Gradients of Plankton and Its Bioluminescence Across the Northern Shelf of the Black Sea (2011-2023)

The distribution of shelf resources is spatially heterogeneous. In this respect, understanding their spatiotemporal gradients is of fundamental importance, since it helps update models and resource management. Data from six summer expeditions carried out from 2011 to 2023 were used to estimate along-shelf and cross-shelf spatial gradients of bioluminescence intensity, phytoplankton, and zooplankton biomass in the upper mixed layer and down to the seasonal thermocline. Plankton samples were collected along transects and oceanographic station grids. The spatial gradients varied from twofold to two orders of magnitude. The ratio of scale of the cross-shelf to along-shelf gradient was a multiple of six. It indicated the cross-shelf gradient's dominant role in mediating the pelagic community's spatial structure. The ratio of scales with equal gradients should be considered when monitoring pelagic shelf ecosystems.