Dissolved Oxygen

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Chesapeake Bay Program Indicator Framework 

Reporting Level Indicators

Indicator and Data Survey

For each indicator for which you are responsible, please provide the following information. This information will be made available to the developers of the reports, the reviewers of the reports and by members of the public who may request detailed information about the data used in the reports.  

A. Category/Name/Source/Contact 

(1) Category of Indicator 

___ Factors Impacting Bay and Watershed Health 

___ Restoration and Protection Efforts 

___ Watershed Health 

__X__ Bay Health 

(2) Name of Indicator: Dissolved Oxygen in Chesapeake Bay

(3) Data Set Description: 

For what purpose(s) were the data collected? (e.g., tracking, research, or long-term monitoring.)  Tracking, research, and long-term monitoring.  

Which parameters were measured directly? Which were obtained by calculation? 

DO concentrations are measured in-situ at surface and depth profiles at fixed stations in the entire Bay.

(4) Source(s) of Data: DO is measured by the MD Department of Natural Resources (MD mainstem and tributary data), the VA Department of Environmental Quality (VA tributary data and benthic monitoring data), Old Dominion University (VA mainstem data), Virginia Institute of Marine Sciences (VA data), and Alliance for the Chesapeake Bay (volunteer monitoring program in VA). 

Is the complete data set accessible, including metadata, data-dictionaries and embedded definitions? If yes, please indicate where complete dataset can be obtained.

Data included in standard monitoring programs are located on the CIMS data hub. These data can be downloaded from the Chesapeake Bay Program website (http://www.chesapeakebay.net/wquality.htm) by selecting the “data” tab and subsequently the “CBP Water Quality Database (1984-present)” for dissolved oxygen data.  Additional data submitted by the states from non-standard monitoring programs can be obtained by contacting Jeni Keisman.

(5) Custodian of Source Data (and Indicator, if different):

Jeni Keisman (UMCES/CBPO) 

(6) CBPO Contact: 

Jeni Keisman (UMCES/CBPO).

B.  Communication Questions

(complete either part 1, 2, or 3) 

2. Bay Health or Watershed Health indicators only 

(7b) What is the long-term trend? (since start of data collection, 1987-2009):

Goal achievement decreased from 14.77 percent (1985-1987 assessment period) to 11.69 percent (2007-2009 assessment period). Goal achievement has averaged 20.89 percent and has ranged from 9.82 percent to 36.13 percent.

(8b) What is the short-term trend? (Trend over the past 10 years, 2000-2009)

Goal achievement decreased from 25.3 percent (1998-2000 assessment period) to 11.69 percent (2007-2009 assessment period).

(9b) What is the current status in relation to a goal? When assessing water quality, regulators examine conditions from the past three years to adjust for annual weather-driven fluctuations. Data gathered from 2007 to 2009 indicate that about 12 percent of the combined volume of open-water, deep-water and deep-channel water of the Bay and its tidal tributaries met dissolved oxygen standards during the summer months. This is a decrease of 5 percent from the 2008 assessment.

(10b) What is the key story told by this indicator?  

Standards Attainment of DO (2007-2009 assessment period):

Water quality data gathered between 2007 and 2009 indicate that about 12 percent of the Bay’s tidal waters met DO standards (i.e., the appropriate DO criteria for open water, deep water, and deep channel designated uses only) during the months of June - September.  To meet those state regulations, all data gathered within each tidal river and mainstem Bay segment must meet required DO concentrations based on a combination of interpolation and cumulative frequency distribution (CFD) analyses.  These analyses allow for some temporal and spatial exceedances of DO criteria, but if the segment of the Bay has concentrations that exceed the permitted spatial and temporal allowances, the entire volume of water for that segment is considered out of attainment.

There are several sources of DO in the Chesapeake Bay. The most important is the atmosphere where oxygen is present at concentrations very much higher than in the water. The process of atmospheric oxygen dissolving in water is enhanced by wind, which mixes the surface layer of the Bay.  Two other important sources of oxygen in Bay waters are phytoplankton (single celled plants) and submerged aquatic vegetation (SAV), or underwater grasses, which produce oxygen through photosynthesis.  A final major source of DO in the Bay comes from water flowing into the estuary from streams, rivers and the Atlantic Ocean. Water flowing in streams and rivers is more turbulent which promotes mixing in from the air. Ocean water generally has a higher DO content due to the fact that the factors that deplete oxygen are relatively small.

Processes that consume DO include plant and animal respiration, the decomposition of dead plants and animals, and the oxidation of other chemicals.  The amount of oxygen that can dissolve in water is strongly limited by the temperature of the water and, to a much smaller degree, by other substances dissolved in the water such as salt.  The colder the water, the more oxygen it can hold.  Therefore, the waters of the Chesapeake Bay have a greater capacity to hold DO during the cold winter months than they do during the summer.

As alluded to above, DO concentrations are the result of a complex interaction of natural processes (including how water circulates in the Bay, weather patterns, and seasonal cycles in the growth of plants and animals) and manmade influences.  Some variation in DO levels occurs naturally, with low DO occurring when, or where, DO is consumed faster than it can be replaced. The human impact on DO levels is the result, principally, of nutrient pollution. The extra nutrients that we add to the Bay stimulate algal growth.  Although algae produce oxygen in the daytime via photosynthesis, respiration at night and the decomposition of dead algal cells can overwhelm the processes that add oxygen, thereby resulting in very low DO concentrations.

For additional information about DO, please refer to the dissolved oxygen backgrounder (http://www.chesapeakebay.net/pubs/do...ckgrounder.pdf)

(11b) Why is it important to report this information?  Dissolved oxygen concentrations need to be high enough to support life in aquatic systems and different aquatic species have different DO requirements.  High chlorophyll-a concentrations are generally a response to increased nutrient (i.e., nitrogen and phosphorus) inputs to the Bay and are indicative of high algal biomass in the water column.  The settling and subsequent decomposition of these algae (i.e., phytoplankton) are largely responsible for the hypoxia and anoxia (i.e., low DO concentrations) in the Bay.  Therefore, DO concentrations are an important indicator of nutrient loading to the Bay and the capacity of the Bay to support aquatic life. 

(12b) What detail and/or diagnostic indicators are related to this reporting level indicator?  A current conditions indicator.

C. Temporal Considerations 

(13) Data Collection Date(s):  1985 through 2009

(14) Planned Update Frequency (e.g. - annual, bi-annual): 

(a) Source Data:  annual

(b) Indicator: annual 

(15) For annual reporting, month spatial data is available for reporting:  January of the following year.

D. Spatial Considerations 

(16) Type of Geography of Source Data (point, line polygon, other):  Point

(17) Acceptable Level of Spatial Aggregation (e.g. - county, state, major basin, tributary basin, HUC):  DO data are aggregated to 78 tidal water segments for the Chesapeake Bay (2003 revised Chesapeake Bay Program (CBP) segmentation and zonation scheme) and then aggregated to the baywide scale.

(18) Are there geographic areas with missing data? If so, where?  Yes.  The following Bay Program segments are not assessed due to insufficient data: ANATF, HNGMH, LYNPH, MATTF, and PISTF.  WBRTF is not assessed due to a lack of information on bathymetry.  Data are missing for the Potomac River for Aug-Sept 2007 due to an equipment failure. 

(19) The spatial extent of this indicator best described as:  

(a) Chesapeake Bay (estuary) XXX

(b) Chesapeake Bay Watershed 

(c) Other (please describe): ____

Please submit any appropriate examples of how this information has been mapped or otherwise portrayed geographically in the past.  The Status and Trends of dissolved oxygen is located in the Water Quality section of the Bay webpage (http://www.chesapeakebay.net/wquality.htm).

(20) Can appropriate diagnostic indicators be represented geographically?  Yes

E. Data Analysis and Interpretation

(Please provide appropriate references and location of documentation if hard to find.) 

(21) Is the conceptual model used to transform these measurements into an indicator widely accepted as a scientifically sound representation of the phenomenon it indicates? (i.e., how well do the data represent the phenomenon?).  Yes. This indicator has undergone technical and peer review by state, Federal and non-government organization partner members of the Tidal Monitoring and Analysis Workgroup (TMAW) and the Monitoring and Assessment Subcommittee (MASC). Data collection, data analysis and QA/QC are conducted by the principal investigators/scientists. The data are peer reviewed by scientists in the workgroup. Data selection and interpretation, the presentation of the indicator, along with all supporting information and conclusions, are arrived at via consensus by the scientists in collaboration with the resource manager members of the workgroup. The workgroup presents the indicator to the subcommittee where extensive peer review by Bay Program managers occurs.  The dissolved oxygen indicator is published at http://www.chesapeakebay.net/status.cfm?sid=204.

(22) What is the process by which the raw data is summarized for development and presentation of the indicator?   Raw data are processed by the Bay Program’s interpolator program and, subsequently, interpolations are analyzed by a fortran program on a linux platform to determine the volumetric extent of compliance.  

(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model).  Interpolator and fortran programs to determine the volumetric extent of compliance.

(24) Are the computations widely accepted as a scientifically sound?  Yes

(25) Have appropriate statistical methods been used to generalize or portray data beyond the time or spatial locations where measurements were made (e.g., statistical survey inference, no generalization is possible)?  Yes.  The Bay Program’s interpolator was used to extrapolate the data.

(26) Are there established reference points, thresholds or ranges of values for this indicator that unambiguously reflect the desired state of the environment? (health/stressors only)  Yes.  There are DO criteria for the Chesapeake Bay that have been developed and published for this indicator (see: http://www.chesapeakebay.net/baycriteria.htm)

F. Data Quality

(Please provide appropriate references and location of documentation if hard to find.) 

(27) Were the data collected according to an EPA-approved Quality Assurance Plan?  Yes.  Methods are described in the Quality Assurance Project Plan (QAPP) on file for the EPA grant.  Documentation is available at: http://www.chesapeakebay.net/qatidal.htm.

If no, complete questions 28a – 28d: 

(28a) Are the sampling design, monitoring plan and/or tracking system used to collect the data over time and space based on sound scientific principles? 

(28b) What documentation clearly and completely describes the underlying sampling and analytical procedures used? 

(28c) Are the sampling and analytical procedures widely accepted as scientifically and technically valid? 

(28d) To what extent are the procedures for quality assurance and quality control of the data documented and accessible? 

(29) Are the descriptions of the study or survey design clear, complete and sufficient to enable the study or survey to be reproduced?  Yes.  Methods are described in the Quality Assurance Project Plan (QAPP) on file for the EPA grant.  Documentation is available at:http://www.chesapeakebay.net/qatidal.htm.

(30) Were the sampling and analysis methods performed consistently throughout the data record?  Yes

(31) If datasets from two or more agencies are merged, are their sampling designs and methods comparable?  Yes.  Methods are described in the Quality Assurance Project Plan (QAPP) on file for the EPA grant.  Documentation is available at:http://www.chesapeakebay.net/qatidal.htm.

(32) Are uncertainty measurements or estimates available for the indicator and/or the underlying data set?  Yes.  Methods are described in the Quality Assurance Project Plan (QAPP) on file for the EPA grant.  Documentation is available at: http://www.chesapeakebay.net/qatidal.htm.

(33) Do the uncertainty and variability impact the conclusions that can be inferred from the data and the utility of the indicator?  Yes.  Dissolved oxygen is variable both spatially and temporally.  The interpolation program used to determine the spatial variability has inherent errors that add to the uncertainty of estimating DO concentrations in large areas of the Bay.  Moreover, the interpolations have inherent errors in that they are a composite of monthly data and the sampling of different parts of the Bay occurs over different times of the month.  Therefore, there are limitations to how the data can be applied and interpreted both spatially and temporally. 

(34) Are there noteworthy limitations or gaps in the data record?   No.   Please explain.  

G. Additional Information


(35) Please provide any other information about this indicator you believe is necessary to aid communication and any prevent potential miss-representation. 

Since 2003, we have included monitoring data provided by the states that were gathered by additional programs beyond the long-term fixed station monitoring program in place since 1985.  Similar data did not exist prior to 2003, so it is not included for analyses going back to 1985.  Therefore, caution should be exercised when attempting to extrapolate trends from the 1985-2009 results as the sampling regime is not consistent for the entire time period.  Specifically, additional data is included in analyses from 2003 to present.

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