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Sanctuary Rocky
Intertidal Open
Ocean & Endangered
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MUSING on Monterey Bay Toxic algal blooms and dramatic fluctuations in fisheries demonstrate that living resources in our national marine sanctuaries are vulnerable to chemical and biological changes. In Monterey Bay and the waters of the California Current, wind-driven upwelling supplies the upper ocean with major nutrients such as nitrate and silicate. This nutrient supply, coupled with light, fuels the production of plankton -- the basis of our Sanctuary's biological riches. However iron, which is also required for plankton growth, is not abundant in upwelled water. Instead iron comes from seafloor sediments that are resuspended in the ocean during natural iron fertilization events caused by strong winds.
Monterey Bay Aquarium Research Institute (MBARI) plans for monitoring the chemistry and biology of the Monterey Bay National Marine Sanctuary include instruments at the sea surface and on the seafloor, as well as mobile units -- all contributing to long-term observations. The MBARI Upper-Water-Column Science Experiment (MUSE) was a step toward implementing these plans, with a study of the interrelationships between the physics, chemistry, and biology of coastal upwelling systems. MUSE embraced a range of science investigations, from natural iron enrichment to the biological and geochemical responses to upwelling, and culminated in a Monterey Bay field experiment in August 2000. The two-week MUSE experiment was designed to study natural iron fertilization. It invol-ved the use of moorings, autonomous underwater vehicles (AUVs), drifters, and underwater gliders, with the support of eight research ships. The weather cooperated nicely, with a series of small upwelling events followed by relaxation of the upwell-ing as the wind died. We traced the process with a number of novel tools: a towed, undulating vehicle with chemical sensors (the "Smart FISH"), two AUVs, and Navy and NASA aircraft. Scripps Institution of Oceanography and the University of Washington operated gliders and vehicles in the region, as well. After an initial survey of the region, MBARI instrumented drifters were deployed to track the ocean fronts that separate cold, upwelled water from warmer water masses. One drifter, released north of Davenport, moved south with upwelling-favorable winds, turned east into Monterey Bay, and then went north. After a week the drifter came nearly full circle, as we recovered it near Davenport. Another drifter was deployed further north, near Año Nuevo. Instrumentation on the drifters showed that they stayed with the cold pools of water in which they were deployed. Daily experiments were conducted in the cold water mass marked by the drifter and at control areas outside the cold mass. During the evenings we conducted surveys from Año Nuevo to Cypress Point to map iron, nitrate, and inorganic carbon concentrations and the subsurface physical structure.
In a tremendous advance for real-time measurements of plankton distributions, MBARI DNA probes revealed a major bloom of Pseudonitzschia australis, a toxic diatom. The distribution of this diatom was inversely related to iron concentrations, but it wasn't clear if the relationship was driven by iron abundance or simply a result of bloom formation. A series of ship-board experiments showed strong iron limitation in our coastal waters, which paralleled our field observations that the iron injected by upwelling is very rapidly lost, while other nutrients remain in the sunlit layers of the ocean. High concentrations of iron have been observed in the region between Año Nuevo and Davenport after upwelling-favorable winds. Data gathered with the Smart FISH show that the high iron concentrations occur in regions where upwelling is bringing deep waters up to the surface. These high iron concentrations disappear within a few days after winds relax.
Ken Johnson
Seamounts are volcanoes that rise up from the ocean floor. Their cascading slopes with outcropping cliffs, rocky fragmented bases, and sedimented valleys impinge on the mid-to-upper water column, modifying local current patterns. These factors result in highly-variable environmental conditions for life over the seamount, ranging from sediment-laden areas with few currents to exposed undersea ridgelines swept by strong currents with high densities of suspended material. Consequently, seamounts appear to support a high diversity of life both on their surfaces and in surrounding waters. Located 120 kilometers to the southwest of Monterey, the Davidson Seamount is forty kilometers long and rises 2,300 meters from the ocean floor, yet is still roughly 1,300 meters below the sea surface. This large geographic feature was the first to be characterized as a "seamount" and was named after George Davidson, a scientist at the Coast and Geodetic Survey -- the forerunner to the National Oceanic and Atmospheric Administration's (NOAA) National Ocean Service. In 1978-1979 the U.S. Geological Survey collected the first geological samples, and recent work on these same samples shows the seamount is about 12 million years old.
In May 2000 MBARI began describing biological communities on the crest and flanks of Davidson Seamount using a remotely-operated vehicle. The Monterey Bay National Marine Sanctuary collaborated in this exploration by performing bird and mammal surveys over the seamount during the cruise and compiling oceanographic data taken from MBARI's research vessel, Western Flyer. The Sanctuary has since conducted aerial surveys from the NOAA plane Shrike AeroCommander to enhance the mammal observation data sets. In addition to being geologically young and having a unique shape (most seamounts are circular) the Davidson Seamount has remarkable biological communities. Davidson has large, dense patches of sponges and apparently extremely old coral forests with individuals commonly reaching more than three meters in height (see photo above). Moreover, many invertebrate species collected during the cruise were previously unknown to scientists. Perhaps related to the rich life on the seamount, the waters above Davidson Seamount appear to be a productive feeding ground and -- as observed at nearby seamounts -- are frequented by sperm whales and albatross. Although samples from the recent exploration of Davidson Seamount have not been analyzed fully and new discoveries concerning Davidson Seamount and similar ocean habitats are expected upon further research, information from this year's sampling efforts have been recognized at the highest levels. On June 12, 2000 President Clinton directed NOAA to work in partnership with marine research institutions and universities to explore four unique sites in the United States, and Davidson Seamount is one of these sites of high research priority. New technologies are enabling detailed investigations of deep-sea
habitats, promising discovery of presently-unknown marine resources.
We are planning future expeditions to Davidson Seamount. Greater
knowledge of the biodiversity, community patterns, and function
of this area will improve our options for management of these
unique marine
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For comments or question please refer to the Webmaster Last modified on: Jan 15, 2000 |
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