In this study, measurements of the light curve were taken to assess photosynthetic competence in Vaucheria algae. The Chl a fluorescence of photosystem II (PSII) was measured using a pulse amplitude modulated fluorometer. The maximum quantum yield (Fv/Fm) and electron transport rates (ETR) were determined in dark-adapted samples. The light curves were measured by varying the light intensity in 10 steps and recording the effective quantum yield. The data were then analysed using a model known as the photosynthetic light response curve, which describes the relationship between ETR and light intensity. The model assumes that ETR increases linearly with light intensity at low levels, but then slows down and approaches a maximum value (ETRmax) at higher light intensities. The half-saturation constant (k) represents the light intensity at which the ETR is half its maximum. These parameters, ETRmax and k, play a crucial role in understanding the photosynthetic properties of algae under different light conditions. The data were analysed using nonlinear least squares estimates of the parameters in R Studio.
In this study, measurements of the light curve were taken to assess photosynthetic competence in Vaucheria algae. The Chl a fluorescence of photosystem II (PSII) was measured using a pulse amplitude modulated fluorometer. The maximum quantum yield (Fv/Fm) and electron transport rates (ETR) were determined in dark-adapted samples. The light curves were measured by varying the light intensity in 10 steps and recording the effective quantum yield. The data were then analysed using a model known as the photosynthetic light response curve, which describes the relationship between ETR and light intensity. The model assumes that ETR increases linearly with light intensity at low levels, but then slows down and approaches a maximum value (ETRmax) at higher light intensities. The half-saturation constant (k) represents the light intensity at which the ETR is half its maximum. These parameters, ETRmax and k, play a crucial role in understanding the photosynthetic properties of algae under different light conditions. The data were analysed using nonlinear least squares estimates of the parameters in R Studio.
Temperature, Salinity, pH, oxygen and chlorophyll data was collected with a Hydrolab HL7 multi parameter sonde installed on an oyster table in the Oddewatt oyster reef in Königshafen, Sylt, Germany (55.028483, 8.433876). The table and sonde surface during low tide.
We analyzed concentrations of dissolved rare earth elements (REE) across the land-ocean continuum in the German Bight (southern North Sea) to identify key drivers for REE cycling in dynamic coastal environments. We identified the coastal transition zone as a critical interface for altering predominantly riverine-derived natural and anthropogenic REEs. We combined shale-normalized REE patterns, measured by quadrupole inductively coupled plasma-mass spectrometry (Q-ICP-MS), with biogeochemical bulk parameters and molecular analysis of dissolved organic matter (DOM) determined by ultrahigh-resolution mass spectrometry (FT-ICR-MS). Samples were acquired during RV Heincke cruise HE527. The dataset includes spatially resolved biogeochemical data (concentrations of chlorophyll-a, dissolved nitrogen, dissolved organic carbon, suspended particulate matter, dissolved iron, dissolved manganese and dissolved REE) in surface waters obtained along the major estuarine transects (Ems, Weser, and Elbe), coast-orthogonal transects and an offshore North Sea transect, with additional deep-water samples. Temporally resolved data were collected near the barrier islands Langeoog and Spiekeroog including the Otzumer Balje inlet. The dataset also contains molecular indices based on DOM composition (see Speidel et al. 2024, https://doi.org/10.1007/s10533-024-01117-3) REE subgroups, ratios and concentrations of anthropogenic Samarium and Gadolinium (for details see Mori et al. under review).
Continued population growth increases the demand for space and resources, which in turn enhances anthropogenic pressure on coastal seas. Biotic and abiotic ecosystem understanding in a wider context is essential for effective management of stakeholder interests. This study is a synthesis of recent findings based on short-lived radium isotopes in the shelf ocean North Sea and uses the isotopes to quantify relevant sources and sinks in biogeochemical cycles in the coastal sea in order to enhance system understanding.
We improve upon the previously designed box model for the southern North Sea by Burt et al. [2014], using a denser data coverage for nearshore areas. Specifically, the updated model considers decay-supported desorbable Ra from suspended particles and input from submarine groundwater discharge. The model quantified a total of five source terms for Ra: the Wadden Sea, rivers, desorption from suspended particles in the water column, submarine groundwater discharge from beach systems, and porewater exchange at North Sea bottom sediments; whereas considered losses are radioactive decay and mixing with the open North Sea. The mass balance reveals that porewater exchange, e.g., ripple flow, significantly dominates the total short-lived Ra isotope discharge to the southern North Sea. An eddy diffusion based Ra approach was not successful to quantify submarine groundwater discharge from beach systems, due to other major inputs of Ra isotopes from the adjacent Wadden Sea and river discharge, superimposing the minor submarine groundwater discharge from beaches.