Although the processes occurring at the front of an ice face in tidewater glacier bays still await thorough investigation, their importance to the rapidly changing polar environment is spurring a considerable research effort. Glacier melting, sediment delivery and the formation of seabird foraging hotspots are governed by subglacial discharges of meltwater. We have combined the results of tracking black-legged kittiwakes Rissa tridactyla equipped with GPS loggers, analyses of satellite images and in situ measurements of water temperature, salinity and turbidity in order to examine the magnitude and variability of such hotspots in the context of glacier bay hydrology. Small though these hotspots are in size, foraging in them appears to be highly intensive. They come into existence only if the subglacial discharge reaches the surface, if the entrainment velocity at a conduit is high and if there is sufficient macroplankton in the entrainment layer. The position and type of subglacial discharges may fluctuate in time and space, thereby influencing glacier bay hydrology and the occurrence of foraging hotspots.

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Macroalgae are the source of many harmful allelopathic compounds, which are synthesized as a defense strategy against competitors and herbivores. Therefore, it can be predicted that certain species reduce aquaculture performance. Herein, the allelopathic ability of 123 different taxa of green, red, and brown algae have been summarized based on literature reports. Research on macroalgae and their allelopathic effects on other animal organisms was conducted primarily in Australia, Mexico, and the United States. Nevertheless, there are also several scientific reports in this field from South America and Asia; the study areas in the latter continents coincide with areas where aquaculture is highly developed and widely practiced. Therefore, the allelopathic activity of macroalgae on coexisting animals is an issue that is worth careful investigation. In this work, we characterize the distribution of allelopathic macroalgae and compare them with aquaculture locations, describe the methods for the study of macroalgal allelopathy, present the taxonomic position of allelopathic macroalgae and their impact on coexisting aquatic competitors (Cnidaria) and herbivores (Annelida, Echinodermata, Arthropoda, Mollusca, and Chordata), and compile information on allelopathic compounds produced by different macroalgae species. This work gathers the current knowledge on the phenomenon of macroalgal allelopathy and their allelochemicals affecting aquatic animal (competitors and predators) worldwide and it provides future research directions for this topic.

Dissolved organic carbon (DOC) concentration and fluxes from four rivers draining the catchment of the Puck Lagoon in southern Baltic are presented. Water samples from rivers and coastal zone close to the rivers' mouth were collected from April 2015 to March 2017. DOC was measured using high temperature catalytic oxidation with an NDIR detection. DOC concentration in rivers as well as area specific load discharged to the lagoon reflected variations of land use along their course. Area specific load of DOC discharged by rivers with high proportion of forests, meadows, and pastures in the catchment was significantly higher as compared to rivers with catchment dominated by arable land. However, the main controlling factor of the total discharged loads of DOC was the water flow. The highest loads were observed during the downpour. That was due to the larger volumes of water transported with rivers and the higher concentration of DOC resulting from increased leaching from the catchment area. The obtained results are especially important in the light of climate change in the southern Baltic region. According to the forecasts, we can expect increased precipitation and flooding and consequently increased leaching from the catchment and transport of DOC to the sea via rivers.