- Email: [email protected]
Critique regarding commentary on Mitsch et al. (2015)
G Model ECOENG 3608 No. of Pages 3
Ecological Engineering xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
Critique regarding commentary on Mitsch et al. (2015) Craig Diamond* Florida State University, The Balmoral Group, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 4 June 2015 Accepted 6 June 2015 Available online xxx
Recent work regarding the usefulness of mesocosms to examine rates of phosphorus retention has attracted commentary. While raising valid concerns about experimental design and the interpretation of results, the commentaries themselves are fraught with positions that cloud rather than clarify the underlying science. The authors in turn draw conclusions constrained by their own contributions to the discipline of Everglades restoration and fail to acknowledge the larger ecological and political context. ã2015 Elsevier B.V. All rights reserved.
Keywords: Everglades Stormwater treatment areas Phosphorus
1. Introduction In their paper titled “Protecting the Florida Everglades wetlands with wetlands: Can stormwater phosphorus be reduced to oligotrophic conditions?” Mitsch et al. (2015) presented results from a three-year mesocosm study intended to examine phosphorus dynamics in six different wetland communities that may potentially serve as polishing systems to further reduce phosphorus concentrations and thereby meet achieve statutory and courtordered water quality standards applicable to the Everglades. Comments regarding the paper have been submitted by Juston and Debusk (Draft, February, 2015) and Julian (n.d., 2015) to Ecological Engineering for its consideration and publication. The reviewers raise numerous valid concerns about the research methods and findings. However, while the comments serve to advance wetlands science by pointing to select deficiencies in experimental design and management, the comments appear weighted with other agenda that mask the fundamental intent and outcomes of the research. 2. Context Since the late 1800s, the hydrology and ecological integrity of Florida’s Everglades have been impacted by drainage practices; major canal, levee and road construction; habitat fragmentation; habitat conversion (to both agricultural and urban land uses); and the introduction of invasive exotics (plant and animal). As evidenced by historical mapping, aerial imagery and more recent remotely-sensed signatures, the remaining “everglades” includes
* Corresponding author. E-mail address: [email protected] (C. Diamond).
no more than 50 percent of the spatial extent of the original ecosystem mosaic. Compounding these hydrological modifications and changes in land use, the vegetative composition and habitat quality of the residual system has been further compromised by decades of stormwater runoff from the greater Everglades– Kissimmee–Okeechobee watershed. The runoff has been acknowledged to be nutrient-rich and to have impacted the historical, and largely oligotrophic, interior wetland systems south of Lake Okeechobee. Federal litigation to compel the State of Florida to enforce its own water quality standards set in motion a now twenty-year long process of acquiring declining agricultural properties and appurtenant lands to construct STAs and flow equalization basins (FEBs) within (or adjoining) the Everglades Agricultural Area (EAA) to achieve phosphorus standards believed to be protective of the Water Conservation Areas (WCAs) and ultimately Everglades National Park (see Fig. 1). The success of the current approach to the phosphorus loading problem is mixed: the STAs (and upstream agricultural field management practices) have reduced phosphorus entering the Everglades, but agreed-upon standards have yet to be reliably met, mixing zones (permitted by law) allow further dispersal of nutrients into the WCAs, and the ecosystem continues to exhibit signs of stress. Efforts to fulfill the conditions of litigation have necessitated further commitments for additional STA acreage and FEBs. Increased area for STAs ultimately translates into fewer acres under production within the EAA and associated runoff.1 In sum, the original plan to achieve the desired level of phosphorus was inadequate and a broader restoration response is
1 The STAs also treat water with elevated nutrients passed through the EAA from Lake Okeechobee.
http://dx.doi.org/10.1016/j.ecoleng.2015.06.002 0925-8574/ ã 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: C. Diamond, Critique regarding commentary on Mitsch et al. (2015), Ecol. Eng. (2015), http://dx.doi.org/ 10.1016/j.ecoleng.2015.06.002
G Model ECOENG 3608 No. of Pages 3
2
C. Diamond / Ecological Engineering xxx (2015) xxx–xxx
The research that is needed about phosphorus removal in the Everglades is multi-fold, including but not limited to the following questions:
Fig. 1. General locations of Stormwater Treatment Areas in context of Greater Everglades Watershed (from SFWMD). The mesocosms research adjoined STA-1W, outside of Water Conservation Area 1 (Arthur R Marshall Loxahatchee Nation.
warranted. However, opportunities to significantly expand areas within the EAA to support both treatment and ecosystem recovery are currently stymied by lack of political will.2 Such constraints on supplemental treatment acreage compel research to determine how best to use existing STAs. The subject research and commentaries need to be considered within this larger context to further reduce phosphorus loadings at specific points of discharge to the Everglades, as mandated by law. 3. Discussion The fundamental issue surrounding the subject research and commentary is whether wetlands have the capacity to achieve phosphorus levels consistent with Everglades resource protection. Histories of Everglades ecology establish that generalized oligotrophic conditions were achieved just beyond the southern edge of the EAA where peat soils tapered off over marl substrate and the periphyton communities were a larger component of the vegetative mosaic. Both the marl substrate and the periphyton are effective scavengers of phosphorus, and total phosphorus (TP) concentrations within the freshwater wetlands of Everglades National Park at the south end of the watershed were generally less than 10 ppb.3 So, the simple answer to the question is “Yes, wetlands can reduce phosphorus to oligotrophic conditions.” The challenge now is achieving this outcome in a context of reduced area of residual natural and semi-natural systems, but with hydraulic loading rates similar to historical flows, and phosphorus concentrations (and total loadings) that are greater than historical levels. The commentaries miss this key point and stray instead into (a) whose work provides what results in terms of contrasts of efficiency, scale, and retention between STAs and the experimental mesocosms, and (b) why the subject research fails to improve upon the commenters’ own past work. While earnest critique enhances opportunity to advance science, dismissing results without offering specific corrective measures does not. The collective discourse should be directed toward extracting what facts can be gleaned from the research and how they may be applied to unresolved matters.
2 The State of Florida and the South Florida Water Management District (SFWMD) are in the position of letting options to acquire thousands of acres within the EAA expire, despite funding availability; as of June 2015 the District Governing Board has declined to purchase said properties. 3 State and Federal agency documents frequently report historical concentrations of TP averaging 6 ppb.
How long a flow path is required for specific reductions in phosphorus concentrations? How should such flow paths vary in length to accommodate variation in hydraulic loading? What wetland vegetation complex (e.g., Emergent, Floating, Submerged) achieves what reduction in phosphorus concentrations? How do these rates of reduction vary with the inflow concentration? Can such specific wetland vegetation complexes be maintained over distance, over various soil/geological substrates, and over phosphorus gradients? Must vegetation be managed for end results, or does “selfdesign” maximize phosphorus uptake rates? What soil substrate(s) provide optimal conditions for which wetland vegetation complex? Does soil history (i.e., past use) constrain retention rates? What are the maturation and stabilization periods for treatment system? What is the minimum period of experimentation necessary to provide a reliable trajectory and probably endpoint for phosphorus uptake? Where should “polishing” systems be located in the larger context of water quality objectives? The subject research touches on several of these questions, but fails to answer any fully. The commentary by Julian points fairly to experimental design and management decisions (and flaws) that contribute to these failures, which could have been controlled for more adequately and which would have provided more robust answers about the behaviors of the mesocosms themselves. Juston and DeBusk do state that Mitsch adds to the knowledge base of aquatic metabolism (and specific phosphorus dynamics) but the work does not establish a basis for any particular phosphorus removal design. In sum, the commentary does not refute Mitsch’s contention that wetlands can be designed for success, but that the research as carried out does not take us to that endpoint. I would concur that the analytical framework was so broad as to not provide sufficient control over the various conflating parameters to target tightly any of the above questions. However, the tenor of both sets of comments is that the mesocosm experiment is offered somehow as an unwelcome replacement for, or a re-design of, the STAs themselves when that is not the case. Both sets of comments laud the effectiveness of existing Stormwater Treatment Areas (STAs) in removing phosphorus from runoff in South Florida, report that such field-scale systems outperform the test mesocosms, and suggest that the subject research does not provide a testable basis for further reductions in phosphorus. To reframe that criticism, despite the merits of the STAs, both commentaries note that lower phosphorus concentrations are still required. Consequently, it is important to be mindful that the subject research was tendered as an enhancement to existing practice, accepting the dependent role of a “back-end” system. On the point of trajectories of phosphorus retention in treatment wetlands, both spatially and temporally, Juston and DeBusk compare the phosphorus retention behaviors of two STAs (2 and 3/4) with that of the mesocosms and conclude that the in situ systems are more effective. However, the retention rate for the self-described “back-end” component of STA-2 is inferred from a model and not measured. Inflow loads at the half-way point of the flow-path may have been higher or lower than estimated,
Please cite this article in press as: C. Diamond, Critique regarding commentary on Mitsch et al. (2015), Ecol. Eng. (2015), http://dx.doi.org/ 10.1016/j.ecoleng.2015.06.002
G Model ECOENG 3608 No. of Pages 3
C. Diamond / Ecological Engineering xxx (2015) xxx–xxx
rendering the numerical contrast of efficiency pointless. Further, as the critical metric from a legal perspective is just the concentration of total phosphorus (Julian), the effectiveness of the periphyton (field scale) demonstration site is in fact less than that of the mesocosm (for Nymphaea), despite having a longer period of operation in which to stabilize both vegetation and soils. In fairness to Mitsch, both sets comments suggest that the mesocosms likely received greater dosing of non-labile phosphorus, constraining uptake rates. The conclusion by Mitsch about the wetland area needed to achieve 10 ppb total phosphorus drew attention by both commenters. As suggested above, additional acreage has become more a political issue than an economic one. Caution is warranted on all sides of the argument. Acreage for FEBs and nominal expansion of STAs has been agreed to by the litigants, so some improvement in TP numbers at points of discharge is anticipated. Mitsch’s conclusion itself should be limited by (a) comparison between the retention rates of the mesocosm and those of STA-1W only, a weak performer among the STAs, and (b) the more generalized STA discharge values for TP, which are less than the 30 ppb used for his calculation. With those caveats in mind a more supportable conclusion would be (conservatively) that several times the current SAV-dominated acreage within the STAs, not the gross acreage of the STAs themselves, will be needed to meet 10 ppb. Where to place this acreage and how best to configure it remain unexplored by the dialog. The decades-long debate over how much land is needed to restore the remnant Everglades includes hydrological, ecological and water quality components. A conclusion that several hundred thousand acres (i.e., ten times the STA acreage and roughly half of the acreage of the EAA) to achieve a single water quality objective may embolden some but also undermines more serious discussion about redesigning the greater Everglades in the context of the Federal litigation, the Comprehensive Everglades Restoration Program (CERP), the Central Everglades Planning Project (CEPP) and related initiatives aimed at mitigating or reversing the fundamental impacts outlined in the Context of this critique. Their own shortcomings aside, the commentaries are largely correct in explaining that the subject research has not demonstrated conclusively that SAV/FAV systems are sufficient to reliably reduce phosphorus concentrations from EAV dominated facilities to the threshold required for Everglades protection. The fundamental touchstone – 10 ppb total phosphorus – was not achieved by the study. However, the research does point to the more complicated dynamics of phosphorus in well-managed and lessthan-well managed systems and adds to the collective position held by affected government agencies, contractors, and nongovernmental advocacy organizations that an oligotrophic system in the Everglades can be attained with sufficient treatment area, ecological management and upstream cooperation. Science is still needed to help craft an effective complement to the STAs that will
3
be appropriately tuned to the spectrum of substrates in the southern EAA and inherent successional pressures in south Florida freshwater wetlands. 4. Closing remarks This critique is offered in support of sound science and the application of ecological principles to resolve environmental challenges. The author recommends that those interested in the dynamics of phosphorus in managed systems read the original paper and the offered comments before accepting or drawing conclusions about the use mesocosms in experimental design or the possibility of achieving oligotrophic conditions in Everglades wetlands. 5. Disclosure of conflict of interest The author is unaffiliated with Florida Gulf Coast University (the host institution for the original paper), the Everglades Agricultural Area Environmental Protection District (a special district supported primarily by agricultural landowner fees) or by the Florida Department of Environmental Protection (the state agency with final authority for enforcing water quality standards established under the Everglades Forever Act). The author was associated with the University of Florida Center for Wetlands (1982–1985); served as faculty in natural resources sciences within the Florida State University System (1985–2009); conducted research on wetlands reclamation and aquatic plant management, the economics of water and water management in South Florida, and the effects of climate change on Everglades hydrology and productivity; and taught graduate courses on the subjects of water resources and the Everglades. The author has provided peer review for wetlands studies conducted for the Florida Institute for Phosphate Research. The author is an unpaid volunteer with the Sierra Club, one of the co-plaintiffs in the original Federal lawsuit that has been responsible for the implementation of the STA and phosphorus reduction programs in the Everglades, and was present at the earliest litigation planning discussions held at the offices of the US Attorney General for the Southern District of Florida. References Julian, P., 2015. Commentary on Mitsch et al. (2015). Protecting the Florida Everglades wetlands with wetlands: can stormwater phosphorus be reduced to oligotrophic conditions?. Juston, J., DeBusk T., 2015. Comment on protecting the Florida Everglades wetlands with wetlands: can stormwater phosphorus be reduced to oligotrophic conditions? by W. Mitsch et al. February 2015. Mitsch, W.J., Zhang, L., Marois, D., Song, K., 2015. Protecting the Florida Everglades wetlands with wetlands: can stormwater phosphorus be reduced to oligotrophic conditions. Ecol. Eng. 80, 8–19.
Please cite this article in press as: C. Diamond, Critique regarding commentary on Mitsch et al. (2015), Ecol. Eng. (2015), http://dx.doi.org/ 10.1016/j.ecoleng.2015.06.002
Ecological Engineering xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
Critique regarding commentary on Mitsch et al. (2015) Craig Diamond* Florida State University, The Balmoral Group, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 4 June 2015 Accepted 6 June 2015 Available online xxx
Recent work regarding the usefulness of mesocosms to examine rates of phosphorus retention has attracted commentary. While raising valid concerns about experimental design and the interpretation of results, the commentaries themselves are fraught with positions that cloud rather than clarify the underlying science. The authors in turn draw conclusions constrained by their own contributions to the discipline of Everglades restoration and fail to acknowledge the larger ecological and political context. ã2015 Elsevier B.V. All rights reserved.
Keywords: Everglades Stormwater treatment areas Phosphorus
1. Introduction In their paper titled “Protecting the Florida Everglades wetlands with wetlands: Can stormwater phosphorus be reduced to oligotrophic conditions?” Mitsch et al. (2015) presented results from a three-year mesocosm study intended to examine phosphorus dynamics in six different wetland communities that may potentially serve as polishing systems to further reduce phosphorus concentrations and thereby meet achieve statutory and courtordered water quality standards applicable to the Everglades. Comments regarding the paper have been submitted by Juston and Debusk (Draft, February, 2015) and Julian (n.d., 2015) to Ecological Engineering for its consideration and publication. The reviewers raise numerous valid concerns about the research methods and findings. However, while the comments serve to advance wetlands science by pointing to select deficiencies in experimental design and management, the comments appear weighted with other agenda that mask the fundamental intent and outcomes of the research. 2. Context Since the late 1800s, the hydrology and ecological integrity of Florida’s Everglades have been impacted by drainage practices; major canal, levee and road construction; habitat fragmentation; habitat conversion (to both agricultural and urban land uses); and the introduction of invasive exotics (plant and animal). As evidenced by historical mapping, aerial imagery and more recent remotely-sensed signatures, the remaining “everglades” includes
* Corresponding author. E-mail address: [email protected] (C. Diamond).
no more than 50 percent of the spatial extent of the original ecosystem mosaic. Compounding these hydrological modifications and changes in land use, the vegetative composition and habitat quality of the residual system has been further compromised by decades of stormwater runoff from the greater Everglades– Kissimmee–Okeechobee watershed. The runoff has been acknowledged to be nutrient-rich and to have impacted the historical, and largely oligotrophic, interior wetland systems south of Lake Okeechobee. Federal litigation to compel the State of Florida to enforce its own water quality standards set in motion a now twenty-year long process of acquiring declining agricultural properties and appurtenant lands to construct STAs and flow equalization basins (FEBs) within (or adjoining) the Everglades Agricultural Area (EAA) to achieve phosphorus standards believed to be protective of the Water Conservation Areas (WCAs) and ultimately Everglades National Park (see Fig. 1). The success of the current approach to the phosphorus loading problem is mixed: the STAs (and upstream agricultural field management practices) have reduced phosphorus entering the Everglades, but agreed-upon standards have yet to be reliably met, mixing zones (permitted by law) allow further dispersal of nutrients into the WCAs, and the ecosystem continues to exhibit signs of stress. Efforts to fulfill the conditions of litigation have necessitated further commitments for additional STA acreage and FEBs. Increased area for STAs ultimately translates into fewer acres under production within the EAA and associated runoff.1 In sum, the original plan to achieve the desired level of phosphorus was inadequate and a broader restoration response is
1 The STAs also treat water with elevated nutrients passed through the EAA from Lake Okeechobee.
http://dx.doi.org/10.1016/j.ecoleng.2015.06.002 0925-8574/ ã 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: C. Diamond, Critique regarding commentary on Mitsch et al. (2015), Ecol. Eng. (2015), http://dx.doi.org/ 10.1016/j.ecoleng.2015.06.002
G Model ECOENG 3608 No. of Pages 3
2
C. Diamond / Ecological Engineering xxx (2015) xxx–xxx
The research that is needed about phosphorus removal in the Everglades is multi-fold, including but not limited to the following questions:
Fig. 1. General locations of Stormwater Treatment Areas in context of Greater Everglades Watershed (from SFWMD). The mesocosms research adjoined STA-1W, outside of Water Conservation Area 1 (Arthur R Marshall Loxahatchee Nation.
warranted. However, opportunities to significantly expand areas within the EAA to support both treatment and ecosystem recovery are currently stymied by lack of political will.2 Such constraints on supplemental treatment acreage compel research to determine how best to use existing STAs. The subject research and commentaries need to be considered within this larger context to further reduce phosphorus loadings at specific points of discharge to the Everglades, as mandated by law. 3. Discussion The fundamental issue surrounding the subject research and commentary is whether wetlands have the capacity to achieve phosphorus levels consistent with Everglades resource protection. Histories of Everglades ecology establish that generalized oligotrophic conditions were achieved just beyond the southern edge of the EAA where peat soils tapered off over marl substrate and the periphyton communities were a larger component of the vegetative mosaic. Both the marl substrate and the periphyton are effective scavengers of phosphorus, and total phosphorus (TP) concentrations within the freshwater wetlands of Everglades National Park at the south end of the watershed were generally less than 10 ppb.3 So, the simple answer to the question is “Yes, wetlands can reduce phosphorus to oligotrophic conditions.” The challenge now is achieving this outcome in a context of reduced area of residual natural and semi-natural systems, but with hydraulic loading rates similar to historical flows, and phosphorus concentrations (and total loadings) that are greater than historical levels. The commentaries miss this key point and stray instead into (a) whose work provides what results in terms of contrasts of efficiency, scale, and retention between STAs and the experimental mesocosms, and (b) why the subject research fails to improve upon the commenters’ own past work. While earnest critique enhances opportunity to advance science, dismissing results without offering specific corrective measures does not. The collective discourse should be directed toward extracting what facts can be gleaned from the research and how they may be applied to unresolved matters.
2 The State of Florida and the South Florida Water Management District (SFWMD) are in the position of letting options to acquire thousands of acres within the EAA expire, despite funding availability; as of June 2015 the District Governing Board has declined to purchase said properties. 3 State and Federal agency documents frequently report historical concentrations of TP averaging 6 ppb.
How long a flow path is required for specific reductions in phosphorus concentrations? How should such flow paths vary in length to accommodate variation in hydraulic loading? What wetland vegetation complex (e.g., Emergent, Floating, Submerged) achieves what reduction in phosphorus concentrations? How do these rates of reduction vary with the inflow concentration? Can such specific wetland vegetation complexes be maintained over distance, over various soil/geological substrates, and over phosphorus gradients? Must vegetation be managed for end results, or does “selfdesign” maximize phosphorus uptake rates? What soil substrate(s) provide optimal conditions for which wetland vegetation complex? Does soil history (i.e., past use) constrain retention rates? What are the maturation and stabilization periods for treatment system? What is the minimum period of experimentation necessary to provide a reliable trajectory and probably endpoint for phosphorus uptake? Where should “polishing” systems be located in the larger context of water quality objectives? The subject research touches on several of these questions, but fails to answer any fully. The commentary by Julian points fairly to experimental design and management decisions (and flaws) that contribute to these failures, which could have been controlled for more adequately and which would have provided more robust answers about the behaviors of the mesocosms themselves. Juston and DeBusk do state that Mitsch adds to the knowledge base of aquatic metabolism (and specific phosphorus dynamics) but the work does not establish a basis for any particular phosphorus removal design. In sum, the commentary does not refute Mitsch’s contention that wetlands can be designed for success, but that the research as carried out does not take us to that endpoint. I would concur that the analytical framework was so broad as to not provide sufficient control over the various conflating parameters to target tightly any of the above questions. However, the tenor of both sets of comments is that the mesocosm experiment is offered somehow as an unwelcome replacement for, or a re-design of, the STAs themselves when that is not the case. Both sets of comments laud the effectiveness of existing Stormwater Treatment Areas (STAs) in removing phosphorus from runoff in South Florida, report that such field-scale systems outperform the test mesocosms, and suggest that the subject research does not provide a testable basis for further reductions in phosphorus. To reframe that criticism, despite the merits of the STAs, both commentaries note that lower phosphorus concentrations are still required. Consequently, it is important to be mindful that the subject research was tendered as an enhancement to existing practice, accepting the dependent role of a “back-end” system. On the point of trajectories of phosphorus retention in treatment wetlands, both spatially and temporally, Juston and DeBusk compare the phosphorus retention behaviors of two STAs (2 and 3/4) with that of the mesocosms and conclude that the in situ systems are more effective. However, the retention rate for the self-described “back-end” component of STA-2 is inferred from a model and not measured. Inflow loads at the half-way point of the flow-path may have been higher or lower than estimated,
Please cite this article in press as: C. Diamond, Critique regarding commentary on Mitsch et al. (2015), Ecol. Eng. (2015), http://dx.doi.org/ 10.1016/j.ecoleng.2015.06.002
G Model ECOENG 3608 No. of Pages 3
C. Diamond / Ecological Engineering xxx (2015) xxx–xxx
rendering the numerical contrast of efficiency pointless. Further, as the critical metric from a legal perspective is just the concentration of total phosphorus (Julian), the effectiveness of the periphyton (field scale) demonstration site is in fact less than that of the mesocosm (for Nymphaea), despite having a longer period of operation in which to stabilize both vegetation and soils. In fairness to Mitsch, both sets comments suggest that the mesocosms likely received greater dosing of non-labile phosphorus, constraining uptake rates. The conclusion by Mitsch about the wetland area needed to achieve 10 ppb total phosphorus drew attention by both commenters. As suggested above, additional acreage has become more a political issue than an economic one. Caution is warranted on all sides of the argument. Acreage for FEBs and nominal expansion of STAs has been agreed to by the litigants, so some improvement in TP numbers at points of discharge is anticipated. Mitsch’s conclusion itself should be limited by (a) comparison between the retention rates of the mesocosm and those of STA-1W only, a weak performer among the STAs, and (b) the more generalized STA discharge values for TP, which are less than the 30 ppb used for his calculation. With those caveats in mind a more supportable conclusion would be (conservatively) that several times the current SAV-dominated acreage within the STAs, not the gross acreage of the STAs themselves, will be needed to meet 10 ppb. Where to place this acreage and how best to configure it remain unexplored by the dialog. The decades-long debate over how much land is needed to restore the remnant Everglades includes hydrological, ecological and water quality components. A conclusion that several hundred thousand acres (i.e., ten times the STA acreage and roughly half of the acreage of the EAA) to achieve a single water quality objective may embolden some but also undermines more serious discussion about redesigning the greater Everglades in the context of the Federal litigation, the Comprehensive Everglades Restoration Program (CERP), the Central Everglades Planning Project (CEPP) and related initiatives aimed at mitigating or reversing the fundamental impacts outlined in the Context of this critique. Their own shortcomings aside, the commentaries are largely correct in explaining that the subject research has not demonstrated conclusively that SAV/FAV systems are sufficient to reliably reduce phosphorus concentrations from EAV dominated facilities to the threshold required for Everglades protection. The fundamental touchstone – 10 ppb total phosphorus – was not achieved by the study. However, the research does point to the more complicated dynamics of phosphorus in well-managed and lessthan-well managed systems and adds to the collective position held by affected government agencies, contractors, and nongovernmental advocacy organizations that an oligotrophic system in the Everglades can be attained with sufficient treatment area, ecological management and upstream cooperation. Science is still needed to help craft an effective complement to the STAs that will
3
be appropriately tuned to the spectrum of substrates in the southern EAA and inherent successional pressures in south Florida freshwater wetlands. 4. Closing remarks This critique is offered in support of sound science and the application of ecological principles to resolve environmental challenges. The author recommends that those interested in the dynamics of phosphorus in managed systems read the original paper and the offered comments before accepting or drawing conclusions about the use mesocosms in experimental design or the possibility of achieving oligotrophic conditions in Everglades wetlands. 5. Disclosure of conflict of interest The author is unaffiliated with Florida Gulf Coast University (the host institution for the original paper), the Everglades Agricultural Area Environmental Protection District (a special district supported primarily by agricultural landowner fees) or by the Florida Department of Environmental Protection (the state agency with final authority for enforcing water quality standards established under the Everglades Forever Act). The author was associated with the University of Florida Center for Wetlands (1982–1985); served as faculty in natural resources sciences within the Florida State University System (1985–2009); conducted research on wetlands reclamation and aquatic plant management, the economics of water and water management in South Florida, and the effects of climate change on Everglades hydrology and productivity; and taught graduate courses on the subjects of water resources and the Everglades. The author has provided peer review for wetlands studies conducted for the Florida Institute for Phosphate Research. The author is an unpaid volunteer with the Sierra Club, one of the co-plaintiffs in the original Federal lawsuit that has been responsible for the implementation of the STA and phosphorus reduction programs in the Everglades, and was present at the earliest litigation planning discussions held at the offices of the US Attorney General for the Southern District of Florida. References Julian, P., 2015. Commentary on Mitsch et al. (2015). Protecting the Florida Everglades wetlands with wetlands: can stormwater phosphorus be reduced to oligotrophic conditions?. Juston, J., DeBusk T., 2015. Comment on protecting the Florida Everglades wetlands with wetlands: can stormwater phosphorus be reduced to oligotrophic conditions? by W. Mitsch et al. February 2015. Mitsch, W.J., Zhang, L., Marois, D., Song, K., 2015. Protecting the Florida Everglades wetlands with wetlands: can stormwater phosphorus be reduced to oligotrophic conditions. Ecol. Eng. 80, 8–19.
Please cite this article in press as: C. Diamond, Critique regarding commentary on Mitsch et al. (2015), Ecol. Eng. (2015), http://dx.doi.org/ 10.1016/j.ecoleng.2015.06.002