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Lake Ohrid is one of the few world’s oldest and longest-existing lakes, sustaining continuous freshwater habitats for over a million years and is the only one of its sort in Europe.
Lake Ohrid (altitude: 695 meters) is oligotrophic, deep (maximum depth 289 m; average
depth 164 m), big (area 358 km2), and has one of the greatest volumes (~55 km3) in Europe.
The water inflow comes mostly from the karst aquifers (50%), with tributaries and direct precipitation accounting for a minor part. Evaporation (40%) and the main outflow, the Crn Drim River (60%), balance the capacity of the lake.
The ecological significance of Lake Ohrid was acknowledged by its declaration as a UNESCO World Natural Heritage Site in 1980. Because of its distinctiveness, natural uniqueness and ecological potential, in 2014 the area of both Ohrid and Prespa lakes was designated a Transboundary Biosphere Reserve.
Climate
The Lake Ohrid region has a local continental climate with influences from the
Mediterranean climate of the Mediterranean and the Adriatic Sea. The mean average
temperature is 11,4°C, with a monthly mean maximum temperature of 21,2°C in July and
August and an absolute maximum of 34,4°C in August. The lowest monthly average
temperature was registered in January at 1,5°C, with an absolute minimum of -17,2°C.
The average annual temperature is ~11°C. The lake does not freeze and the surface water
temperature ranges between 6 and 26°C. The average annual rainfall around the Lake is
approximately 759 mm. According to the wind rose, the most prevalent is the north wind,
particularly in the fall and winter, while the south and south-west winds are dominant in the
spring and summer.
Средната годишна температура изнесува ~11°C. Езерото не замрзнува и температурата на површинската вода се задржува помеѓу 6 и 26°C. Просечните врнежи околу Езерото се приближно 759 mm годишно. Според ружата на ветрови, најчест е северниот ветер, особено во есен и зима, а во пролет и лето, ветровите од југ и југо-запад се доминантни.
Habitats
The Ohrid region and its surroundings are habitats for many plant and animal species.
Indeed, the area is renowned for its great variety of habitats, which stretch from 650 m m.s.l
at Lake Ohrid to the highest mountain peaks (Magaro 2254 m m.s.l) and include numerous
aquatic habitats, such as: freshwater springs, wetlands, reed belts, broad-leaved forests and
alpine pastures on limestone soil, rocks, cliffs and caves.
The most common habitats in Lake Ohrid include: oligo-mesotrophic, hard waters
overgrown with benthic vegetation of Chara spp.; natural eutrophic lakes dominated by
Magnopotamion and Hudrocharion communities; muddy-banked rivers covered in
vegetation species such as Chenopodion rubri and Bidention; calcareous wetlands (marshes)
with Cladium mariscus and species of Cariciondavallianae, and alkaline wetlands.
Fauna
The Lake Ohrid has extraordinarily rich and diverse faunal components, the majority of
which are marked by significant endemism. The lake is home to 21 native fish species and 7
imported species. Seven of the native fish species are endemic, including the well-known
Ohrid trout (Salmo letnica) (Fig. 2), the symbol of the city of Ohrid. Lake Ohrid’s fish faunaincludes the European eel (Anguilla anguilla), a critically endangered species (CE) according
to the IUCN Red list.
586 benthic macroinvertebrates are registered in Lake Ohrid, with endemism ranging from
50 to 90% for certain benthic groups (Turbellaria – flatworms, oligochaetes, leeches,
isopods, amphipods, etc.), making it the aquatic ecosystem with the highest endemism per
square meter in the world.
The rich and unique fauna of Lake Ohrid includes various types of relic forms such as: Ohrid
round sponge (Ohridaspongia rotunda) (Fig. 3), or the hardly visible endemic snail (Gocea
ohridana) (Fig. 4), which is only found in an area the size of a football field in the southeast
part of the lake. In general, the fauna of the group Gastropoda (freshwater snails) is the
richest, most diverse and has the highest endemism, accounting for 86% of the 72
registered species.
Almost all of the benthonic fauna registered in Lake Ohrid were assessed using IUCN criteria.
28 species were classified as vulnerable, 17 as endangered, and 10 as critically endangered,
indicating the urgent need to take action to protect and preserve this rich faunal
component.
Lake Ohrid is an important habitat for waterbird reproduction, migration and
wintering. During the winter, geese, swans and cormorants appear and the number of coots
(Fulica atra) on the lake can reach several tens of thousands.
Flora
Lake Ohrid represents a true treasure of biological diversity, even among microscopic algae,
which has drawn the attention of many researchers from European and neighbouring
countries. As with other living groups, Lake Ohrid stands out for its high concentration of
rare and tertiary relict algae species. Diatoms (Bacillariophyceae) appear to be a significant
group of microscopic algae, followed by green algae (Chlorophyceae). Lake Ohrid has a total
of 789 diatomic algae, with 117 species (14%) being endemic to the lake and 15 (about 2%)
being relict species or previously known exclusively from fossil deposits in Romania.
The number of species registered in Lake Ohrid is steadily rising. The majority of the species
in the Lake could be ecologically categorized as oligotraphentic – species that live only in
very clean waters with few nutrients, especially nitrogen and phosphorus.
The macrophyte vegetation on the shores of Lake Ohrid can be divided into various belts, including types of Chara at depths between 3 and 30 meters, types of aquatic macrophytes in shallow waters and an interrupted belt of reeds (Phragmites australis) along the shores. Reed belts serve as crucial habitat for a wide variety of other organisms, such as juvenile fish, frogs and water birds. In many places colonial algae Cladophora grows on most surfaces.
Human interactions
The shores of Lake Ohrid have been inhabited since prehistoric times, with archeologic
studies revealing settlements dating back to before 6000 B.C. The city of Ohrid is one of
Europe’s oldest human settlements. The Prespa region has been inhabited since the Bronzeand Early Stone Ages. The Illyrians lived in Ohrid and Prespa until the 5th century B.C. when
they were conquered by Rome. During the Roman Empire, the Via Egnatia route passed
through this area, resulting in the development of numerous settlements nearby. In the
medieval period, the city of Ohrid was a cultural center with a flourishing university, the
oldest in Europe, where 3500 students were educated on the Ohrid hill in the IX and X
centuries.
The attractive landscape and recreation opportunities that Lake Ohrid offers,
surrounded by mountains and hills, numerous beaches with clear water, a variety of ancient
items from cultural and other archaeological structures, and many monuments of nature,
have made Lake Ohrid one of the most sought-after tourist destinations. As a result, the
population has grown by five times in the last 50 years, reaching 200.000 people. The
primary sources of income for the population have always been fishing, agriculture and
animal husbandry. Furthermore, the sector for small businesses and seasonal services is
seeing noticeable development, bearing in mind that the main industrial facilities that once
existed are no longer operational.
The whole region is also very attractive for a variety of sports activities: mountain climbing,
hiking, alpinism, sailing, diving and paragliding, educational and recreational activities, bird
watching and speleological explorations.
The convergence of distinctive natural values with the quality and diversity of its cultural,
material and spiritual heritage, makes this region truly unique.
The convergence of the characteristic natural values with the quality and diversity of its cultural, material and spiritual heritage, makes this region truly unique.
