Reply on RC2

The authors show phytoplankton growth and grazing mortality by microzooplankton based on the result from dilution experiments. In my knowledge, dilution techniques are somewhat difficult for researchers and thus large numbers of data sets have been unavailable. Even under these difficulties, the authors demonstrate excellent data sets not only from the dilution experiments but also detail measurements on environmental variables. I believe that this study provides a good example for phytoplankton dynamics in the fluctuated environments. On the other hand, some disadvantages are found in the present study as follows.

I am afraid to say that current conditions of this manuscript need moderate revisions. I would be very happy if the authors provide more suitable descriptions and discussions on the above issues and conduct major revisions.
Response: We thank the reviewer for these constructive comments. We have taken all of them during our revisions.

Specific comments
L35: the cycling of carbon and nutrients in the ocean Please add brief description why they regulate carbon and nutrients cycle, here.
Response: Done. The sentence has been rewritten as "Microzooplankton are generally the dominant herbivores in the marine ecosystem (Calbet and Landry, 2004), regulating not only primary productivity but also carbon export via vertical migration/pellet sinking and nutrient recycling by mixotrophy (Steinberg and Landry, 2017)".
L99: After returned to the laboratory Could you tell the readers how many minutes do you take from the study station to land laboratory? I am just wondering whether microzooplankton grazing and excretion affect samples for chlorophyll and nutrients measurements. For our information, you can add the durations here, such as "after return to the laboratory (<1 hour)".
Response: Thanks for pointing out this. It was less than one hour. The duration has been clarified in the revised manuscript.
L122: carried out directly at a coastal pier near the sampling site This description was unclear. We cannot understand where you take water samples for the experiments and incubate these waters in the bottles. All procedures including water sample collections for experiments were conducted at the coastal pier? If so, you need to discuss the regional difference between the station and the coastal pier. Please mention them clearly.
Response: Sampling collections were made at the offshore station 500 m away from the pier. The incubation experiment was conducted at the pier with the running seawater for temperature control in the incubator directly taking from the nearby surface seawater (There was no difference in temperature detectable between the sampling seawater and the seawater near the pier).
L128: 5 μmol l-1 NaNO3, 0.5 μmol l-1 KH2PO4 I understand you determine these concentrations based on the previous experiments. In my knowledge, the N:P ratio is also important for regulating phytoplankton growth. Could you provide some explanations why you determine this N:P ratio (ca. 10) far from Redfield ratio (16) and observed ratio (>20)?
Response: We did not choose the Redfield N:P of 16 in our nutrient-enriched experiments as the N:P ratio about 10 is sufficient for a large phytoplankton growth due to a persistent high N/P ratio of the local surface seawater driven by river discharge, similar to those used by Chen et al (2009).
L145: The intrinsic growth rate (μ0) is calculated as the sum of the net growth rate without nutrient enrichment (ε raw ) and the grazing rate The authors should add another equation or alternative description on phytoplankton growth rates. As mentioned later, most of the readers who are not familiar with dilution experiments are confused for several phytoplankton growth rates that the authors mentioned. Currently, at least, the authors used the following growth rates and these terms should be defined clearly in Method section. apparent growth rate at each dilution factor growth rate at non-dilution without nutrients enrichment apparent growth rate at non-dilution with nutrients enrichment intrinsic growth rates (growth rate 3 minus microzooplankton grazing) Response: Sorry for the confusing terms. We have clearly redefined these rates into three distinct groups (ε: apparent growth rate; m 0 : natural growth rate; m n : nutrient-enriched growth rate) and we have also differentiated them between rate for total community and rate for each size-class. We have unified them throughout the manuscript. The relevent text in the method section is now written as the attached PDF (text1.pdf) L192: which may indicate an extra utilization of P compared to other nutrients. Likely, an increased P consumption could occur here given the phosphorus deficiency driven by very high N/P ratios.
This phrase involves some assumptions and discussions. I think this should be deleted or moved to discussion.
Response: Agree. We have deleted this in the revised manuscript.
L210: 1220 ind L -1 Why don't you estimate carbon-based biomass like pico-sized autotrophs? Ciliate/TChl is semi-quantitative values due to the different cell size between aloricates and tintinnids. Numerical abundance of microzooplankton is comparable to the other quantitative numbers like nutrients, growth rates and grazing mortality rates?