Northward wind stress, common in spring and 

 summer, spreads the coastal front seaward; southward 

 stress, common in the autumn and winter, confines the 

 front to a narrow band along the coast. Under the 

 latter conditions, material may be advected to Cape 

 Canaveral and subsequently deflected into the Gulf 

 Stream. 



This knowledge base on SAB particle dynamics 

 is the beginning of a general conceptual model that ul- 

 timately will provide DOE with a predictive capability 

 for quantitatively assessing SAB's capacity for as- 

 similating energy-related by-products. This informa- 

 tion will enable decisionmakers to maintain the 

 delicate marine ecological balance while continuing to 

 satisfy national energy requirements. 



Southwest: California Basins Study 

 Statement of Problem 



The geologic and oceanographic setting of the 

 West Coast margin is different from that of the East 

 Coast because it is a zone of crustal plate collision, 

 whereas the East Coast is a more passive zone with less 

 tectonic activity. The West Coast area, frequently 

 referred to as the California Bight, offers some impor- 

 tant advantages for determining the fate of injected 

 pollutants. The region has a network of deep-sea 

 basins close to shore. (See figure 4 for a schematic 

 showing the deep basins adjacent to the coast and the 

 ocean currents flowing through them.) These basins 

 act as extremely efficient traps for coastal sediment. 

 The deep waters in many of the basins are nearly free 

 of oxygen; sediment records consequently are well 

 preserved. Water circulation is restricted by the walls 

 and sills which define basin boundaries, by adjacent 

 land masses, and by reduced local wind effects due to 

 coastal mountain topography. General circulation is 

 restricted by an eastern (rather than a western) bound- 

 ary current. 



These characteristics also affect biological en- 

 vironments, in that colder waters move south along 

 California and coastal upwelling is a major process. In 

 contrast, on the East Coast, warm waters move 

 poleward and current mixing recharges surface water 

 nutrient budgets. 



Sediment particles enter the coastal zone from 

 river input, major waste discharges, biological produc- 

 tion in the water column, and atmospheric infall. River 

 discharge enters the margin from the northern sector 

 rivers. Sediment contribution is seasonal; it also can be 

 influenced by longer climatic cycles. Over the past cen- 



tury, more than half of the sediment contribution has 

 come in four or five major flood events at roughly 20- 

 year intervals. On a long-term average, land-derived 

 sediment from the rivers constitutes approximately 80 

 percent of the total California borderland particulate 

 budget. 



CaBS' objectives are: 



• To quantify the production, transformation, 

 and flux of organic matter and energy-re- 

 lated byproducts within the Santa Monica- 

 San Pedro Basins 



• To evaluate the current patterns and water 

 movements which transport particles and 

 dissolved materials within the Basin and 

 resuspend and transport particles from the 

 Basin margins and bottom 



• To measure terrestrial particulate and dis- 

 solved inputs to the Basin 



• To measure net accumulation and burial 

 rates of sediment and sediment-associated 

 radionuclides, organics, and elements 



• To develop models of the dynamics of or- 

 ganic matter in the Santa Monica-San Pedro 

 Basins. 



Program Description 



The California Basins Study is a coordinated, 

 multidisciplinary effort to examine and understand the 

 production, transport, and ultimate fate of biogenic 

 particulates and energy-related products associated 

 with them in the nearshore ocean basins off Southern 

 California. 



Particle sources include anthropogenic and 

 other terrestrial inputs as well as planktonic growth. 

 The CaBS program has emphasized understanding 

 planktonic cycling in the near-surface euphotic zone, 

 vertical particle fluxes, and benthic metabolism and 

 burial rates. 



This study has used the closed nature of the 

 Santa Monica-San Pedro Basin off Los Angeles as a 

 convenient regional feature which constrains the 

 movement of near-bottom particulate material, there- 

 by allowing budgets in a closed-basin system to be 

 determined (figure 4). One strength of this program is 

 the comparison of methods used to measure the 

 various particle-associated processes. Results are 



Coastal Ocean Margins Program 



14 



December 1988 



