# Assessment of the Resource Potential of Baltic Sea Macroalgae
## 3 Results
### Seasonal Dynamics of Beach-Cast Macroalgae  
The seasonal dynamics of algae cast on the Baltic Sea coast within the Kaliningrad region were estimated at two model sites 100 m long with the maximum total annual cast, located in the Filinsky Bay, from March 2019 to August 2020. Model site No. 1 was located in the central part of the bay on the east side of the slipway for small boats, and site No. 2 was 200 m east of site No. 1. Both sites had a northern exposure to the coastline. According to data analysis, on the model site 1, the highest levels of algae casts (up to 500-1700 kg dry weight/100 m of coastline) were observed primarily in the spring and summer months of 2019 and 2020. Significant amounts of algae (approximately 300 kg dry weight/100 m of coastline) were also observed in March 2019, during the phenological winter. On the model site 2, the dynamics were diverse. The dynamics of casting show a general trend for both observed sites. However, despite their proximity to each other, the quantitative parameters differ significantly. The average annual indicator for section No. 1 was 197 kg dry wt./100 m of coast, while for section No. 2-66 kg dry wt./100 m of coast. This can be explained by the fact that, despite the identical northern exposure of both beaches, site No. 1 adjoins the slipway on the eastern side. As a result, a type of hydrodynamic trap forms, which aids in the accumulation of algae biomass under certain wind conditions. Throughout the entire observation period, the qualitative composition of casts in both parts of the Filinsky Bay coast generally coincided. There was a clear seasonal dynamic of the species composition of beach-cast algae. In the cold period of the year, the biomass of red algae, primarily due to _Furcellaria lumbricalis_, reached 90-100% (Figure 3) and decreasedto 30-50% in the warm period due to the massive vegetation of green algae of the _Cladophora_ and _Ulva_ genera. A preliminary assessment of the total annual volume of macroalgae casts on the Baltic Sea coast within the Kaliningrad region revealed significant spatial and seasonal unevenness in their distribution [56; 57]. In most cases, casts significant in terms of volume were of a local nature and were mostly confined to areas of the northern coast of the Sambian Peninsula. In total, for the period from March 2019 to August 2020, 22 episodes of significant macroalgae casts in terms of area and volume with a layer thickness exceeding 0.25 m were recorded in six local areas of the coast. The recorded maximum length of the cast was 300 m and thickness was 1 m.  
Content of Lipids, Proteins, Carbohydrates, and Biogenic Elements in the Biomass of the Studied Macroalgae  
The highest content of crude protein was observed in samples of macroalgae of the genus _Polysiphonia_ and amounted to 28.2% of absolute dry matter (a.d.m.). In samples of algae of the genus _Furcellaria_, the content of crude protein was 25.4% of a.d.m. For algae of the genus _Cladophora_, this indicator was 20.8% of a.d.m. The lowest content of crude protein was observed in samples of macroalgae _Ulva_ sp., 17.3% of a.d.m. (Table 3). It was demonstrated that the protein content determined by the Bradford method was significantly lower than that measured using the Kjeldahl method. This may be due to insufficient extraction of protein from the biomass, and also to the fact that the Kjeldahl method also determines non-protein nitrogen in the samples. According to the data obtained by the Bradford method, the highest amount of protein was found in macroalgae _Furcellaria_ samples and amounted to 3.5%. In samples of macroalgae of the genera _Cladophora_ and _Polysiphonia_, the protein content was 3.1% (by the Bradford method). The highest content of reducing sugars (Table 3) was found in samples of macroalgae _Furcellaria_ (21.96%). The content of reducing sugars in algae samples from the genus _Polysiphonia_ was 17.84%, while _Cladophora_ had a content of 13.04%. The lowest content of reducing sugars was observed for _Ulva_ sp., at 11.83%.