Varying organic content in fish otoliths: Effects on SIMS-based δ18O measurements and possible corrections

The data in this dataset was collected by sampling 113 otoliths from northern pike along environmental gradients in Baltic Sea brackish lagoons, their freshwater tributaries, and a reference freshwater lake in Brandenburg, Germany, lake Kleiner Döllnsee. Measurements of stable oxygen isotopes as thermal marker and hydroxy ions as an indicator for organic matter were taken from the otoliths using secondary ion mass spectrometry (SIMS) at the GeoForschungsZentrum Potsdam. Electron microprobe (EPMA) scans of calcium (Ca), magnesium (Mg), phosphorus (P), sulphur (S), and strontium (Sr), were taken as 10 um spatial grid patterns of three representative otolith specimen. A spatial SIMS grid of 35 um was taken of one representative otolith speciemen. Measurements of water isotopes, water temperature, salinity and turbidity were taken for interpolation of expected otolith d18O values. Annual otolith increments, along with age information, were used to asssess growth performance at the individual level.