Käina Bay () is almost isolated and very shallow approximately marine area between the Estonian islands

Hiiumaa Hiiumaa ( , ) is the second largest island in Estonia and is part of the West Estonian archipelago, in the Baltic Sea. It has an area of 989 km2 and is 22 km from the Estonian mainland. Its largest town is Kärdla. It is located within ...

and Kassari, which is connected to the surrounding

Väinameri The Väinameri (Estonian language, Estonian for ''Strait Sea'' or ''Sea of Straits''; ) or Väinameri Sea is a strait and sub-bay of the Baltic Sea, located between the West Estonian Archipelago and the Estonian mainland, within western Estonia. ...

and adjacent Vaemla Bay via three tiny channels - Orjaku channel, Orjaku sill and

Vaemla Vaemla () is a village in Hiiumaa Parish, Hiiu County in northwestern Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by ...

(Laisna, Õunaku) channel. The maximum depth of Käina Bay is about 1 meter. Käina Bay is separated from the Väinameri Sea by Kassari Island, Õunaku Bay and Jausa Bay by a dyke road. There are many thickets of reeds and islets (23). In the southern part of the bay there is mineral curative mud.

Water regime

Average high

water level Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified vertical datum. Over long distances, neglecting external forcings (such as wind), water level ten ...

in Käina Bay lasts from November until March and critically low water level period is from April until June. Most extreme changes in the

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

; onto which water level in the bay reacts with certain time lag, occur in the open sea from September until March, when stronger winds prevail. Sea level variability in the Käina Bay is smaller comparing to

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...

. Two types of water exchange regime occur in the Käina Bay, which depend on the water level in the open sea. In the case of higher sea level water in the Vaemla Bay rises faster due to transport through Õunaku sill comparing to Käina Bay and as a consequence, open sea water arrives to the Käina bay also through Vaemla channel. In the case of lower sea level water exchange through Õunaku sill does not occur and therefor saltier water inflow (outflow) to (from) the Vaemla Bay occurs through Käina Bay. File:Käina Bay 8.jpg, Orjaku channel from the Käina Bay File:Käina Bay 7.jpg, Orjaku channel to the Käina Bay File:Käina Bay 6.jpg, alt=Orjaku channel entrance to the Jausa Bay, Orjaku channel entrance to the Väinameri File:Käina Bay 5.jpg, Orjaku channel culvert under the road

Protected nature area

Landscape Reserve

Käina Bay-Kassari Landscape Conservation Area (KLO1000508) is one of 152

protected areas of Estonia Protected areas of Estonia are regulated by the Nature Conservation Act (), which was passed by the Riigikogu, Estonian parliament on April 21, 2004 and entered into force May 10, 2004. Overall Estonia has 15403 protected areas covering 21% of the ...

. Total area of the reserve is , including areas permanently covered by water . The history of this protected area dates back to 1939, when the Kassari and Vaemla Bay curative mud areas were protected. In 1962, two protected areas were established: the Kassari Island

Landscape A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or human-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes th ...

Protection Area and the Käina Bay

Ornithological Ornithology, from Ancient Greek ὄρνις (''órnis''), meaning "bird", and -logy from λόγος (''lógos''), meaning "study", is a branch of zoology dedicated to the study of birds. Several aspects of ornithology differ from related discip ...

Protection Area, which were merged to form the Käina Bay-Kassari Landscape Protection Area in 1998. This area is maintained and improved with the support of various public funds, including support from the European Union Cohesion Fund and Environmental Investment Centre environmental programme. Vaemla region at the Käina Bay-Kassari Landscape Reserve on the south-eastern edge received the necessary tools for coastal meadow maintenance. The channels would ensure normal water exchange in the bay and at the same time create a favorable condition for the local habitats and species. Based on the 2017 study of the Taltech Department of Marine Systems about the condition of Käina Bay and Vaemla Bay, and the efficiency of water regulators and recommendations therein, the works in the watercourses were implemented in May 2020. During the works, reeds and sediment were removed from Puulaiu, Orjaku sill and Laisna channel. The works commissioned by the Environmental Board were financed from the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

Cohesion Fund The Cohesion Fund, one of the five European Structural and Investment Funds of the European Union, provides support to Member States with a gross national income per capita below 90% EU-27 average to strengthen the economic, social and territorial ...

within the framework of investments in the project “Preservation and Restoration of

Protected Species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, invasiv ...

and Habitats”.

Ramsar Site

Hiiumaa islets and Käina Bay Hiiumaa ( , ) is the second largest island in Estonia and is part of the West Estonian archipelago, in the Baltic Sea. It has an area of 989 km2 and is 22 km from the Estonian mainland. Its largest town is Kärdla. It is located within ...

site has been listed the list of Ramsar sites in Estonia as one of 17 Estonian wetlands of international importance. The Hiiumaa Islets and Käina Bay site () is a complex of coastline and small islands on the southeast coast of Hiiumaa Island, which in turn lies off the west coast of the Estonian mainland. The area is hydrologically highly prized for the prevention of coastal erosion, sediment trapping, maintenance of water quality, and support of

food chain A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...

s. Here, too, rich communities of endangered orchids can be found. The mix of state and private lands supports about 100 inhabitants but is an important area for

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment (Freshwater ecosystem, freshwater or Marine ecosystem, marine), but may also be caught from Fish stocking, stocked Body of water, ...

and

ecotourism Ecotourism is a form of nature-oriented tourism intended to contribute to the Ecological conservation, conservation of the natural environment, generally defined as being minimally impactful, and including providing both contributions to conserv ...

, as well as for environmental education, scientific research, and curative sea mud (

peloid Peloid is defined as a mature clay, mud or mud Suspension (chemistry), suspension or Dispersion (chemistry), dispersion with curative or cosmetic properties, consisting of a complex mixture of fine-grained materials of geological and/or biologic ...

Biosphere reserve

West Estonian Archipelago The West Estonian archipelago (, also Moonsund archipelago) is a group of Estonian islands located in the Baltic Sea around Väinameri. The total area is about . The archipelago is composed of the islands Saaremaa, Hiiumaa, Muhu, Vormsi and ab ...

, including Käina Bay, was from 1990 listed as

UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

Biosphere Reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geologic ...

which are wholly or partially

World Heritage sites World Heritage Sites are landmarks and areas with legal protection under an international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural heritag ...

Mineral resource deposit

According to the Earth's Crust Act and Environmental Register national mineral resource Käina sea mud deposit is located in the western part of Käina Bay, where near Orjaku village organic mineral mud is being excavated and used by the cosmetics industry, for curative purposes and SPA industry. Estonian mineral mud has been studied extensively in the past. The latest research was conducted in 2013-2014 by Centre of Excellence in Health Promotion and Rehabilitation (). The results confirm that Käina Bay contains the most mineral sediments and the lowest concentrations of heavy metals out of all analyzed mud deposits in Estonia. On the lithological composition on average Käina Bay

contains 91.4% of minerals, 6.5% of organic matter, and 3.7% of carbonates. The sediments in Käina Bay are ecologically cleanest in Estonia.

References

{{reflist Ramsar sites in Estonia Bays of Estonia Biosphere reserves of Estonia Hiiu County