The revised manuscript has been improved by the reviewer suggestions taken on by the authors. However, there are still some points that need clearing up before the manuscript is suitable for publication. In some places, this is a result of the authors addressing reviewers’ comments in the response file but then not adding text to the manuscript to clarify the parts where questions were raised. I try to highlight these places in my specific comments. Frustratingly, in reading through the responses to reviewers’ comments there were also several places where the authors stated that they have made the suggested changes, but these were not in the current manuscript draft.
1) I think Figure 1 still needs some work. One of the previous reviewers recommended adding a scale bar to Figure 1C, which the authors say they have done, but I could not find it. By scale bar, I assume that the reviewer was referring to distance in km in addition to the latitude and longitude data that was already included. In addition, the Petrohue river does not appear to be labeled, while the other two rivers are labeled in different font sizes. And the symbol for the hydrological station is difficult to see in the figure. Perhaps a solid black triangle would be better. In the caption, the ash plume extent should be stated as “approximate” as it represents a full week of coverage for a dynamic feature.
2) I think the collection of the ash sample still needs more clarification. The eruption is described in lines 144-145 as taking place in two pulses on 22nd April and 23rd April. The ash sample was not collected until 6th May. In the response to reviewer 3 the authors state that the ash sample was collected after the third eruptive pulse. The timing of this third pulse should therefore be included in the eruption description to clarify to readers that there was not much time between deposition and sample collection. (The authors do mention an ash plume on 6th May in the caption of Figure 2, but details of this third pulse should also be mentioned in the text when discussing the eruption timing).
3) With the inclusion of Table 1, there should be some reference to it in the text, preferably before getting into details about the different leaching experiments. I also suggest splitting the water type (DI water, seawater, etc) and the measurements made (trace metals, alkalinity) into separate columns in Table 1.
4) There is still a problem with Figure 4 and/or Supplementary Table 2. The station-by-station data for diatoms in the figure do not match those in the table. According to Supp.Table 2, the circles in Figure 4 represent diatoms at Stn.A, the triangles Stn.B, and the squares Stn.C. This problem was brought up in the previous round of review and the authors stated that it had been addressed, so it may be that the updated version of the figure somehow didn’t get included. It needs to be addressed, along with any associated changes needed in the text regarding diatom abundance at the different stations (e.g. Line 326).
5) The supplementary material for this manuscript includes five tables and three figures and yet reference is only made to one supplementary figure in the text (four of the tables are mentioned with regards to data availability). It would make sense to include references to the appropriate supplementary materials in the main text.
6) In section 4.3 the authors no longer discuss the SW Atlantic area marked on Figure 8; instead referring to the area further south and shown on the supplementary figure. I think the better approach here involves first discussing the two Pacific areas, as they have done, and then comparing the two Atlantic areas – the one in Figure 8 that did not show any change in chlorophyll-a and then the one further south where location on the shelf and lower satellite coverage complicate interpretation.
Line 49 – The symbol for fluoride should be F-, not Fl-. This was brought up by Reviewer 2 previously. Also at Line 227 and Table 2.
Lines 68-72 – Suggest changing this sentence to “A pulse of Fe(II) release upon addition of Calbuco ash to seawater made it an unusually efficient dissolved Fe source. The fraction of dissolved Fe released as Fe(II) from Calbuco ash (~18-38%) was roughly comparable to literature values for Fe released into seawater from aerosols collected over the Pacific Ocean following long range atmospheric transport”.
Line 96 – change to “some freshwater bodies”
Line 104 – Remove the first “North Atlantic” reference from this sentence and change the year of the Eyjafjallajokull eruption to 2010 (noted in the previous round of reviews).
Lines 106 – The use of “largely” in this sentence is made redundant by the use of “predominantly”. Suggest removing “largely”.
Line 115 – Suggest changing the las part of the sentence to “..and leaching experiments carried out on ash collected from the fjord region, to investigate the inorganic consequences of ash deposition to natural waters”.
Lines 124-128 – I’m confused as to why the Petrohue is identified as the major river of the system (line 125) when the Puelo is the largest in terms of flow. Perhaps the first sentence could be adjusted to “The Calbuco volcano is located in close proximity to Reloncavi Fjord”.
Lines 161-163 – Ash was collected on 6 May. How long after deposition was this? Also clarify that the weather was dry throughout the period between deposition and collection. At present it is ambiguous – just the day preceding ash collection.
Line 176 – The range of concentrations selected was justified in comments to a reviewer as being broadly in line with previous studies. This justification could be included in the text for all readers.
Line 178 – Specify that the addition was of concentrated HCl.
Line 181 – Give the (approximate) seawater temperature.
Lines 183-184 – Suggest changing to “For these experiments, a pre-weighed mass of was added to 250ml South Atlantic seawater and manually shaken for approximately one minute, using an expanded concentration range of 0.2-4000 mg L-1”
Line 196 – change to “flow-through”.
Lines 215-217 – The inclusion of the size distribution of the ash is a good addition. In the response to reviewers, the authors also make the argument that the <63um size fraction has the greatest surface area and so the choice of size fractions includes both the dominant size fraction by mass (250-1000um) and the dominant size fraction by surface area (<63um). A couple of lines making this argument should also be added to the manuscript to clarify for the reader.
Line 227 – Change Fl- to F-.
Lines 234-240 – There is unnecessary repetition here. The first list of parameters could be removed, giving a sentence that reads “High temporal resolution (hourly) in situ measurements were taken simultaneously in the Reloncaví fjord (Fig. 1 C, North Patagonia Oceanographic Buoy) at the surface and at 3 m depth, using two SAMI sensors that measured spectrophotometric CO2 and pH (DeGrandpre et al., 1995; Seidel et al., 2008) (Sunburst Sensors, LLC), and an SBE 37 MicroCAT CTD‐ODO (SeaBird Electronics) for temperature, conductivity, depth and dissolved O2, as per Vergara-Jara et al., (2019).”
Line 254 – “an” instead of “a”
Lines 259-262 – Reword as “Additionally, as part of a long-term monitoring program at station C (Fig. 1), chlorophyll-a samples were retained from 6 depths (1, 3, 5, 7, 10 and 15 m) on 6 occasions during March-May 2015. Chlorophyll-a was determined by fluorometry after filtering 250 ml of sampled water through GFF filters (Whatman), as per Welschmeyer (1994).”
Line 266 – “…for comparison to prior reported data integrated to 10m…”
Line 267 – I don’t think it is necessary to reference Figure 4 here, particularly as Figure 3 has not yet been referenced.
Line 275 – Similarly, there is no need to reference Figure 7 here, when earlier figures have not yet been referenced.
Line 327 – Is station B the more freshwater influenced? Station A is further upstream in the fjord and close to the second largest river flow input. Station C is located close to the largest river flow input. Is there data to back up station B being more freshwater influenced?
Lines 329-330 – Reword this to state that highest chlorophyll concentrations were measured close to Station C on that date (rather than at C, including two nearby measurements).
Line 358 - Change Fl to F (also Table 2). Also, elsewhere in the manuscript all of these chemical species are written as ions, which is what is measured by the technique, and should also be written as such here for consistency.
Line 366 – The authors responded to a reviewer comment about brackish water leaching results not being included in Table 2 because the higher original concentrations of major ions in brackish water make it difficult to observe changes. A statement to that effect could be added here for the general reader.
Lines 376-377 – In the methods the ash loading for these leaching experiments is described as 2-50 mg/L, and in Figure 6 it is given as mg ash added, but here it is described as 0.1-6 mg/L. I think this latter case is supposed to be mg/100mL or just mg added. Please change units or numbers for consistency.
Lines 377-383 – No mention is made here of where Fe fits into this grouping.
Figure 7 (left panel) – Now that only Calbuco ash is included in the figure, the x-axis label should be changed to “ash loading”, rather than “dust loading”.
Figure 7 (left panel) – the lines fitted to each dataset (2 weeks, 4 months, 9 months) are not mentioned in the figure caption.
Figure 7 – The caption (and description in the methods) indicates a 30-minute time-series of Fe(II) measurements, but the x-axis of the right-hand panel clearly extends to beyond an hour. Please clarify in the text and caption.
Line 415 – “Concentrations of up to 4.0 nM Fe(II)” are not evident in Supplementary Figure 2 (which should be referenced) or in the data in Supplementary Table 1. Perhaps 4nM represents one value from replicates of the 4 month old ash, 2mg/L ash loading experiment (2.17+-1.07 nM Fe(II) in the table), but that should be acknowledged in the text.
Line 419 – reference Supplementary Figure 2 also.
Line 431 – in response to a comment from Reviewer 2 the authors provide a reference (Torres et al 2007) to support their interpretation of UV Aerosol Index as a measure of dust/ash aerosol loading. Why not cite that reference here in the text?
Lines 436-438 – reference the appropriate supplementary figure here.
Figure 8 – dashed vertical lines (22nd April) in panels G and H are hard to discern. Perhaps red would be a more visible colour to use.
Line 471 – change “ash fall” to “ash deposition event” to avoid confusion with the fall season, mentioned in the line above (or use autumn instead of fall for the season).
Line 491 – it is stated that the diatom bloom (peaking 14th May based on data available) occurred several weeks after the eruption. This adds to the confusion about collection of the ash sample, which was carried out a week earlier on 6th May. But in response to reviewers the authors state that this collection took place after a third eruptive pulse of ash. This suggests an additional ash deposition event closer to the bloom peak. Please clarify.
Line 544 – See my general point about changes needed to Figure 4 – currently the figure does not show a more modest diatom abundance at Station A, as stated here, but rather at Station B. Also, the authors again state that this date (14th May) is 3-weeks after the eruption – should it be three weeks after the main eruption (see line 491 comment)?
Lines 570-574 – I believe this sentence is added based on a reviewer comment about previous work. In the response to reviewers the authors argue that these lower pH experiments may not be applicable at seawater pH and I think that caveat can be added to this sentence.