Showing papers on "Monterey Canyon published in 2019"

Linking Direct Measurements of Turbidity Currents to Submarine Canyon-Floor Deposits

Abstract: Submarine canyons are conduits for episodic and powerful sediment density flows (commonly called turbidity currents) that move globally significant amounts of terrestrial sediment and organic carbon into the deep sea, forming some of the largest sedimentary deposits on Earth. The only record available for most turbidity currents is the deposit they leave behind. Therefore, to understand turbidity current processes, we need to determine the degree to which these flows are represented by their deposits. However, linking flows and deposits is a major long-standing scientific challenge. There are few detailed measurements from submarine turbidity currents in action, and even fewer direct measurements that can be compared to resulting seabed deposits. Recently, an extensive array of moorings along Monterey Canyon, offshore California, took measurements and samples during sediment density flow events, providing the most comprehensive dataset to date of turbidity current flows and their deposits. Here, we use sediment trap samples, velocity measurements, and seafloor cores to document how sand is transported through a submarine canyon, and how the transported sediment is represented in seafloor deposits. Sediment trap samples from events contain primarily fine to medium-grained sand with sharp bases, normal grading, and muddy tops. Sediment captured from the water column during the flow shows normal grading, which is broadly consistent with the initial peak and waning of flow velocities measured at a single height within the flow, and may be enhanced by collapsing flows. Flow events contain coarser sand concentrated toward the seafloor and larger grain sizes on the seafloor or in the dense near-bed layer, possibly representative of stratified flows. Although flow velocity varies, sand grain sizes in sediment traps are similar over distances of 50 km down-canyon, suggesting that grain size is an unfaithful record of down-canyon changes in maximum flow speeds. Sand transported within flow events and sampled in sediment traps is similar to sand sampled from the seafloor shortly after the events, but traps do not contain pebbles and gravel common in seabed deposits. Seabed deposits thus appear to faithfully record the sand component that is transported in the water column during sub-annual turbidity currents.

Sediment and organic carbon transport and deposition driven by internal tides along Monterey Canyon, offshore California

Abstract: Submarine canyons are globally important conduits for sediment and organic carbon transport into the deep sea. Using a novel dataset from Monterey Canyon, offshore central California, that includes an extensive array of water column sampling devices, we address how fine-grained sediment and organic carbon are transported, mixed, fractionated, and buried along a submarine canyon. Anderson-type sediment traps were deployed 10 to 300 meters above the seafloor on a suite of moorings anchored between 278–1849 m water depths along the axial channel of Monterey Canyon during three consecutive 6-month deployments (2015–2017). Tidal currents within the canyon suspended and transported fine-grained sediment and organic carbon that were captured in sediment traps, which record the composition of sediment and organic carbon transport along the canyon. High sediment accumulation rates in traps increased up-canyon and near the seafloor, where fine-scale (

Life history of the deep-water persimmon eelpout (Eucryphycus californicus, family: Zoarcidae), and its use of drift vegetation as an ecological subsidy

Abstract: The Persimmon Eelpout (Eucryphycus californicus) is a relatively unknown, deep-sea fish inhabiting temperate marine waters on the west coast of North America. Using samples collected in the mid-1970s, the most recent targeted sampling for this species, we present basic life history attributes, and an analysis of the relationship between E. californicus and drift macrophyte habitat in the Monterey Canyon, California, USA. A diet analysis revealed that the fish consumes predominantly small crustaceans, especially amphipods and copepods, including species that associate with drift macrophyte habitat. Otoliths were analyzed to yield age estimates ranging from 0 to 6 years, and growth was modeled showing a maximum length of 203 mm for males and 271 mm for females. An analysis of the reproductive ecology of E. californicus showed that like many deep-sea fishes, females lay relatively few, large eggs. The species exhibits a protracted spawning period, and females spawn with only one functional ovary. Empirical information presented in this paper and anecdotal evidence shows that E. californicus likely relies on drift algae and seagrasses, a habitat subsidy exported to the deep-sea environment from adjacent kelp forest ecosystems, for shelter and to concentrate food resources. This example of a species dependent on an ecosystem subsidy adds to our knowledge regarding the effects of cross-ecosystem connectivity in the marine environment, and furthers our understanding of the ecology of the deep-sea macrofaunal assemblage in Monterey Bay.