US JGOFS EqPac: Chloropigments and Amino Acid Concentrations in Sediment Cores and Traps
EqPac (cruise 13 for collection of sediment cores)
Chloropigments and Amino Acid Concentrations in Sediment Cores and Traps
2.2. Analytical methods
For more detail on this data set, see: Lee, C; Wakeham,S.G.; Hedges, J.I., 2000.
Composition and flux of particulate amino acids and chloropigments in equatorial Pacific
seawater and sediments. Deep-Sea Research, I, 47 ( 8), 1535-1568.
Deep sediment traps were also deployed between January 1992, and January 1993, on
moorings (Honjo et al., 1995) at 9°N, 5°N and 0°. Both IRS-valved traps and valveless
(NVC no-valve control) traps collected samples from about 1000 m below the sea
surface, while NVC traps collected samples from ~1000 m above the sea floor (mab).
Traps were poisoned with mercuric chloride, and retention of poison was verified by
salinity measurements. Particulate material collected was split and filtered as for free-
Sediment cores were collected during November-December, 1992, from seven stations
along the N-S transect using a multiple corer (Barnett et al., 1984). These stations were
at 9, 5, 2°N, the equator, and 2, 5 and 12°S. Cores were sectioned aboard ship; similar
sediment depth intervals from several cores taken simultaneously were composited and
Particulate amino acids were measured by fluorescence high performance liquid
chromatography (HPLC) after acid hydrolysis (Lee and Cronin, 1982; 1984). Thawed
filters and sediments were hydrolyzed under N2 at 110degC for 19 h with 6 N HCl to
release THAA, total hydrolyzable amino acids in peptide bonds (proteins and peptides) or
adsorbed onto particles. Hydrolyzates were dried in vacuo, taken up in water, and the
resulting free amino acids were analyzed by HPLC using a modification of the Mopper
and Lindroth (1982) o-phthaldialdehyde derivative technique. Only one sample was
usually available from each site and depth for hydrolysis because of the splitting scheme.
Duplicate analyses of the same hydrolyzate agreed within 10-15% except for lysine
We report here results only for chlorophyll-a and some of its immediate degradation
products. Chloropigments were extracted from thawed filters into 100% acetone and
analyzed by HPLC with fluorescence detection (Mantoura and Llewellyn, 1983; Bidigare
et al., 1985). Samples were covered with Al foil as much as possible during handling and
analysis to exclude light. Details of our analytical methods appear in Sun and Sun. Here
we report data on chlorophyll-a (Chl), pheophytin-a (Phytin), pheophorbide-a (Phide) and
pyropheophorbide-a (Pyrophide) fluxes and composition. Monovinyl and divinyl
chlorophylls (Bidigare and Ondrusek, 1997) were not separated. Only one sample was
usually available from each site and depth for extraction because of the splitting scheme.
Duplicate analyses of the same extract agreed within 10%.
Barnett, R.P.O., Watson, J., Connelly, D. 1984. A multiple corer for taking virtually
undisturbed samples form shelf, bathyal and abyssal sediments. Oceanologica Acta 7,
Bidigare, R.R., Kennicutt, M.C., Brookes, J.M. 1985. Rapid determination of
chlorophylls and their degradation products by high performance chromatography.
Limnology and Oceanography 30, 432-435.
Bidigare, R.R., Ondrusek, M.E. 1996. Spatial and temporal variability of phytoplankton
pigment distributions in the central equatorial Pacific Ocean. Deep-Sea Research II 43,
Honjo S., Dymond, J., Collier, R. and Manganini, S.J., 1995. Export production of
particles to the interior of the equatorial Pacific Ocean during the 1992 EqPac
experiment. Deep-Sea Research II 42, pp. 831¯870.
Lee, C., Cronin, C. 1982. The vertical flux of particulate organic nitrogen in the sea:
decomposition of amino acids in the Peru upwelling area and the equatorial Atlantic,
Journal of Marine Research 40, 227-251.
Lee, C., Cronin, C. 1984. Particulate amino acids in the sea: Effects of primary
productivity and biological decomposition. Journal of Marine Research 42, 1075-1097.
Mantoura,R.F.C., Llewellyn, C.A. 1983. The rapid determination of algal chlorophyll and
carotenoid pigments and their breakdown products in natural waters by reverse-phase
high-performance liquid chromatography. Analytica Chimica Acta 151, 297-314.
Mopper, K., Lindroth, P. 1982. Diel and depth variations in dissolved free amino acids
and ammonium in the Baltic Sea determined by shipboard HPLC analyses. Limnology
and Oceanography 27, 336-347