Grantee Research Project Results
Final Report: CISNet: In Situ and Remote Monitoring of Productivity and Nutrient Cycles in Puget Sound
EPA Grant Number: R826942Title: CISNet: In Situ and Remote Monitoring of Productivity and Nutrient Cycles in Puget Sound
Investigators: Emerson, Steven
Institution: University of Washington
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2002)
Project Amount: $581,876
RFA: Ecological Effects of Environmental Stressors Using Coastal Intensive Sites (1998) RFA Text | Recipients Lists
Research Category: Environmental Statistics , Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
The objective of this research project was to develop a profiling mooring-the Oceanic Remote Chemical/Optical Analyzer (ORCA)-to monitor water quality remotely in south Puget Sound, Washington state. South Puget Sound includes the most inland reaches of the Puget Sound estuary network and is characterized by relatively sluggish circulation, seasonal stratification, and intense phytoplankton blooms coupled with nutrient depletions in the spring and summer months. With extensive urbanization of the area predicted for the next 10 years, south Puget Sound is potentially at risk to impacts from eutrophication. The intention of the ORCA profiler was to provide high resolution, long-term time series data at one location, which would enable us to monitor tidal, diel, seasonal, and inter-annual cycles and trends in stratification, oxygen, nutrients, water clarity, phytoplankton abundance, and community distribution. In addition to the mooring itself, there was a proposed field component that was intended for both verification of the mooring derived data and for a broader survey of ambient conditions in Puget Sound. Our intention was to use the mooring data combined with the survey data and optics data from the mooring location to test ecological and biogeochemical hypotheses about Carr Inlet, as well as to extend these interpretations to greater Puget Sound through broader survey and remote sensing data.
At the beginning of this research project, we established a project Web site, where we included a brief overview of the project, a list of the people involved, pictures from our test deployments, viewable data, and current status information. Regular, automatic updates keep viewable data current. The reader is referred to this location for more detail about the research project and any current data.
Summary/Accomplishments (Outputs/Outcomes):
ORCA (see Figure 1) was designed and constructed at the University of Washington (UW) from a combination of custom and commercially available components developed with assistance from UW Oceanography Technical Services. ORCA has three main components: a three-point moored float, a profiling assembly, and an underwater sensor package. The mooring is anchored in a three-point configuration, with each point consisting of two railroad wheel anchors (620 kg), connected through a combination of chain and wire rope to a 250-kg steel ballast ring. Mounted atop the float is a platform with housing and superstructure, a 24-Volt, 1/3 Hp marine winch, four 12V/98 amp-hour gel-cell batteries, custom electronics control package, surface computer, cellular modem, Davis weather station, and two 75-Watt solar panels. The ORCA profiler has 2-nautical mile amber flashing beacon and a radar reflector that are mounted on the superstructure.
Figure 1. Schematic of the ORCA Profiler
The ORCA sensor package consists of standard sensors used for shipboard CTD profiling mounted within a stainless steel cage (30-cm wide, 1-m high). Power and communications between the underwater package and the surface computer are achieved through a five-conductor, Kevlar-reinforced hydrowire, attached to the winch through a six-conductor slip ring assembly. The hydrowire terminates at the sensor cage with a combination of polypropylene cable grip and thimble. Power and communications from the surface terminate at a module that provides power for the sensors during sampling through a 12-V, 5 amp-hour battery and voltage regulator, which is trickle-charged through the hydrowire at all times. The basic sensors consist of: a Seacat-19 conductivity, temperature, depth profiler from Seabird Electronics, a Seabird-YSI Oxygen electrode, a Wetlabs Wetstar chlorophyll fluorometer, and a Wetlabs C-star 660-nm, 10-cm path length transmissometer.
We conducted profiling by using the surface computer to control the sequence and timing of the sampling operations, communicating with the sensors, and controlling the winch by applying power and toggling a directional pin. Between profiles the sensor package parks beneath the euphotic zone to limit biofouling. At the start of the profile, the surface computer turns on the CTD and reads the pressure data, then supplies power to the winch until the package is at the programmed depth. After the package has profiled the water column and is back at the parking depth, the surface computer downloads the instrument data. Every night, the surface computer uses the cellular modem to call the host computer at UW and transfers all new data files to our database.
Figure 2. Carr Inlet, Puget Sound, Washington State (star indicates mooring site)
Since its deployment in Carr Inlet (47° 16.779' N,122° 43.658' W, see Figure 2) on May 25, 2000, ORCA has provided a near-continual stream of high-resolution water quality data from Carr Inlet (2002 results are presented in Figure 3; refer to the Web site for data from previous years) with some data gaps due to routine maintenance and malfunctioning instrumentation. We are continually conducting data quality assurance, data reduction, and time-series analysis in an effort to understand the sources of variability in this growing data set. Throughout the 3 years of data collection, we observed a considerable covariation in all parameters, indicating a tight coupling between physical and biological processes in Carr Inlet. Throughout the summer and early fall, variability in wind, rainfall, and sunlight forced temperature and salinity between intermittent periods of either strong stratification or deep mixing. The seasonal cycle in temperature and salinity also was intense, with the intermittently high surface temperatures disappearing entirely in the fall and salinity increasing steadily throughout the summer and fall. Oxygen and chlorophyll covaried in the summer through a combination of physical response to the intermittent stratification and mixing and biological response to primary production and respiration. At depth, we observed the generation and strengthening of low oxygen conditions throughout the summer with destruction of this stratification during the onset of intense mixing in the fall. Oxygen saturation varied from undersaturation (~60 percent) at all depths during the winter, to mid-summer values near saturation (~90-100 percent) at depth and supersaturated (~150 percent) at the surface.
Figure 3. ORCA Time-Series of Temperature, Salinity, Density, Oxygen, Oxygen Saturation, and Chlorophyll Fluorescence From January 1, 2002-December 19, 2002
In terms of our objectives, the Puget Sound Monitoring project has been successful. We were able to build an autonomous profiling mooring that has provided us with a high resolution, long-term data set in Carr Inlet. With this data set, we have been able to monitor tidal, diel, seasonal, and inter-annual cycles and trends in stratification, oxygen, water clarity, and phytoplankton abundance. One of the unexpected results of the project is that we are able to determine the diurnal oxygen concentration changes by calculating the mean diurnal change measured in over 600 profiles for the period between May 1 and September 30, 2002 (see Figure 4). To demonstrate how often one would have to sample to resolve this diurnal oxygen change, we randomly subsampled the entire 2002 data set at various frequencies. This result (see Figure 5) demonstrates that the character of the diurnal oxygen change is lost if samples are conducted less frequently than every 2 hours during the day, every other day.
Figure 4. Hourly Oxygen Averages for all Casts From May Through September 2002
We are in the process of formulating biogeochemical models that may help us to quantitatively distinguish between the biological and physical effects such that we can understand controls on oxygen concentrations in both the surface and deep waters. The field component of the project has provided an additional database, such as a primary productivity model based on 14C incubation measurements. The comparison between results at ORCA and the field component of the project lead to some interesting questions, and potential areas of future research.
A one-dimensional oxygen mass balance using the 2002 data set to evaluate air-water gas transfer and the time dependent changes of oxygen in the euphotic zone reveals a net daily oxygen production of 10 mmoles m-2d-1 that, when divided by a ΔO2:ΔC ratio of 1.45, results in a net community production rate of 120 mg C m-2d-1. A primary production estimate determined by WaDOE using 14C incubation measurements is 3,400 mg C m-2d-1, indicating that less than 10 percent of the net primary production escapes the euphotic zone in summer. We have shown that the oxygen budget calculation that can be accomplished with the high frequency profiling-mooring data allows an estimate of C-export to deep waters, which is one of the primary factors affecting dissolved oxygen drawdown in these waters. These types of data and analyses further our ability to predict summer levels of deep water oxygen, which is an important water quality parameter.
Figure 5. Hourly Oxygen Averages for all Casts From May Through September 2002, Using Random Subsampling
Although the U.S. Environmental Protection Agency grant has ended, we have secured other funding to work with a large collaborative project in Carr Inlet, and will continue to collect data with the ORCA mooring through spring of 2003. As part of this research project, we plan to complete the testing of the new nutrient analyzer and integrate it into the package for the 2003 spring bloom. High-frequency nutrient data at both the surface and at depth, and a clearer understanding of what the models showing us about the controls on oxygen concentration and production, will further our understanding of the vulnerability of Carr Inlet to hypoxia through eutrophication.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 11 publications | 1 publications in selected types | All 1 journal articles |
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Type | Citation | ||
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Dunne JP, Devol AH, Emerson S. The Oceanic Remote Chemical/Optical Analyzer - An autonomous moored profiler. Journal of Atmospheric and Oceanic Technology 2002;19(10):1709-1721. |
R826942 (2000) R826942 (2001) R826942 (Final) |
not available |
Supplemental Keywords:
water, marine, estuary effects, vulnerability, population, water quality nitrate, oxygen environmental chemistry, ecology modeling, monitoring, Pacific Coast, Pacific Northwest, Washington, WA, EPA Region 10., Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, State, Monitoring/Modeling, Ecological Risk Assessment, anthropogenic stress, aquatic ecosystem, coastal ecosystem, eutrophication, nutrient supply, nutrient transport, remote sensing, CISNet, bioavailability, chemical speciation, coastal zone, remote sensing data, Puget Sound, CISNet Program, biomass, Washington (WA), nutrient cycling, water quality, gas concentrations, nutrient transport model, in situ chemical profilesRelevant Websites:
Marine water & sediment monitoring
Progress 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.