Grantee Research Project Results
Final Report: Integrated Urban Watershed Analysis: The Los Angeles Basin and Coastal Environment
EPA Grant Number: R825381Title: Integrated Urban Watershed Analysis: The Los Angeles Basin and Coastal Environment
Investigators: Turco, Richard , Friedlander, Sheldon , Berk, Richard , Ambrose, Richard , Fong, Peggy , Dracup, John A. , Feddema, Johannes , Forrester, Graham E , Fovell, Robert G , MacDonald, Glen , McWilliams, James , Orme, Antony , Raphael, Marilyn , Stenstrom, Michael , Stolzenbach, Keith , Suffett, Irwin , Vance, Richard , Venkatesan, M. Indira , Walter, Hartmut , Trimble, Stanley , Hamner, William M
Institution: University of California - Los Angeles
EPA Project Officer: Packard, Benjamin H
Project Period: December 1, 1996 through November 30, 1999 (Extended to November 30, 2000)
Project Amount: $1,200,000
RFA: Water and Watersheds Research (1996) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
The objective of the University of California-Los Angeles (UCLA) Los Angeles Watershed project was to delineate the processes that control water availability and quality in a major urbanized region; the Santa Monica Bay (SMB) and its watersheds along the coastal zone of the Los Angeles Basin (LAB), in Southern California. The overall methodology was based on the coupling of data and models that bear on a wide range of factors influencing regional water resources, including: synoptic meteorology and climatology; basin hydrology, vegetation and land use; water consumption and disposition; runoff sources of sediments, toxics and nutrients; air pollutant transport, transformation and surface deposition; downstream wetlands ecology; coastal water circulation, biogeochemistry, and sediments. The three spatial scales used for the watershed problem are illustrated in Figure 1. The largest scale (I) encompasses the entire region, and is appropriate for mesoscale meteorological and coastal ocean modeling. On a more local scale (II), a major receptor such as SMB is associated with numerous watersheds. This scale assesses the factors controlling coastal water quality. Finally, on the individual watershed/wetland scale (III), investigations of pollutant runoff and wetland ecosystems are relevant. The various aspects of the watershed problem have been addressed by members of the interdisciplinary science team assembled through UCLA's Institute of the Environment. The effort focused on the development of a detailed understanding of key components of the problem and a broad synthesis of these components using models and data analysis.
Figure 1. Regional watershed areas and scales of resolution for research projects and assessments.
The component analysis has been divided into four primary areas: (1) air and atmospheric processes (mainly at scale III); (2) land and hydrological processes (scale I); (3) wetlands and ecological processes (scale I); and (4) marine and coastal ocean processes (scales II and III). The observational database for the project includes in situ measurements, remotely sensed data, and local geographical information, all of which is processed using Geographical Information System (GIS) techniques. The basic processes for each component are represented by advanced models, which simulate material flow, deposition, transformation, and bioassimilation. The models can be linked by generating sophisticated data sets for analysis and interpretation. The integrating objective of the Watershed project is a multidisciplinary assessment of pollutant mass budgets in SMB, a primary coastal reservoir along the Los Angeles (L.A.) coastline. This assessment accounts for sources of trace pollutants deposited directly from the air, in runoff from land, and through outflows of wastewater.
Research Components. The four principal research components of the L.A. Watershed project are: Air, Land, Wetlands, and Coastal Ocean. Each of these components is interdisciplinary in nature. The four components are linked in a number of ways, as summarized in terms of scientific relationships in Table 1 (also refer to Figure 3).
In Table 1, each column represents a major watershed component, while each row identifies the information it contributes to the other components. The diagonal entries define the primary research elements of the four project components. Integration is achieved through the implementation of the various linkages, indicated by the off-diagonal items.
Integration of Components-Focus on SMB. The four components of the L.A. Watershed project were further integrated in an assessment of pollutant budgets in SMB. This effort has incorporated results from nearly all Watershed research elements described in this report. Figure 2 illustrates the key factors in the present analysis, ranging from streamflow associated with climatological precipitation to transport and dispersion from SMB via the California Current. The bay represents a massive reservoir for pollutants (with several sub-reservoirs consisting of the surface layers, bulk waters, and sediments). The inputs and sinks for pollutants in each reservoir were addressed by the Watershed analysis. The Malibu and Ballona watershed drainages represent major sources of materials for the bay; both have been extensively characterized by project scientists for the first time in a comprehensive manner. The coastal ocean circulation and internal eddy dispersion within SMB has not previously been modeled in such detail, and the present report offers the first important results in this regard.
COMPONENT (client) | AIR | LAND | WETLANDS | COASTAL OCEAN |
Air | Winds and precipitation (e.g., Santa Ana winds); Material transport, transformation, and removal. | Topography and land use (roughness, moisture); Particle and gas sources; Urban emissions. | Tracer vapor fluxes generated by biological activity. | Coastal winds; Sea surface temperature; Marine aerosol and sulfur emissions. |
Land | Precipitation rates/patterns; Extreme events; Climatology of drought. | Watershed hydrologic and land use characterization; Runoff fluxes and inventories; Malibu and Ballona Creek cases. | Beach sediment sources. | Influence on climatology (El Niño, La Niña); Coastal erosion and sediment movement. |
Wetlands | Air deposition sources of nutrients, toxics, and other material; Direct and watershed deposition. | Streamflow extremes; Sources of nutrients and toxics; Sediment flows. | Malibu/Ballona/Mugu/Newport Bay plant/animal studies; Ecosystem/pollutant relations. | Tidal forcing and flushing; Impact on drought cycles and implications for estuaries. |
Coastal Ocean | Airborne deposition on coastal waters and watersheds; Wind driven currents. | Urban runoff (SMB); Sewage outflow, and dumping; Sediment sources. | SMB pollutant filter and source; Biotic fluxes and debris. | Coastal ocean circulation; Marine ecosystems; Pollutant dispersion/removal; SMB mass budgets. |
Figure 2. Schematic diagram indicating the elements of a mass balance analysis for SMB. Shown are sources and sinks of materials (soluble chemicals and particulates) for SMB addressed in the L.A. Watershed Project. Input comes from the surrounding watershed runoff, sewage outfalls, air deposition, and transport from adjacent waters. Losses occur by sedimentation, mixing, and dispersion into coastal currents. Sources tend to be sporadic, while sinks are more continuous, resulting in major pollution "events" and biological "blooms."
Air. The air component of the project considered atmospheric processes that significantly influence the coupled system of land, wetlands, coastal ocean, and the flow of water and pollutants. Specific topics treated under the project include: regional meteorology and precipitation, climatology and drought, and airborne pollutant transport and deposition. The meteorological setting for the L.A. Watershed system determines the timing and rates of water flow through coastal drainages. Observed and simulated precipitation patterns were generated to support the land runoff component of the SMB pollution assessment. Moreover, to provide a regional view of historical variations in precipitation, the climatology of the LAB was characterized using tree ring samples. This analysis revealed drought frequency in connection with climate change in the Pacific Ocean Basin. Field and laboratory research also was conducted to quantify the properties of airborne particles that affect surface water composition along the coast of L.A. through deposition. Finally, meteorological and aerosol data were incorporated into a regional air quality model to determine the deposition rates of various pollutants onto coastal waters and watersheds in the LAB, with an emphasis on SMB.
Figure 3. Interconnections Between the Major Components of the Santa Monica Bay Watershed Project. The connections on the left of the chart indicate intra-connectivity within components, and those to the right of the chart show the interconnectivity between components.
Regional Meteorology: The LAB. A mesoscale dynamics model (the MM5 code) was used to study rainfall events in the LAB. The simulations provided information on the distribution of precipitation among the major watershed in the region, as well as providing detailed rainfall data for hydrologic simulations. Calculated precipitation rates and amounts were compared to corresponding rain gauge data, while simulated runoff was contrasted against recorded streamflow data. The most detailed work, involving a coupled meteorological/hydrological analysis, focused on the Malibu Lagoon Watershed (as described under the Land component below). The ability of the MM5 to produce realistic regional meteorological forecasts (winds, temperatures, pressures, and precipitation) in the L.A. area was tested first. Case studies were conducted both with and without data assimilation, using Four Dimensional Data Assimilation (FDDA) only to optimize the fidelity of the predictions. FDDA marginally increased the accuracy of the forecasts. Following these validation studies, simulated MM5 precipitation rates and patterns were coupled to a hydrological code adopted for the Watershed project. In a particular case of an intense rain event (February 7-8, 1993), calculated and measured precipitation was consistent, and generated hydrographs compared favorably with observations. These and other results obtained during the project indicated that properly constrained meteorological simulations can be employed to reproduce streamflow variations more accurately than those based solely on rain gauge data (owing to the limited spatial coverage and localized nature of the gauges).
In addition to linking the meteorological and hydrological analyses, the meteorology was coupled to the pollutant dispersion and deposition model. The integrated air quality and meteorology simulations, which encompass the entire LAB, are carried out first to support a watershed assessment in the Southern California area.
Regional Climatology: Southern California. To extend the L.A. Watershed analysis to longer time scales, records of natural precipitation and drought variability within the L.A. area were reconstructed over a period of more than 1,000 years using tree ring measurements. The feasibility of deducing the corresponding historical streamflow in major regional river systems also was assessed. Using these data, the regional climate record was fully reconstructed. This record is useful for estimating potential extremes in precipitation (high and low) and corresponding streamflow to the coastal zones. Periods of drought with low frequency are of crucial importance for water resource planning in the region. Furthermore, the present transport and deposition of pollutants into SMB can be scaled against extreme events in the climatic record to define the range of natural variability in this key atmospheric forcing of the watershed system.
During the Watershed project, tree rings were sampled and analyzed at 10 sites, each site having trees old enough to date 600 years or more. This data has been analyzed, cross-dated, and archived for further use. Statistically verifiable time-series of winter precipitation of over approximately the last 1,000 years and Palmer Drought Severity Index (PDSI) were derived from the data for the LAB. We find that very severe droughts, with precipitation at least two standard deviations below the mean for the period 1895-2000, have occurred at least 14 times in the past 600 years. Droughts in which precipitation was at least one standard deviation below the 1895-2000 mean have occurred over 100 times during the period studied.
Time-series analysis of drought frequency and correlations with external forcing factors indicates that only about 30 percent of the variability in L.A. precipitation can be attributed to El Niño and La Niña events. The decadal-scale variations in dry and wet periods correlate with the Pacific Decadal Oscillation (PDO), which represents a cycle of warming and cooling of sea surface temperatures off the Pacific Coast of North America. Based on this new data, the relationship between annual or monthly streamflow and tree ring width is statistically insignificant.
Airborne Particulates: An SMB Case Study. A field study was conducted to define the composition and microphysical properties of aerosols (suspended fine particles) over SMB and its watersheds. The detailed aerosol data was employed to calibrate a comprehensive model for airborne particulates (see the following section) and to estimate the contribution of aerosol dry deposition to the surface water chemistry of SMB. Samples of air and the underlying surface microlayer (SMIC), as well as bulk water below the SMIC, were obtained along several transects of the bay. Size-resolved aerosol samples were analyzed for trace metal composition, and a source apportionment analysis was conducted to confirm the likely origins of the metals. The experimental design called for identical analytical chemical techniques to be applied to samples from all three media (air, SMIC, and water column), in order that relative tracer abundances in each medium could be intercompared more accurately. Both inland and marine aerosols were monitored to identify gradients across the land-sea transition. The study included a diurnal characterization of the aerosol concentrations and fluxes to the bay.
A field campaign was carried out on SMB in April 1998, and additional aerosol data from a nearby inland site (maintained by the Southern California Air Quality Management District) was analyzed to define gradients between the two environments. The data was analyzed for up to 28 trace metals (although only about half that number were reliably detectable). That May, diurnal monitoring of the marine aerosol using the same instrumentation was conducted. Analysis of the data revealed that the concentrations of certain tracers in the SMIC (Mn, Fe, Cr) are greatest during the morning hours (2-10 a.m.). This enhancement correlated with measured variations in the chemical composition of particles smaller than about 0.67 microns (i.e., the ultrafine fraction). Estimates of trace metal dry deposition rates to surface waters suggest that a number of metals (e.g., Zn, Ni) in the SMIC will be controlled by atmospheric sources.
Air Pollutant Transport and Deposition: L.A. Watersheds. To support the SMB, surface microlayer composition studies and the overall SMB mass balance assessment, detailed aerosol simulations were completed using the Surface Meteorology and Ozone Generation (SMOG) model. The pollution deposition associated with the most common weather conditions affecting the LAB were investigated. The meteorological predictions from the MM5 defined the regional synoptic conditions for these studies. Hence, the air pollution transport and deposition calculations were constrained with respect to dynamical variables. The SMOG model detailed the chemical and microphysical processes relevant to aerosol formation, growth, and dry deposition over the entire L.A. area, including SMB. This three-dimensional view has shown how elevated pollutant layers can form over the LAB, leading to pollutant deposition on inland headwaters, and the pathways by which urban pollutants are dispersed over areas well beyond the LAB.
SMOG simulations were used to quantify the influence of weather on the deposition of trace metals over SMB. Regional chemical/aerosol simulations are useful when making estimates of the potential material inputs from extended land sources to SMB and other coastal receptors. The predicted patterns, rates, and variations in pollutant mass deposition-both directly onto water basins, as well as on their watersheds-delineate a key component of the overall watershed mass balance.
Land. The overall land component of the L.A. Watershed project sought to develop predictive models representing the physical, hydrological, and runoff characteristics of the watersheds that feed the coastal waters of Southern California. In particular, the land component focused on watersheds and runoff affecting SMB. With more than 30 to choose from, the land/hydrology/runoff team selected two of the major watersheds associated with SMB: Malibu Creek and Ballona Creek. The Malibu Creek Watershed is impacted by development in its lower and upper reaches, but also encompasses large tracts of relatively pristine national park land. On the other hand, the Ballona Creek watershed drains most of western L.A., and is heavily developed (more than 60 percent impervious) and channelized. These two watersheds account for the majority of particulates and toxic pollutants entering SMB.
Malibu Creek Watershed Assessment. The analysis of the Malibu Creek Watershed, a major feeder stream for SMB, employed a version of the well known TOPMODEL. The Malibu Creek Watershed was characterized using detailed information on elevation, land use, vegetation type, and soil properties collected from regional agencies. These hydrologic data were assessed for accuracy prior to modeling. Other information was compiled to calibrate and validate model predictions, including streamflow measurements and corresponding precipitation records. A number of validation runs were performed for Malibu Creek using recent rain gauge and streamflow measurements. Parallel with this initial hydrological modeling, a historical frequency analysis was performed on the streamflow and precipitation data for the Malibu Creek area. The hydrologic model was run using historical rain data, and was coupled to a regional meteorological model. To drive the TOPMODEL, the MM5 was run in a high-resolution temporal and spatial mode. Hydrologic and coupled model predictions were compared against statistical behavior to assess the accuracy of such forecasting.
The results of the hydrologic/precipitation modeling work indicate that there is potential for conducting reasonable simulations by incorporating mesoscale precipitation forecasts into a comprehensive hydrologic model. Noteworthy results include:
· The use of precipitation rates and distributions from a mesoscale model has the advantages of augmenting data from local precipitation stations, which are typically few in number even in large watersheds, and of allowing self consistent, fully coupled predictions of streamflow and runoff.
· The hydrologic model (TOPMODEL) does not always capture the time of peak runoff, even with the use of measured precipitation, although the predicted magnitude of the peak runoff is quite accurate.
· On a 24-hour time scale, the mesoscale model is effective in simulating total event rainfall, whereas the timing of the rainfall is less resolved.
· Overall, a generalized calibrated hydrologic model is invaluable for forecasting flood potential, evaluating the impacts of changes in land use and vegetation on runoff, and tracing the flow of contaminants through a watershed.
In the last phase of the project, several dynamic river models were investigated for their ability to predict time-dependent flow within the L.A. River system. Both the Dynamic Wave Operational Model (DWOPER) and Flood Wave Model (FLDWAV) were considered, because each allows fundamental transient flow studies to be performed, and each is readily coupled to a mesoscale meteorological model such as the MM5, as well as to a surface hydrological code such as TOPMODEL. Stream gauge and engineering data were collected for the purpose of testing the DWOPER code along an upstream run of the L.A. River.
SMB Runoff Analysis. The runoff element of the L.A. Watershed project compiled extensive data on the pollutants affecting wetland and coastal waters, and the absolute quantities of materials transferred by the major streams feeding SMB. The runoff sources of a wide variety of substances-from lead and other metals, to nutrients, to polycyclic aromatic hydrocarbons (PAHs)-were calibrated within the framework of a detailed GIS-based land runoff code, which has been calibrated using stream measurements in both dry and wet periods.
An effort was made to couple the GIS land-use and source database with a more realistic runoff model: the U.S. Environmental Protection Agency (EPA) Storm Water Management Model (SWMM). SWMM includes stream and drain hydraulics, and is more predictive than the GIS-based model alone. A calibrated version of the coupled SWMM/GIS model was constructed during the Watershed project. To manage the workload, the study area was reduced from the entire SMB Watershed to the Ballona Creek Watershed. However, the resulting methodology is general and applicable to all of the watersheds in Southern California. Moreover, the integration of a sophisticated non-point runoff source model with a GIS system offers a powerful new tool for developing control strategies to improve water quality within local drainages.
Given the variability in storm events, widely varying flow patterns were observed at Ballona Creek during the field measurements. The outflow from the creek also is strongly influenced by tidal action, and transport of pollutants to SMB occurs primarily during low tide cycles. Suspended solids carry the primary load of organic chemicals and toxic metals to the bay. PAHs were the main pollutants detected in the suspended phase in the storm drains sampled.
The highest concentrations of trace organics are contained in the first upstream flushing of Ballona Creek. Of the 17 target PAHs, pyrene was consistently detected in the greatest concentrations. Benzo(a)pyrene, benzo(k)fluoranthene, chrysene, fluoranthene, and phenanthrene also were present in significant quantities. In general, the PAHs in suspended solids exceeded their Effective Range Median (ERM) value for sediment toxicity (representing the point above which adverse ecological effects are expected). The measured concentrations also surpassed the proposed limits defined in the California Ocean Plan designed to protect human health, welfare, and the coastal environment.
In the samples taken, aqueous phase metal concentrations were generally 100 times lower than concentrations in the solid phase (the latter of which were in the range of milligrams of pollutant per liter of water sampled). The concentrations of eight regulated metals (Ag, As, Cd, Cu, Cr, Ni, Pb, Zn) in the suspended sediment load usually exceeded the Effective Range Low (ERL) value for sediment toxicity (above which ecological effects are expected), with some concentrations lying above the ERM value, where significant ecological effects occur.
Lead is most frequently detected at the highest concentrations in runoff from Ballona Creek. Lead concentrations were always greater than the ERM. While the study showed that this outflow is a significant non-point source of lead pollution, the receiving waters inside of the Marina del Rey breakwater are already highly contaminated with lead, most likely originating in the adjacent marina, where sediment lead concentrations are as high as 3,000-35,000 mg (on solids) per liter of water. The total estimated lead mass output from Ballona Creek was 30 kg (in a January 1997 storm) and 900 kg (in a March 1997 event). These quantities are equivalent to up to 6 months of discharge from a major oil refinery.
SMB Water Quality. Metals, nutrients, PAHs, and other pollutants that flow into SMB were sampled directly in receptor waters as part of the integrated watershed analysis. In one phase of the study, measurements of chemical runoff were coordinated with air and surface microlayer data taken simultaneously. In addition to determining the relative sources of trace metals for the microlayer, another objective was to track the outward flow of contaminants from Ballona Creek into SMB. Sampling transects were completed from January 25-27, 1997, from the mouth of Ballona Creek into the bay, from a vessel maintained by the University of Southern California. Samples of suspended solids were collected during these 3 days at three distinct sites: the mouth of Ballona Creek, the near-littoral zone, and offshore. The solids, which carry much of the trace contamination into SMB, were separated from the water column prior to analysis.
The recorded composition of the suspended solids indicated that the majority of polychlorinated biphenyls (PCBs), PAHs, phthalates, and metals detected in the ocean water column adjacent to the Ballona outflow originate at the mouth of the creek (but could receive a major contribution from the marina).
Runoff mass fluxes deduced by the land runoff team were compared to predictions of air deposition rates determined under the air quality component of the project. Moreover, possible airborne contributions to runoff into SMB also were estimated for the first time using new calculations of aerosol pollutant deposition over land. For certain metals, such as zinc, air deposition dominates the runoff mass flux.
Terrestrial Biodiversity: The Western LAB. As an element of the L.A. Watershed project, a survey was made of the biodiversity of the western LAB. The area of interest is adjacent to SMB and channels runoff into coastal waters. Here, fully developed tracts, along with substantial areas are less impacted, owing to steep or unstable terrain that is difficult to develop or that presents other hazards such as fire and flood. In the major Ballona Watershed, the native flora and fauna have been displaced by extensive development. In the Malibu Watershed, by contrast, the land is dominated by steep terrain, canyons, and ridges hosting many native species in sustainable populations. Nevertheless, subdivisions, roadways, and parks degrade the land, water quality, and biodiversity throughout the watershed.
There is a strong contrast in the composition and structure of vegetation between irrigated and non-irrigated landscapes in the western LAB. Imported irrigation water supports the majority of urban vegetation, including home gardens and lawns, parklands, street arbors, and a wide variety of ornamental plants. The imported water taken up by such vegetative cover contributes substantially to the land evapotranspiration budget throughout the year. Transpired water can influence the microclimates in urban neighborhoods and affect the stability and mixing height of the boundary layer, which in turn can impact air quality.
Similarly, the urban fauna is highly impoverished due to widespread use of pesticides and herbicides, with associated impacts of exotic vegetation, vehicular attrition, and pest control measures. Adaptable species such as raccoon, opossum, coyote, eastern gray squirrel, and red fox are still found in many neighborhoods, particularly along urban boundaries with islands of native vegetation. Cowbirds, house sparrows, several parrot species, and starlings are common and abundant urban avian invaders. Species more reliant on native habitat and larger domains are in a more precarious state; these include deer, bobcat, mountain lion, and some raptors.
Pockets of remnant, non-irrigated coastal sage and riparian habitats still contain substantial elements of historical flora and fauna. The native vegetation of the coastal slopes and the L.A. plain is well adapted to the highly seasonal nature of regional rainfall and periodic drought. However, extensive channeling of waterways and surface paving has reduced the opportunity for storm waters to spread over, infiltrate, and thus continue to hydrate the once extensive flood plains of the region. Frequent flood episodes in the 19th century had maintained large wetlands along the coast and in the cienegas (marshes) of Beverly Hills, north of the Baldwin Hills. Long ago, these areas were drained and isolated from seasonal inundation. The implications for runoff from watersheds such as Ballona Creek are profound.
GIS Integration. The development of GIS applications for integrated watershed assessment was realized at the most fundamental level in the context of the land component of the L.A. Watershed project. For example, GIS-based land-use, hydrology, and runoff models were employed in the SMB pollution study. During the course of the research, a new GIS laboratory was established at UCLA. The resulting GIS facility consists of three laboratories located in the Departments of Geography and Atmospheric Sciences. Together, the laboratories constitute the Institute of the Environment's Regional Environmental Assessment Laboratory (REAL) and GIS (REAL/GIS). One area houses an advanced GIS/Remote Sensing facility, where watershed databases are archived, and the Watershed project Web Site is maintained. High-performance computing resources are located at a second location, and are available to the Watershed modelers and data analysts. The REAL/GIS facility offers access to watershed and related information for project researchers and students. Eventually, access will be expanded to the entire university community and to the public over the Internet.
Wetlands. The L.A. Watershed Project wetlands component examined the fate, transport, and ecosystem effects of anthropogenically produced chemical substances in certain important watersheds along the Southern California coast. The objective was to determine how pollutants affect SMB and its associated resources. Contaminants can be processed through various wetland environmental compartments; including the water column, sediments, and living organisms.
Estuarine Plants: Southern California Coastal Zone. The plant research focused on nutrient fluxes into and cycling within estuaries, and the effects of nutrient enrichment on intertidal and subtidal marine plants (algae and vascular plants). Because the original coastal marshes comprising the SMB watershed have been significantly impacted by development or dredging, Upper Newport Bay (UNB) and Mugu Lagoon-both outside but near to SMB-were used as prototypical study sites. Quarterly field sampling was conducted for one year in UNB to measure nutrient levels in the water column, sediments, and algal tissue at eight locations. In addition, the magnitude and species composition of algal blooms in the bay were measured. These data serve as a baseline for assessing the potential impacts of planned wastewater releases on algal blooms and the nutrient status of the bay.
Field sampling indicates that UNB is highly eutrophic, with water column nitrate levels in the upper bay reaching 800 µM, a level 100 times greater than ocean water. However, most of these nutrients are removed by macroalgae, or are captured in sediments as the water is transported through the estuarine system. Nitrogen levels in algal tissue reflect the enrichment. A distinct seasonal cycle also was found, in which the algal community shifts from dominance by benthic diatoms in winter, to blooms of Enteromorpha in spring and early summer, and finally a replacement of Enteromorpha by Ulva in late summer and early fall.
Quarterly observations provided conflicting indicators of nutrient limitation for the macroalgal blooms investigated. Water column nitrogen-to-phosphorus (N:P) ratios were high-up to 370:1-suggesting potential phosphorous limitation, while sediment N:P ratios were low-<4:1-suggesting nitrogen limitation. A microcosm experiment was conducted to test whether macroalgae were nitrogen- or phosphorous-limited in this system. The results indicate that even at high nutrient levels (300 µM N and 30 µM P), macroalgal growth was nitrogen-limited. Despite high nitrogen loading over the course of the experiment, the burden in the water column remained low, being removed by the increasing algal biomass. The Watershed data indicate that macroalgae also employed N originating in sediments for growth. At the same time that nitrogen was accumulating in algal tissue, it was decreasing in microcosm sediments. These results have important implications for the management of UNB.
The plant team undertook two other experimental studies. In one, the response of Encephalitozoon intestinalis to fluctuating salinity in a coastal estuary was measured to quantify the potential sensitivity to highly variable anthropogenic freshwater influxes. In a fully crossed two-factor experiment, E. intestinalis was subjected alternatively to fresh and ambient waters over 24-day periods. Depending on the nutrient base and duration of exposure to freshwater, significant effects were recorded. These included loss of pigmentation, decreased wet and dry biomass, increased wet-to-dry mass ratios, decreased removal of nitrogen and phosphorus from the water column, and an accumulation of ammonia in the water column. It was concluded that the growth of E. intestinalis is sensitive to reduced salinity and may suffer if it is regularly reduced.
Finally, the nitrogen dynamics of salt marsh vascular plants were studied. In a Southern California salt marsh subject to previous long-term eutrophic conditions, Silene virginica (pickleweed) strongly responded to applied nitrogen. Although phosphorus addition did not result in significant biomass changes, it did influence tissue nutrient levels. Again, such results have important implications for efforts to restore and protect wetlands from the consequences of nutrient enriched runoff.
Estuarine Fish: L.A. Area Wetlands. While diverse organic and inorganic pollutants are known to enter estuaries, little is known about their effects on resident fish populations. The present Watershed study considered: (1) how different concentrations of chemical pollutants might affect the abundance and population dynamics of wild estuarine fish; (2) how prolonged exposure of caged fish to pollutants in situ influences their growth rates and survival; and (3) how fish from different estuaries differ in their responses to pollution.
Fish surveys were conducted in five estuaries within the greater L.A. area: Alamitos Bay, Anaheim Bay, Ballona Wetland, Mugu Lagoon, and Newport Bay. Individuals were counted and measured, and their ages and growth rates estimated using growth rings in the otolith, or ear bone. At each site, samples of sediment and water also were collected and analyzed for metallic pollutants associated with the sediment, adsorbed on suspended solids, or in the aqueous phase. A suite of organic pollutants was measured, including PCBs, DDTs, phthalates, phenols, pesticides, and PAHs, with the goal of correlating pollutant loadings with fish populations. Tissue samples also were analyzed for the presence of organic pollutants. These values correlated with concentrations in sediments.
Four caging experiments were conducted to determine fish survival and growth rates at different sites with varying pollutant loads. The California killifish (Fundulus parvipennis), and the longjaw mudsucker (Gillichthys mirabilis), were used in two experiments. Both species are common at all five estuaries surveyed, and are representative of the different life histories exhibited by estuarine fishes.
In the caging experiments, no consistent differences were detected in the growth rates among fish originating from various estuaries transplanted into a specific estuary. On the other hand, consistent differences were found in the growth rates at different sites, with fish transplanted to Ballona growing the fastest (compared to fish transplanted to Mugu and Alamitos). Similarly, fish transplanted to Ballona survived in greater numbers than those transplanted to the other estuaries.
To supplement the field experiments on killifish, a laboratory test was conducted to investigate the possibility that populations from different estuaries have evolved differences in inherent performance. Fish were collected from each of three wetlands (Ballona, Mugu, and Alamitos) and placed in a series of aquaria (three aquaria per estuary). The fish were maintained under constant conditions for 2.5 months while being fed ad libitum. The results show that subtle differences in the growth rates of these specimens are indeed apparent, with fish from Ballona growing somewhat faster than those from other sites. However, the differences were not statistically significant.
Regarding the relationship of fish survival to pollutant exposure, initial studies centered on pollutants in sediments. Twenty-one metals and 142 organic compounds were screened in sediment samples from the study areas. When these chemicals are individually examined for correspondence with data on fish performance, a complex pattern emerges. For example, during the first field test on G. mirabilis, none of the metal concentrations at the sites varied in a manner that corresponded with the growth rate or survivability of the fish. Each metal varied more or less independently between estuaries. These results point up the difficulty in correlating any one, or even several, pollutant factors with observed ecological change. In the field, fish grew fastest at Ballona, at intermediate rates at Mugu, and slowest at Alamitos. The highest pollutant loadings also were found in Alamitos, which is in accord with the fish growth results. However, the lowest pollutant levels were found in Mugu, not Ballona.
SMB: State of the Wetlands. We draw several conclusions on the state of wetlands in SMB:
· The degradation and destruction of the once extensive tidal wetlands in the SMB watershed have reduced, to an unknown but probably substantial degree, the natural ability of these ecosystems to cleanse land runoff of anthropogenic pollutants. As a result, larger quantities of certain pollutants are transported into SMB.
· The preservation, rehabilitation, and expansion of remaining wetlands would likely restore some significant fraction of their prehistoric filtering capability.
· Pollution of SMB and other Southern California estuaries by anthropogenic nutrients in runoff results in severe and continuing eutrophication of the receiving waters. Additional pollution accompanying population growth across the region will intensify this destructive process.
· Toxic substances in land runoff harm estuarine fish, most likely through synergistic effects caused by exposure to multiple pollutants.
· The social cost of tidal wetland losses throughout Southern California, and the economic costs and benefits of tidal wetland restoration cannot be accurately calculated at this time. A more extensive scientific understanding of key wetland processes and functions is required.
Coastal Ocean. The Coastal Ocean component of the L.A. Watershed project addressed a range of issues associated with coastal marine sciences, and connected coastal studies to other components of the overall watershed analysis. Several significant advances were made during the course of the project. The first coastal ocean circulation model for the west coast of the U.S. and Southern California was developed and applied in this study. The model treats both physical and biogeochemical processes, and is capable of resolving features of coastal waters to a scale of about one kilometer along the entire western U.S. coastline. Significant new findings with regard to the distribution of squid larvae in the region of SMB and the Southern California Bight (SCB) also were obtained. This work is important in linking the physical oceanography of the region with the chemical and biological oceanography, including the impacts of climatic change and contaminating nutrients and toxics on the performance of important fishery species. Finally, a careful analysis of newly obtained and historical sediment compositional data for SMB was used to track the fate of particulate-associated contaminants within the SMB system. This analysis provided the basis for a more far-ranging mass balance assessment of the sources and inventories of pollutants in the bay.
Coastal Ocean Circulation and Transport. A new Regional Ocean Modeling System (ROMS) was developed under the Watershed project. ROMS was applied to study ocean circulation along the southern California coast and SMB. A novel numerical technique has been implemented to allow nested simulations from Pacific Ocean basin gyres, to west coast currents, to eddies in SMB. This methodology leads to a resolution that is sufficient for budget calculations in the bay, while still properly representing the dynamic forcing at larger scales. Model simulations were tested against measurements of ocean surface currents, sea surface temperatures, sea level height, and ocean color with favorable results. Satellite data sets (including AVHRR, RADARSAT, and SeaWIFS) also were utilized to characterize eddy circulations in SMB, as a prelude to the validation of very high resolution simulations.
In the last year, a biogeochemical multi-trophic-level nutrient-based model was introduced into ROMS. The resulting coupled circulation/ecosystem model has been used to carry out preliminary studies of the dynamical character of the California Current System, its vigorous upwelling and mesoscale eddy variability, and the implications of such dynamics for phytoplankton populations. An important finding of this analysis is that the mean and seasonal coastal ocean currents, and the corresponding distributions of tracers and biological properties, are strongly altered by transient circulations and eddies. Although calibration of the ecosystem model has not yet been completed, preliminary comparisons between predicted and measured patterns of productivity in coastal upwelling zones are encouraging. Further, ROMS properly predicts the offshore magnitude and extent of these biologically active zones, while also resolving eddy-scale features in the distribution of biomass, as observed. It follows that ROMS should be more than adequate for simulating the circulation of SMB and other small coastal structures.
Coastal Biological Processes and Biogeochemistry. The biological oceanography of the SCB in general, and SMB in particular, is strongly affected by periodic winter storms and the powerful current systems dominating the Southern California Coastal Ocean. Winter storms can be quite intense, often inducing deep mixing and surface enrichment of nutrients, which leads to dramatic increases in phytoplanktonic populations. During the long summer season, by contrast, the SCB is warmed at the surface and becomes more stratified, resulting in a reduction in surface chlorophyll.
The SCB also is affected by the northward flowing Southern California eddy, which is deflected by headlands, islands, and submarine topography, producing a large number of mesoscale cyclonic and anticyclonic gyres in the bight. These circulations aggregate zooplankton along convergent fronts, and generate significant local upwelling that enriches the entire SCB and SMB. The mesoscale turbulence, although present throughout the year, is more or less unpredictable. This chaotic source of nutrients, together with patchy aggregations of phytoplankton, dominate biological activity in the bight, generating several important fisheries that include relatively large schooling species, such as anchovies, sardines, and squid, animals capable of traveling long distances in search of food. The near coast tidal mixing connected with coastal topography also provides a critical habitat zone. The survivorship of many species, such as larval squid, is closely related to the availability of inshore waters enriched by tidal activity. Hence, the entire range of features characterizing the topography and circulation of the SCB is associated with variability in nutrient sources and habitats for the wide range of species populating this coastal zone.
To provide a better understanding of the interactions between the dynamics of the SCB, including El Niño disturbances and the distributions and abundances of key fishery species, a detailed study of the California market squid, Loligo opalescens, was undertaken. Following the intense El Niño of 1997-1998, market squid paralarvae were collected along transects in the SCB from 1999 through 2001, during the spawning season (with more than 10,000 paralarvae obtained from 422 samples). The abundance of paralarvae increased dramatically from 1.5 squid per 1000 m3 in 1999, to 77.9 squid per 1000 m3 in 2000, and 73.6 squid per 1000 m3 in 2001. This population increase is interpreted as a recovery in larval populations, following lows induced by the previous El Niño event. The variation also suggests that climatic disturbances can perturb squid fisheries for up to several years. Paralarvae also were found to be very abundant close to shore for up to a month after hatching in 2000. In this regard, tidal surface currents adjacent to shore in the Channel Islands seem to impact larval numbers significantly. Tidally reversing currents within 1-3 kilometers of the coast create an inshore boundary layer within which the paralarvae are entrained immediately after hatching. The age of paralarvae (based on statolith increments) entrained within the Catalina Island boundary layer averaged 13-16 days, although some individuals remained near shore for up to a month. Neritic currents further from the coast act to disperse older members throughout the SCB. The greatest changes in paralarval abundances seen along all transects were observed within one kilometer of the transition between these near-shore and offshore flow regimes. In each case, the paralarvae are found above 80 meters depth both day and night, and exhibit a statistically significant pattern of vertical diel migration. At sea, the paralarvae were disproportionately abundant adjacent to fronts associated with uplifted isotherms, where nutrients are usually enhanced.
SMB Pollution Assessment. The L.A. Watershed research project sought to characterize the sources and distributions of pollutants affecting SMB. This analysis included a review of the natural features of the bay, including its topography, water movement and associated material transport, sediment dynamics, and sources of natural pollutants, such as petroleum and heavy metals. Certain biological aspects of SMB also were considered in this context, including the relationship of coastal zone ecology to marine physical and chemical environments. Major sources of anthropogenic pollutants for SMB have been identified, including a number of specific point and non-point sources. The contamination of bay sediments has been treated in some detail, including the identification of likely sources of toxics, and the evaluation of potential resuspension from sediment pools. Towards the end of the project, inventories for various pollutants were estimated using a mass balance approach encompassing key sources and reservoirs.
The Watershed project addressed the role of atmospheric transport as a source of coastal pollution. A number of measurements were carried out on SMB to characterize pollutant deposition on its surface waters. Samples of the surface microlayer and adjacent water column were collected, and high-resolution hydrographic surveys were carried out, from the UCLA vessel, Sea World. The seaborne sampling was performed collaboratively with the Southern California Coastal Water Research Project, the SMB Restoration Project, and the L.A. County Department of Public Works. These unique measurements of the concentrations of organic and inorganic constituents in the overlying air, microlayer, and bulk water of SMB allowed deposition rates to be estimated. The results indicate that the concentrations of specific target constituents are significantly enhanced in the microlayer compared to bulk water, and that the enhancement is greatest near shore and after periods of offshore winds. Based on these studies, the absolute fluxes of trace metals to SMB have been quantified.
Samples of sediments from several sites in SMB were analyzed to determine the abundances of PAHs, linear alkylbenzenes (LABs), chlorinated hydrocarbon pesticides, including DDTs, and PCBs. Data was collected over 3 years, and yielded detailed information on DDTs and polychlorinated biphenyls. The PAHs and LABs also were quantified in these samples. The new data provided sufficient spatial coverage of SMB to allow the sources, reservoirs, and dispersion of new and old materials, as well as short-term trends in concentrations, to be investigated. To construct a more general picture of sediment contamination throughout the bay, the present measurements have been augmented using archived data from the Sanitation Districts of the City of L.A. (e.g., monitoring samples from the Hyperion treatment plant).
As part of the work on the origins of trace compounds in coastal sediments, a novel approach for discriminating the sources of DDT in bottom samples succeeded in separating the contributions due to sewage outflows and industrial dumping. The sewage source should exhibit a close relationship between DDT and another class of stable organic compounds used in detergents, the LABs. Thus, using LABs as a sewage tracer, coastal areas suffering industrial DDT pollution have been clearly identified for the first time. This information can be used to formulate remediation plans for the region.
The distribution patterns of specific contaminants in sediments provide a picture of the dispersion of sewage effluent throughout SMB. It also is evident that specific areas exist in sediment where sewage debris preferentially accumulates close to, and downstream from, discharge points. Sediments such as high amounts of DDTs have been found relatively far south of the Hyperion outfall. However, these elevated abundances also may be connected with emissions from the Whites Point Outfall (used by the L.A. County Districts bordering the Palos Verdes Shelf) rather than from Hyperion, owing to transport associated with the California Counter Current. Ultimately, the source can be differentiated by examining additional data on the DDT distributions in sediments across the Palos Verdes Shelf and in adjacent areas. The data generated by this component of the Watershed project are available from the GIS database established for the Watershed project.
Journal Articles on this Report : 22 Displayed | Download in RIS Format
Other project views: | All 91 publications | 31 publications in selected types | All 23 journal articles |
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Berk RA, Fovell RG, Schoenberg F, Weiss RE. The use of statistical tools for evaluating computer simulations -- an editorial essay. Climatic Change 2001;51(2):119-130. |
R825381 (Final) |
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Boyer KE, Fong P, Vance RR, Ambrose RF. Salicornia virginica in a Southern California salt march: seasonal patterns and a nutrient-enrichment experiment. Wetlands 2001;21(3):315-326. |
R825381 (1999) R825381 (Final) R827637 (2002) R827637 (Final) |
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Boyer KE, Fong P. Macroalgal-mediated transfers of water column nitrogen to intertidal sediments and salt marsh plants. Journal of Experimental Marine Biology and Ecology 2005;321(1):59-69. |
R825381 (1999) R825381 (Final) R827637 (Final) |
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Boyer KE, Fong P. Co-occurrence of habitat-modifying invertebrates: effects on structural and functional properties of a created salt marsh. Oecologia 2005;143(4):619-628. |
R825381 (1999) R825381 (Final) R827637 (Final) |
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Boyle KA, Kamer K, Fong P. Spatial and temporal patterns in sediment and water column nutrients in a eutrophic Southern California estuary. Estuaries and Coasts 2004;27(3):378-388. |
R825381 (1999) R825381 (Final) R827637 (2002) R827637 (Final) |
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DiGiacomo PM, Holt B. Satellite observations of small coastal ocean eddies in the Southern California Bight. Journal of Geophysical Research 2001;106(C10):22521-22543. |
R825381 (Final) |
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DiGiacomo PM, Hamner WM, Hamner PP, Caldeira RMA. Phalaropes feeding at a coastal front in Santa Monica Bay, California. Journal of Marine Systems 2002;37(1-3):199-212. |
R825381 (Final) |
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Forrester GE, Fredericks BI, Gerdeman D, Evans B, Steele MA, Zayed K, Schweitzer LE, Suffet IH, Vance RR, Ambrose RF. Growth of estaurine fish is associated with the combined concentration of sediment contaminants and shows no adaption or acclimation to past conditions. Marine Environmental Research 2003;56(3):423-442. |
R825381 (1999) R825381 (Final) |
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Hidalgo HG, Dracup JA, MacDonald GM, King JA. Comparison of tree species sensitivity to high and low extreme hydroclimatic events. Physical Geography 2001;22(2):115-134. |
R825381 (Final) |
not available |
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Hunt JC, Zeidberg LD, Hamner WM, Robison BH. The behaviour of Loligo opalescens (Mollusca: Cephalopoda) as observed by a remotely operated vehicle (ROV). Journal of the Marine Biological Association of the United Kingdom 2000;80(5):873-883. |
R825381 (Final) |
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Kamer K, Fong P. A fluctuating salinity regime mitigates the negative effects of reduced salinity on the estuarine macroalga, Enteromorpha intestinalis (L.) link. Journal of Experimental Marine Biology and Ecology 2000;254(1):53-69. |
R825381 (1999) R825381 (Final) R827637 (2000) R827637 (Final) |
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Kamer K, Boyle KA, Fong P. Macroalgal bloom dynamics in a highly eutrophic southern California estuary. Estuaries and Coasts 2001;24(4):623-635. |
R825381 (1999) R825381 (Final) R827637 (2000) R827637 (2002) R827637 (Final) |
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Keyantash J, Dracup JA. The quantification of drought: an evaluation of drought indices. Bulletin of the American Meteorological Society 2002;83(8):1167-1180. |
R825381 (Final) |
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Lu R, Turco RP, Stolzenbach K, Friedlander SK, Xiong C, Schiff K, Tiefenthaler L, Wang G. Dry deposition of airborne trace metals on the Los Angeles Basin and adjacent coastal waters. Journal of Geophysical Research-Atmospheres 2003;108(D2):4074. doi: 10.1029/2001JD001446. |
R825381 (Final) |
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Marchesiello P, McWilliams JC, Shchepetkin A. Open boundary conditions for long-term integration of regional oceanic models. Ocean Modelling 2001;3(1-2):1-20. |
R825381 (Final) |
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Marchesiello P, McWilliams JC, Shchepetkin A. Equilibrium structure and dynamics of the California current system. Journal of Physical Oceanography 2003;33(4):753-783. |
R825381 (Final) |
Exit Exit Exit |
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Schoenberg F, Berk R, Fovell R, Li C, Lu R, Weiss R. Approximation and inversion of a complex meteorological system via local linear filters. Journal of Applied Meteorology 2001;40(3):446-458. |
R825381 (Final) |
Exit Exit Exit |
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Shchepetkin AF, McWilliams JC. A method for computing horizontal pressure-gradient force in an oceanic model with a nonaligned vertical coordinate. Journal of Geophysical Research 2003;108(C3):3090. doi: 10.1029/2001JC001047 |
R825381 (Final) |
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Song YT, Chao Y. A theoretical study of topographic effects on coastal upwelling and cross-shore exchange. Ocean Modelling 2004;6(2):151-176. |
R825381 (Final) |
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Venkatesan MI, Northrup T, Baek J. Trace organic contaminants and their sources in surface sediments of Santa Monica Bay, California, USA.MARINE ENVIRONMENTAL RESEARCH2010;69(5):350-362 |
R825381 (Final) |
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Zeidberg LD, Hamner WM. Distribution of squid paralarvae, Loligo opalescens (Cephalopoda: Myopsida), in the Southern California Bight in the three years following the 1997-1998 El Nino. Marine Biology 2002;141(1):111-122. |
R825381 (Final) |
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Zeng EY, Venkatesan MI. Dispersion of sediment DDTs in the coastal ocean off southern California. Science of the Total Environment 1999;229(3):195-208. |
R825381 (1999) R825381 (Final) |
Exit Exit |
Supplemental Keywords:
air, water, watersheds, wetlands, runoff, land, terrestrial, microlayer, sediments, marine, coastal ocean, estuary, precipitation, toxics, bioavailability, ecological effects, human health, animal, fish, algae, population, chemicals, air pollution, ozone, toxics, particulates, polycyclic aromatic hydrocarbons, PAHs, polychlorinated biphenyls, PCBs, DDT, metals, heavy metals, organics, effluent, discharge, runoff, outflow, suspended solids, ecosystem, estuary, salt marsh, wetlands, indicators, restoration, habitat, remediation, restoration, coastal management, conservation, water quality, air quality, atmospheric sciences, biology, environmental chemistry, public health, engineering, ecology, hydrology, meteorology, oceanography, dendrochronolgy, biogeochemistry, modeling, monitoring, surveys, remote sensing, in situ sampling, satellite, geographic information systems, GIS, western U.S., pacific coast, California, southern California, Los Angeles Basin, LAB, Santa Monica Bay, SMB, Southern California Bight, SCB, water resources, transportation, land development, industry., RFA, Scientific Discipline, Water, Geographic Area, Waste, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Water & Watershed, Hydrology, Geochemistry, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Contaminated Sediments, State, Ecological Effects - Environmental Exposure & Risk, Ecological Risk Assessment, Watersheds, aquatic ecosystem, coastal ecosystem, nutrient supply, remote sensing, basin hydrology, ecological exposure, wetlands, coastal watershed, meteorology, sediment, urban watersheds, contaminated sediment, Los Angeles Basin, coastal environments, sediment runoff, aquatic ecosystems, urbanizing watersheds, water quality, biogeochemistry, California (CA), groundwater, land useProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.