POC flux versus depth at ALOHA (22° 45′ N, 158° W) and K2 (47° N 160° E). (A) POC flux at ALOHA (triangles) and K2 (circles) with open and solid symbols for deployments 1 and 2, respectively (deployment start dates in Table 1). (B) Same data normalized to 150 m POC flux and compared with Martin et al. (4) (dashed line). For each depth, up to three independent NBSTs were deployed from the same launch site, and the POC fluxes are shown (A) for each NBST, with a slight vertical offset, as the mean and standard deviation of replicate POC measurements (n from 2 to 4). Fits to normalized data (B) used a power function of the form F/F150 = (z/150)–b, where z is the depth of the trap, F150 is the POC flux at the 150-m reference depth, and b describes the rate of flux attenuation.