Teapotty, I tried to find out how many mesocosm studies this research was based on but until I see the paper I won't know. The phytoplankton communities change in tropical or polar conditions and different members of the phytoplankton community respond differently to acidification. To get a good idea on how different areas of the oceans respond someone would need to run multiple mesocosms . The initial work done shows a 18% methyl sulfide production drop by 2100. Atmospheric Co2 should be over 900 ppm , temps. 4 to 6 C increase on land with an additional .23 to .48 C if this study is correct. Ocean pH will have decreased by ~. 4 and ocean temperature increased by 2 to 3 degrees C. If we actually pull the trigger and get to 900 ppm Co2 by 2100 we will continue to see ocean pH drop between 2100 and 2300. This would require the burning of most of the coal and oil reserves known. It seems like we are still headed to 900 . If we do continue this long enough we can change the average ocean pH by an additional .3 by 2300 with a resultant average surface ocean pH of 7.5
The researchers probably didn't run their mesocosm down to 7.5 pH or the 7.3 potential in arctic waters. Kinda like the difference between running a crash test dummy into a wall at 120 mph or 200 mph. The dummy doesn't make it.