An Innovative IMTA System: Polychaetes, Sponges and Macroalgae Co-Cultured in a Southern Italian In-Shore Mariculture Plant (Ionian Sea)

Round 1

Reviewer 1 Report

This manuscript represents the valuable information on the actual trial of an IMTA system in the field. The IMTA system will contribute to secure the sustainability of aquaculture which grows rapidly all over the world. Before publishing this manuscript in the journal, I have two general comments. The first comment is related to the material cycle in the aquaculture site. I understand that the production of seabass and sea bream is around 100 tons/year. This production means that the waste from the aquaculture site may reach a few hundred tons on a basis of wet weight, depending on the feed conversion ratio of them. In this trial, the production of polychaetes was estimated as 0.36 tons and the production of sponges was around 200 L. The production of macroalgae is not clear, but will be around 1.4 tons including both species. I suggest that the authors predict what percentage of the waste was fixed by these organisms after all the productions are converted into wet weight. In addition, the authors discuss how to scale-up the IMTA system for the production to be comparable to the waste production. Then it is a critical issue whether these invertebrates and macroalgae are harvested to be used for food or the other purposes. They have a function of fixing nutrients from waste, resulting in improving the environmental quality. However, they may deteriorate the environment by obstructing the diffusion of waste and then increasing the concentration of waste in the aquaculture site if they are not harvested. I suggest that the authors discuss this negative aspect more clearly.

The other comments are as follows.

• Abstract: A period is required after ‘cultivated in horizontal collectors’.
• 1 Study area: Please show the mean depth of the study area. Only the depth of cages is represented. The information on topography and mean current velocity, if possible, is important to estimate the diffusion region of the waste.
• 2. Field work: sampling and processing: Please describe what items are measured for sediments and water column.
• The caption of Fig.2: What does ‘ a camera’ mean? Did you install regularly underwater cameras in the aquaculture site?
• 5: I cannot find the photos E and F.
• 6: I cannot find a body length and a density. Only the biomass (wet weight) is represented.
• 7: Please represent the regression curves in A.
• Line 332: The authors mention that ‘initial weight loss occurred as a consequence of the stress due to the collection and cutting of donor sponges into uniform explants’. Certainly, the growth rate of sponges was slightly reduced, but the accuracy of the monitoring method may not be sufficient to discuss such slight reduction.
• Line 362: The relation between the descriptions ‘in the first 11 days of 350 cultivation a 11% SGR was measured’ and ‘in the first 7 days of cultivation the mean SGR value was 11.1%’ is not clear.
• Line 402: ‘to’ should be removed.
• Line 506: If the authors monitor the concentration of dissolved inorganic nitrogen, please discuss the limitation of nutrients with the monitoring data. Were the abundant epiphytes blooming induced by nutrients input under proper light intensity and water temperature?

Author Response

Manuscript 940740: An innovative IMTA system: polychaetes, sponges and macroalgae co-cultured in a Southern Italy in-shore mariculture plant (Ionian Sea).

Answer to Reviewer 1

Rev: This manuscript represents the valuable information on the actual trial of an IMTA system in the field. The IMTA system will contribute to secure the sustainability of aquaculture which grows rapidly all over the world. Before publishing this manuscript in the journal, I have two general comments. The first comment is related to the material cycle in the aquaculture site. I understand that the production of seabass and sea bream is around 100 tons/year. This production means that the waste from the aquaculture site may reach a few hundred tons on a basis of wet weight, depending on the feed conversion ratio of them. In this trial, the production of polychaetes was estimated as 0.36 tons and the production of sponges was around 200 L. The production of macroalgae is not clear, but will be around 1.4 tons including both species. I suggest that the authors predict what percentage of the waste was fixed by these organisms after all the productions are converted into wet weight. Answer: Answer: we extrapolated some data concerning Polychaete biomass, based on previous experiences. However, mass balance with net removal of wastes is still under study and will be the object of an additional work. The present paper deals with applied methodology to obtain a large amount of biomass. We also wish to underline that the calculation of the drivers in most cases even if based on measured data, outputs of system-scale models or a combination of both, is a simulation, by contrasts we are measuring data from the field.

Rev: In addition, the authors discuss how to scale-up the IMTA system for the production to be comparable to the waste production. Then it is a critical issue whether these invertebrates and macroalgae are harvested to be used for food or the other purposes. They have a function of fixing nutrients from waste, resulting in improving the environmental quality. However, they may deteriorate the environment by obstructing the diffusion of waste and then increasing the concentration of waste in the aquaculture site if they are not harvested. I suggest that the authors discuss this negative aspect more clearly. Answer: The biomass produced is regularly collected and only a small part remains unchanged. This is described in the text, but we have modified some of the discussions in accordance with the referee's suggestion.

The other comments are as follows.

• Abstract: A period is required after ‘cultivated in horizontal collectors’. Answer: Done
• 1 Study area: Please show the mean depth of the study area. Only the depth of cages is represented. The information on topography and mean current velocity, if possible, is important to estimate the diffusion region of the waste. Answer: we have modified the figure which now contains information on the bathymetry of the area and the direction of the main stream. The current entering the Great Sea flows into a passage of the breakwater. This current is due to tidal flows and varies continuously. The important thing for the definition of the experimental design was to verify the correct position of the treatments and controls according to the direction of the current regardless of its intensity.
• 2. Field work: sampling and processing: Please describe what items are measured for sediments and water column. Answer: We have entered the main parameters measured. The data are not reported because they are the subject of a subsequent publication on the effectiveness of the system designed. At the moment we have limited ourselves to describing the methodological part relating to breeding
• The caption of Fig.2: What does ‘ a camera’ mean? Did you install regularly underwater cameras in the aquaculture site? Answer: No, it is the rearing unit, called “camera”. Now it is better explained and camera has been changed in chamber.
• 5: I cannot find the photos E and F. There was a upload issue. Answer: Now the figure includes all the section.
• 6: I cannot find a body length and a density. Only the biomass (wet weight) is represented. There was a upload issue. Answer: Now the figure includes all the section.
• 7: Please represent the regression curves in A. Answer: Done
• Line 332: The authors mention that ‘initial weight loss occurred as a consequence of the stress due to the collection and cutting of donor sponges into uniform explants’. Certainly, the growth rate of sponges was slightly reduced, but the accuracy of the monitoring method may not be sufficient to discuss such slight reduction. Answer: Sponges are generally very slow growing organisms. Growth can vary significantly between seasons, populations or sites, and many sponge species have highly variable morphology, which complicates accurate estimates. In addition, sponges lack distinct morphological structures which can be used as growth indicators. When measuring growth in sponges, it should be recognized that sponges often heal wounds much faster than their normal growth rate and tissue regeneration is therefore not a good predictor of normal growth rates. The monthly measurement of the volume allowed us to detect the whole sponge biomass decrease during the first months of rearing and its subsequent growth.
• Line 362: The relation between the descriptions ‘in the first 11 days of 350 cultivation a 11% SGR was measured’ and ‘in the first 7 days of cultivation the mean SGR value was 11.1%’ is not clear. Answer: There was information on the species the SGR was referring to. Now in the text it is clearer.
• Line 402: ‘to’ should be removed. Answer: Done
• Line 506: If the authors monitor the concentration of dissolved inorganic nitrogen, please discuss the limitation of nutrients with the monitoring data. Were the abundant epiphytes blooming induced by nutrients input under proper light intensity and water temperature? Answer: Loredana

Reviewer 2

This is a paper worthy of publication in JMSE. It is generally well written although it is overly word sometime. However, there are several substantive issues that need to be improved before publication.

First is the issue of illustration. I think that Fig. 3 is not need. It illustrates nothing. Answer: This is fundamentally methodological work and we believe that explaining the activities in detail can add value to the understanding of the text

in caption of Fig. 5 there are six point (A-F), but only four photos represented. Answer: We solved the problem by loading the correct figure

Moreover, the captions not always correspond to pictures. Answer: We solved the problem by loading the correct capture

The same problem with Fig. 6. Answer: We solved the problem by loading the correct capture

In all graphs it is better to combine the data for both line and represent them as MEAN±SD. In Figures 4A, B, 6 and 9A, the X-axis must show the months in a valid scale. The time interval between July and September is not equivalent to that between September and December. The designation of time should be same on all Figs. Answer: We agree. The graphs have been modified according to a principle of uniformity of descriptors

Because co-cultivation of mussels, sabellids, sponges and seaweeds with fish had the aim of decrease the environmental impact of fish farm it is useful to provide comparative data of water quality and sediments at treated and control sites. Based on lines 143-145, such data were obtained. Answer: Verification of changes in the environmental structure takes a long time, investigations are still ongoing and the data have not been published. We modified the text by specifying which parameters were measured. more this paper focuses more on farming than on environmental quality.

Why there are not data on M. galloprovincialis? What was the effect of IMTA on production of farmed fish ? Answer: We are absolutely aware that mussels have a role in the bio-remediation of aquaculture wastewater: in this work, however, we have focused on uncommon species, while mussel is much studied. Our intent was to verify if and how polychaetes, sponges and macroalgae could respond to breeding and not so much the effect of this breeding on the environment. We are currently evaluating the environmental response but research is still ongoing.

Minor comments

The estimated production of the target species should be expressed as biomass per area or linear meter of long line. Answer: This is not possible at the moment. For now we have tested the growth performances of the various species and we have not tested the maximum breeding density in the individual chambers. This is a next step and it will be essential when we have to make the "scale leap". To date, we also do not know how far we can push the stocking density of invertebrates.

Growth rate should be provided as % per day. Please correct it. Answer: Now all Growth Rates are reported as daily percentage values.

The section “Conclusive remarks” should be shortened. Now it in part repeats the discussion. Answer: we have modified the chapter making it more streamlined

In title please change maricolture with mariculture. Answer: Done.

My recommendation is that the manuscript should be accepted, but this should be done after revision  

Author Response File: Author Response.docx

Reviewer 2 Report

This is a paper worthy of publication in JMSE. It is generally well written although it is overly word sometime. However, there are several substantive issues that need to be improved before publication.

First is the issue of illustration. I think that Fig. 3 is not need. It illustrates nothing. In caption of Fig. 5 there are six point (A-F), but only four photos represented. More over, the captions not always correspond to pictures. The same problem with Fig. 6. In all graphs it is better to combine the data for both line and represent them as MEAN±SD. In Figures 4A, B, 6 and 9A, the X-axis must show the months in a valid scale. The time interval between July and September is not equivalent to that between September and December. The designation of time should be same on all Figs.

Because co-cultivation of mussels, sabellids, sponges and seaweeds with fish had the aim of decrease the environmental impact of fish farm it is useful to provide comparative data of water quality and sediments at treated and control sites. Based on lines 143-145, such data were obtained.

Why there are not data on M. galloprovincialis? What was the effect of IMTA on production of farmed fish ? 

Minor comments

The estimated production of the target species should be expressed as biomass per area or linear meter of long line.

Growth rate should be provided as % per day. Please correct it.

The section “Conclusive remarks” should be shortened. Now it in part repeats the discussion.

In title please change maricolture with mariculture

My recommendation is that the manuscript should be accepted, but this should be done after revision  

Author Response

Manuscript 940740: An innovative IMTA system: polychaetes, sponges and macroalgae co-cultured in a Southern Italy in-shore mariculture plant (Ionian Sea).

Answer to Reviewer 2

This is a paper worthy of publication in JMSE. It is generally well written although it is overly word sometime. However, there are several substantive issues that need to be improved before publication.

First is the issue of illustration. I think that Fig. 3 is not need. It illustrates nothing. Answer: This is fundamentally methodological work and we believe that explaining the activities in detail can add value to the understanding of the text

in caption of Fig. 5 there are six point (A-F), but only four photos represented. Answer: We solved the problem by loading the correct figure

Moreover, the captions not always correspond to pictures. Answer: We solved the problem by loading the correct capture

The same problem with Fig. 6. Answer: We solved the problem by loading the correct capture

In all graphs it is better to combine the data for both line and represent them as MEAN±SD. In Figures 4A, B, 6 and 9A, the X-axis must show the months in a valid scale. The time interval between July and September is not equivalent to that between September and December. The designation of time should be same on all Figs. Answer: We agree. The graphs have been modified according to a principle of uniformity of descriptors

Because co-cultivation of mussels, sabellids, sponges and seaweeds with fish had the aim of decrease the environmental impact of fish farm it is useful to provide comparative data of water quality and sediments at treated and control sites. Based on lines 143-145, such data were obtained. Answer: Verification of changes in the environmental structure takes a long time, investigations are still ongoing and the data have not been published. We modified the text by specifying which parameters were measured. more this paper focuses more on farming than on environmental quality.

Why there are not data on M. galloprovincialis? What was the effect of IMTA on production of farmed fish ? Answer: We are absolutely aware that mussels have a role in the bio-remediation of aquaculture wastewater: in this work, however, we have focused on uncommon species, while mussel is much studied. Our intent was to verify if and how polychaetes, sponges and macroalgae could respond to breeding and not so much the effect of this breeding on the environment. We are currently evaluating the environmental response but research is still ongoing.

Minor comments

The estimated production of the target species should be expressed as biomass per area or linear meter of long line. Answer: This is not possible at the moment. For now we have tested the growth performances of the various species and we have not tested the maximum breeding density in the individual chambers. This is a next step and it will be essential when we have to make the "scale leap". To date, we also do not know how far we can push the stocking density of invertebrates.

Growth rate should be provided as % per day. Please correct it. Answer: Now all Growth Rates are reported as daily percentage values.

The section “Conclusive remarks” should be shortened. Now it in part repeats the discussion. Answer: we have modified the chapter making it more streamlined

In title please change maricolture with mariculture. Answer: Done.

My recommendation is that the manuscript should be accepted, but this should be done after revision  

Author Response File: Author Response.docx