Hydrodynamic sorting controls the transport and hampers source identification of terrigenous organic matter: a case study in East China Sea inner shelf and its implication

Transport of terrigenous organic matter (TerOM) in marginal seas plays an important role in marine carbon cycle which is closely related to global climate change. Suspended particulates in East China Sea (ECS) inner shelf are subject to strong influence of seasonally varied Zhe-Min Coastal Current (ZMCC) and Taiwan Warm Current (TWC). Transport of TerOM attached to the mineral particulates is therefore largely dependent on these hydrodynamic conditions. To address the transport pattern of TerOM in highly dynamic marginal seas and its implication, sediment samples were collected from ECS inner shelf and fractionated by water elutriation to simulate the hydrodynamic sorting process. Lignin phenols were determined for each fraction. The abundance of C phenols preferentially concentrated in the finer fractions, which is believed as a collective effect of hydrodynamic sorting, diagenetic reactivity and association preference of C phenols with finer sediments. In contrast to the expectation, sediments at the southernmost site did not have the highest mass percentage for the finest fraction, the lowest lignin abundance and the highest degradation status. Combining the results of lignin parameters with seawater temperature and salinity profiles, it is proposed that sediments are transported along the inner shelf southward in winter and northward in summer to some extent with the influence of seasonally varied ZMCC and TWC, induced by the seasonality of East Asia Monsoon (EAM). Finer grained sediments are more susceptible to this process. This transport pattern, which was only reported previously in ocean modeling, was firstly supported by the observation of lignin biomarkers. It is suggested that cross-shelf transport of sediments in ECS seems to be possible, but is complicated and is also affected by the seasonal variation of EAM. This study improved the understanding of hydrodynamic sorting on the transport of TerOM and carbon cycling in the marine system

Controls on the delivery of fluvial sediment to the coastal ocean: The Salinas River, California

To estimate delivery to the coastal ocean, a global river database was assembled. An estimated 35,000 km3 of freshwater, 4 * 10 6 tonnes of dissolved solids and 18.6 * 106 tonnes of suspended sediment are delivered annually. The global delivery of fluvial water and sediment, both suspended and dissolved, is dominated by Southeast Asia, due to the unique climatic, geologic and geomorphic character of the rivers in this region. Over 30% of the global freshwater and dissolved solid discharge, and an astounding 70% of the suspended sediment originate in this region. The Salinas River, central California, was the focus of an in-depth study on the controls on sediment delivery from a small, semi-arid watershed. This river discharges into the Monterey Bay an average of 0.4 km3 of water and 3.3 tonnes of sediment annually. Basin-scale control on the discharge of the river is dominated by the underlying geology as well as the anthropogenic changes to the watershed. Despite the altered nature of the Salinas River, the fluvial discharge is dominated by short-lived meteorological events. Large flood events on the Salinas River almost entirely correlate with El Nino events. However, not all El Nino years produce flood events. It was shown that the probability of a large flood on the Salinas River is determined not only by the presence of El Nino conditions, but also by the interaction between the Pacific Decadal Oscillation and the ENSO. The coinciding of warm phases of both of these large-scale phenomena produces significantly higher annual discharges than any other combination of the climatic phenomena. The Monterey Bay is bisected by a submarine canyon, restricting the shelf space and creating 2 separate sedimentary environments. The southern shelf bypasses most modern fluvial sediment to the canyon, whereas the northern shelf stores most of the sediment delivered. The estimate of Holocene sediment discharge from the rivers and creeks of the bay indicate that \u3e60% of fluvially delivered sediment is lost to the canyon and deep ocean. The transport pathways of this removal are currently unknown, but hyperpycnal flow from the mouth of the Salinas River is hypothesized

Fine-grained sedimentation on the Chenier Plain Coast and inner continental shelf, northern Gulf of Mexico

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2003This thesis examines the evolution of a mud-dominated coastal sedimentary system on multiple time scales. Fine-grained systems exhibit different properties and behavior from sandy coasts, and have received relatively little research attention to date. Evidence is presented for shoreline accretion under energetic conditions associated with storms and winter cold fronts. The identification of energetic events as agents of coastal accretion stands in contrast to the traditional assumption that low-energy conditions are required for deposition of fine-grained sediment. Mudflat accretion is proposed to depend upon the presence of an unconsolidated mud sea floor immediately offshore, proximity to a fluvial sediment source, onshore winds, which generate waves that resuspend sediment and advect it shoreward, and a low tidal range. This study constrains the present influence of the Atchafalaya River on stratigraphic evolution of the inner continental shelf in western Louisiana. Sedimentary and acoustic data are used to identify the western limit of the distal Atchafalaya prodelta and to estimate the proportion of Atchafalaya River sediment that accumulates on the inner shelf seaward of Louisiana's chenier plain coast. The results demonstrate a link between sedimentary facies distribution on the inner shelf and patterns of accretion and shoreline retreat on the chenier plain coast.Among my funding sources was a two-year fellowship from the Clare Booth Luce Foundation. I have received research grants from the Geological Society of America Foundation (Grant 6873-01) and the American Association of Petroleum Geologists (Kenneth H. Crandall Memorial grant)

Integrating space-and time-scales of sediment-transport for Poverty Bay, New Zealand

Poverty Bay is a small embayment located in the middle of the Waipaoa River Sedimentary Dispersal System (WSS) on the eastern coast of the north island of New Zealand. Within this dispersal system, a large multidisciplinary study was focused on determining the sediment routing from the source within the headwaters to the locations of sediment accumulation on the continental shelf and slope. Poverty Bay acts as the land to sea transition area in the WSS, and as such significantly modifies the fluvial sedimentary signal before it is exported to the continental shelf. Until this study, little hydrodynamic or sediment-transport work had been conducted in Poverty Bay, however. This dissertation analyzed observation and numerical model results to characterize the hydrodynamics and sediment-transport within Poverty Bay. Three S4 current meters with pressure and temperature/salinity sensors, one upward looking ADCP, and one downward looking ADV were deployed in Poverty Bay for April--September, 2006. Hydrodynamics, sediment-transport, and waves were modeled using the Regional Ocean Modeling System (ROMS) fully coupled to the Simulated WAves Nearshore (SWAN) model. The 2006 winter wet season was modeled to overlap with the field observations, along with a ∼40 yr recurrence interval storm that occurred from 21--23 October, 2005. For these two meteorological conditions, four different model grid and sediment load configurations were modeled; (1) the modern Poverty Bay with the modern sediment load, (2) the modern Poverty Bay with the pre-anthropogenic (PA) sediment load, (3) the 2 kya Poverty Bay with the PA sediment load, and (4) the 7 kya Poverty Bay with the PA sediment load. Both the observation and modeling results showed significant quantities of fine sediment were ephemerally deposited within the shallow Poverty Bay during times of elevated river discharge and energetic waves and currents. The deposition of sediment within Poverty Bay during floods followed by the resuspension and export to the continental shelf during subsequent wave events created multiple pulses of sediment out of Poverty Bay. as the sediment underwent multiple resuspension episodes, the sedimentary signal initially supplied by the river, such as the timing of supply to the shelf and the grain size distribution, would be altered. Shoreward nearshore currents and a divergence in the currents seaward of the Waipaoa River mouth provided mechanisms for the segregation of the sand from the muddy sediment, with the coarse sediment preferentially moved shoreward and the fine sediment exported from Poverty Bay to deeper water. Model results also showed significant differences between the sedimentary signals supplied to the continental shelf based on the dispersal basin geometry and river mouth orientation. The model estimates showed that marine dispersal can influence the long-term trends of a slowing shoreline progradation rate and coarsening upward sequences on the continental shelf, without invoking climate change or changes to the sediment supply. This implies that the processes controlling marine and nearshore sediment dispersal must be considered when developing hypothesis based on sedimentological observations

Virginia Institute of Marine Science 1988-90 Biennial Report

https://scholarworks.wm.edu/vimsannualrpt/1025/thumbnail.jp

Abstracts of papers submitted in 1987 for publication

This volume contains all abstracts submitted for publication during calendar year 1987 by the staff and students of the Woods Hole Oceanographic Institution. Because some of the abstracts may not be published in the journal to which they have been submitted initially, we have purposely omitted identifying the journals. The volume is intended to be informative, but not a bibliography

Goods and Services of Marine Bivalves

The aim of this book is to review and analyse the goods and services of bivalve shellfish. How they are defined, what determines the ecological functions that are the basis for the goods and services, what controversies in the use of goods and services exist, and what is needed for sustainable exploitation of bivalves from the perspective of the various stakeholders. The book is focused on the goods and services, and not on impacts of shellfish aquaculture on the benthic environment, or on threats like biotoxins; neither is it a shellfish culture handbook although it can be used in evaluating shellfish culture. The reviews and analysis are based on case studies that exemplify the concept, and show the strengths and weaknesses of the current applications. The multi-authored reviews cover ecological, economic and social aspects of bivalve goods and services. The book provides new insights for scientists, students, shellfish producers, policy advisors, nature conservationists and decision makers. This book is open access under the CC BY license.publishedVersio

ITALY-CHINA: AN ANCIENT CULTURAL HERITAGE AND THE CHALLENGE FOR FUTURE DEVELOPMENT

Scegliere gli argomenti di interesse attinenti al corso di Sociologia dello Svilupp