Nutrient uptake kinetics and ecophysiological consequences in 4 North Sea seaweedsNutrient uptake kinetics and internal storage capacities of dissolved inorganic phosphate (DIP) and dissolved inorganic nitrate (DIN) were quantified for 4 North Sea seaweed species, Ulva lactuca, Saccharina latissima, Laminaria digitata, Palmaria palmata. All seaweed species tested showed a biphasic response in uptake rates: surge uptake as a response to nutrient-starvation and maintenance uptake after internal nutrient pools had been filled. In absolute numbers, all seaweed species had different uptake rates and internal storage capacities for DIP and DIN. These differences were translated into different physiological consequences, from growth characteristics to internal composition related to DIP and DIN availability. Some species were well equipped to withstand low periods of nutrient limitation, some were very efficient in DIP and DIN uptake. For the first time ever, a comprehensive insight was achieved in DIP and DIN uptake kinetics, management strategies and physiological effects in these North Sea seaweed species. With this insight ecological effects of nutrient limitations and shifts in limitation can be estimated. And ecological importance of seaweeds in terms of ecosystem services (e.g. DIP/DIN cycling) demonstrated. The results also allow prediction of potential seaweed biomass production in (off-shore) cultivation. This thesis furthermore provides novel concepts for standardized texture analysis on the seaweeds, enabling research into the effects of environmental conditions on the tissue toughness of seaweeds. Finally, an optical analysis to estimate protein concentration in U. lactuca is introduced, which resulted in the EyeOnUlva smartphone app. |
