» Home » HOT » Analytical Methods & Results

Bottom-Moored Sediment Traps

A bottom-moored sediment trap experiment has been in place since June 1992 at a site near Station ALOHA. Schedule of deployments and retrievals is shown in Table 1 below. The ALOHA-XIII mooring was deployed in June 2007 and is scheduled to be recovered in June 2008. The present experiment consists of 2 Parflux MK7-21 sequencing sediment collectors locate at 2800 & 4000 m. A separate sampling cup is rotated into the collector position on an approximately 15-20 day cycle, depending on the deployment period. Samples from each cup are initially divided into four 60-ml volumes (also refered to as splits). Each split is further divided into the volumes required for the various analysis (Table 2).

Designation    Location                  Depth     Schedule

   ALOHA-I     22 57.3'N, 158 06.2'W     4,800     Jun 1992 - Sep 1993
  ALOHA-II     23 06.7'N, 157 55.8'W     4,800     Sep 1993 - Oct 1994
 ALOHA-III     22 50.2'N, 157 55.9'W     4,800     May 1995 - Oct 1995
  ALOHA-IV     22 51.7'N, 157 54.3'W     4,800     Nov 1995 - Oct 1996
   ALOHA-V     22 51.0'N, 157 53.7'W     4,800     Oct 1996 - Dec 1997
  ALOHA-VI     22 51.5'N, 157 55.8'W     4,800     Dec 1997 - Nov 1998
 ALOHA-VII     22 51.8'N, 157 55.4'W     4,800     Nov 1998 - Oct 1999
ALOHA-VIII     22 49.3'N, 157 52.5'W     4,800     Nov 1999 - Nov 2000
  ALOHA-IX     22 48.7'N, 157 54.1'W     4,800     Dec 2000 - Mar 2002
   ALOHA-X     22 48.3'N, 157 55.3'W     4,800     Jun 2002 - Jun 2003
  ALOHA-XI     22 50.5'N, 157 52.4'W     4,800     Nov 2003 - Mar 2005
 ALOHA-XII     22 49.7'N, 158 05.1'W     4,800     Jul 2005 - Sep 2005
ALOHA-XIII     22 51.5'N, 157 55.1'W     4,800     Jun 2007 - Jun 2008

Table 1: Schedule of Deployments and Recoveries of Moored Sediment Trap

Investigator	Institution	Analyses
D. Karl, L. Tupas, D. Hebel, U. Magaard, T. Houlihan, D. Sadler, H. Nolla	University of Hawaii	Total mass, dissolved N, P, Si, total and biogenic particulate C, N, P, Si, fluorometric chloropyll a, phaeopigments, stable C, N isotopes, bacterial abundance
R. Bidigare, S. Christensen	University of Hawaii	Pigments by HPLC, diatom abundance and composition
D. Bird	University of Quebec at Montreal	Virus abundance
S Honjo, S. Manganini	Woods Hole Oceanographic Institution	Lithogenic analysis
L. Sautter	College of Charleston	Foraminiferan abundance
F. Prahl	Oregon State University	Alkenone concentrations
J. Dymond	Oregon State University	Barite

Table 2: Distribution of Sample Materials From Bottom-Moored Sediment Traps

Particulate carbon flux measurements from the ALOHA-I and II sediment traps is shown in Figure 65. Particulate carbon, as well as particulate nitrogen, phosphorus and mass, showed a major export pulse during the summer periods when the upper water column was well stratified. A second export pulse was also observed in late winter-early spring but this feature appears to be different than the summer peak. The major particulate matter export was recorded in the same collector cups regardless of depth suggesting a sinking rate of about 200 m d^-1. Analysis of chlorophyll a by fluorometry and HPLC pigment analyses reveal that the peak export event coincides with the removal of pigmented cells. The summer export material contains the full spectrum of major and accessory pigments. Microscopic analysis showed the dominance of diatoms during the summer export. A discussion of some of the findings has been presented in Karl et al. (1996a and 1997). Samples from ALOHA-III through XI are under analysis.