 4 in M/l May 2000 Sept 2000

Si. O 4 in M/l May 2000 Sept 2000

Temp (ºC) May 2000 Sept 2000

Difference Contours

Summary and Conclusions 1) Nutrients showed very similar profiles along the Cal. COFI line for May and September, 2000. 2) Higher values of nutrients in the vicinity of the M 1/H 3 station for May are in keeping with the averaged Upwelling Index for locations just South and North of the station. 3) Data from several more cruises would have been more illuminating, perhaps one per month. Once the program problems were fixed, creating more profiles doesn’t take much time.