Review Manuscript DDI-2024-0411

Title: Modeling non-indigenous ascidian larval dispersal in the coastal waters of the Eastern Mediterranean Sea

I have carefully read the manuscript, which presents a study on the dispersal potential of invasive ascidian species along the Israeli coast of the Mediterranean Sea. The authors employ a biophysical modelling approach to investigate the dispersal dynamics of four species of solitary ascidians. This research is valuable as it shows that despite a short pelagic larval duration and very specific settlement habitat, these invasive species can spread rapidly via larval dispersal and highlights the role of artificial substrates in facilitating their expansion. The study also explores how future climate change scenarios may affect the reproductive patterns of these ascidians.

The manuscript is well-written, with clear presentation of results that effectively support the authors’ conclusions. However, I believe the study would benefit from further refinement in a few areas before publication. First, additional details in the methodology section would enhance the reader’s understanding of model parameterization (see specific suggestions below). Moreover, it would be beneficial for the authors to acknowledge and discuss the limitations of their study, particularly regarding assumptions in future climate scenarios. Finally, expanding the introduction to provide more context on these invasive species—including their current distribution, the timeline of their arrival in the Mediterranean, and the risks they pose to aquaculture—would give readers a better sense of the urgency and importance of this research.

Detailed comments can be found below:

Line 59: Solitary species reproduce by broadcast spawning (a word is missing).
Line 95: Could you present the current distribution of the species in the Mediterranean Sea? It would help the reader get an idea of the importance of the work and issue.
Line 110: Are all the species present in the Red Sea?
Line 114: We need more information on the literature review to reproduce this step. How was the literature review conducted? What search terms were used?
Line 121: The term “general” is vague. Did you use the average duration or the most commonly reported duration?
Line 125: What does IOLR stands for?
Line 126: Can you add the measurement stations on Map 3? Can you justify that two measurement stations are enough to represent the variability of temperatures in the part of the sea?
Line 129: Please describe the biophysical model in more details. Describe the physical oceanographic model. Give the temporal and spatial resolution of the two nested models. Describe the larvae behaviours, or justify the absence of behaviour, during dispersal.
Line 135: Please write a paragraph detailing the links between reproduction and SST in your model. In other words, explain how SST is impacting reproduction, dispersal, and/or settlement.
Line 141: Why did you not consider changes in the currents and their potential effects on connectivity? Is SST enough to estimate the impact of climate change on the potential spread of these invasive species?
Line 145: Why did you choose only one scenario for your analysis? Could you include intermediate scenarios?
Line 148: How was the habitat compiled? Where did you get the layer representing the artificial substrate? Are you integrating any species record in your analysis? What is the current distribution of these 4 species in these habitats?
Line 149: We need more information on the biophysical to be able to replicate the study: number of larvae released per site, number of sites, size of the release and settlement sites, frequency of release, duration of the release, settlement behaviour, …
Line 156: What values of horizontal and vertical diffusivity were used?
Overall, it is complicated to understand the differences between the 4 models for the 4 species. It can be pieced together by referring to the Table 1, but I would like to see a part dedicated to this in the text as well.
Line 166: include Cyprus and Syria, with respective sites, on a map. How were the habitats for these regions compiled?
Line 196: How does the connectivity change with increased temperature? Are ascidians reproducing multiple times through the reproduction period?
Line 200: Can you elaborate on the harm caused by invasive ascidians?
Line 202: You need to elaborate on the need to understanding ascidian larval connectivity for conservation strategies and marine protected areas. I believe there is a much stronger point to be made on the impact of ascidians on aquaculture production and infrastructure via biofouling.
Line 229: mtDNA has been used in New Zealand black foot abalone to detect genetic breaks due to isolation by distance.
Line 231: What is creating these genetic breaks?
Line 237: Your study only estimated that the reproduction period of three species will lengthen, but you did not demonstrate that it will facilitate the dispersal and establishment of the ascidians. I would like to see a part discussing the limitations of this study.
Table 1: Show the distribution along the coast in a separate map to help international readers. How was the number of reproductive days calculated?
Figure 4: A map of the density of trajectories would improve the visualization by allowing for a clearer and more intuitive comparison of the dispersal patterns. A trajectory density map would highlight areas with higher concentrations of paths, providing a quick visual cue to identify regions with the most significant dispersal activity.

I would like to thank the authors for addressing all of my comments and implementing the suggested changes to the manuscript.

I only have one minor comment: on line 212, I believe the following text can be removed: "and various interpolation methods (A, B, C grids, NetCDF, ASCII)" as only one interpolation method would have been used and NetCDF and ASCII refer to output formats and not interpolations.