WATER RESOURCES RESEARCH, VOL. 49, 2312–2313, doi:10.1002/wrcr.20162, 2013
Comment on ‘‘Spatial and temporal phosphorus distribution changes in a large wetland ecosystem’’ by X. Zapata-Rios et al. Paul Julian II1 Received 21 November 2012; accepted 22 February 2013; published 27 March 2013.
Citation: Julian, P. II (2013), Comment on ‘‘Spatial and temporal phosphorus distribution changes in a large wetland ecosystem’’ by X. Zapata-Rios et al., Water Resour. Res., 49, 2312–2313, doi:10.1002/wrcr.20162.
[1] I commend the author at their novel analysis and approach with the use of advanced geo-statistical tools to provide both spatial and temporal trends of surface water total phosphorus within the Everglades Protection Area (EvPA). However, several aspects of the manuscript lack information such as data screening technique, data manipulation techniques, and the interpretation of the State of Florida, class III total phosphorus (TP) water quality criteria were established for the EvPA. The primary purpose of this commentary is not to discount the author’s work which is a very interesting way at looking at environmental data and provides some useful insight into the correlation of water depth and total phosphorous concentrations. However, the application of regulatory water quality limits to data not originally intended to be used is problematic, which the authors do not address. [2] The use of multiple data sets to answer complex question is a hard thing to do, especially when data sets are not originally intended to be combined. Even though standard sampling and analysis methods exist data sets may differ according to slight variations in collections methods (i.e., pump, bailer, niskin, etc.) or laboratory analysis. Zapata-Rios et al. [2012] do not explicitly state the methods used to collect samples, which could have profound effect on the data distribution and statistical outcomes, especially related to total phosphorous in surface water within the Everglades (South Florida Water Management District, unpublished data, 2012). Furthermore, the authors do not address the screening protocol employed for laboratory or field sampling qualifiers which could influence the integrity of the data and the values reported. These qualifiers include improperly preserved samples, analysis was not performed within the acceptable window, error associated with control standards or replication or data was estimated with a lower accuracy method [Julian et al., 2013]. Moreover, additional data screening is required when assessing surface water TP in the EvPA [Payne and Weaver, 2007].
1
4003 Chinook St., Tallahassee, Florida, USA.
Corresponding author: P. Julian, 4003 Chinook St., Tallahassee, FL 32303, USA. (
[email protected]) This article is a comment on X. Zapata-Rios et al., doi:10.1029/ 2011WR011421. ©2013 American Geophysical Union. All Rights Reserved. 0043-1397/13/10.1002/wrcr.20162
[3] It is understood that excessive nutrient loading to a particular water body can effect cause an ecological imbalance within algal and plant communities [Gaiser et al., 2006], therefore a United States Environmental Protection Agency (U.S. EPA) approved numeric TP water quality criteria for class III water bodies was developed by the State of Florida [Florida Administrative Code, 2004]. The state of Florida defines class III water bodies as water bodies that fulfill recreation, propagation and maintenance of a healthy, well-balanced population of fish and wildlife [Florida Administrative Code, 2010] and attainment of the water quality criterion ensures that the water body is protected and fulfils its designation. The authors reference the Everglades Forever Act (EFA) amended determination which describes a two-part WQBEL as a critical component of an enforceable framework that ensures that stormwater treatment area (STA) discharges will not cause exceedances of the Class III TP numeric nutrient criteria within the EvPA. The Class III TP numeric nutrient criteria within the EvPA is a multipart criteria involving the assessment of defined high phosphorous impact and unimpacted areas within the EvPA marsh and is assessed in a five water year moving window [Florida Administrative Code, 2004]. As part of the EFA amended determination, a two part Water Quality Based Effluent Limit (WQBEL) was proposed by the U.S. EPA which includes a 10 mg/L annual geometric mean (GM) in more than 2 consecutive years or a 18 mg/L annual flow weighted mean (FWM) TP concentration from each respective STA. However, the limits defined by the U.S. EPA Amended Determination are not applicable as the South Florida Water Management District with support from Florida Department of Environmental Protection has developed an equally as rigorous, if not more rigorous WQBEL. The stated developed and U.S. EPA approved WQBEL, much like the proposed federal WQBEL involves two parts, the first requires that the discharge for each STA may not exceed an annual FWM of 13 mg/L in more than three out of five years and second requires an annual FWM of 19 mg/L for each STA discharge [South Florida Water Management District, 2012a]. [4] It is unclear which 10 mg/L limit Zapata-Rios et al. [2012] is referencing but if it is assumed that the Class III limit defined in 62–302.530 Florida Administrative Code (F.A.C.) [Florida Administrative Code, 2004] is applied then attainment of the criterion is achieved if the 5 water year (1 May to 30 April) GM averaged across all station is less than or equal to 10 mg/L within each respective category (impacted and unimpacted) in conjunction with three
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other assessments. This limit was developed using a combination of biological, water and sediment quality data in a change point analysis similar to analysis presented by Song et al. [2003]. The established water quality criterion is deemed protective to aquatic life in that if stations achieve the all parts of the criterion then those areas should fulfill the intended use of the water body. Therefore, the utilization of the 10 mg/L limit to assess the surface water TP condition was improperly applied. This is due to the application of the 10 mg/L limit across a broad spatial extent (i.e., EvPA and Everglades National Park [ENP]) not taking into account impacted and unimpacted regions of the marsh within each compartment, the long temporal scale of the assessment stretch from 1995 to 2007, the water quality interpolated surface data is limited to approximately five-year time steps and spans several months and not the entire water year. [5] Zapata-Rios et al. [2012] also compared TP surface water conditions using the 15 mg/L limit defined in 62– 302.530 F.A.C. [Florida Administrative Code, 2004]. Much like the 5 year 10 mg/L limit, the 15 mg/L limit is a part of the overall water quality criterion and attainment is achieved when an annual GM at all individual stations is less than or equal to 15 mg/L. Hypothetically, the interpolated TP data could be compared with this limit if each cell was assumed to be an individual sampling station with impacted and unimpacted regions identified. However, compliance with the criterion is assessed on an annual basis and requires a minimum number of data points distributed between the wet and dry season [Payne and Weaver, 2007]. [6] When using water quality criteria developed within the environmental regulatory framework attention should be given to how the method was developed, the time period of assessment, and the implications of using data not originally intended for assessment of water quality criteria attainment. Overall Zapata-Rios et al. [2012] demonstrate long-term (1995–2007) improvement in surface water TP concentrations within the EvPA and ENP, especially during the dry season with large areas with less than 50 mg/L decrease in concentrations. This improvement could be attributed to improvements in best management practices,
tighter regulatory action, better ecosystem management and the construction and completion of the Everglades STAs and other Everglades restoration projects [Julian et al., 2013]. Portions of the EvPA are still considered impacted, however conditions continue to improve with additional improvement possible with the anticipated completion of projects outlined within the State of Florida restoration strategies [Julian et al., 2013; South Florida Water Management District, 2012b]. [7] Acknowledgments. I would like to thank Ernie Marks and Frank Nearhoof for there review and useful comments on a draft of this manuscript.
References Florida Administrative Code (2004), 62-302.540 Water Quality Standards for Phosphorus within the Everglades Area, Florida Department of Environmental Protection, Tallahassee, Fla. Florida Administrative Code (2010), 62-302.400 Classification of Surface Waters, Usage, Reclassification, Classified Waters, Florida Department of Environmental Protection, Tallahassee, Fla. Gaiser, E. E., D. L. Childers, R. D. Jones, J. H. Richards, L. J. Scinto, and J. C. Trexler (2006), Periphyton responses to eutrophication in the Florida Everglades: Cross-system patterns of structural and compositional change, Limnol. Oceanogr., 51, 617–630. Julian II, P., G. Payne, and S. Xue (2013), Status of water quality in the Everglades protection area, in South Florida Environmental Report, chap. 3A, pp. 1–42, South Florida Water Management District, West Palm Breach, Fla. Payne, G., and K. Weaver (2007), Appendix 3C-1 Calculation of annual and five-year geometric mean total phosphorus concentrations to assess achievement of the phosphorus criteria for the Everglades protection area, in South Florida Environmental Report, append 3C-1, pp. 1–3, South Florida Water Management District, West Palm Beach, Fla. Song, S. Q, R. S. King, C. J. Richardson (2003), Two statistical methods for the detection of environmental thresholds, Ecol. Modell., 166, 87–97. South Florida Water Management District (2012a), Technical Support Document for Derivation of the Water Quality Effluent Limit for Total Phosphorous in Discharge form Everglades Stormwater Treatment Areas to the Everglades Protection Area, West Palm Beach, Fla. South Florida Water Management District (2012b), Restoration Strategies Regional Water Quality Plan, West Palm Beach, Fla. U.S. Environmental Protection Agency (2010), United States Environmental Protection Agency Amended Determination Report, Atlanta, Ga. Zapata-Rios, X., R. G. Rivero, G. M., Naja and P. Goovaerts (2012), Spatial and temporal phosphorous distribution changes in a large wetland ecosystem, Water Resour. Res., 48, W09512, doi:10.1029/2011WR011421.
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