Lake Abant

Abant Lake is a natural freshwater lake located within the boundaries of Bolu Province in western Türkiye’s Black Sea region, 18 km northeast of the district of Mudurnu. Situated at an elevation of 1328–1350 meters, it is a tectonic and landslide-formed lake on the Abant Mountains, with a surface area of approximately 125–127 hectares and a maximum depth of 18 meters.

The lake and its surrounding mountainous terrain, forests, and water sources were designated as a “Nature Park” in 1988 and attained the status of a “National Park” on 9 June 2022.

^{Abant Gölü (}Pexels⁾

Abant Lake is a natural dam lake formed by the blocking of the Abant Creek valley by a landslide mass. It lies west of the North Anatolian Fault Line, near the Gerede segment. Fed year-round by snow, rainfall, and small streams, the lake discharges excess water into the Büyüksu Creek via the Abant Creek. The lake surface freezes completely during winter months.

The area surrounding Abant Lake possesses a rich vegetation cover due to its location in the transition zone between the Black Sea and Central Anatolian climate belts and its topographic diversity. Approximately 1305 scientifically identified plant species have been recorded in and near the lake, of which more than 50 are endemic.

• Conifers: Black pine (Pinus nigra), Scots pine (Pinus sylvestris), Uludağ fir (Abies bornmülleriana), Oriental spruce (Picea orientalis)
• Deciduous trees: Oak (Quercus spp.), Oriental beech (Fagus orientalis), hornbeam (Carpinus betulus), aspen (Populus tremula), ash (Fraxinus spp.), chestnut (Castanea sativa)

• Hazelnut (Corylus avellana), juniper (Juniperus spp.), rhododendron (Rhododendron spp.), hawthorn (Crataegus spp.), holly (Ilex aquifolium), dog rose (Rosa canina), blackberry, nettle, ivy, mint, lady fern, hollyhock and horse-tail are among the species found throughout the lake area

• Crocus abantensis (Abant crocus): Grows exclusively on high plateaus around the lake. Protected under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention).
• Ornithogalum pascheanum, Poa asiae-minoris: Rare species known to grow only in Abant.

Aquatic macrophytes found along the lake shore include:

• Common reed (Phragmites australis), bulrush (Schoenoplectus lacustris), yellow water-lily (Nuphar lutea), white water-lily (Nymphaea alba), floating pondweed (Potamogeton natans), common duckweed (Lemna minor), jointed rush (Juncus articulatus), spiked water-milfoil (Myriophyllum spicatum), and whorled water-milfoil (M. verticillatum)

Abant Lake and its surroundings host a wide variety of vertebrate and invertebrate species through their terrestrial and aquatic ecosystems.

• Endemic: Muscardinus avellanarius abanticus (Abant hazel mouse), detected only in this region.
• Other species: Red deer, roe deer, bear, wolf, fox, jackal, hare, pine marten, squirrel and Eurasian beaver. Beavers are classified as threatened due to habitat loss.

• Salmo trutta fario var. abanticus (Abant trout): An endemic trout species unique to the lake’s ecosystem, formally described in scientific literature. Controlled recreational fishing is permitted to ensure its conservation.

• “Small crested newt” (scientific name not yet formally established in systematic literature): Observed only around Abant Lake and not recorded anywhere else in the world.

Birds

• Waterfowl: Mallard, wild goose, pochard, tufted duck, crane, kingfisher
• Raptors: Goshawk, sparrowhawk, golden eagle, black kite, tawny owl
• Other species: Jay, magpie, chaffinch, blackbird, nightingale, blue tit, goldfinch, linnet.

Butterflies

• The region is home to the threatened Apollo butterfly (Parnassius apollo) and the Caucasian fritillary (Zerynthia caucasica).

Macrophyte studies and water quality monitoring data indicate that Abant Lake exhibits moderate nutrient enrichment (eutrophication). Macrophyte density increases notably during summer and autumn, with certain species becoming dominant.

Measured Values

• Macrophyte Index (MI): 2.85
• Ecological Quality Ratio (EQR): 0.52 (moderate quality)
• Average water temperature: 11.5 °C
• pH: Ranges between 7.5 and 8.2
• Dissolved oxygen: 8–12 mg/L
• Electrical conductivity: Average 219–230 µS/cm
• Heavy metals: Cadmium, lead, chromium and mercury detected (in some periods exceeding hazardous thresholds).

• Abant Lake was declared a nature park in 1988 and a national park in 2022.
• The lake is classified as a “Sensitive Area” with respect to eutrophication.

The physicochemical variables of Abant Lake (temperature, dissolved oxygen, pH, conductivity, etc.) vary seasonally. Average temperature ranges from 10–12 °C and pH from 7.5 to 8.0. Studies have detected the presence of heavy metals such as cadmium, lead and mercury in the lake. Their accumulation in plankton and aquatic organisms varies by season.

Based on macrophyte analyses, the ecological quality of Abant Lake is rated as “good” and its nutrient enrichment as “moderate.” Measurements conducted in 2015 yielded a Macrophyte Index (MI) of 2.85 and an Ecological Quality Ratio (EQR) of 0.52.

The lake and its surroundings were placed under protection as a nature park in 1988 and became Türkiye’s 48th national park in 2022. Since 2003, a “long-term development plan” has aimed to preserve the area, manage tourism pressure and ensure sustainable use.

Major threats include overgrazing, illegal hunting, introduction of non-native species into aquatic environments and uncontrolled tourism activities. Particularly day-trip tourism and hotel construction damage the vegetation cover. In 2015, the lake was designated a “Sensitive Area” due to eutrophication risk.

Abant Lake was discovered in the 1920s and began to be promoted as a tourist destination from the 1930s onward. Atatürk’s visit to Abant during his 1934 trip to Bolu significantly contributed to the region’s promotion.

Today, the lake area is enriched with accommodation facilities, walking trails, a nature museum, viewing terraces, restaurants and cafés, tented camping areas and sport fishing opportunities, alongside its natural landscape. The national park attracts visitors year-round, with peak demand during winter and holiday periods. In 2023, it was visited by 571,162 people.

Access to the lake has been regulated since 2023 through the HGS system. Open fires and wood-burning barbecues are prohibited around the lake; only gas or electric stoves are permitted.