Long photoperiods sustain high pH in Arctic kelp forests Dataset

This dataset contains field- and laboratory data of metabolic activity, photosynthetic characteristics and associated effects on water chemistry of Greenland kelp forests. Field data include diurnal variation in pH, pCO2, O2-concentration, light, temperature, and salinity in shallow kelp forests habitats over 10-day periods in the subarctic Kobbefjord (64???N, 51???W) in late summer 2013 at a photoperiod of 15 h light and in the Arctic Disko Bay (69 ??N, 53 ??W) during midsummer 2014 at a photoperiod of 24 h light. Field data further include in-situ measurements of photosynthetic activity (relative electron transport rate, rETR) during a diurnal cycle in midsummer in Disko Bay. Laboratory data include time series of seawater pH, CO2 concentration and rates of change of CO2 concentration and photosynthetic activity of arctic vegetation measured during experimental manipulations of photoperiod and CO2 concentration in aquaria at 4 oC. There were three replicated aquaria per CO2 concentration treatment (200 ppm, 400 ppm and 1000 ppm). Each aquarium contained 6 L of artificial seawater and 2.7 ??? 3.7 gDW of macrophytes (Ascophyllum nodosum, Fucus vesiculosus, Saccharina longicruris, Zostera marina) collected at Nuuk. Methods are described in detail in Krause-Jensen et al. (2016).