Table of
Contents

Director's Report

Shorelines

Celebrating a Century

Hydrostation "S"

BATS

Cruise Diary

Oceanic Flux Program

Honor Roll
of Donors

OFP
Discovering changes in the deep
Dr. Maureen Conte describes the Oceanic Flux Program's studies of variability in the ocean's depths

Dr. Maureen Conte (left), head of the Oceanic Flux Program at Woods Hole Oceanographic Institution, deploys a deep-ocean sediment trap from BBSR's R/V Weatherbird II with the help of marine technician James Caison (right) and deckhand Patrick Hartery

In early 1978, a geochemist from Woods Hole Oceanographic Institution (WHOI) headed to the open ocean with exciting new equipment, a deep-ocean sediment trap. Dr. Werner Deuser deployed the funnel-like trap, designed to collect particles settling through the water column, near BBSR's Hydrostation "S" site. His plan was to measure the composition of settling particles 3,200 meters below the ocean's surface so he could better interpret ocean sediment composition in terms of past ocean conditions. Little did he realize that his study would evolve into the Oceanic Flux Program (OFP), one of oceanography's longest-running time series.

The OFP time series is unique in its focus on temporal variations in particle flux in the deep ocean. Scientists are keenly interested in particle flux because it controls the geochemical cycles of carbon and many other elements associated with biogenic material, the material produced by the ocean's living organisms. Sinking particles are also the major food source for animals living in the deep. The chemical composition of settling particles provides scientists with a wealth of information on particle sources and flux processes within the water column. This data allows us to more accurately interpret the ocean's sedimentary record and also to assess present day variability in upper-ocean functioning. Deep moored sediment traps are important sampling tools for long-term ocean observatories because they provide a continuous, albeit "edited," record of upper-ocean functioning integrated over tens of thousands of square kilometers.

Dr. Deuser chose Bermuda as an ideal location to study particle flux because the Sargasso Sea is characteristic of a large expanse of the North Atlantic. The long history of Bermuda research has provided invaluable information about the ocean environment. The establishment of other time series near the OFP site – the Bermuda Atlantic Time-series Study (BATS) in 1988 and the Bermuda Testbed Mooring (BTM) in 1994 – is currently providing an unparalleled opportunity to study the links between particle flux and the overlying surface water environment.

I took over the OFP in 1996, and every four months since then, I leave BBSR on the R/V Weatherbird II to recover and redeploy the OFP mooring. It now consists of four kilometers of wire and floats interspersed with traps at 500, 1,500 and 3,200-meter depths. A rotating sampling carousel allows sequential two-week collections. The material we recover consists of a few hundred milligrams of organic debris, zooplankton fecal pellets, minute shells of one-celled organisms, and inorganic particles. Back at WHOI, the samples are microscopically examined and analyzed for mass and chemical composition. My lab also conducts trace organic analyses of lipid "biomarker" compounds. Subsamples are sent to scientists worldwide for use in a diversity of research, and the remaining material is archived for future studies.

OFP findings have revolutionized our view of the ocean's interior. The OFP provided the first direct evidence that the deep-ocean environment was not constant, as widely believed, but was connected to seasonal variations in the overlying surface water. The OFP record has revealed flux variations on time scales ranging from a few days to more than a decade. Recently, collaborative studies with the BTM program and BATS have documented how physical and biological processes in the upper ocean may promote short-lived flux pulses of fresh biogenic material into the deep ocean. These pulses appear to be extremely important in determining the average penetration depths of nutrients and other elements in biogenic material.

Next year marks the 25th anniversary of the OFP time series. Analytical advances and the advent of satellites make possible investigations that were unfathomable in 1978. The OFP record has become long enough to begin to study how climate variation patterns affect particle flux. OFP research will continue to provide new insights into the controls on particle flux through the ocean's interior, which will be of paramount importance for predicting how ocean functioning will be affected by future, possibly human-induced, climate change.