How Do Underwater Cultural Heritage Sites Affect Coral Assemblages?

Round 1

Reviewer 1 Report

Review of remotesensing-2289503-peer-review-v1

 

 

 How do underwater cultural heritage sites affect coral assemblages?

 

Line 38            should have a reference to WWII era etc shipwrecks in the study area

Line 83            same  as above

 

What’s missing in the introduction is a discussion that UCH are also DATED substrates and thus can be used to consider aspects of growth and recolonisation by corals, for example concrete bottom weights of (former) mooring buoys of the concrete sides of sea-plane ramps running from MSL to -4m MSL.

 

 

Line 80–85      WHAT are these UCH? Be specific. All that is discussed is generic. But UCH range from concrete to iron-based tanks and landing  barges, to dumped military material eg Jeeps and truck (for ex. in Majuro Lagoon), to aluminium based aircraft.  From vertical surfaces (ships) to surfaces parallel to the ocean surface (aircraft). What are we talking about here?

 

Also, when considering contaminants, what is the specific substrate? Both from a material perspective (concrete, iron, aluminium) and from a pollutant perspective (leaching fuel etc)

 

Also, what is the disturbance level here? Did the UCH act as fish attractant devices and thus were visited more by spearfishing divers? Specific if not (I guess not as in Apra Harbor).

What about recreational divers (US Navy personnel with clearance to dive) visiting the UCH? 

This needs to be specified  as it will influences interference.

 

These issues  must be addressed before the validity of the rest of the paper can be assessed

 

Author Response

Thank you for providing us with constructive feedback to improve our manuscript. We have addressed your comments in the revised manuscript, and provided specific responses with line numbers to your comments in the attached document. 

Author Response File: Author Response.docx

Reviewer 2 Report

Studying artificial reef substrates created at UCH sites is important for understanding the interactions, both positive and negative, between human activities and natural ecosystems. Visualizing the findings of this work, would provide a better understanding of those interactions. This could be done either by a set of representative illustrations of the coral assemblages (at the three habitat categories), or moreover by a comparison chart showcasing the differences in coral assemblage structure among the three study regions (e.g. as they derived from the SIMPER analysis and already described in the results section).

Author Response

Thank you for providing us with constructive feedback to improve our manuscript. We have addressed your comments in the revised manuscript, and provided specific responses with line numbers to your comments in the attached document. 

Author Response File: Author Response.docx

Reviewer 3 Report

Line 157 – I would prefer the use of precision here in place of scale, as scale can be ambiguous.

Line 157 - 159 – It would be good to provide some figures for estimated vertical and horizontal accuracy here. Also, what was the procedure for surveying GCPs, and their estimated level of accuracy? Maybe talk about the refractive index of water and how this could potentially impact the photogrammetric process.

Line 184 to 186 is repetition of what is said above. I appreciate the application is different, but why not just say “using the same methodology as above”?

Discussion – Maybe it’s not the primary point of this paper, but it would be good to discuss variability between UCH sites of different ages, rather than treating them all as being the same, since intuitively this would also seem to be a key factor in coral diversity.

I think that it would be very useful to provide some examples of orthoimages and DEMS developed created during the project.

Author Response

Thank you for providing us with constructive feedback to improve our manuscript. We have addressed your comments in the revised manuscript, and provided specific responses with line numbers to your comments in the attached document. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

 

Review of

How do underwater cultural heritage sites affect coral assemblages

 

 

 

Thank you for the revised ms.

 

I am now confused. In the light of your responses, what is the purpose of the paper. There is no well formulated, clear aim.

 

You state:

“The resulting coral assemblage 118

data (live coral cover, coral diversity, and richness) and 3D habitat complexity data (sur- 119

face complexity, terrain ruggedness, slope, fractal dimension, and curvature) were inte- 120

grated into analyses of variance, univariate statistical models, and multivariate analyses 121

to examine patterns in reef habitats among all study sites, and to determine if UCH sites 122

influence coral reef ecology and habitat complexity. The results from this study provide 123

insight into the ecological ramifications of UCH artifacts on coral reefs and can be scaled 124

and adapted to other locations to properly manage and conserve marine resources.

 

So from reading this, UCH artifacts may have ecological ramifications…so far so good.

 

In your response to review Round #1 you state:

. We appreciate the comments on contaminants and disturbance, but these data do not exist, thus we did not speak to parameters we are unable to address with our data. …Thus, our focus for this article, in this special issue, is to illustrate how high-resolution photogrammetry and advanced statistical tools can be applied to understand differences in assemblage structure and 3D complexity on natural and artificial substrate. Our focus is not on detailing the characteristics, contaminants, history, temporal dynamics, fish assemblages, or diver-based disturbance on UCH sites.

 

 

Yes, one can compare UCH sites with natural reefs and see whether ecology and habitat complexity differ. But observing whether they do or no do not, is utterly meaningless unless the factors that lead to the establishment of the coral assemblage are considered as well as the factors that may impact the coral development. Artificial substrates differ from existing coral substrates or dead coral (eg in  on reefs where coral was quarried and new coral colonise on excavated edges). The UCH substrates differ in raw material (iron/steel, aluminium, concrete), stability, pollutants, etc etc. I my view it is not acceptable to simply sweep them aside in a generic comment that there are no timeline data.

You have some of this in line 418ff.  But this is not enough

Also, you are commenting on concrete substratum of the Barge Glass Breakwater site. How does the Tanker, which is also of ferro cement, differ? This is not mentioned.

 

Unless I am missing something, you do not draw on the different chronologies of UCH reef establishment in your analysis. Yet there is a difference. The Cormoran  was scuttled in April 1917, with the bulk of the other UCH in WWII.  So, what is the difference here? Is there a difference in the coral assemblage structure? 

 

Also, given the comparatively recent establishment of the WWII era derived coral assemblages, what is the influence of water depth and thus temperature profile? Surely this is significant ? The position of the wreck of the Cormoran provides you with a convenient gradient to look at the effects of depth in  a single site where you have the same starting point with what amounts to a blank canvas. 

 

In my review I wrote:

What’s missing in the introduction is a discussion that UCH are also DATED substrates and thus can be used to consider aspects of growth and recolonisation by corals, for example concrete bottom weights of (former) mooring buoys of the concrete sides of sea-plane ramps running from MSL to -4m MSL.

 

To which you responded:

 

We added a sentence about this value of UCH for understanding colonization and growth. While we do not have temporal data to address these parameters, we point out how future studies can do so to better understand coral reef ecology. [Lines 103-156]

 

This is patent nonsense. You DO have temporal data. You have the WWI wreck of the Cormoran , and the WWII-era Tokai Maru sits on top. You can compare the structure of the coral assemblage at the stern of the Cormoran  with that of the hull of the Tokai Maru. And use the gradient of the Cormoran , as well as the albeit shorter gradient on the hull of the Tokai Maru to account for the depth effects.

 

There is also no discussion on currents, water exchange and nutrient inflows in the analysis and discussion. The location of the sites in Apra Harbor and outside the breakwater differ in their position. Environmental pollutant concentrations derived from US Navy shipyard operations are well documented and differ spatially in the Habor basin. That appears not to have been considered in the analysis.

 

If the aim of the paper is to show technological and methodological approaches, then say so. But as it stands it does not “provide insight into the ecological ramifications of UCH artifacts on coral reefs” as the paper claims. 

 

I would recommend that the authors take a step back a look at the focus of their paper as intended vs as written.  

The response the review comments make sense :  “focus for this article, in this special issue, is to illustrate how high-resolution photogrammetry and advanced statistical tools can be applied to understand differences in assemblage structure and 3D complexity on natural and artificial substrate” 

 

But then make THAT the expressed focus of the paper and shape the introduction accordingly and do not wrap the paper into a foil of cultural heritage.

 

The paper needs a good rethink and refocus. I recommend that the authors resubmit a new manuscript.

 

Minor issues

 

Figure 2 needs a formal scale

 

 

Author Response

Attached please find our reply. Thanks.

Author Response File: Author Response.pdf