Seasonal and Interannual Trends of Oceanographic Parameters over 40 Years in the Northern Adriatic Sea in Relation to Nutrient Loadings Using the EMODnet Chemistry Data Portal
, Francesco Acri 4, Fabrizio Bernardi Aubry 4, Caterina Bergami 5, Marina Cabrini 6, Alessandra Campanelli 1, Michele Giani 6, Stefano Guicciardi 1, Mauro Marini 1,3, Francesca Neri 2, Antonella Penna 3,7, Pierluigi Penna 1, Alessandra Pugnetti 4, Mariangela Ravaioli 5, Francesco Riminucci 5,8, Fabio Ricci 3,7, Cecilia Totti 2, Pierluigi Viaroli 9 and Stefano Cozzi 10Round 1
Reviewer 1 Report
Seasonal and interannual trends of oceanographic parameters over 40 years in the northern Adriatic Sea in relation to nutrient loadings from EMODnet Chemistry data portal.
By Federica Grilli et all.
Comments and Suggestions for Authors:
This study aimed to analyze the seasonal and interannual variability of hydroligycal and biogeochemical parameters in NAS using data from EMODnet Chemistry data portal. Influence of river discharge on seawater properties was also considered. This manuscript is interesting and novel. However, there are some questions that should be answered before the manuscript can be published. First of all I would ask you to check the data for NO3, there are some very high concentration (the same level as in the river) that should be explain or deleted from the dataset. I would also recommend you to divide the dataset for coastal water and open water to get better signal for both seasonal and interannual changes caused by river inflow and climate changes. See more detailed comments below.
Please correct the title, change “in relation to nutrient loadings from EMODnet …”. EMODnet is not a source of nutrient
69 - What do you mean by negative changes in plankton community composition? Please explain or rephrase.
99 – the 100 m isobath position is not shown in the map
104-109 – Here you describe water mass circulation in the NAS that is important but is not clear enough – does water mixed to the bottom, do you have resuspension, is there water stratification in the NAS? Please describe in more detail the characteristics of MLIW and the densest Mediterranean water mass, its T, S, nutrient content. I would like to have more information here since hydrodynamic processes in NAS play very important role for this study.
114 – data per year of what? Do you mean number of stations, number of samples, number of all the measured variables (phosphate and nitrate etc., together)?
141 – what is the number of data used in the study? Is this number - all parameters together for all studied period? I would like to have more information here, number of measurements/stations for each parameter for each year.
- Figure 2 – impossible to see scales, please increase the font size. What data were used here? Aggregated?
- Table 1. What data were used here? Aggregated?
227-228. data for S and NO3 does not match your statement about their inversely relationship. In Table 1, aggregated data - lowest salinity correspond to lowest NO3 conc (summer). In fig .4, spring, you have increasing trends both for salinity and NO3 conc. And in Fig 3 both parameters have increasing trends. You explain in the text the reason of low aggregated salinity in summer and high in the autumn. But if you want to get a clear trends for changes caused by river inflow or climate change you should divide your dataset for coastal water and open water.
203, 255, 268. Table 1, Fig 3 and 4. NO3 data show very high concentrations in 2012 and 2013 years that are the same level as in the river. This should be checked and or deleted from the dataset or explained. These values are the main reason for the increasing trend of NO 3 you discussed.
263-264. What is the most recent period? there is no data for S for last decade in the paper. Please provide years to be able to compare.
272-274. Decrease in Chl-a in 2003-2008 is not seen from your data. In 2003-2008 period there is no Chl-a data for spring and summer periods and just couple of stations for other seasons. Please rephrase/site another work.
- As I can see, for 2010 you have Chl-a data for autumn period only. It is difficult to speak about increasing trend from 2010, please rephrase.
309-311. You say that PO4 availability in the NAS depends mainly on the remineralization of Porg. How does it work for NAS surface waters? Water stratification will affect supply of PO4 from deep water. Does increase in surface temperature affect stratification and therefore PO4 conc? If you divide your dataset for coastal water and open water maybe you could find interesting results connected to the climate change.
- by increase of nutrient concentration you mean nitrogen? Because you do not have increase of P… Please check.
- “... lead to higher concentration …of organic matter composition” – please check the sentence.
410-434. Were there any changes in plankton community during two studied periods. Perhaps, it could be discussed here.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Title: Seasonal and interannual trends of oceanographic parameters over 40 years in the northern Adriatic Sea in relation to nutrient loadings from EMODnet Chemistry data portal
The authors adopted the long-term data to evaluate the climate change influence and anthropogenic activities on the northern Adriatic Sea (NAS) region. Based on these data, this article pointed out that the distributions of salinity, chlorophyll-a, and nutrient in the NAS are effected by the Po River discharge, and there was an obvious rising temperature on the sea surface. The authors also provided well literature reviewer and statistical analyses to support their results.
Major opinions:
- Could the authors analyze these data based on the repeated sampling locations or grid areas?
The aggregated data confused me a lot since I have no idea about the sampling stations. Figure 1 shows the sampled locations from 1971-2015, but that doesn’t provide enough spatial information for different years. The authors mentioned in Line 144 “in oceanographic cruises and in fixed-point monitoring stations”. If the oceanographic cruises don’t repeat the sampling stations, the directly calculated average results will bring some issues. For instance, the highest two discharges (Table A1) are in spring and autumn, but the lowest two salinities are in spring and summer. Based on the authors’ suggestion, the nutrient concentrations should be relative to salinity value. However, the highest two nutrient concentrations are in spring and autumn, as river discharge. Figure 8 also shows that the sampling locations changed with time.
- Could the authors provide riverine nutrient fluxes? Since that provides more direct information for how many nutrients were delivered to the NAS.
Minor opinions:
- Could simplified annual or seasonal averages with standard error ranges be provided in Figure 3-5?
- Table 1 and Table A1 should include the sample amount.
- The mentioned location such as the Istria peninsula should be provided in Figure 1.
- The time periods are not consistent. For instant: Lines 114, 143: -2015; Line 273: -2016.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
In general I agree with the revision and I now consider the manuscript worthy for publication.
The main limitation remains on the data control for NO3 concentration. The authors hadn’t explain the observed very high concentration of NO3 in 2012-2014 years (from the figures it is difficult to say exactly which year it is). These values are of the same level as in the river and were observed in one year in the spring and one year in the autumn. These values are the reason of the increasing trend in NO3 that is one of the main results of the manuscript. If authors don’t want to remove these values from the data set, they should write more why you believe them. It could be an extreme weather conditions (extensive runoff, tornado, flood, wind) or something else. Or it could be just an analytical error…
The authors write in the abstract and conclusions that “These changes (in nutrients dynamic) indicated that phytoplankton communities in the NAS have been largely modulated in the last forty years by…”. In the text there is no any word about any changes in phytoplankton communities. If the authors put such statements in the abstract and conclusions, it should discuss it in the manuscript, especially in paragraph 3, and the authors are certainly familiar with these results (Totti et al., 2019).
The authors use different terms – Oceanographic, hydrological and biogeochemical parameters, sometimes merging everything in “oceanographic”, sometimes separate them (i.e. “oceanographic and biogeochemical” or “hydrological and biogeochemical”). Please check in the whole manuscript.
Line 152. “1 nautical mile” should be “1 nautical mile from the coast”
Line 274-275. The authors don’t have Chl-a data from about 1997, not from 2003 as it is written. It makes no sense to write here about the period 2003-2006. Just remove the second part of the sentence.
Line 416-440. Could the authors write here average nutrient concentrations for two discussed periods to better presentation of their results.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The EMODnet Chemistry dataset allowed to make only these considerations since oceanographic cruises are not always repeated in space and time. It is a random collection of measures of different research projects.
If the authors like to mention potential estimated error for the randomly sampled location, that will be more persuasive.
Author Response
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Author Response File: Author Response.docx
