In this manuscript, the authors, through single-chamber analysis (LA-ICP-MS) of planktonic foraminifera in the high-salinity and oligotrophic environment (GOA: Gulf of Aqaba), captured in detail the temporal and vertical variations of element/Ca ratios. Especially, the thorough monthly sampling at each depth is considered by this reviewer to make this work quite unique. Also, by the analysis of each single chamber, the authors focus on inter-chamber variability (ICV) and propose it as an event proxy, which is also characteristic.

In the monthly time-series analysis, they capture the rapid chemical composition change associated with the event of spring mixing.

In the study subjects (G. ruber albus and T. clarkei “big” / “encrusted”), the difference of characteristics for each is shown, and the importance of species-dependency in proxy use is indicated. These efforts can become the basis to establish the chamber-by-chamber record of planktonic foraminifera as a future high-temporal-resolution paleoenvironmental reconstruction method.

The expected audience is as follows, and this fits with the scope of the journal:

Paleoceanography and paleoclimatology researchers interested in high-resolution records and short-term event analysis

Geochemistry and biomineralization researchers who want to understand element uptake mechanism and calcification physiology

Analytical chemistry and LA-ICP-MS application researchers who want to know possibilities and limitations of micro-scale analysis

Before publishing, I would like to comment the points which I noticed should be solved:

1. Na/Ca spikes

The reason for Na/Ca spike cannot be explained by the increase of Na concentration in seawater. Foraminiferal Na/Ca is also an indicator of salinity. If we try to explain the large Na/Ca variation as in Fig. 7 by seawater Na/Ca variation, we have to suppose an event in which salinity increases by two digits scale. However, from the desert in the hinterland, even if minerals are input and somewhat dissolved, it is hard to consider an impact on the salinity at the scale of digit change. Also, from the analysis of T. clarkei in Fig. 9b, c, Na shows positive correlation with Mg, Al, Ti, Mn, Fe. This may suggest that T. clarkei has the property to incorporate sinking particles containing Na, such as Albite/Na-feldspar and Plagioclase, on/into the shell during calcification. I guess the possibility of particle trap on the shell. This is possibly indicating a new role of foraminifera as “fossils that trapped sinking particles” in addition to being environmental proxies. From Fig. 7(b), there is a possibility that the same phenomenon is happening in G. ruber. If this is because the study area has an arid region in the background and seasonally sinking particles become extremely abundant in seawater, this does not affect the soundness of proxies using planktonic foraminifera from other regions. Also, if we can monitor some elements like Ti, Na or Si to check whether the proxy is working normally, the soundness of the environmental proxy in the study area is also kept, while the role as a catcher of sinking particles itself will emerge.

From the perspective of calcification mechanisms, the calcifying fluid is to some extent isolated from ambient seawater, making the direct incorporation of external particles unlikely. However, it is possible that particles adhering to the shell surface become enclosed when a new chamber is formed over them. Although unpublished, in my own experience this reviewer has observed cases where diatom frustules were incorporated into the interior of the shell. In other words, the incorporation of foreign material into the shell interior can indeed occur. While such occurrences have generally been rare enough to go unnoticed, this study might find by the possibility that in certain seasons in this particular region, such incorporation might happen more frequently.

To verify whether the Na/Ca spikes originate from calcite itself or from the incorporation of external mineral particles, it is necessary to conduct some form of direct check. For example, confirming the amount and seasonal changes of sinking particles in the study area, and performing SEM observations or XRD analysis of the shells, would allow you to determine whether mineral-like foreign materials are present inside the calcite. Alternatively, by examining the depth-resolved elemental profiles obtained from the authors’ LA-ICP-MS analyses, it should be possible to determine whether the influence of external particles extends throughout the entire calcite structure or is confined to specific locations.

Establishing this point is essential for assessing the reliability of Na/Ca as a proxy in this environment, and solving it would also strengthen the discussion of Fig. 12.

2. Final chamber (F0) composition

Regarding the idea that F0 (final chamber) element composition does not reflect the environment, I think there are both opinions, but to deny it here needs a little more basis. For example, Sadekov et al. (2009: https://doi.org/10.1029/2008PA001664) concluded that Mg/Ca of the final chamber has the highest correlation with temperature, and Hupp and Fehrenbacher (2024: https://doi.org/10.61551/gsjfr.54.4.355) also did not point out problems in analyzing the final chamber. There are other similar studies. Especially Mg/Ca has many cases that respond rather straightforward to temperature changes, so I would be more convinced if you point out that calcification temperature (depth) is different from the assumption.

3. Small number of individuals

I appreciate again the accumulation of efforts that you analyze three categories of foraminifera at each depth every month, which is very ambitious. However, the small number of individuals in each population is obvious. ICV is discussed, but I do not find quantitative treatment of inter-individual variability or pooled mean value. As the basis to say that discussion is possible with few individuals, could you add, in addition to pooled mean value, statistical indices showing the magnitude of variation among individuals (for example: standard deviation, coefficient of variation) or excuses from previous studies which state that comparing by pooled mean value for inter-individual variation is no problem?

4. Minor points

Fig. 2 appears quite late in the text. You forget to refer to Fig. 2 somewhere in the first half.

In the text final chamber is written as F0, but in Fig. 1 it is F-0. Please unify.

In Fig. 4 etc., please indicate MLD also in the legend.

Comparing the environmental figure in Fig. 1 with Fig. 3–8, the horizontal axis is shifted. Please fix, and please also write what the horizontal axis represents.

In Fig. 9, elements are slightly misaligned with the columns. For example, U is completely showing the result of the previous element for both vertical and horizontal axes.