off-course your data is interesting because primarily pH value high(just 2007) but in middle low after that slightly increase in your pH value July 2011 onwards,its shows against ocean acidification. but can you measure air and water temperature of relative time points. i am wondering about your salinity data because it is so high approximately 43 ppt.so why salinity is so high.

The data appear typical of annual pH cycles recorded elsewhere. Most studies of acidification report annual cycles with higher pH in winter months and a drop-off as temperatures and plankton abundances increase (more O2 used, more CO2 produced), followed by another increase as you approach colder temperatures. We see this in both coastal waters and nearshore sediments (muds). The single parabolic fit is misleading in this case and I think you need to look at cycles alongside this overall trend. I'm not sure that I agree with Tarkeshwar Singh that the slight increase in pH from July 11 onward indicates a reversal of acidification, but it would be interesting to monitor these data further.

What's interesting to me is the large drop in pH during Nov-Dec 09. Do you have any speculation as to what may have attributed to this drop? Also, have you collected any other chemical data to go along with your pH measurements (i.e., total alkalinity or DIC)?

Kenneth will send you the coordinates soon am currently on move with little internet access and the data is at base. Mostly these are coastal stations.

Manuel your concern regarding salinity is valid and I wanted to have a look at data as models and hypothesis sometime disregards these observations since they don't go well with popular belief. The background is Iranian coast is having slightly lower salinity as the water enters from Indian Ocean through strait is Hormuz from the eastern coast these measurements are of western coast where 11 million m3 of desalinated water is produced daily and the amount of brine discharged is 35 million m3. With little fresh water input and a residence time of 3-5 years this salinity is expected we get around 39-41 near boubou an island where Shaat al arab river discharges.

Jeff unfortunately I don't have alkalinity and DIC data prior to 2011 but we aed doing these measurements for over 2 years now. There is a drop in alkalinity.

Suggestions and interpretations are welcomed. Regarding oceanic productivity yes the chl-a abundance is there during summers but the sea weeds and other macro algae are abundant during the winters if it has any thing to do with pH perturbations.

Hi Saif,

Your work here is very interesting and I'd certainly like to learn more about it! I would say the chlorophyll-a (i.e., increased productivity) in the summers and the abundance of macroalgae and seaweed in winter are certainly influencing your trends. In comparison to my above comment regarding the increase in plankton during the summer driving CO2 levels up and decreasing the pH, we know that seaweeds and macro-algae actually take up CO2, and would therefore contribute to a decrease in CO2 and an increase in pH during the winter. This is consistent with your data and, again, coincides with trends seen elsewhere. However, it is important to recognize that marine carbonate chemistry is not so cut and dry, but is very complex. It would not simply be the plankton and seaweeds driving your trends, but other factors are certainly at play as well. With that said, your data makes sense to me and is quite interesting, with pH changes seemingly driven by algal dynamics, and an overall decrease over time!

I'm still interested in the sharp decline in pH during Nov-Dec 09. Have you looked into this? I think it is certainly something worth exploring. An unexpected algal bloom? Seaweed harvesting?

I have a couple of other questions for you as well:

1. How did you measure pH? Were you simply dropping a probe off the side of a boat at different times of the year, or did you have a sensor deployed for given periods of time?

2. If you've started taking measurements of DIC and/or total alkalinity, you can easily derive estimates of the carbonate saturation state (usually with respect to aragonite) using those parameters coupled with temperature and salinity (and chl-a if you have those measurements as well, but these are not critical). Have you looked into this?

Jeff am on move these days hopefully will be at base tommrrow evening, will re0ply to you in details. I will certainly get in touch with you to see how to improve the interpretation of thsi dataset.

Jeff these pH measurements are done at fixed stations as a continous measurement using hydrolab and YSI instrements .

Kenneth these stations are in western Persian Gulf essentially all are within 20 Kms from the shore. Are you interested in precise coordinate or approximate location.

Thank you Saif - my apologies for the extremely late response here. With respect to your instruments, did you test/calibrate for data drifting and potential discrepancies between the two different types of instruments?

Yep we do Jeff. These instruments undergo triple point calibration using NIST reference material.

Thanks Saif! That's great. How often are the instruments calibrated?

I'm very interested to see the carbonate saturation data once it is obtained!

The instruments are calibrated on weekly basis.

I will share teh data soon. I will upload alkalinityt measurements we have doen over past 3 years, soon.

Hi,

Do you have any biologists working on these issues?

@Sam Nope are you interested?

@Saif I am biologist, I am interested