Baltic Europe, i.e. the sea and inland hinterland, form a unique macro-regional unit. Strong collaboration links as well as competition in the Baltic Sea Region are an inherent feature of the region from the beginnings of its civilization development. The article shows the forty-year-long Baltic integration process and the Polish scientific contribution to the process. Since 2004, the Baltic has become an internal EU sea. This fact no doubt strengthened cooperation of the countries around the Baltic Sea. In many spheres, these ties take the form of networking. An important stimulus for further integrations is the EU Strategy for the Baltic Sea Region. Political stabilisation and economic development may transform, in a longer time span, the emerging transnational Baltic Europe into a new economic and cultural European centre.

The Baltic is a unique brakish sea. Its moderate salinity is the result of the fresh river water input and non-periodic inflows of salty, oxygenated waters from the North Sea. However, the balance continually fluctuates. What impact does that have on the sea?

The article presents the issues related to ecological security of the Baltic Sea. The issue was taken from the perspective of Poland as one of the Baltic States, and also as a Member State of the European Union. The authors discussed the mechanisms and legal instruments which are crucial for the ecological security of the Baltic Sea (i.e. Helsinki Convention of 1974, or Agenda 21 for the Baltic Sea Region “Baltic 21”). The importance of cross-border cooperation has also been emphasized as an essential element of the security policy in the Baltic Sea area. The article also indicated threats to the protection of Baltic waters, among others, eutrophication.

How does inflowing river water affect the quality of water in the Baltic Sea? Why are the chemicals used in agriculture so dangerous for seas, and what future lies in store for the Baltic?

This article presents results of the analysis of 3 sediment cores taken from the bottom of Pomeranian Bay, southern Baltic Sea. These results are part of a larger project that aims to determine the characteristics and rate of the Atlantic marine ingression in the Pomeranian Bay area. The main geochemical elements and diatom assemblages from the cores were identified, revealing lacustrine sediments deposited during the time of Ancylus Lake and marine sediments deposited during the Littorina transgression. Distinct changes in the geochemical composition and diatom assemblages suggest that the Littorina transgression had a very large impact on the environment of Pomeranian Bay.

The article presents the results of a detailed study of the geological structure of the Łeba Barrier in the Rąbka cross-section (Southern Baltic, Poland). The barrier separates Lake Łebsko from the Baltic. Five sedimentary complexes were distinguished there (M2-M6). The spatial variability of the grain-size distribution was examined and succession stages of the mollusc fauna occurring in the individual sedimentary complexes were distinguished. Radiocarbon dating was used to establish the age of the most important events during the process of formation of the barrier, which took place in the course of several relative sea-level changes. The first sedimentary complex (M2) at Rąbka is connected with the second ingression (i2) of the Baltic Sea (ca. 6,700-6,000 14C years BP), sea-level stabilization (6,000-5,500 14C years BP), and at last sea-level lowering (5,500-5,000 14C years BP) in the region of the Gardno-Łeba Coastal Plain. The sedimentary complex M3 developed in a lagoonal environment when the barrier was situated north of its present position (5,000-3,000 14C BP). The next lowering of the sea-level made the lagoon shallower and caused the emergence of small but already subaerial stretches of barrier land with a freshwater fauna in the north (4,880š40 14C BP). With the next ingression stage (i3), which took place between 4,500 and 3,000 BP, the barrier shifted to its present-day position and the lagoon changed into a freshwater lake. From 3,000 to 1,700 14C BP fossil soil and peats developed on the barrier surface as a result of another sea-level lowering. The last ingression stages (i4 and i5), younger than 1,700 BP, built up the barrier, practically in its today's location (sedimentary complexes M4 and M5). The youngest sedimentary complex (M-6) is represented by present-day beach sands.

We present the last millennium of history of a peatland located in northern Poland. Our results are based on two replicate monoliths taken from a Baltic raised bog. We applied a high-resolution approach and radio car bon dating to the peat material to obtain a de tailed palaeoenvironmental reconstruction. To reconstruct past peatland moisture, we used three prox ies: testate amoebae, plant macrofossils and pollen. Despite different peat accumulation and extensive hiatus in the formerly studied core, both monoliths show a similar pattern of changes. However, the core from this study provides us with more detailed data on S. fuscum disappear ance which correlates well with the data from the other Baltic bog, S³owiñskie B³oto. Our re search shows that pris tine Bal tic bogs can be dated to AD 1350. Słowiñskie Błoto palaeohydrology confirms AD 1300 as the beginning of the hydrological disturbance. In the case of the Stążki and Słowiñskie Błoto bogs, the Little Ice Age (LIA) is recorded between AD 1500 and AD 1800. However, this climatic change might have been blurred by human impact. In the case of the Baltic bogs, their reference virgin state can be dated to AD 1200. After this date, we observed in creasing human impact and climatic in stability connected with the LIA. However, between AD 1800 and 1900, bogs were wet, most possibly due to climatic forcing. This fact suggests that despite human impact, recent peat deposits can still reflect climate. Our research provided in formation related to the time of existence, location and characteristics of the natural/pristine state. High-resolution peatland palaeoecology is crucial for restoration activities, e.g., rewetting and environmental management. The palaeohydrological context (supported by other proxies) of the last 1000 years provides a reliable answer to the question: ‘To rewet or not to rewet?’

The environment in general and the marine environment in particular forms an ecosystem. Such ecosystem is characterized by high interconnectivity and interdepen-dence of species inhabiting it. Often enough, marine ecosystems far exceed the limits of the State’s sovereignty. Thus, their effective protection and preservation shall be carried out on a cooperative basis, engaging all States sharing common environment. The first international treaty to tackle the issue of marine environmental protection on a systemic basis is the United Nations Convention on the Law of the Sea (UNCLOS). It is also a treaty which directly established an obligation to cooperate in ensuring this protection. However, homogenous international regulation is not capable of addressing regional varying circumstances of marine environment. As the example of the South China Sea shows, lack of cooperation between coastal States can result in an irreversible damage to the environment. On the other hand, a remarkable model of effective realization of the obligation to cooperate has been established in the region of the Baltic Sea. What we can learn from these experiences is that fulfillment of the obligation to cooperate on a re-gional basis is a prerequisite for effective protection and preservation of the marine environment.