Abstract

In experiments designed to relate the release kinetics of various elements with that of protein from biogenic particles, 110mAg, 241Am, 109Cd, 60Co, 75Se and protein were measured over time in radiolabeled copepod carcasses and particles caught in unpoisoned sediment traps (mostly zooplankton fecal pellets and amorphous marine snow). Log-linear release rate constants (k) of 110mAg, 241Am, 109Cd, and 60Co from carcasses ranged from 0.079 d−1 for 60Co at 2°C to 0.130 d−1 for 109Cd at 15°C, and did not vary significantly with temperature. 75Se was lost most rapidly from copepod carcasses at 2°C, with k = 0.168 d−1; however, at 15°C, 75Se was in two compartments, with 56% in a rapidly exchanging pool (k = 0.391 d−1) and 44% in a slowly exchanging pool (k = 0.107 d−1). Protein displayed loss from two compartments at both temperatures. At 2°C, protein was lost slowly (k = 0.065 d−1) for 1 wk, after which it was released from the carcasses very rapidly (k = 0.245 d−1). At 15°C, however, the loss of protein from carcasses was more rapid over the first 2 d (k = 0.627 d−1) than thereafter (k = 0.127 d−1). The k values of 110mAg, 241Am, and 60Co from sediment trap particles (15°C) ranged from 0.008 to 0.011 d−1. Protein was lost twice as fast as 110mAg, 241Am, and 60Co, more slowly than half of the particulate 109Cd and 75Se in rapidly exchanging pools (k = 0.168 and 0.237 d−1, respectively), and at rates comparable to 109Cd and 75Se in slowly exchanging pools. Overall, copepod carcasses and fecal pellets could act as vectors of these five elements and protein to the deep ocean, the vertical flux being dependent on settling velocity and water column temperature structure. Of the elements considered here, Se follows the cycling of protein most closely.

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