Sediment Trap Methodology

CARIACO sediment trap mooring

13 February 2008: Prepared for OCB data system by Terry McKee (BCO-DMO) from documentation contributed by Laura Lorenzoni (IMaRS, USF).

To measure settling particle flux at the CARIACO time-series site, five automated sediment traps were placed at 150, 225, 410, 810, and 1210 m on a mooring. These funnel-shaped traps are synchronized to collect samples over 2 week periods into a series of jars. The traps are retrieved and re-deployed every 6 months (May and November), and samples are collected to estimate carbonate, organic carbon, nitrogen, and biogenic silica fluxes and various other geochemical parameters.

This sediment trap dataset includes all sediment trap flux records collected during the CARIACO Time-Series project to date.

May 1996 - October 1996 is not available due to clogging of all 4 traps
May 2001- November 2001 is not available due to clogging of all 4 traps

Sediment trap mooring description

A mooring with five automated sediment traps (Z, A-D) is located in the eastern Cariaco Basin (10°30'N; 64°40'W). (the original full sized diagram is available as a PDF file). Traps A-D have been in place since November 1995. Trap A is located in oxic waters at 226±6 m. Trap B-D are in the anoxic portion at 407 ± 3 m, 807±2 m and 1205 ± 3 m, respectively (Benitez-Nelson et al., 2007). The fifth trap, Z, was added in November 2003 and currently resides at 150 ± 2 m. All five sediment traps are funnel-shaped with a 0.5 m² opening that is covered with a baffle top to reduce turbulence. The mooring is deployed for six-month intervals (retrieved and re-deployed about every 6 months in May and November) and each sample collection cup is filled with a buffered 3.2% formalin solution as a preservative for the accumulating organic matter (settling particles). The cups rotate every two weeks and are numbered 1-13, with cup 1 collecting for the two-week interval immediately following deployment, and cup 13 collecting for the 2 weeks immediately before recovery (Thunell et al., 1999; Müller-Karger et al., 2000; Thunell et al., 2000; Müller-Karger et al., 2001; Taylor et al., 2001; Goñi et al., 2003; Benitez-Nelson et al., 2007; Thunell et al., 2007).

Benitez-Nelson, C. R., L. O. Madden, R. M. Styles, R. C. Thunell, and Y. Astor (2007) Inorganic and organic sinking particulate phosphorus fluxes across the oxic/anoxic water column of Cariaco Basin, Venezuela, Marine Chemistry, 105, 90-100.

Goñi, M., Aceves, H., Thunell, R., Tappa, E. and Black, D. 2003. Biogenic fluxes in the Cariaco Basin: A combined study of sinking particulates and underlying sediments, Deep-Sea Research 50, 781-807.

Müller-Karger, F., R. Varela, R. Thunell, M. Scranton, R. Bohrer, G. Taylor, J. Capelo, Y. Astor, E. Tappa, T.-Y. Ho, M. Iabichella, J. J. Walsh, and J. R. Diaz, "The CARIACO Project: Understanding the Link between the Ocean Surface and the Sinking Flux of Particulate Carbon in the Cariaco Basin", EOS. AGU Transactions, vol. 81:45, (2000), p. 529.

Müller-Karger, F. E. R. Varela, R. Thunell, M. Scranton, R. Bohrer, G. Taylor, J. Capelo, Y. Astor, E. Tappa, T. Y. Ho, and J. J. Walsh, "Annual Cycle of Primary Production in the Cariaco Basin: Response to upwelling and implications for vertical export", Journal of Geophysical Research, vol. 106:C3, (2001), p. 4527.

Taylor, G., Scranton, M., Iabichella, M., Ho, T., Thunell, R., Varela, R., and Müller-Karger, "Chemoautotrophy in the redox transition zone of the Cariaco Basin: A significant source of mid-water organic carbon production", Limnology and Oceanography, vol. 46:1, (2001), p. 148.

Thunell, R., E. Tappa, R. Varela, M. Llano, Y. Astor, F. Müller-Karger, and R.Bohrer., "Increased marine sediment suspension fluxes following an earthquake", Nature, vol. 398, (1999), p. 233.

Thunell, R., R. Varela, M. Llano, J. Collister, F. Müller-Karger, and R. Bohrer, "Organic carbon fluxes and regeneration rates in an anoxic water column: Sediment trap results from the Cariaco Basin", Limnology and Oceanography, vol. 45, (2000), p. 300.

Sediment trap sampling and analytical protocols

Sediment trap samples are sealed and refrigerated immediately after collection. Processing is usually carried out within 1-3 weeks after recovery. The supernatant and any swimmers are discarded and whole traps samples are split using a precision rotary splitter. A quarter of each sample is used for bulk geochemical analyses. Particulate organic carbon (POC) and particulate nitrogen (PN) analyses are conducted according to the methods described in Thunell et al. (2000), using a Perkin Elmer 2400 elemental analyzer.

Sediment_Trap.csv