Spatial Distribution of Pine Pollen Grains Concentrations as a Source of Biologically Active Substances in Surface Waters of the Southern Baltic Sea

Pine pollen is a very important component of the marine environment: it is a valuable source of both carbon and macro- and microelements, and it is also a major food resource for many marine organisms. Its characteristic optical properties distinguish it from other suspended particulate matter (SPM), but it can also distort measurements of the latter. Hence, it affects a range of sea water properties as well as a number of key biogeochemical processes taking place in the marine environment. Pollen concentrations were determined with satisfactory accuracy in samples of sea water taken from selected stations in the southern Baltic Sea in May 2018. This paper aims to highlight the spatial differentiation of pollen levels in southern Baltic surface waters and to show that pollen in May is a significant, hitherto overlooked, source of a great many substances essential for the ecosystem’s functioning. Our measurements indicated that pollen was present over the entire area of the southern Baltic studied. Spatially, its concentrations in surface waters differed very widely. Very high levels were recorded both very close to the shore and a long way from it. Any analysis of the influence on the ecosystem of the various substances that pollen brings to the water must take into account the ratio of the concentration of pollen to that of other SPM in the ecosystem. This study showed that even a small concentration of SPM in the central Baltic means that pollen grains can periodically supply substances key to the ecosystem’s functioning. In many areas, pine pollen can make up as much as ca. 50% of the SPM in the 1.25–250 µm size range.