The aim of this study is to determine natural and anthropogenic threats and their effects concerning the lakes situated within the coastal zone of the southern Baltic. The shore zone is a place of contact of the sea waters and the inland waters. This results in the formation of special water relationships and special circulation water. Macroscale conditions overlap local hydrological conditions and morphometric features of basins and hydrological features of catchments specific to particular lakes. All the natural conditions have been affected by human activity for over eight centuries. As a result. numerous natural and anthropogenic threats occur and cause not only periodic changes in the structure of lakes but such that even endanger their existence.

Surface phytoplankton samples were studied quantitatively and qualitatively in February 1996 - November 1998 and January 2003 - November 2005 at the shore and in the center of Admiralty Bay, King George Island. Phytoplankton assemblages showed spring-summer peaks (maxima 4.0-5.2×106 cells l-1) associated with small variations in low atmospheric pressure, and low velocity winds. They were dominated by nano-sized (<20 µm) flagellates and picoplankton (~2 µm). The prevalent nanoflagellates were either Prasinophyceae, Cryptophyceae, or Prymnesiophyceae. Diatoms were next in abundance. Of the seven spring-summer diatom blooms, five had initiated at the shore (maximum 9.8×105 cells l-1; November 1998). They were significantly greater than in the open water, and did not spread into the bay centre. Two observed open water blooms did not reach the shore. Diatoms formed up to 44% of the total cells in the period 1996-98; they only formed <5% in 2003-05. Shore and open water populations differed by diatom dominance structure. Pennates (Fragilariopsis spp., F. cylindrus, Pseudo-nitzschia spp.), and benthic species were prevalent at the shore; centrics (Thalassiosira spp., Chaetoceros socialis) were most common offshore. In 2003-05 diatoms were relatively impoverished in Chaetoceros spp. and the larger (>20 µm) Fragilariopsis spp. Nano-sized Thalassiosira spp. were the winter dominants. Diatom species dominance structure may change at each of the two sites within a month (e.g. shore site: F. cylindrus dominant in October ’98; T. gravida in November ’98). Dinoflagellates showed summer increases associated with diatom blooms. Variations in phytoplankton cell concentrations, the species structures between the shore and open waters, and between seasons appear to be related to physical factors: changes in wind velocity and direction, inflow of waters from the Bransfield Strait, ice melting and changes in atmospheric pressure.

Climate change and its consequences, including rising ocean temperature and sea level rise are well scientifically documented. The changes are especially severe for coastal communities, which are estimated to have reached c. 50% of the world’s population. Using an example of the Gulf of Gdansk region, which is of European importance, due to the presence of two major Baltic ports and global tourism, we explore, how sea related threats may affect the region and we analyse how the three major cities are prepared to these threats. The four city developmental strategies and an additional document, an “umbrella strategy” focusing on climate change threats do not consider sea level rise and more frequent storm surges as threats. The sea level rise is briefly discussed in the fourth document. The adaptation plan, an appendix to the document, mentions sea level rise, but the discussion of the problem is indirect and involves some examples of adaptation actions in loosely similar environmental conditions. The adaptation plan, in fact includes a list of possible threats, rather than a detailed discussion of the suggestions of the measures to be undertaken. For comparison, we present a multilevel approach, which is effectively run in the Port of Rotterdam and argue that such approach should be undertaken in the studied region. We conclude that despite years of education on climate change, the problem is still not recognised and is underrepresented in practical measures of the studied region. We also provide hints on how to overcome this situation.

Geospatial data obtained using Unmanned Aerial Vehicles (UAVs) and Unmanned Surface Vehicles (USVs) are increasingly used to model the terrain in the coastal zone, in particular in shallow waterbodies (with a depth of up to 1 m). In order to generate a terrain relief, it is important to choose a method for modelling that will allow it to be accurately projected. Therefore, the aim of this article is to present a method for accuracy assessment of topo-bathymetric surface models based on geospatial data recorded by UAV and USV vehicles. Bathymetric and photogrammetric measurements were carried out on the waterbody adjacent to the public beach in Gdynia (Poland) in 2022 using a DJI Phantom 4 RTK UAV and an AutoDron USV. The geospatial data integration process was performed in the Surfer software. As a result, Digital Terrain Models (DTMs) in the coastal zone were developed using the following terrain modelling methods: Inverse Distance to a Power (IDP), Inverse Distance Weighted (IDW), kriging, the Modified Shepard’s Method (MSM) and Natural Neighbour Interpolation (NNI). The conducted study does not clearly indicate any of the methods, as the selection of the method is also affected by the visualization of the generated model. However, having compared the accuracy measures of the charts and models obtained, it was concluded that for this type of data, the kriging (linear model) method was the best. Very good results were also obtained for the NNI method. The lowest value of the Root Mean Square Error (RMSE) (0.030 m) and the lowest value of the Mean Absolute Error (MAE) (0.011 m) were noted for the GRID model interpolated with the kriging (linear model) method. Moreover, the NNI and kriging (linear model) methods obtained the highest coefficient of determination value (0.999). The NNI method has the lowest value of the R68 measure (0.009 m), while the lowest value of the R95 measure (0.033 m) was noted for the kriging (linear model) method.