Grantee Research Project Results
2007 Progress Report: Stimulation of Toxic Blooms of the Diatom Pseudo-nitzschia spp. by Urban River Discharge into Southern California Coastal Waters
EPA Grant Number: R831705Title: Stimulation of Toxic Blooms of the Diatom Pseudo-nitzschia spp. by Urban River Discharge into Southern California Coastal Waters
Investigators: Caron, David A. , Miller, Peter E. , Schnetzer, A.
Current Investigators: Caron, David A. , Miller, Peter E. , Schnetzer, Astrid
Institution: University of Southern California , University of California - Santa Cruz
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2004 through August 31, 2007 (Extended to August 31, 2008)
Project Period Covered by this Report: September 1, 2006 through August 31,2007
Project Amount: $350,765
RFA: Ecology and Oceanography of Harmful Algal Blooms (2004) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water
Objective:
The Los Angeles area of the Southern California Bight is the focal point of this field-oriented ECOHAB research program to investigate the relationship between freshwater inputs from a highly urbanized coastal region and blooms of the toxic diatom Pseudo-nitzschia. The Los Angeles Harbor and adjacent coastal ocean is periodically influenced by runoff from 3 major rivers. Freshwater discharge from the Los Angeles River, San Gabriel River and Santa Ana River contribute substantial amounts of inorganic nutrients, labile organic compounds and trace metals to the coastal region. River input is strongly episodic, highly channelized, and restricted primarily to winter/early spring. It is hypothesized that these meteorological events influence phytoplankton dynamics and the formation of harmful algal blooms. This research program examines the connection between storm events and Pseudo-nitzschia species success and the production of domoic acid in coastal communities. The program also addresses the relative importance of natural coastal upwelling and river input on phytoplankton blooms and toxic events caused by Pseudo-nitzschia species.
Approach:
A sampling grid (up to 45 sites) encompassing three major river discharges will be studied following a major rainfall event in each of two consecutive years. Samples will be collected at 2-4 day intervals for a period of 2-3 weeks following each event. Supplemental samples will be collected bi-weekly throughout the year along a single cross-shelf transect. Remote sensing will be used to guide sampling during the storm events. Plankton abundances will be determined using flow cytometry, FlowCAM and fluorescence microscopy. Pseudo-nitzschia spp. abundance will be determined by microscopy (light, SEM), fluorescent in-situ hybridization, and quantitative real-time PCR. Domoic acid concentrations will be obtained using an immunological method. Physical parameters, nutrient and trace metals will be analyzed.
Progress Summary:
The study area encompasses ~400 km2 off the coastal Southern California Bight between the Palos Verdes peninsula and Newport Beach (Fig 1). Multiple surveys (weekly to monthly) were conducted throughout 2005, 2006 and 2007 in order to characterize the impact of river discharge on phytoplankton blooms in general, stimulation of blooms of the potentially toxic diatom Pseudo-nitzschia spp., and stimulation of the production of domoic acid (please find project results for 2005 and for the first half of 2006 detailed in prior Progress Reports).
Fig. 1: Study region. During each survey surface water was collected at 20 stations (dots). Three stations south of the LA harbor (along white line) were sampled bimonthly to monitor for Pseudo-nitzschia presence between major sampling events.
2006 Summary: A Pseudo-nitzschia bloom dominated by P. australis was observed in the study area between February and May of 2006. Domoic acid concentrations reached their maximal levels during mid-March and a second peak occurred in mid-April (Fig. 2). In contrast to March and April cell abundances and toxin concentrations did not follow the same trend in June when an increase in P. australis numbers at several of the 20 sampling stations was not associated with increased domoic acid levels (Fig. 2). Overall cell abundances ranged from <10 – 1,477 cells L-1 and domoic acid concentrations ranged from 0 – 14.4 μg DA L-1 with a mean of 171 cells L-1 and 1.26 μg DA L-1, respectively. Abundances and toxin levels were used to calculate per cell toxin quotas which ranged from 0 – 66 pg DA cell-1 and averaged 6.03 pg DA cell-1.
Fig. 2: Changes in Pseudo-nitzschia abundances (PN abund) and domoic acid (DA) concentrations observed in 2006. Values are shown as average for all 20 sampling locations with their standard deviation.
The completion of data analyses and processing of samples for biological (chlorophyll a, Pseudo-nitzschia abundances), physical (temperature, salinity) and chemical parameters (macronutrients PO4, NO3+NO2, Si(OH)4, domoic acid concentrations) was followed by multiple regression analyses to examine which environmental factors best correlated with particulate DA concentrations in the plankton (Table 1). Statistical testing showed that particulate DA concentrations were inversely correlated with silicate levels (p=0.003) and positively correlated with nutrient ratios N:Si(OH)4 and P: Si(OH)4 (p=0.1 and 0.001, respectively, Table 1). Particulate DA levels further increased with phytoplankton biomass (measured as chlorophyll a; p=0.000) and decreased with surface water temperature (p=0.001). These results were in good agreement with earlier field observations made during 2004 (Schnetzer et al., 2007) and with results from laboratory studies that demonstrated that silica stress can increase toxin production in Pseudo-nitzschia spp..
2007 Surveys: We continued to carry out our coastal surveys throughout 2007 and similarly to 2006 we observed a highly toxic bloom dominated by P. australis. In both years maximal toxin concentrations occurred at stations closer to the coast, more specifically inside or immediately outside the Los Angeles harbor (Fig. 3). Contrary to 2006 Pseudo-nitzschia bloom abundances were observed no earlier than late April in 2007 and the bloom did not last longer than 1 month. Although overall bloom duration was shorter toxin concentrations in excess of 25 μg DA L-1 were nearly double the highest values obtained during 2006 and were within the highest ever reported for natural algal assemblages. The color contours of Figure 3 are on the same scale to facilitate comparison of the two years.
The pattern and magnitude of the 2007 phytoplankton bloom (i.e. chlorophyll concentration) and domoic acid toxicity event are depicted in Figure 4 (shown are the results for 7 of the 11 surveys that were conducted). Note that there are two scales for the concentrations of domoic acid on this figure. The red dots indicate the extremely high values of domoic acid measured in plankton samples during late April 2007 (this panel is shown separately in Figure 3 to allow comparison with the bloom observed during 2006). The black and white dots indicate a different scale used to show the much lower concentrations of domoic acid before and only 1.5 weeks after April 26 (Fig. 4).
The majority of samples have been processed for 2007. Nutrient analyses and salinity measurements will be completed within the next months and currently underway is the completion of Pseudo-nitzschia cell enumeration by means of a newly developed genus-specific qPCR approach (see details below).
Preliminary analyses indicate that a major stimulant for the 2007 bloom was an upwelling event that occurred a week before the peak concentrations of domoic acid were observed. Two pieces of information support this preliminary conclusion. First, the year was one of the driest years ever on record and discharge from the LA River (which may play a role in some year’s blooms) was very low. Second, a significant decrease in water temperature was observed in the waters in and around the study site just prior to bloom initiation. This suggests that nutrient enrichment due to a local upwelling event may have triggered the bloom. This hypothesis will be tested as we complete all datasets for 2007 and multivariate statistics can be performed. These analyses will be followed by statistical testing of the entire Ecohab dataset which comprises of a total of 39 surveys that were conducted between 2005 and 2007.
Fig. 4: Chlorophyll concentrations (contours) and domoic acid concentrations (red, black and white dots) observed during 2007. Note that there are two different scales for the concentration of domoic acid.
The newly-developed protocol allows for the detection of Pseudo-nitzschia abundances over 4 orders of magnitude (shown for P. australis in Fig. 5). Amplification of non-target species only occurred after more than 36 cycles and allowed to determine a cut-off point for non-specific signal yield relative to the lowest resolved culture dilution of P. australis with 5 cells ml-1 (Ct=32). More than 30 protistan species were chosen for specificity tests from the lab culture collection and all of them fell below our lower detection limit. In contrast, all available Pseudo-nitzschia extracts (total of 8 different species) resulted in a significant fluorescence yield and were detectable using the approach (not shown).
Higher Trophic Level Impact: Toxic blooms of P. australis impacted a wide variety of top predator species through food web interactions during 2006 and 2007. A tight temporal relationship between bloom dynamics and animal stranding incidents was documented. For instance, the appearance of toxin in the plankton resulted in an increased number of sea lions being received by mammal care facilities within 3 days. These insights are a product of established working partnerships (see ‘Establishment of Partnerships’ section below) with animal rescue and care centers that have provided samples of tissue, fluids, stomach contents, and fecal material for domoic acid analysis over the past 2 years. 2006 and 2007 data showed that bloom duration and overall toxicity of the bloom was reflected in the number of animal strandings. Furthermore, domoic acid levels in serum samples were highest when concentrations in the plankton reached maximal levels (for details on 2006 please see prior Progress Report). More than ten coastal species (mainly birds), that had not been implicated with domoic-acid poisoning previously, tested positive for the algal toxin since early 2006. These results are now being summarized for publication.
Partnerships established: We have established working partnerships/relationships with a variety of research institutions, management groups, state and local agencies, and animal rescue and care groups. These include the following:
- CA Department of Public Health
- Southern California Coastal Ocean Observing System
- Southern California Coastal Water Research Project
- Southern California Marine Consortium
- LAC Sanitation District
- OC Sanitation District
- Wrigley Institute for Environmental Studies
- Fort McArthur Marine Mammal Care Center, San Pedro CA
- Pacific Marine Mammal Center, Laguna Beach, CA
- National History Museum, Section of Mammalogy, Los Angeles, CA
- International Bird Rescue Research Center, San Pedro, CA
- Wetlands and Wildlife Care Center, Huntington Beach, CA
- Whale Rescue Team, South Bay, CA
Expected Results:
This project will discern the patterns of environmental and biological factors stimulating population growth and domoic acid production by Pseudo-nitzschia species in coastal waters of southern California. Key factors leading to blooms of these species and toxicity events will be documented.
Future Activities:
The completion of sample processing and data analysis for the 2007 field surveys is close to completion. All datasets for 2007 will be analyzed using multivariate statistical approaches to examine how environmental parameters (nutrient data, salinity and temperature data, environmental indices such as river runoff and coastal upwelling) correlate with Pseudo-nitzschia abundances and domoic acid concentrations. Data analyses will also be performed for the complete Ecohab dataset collected from the beginning of 2005 till the end of 2007 which encompassed a total of 39 large-scale grids. Several manuscripts are currently being prepared for publication and submission to peer-reviewed journals.
Expenditures 09/01/06 - 08/31/07
Expenditures have been made during this period in accordance with our original projections. As of 01/22/08, the grant has received $365,549 in funding. The existing balance is $27,996 with an additional $35,905 in open liens. The project is currently in its non-cost extension until 08/31/2008.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 41 publications | 5 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Schnetzer A, Miller PE, Schaffner RA, Stauffer BA, Jones BH, Weisberg SB, DiGiacomo PM, Berelson WM, Caron DA. Blooms of Pseudo-nitzschia and domoic acid in the San Pedro Channel and Los Angeles Harbor areas of the Southern California Bight, 2003-2004. Harmful Algae 2007;6(3):372-387. |
R831705 (2007) |
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Supplemental Keywords:
marine, southwestern coastal ocean, toxicity, domoic acid, plankton, phytoplankton, Pseudo-nitzschia, ecosystem damage, environmental biology, ecology, remote sensing, satellite, immunology, molecular biology, microscopy, RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, estuarine research, State, Oceanography, algal blooms, Wet Weather Flows, Environmental Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, Aquatic Ecosystem Restoration, monitoring, risk assessment, aquatic ecosystem, environmental restoration, wetlands, river discharge, estuaries, bloom dynamics, watershed, downstream effects, precipitation monitoring, conservation, restoration strategies, aquatic degradation, environmental stress, combined sewer overflows, environmental indicators, California (CA), algal bloom detection, storm drainage, stormwater runoff, storm events, contaminated waterfronts, groundwater pollution, domoic acid producing diatoms, real-time monitoringProgress 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.