» Home » HOT » Analytical Methods & Results

Bottom-Moored Sediment Traps

Bottom-moored traps


Analytical Method

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-XIV & ALOHA-XV moorings were deployed in June 2009 and recovered in September 2009. The present experiment consists of 2 sets of 2 Parflux MK7-21 sequencing sediment collectors locate at 4600 m. A separate sampling cup was rotated into the collector position on an approximately 15-20 day cycle, depending on the deployment period. Samples from each cup was initially divided into four 60-ml volumes (also refered to as splits). Each split was 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 - Aug 2008
ALOHA-XIV 22 51.7'N, 157 55.1'W 4,800 Jun 2009 - Sep 2009
ALOHA-XV 22 51.8'N, 157 53.3'W 4,800 Jun 2009 - Sep 2009

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



Results

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 XV are under analysis.