View source for Lake Ohrid

{{short description|International lake in North Macedonia and Albania}}
{{Infobox body of water
| name               = Lake Ohrid
| image              = Lake Ohrid, Macedonia-Albania viewed from a NASA satellite.jpg
| caption            = Lake Ohrid viewed from a NASA satellite
| image_bathymetry   = Ohrid Basin map.png
| caption_bathymetry = Map of the Ohrid Basin showing major hydrological and geological features
| location           = [[North Macedonia]]–[[Albania]] border
| coords             = {{WikidataCoord|display=it}}
| lake_type          = [[ancient lake]], [[Lake#Tectonic lakes|tectonic lake]]
| inflow             = [[Sateska]] River, Biljana's springs, underground link with [[Lake Prespa]]
| outflow            = [[Black Drin]] River
| catchment          = {{convert|2,600|km2|abbr=on}}
| basin_countries    = North Macedonia, Albania
| length             = {{convert|36.4|km|mi|abbr=on}}
| width              = {{convert|16.8|km|abbr=on}}
| area               = {{convert|358|km2|abbr=on}}
| depth              = {{convert|155|m|ft|abbr=on}}
| max-depth          = {{convert|288|m|ft|abbr=on}}
| volume             = {{convert|55.49|km3|abbr=on}}
| residence_time     = 70 years
| shore              = {{convert|87.53|km|mi|abbr=on}}<br />North Macedonia: {{convert|56.02|km|mi|abbr=on}};<br />Albania: {{convert|31.51|km|mi|abbr=on}}
| elevation          = {{convert|693|m|ft|abbr=on}}
| frozen             = 
| islands            = none
| cities             = [[Ohrid]], [[Struga]] (North Macedonia) <br /> [[Pogradec]] (Albania)
<!--      Map      -->| pushpin_map        = North Macedonia#Albania#Balkans#Europe
| pushpin_label_position = 
| pushpin_map_alt    = Location of the lake in Europe
| pushpin_map_caption = <!--   Below       -->
| website            = 
| reference          = 
| extra              = {{designation list | embed=yes
| designation1 = WHS
| designation1_offname = Natural and Cultural Heritage of the Ohrid region
| designation1_type = Natural, Cultural
| designation1_criteria = i, iii, iv, vii
| designation1_number = [https://whc.unesco.org/en/list/99 99]
| designation1_free1name = Region
| designation1_free1value = [[List of World Heritage Sites in Europe|Europe and North America]]
| designation1_date = 1979 {{small|(3rd [[World Heritage Committee|session]])}}
| designation1_free3name = Extensions
| designation1_free3value = 1980, 2019
| designation2 = Ramsar
| designation2_date = 15 February 2021
| designation2_number = 2449<ref name="RSIS">{{Cite web|title=Lake Ohrid|website=[[Ramsar Convention|Ramsar]] Sites Information Service|url=https://rsis.ramsar.org/ris/2449|access-date=13 May 2021}}</ref>}}
}}
'''Lake Ohrid'''{{efn|{{langx|mk|Охридско Езеро|Ohridsko Ezero}}; {{IPA|mk|ˈɔxritskɔ ˈɛzɛrɔ}}; {{langx|sq|Liqeni i Ohrit}}; {{IPA|sq|liˈcɛni i ˈɔhrit}}}} is a [[lake]] which straddles the mountainous border between the southwestern part of [[North Macedonia]] and eastern [[Albania]]. It is one of [[Europe]]'s deepest and oldest lakes, with a unique aquatic [[ecosystem]] of worldwide importance, with more than 200 endemic species.<ref>{{cite web
  |url=http://www.investinmacedonia.com/page.aspx?language=&page=O25QDpgVFLj9Bfg/vkoGyw==|title=Lake Ohrid; Invest in Macedonia – Agency for Foreign Investments of the Republic of Macedonia|website=InvestInMacedonia.com|access-date=3 June 2017|url-status=dead|archive-url=https://archive.today/20080914032610/http://www.investinmacedonia.com/page.aspx?language=&page=O25QDpgVFLj9Bfg/vkoGyw==|archive-date=14 September 2008
}}</ref>

North Macedonia's side of Lake Ohrid was declared a [[World Heritage Site]] by [[UNESCO]] in 1979, with the site being extended to also include the cultural and historic area of [[Ohrid]] in 1980. In 2010, [[NASA]] named one of [[Lakes of Titan|Titan's lakes]] after it.<ref>{{cite web
  |url=http://www.mia.com.mk/default.aspx?vId=77930245&lId=2&pmId=501|title=One of Titan lakes to be named Ohrid Lacus|website=MIA.com.mk|access-date=3 June 2017
}}</ref> In 2014, the [[Ohrid-Prespa Transboundary Reserve]] between Albania and North Macedonia was added to UNESCO's World Network of Biosphere Reserves.<ref>{{cite web
  |url=http://www.unesco.org/new/en/media-services/single-view/news/thirteen_sites_added_to_unescos_world_network_of_biosphere_reserves/#.U5pSD3KzHz4|title=Single View News - United Nations Educational, Scientific and Cultural Organization|website=www.UNESCO.org|access-date=3 June 2017
}}</ref> Albania's side of Lake Ohrid was also designated UNESCO world heritage status in 2019. North Macedonia's portion was designated as a protected [[Ramsar site]] in 2021, passing all nine criteria for proclamation.<ref name=":9">Ministry of Environment and Physical Planning (2021) "[https://rsis.ramsar.org/RISapp/files/RISrep/MK2449RIS_2105_en.pdf Ramsar Information Sheet: Lake Ohrid]".  Ramsar Secretariat, Gland, Switzerland.</ref>

In Albania, the coastal portion of the lake holds [[Protected areas of Albania|Managed Nature Reserve]] status. In North Macedonia, a portion of the lakeside is part of the [[Galičica]] National Park.

The towns situated at the lakeside are [[Ohrid]] and [[Struga]] in North Macedonia along with [[Pogradec]] in Albania. The lake is otherwise [[List of settlements on the Lake Ohrid shoreline|surrounded by settlements]] in the form of villages and resorts in both basin countries.

==Geography==
[[File:Ohrid and Prespa lakes topographic map.svg|250px|left|thumb|upright|Topographic map with Lake Ohrid on the left]]
Lake Ohrid is one of the oldest lakes in the world, and with a maximum depth of {{convert|288|m|ft}} and mean depth of {{convert|155|m|ft|abbr=on}}, it is the deepest lake in the [[Balkans]]. It covers an area of {{convert|358|km2|sqmi}} and contains an estimated 55.49 cubic kilometres ({{#expr: {{convert|55.49|km3|acre ft|comma=off|disp=number|-6}} / 1000000}} million [[Acre-foot|acre-feet]]) of water. The lake is {{convert|30.4|km|mi|abbr=on}} long and {{convert|14.8|km|mi|abbr=on}} wide at its maximum extent, with a shoreline of {{convert|87.53|km|mi|abbr=on}}.

64% of Lake Ohrid's shoreline and 69% of its surface area are within [[North Macedonia]], whereas 36% of the shoreline and 31% of the surface area fall within [[Albania]].

==Origin==
[[File:Museum on Water, Ohrid.JPG|thumbnail|left|upright=1.8|Reconstruction of [[Bronze Age]] stilt houses on Lake Ohrid, near [[Peštani]], [[North Macedonia]]]]

The Ohrid and [[Prespa Lake]]s are the two largest in a north–south chain of tectonic basins ([[graben]]s) including the [[Korçë Plain|Korçë basin]], and [[Lake Ioannina]] in northwestern Greece, known as the Dessaret group. The transition from [[Compressional tectonics|compressional]] to [[extensional tectonics]] in the central Balkan Mts occurred around 6 million years ago, with the oldest lake sediments being [[Pliocene]], possibly 3-5 million years old.<ref>Hoffmann et al. 2010 Evolution of ancient Lake Ohrid: a tectonic perspective. Biogeosciences, 7, 3377–3386, www.biogeosciences.net/7/3377/2010/doi:10.5194/bg-7-3377-2010/</ref><ref name=":5"/><ref name="Korovchinsky, Petkovski" /> The ''Dessaret chain'' is a poorly developed [[rift valley]]. Worldwide, rift valley lakes with similarly ancient origins include [[Lake Baikal]], [[Lake Titicaca]], [[Lake Tanganyika]] and the [[Dead Sea]]. Most lakes have much shorter life spans as they rapidly fill with sediments. Lake Ohrid is being  infilled at its north end by its modest main tributaries, but is preserved by its great depth, by continuing [[tectonic subsidence]], and by the main inflows being from underground karstic channels from Lake Prespa carrying minimal sediment. The graben system is still tectonically active and Lake Ohrid sits in a seismogenic landscape, with many visible traces including fresh fault scarps, displaced sediment and soil sequences, stepped hillsides, and a hydrothermal field near [[Kosel, North Macedonia|Kosel]]. Moderate earthquakes are frequent, with the strongest yet measured here on 18 February 1911, with a magnitude 6.6 at a focal depth of 15&nbsp;km, destroying houses but with no loss of life.<ref>Hoffman et al. 2010</ref>

==Hydrology==
The lake drains an area of around 2,600&nbsp;km² and is fed primarily by underground springs on the eastern shore (about 50% of total inflow), with roughly 25% shares from rivers and direct precipitation. Over 20% of the lake's water comes from nearby [[Lake Prespa]], about {{convert|10|km|mi|abbr=on}} to the southeast and at 150 m higher altitude than Lake Ohrid. The water leaves Lake Prespa trickling through underground watercourses in the [[karst]]ic landscape, where it is joined by mountain range precipitation and eventually emerges in numerous springs along the eastern shore and below the water surface of Lake Ohrid. The water leaves Lake Ohrid by [[evaporation]] (~40%) and through its only outlet, the [[Black Drin|Black Drin River]], which flows in a northerly direction into [[Albania]] and thus to the [[Adriatic Sea]]. The relatively dry, Mediterranean climate and the small drainage basin of 2,600&nbsp;km² (catchment/lake surface ratio of ~7) of Lake Ohrid results in a long [[Lake retention time|hydraulic residence time]] scale of ~70 yr.<ref name="spirkovski" >Z. Spirkovski, Z. Krstanovski, L. Selfo, M. Sanxhaku, V.I. Puka, "The Monitoring Programme of the Lake Ohrid Conservation Project", in ''Transboundary Water Resources in the Balkans: Initiating a Sustainable Co-Operative Network'', ed. Jacques Ganoulis, I L Murphy, Mitja Brilly (Springer, 2000)</ref><ref name="physics" >A. Matzinger, Z. Spirkovski, S. Patceva, A. Wüest, "Sensitivity of ancient Lake Ohrid to local anthropogenic impacts and global warming" (Journal of Great Lakes
Research 2006, 32: 158–179)</ref><ref name="prespa" >A. Matzinger, M. Jordanoski, E. Veljanoska-Sarafiloska, M. Sturm, B. Müller, A. Wüest, "Is Lake Prespa jeopardizing the ecosystem of ancient Lake Ohrid?" (Hydrobiologia 2006, 553: 89–109)</ref>

==Physical and geochemical properties==
The water at the surface of Lake Ohrid moves predominantly in a counter-clockwise direction along the shore, as a result of wind forcing and the Earth rotation, similar to the [[Ekman layer|Ekman]]-phenomenon known from oceans. In terms of vertical water exchange, [[convection|convective]] mixing during winter cooling is the dominant process. However, in an average winter only the top 150–200 meters of the lake are mixed, whereas the water below is stably [[Lake stratification|stratified]] by salinity. The stability due to this salinity gradient allows complete convective mixing events only roughly once every 7 years.<ref name="physics" /><ref name="Hadzisce">S. D. Hadzisce, "The mixo-phenomenon of Lake Ohrid in the course of the years 1941/42-1964/65 (in German)" (Proceedings of the International Association of Theoretical and Applied Limnology 1966, 16: 134–138)</ref>

Both in terms of [[nutrient]] concentration (4.5 μg L<sup>−1</sup> of phosphorus), as well as biological parameters Lake Ohrid qualifies as [[oligotroph]]ic. Thanks to this oligotrophy and the filtered spring inflows, the water is exceptionally clear with transparencies to a depth of as much as 22 meters (66&nbsp;feet). Lake Ohrid lacks an annual deep water exchange which in other lakes can bring complete overturn; plunging rivers are also absent. Despite this, dissolved oxygen never drops below ~6&nbsp;mg L<sup>−1</sup>.<ref name="model">A. Matzinger, M. Schmid, E. Veljanoska-Sarafiloska, S. Patceva, D. Guseska, B. Wagner, B. Müller, M. Sturm, A. Wüest, {{cite journal |title=Eutrophication of ancient Lake Ohrid: Global warming amplifies detrimental effects of increased nutrient inputs |journal=Limnology and Oceanography |date=2007 |volume=52 |pages=338–353 |url=http://www.aslo.org/lo/toc/vol_52/issue_1/0338.pdf |url-status=dead |archive-url=https://web.archive.org/web/20070713172930/http://aslo.org/lo/toc/vol_52/issue_1/0338.pdf |archive-date=2007-07-13 |doi=10.4319/lo.2007.52.1.0338 |last1=Matzinger |first1=Andreas |last2=Schmid |first2=Martin |last3=Veljanoska-Sarafiloska |first3=Elizabeta |last4=Patceva |first4=Suzana |last5=Guseska |first5=Dafina |last6=Wagner |first6=Bernd |last7=Müller |first7=Beat |last8=Sturm |first8=Michael |last9=Wüest |first9=Alfred |issue=1 |bibcode=2007LimOc..52..338M |s2cid=83496931 }}</ref><ref name="soer">M. Watzin, V. Puka, T. B. Naumoski (eds), "Lake Ohrid and its watershed, state of the environment report" (Lake Ohrid Conservation Project. Tirana, Albania and Ohrid, Macedonia)</ref>

== Wetland habitats ==
Previously extensive wetland habitats in the vicinity of Lake Ohrid have been lost due to conversion into agricultural or urban land. These include Struga Marsh, large portions of which were drained for agriculture in the 1940s<ref name=":0">{{Cite journal|last=Apostolova |first=N. |display-authors=etal |date=2016|title=Studenchishte Marsh as an Integral Part of Ancient Lake Ohrid: Current Status and Need for Protection|url=https://issuu.com/societyofwetlandscientists/docs/june_2016_wsp|journal=Wetland Science & Practice|volume=33| issue =  2|pages=35–45}}</ref> and again in the 1960s when the [[River Sateska]] was rerouted.<ref name=":1">Deutsche Gesellschaft für Internationale Zusammenarbeit (2015) [https://www.giz.de/en/downloads/giz2016-en-initial-characterization-prespa-ohrid-shkodra-skadar.pdf Initial Characterisation of Lakes Prespa, Ohrid and Shodra/Skadar. Implementing the EU Water Framework Directive in South-Eastern Europe] {{Webarchive|url=https://web.archive.org/web/20180325232911/https://www.giz.de/en/downloads/giz2016-en-initial-characterization-prespa-ohrid-shkodra-skadar.pdf|date=2018-03-25}}.</ref>

Nowadays, the last remaining significant coastline wetland at Lake Ohrid is [[Studenchishte Marsh]],<ref name=":0" /> which is located on the eastern shore near the city of Ohrid. Despite degradation from a variety of sources such as large-scale disposal of [[construction waste]], major land conversion, disruption of water connections to Lake Ohrid, beach urbanization and loss of reed belts,<ref name=":0" /> Studenchishte Marsh is  still an important buffer to prevent lake eutrophication<ref>{{Cite news|url=http://fokus.mk/lake-ohrid-a-paradise-in-peril/|title=Lake Ohrid: A Paradise in Peril|last=Dr. Thomas Wilke and Dr. Christian Albrecht|date=31 August 2015|work=Fokus|access-date=25 March 2018|archive-url=https://web.archive.org/web/20151017233819/http://fokus.mk/lake%2Dohrid%2Da%2Dparadise%2Din%2Dperil/|archive-date=2015-10-17|url-status=dead}}</ref> and a key habitat for biodiversity, including relict plants and endemic species.<ref name=":0" /> These values, and the comparative rareness of similar habitats in Macedonia (now North Macedonia), prompted an expert team in 2012 to recommend designation of a 63.97-hectare area at Studenchishte Marsh to be protected as a [[Natural monument|Natural Monument]] under Macedonian law.<ref>Spirovska, M., et al. (2012) [http://www.ohrid.gov.mk/Ekologija/Proekti/Ekologija%20arhiva/Menka- Blato-13_02_2012%20%20lektorirano-final.pdf Integrated Study on the State of the Remains of Studenchishte Marsh and Measures for its Revitalization]{{Dead link|date=February 2020 |bot=InternetArchiveBot |fix-attempted=yes }}, Dekons-Ema Drustvo za ekoloshki consulting. (Macedonian language)</ref>

Changes to the General Urban Plan for Ohrid 2014–2020, however, made provisions for Studenchishte Marsh to be drained and replaced with infrastructure for tourism and water-sports,<ref name=":0" /><ref>{{Cite news|url=https://www.newscientist.com/article/dn28693-europes-oldest-lake-faces-destruction-to-make-way-for-tourists/|title=Europe's oldest lake faces destruction to make way for tourists|last=Pearce|first=Fred|date=18 December 2015|work=New Scientist|access-date=25 March 2018}}</ref> a proposal which, together with other regional developments, was opposed by numerous local and international experts,<ref>{{Cite web|url=https://ohridsos.org/declaration-on-preserving-the-world-natural-and-cultural-heritage-of-ohrid/|title=Declaration on Preserving the World Natural and Cultural Heritage of the Ohrid Region|website=ohridsos.org|date=15 April 2015|access-date=25 March 2018}}</ref> including the [[Society of Wetland Scientists]].<ref>Society of Wetland Scientists (2015) [http://sws.org/images/News/LakeOhrid2015.pdf Letter to Mr Nikola Bakračeski, Mayor of the City of Ohrid] {{Webarchive|url=https://web.archive.org/web/20170404093909/http://sws.org/images/News/LakeOhrid2015.pdf |date=2017-04-04 }}.</ref> A [[Strategic environmental assessment|Strategic Environmental Assessment]] also concluded that no measure except non-implementation could reduce the direct negative impact on Studenchishte and the indirect negative impact on Lake Ohrid if the proposed construction was to take place at the wetland.<ref>Dr. Borka Kovachevic (2015) [https://www.scribd.com/doc/258516081/DRAFT-REPORT-ON-STRATEGIC-ENVIRONMENTAL-ASSESSMENT-AMENDMENTS-TO-THE-GENERAL-URBAN-PLAN-FOR-OHRID Draft Report on the Strategic Environmental Assessment for Changes and Additions to the General Urban Plan for Ohrid].</ref> Plans to drain the area have subsequently been reversed and the Macedonian government announced in 2018 that it would move forward with proclamation of Studenchishte Marsh as a protected area and its designation together with Lake Ohrid as a [[Ramsar site|Wetland of International Importance]] under the Ramsar Convention.<ref>{{Cite web|url=http://vlada.mk/node/14294|title=From the 60th Session of the Government of the Republic of Macedonia|date=20 March 2018|website=Government of the Republic of Macedonia|access-date=25 March 2018|archive-date=26 November 2023|archive-url=https://web.archive.org/web/20231126104009/https://vlada.mk/node/14294|url-status=dead}}</ref> Ramsar status was formalized in 2021<ref name="RSIS"/> although protection of Studenchishte Marsh at the national level has not yet been completed.  

The [[IUCN]] identifies wetland rehabilitation as one of five potential site needs for the [[UNESCO]] Natural and Cultural Heritage of the Ohrid Region.<ref name=":2">International Union for the Conservation of Nature (IUCN) (2017) [https://www.worldheritageoutlook.iucn.org/node/968 Natural and Cultural Heritage of the Ohrid region 2017 Conservation Outlook Assessment] {{Webarchive|url=https://web.archive.org/web/20220120220402/https://worldheritageoutlook.iucn.org/node/968 |date=2022-01-20 }}, Gland, Switzerland.</ref>  However, the potential to restore Struga Marsh, which was not included in the boundaries of the Ramsar Site, is likely to be reduced by construction of the European Corridor VIII railway, while Studenchishte's future is yet to be fully resolved.<ref name=":3">World Heritage Centre, ICOMOS and IUCN (2017) [https://whc.unesco.org/en/documents/158740 Reactive Monitoring Mission Report Natural and Cultural Heritage of the Ohrid Region (Former Yugoslav Republic of Macedonia)], World Heritage Centre, Paris, France.</ref> 

==Fauna==
[[File:Ohridospongia rotunda.jpg|thumb|Ohrid sponge (''[[Ochridaspongia rotunda]]'') is endemic to Lake Ohrid]]

Measured by its surface area of 358&nbsp;km², Ohrid is probably among the most biodiverse lakes on Earth.<ref name=":5">Albrecht, Christian and Wilke, Thomas: ''Ancient Lake Ohrid: biodiversity and evolution; in Patterns and Processes of Speciation in Ancient Lakes'', Developments in Hydrobiology, Springer Netherlands, 2009, pp 103 to 140. {{ISBN|978-1-4020-9582-5}}  {{doi|10.1007/978-1-4020-9582-5_9}}</ref> While it is special as such, by far the most spectacular quality is its impressive [[endemism]]. Similar to [[Lake Baikal]] or [[Lake Tanganyika]], Lake Ohrid harbors endemic species covering the whole food-chain, from [[phytoplankton]] and sessile algae (20 species; e.g., ''[[Cyclotella fottii]]''), over plant species (2 species; e.g., ''[[Chara ohridana]]''), [[zooplankton]] (5 species; e.g., ''[[Cyclops ochridanus]]''), [[cyprinid]] fish (8 species; e.g., ''[[Pachychilon pictum]]''), to predatory fish (two trout species; the [[Ohrid trout]] complex ''Salmo letnica'', and "Belvica" ''[[Salmo ohridanus]]'') and finally its diverse endemic bottom fauna (176 species; e.g. ''[[Ochridagammarus solidus]]''), with particularly large endemism among [[crustacean]]s, [[mollusc]]s, sponges and [[planarian]]s. There were recorded 68 species of [[freshwater snail]]s from the Lake Ohrid basin.<ref name="Hauffe 2011">{{cite journal | last1 = Hauffe | first1 = T. | last2 = Albrecht | first2 = C. | last3 = Schreiber | first3 = K. | last4 = Birkhofer | first4 = K. | last5 = Trajanovski | first5 = S. | last6 = Wilke | first6 = T. | year = 2011 | title = Spatially explicit analysis of gastropod biodiversity in ancient Lake Ohrid | journal = Biogeosciences | volume = 8 | issue = 1 | pages = 175–188 | doi = 10.5194/bg-8-175-2011 | bibcode = 2011BGeo....8..175H | doi-access = free }}</ref> 73.5% (50 species) of the total freshwater gastropod fauna appear to be endemic to the Lake Ohrid basin.<ref name="Hauffe 2011"/> Whereas the endemic species list cited above is based on morphological and ecological characteristics, some recent applications of molecular genetic techniques underline the difference of the fauna from common European taxa, as well as the old age of the lake.<ref name="stankovic">S. Stankovic, "The Balkan Lake Ohrid and its living world", Monographiae Biologicae, Vol. IX (Uitgeverij Dr. W. Junk, Den Haag, Netherlands, 1960)</ref><ref name="salemaa">H. Salemaa, "Lake Ohrid", in ''Speciation in Ancient Lakes'', eds. K. Martens, B. Goddeeris, G. Coulter (Archiv für Hydrobiologie – Advances in Limnology 1994, 44: 55–64)</ref><ref name="sell">{{cite journal | last1 = Sell | first1 = J. | last2 = Spirkovski | first2 = Z. | year = 2004 | title = Mitochondrial DNA differentiation between two forms of trout Salmo letnica, endemic to the Balkan Lake Ohrid, reflects their reproductive isolation | journal = Molecular Ecology | volume = 13 | issue = 12| pages = 3633–3644 | doi=10.1111/j.1365-294x.2004.02362.x | pmid=15548279| s2cid = 24961975 }}</ref>

Quite remarkably, [[exotic species]] do not seem to be a major issue in Lake Ohrid, although they have been recorded in small populations for several decades or exist in nearby rivers or lakes. The reason lies very probably in the ideal adaptation of the endemic species to the specific conditions in the lake, such as low nutrient availability, good living conditions in greater depth thanks to high water transparency and oxygen content, as well as subaquatic spring inflows supplying cool and [[oxygen]]-rich water.<ref name="stankovic" /> In total, seven introduced fish species are known from the lake.<ref name=Talevski>{{cite journal | last1 = Talevski | first1 = Milosevic | last2 = Maric | first2 = Petrovic | last3 = Talevska | last4 = Talevska | year = 2009 | title = Biodiversity of Ichtyofauna from Lake Prespa, Lake Ohrid and Lake Skadar | url = http://www.diagnosisp.com/dp/journals/view_pdf.php?journal_id=1&archive=0&issue_id=22&article_id=680 | journal = Biotechnology & Biotechnological Equipment | volume = 23 | issue = 2 | pages = 400–404 | doi = 10.1080/13102818.2009.10818449 | s2cid = 84541133 }}{{dead link|date=December 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Despite the exceptionally high level of endemism in Lake Ohrid (for example, a third of the 21 native fish species and almost 80% of its 72 mollusc species are endemic), a significant number of non-endemic species are found in Lake Ohrid. This includes species, which are mobile (e.g., via water birds) or migratory, such as the [[European eel]].<ref name=Talevski/><ref>M.R. Frogley, R.C. Preece, "A faunistic review of the modern and fossil molluscan fauna from Lake Pamvotis, Ioannina, an ancient lake in NW Greece; implications for endemism in the Balkans", in ''Balkan Biodiversity: Pattern and Process in the European Hotspot'', eds. Huw I. Griffiths, Jane M. Reed, Boris Kryštufek (Springer, 2004)</ref><ref>Segers, H.; and Martens, K; editors (2005). ''The Diversity of Aquatic Ecosystems.'' p. 46. Developments in Hydrobiology. Aquatic Biodiversity. {{ISBN|1-4020-3745-7}}</ref>

===Birds===
The lakeshore reed beds and wetlands provide critical habitat for hundreds of thousands of wintering water birds, including rare and threatened species such as the [[Dalmatian pelican]], [[ferruginous duck]], [[swan]], [[spotted eagle]], and [[eastern imperial eagle]]. The Macedonian part of the lake has been designated an [[Important Bird Area]] (IBA) by [[BirdLife International]] because it supports populations of [[common coot]]s and [[pygmy cormorant|pygmy cormorants (''Microcarbo pygmaeus'')]].<ref name=bli>{{cite web |url=http://datazone.birdlife.org/site/factsheet/lake-ohrid-iba-north-macedonia|title= Lake Ohrid|author=<!--Not stated--> |date=2021|website= BirdLife Data Zone|publisher= BirdLife International|access-date= 10 March 2021}}</ref> The Albanian part of the lake has been designated a separate but corresponding IBA for the same reason, with additional bird species being [[common goldeneye]]s, [[red-crested pochard|red-crested pochards (''Netta rufina'')]] and [[black-necked grebe]]s.<ref name=bli2>{{cite web |url=http://datazone.birdlife.org/site/factsheet/lake-ohrid-and-surrounding-area-iba-albania|title= Lake Ohrid and surrounding area|author=<!--Not stated--> |date=2021|website= BirdLife Data Zone|publisher= BirdLife International|access-date= 10 March 2021}}</ref> Wetland of International Importance status under the Ramsar Convention is underpinned in part by the biogeographically significant populations of red-crested pochard and pygmy cormorants too, but also [[Common merganser|goosander]] (''Mergus merganser'').<ref name=":9" />

==Socio-economy==
[[File:Basilica Lin, Albania 2018 01.jpg|left|thumb|The 6th-century [[Early Christianity|paleochristian]] basilica overlooking the Ohrid Lake in [[Lin, Korçë|Lin]], Albania.]]
The prehistoric pile-dwelling near [[Lin, Korçë|Lin]] in Pogradec, Albania, is Europe's oldest of its kind, as confirmed by [[University of Bern]] specialists. Archaeologists from Albania and Switzerland have been excavating remains on the Ohrid Lake shore and underwater. This settlement, over 8,500 years old, developed [[agriculture]] 8,000–9,000 years ago, playing a key role in spreading farming practices across Europe. The Lin site predates similar Swiss sites by over 2,000 years.<ref>{{Cite web |date=2023-07-19 |title=Lin’s Pile Dwelling Settlement Confirmed Oldests in Europe • IIA |url=https://invest-in-albania.org/lins-pile-dwelling-settlement-confirmed-oldests-in-europe/ |access-date=2024-10-19 |website=invest-in-albania.org |language=en-US}}</ref>

There are three cities on the lake's shores: [[Ohrid]] and [[Struga]] on the Macedonian side; and [[Pogradec]] in Albania. There are also several fishing villages, although tourism is now a more significant part of their income. The catchment area of the lake has a population of around 170,000 people, with 131,000 people living directly at the lake shore (43,000 in Albania and 88,000 in North Macedonia). The population in the catchment has increased by 100,000 people in the last half century, putting the lake's fragile ecosystem under pressure.{{citation needed|date=October 2022}} 

The historic monuments, as well as the pristine lake environment, make the area around Lake Ohrid a prime site for tourism. In the 1980s, more than 200,000 national and international tourists went on a pilgrimage to the Macedonian lake side every year. During the [[Yugoslavia|Yugoslav]] crisis and particularly after the interethnic conflicts within North Macedonia in 2001, international tourism collapsed but has been slowly recovering. Even though many visitors are staying for a weekend only, tourism makes an important contribution to the local economy (~1 visitor/inhabitant).<ref name="spirkovski" /><ref name="model" />[[File:Church of St. John at Kaneo 6.jpg|thumb|[[Church of St. John Kaneo]] and the Ohrid Lake]]Historically, Lake Ohrid was close to a main highway of the Roman Empire, the [[Via Egnatia]], from Durrës on the coast of Albania to Thessalonika and Constantinople (Istanbul), but now is a communications backwater. There is a minor road around the lake, with border crossings between Albania and North Macedonia. Religious monuments such as the Black Madonna south west of Struga and St Naum monastery are counterposed with ravages of war, such as the fortifications of the Macedonian Front across Galicica Mountain.<ref>Kapka Kassabova, To the Lake, a Balkan Journey of War and Peace, Granta 2020</ref>

== World Heritage Site ==
[[File:Ohrid from Samuel's Fortress 2.jpg|thumb|right|View of Ohrid and Ohrid Lake from [[Samuil's Fortress, Ohrid|Samuil's Fortress]]]]
[[File:Pogled kon star Ohrid.tif|thumb|right|View of old Ohrid]]
The Macedonian side of Lake Ohrid was declared a World Heritage Site by UNESCO at the 3rd Session of the [[World Heritage Committee]] in 1979<ref>UNESCO World Heritage Committee (1979) [https://whc.unesco.org/archive/1979/cc-79-conf003-13e.pdf Report of the Rapporteur on the Third Session of the World Heritage Committee].</ref> and holds that status under Criterion VII as a superlative natural phenomenon related to its refuge function for relict and world-unique freshwater species, and its rich bird life.<ref name=":7">{{Cite web|url=https://whc.unesco.org/en/list/99|title=World Heritage List, Natural and Cultural Heritage of the Ohrid Region|last=World Heritage Centre|access-date=16 June 2019}}</ref> The lake became part of a mixed Natural and Cultural World Heritage Site in 1980 when the city of [[Ohrid]] in Macedonia was also designated with UNESCO status for its architectural, artistic and religious values.<ref name=":7" />

Concern over current and potential deterioration of the World Heritage Site prompted invitation of a joint Reactive Monitoring Mission by the World Heritage Centre, IUCN and ICOMOS in April 2017, which identified a wide range of pressures including from transport infrastructure, traffic, tourism developments, overfishing, sewerage, solid waste disposal, invasive species, both legal and illegal construction, and management of water levels.<ref name=":3" /> The mission report devised 19 recommendations for Macedonia, which were incorporated under Decision 41 COM 7B.34  of the World Heritage Committee at its 41st Session in Krakow, Poland in 2017.<ref>World Heritage Committee (2017) [https://whc.unesco.org/en/decisions/7036/ Decision 41 COM 7B.34].</ref>

In May 2019, the [[UNESCO World Heritage Centre]] expanded the World Heritage Site to the Albanian side of the lake.<ref name=":7" /> In addition, draft Decision 43 COM 7B.36 was released<ref>World Heritage Centre (2019) [https://whc.unesco.org/archive/2019/whc19-43com-7B-en.pdf United Nations Educational, Scientific and Cultural Organization, Convention Concerning the World Cultural and Natural Heritage, World Heritage Committee Forty-third Session, Baku, Azerbaijan 30 June - 10 July 2019, Item 7B of the Provisional Agenda: State of conservation of properties inscribed on the World Heritage List].</ref> recommending for the Ohrid region, including Lake Ohrid, to be placed on the [[List of World Heritage in Danger]] during the 43rd Session of the [[World Heritage Committee]] in Baku, Azerbaijan. This position aligns with IUCN advice.<ref>{{Cite web|url=https://www.iucn.org/news/iucn-43whc/201906/iucn-advises-danger-status-three-world-heritage-sites|title=IUCN advises "in danger" status for three World Heritage sites|last=IUCN|date=7 June 2019|access-date=16 June 2019}}</ref> In its analysis and conclusions, the World Heritage Centre observed threats to Lake Ohrid from "decreased water levels, uncontrolled discharge, water pollution due to inadequate wastewater treatment systems leading to evident eutrophication at the mouths of intake rivers, heavy pressures from tourism, and extensive uncontrolled urban development and inappropriate exploitation of the coastal zones." It also observed that the majority of recommendations from the 2017 Reactive Monitoring Mission had not been implemented.

== Science and research ==
Due to its size, accessibility and species richness, Lake Ohrid is extremely well-suited to the function of a natural laboratory.<ref name="Hauffe 2011" /> Deep sediment cores augmented by diverse ecology in the present day offer an extensive archive from which to understand the history of its region over the past 1,200,000 years.<ref>{{Cite web|url=http://www.geologie.uni-koeln.de/2035.html|title=SCOPSCO - Scientific Collaboration On Past Speciation Conditions in Lake Ohrid|date=5 October 2015|website=University of Cologne|access-date=27 June 2019}}</ref><ref>Lorenschat, Julia & Schwalb, Antje (2013) [https://www.researchgate.net/publication/262376171_Autecology_of_the_extant_ostracod_fauna_of_Lake_Ohrid_and_adjacent_waters_-_A_key_to_paleoenvironmental_reconstruction Autecology of the extant ostracod fauna of Lake Ohrid and adjacent waters - a key to paleoenvironmental reconstruction]. Belgian Journal of Zoology, Vol. 143 Issue 1, p42-68. 27.</ref>

Research to date has investigated biodiversity processes,<ref name=":5" /><ref>T. Hauffe, C. Albrecht, K. Schreiber, K. Birkhofer, S. Trajanovski, and T. Wilke (2011) [https://www.biogeosciences.net/8/175/2011/bg-8-175-2011.pdf Spatially explicit analysis of gastropod biodiversity in ancient Lake Ohrid]. Biogeosciences, 8, 175–188.</ref> the interplay between geological and biological evolution,<ref>{{Cite journal|last=Wagner |first=B. |display-authors=etal |date=2017|title=The environmental and evolutionary history of Lake Ohrid (FYROM/Albania)|journal=Biogeosciences|volume=14|pages=2033–2054|doi=10.5194/bg-14-2033-2017 |doi-access=free|hdl=11380/1135662|hdl-access=free}}</ref> the birth of European agriculture,<ref>{{Cite web|url=https://www.unibe.ch/news/media_news/media_relations_e/media_releases/2018/medienmitteilungen_2018/64_million_euros_for_research_into_the_birth_of_agriculture_in_europe/index_eng.html|title=6,4 Million Euros for research into the birth of agriculture in Europe|date=23 October 2018|website=Universitat Bern|access-date=27 June 2019}}</ref> and investigations of regional climate and environmental conditions over hundreds of thousands of years.<ref name=":8">{{Cite journal|last=Sadori |first=L |display-authors=etal |date=2016|title=Pollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (south-eastern Europe) during the past 500 ka.|journal=Biogeosciences|volume=13|issue=5 |pages=1423–1437|doi=10.5194/bg-13-1423-2016 |bibcode=2016BGeo...13.1423S |doi-access=free|hdl=11380/1093769|hdl-access=free}}</ref>

Among other contributions, such research has delivered the first empirical evidence for niche-based assembly processes from a natural system and demonstrated the establishment of dynamic equilibrium in an isolated ecosystem during the slowdown of both speciation and extinction rates.<ref>Species In Ancient Lakes (SIAL) (2018) [http://www.sial-online.org/files/SIAL8_Abstract_Book_small.pdf SIAL 8 Conference Program and Abstracts]. Justus Liebig University Giessen, Germany and Mbarara University of Science and Technology, Uganda.</ref> It has also demonstrated the importance of tree cover for buffering soil erosion during times of climate change<ref>{{Cite news|url=https://theconversation.com/trees-the-ancient-macedonians-and-the-worlds-first-environmental-disaster-116176|title=Trees, the ancient Macedonians, and the world's first environmental disaster |last1=Dosseto |first1=Anthony |last2=Francke |first2=Alex |date=31 May 2019|work=The Conversation|access-date=27 June 2019}}</ref> and provided insight into the composition of regional flora through glacial and inter-glacial periods.<ref name=":8" />

==Human influence==
[[File:Ohrid-Lake.jpg|thumb|The lake coast at [[Sveti Naum|St. Naum Monastery]], with [[Galičica]] Mountain in the background.]]
Shore habitats are under particular pressure from human activities. Particular threats are the building of tourist facilities directly at the shore, destroying of reed belts to gain agricultural land and intense pollution close to the mouth of tributaries. Although the effects of these human impacts have not been evaluated in detail they are of great concern, as the shallow water sites are particularly rich in endemic bottom fauna and form important spawning grounds for several endemic fish species. Moreover, reed belts have great importance for water birds.<ref name="soer" />

Commercial fish yield, i.e. the two endemic [[trout]] species, has dropped significantly over the past decades, both in North Macedonia and in Albania. The most probable reason is [[overfishing]] and possibly destruction of spawning grounds. Pollution may also be a factor.<ref name=":4">{{Cite journal|last1=Jordanova|first1=Maja|last2=Rebok|first2=Katerina|last3=Rocha|first3=Eduardo|title=Liver pathology of female Ohrid trout (Salmo letnica kar.) from the eastern coast of lake ohrid: Baseline data suggesting the presence of a pollution gradient|journal=Turkish Journal of Fisheries and Aquatic Sciences|volume=16|issue=2|doi=10.4194/1303-2712-v16_2_03|year=2016|doi-access=free}}</ref> Although there are regulations regarding fishing practice (e.g. minimal mesh size) and only a limited number of licensed fishermen, these rules are always not obeyed as a result of the high market value of the endemic trout. As a reaction to the situation, a seven-year moratorium on fishing Ohrid trout was imposed from 2004 to help the population recover and to allow scientists to collect further data. Nonetheless, even though thorough assessment of fish stocks has not been conducted since the 1990s<ref name=":1" /> and trout populations are still believed to be in decline,<ref name=":4" /> fishing with quotas was restarted in 2012 under the auspices of a concessionaire.<ref name=":3" /> More data is required to determine whether these current fishing levels are sustainable<ref name=":2" /> and illegal fishing, particularly on the Albanian side of the lake,<ref name=":3" /> remains a problem.

While most of the endemic fish species are non-migratory, the [[European eel]] spawns in the distant [[Sargasso Sea]] while its offspring return to the lake. Unfortunately, as in many European lakes, it is very unlikely today that eels can reach Lake Ohrid naturally and return to the [[Sargasso Sea]], as a result of several hydropower dams on the [[Black Drin]] and the [[Drin River]], both in North Macedonia and Albania. As a result, eel found in Lake Ohrid are stocked populations.<ref name="soer" />

[[File:Pogradec, Lake Ohrid - Albania.jpg|thumb|left|Pogradec along Lake Ohrid]]
Given the population growth over the past 50 years, a particular concern is the potential [[eutrophication]] of currently [[oligotroph]]ic Lake Ohrid from increased pollution. Indeed, [[sediment]] cores show a ~3.5 fold increase in [[phosphorus]] concentration over the past century. On the one hand, shifts from endemic to common European species, which are better adapted to higher nutrient conditions, have already been observed close to polluted inflows. On the other hand, higher nutrient levels have reduced the water transparency, as well as the oxygen availability in the deep water and at the lake bottom, two properties which are requisite for the endemic flora and fauna. Still, the lake is in a comparably good state at the moment. However it may take more than a decade to see the effects of today's pollution level in the lake, because of its long water residence time. Moreover, it was shown that the negative effects from eutrophication would be significantly amplified by [[global warming]]. Although there is time to react, computer simulations indicate that at least a 50% reduction in phosphorus input must be reached to keep the deep water oxygenated for the next 50 years at predicted atmospheric warming. This aim could be reached by controlling household wastewater, which is by far the biggest phosphorus source at the moment. First steps in that direction have been taken by extending and improving the existing sewage system in North Macedonia in the framework of a GEF ([[Global Environment Facility]]) program. The most important next task would be a solution for three remaining, severely polluted tributaries, one in North Macedonia and two in Albania.<ref name="model" /><ref name="soer" />

== Declaration on the Protection of the Lake Ohrid Ecosystem ==
On 3 May 2018, the [[Society of Wetland Scientists]] released the Declaration on the Protection of the Lake Ohrid Ecosystem, which was passed unanimously by 45 attending members at its 13th annual European meeting.<ref>{{Cite web|url=https://ohridsos.org/portfolio/the-declaration-on-the-protection-of-the-lake-ohrid-ecosystem/|title=The Declaration on the Protection of the Lake Ohrid Ecosystem|date=10 May 2018|website=www.ohridsos.org|access-date=28 May 2018}}</ref> Urging Macedonian authorities to substantially enhance protection of Lake Ohrid, the declaration outlines the unique significance of the interconnected Ohrid-Prespa lake system, both for its biodiversity and relevance to research on climate and evolution, and recommends measures for future management including revitalization and enlargement of wetland areas, pollution control and a re-orientation of tourism policy.<ref name=":6">Society of Wetland Scientists (2018) The Declaration on The Protection of the Lake Ohrid Ecosystem (Available 28/5/2018 via http://www.sws.org/images/chapters/europe/Declaration.pdf)</ref> It further describes the "critical importance" of the last intact marsh on the Lake Ohrid shore, [[Studenchishte Marsh]], in terms of its species composition and ecosystem services such as water quality improvement, carbon storage and flood retention among others.<ref name=":6" />

==Namesakes==
Lake Ohrid is also the namesake of [[Ohrid Lacus]], a [[hydrocarbon]] lake on the [[Saturn]]ian moon [[Titan (moon)|Titan]]. It is composed of [[liquid]] [[methane]] and [[ethane]]<ref name="Coustenis2008">{{cite book|last1=Coustenis | first1 = A. | last2 = Taylor |first2 = F. W.|title=Titan: Exploring an Earthlike World|url=https://books.google.com/books?id=j3O47dxrDAQC&pg=PA154|date=21 July 2008|publisher=World Scientific|pages= 154–155|isbn= 978-981-281-161-5}}</ref> and is located 71.8°[[North|N]] 221.9°[[West|W]] on [[titan (moon)|Titan]]'s globe.

==See also==
* [[Tourism in North Macedonia]]
* [[Tourism in Albania]]
* [[Sateska River|River Sateska]]
* [[Studenčište Marsh]]
* [[List of international lakes]]

{{Portal bar|Europe|North Macedonia}}

==Notes==
{{note list}}

==References==
{{Reflist|refs=

<ref name="Korovchinsky, Petkovski" >{{Cite journal
 |title     = The ancient Balkan lakes harbor a new endemic species of Diaphanosoma, Fischer, 1850 (Crustacea: Branchiopoda: Cladocera)
 |first1    = Nikolai M.
 |last1     = Korovchinsky
 |first2    = Trajan K.
 |last2     = Petkovski
 |date      = 1 April 2014
 |journal   = [[Zootaxa]]
 |publisher = Magnolia Press
 |volume    = 3784
 |issue     = 5
 |pages     = 539–549
 |doi       = 10.11646/zootaxa.3784.5.3
 |pmid      = 24872071
 |url       = http://zoobank.org/urn:lsid:zoobank.org:pub:63CBEC43-F367-4088-A1AD-1F85D23A8C12
}}{{Dead link|date=July 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

}}

==External links==
{{Commons category}}
* [http://www.ohrid.gov.mk Ohrid Municipality]
* [http://www.visitohrid.org Official website for Info, Places to visit and reservations in Ohrid]
* [http://www.exploringmacedonia.com Macedonia Tourism portal]
* [https://web.archive.org/web/20190420135906/https://ohrid.com.mk/ Ohrid Information portal]
* [https://web.archive.org/web/20090122230628/http://visitstruga.com.mk/ Struga Tourism portal]
* [http://www.pogradec.info Pogradec Travel Guide]
* {{usurped|1=[https://web.archive.org/web/20030926043842/http://www.worldlakes.org/lakedetails.asp?lakeid=8770 LakeNet Profile]}}
* [http://ohridsos.org Ohrid SOS]
{{Ohrid}}
{{North Macedonia topics}}
{{Albania topics}}
{{World Heritage Sites in Albania}}
{{Lakes in Albania}}
{{Pogradec}}
{{Authority control}}

{{DEFAULTSORT:Ohrid}}

[[Category:Ancient lakes]]
[[Category:Lakes of North Macedonia|Ohrid]]
[[Category:Lakes of Albania|Ohrid]]
[[Category:Albanian Ohrid Lake Coast]]
[[Category:Ohrid]]
[[Category:Albania–North Macedonia border]]
[[Category:World Heritage Sites in North Macedonia]]
[[Category:International lakes of Europe|Ohrid]]
[[Category:Protected landscapes in Albania]]
[[Category:Geography of Korçë County]]
[[Category:Tourist attractions in Korçë County]]
[[Category:Important Bird Areas of Albania]]
[[Category:Important Bird Areas of North Macedonia]]
[[Category:Ramsar sites in North Macedonia]]