This manuscript provides measurements of O2-derived NCP and NOx-derived NCP in a shallow shelf sea environment. UEA and CEFAS have established a strong track record in autonomous Seaglider measurements in this region, and the datasets presented in this manuscript will be a useful contribution. Below are a number of comments below designed to improve the manuscript

1. The initial O2 and NO3-derived NCP estimates from autonomous vehicles were first pioneered by Ken Johnson approx 10-12 years ago. I think O2 based NCP estimates are now fairly common and so the authors dont need to highlight the novelty of autonomous measurements (Lines 94-104). Instead the authors should describe how the SeaGlider sampling strategy was designed to accomplish the study objectives. This information is currently missing from the manuscript.  i.e. what was the scientific motivation behind the East-West transects conducted by the SeaGlider. Not a N-S, butterfly, Eulerian, Lagrangian approach?

2. The manuscript has way too many distractions from the main topic of NCP in shelf seas. This is evident in the abstract where the authors do not provide measured values and becomes highly evident where in the Introduction where only a few lines (Lines 75-77) are about NCP. The rest is about carbon cycling, the Dogger bank ecosystem, deoxygenation, and an AlterECO project. Some NCP concepts are introduced in the methods (Lines 179-181 and Discussion (Lines 274-276) and these should be moved to the Introduction.     

3. There are several other distractions in the manuscript which divert the readers attention away from NCP. These include include the buoy-derived measurements from 12-14 years ago and the in-depth discussion about O2:N stoichiometry.  I suggest the authors think carefully about the content and whether they wish to present a NCP-focused manuscript, a buoy vs SeaGlider comparison manuscript, or an ecosystem-overview manuscript.  At the moment the manuscript tries to cover all three topics and it causes the reader to get a little lost.

4. I dislike the units for O2 and NO3 used in Figure 2, the O2 mass balance units presented in Figure 4, and the units used in Table 1.  For example, Columns 4 and 5 in Table 1 should state O2-based NCP and NO3-based NCP and provide the depth-integrated units. You will lose readers if the data is presented in its current format. I dont think the existing format is used by the productivity/autonomous community.

5. Abstract Line 1 and Introduction Line 13 I dislike the description ‘ecosystem services’ in this manuscript. The publication will (hopefully) be read by non-English speaking readers and they will have no idea what this refers to

6. Abstract Lines 5-10, see comment #2, I was confused why the authors chose to focus on elemental stoichiometry in the abstracts.

7. Line 122 - Initially I wanted to see SML and BML plotted on Figure 2 as I thought it was relevant information but on Line 133, you state that the definition of SML or BML has minimal impact, so now I am wondering why you bothered to even mention it.

8. Figure 1. Where is the mean tidal ellipse shown in red? Is there any significance to the SeaGlider operations occurring ~50 miles to the north of the buoys from 12 years ago?

9. Figure 2. Did you not have a fluorometer? Why is chlorophyll not shown? Seems like this is an obvious biomarker for a phytoplankton bloom

10. Figure 6. I am not sure why observations from 2007-2008 are being compared to 2019. I understand they record NO3 decline during the spring bloom but why not just include them as an extra Line in Table 2. In the current format, the readers attention gets distracted from the Seaglider observations.

I have read the manuscript "Simultaneous assessment of oxygen and nitrate-based net

community production in a temperate shelf sea from a single ocean glider"

by Tom Hull and coauthors and found it interesting to read.

BG review criteria:

The paper describes analyses of data from a glider deployed North of Dogger Bank

in the North during spring bloom season which is an appropriate subject for BG.

The glider was equipped with a (still) novel lab-on-a-chip sensor for NOx measurements. 

Using these new data together with the

more common pressure, temperature, salinity, and oxygen data allows for the observation

and analysis of properties such as e.g. the O2:N ratio during the bloom. As these

properties might change under a changing climate these observations can be seen

as a pilot study for possible monitoring systems.

The findings support the feasibility of such a system and are clearly described.

The results support the interpretations and conclusions.

The description of the experiments is sufficient and the calculations can

in most cases be followed. In a few cases (see below) some alternative

units could make it even easier. And some additional explanations/definitions would

be helpful for the less well versed reader.

The authors give credit where due and adequately mark their own contributions.

The title is adequate.

The abstract gives a complete yet concise description.

The overall presentation is fine.

The language is very good.

Formulae are mostly correctly defined and used. Some additional definitions/explanations

will be helpful. See below.

No significant parts of the paper require reorganization.

The references are appropriate.

General comments:

As a physicist I have difficulties with the 'net community production in equivalents'. See e.g. Table 1.

Could you please explain how they are calculated. In appendix A1 I can find a definition for 

J. Is that J(O2)? But nowhere I can find a J(NOx) definition. 

As this is a calculation at the heart of the paper, it should be described better.

I would like to see the title include the LoC sensor.

I found it at times difficult to compare the numbers within the paper. That is between the 

integrated properties and the concentration properties. Lines 231 to 235 are a good example.

In the same sentence you use the change in concentration and the inventory. While I am 

able to divide by 40, I would very much prefer to have a consistent scaling. Maybe you

can for each inventory number also give an average concentration in parenthesis. And in line

234 shouldn't 40 * -4.5 = -180 be the same as the 214 +/- 7 drawn down to 0, or am I getting something wrong?

Similarly I have difficulties following the jumping between unit prefixes. Sometimes you use

mol sometimes mmol. I would prefer a continuous use of mmol, even if the numbers are 1000* larger.

Detailed comments:

- title     You use 'nitrate-based' here, but measure NOx later. A common problem when describing these

            sensors for which I also do not have a good solution.

- line 153  How do you 'extrapolate' the salinity from the descent to the ascent?

            Using temperature as reference or pressure?

            

- line 163  'down to a 40 m depth'    drop the 'a' ?

- line 205  You write the 'tidal advection was 5 km over 25 hours'. Do you mean the full length

            moved around the tidal ellipse? Then the ellipse in Figure 1 cannot be to scale.

            I would estimate the circumference of the red ellipse to be more like 20-25 km.

            Either state 'not to scale' in the caption or draw it smaller or correct the number in

            line 205. Or correct me ;-)

            

- line 231  'based on average depth'. Is there a 'the' missing?

- line 233  I would always write 'between ... and' or 'from ... to' not 'between ... to'

- line 233  I get slightly different numbers from Figure 3.

            (0.4-0.04)*1000/40/12 = 0.75 mmol/m^2/d

            (0.54-0.16)*1000/82/12 = 0.39 mmol/m^2/d

            Or am I calculating something wrong?

- line 234  the same

            -4.5 mmol/m^3 * 40m = -180 mmol/m^2 = -0.18 mol/m^2  over 12 days

            in Figure 3 this looks different. More like -0.36 mol/m^2 over 12 days

- line 244  Are you sure about the 1% ? I get more than 2% for a 1 deg change.

- line 245  Something is wrong with this sentence. You say 'Productivity J(O2) is increasing'.

            But don't you actually mean 'Produced biomatter is increasing' ?

            To me 'productivity' is a derivative of an amount (or if per unit volume of a concentration).

            And in the same sentence you say there is a 'marked drop in productivity' when NOx is used up

            which I would think is correct.

            

- line 263  'partitioning of the oxygen and NOx−across the thermocline'

            looks like the 'the' is too much

            

- line 327  'was cooler then 2007'    than 

- line 536  Something is missing in 'by calculating the change oxygen inventory'.

            Maybe 'in the'?

- Figure 1  Axis labels are missing and the numbers could be bigger.

- Figure 5  Numbers are missing from the axes. I think, if you give numbers for the slopes,

            you should give numbers for the axes too. I understand that this is a conceptual

            diagram, but it still looks 'odd' without them.