US JGOFS EqPac: Chloropigments and Amino Acid Concentrations in Sediment Cores and Traps


Cindy Lee
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 9N, 5N 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-
drifting traps

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, 2N, the equator, and 2, 5 and 12S.  Cores were sectioned aboard ship; similar 
sediment depth intervals from several cores taken simultaneously were composited and 
homogenized.  

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 
(~40%).

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, 399-408. 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, 809-833. 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. 831870. 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