LED Lighting and High-Density Planting Enhance the Cost-Efficiency of Halimione Portulacoides Extraction Units for Integrated Aquaculture

Round 1

Reviewer 1 Report

I. This is big undandestanding presented in this apper. Autors are using LEDs which are emmiting whie light (see Fig.1b) but in the paper this LEDs is called as blue one. This issue must be fixed. Plese provide all photometric/radiometric and colorimetric data for this LED. Please give radiant/luminous flux informations and μmol/J. Also please describe chromaticity point x,y (or u,v) and CCT [K]  values. 

 

II. Also in Introduction please include information about PAR (Photosynthetically Active Radiation) radiation and DIN standard describing PAR radiation must be called. Please describe also μmol/J parameters which is main parameter which must be used when plant lighting is described.  

 

III. In Fig.1 the intensity could not be described in counts, this should be described in relative or radiometric units.

 

IV. Please make shure that your spectroradiometer is calibrated for intensity. The compact spectroradimeters must be calibreted for intensity (by using incadescent lamp) even they are used for getting relative measurement data. Those instrument are strong nonlinear with wavelenght and manufacters typically are selling them without calibration. For this reason please describe intensity calibration data (curve) for used in this research spectroradiometer. Also please provide Figure where measured by this spectroradiometer SPDs of clasical bulb (halogen or incadescent lamp) will be given. Only if SPDs shape of clasical bulb (and its CCT) will be correct the instrument can be used for LEDs and FL lamp SPDs measurement. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

It is an interesting and well-structured work, also well supported bibliographically. It provides good prospects for integrated multitrophic aquaculture (IMTA).

I recommend expressing oxygen also as a percentage saturation, which immediately gives you an idea of the level of oxygen present. I would add a few more pictures of the experiments, which are very interesting.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Methodologically correct research on a novel topic with great projection for the development of sustainable aquaculture through the development of IMTA systems in aquaponics. Despite the interest of the subject, this research, due to its own experimental design, does not provide relevant information for the possible commercial development of the Halimione portulacoides culture in this type of system. The main problems of the manuscript are:

- The choice of the various light sources tested is not adequately justified. There are many types of fluorescent lights, with very different spectra, here a specific type has been chosen without any justification. On the other hand, it has been decided to use only blue led light when it is known that chlorophylls also absorb radiation in the red band, which is why many producers combine both types of led as indicate many of the works that the authors cite in table 3, even in many of these works cited it is clear that red LEDs give better results than blue ones.

- The light intensities tested (about 370 μmol photons m^-2 s^-1) are much lower than those that usually exist in the salt-marsh environments where these species live (usually above 1000 μmol photons m^-2 s^-1), Therefore, the data obtained on productivity and growth rate, the influence of density, biofiltration capacity, etc. under these conditions they cannot be extrapolated to an industrial production system that claims to be profitable. In this regard, it would have been very interesting to study the photosynthetic saturation curve to know if the plants or part of them were well below this value, which is undoubtedly affecting productivity. Differences in the pigment composition are hardly noticeable, probably because the plants are far below the light saturation that could be the cause of stress that would surely have an impact on the synthesis of accessory pigments.

- The justification for carrying out the pigment composition analysis is unclear: “potential changes in the pool of photosynthetic pigments were also assessed to understand if long-term exposure to blue LEDs affected photosynthesis”. Normally this analysis is carried out to know the possible photosynthetic stress or to see if the type of light can promote a difference in proportions of accessory pigments that can increase the added value of the raw material obtained due to the biotechnological or bioactive interest of any of them.

- From the point of view of productivity an obvious result is obtained: the lower the density, the higher the individual growth rate, and the lower production per unit area. The interesting thing would have been to determine in these experimental conditions the maximum density from which productivity per unit area no longer increases and, however, intraspecific competition phenomena can already be clearly appreciated. Although these data could not be extrapolated to a more efficient production system (with greater light intensity), they would serve to detect the symptoms that intraspecific competition is manifesting itself negatively. In table 1 it seems that in "Growth per hydroponic unit, in final biomass" and in "Productivity" there must be an error in the letters that indicate the significant differences.

- The economic cost analyzes are made with an assessment of the cost of kWh^-1 in Portugal at the time of writing this paper. This is irrelevant, the only interesting data is the percentage difference in consumption between both lighting sources since everything else is circumstantially very variable.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

This version could be published at present form. 

Reviewer 3 Report

I am satisfied with the changes made to the manuscript. I wish that some of those that obviously would need further experimentation, be taken into account in future research.

Sincerely