RELEASE RATES OF TRACE-ELEMENTS AND PROTEIN FROM DECOMPOSING PLANKTONIC DEBRIS .2. COPEPOD CARCASSES AND SEDIMENT TRAP PARTICULATE MATTER

In experiments designed to relate the release kinetics of various elem ents with that of protein from biogenic particles, Ag-110m, Am-241, Cd -109, Co-60, Se-75 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-linea r release rate constants (k) of Ag=110m, Am-241, Cd-109, and Co-60 fro m carcasses ranged from 0.079 d-1 for Co-60 at 2-degrees-C to 0.130 d- 1 for Cd-109 at 15-degrees-C, and did not vary significantly with temp erature. Se-75 was lost most rapidly from copepod carcasses at 2-degre es-C, with k = 0.168 d-1; however, at 15-degrees-C, Se-75 was in two c ompartments, 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 lo ss from two compartments at both temperatures. At 2-degrees-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-degrees-C, how ever, 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 Ag-110m, Am-241, and Co-60 from sediment trap particles (15-degrees-C) ranged from 0.008 to 0.011 d-1. Protein was lost twice as fast as Ag- 110m, Am-241, and Co-60, more slowly than half of the particulate Cd-1 09 and Se-75 in rapidly exchanging pools (k = 0.168 and 0.237 d-1, res pectively), and at rates comparable to Cd-109 and Se-75 in slowly exch anging pools. Overall, copepod carcasses and fecal pellets could act a s vectors of these five elements and protein to the deep ocean, the ve rtical flux being dependent on settling velocity and water column temp erature structure. Of the elements considered here, Se follows the cyc ling of protein most closely.