In-situ measurements are important for the study of lake ecosystems as several biogeochemical processes in the water column are confined to very narrow zones which can be highly dynamic in time and heterogeneous in space. New insights into these reactions can only be gained by in situ observations at high spatial and temporal resolution. Current practices involve sampling with devices like Niskin bottles. Such classical sampling tools typically integrate measurements over half a meter due to their dimensions. Moreover, biases in results can be introduced due to preservation and storage of samples as well as from changing environmental conditions, when deep water samples are brought to the surface. Modern sensor technologies promise to overcome the limitations of such classical analytical practices. Existing platforms are often equipped with sensors for various physical parameters like temperature, conductivity, photosynthetically active radiation (PAR) and chemical parameters like pH, O2 and sulfide. Still, reliable sensors for in situ profiling of chemical species relevant to carbon, nitrogen and phosphorous cycles are lacking. Ion selective electrodes (ISEs) have not been used widely in lakes owing to limitations in their detection limit and problems of pressure compensation. The presented work combines recent developments in the field of solid contact ion selective electrodes (SC-ISEs) and demonstrates the possibility of gaining new insights into aquatic ecological processes. To achieve the goal of high resolution profiling of nutrients and inorganic carbon species, new solid state sensors were fabricated with materials and designs suitable for measurements in lake waters and robust to changes in redox conditions, reactive solutes and physical changes. Furthermore, we developed an in situ calibration protocol, which accounted for drift and interferences that are inherent with these type of sensors.