Chlorophyll a

Last modified

 

Metadata 

Chesapeake Bay Program Indicator Framework 

Reporting Level Indicators

Indicator and Data Survey

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: Chlorophyll-a in Chesapeake Bay

(3) Description of Dataset used to calculate percent of goal achieved: 

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? 

Chlorophyll-a concentrations were calculated from filtered water samples at fixed stations in the entire Bay.  These values were used to obtain the percent goals.

(4) Source(s) of Data: Chlorophyll-a samples are collected by the MD Department of Natural Resources (MD mainstem and tributary data), the VA Department of Environmental Quality (VA tributary data), and Old Dominion University (VA mainstem data) 

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

Data are located on the CIMS data hub. These data can be downloaded from the Chesapeake Bay Program website (http://www.chesapeakebay.net/data_waterquality.aspx).

(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, 1985-2009) Goal achievement decreased from 47.6 percent to 29.4 percent. The score has averaged 32.9 percent and ranged from 17.3 percent to 49.8 percent of goal achieved.

The area of the Bay meeting (i.e., less than or equal to) its chlorophyll a threshold concentrations has high interannual variability, but has generally shown a decreasing trend over the period of record.. 

(8b) What is the short-term trend? (10-year trend)  Between 2000 and 2009, the chlorophyll a score increased from 22.85 percent to 29.4 percent of goal achieved.

(9b) What is the current status in relation to a goal? The goal is for 100 percent of Chesapeake Bay tidal waters to be below certain threshold concentrations of chlorophyll a that are acceptable to underwater bay grasses. In 2009, 29 percent of tidal waters had chlorophyll a concentrations below the threshold. This is an increase of 2 percent from 2008.  

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

Chlorophyll-a is the photosynthetic pigment that plants use to produce cell material from sunlight and carbon. The amount of chlorophyll-a in water is a measure of phytoplankton (aquatic algae) biomass and, therefore, is an indicator of water quality.

Phytoplankton form the base of the Bay food web and provide food for fish and other filter-feeding organisms. Changes in abundance, species composition and productivity of phytoplankton are commonly the first biological response to nutrient enrichment and are a measure of the effectiveness of nutrient reduction strategies.  These changes in phytoplankton influence the food webs of which they are a part and the fisheries that depend upon them.  Too much phytoplankton, caused by overproduction and/or under-consumption, reduces water clarity and depletes oxygen in bottom waters.

Chlorophyll-a in the Bay is measured in different ways.  The status of chlorophyll-a is currently assessed according to the limit of 15 µg L-1 for submerged aquatic vegetation (SAV).  Although inter-annual and seasonal variability are high, most areas of the Bay are below this limit for SAV, whereas the upper reaches of large tributaries and most upper Bay tributaries are borderline or failing.

The thresholds below have been applied to the entire Bay to provide an assessment of chlorophyll-a in the Bay.  The following chlorophyll-a thresholds are applied to fixed sampling station data collected over the growing season of interest (i.e., March through September, not including June).

Spring (Mar, Apr, and May) thresholds (g L-1):                           

TF threshold ≤ 14          

OH threshold ≤ 20.9                       

MH threshold ≤ 6.2                                  

PH threshold ≤ 2.8

Summer (Jul, Aug, and Sep) thresholds (g L-1): 

TF threshold ≤ 12

OH threshold ≤ 9.5

MH threshold ≤ 7.7

PH threshold ≤ 4.5

Criteria Documentation, available at:

• Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries, April 2003, http://www.chesapeakebay.net/content.../cbp_13142.pdf

• Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries – 2004 Addendum, October 2004, http://www.chesapeakebay.net/content.../cbp_13268.pdf

• Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries – 2007 Chlorophyll Criteria Addendum, http://www.chesapeakebay.net/content.../cbp_20138.pdf

(11b) Why is it important to report this information?  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 in the Bay.

Therefore, chlorophyll-a concentrations are an important indicator of the magnitude of nutrient loading and potential hypoxia and anoxia in the Bay. 

(12b) What detail and/or diagnostic indicators are related to this reporting level indicator?  Spatially-explicit interpolation maps.

C. Temporal Considerations 

(13) Data Collection Date(s):  1985 through 2008

(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):  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 Bay-wide level.

(18) Are there geographic areas with missing data? If so, where?  Chlorophyll-a data are included from fixed station measurements in every segment of the Bay except for ANATF, CHOTF, CHSTF, HNGMH, LYNPH, NANOH, and POCOH.

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

(a) Chesapeake Bay (estuary)

(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.  

(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 nongovernment 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 workgroup scientists. 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.

(22) What is the process by which the raw data is summarized for development and presentation of the indicator?   Raw data are processed by a Fortran program developed by J. Keisman (UMCES/CBPO) to determine the aerial extent of compliance.  Chlorophyll-a data from each station are compared to the threshold values above and the percent of the total samples that are less than or equal to the appropriate threshold is determined.  Subsequently, the mean of the values calculated previously from all the stations in a segment is determined and these means are then area weighted to determine a Bay-wide value.  The formal protocol can be obtained by contacting Jeni Keisman.

(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model).  Fortran program is used to determine the aerial extent of compliance.

(24) Are the computations widely accepted as a scientifically sound?  Yes The methods for Chlorophyll a are the same as those for the Ecocheck Report Card Report Card:

http://www.eco-check.org/reportcard/...peake/methods/

specifically the document (Development of an Integrated and Spatially Explicit Index of Chesapeake Bay Health (Bay Habitat Health Index - BHHI))

(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. Station-level results were averaged at the segment-scale and segment-level scores were area-weighted when averaging up to the whole-bay level.

(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.  These are chlorophyll-a thresholds that were determined by Buchanan et al. (2005, Estuaries) and are used in the Phytoplankton Index of Biotic Integrity.  

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/qualityassurance.aspx.

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/qualityassurance.aspx.

(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/qualityassurance.aspx.

(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/qualityassurance.aspx.

(33) Do the uncertainty and variability impact the conclusions that can be inferred from the data and the utility of the indicator?  Yes.  Chlorophyll-a is highly variable both spatially and temporally and, therefore, there are limitations to how the data can be interpreted. 

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

G. Additional Information

(optional) 

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

Criteria Documentation, available at:

• Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries, April 2003, http://www.chesapeakebay.net/content.../cbp_13142.pdf

• Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries – 2004 Addendum, October 2004, http://www.chesapeakebay.net/content.../cbp_13268.pdf

• Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries – 2007 Chlorophyll Criteria Addendum, http://www.chesapeakebay.net/content.../cbp_20138.pdf

Page statistics
1004 view(s) and 1 edit(s)
Social share
Share this page?

Tags

This page has no custom tags.
This page has no classifications.

Comments

You must to post a comment.

Attachments