# Assessment of the Resource Potential of Baltic Sea Macroalgae
## 3 Results
### Spatial Distribution of Beach-Cast Macroalgae  
An analysis of the features of the spatial distribution of beach-cast algae on the coast of the Baltic Sea within the Kaliningrad region made it possible to identify their significant spatial and seasonal heterogeneity. From March 2019 to September 2021, the coast of the Sambia Peninsula experienced 22 episodes of significant macroalgae cast in terms of area and volume. In most cases, casts were local in nature and were mainly confined to six districts: Zaostrovye on the east side of Cape Gvardeisky (the most significant cast was recorded in August 2019, with a length (L) of 150 m, with a maximum layer thickness (h) of up to 0.35 m, (Figure 2a), west of the mouth of the Zabava River (August 2019, L = 200 m, h up to 0.45 m (Figure 2b), the settlement Otradnoe (June 2020, L = 250 m, h up to 0.50 m (Figure 2c), Filinsky Bay (July 2019, L = 250 m, h up to 0.35 m (Figure 2d), the western part of the beach in Baltiysk (July 2019, L = 70 m, h up to 1.0 m (Figure 2e), and the western part of the beach in Pioneersky (July 2019, L = 50 m, h up to 0.30 m (Figure 2f)). Figure 2: Algae casts of large volume, the layer thickness exceeds 0.15 m: **(a)** Zaostrovye settlement from the east side of Cape Gvardeisky, 28 August 2019; **(b)** coast, west of the mouth of the river Zabava, 31 August 2019; **(c)** Otradnoe settlement, 20 June 2020; **(d)** Filinsky Bay, 10 July 2019; **(e)** the western part of the beach in Baltiysk, 17 July 2019; **(f)** Western part of the Pioneersky beach, 25 July 2019 (photos by [PERSON]). Significant beach-cast algae occurrences were after stormy weather. So, in July 2019, after storm episode from 27 June-7 July 2019 with northwestern winds up to 20 m/s, algae casts layer exceed 0.15 m and were recorded in four local areas located on the northern coast of the Sambian Peninsula, as well as on the beach of Baltiysk. The maximum observed length of a continuous patch of beach-cast macroalgae was 250 m (Filinskaya Bay), the largest layer thickness was 1 m (western part of the beach in Baltiysk). The width (from the water edge deep into the beach) of continuous patches was 1-20 m. After storm lasted from 11 till 13 March 2020 with northwestern winds up to 20 m/s, macroalgae casts with layer thickness more than 0.15 m were observed at three sites along the northern coast in March 2020. The maximum observed length of a continuous patch of macroalgae cast was 300 m (the beach of the village of Otradnoe), and the largest layer thickness was 0.6 m (Filinskaya Bay). During the warm season, June-September 2019 and 2021, in the absence of strong surf, fragments of beach-cast macroalgae and sea grasses were found almost throughout the Russian part of the Baltic southeastern coast. Narrow cast bands, not exceeding 0.5-1.0 m wide, in which macroalgae did not form a continuous projective cover, were found along the entire seacoast of the Kaliningrad region and had a length of up to 1 km (the beaches of Yantarny and Zelenogradsk). Most of the continuous accumulations had an average layer thickness not exceeding 0.15 m. With the exception of a few isolated regions, most of the Russian sea shoreline had just single fragments of algal thalli that did not form clusters during the cold season. Thus, on the northern coast of the Sambia Peninsula, large volumes of beach-cast algae were observed, in contrast to the western coast and the Vistula and Curonian Spit, especially in the period from late autumn to early spring, when the main biomass of the beach-cast algae was formed by species of the red algae _Furcellaria lumbricalis_. This is perhaps attributable to the presence of a belt of these algae in the Cape Taran area [55]. During the summer, representatives from the green algae division played a key role in casts along the whole length of the Kaliningrad region's seacoast, with the majority of the species being annuals growing on stones and groins [56].