Advancing the Science of Environmental Flow Management for Protection of Temporarily Closed Estuaries and Coastal Lagoons
Round 1
Reviewer 1 Report
The ecohydrology of transition environments, like temporarily closed estuaries and coastal lagoons, is summarized to propose a research program aimed at a better understanding of ecological and geomorphic responses to their altered flow regimes. For this purpose, many factors are considered, as estuarine typology, land use/ocean forcing factors, climate change, etc., to address adaptive management through long-term monitoring and assessment of these sensitive environments. Case studies of Mediterranean climate-type regions and ocean coastlands are discussed and considered for formulating a decalogue of implementing estuarine ecological flows in adaptive management.
The manuscript is well structured, figures and tables are clear, references are pertinent and numerous. The conclusion and suggested recommendations aim to advance environmental protection and restoration.
The authors also argue about coastal lagoons, as well as the title suggests. However, the scheme of Figure 3 shows a mainly continental fluvial-coastal environment. I suggest modifying or substituting it with a schematic figure of a lagoon-dune-beach system, considering that Congxian and Ping 1991, Sedim. Geol. 72 - already classified the Quaternary coastal lagoons as closed, partially closed, and open lagoons due to the different morphodynamic balance between the mainland and marine processes.
Author Response
Reviewer 1
The manuscript is well structured, figures and tables are clear, references are pertinent and numerous. The conclusion and suggested recommendations aim to advance environmental protection and restoration.
Response: Thank you for the overall positive reaction and comments
The authors also argue about coastal lagoons, as well as the title suggests. However, the scheme of Figure 3 shows a mainly continental fluvial-coastal environment. I suggest modifying or substituting it with a schematic figure of a lagoon-dune-beach system
Response: We have revised Figure 3 to better illustrate the lagoonal nature and the dune strand elements of the archetypal TCE illustrated by the graphic. We would also like to point out that the figure is meant to depict features that may be present in some TCEs, but likely are not found in all TCEs. The graphic is not meant to represent all TCE types discussed in the manuscript.
Reviewer 2 Report
The manuscript by Stein et al., “Advancing the Science of Environmental Flow Management for Protection of Temporarily Closed Estuaries (TCE’s) and Coastal Lagoons aims to present a synthesis of the current knowledge of the ecohydrology in TCEs and coastal lagoons and identify key knowledge gaps in our understanding of ecological responses to altered flow regimes in TCEs. In doing so, it addresses a much-needed area of environmental flow management of estuarine environments. Such environments pose significant management challenges from a range of pressures, including the modification of flow regimes that alter the freshwater inputs to these systems.
This is generally a nicely written paper that has some interesting summary material, but often falls short of offering something new and exciting to the field. I was frequently a bit disappointed that the logical step on from simply compiling information hadn’t been undertaken and I feel it requires a bit more thought and a little stronger structure to make this a really valuable paper.
Section 2 is headed as being a framework for establishing research priorities. Essentially, it appears that the authors believe that there are fundamental flaws in existing frameworks that prevent them from being useful, but aside from identifying areas where the frameworks could be improved, it does not provide a critical evaluation of the current suite of frameworks. I was also expecting this this section would provide a framework that is used throughout the remainder of the manuscript to establish the research priorities. It does, but the link is not explicitly made between the framing in this section and the rest of the manuscript. The framework doesn’t guide research priorities, it helps to identify knowledge gaps that then can be prioritised. This section needs some reworking to clearly articulate the point the Authors are trying to make.
I worry about the recommendation to generate yet another typology/classification scheme. The scientific literate is replete with classifications schemes for such environments (one only has to look to the wetland literature which, to some degree, overlaps with the TCE literature). I am not convinced that another generic classification scheme would offer environmental flow managers or those attempting to provide environmental flows for TCE outcomes anything that a site-specific evaluation would not provide. I also suspect that the desire to have a typology that is “inclusive of all estuaries that could be subject to environmental flow requirements, yet robust enough to accommodate the characteristics of individual systems” is a pipe dream and we need to consider how we might better use a generic framework for eflow evaluation across a range of specific estuary types. Otherwise we could spend yet more years where the science is focussed on classification, not on understanding the eco-hydrology relationships needed to better manage the system.
I refer the authors to Kath, J., Boulton, A.J., Harrison, E.T. and Dyer, F.J., 2018. A conceptual framework for ecological responses to groundwater regime alteration (FERGRA). Ecohydrology, 11(7), p.e2010 where the authors, instead of looking to further divide existing classes of GDE’s, look for commonalities that may be useful in understanding knowledge gaps and managing groundwater dependent ecosystems. Groundwater dependent ecosystems are similar to estuarine environments in their complexity and lack of investment in understanding and managing.
The need to better incorporate information from different temporal scales is a theme throughout the manuscript yet it is not well drawn out. The thing that makes estuaries different from (say) end of system wetlands or floodplain wetlands is the interplay between fresh and salt water (river flow and tidal flow to use the language of the manuscript). This means that a structured assessment of flows at different temporal scales is needed from sub daily (tidal cycles) to long term regimes. This point is poorly made in the manuscript. Table 1 does not link well to the text which makes the case (albeit in passing – lines 276-278) that estuary environmental flow assessments should be simulated at hourly or daily time steps. It would have been nice to see a better structured Table 1 which focussed on the temporal scale of the hydrological knowledge needs. Instead the table focusses on the flow components which doesn’t help this section address the specific needs of estuaries.
The need to also consider temporal scales in establishing expectations or desired conditions is missed from this manuscript and I would argue it is particularly important in estuaries. The spatial and temporal complexity of TCEs across multiple levels of ecological organisation makes establishing expectations or desired conditions a significant challenge. As with wetlands, objectives and targets are often static indicators (a single “desired state”) and fail to take into account the importance of spatial or temporal variation in population or community structure, or composition which may be functionally significant.
The manuscript essentially provides a shopping list of 34 knowledge gaps that if filled will advance our understanding of ecological responses to altered flow regimes in TCEs. It then disappointingly fails to then take these knowledge gaps and prioritise them to help investors and researchers. Of these identified– which are the most important – and how would you go about determining which are most important?? Many are a huge task – and lead to a research agenda that would take squillions of dollars and tens of years to deliver. This is not going to happen and we need to be starting to manage better now. How can we get smarter at addressing such massive knowledge gaps to better inform environmental flow management?? This is where I think the authors could turn a rather pedestrian piece into something of significant value to the scientific community and it just falls short.
Grammar and expression
I note that the phrase ‘due to’ is often incorrectly used. ‘Due to’ should be used to modify a noun and preceded by a form of the verb ‘to be’. Consider replacing most with because of or revising the sentences to use it correctly.
Line 69: the phrase ‘high levels of ecosystem function’ is odd. They either provide significant ecosystem functions or many ecosystem functions.
Line 72: ‘the effects of’ not just ‘effect of’
Line 79: don’t need to re-define TCE’s – they have been defined previously
Line 677: TCE estuaries – estuaries is repeated.
Author Response
Reviewer 2
This is generally a nicely written paper that has some interesting summary material, but often falls short of offering something new and exciting to the field. I was frequently a bit disappointed that the logical step on from simply compiling information hadn’t been undertaken and I feel it requires a bit more thought and a little stronger structure to make this a really valuable paper.
Response: Thank you for this feedback. We have added text to better link the conceptual model to the balance of the paper. We have also added a new table (Table 2), which rates the identified research needs based on four factors relevant for prioritization. We then identify the top five research needs based on prior discussions among experts and highlight these as the areas that could most universally improve knowledge necessary to inform establishment of environmental flows for TCEs.
Section 2 is headed as being a framework for establishing research priorities. Essentially, it appears that the authors believe that there are fundamental flaws in existing frameworks that prevent them from being useful, but aside from identifying areas where the frameworks could be improved, it does not provide a critical evaluation of the current suite of frameworks . I was also expecting this this section would provide a framework that is used throughout the remainder of the manuscript to establish the research priorities. It does, but the link is not explicitly made between the framing in this section and the rest of the manuscript. The framework doesn’t guide research priorities, it helps to identify knowledge gaps that then can be prioritised. This section needs some reworking to clearly articulate the point the Authors are trying to make .
Response: The intent was to expand on an existing framework and not provide a review of available frameworks as this has been done recently e.g. Van Niekerk et al. 2019 and is described in the text (lines 99-111). This framework was used throughout the manuscript to highlight key research gaps necessary for advancing environmental flow programs for estuaries. We have added text at the end of section 2 (lines 153-160) to provide a better roadmap that relates the conceptual framework to the balance of the paper. We have also included text throughout the manuscript to better identify links back to the framework throughout the manuscript. Figure 1 is referred to where appropriate.
I worry about the recommendation to generate yet another typology/classification scheme. The scientific literate is replete with classifications schemes for such environments (one only has to look to the wetland literature which, to some degree, overlaps with the TCE literature). I am not convinced that another generic classification scheme would offer environmental flow managers or those attempting to provide environmental flows for TCE outcomes anything that a site-specific evaluation would not provide. I also suspect that the desire to have a typology that is “inclusive of all estuaries that could be subject to environmental flow requirements, yet robust enough to accommodate the characteristics of individual systems” is a pipe dream and we need to consider how we might better use a generic framework for eflow evaluation across a range of specific estuary types. Otherwise we could spend yet more years where the science is focussed on classification, not on understanding the eco-hydrology relationships needed to better manage the system.
Response: The section on the typology has been scaled back to focus only on small temporarily closed estuaries. We have also removed the recommendation for a new typology and instead focus on enhancements to existing typologies. This section now includes more explicit linkages to biology (beyond hydrology and geomorphology. We highlight flow timing aspects and how they relate across all TCEs, which is gap in many existing typologies.
I refer the authors to Kath, J., Boulton, A.J., Harrison, E.T. and Dyer, F.J., 2018. A conceptual framework for ecological responses to groundwater regime alteration (FERGRA). Ecohydrology, 11(7), p.e2010 where the authors, instead of looking to further divide existing classes of GDE’s, look for commonalities that may be useful in understanding knowledge gaps and managing groundwater dependent ecosystems. Groundwater dependent ecosystems are similar to estuarine environments in their complexity and lack of investment in understanding and managing.
Response: Thank-you for referring us to this article. We like the general structure and the way the authors provided a clear roadmap that linked overarching research needs with the body of the paper. We have emulated certain aspects of that structure in our revisions.
The need to better incorporate information from different temporal scales is a theme throughout the manuscript yet it is not well drawn out. The thing that makes estuaries different from (say) end of system wetlands or floodplain wetlands is the interplay between fresh and salt water (river flow and tidal flow to use the language of the manuscript). This means that a structured assessment of flows at different temporal scales is needed from sub daily (tidal cycles) to long term regimes. This point is poorly made in the manuscript. Table 1 does not link well to the text which makes the case (albeit in passing – lines 276-278) that estuary environmental flow assessments should be simulated at hourly or daily time steps. It would have been nice to see a better structured Table 1 which focussed on the temporal scale of the hydrological knowledge needs. Instead the table focusses on the flow components which doesn’t help this section address the specific needs of estuaries.
Response: The section on driving and forcing factors, and especially the text around Table 1, has been revised to better signpost the different temporal scales that influence the hydrological and hydraulic processes in estuaries. Table 1 has not been modified, as we believe that in the context of an eflows assessment, the management manipulation will involve protection or restoration of flow components. Consequently, we felt it important that the table remains structured around flow components.
The need to also consider temporal scales in establishing expectations or desired conditions is missed from this manuscript and I would argue it is particularly important in estuaries. The spatial and temporal complexity of TCEs across multiple levels of ecological organisation makes establishing expectations or desired conditions a significant challenge. As with wetlands, objectives and targets are often static indicators (a single “desired state”) and fail to take into account the importance of spatial or temporal variation in population or community structure, or composition which may be functionally significant.
Response: The text of the section on desired conditions has been edited to incorporate discussion of the temporal variability of processes in estuaries and the different scale on which this occurs. We consider this an extra argument in favour of a focus on processes rather than static end states. We have also added comments about this in the context of climate change.
The manuscript essentially provides a shopping list of 34 knowledge gaps that if filled will advance our understanding of ecological responses to altered flow regimes in TCEs. It then disappointingly fails to then take these knowledge gaps and prioritise them to help investors and researchers. Of these identified– which are the most important – and how would you go about determining which are most important?? Many are a huge task – and lead to a research agenda that would take squillions of dollars and tens of years to deliver. This is not going to happen and we need to be starting to manage better now. How can we get smarter at addressing such massive knowledge gaps to better inform environmental flow management?? This is where I think the authors could turn a rather pedestrian piece into something of significant value to the scientific community and it just falls short.
Response: Thank you for this suggestion. As discussed above, we have also added a new table (Table 2), which rates the identified research needs based on four factors relevant for prioritization. We then identify the top five research needs based on prior discussions among experts and highlight these as the areas that could most universally improve knowledge necessary to inform establishment of environmental flows for TCEs. We believe the addition of this summary table greatly improves the manuscript and makes it less pedestrian.
I note that the phrase ‘due to’ is often incorrectly used. ‘Due to’ should be used to modify a noun and preceded by a form of the verb ‘to be’. Consider replacing most with because of or revising the sentences to use it correctly.
Line 69: the phrase ‘high levels of ecosystem function’ is odd. They either provide significant ecosystem functions or many ecosystem functions.
Line 72: ‘the effects of’ not just ‘effect of’
Line 79: don’t need to re-define TCE’s – they have been defined previously
Line 677: TCE estuaries – estuaries is repeated.
Response: We have made all these changes except for defining TCEs on line 79. This is the first instance where we refer to temporarily closed estuaries in the body of the text (vs. the abstract), so we have retained the definition in this location
Round 2
Reviewer 2 Report
The changes made to the manuscript are difficult to ascertain because reference to the changes does not appear to link to the line numbers I have been sent. It appears that most of the changes are cosmetic and don't really demonstrate the additional thought I had expected from the authors.
I do however, appreciate the prioritization process provided in Table 2 - this at least starts to give funders and research teams some guidance.
Figure 3 caption - check spelling of correspond.
Author Response
Thank you for the quick review of the revised manuscript. We apologize for the difficulty in tracking the changes we made. To that end, I am uploading a redline version of the manuscript that better shows our edits and revisions in response to the reviewer comments.
I have also corrected the spelling of correspond in the caption of Figure 3.
We look forward to your final decision on the manuscript. Thank you.
Author Response File: 
Author Response.docx
