Standard HOT protocols were used to measure in vitro primary productivity (PP) via the 14C 
radiotracer method [Karl et al., 1996]. Water samples were collected from 15m before dawn and 
incubated on deck in incubators screened to 30% of surface irradiance and plumbed with flow 
through surface seawater for temperature regulation. Duplicate 500-ml bottles were incubated 
in the incubator for ~12hr and 24hr, light bottles were paired with dark bottles. Following 
dawn to dusk or dawn to dawn incubations, each sample was filtered onto 25mm glass fiber 
filters. Filters were acidified with 1 ml of 2N hydrochloric acid in a fume hood for 12 hr to 
remove inorganic 14C after which 10 ml of Ultima Gold scintillation fluid was added each sample. 
Radioactivity was determined using a Perkins Elmer 2600 liquid scintillation counter; samples 
were recounted after 30 days.The rate of PP was calculated by multiplying the percent of carbon 
labeled by the total carbon available for photosynthesis (e.g. dissolved inorganic carbon, DIC, 
calculated from SST and salinity measured at each station as per Lee et al. [2006] and dividing 
by incubation time (t = 1 day) as follows. Rate measurements in light bottles were corrected 
to remove the rate measured in parallel dark bottles. 

12L 	= 12hr on deck, light bottle
12D 	= 12hr on deck, dark bottle 
12L-D 	= The difference between 12L and 12D
24L 	= 24hr on deck, light bottle
24D	= The difference between 24L and 24D

All units are in mg C/m3/day

HST Date	Station	Cast	Niksen	Depth target (m)	Average L12	Stdev L12	Average 12L-12D	Stdev L12-D12	Average L24	Stdev L24	Average 24L-D	Stdev 24L-D
7/26/2015	6	1	14	15	18.67	1.7	18.03	1.76	10.91	3.7	10.08	3.73
7/27/2015	16	1	12	15	18.23	0.4	17.58	0.39	10.68	0.4	10.06	0.45
7/28/2015	22	1	20	15	15.20	2.5	14.92	2.36	10.02	1.3	9.29	1.36
7/29/2015	30	1	20	15	17.73	1.5	16.90	1.53	11.52	1.1	10.75	0.97
7/30/2015	37	1	20	25	15.34	0.7	14.76	0.67	10.32	2.0	9.29	1.95
7/31/2015	44	1	20	15	15.98	0.6	15.30	0.64	10.90	0.1	10.16	0.08
8/1/2015	52	1	20	15	15.00	1.9	14.66	1.95	8.92	1.4	8.47	1.41
8/2/2015	58	1	20	15	18.55	2.7	17.91	2.67	13.01	0.5	12.12	0.54
8/3/2015	67	1	20	15	15.41	1.2	14.73	1.20	11.45	0.6	10.69	0.51