Korhan Özkan

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• PhD
• Professor at Middle East Technical University

Microplastic (MP) pollution was investigated in the sediment of lakes on Robert Island in the South Shetland Islands located in the northwest of the Antarctic Peninsula. Sediment samples were taken from a glacial lake (L1) and three coastal lakes (L2, L3 and L4) in March and April 2018 as part of the Turkish Antarctic Science Expedition-II (TAE-II)...

Submerged macrophytes play a crucial role as primary producers and contribute essential ecosystem functions and services. We aimed to assess the effects of simulated climate warming (4.5 ºC) on the functional trait responses of a submerged macrophyte, Stuckenia pectinata (L.) Börner, in a synchronized oligohaline (4 ppt salinity) mesocosm experimen...

Understanding how the causal feedback between phytoplankton and environmental drivers controlling the chlorophyll a (Chl a, as a proxy of phytoplankton biomass)–nutrient relationships are modulated under different ecosystem conditions is a major challenge in aquatic ecology. Using an empirical dynamic model (convergent cross mapping) on a 20‐yr dat...

Phytoplankton taxa are strongly interconnected as a network, which could show temporal dynamics and non-linear responses to changes in drivers at both seasonal and long-term scale. Using a high quality dataset of 20 Danish lakes (1989-2008), we applied extended Local Similarity Analysis to construct temporal network of phytoplankton communities for...

The regions of Bolkar Mountains and Aladağlar accommodate a unique ecosystem in Turkey, due to being in a transitional climate between the continental and the Mediterranean and hosting alpine lakes which are considered as good indicators of regional and atmospheric pollution due to being far from direct human impact. On the other hand, these region...

Salinization of freshwater ecosystems is one of the major challenges imposed largely by climate change and excessive water abstraction for irrigated crop farming. Understanding how aquatic ecosystems respond to salinization is essential for mitigation and adaptation to the changing climate, especially in arid landscapes. Field observations provide...

Climate change is affecting freshwater ecosystems globally, particularly those in semi-arid and arid regions. The Central Anatolian Ecoregion (CAE) in Türkiye has a semi-arid climate and is home to numerous endemic fish species. We used species distribution modelling to elucidate the distribution of sixteen endemic fish species in CAE and predicted...

Cold environments are considered extreme biomes and historically thought to be barren and unproductive. However, investigations show that some of the coldest regions in the world represent unique biodiversity hotspots. In this review, the prominent diatom communities of alpine lakes and ponds across different parts of the world, including the Arcti...

With the retreat of glaciers, new ponds and lakes are often formed. These are gradually col-onised and become more productive as vegetation develops in their catchments, creating more complex food webs. Near the Jakobshavn Isbrae in West Greenland, we studied trophic structure and food web complexity using stable isotopes in 26 lakes belonging to t...

Global warming and altered precipitation patterns are predicted to intensify the water loss in semi-arid and arid regions, and such regions in Turkey will be particularly affected. Moreover , water abstraction, not least for irrigation purposes, is expected to increase markedly, posing major threats to the water balance of the lakes and thus their...

The structure and functioning of Arctic ecosystems have been drastically modified by global warming, with fish species potentially performing habitat shifts such as the northern expansion of generalist and warm-adapted species. The freshwater fish species Arctic charr (Salvelinus alpinus, hereafter charr) plays a key role in Arctic lake food webs,...

Eşsiz doğa güzelliği ve canlı çeşitliliğine sahip ülkemizin tüm kuş türlerini içerisinde barındıran, metinlerinden görsel malzemesine kadar tümüyle özgün olması açısından “ilk” kuş tanım kitabı niteliğindeki TRAKUS Türkiye’nin Kuşları doğa ve kuşlara olan ilgisini geliştirmek isteyenlere rehberlik etmek için hazırlandı. 7 gram ağırlığı ile Çalıkuş...

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and tot...

The Konya Closed Basin (KCB) in Turkey has a cold semiarid to warm Mediterranean climate and hosts the largest Turkish freshwater lake, Lake Beyşehir, and the iconic saline Lake Tuz. Using published as well as our own ground-truth and remote sensing data, we provide (1) a brief description of the paleoenvironmental changes in the KCB; followed by (...

Human-induced changes in external nutrient loading affect the phytoplankton community and abundance directly by changing the amount of nutrients available, but also indirectly through changes in the zooplankton (that is, grazer) community structure, mediated in part by changes in the fish community structure and biomass. Such shifts affect the spec...

Seasonal and annual dynamics of the zooplankton community in lakes are affected by changes in abiotic drivers, trophic interactions (e.g., changes in phytoplankton and fish communities and abundances) and habitat characteristics (e.g. macrophyte abundance and composition). However, little is known about the temporal responses of the zooplankton com...

Tufted Ghost Crabs (Ocypode cursor) experience local population declines and also range contractions at larger spatial scales due to increasing anthropogenic pressures on coastal ecosystems. Therefore, the environmental drivers of the decline in ghost crab populations and the efficiency of protection measures are needed to be better understood for...

Son dönemde Marmara Denizi’nde yoğunlukla gözlemlenen; görsel, ekolojik ve ticari yönlerden sebep olduğu olumsuz etkileri nedeniyle kamuoyunun gündemine oturan deniz salyası sadece bugün değil geleceğimizi için de tehlike oluşturuyor. Bu bağlamda Türkiye Bilimler Akademisi Başkanlığı, konusunda uzman bilim insanları bu çevre sorununu değerlendirmel...

The cover image is based on the Original Article Changes in functional composition and diversity of waterbirds: The roles of water level and submerged macrophytes, by İbrahim Kaan Özgencil https://doi.org/10.1111/fwb.13531.

World-wide, reducing the external nutrient loading to lakes has been the primary priority of lake management in the restoration of eutrophic lakes over the past decades, and as expected this has resulted in an increase in the local environmental heterogeneity, and thus biotic heterogeneity, within lakes. However, little is known about how the regio...

• Water level and submerged macrophytes are critical players for the functioning of shallow lake ecosystems; understanding how waterbird communities respond to changes in both can have important implications for conservation and management. Here, we evaluated the effects of changes in water level and submerged macrophyte status on wintering waterbi...

Climate warming threatens the structure and function of shallow lakes, not least those in the Mediterranean climate. We used a space-for-time substitution approach to assess the response of trophic and community structures as well as the richness and evenness of multiple trophic levels to temperature, hydrological, and nutrient constraints. We sele...

We tested for the first time the efficiency of the use of infra-red (IR) cameras for sea turtle hatchling monitoring. The cameras were installed on one green turtle (Chelonia mydas) and four loggerhead turtle (Caretta caretta) nests during 2014 and 2015 nesting season in the southeast Mediterranean, Turkey. The camera monitoring, even with the limi...

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent probl...

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to thei...

Insight into how environmental change determines the production and distribution ofcyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus onhepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g.,anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their p...

METU Erdemli Campus as a functioning wildlife habitat! We live in the beginning of Anthropocene, and wild life habitats are disappearing at an unprecedented rate! Natural parks are not enough to save the planet and new conservation ideas, where humans and natural ecosystems can co-exist, are needed. University campuses can be ideal pilot study area...

Seabirds are located at higher levels of marine food webs. Therefore, the distribution and abundance of seabird populations are important indicators of well-being of the marine ecosystems. North East Mediterranean Coast has high human activity like heavy industry and fisheries, whereas also hosts important environmental protection areas supporting...

Eutrophication continues to be the most important problem preventing a favorable environmental state and detrimentally impacting the ecosystem services of lakes. The current study describes the results of analyses of 20 year monitoring data from two interconnected Anatolian lakes, Lakes Mogan and Eymir, receiving sewage effluents and undergoing res...

Abstract For understanding emergence behaviour of turtle hatchlings, one of the ten Chelonia mydas (green sea turtle) nests, produced during nesting season 2014 at a beach in the northeastern Mediterranean (Erdemli, Turkey) was surveyed during nesting hatching period, using an infra-red (IR) camera. After hatching the nest was excavated for the an...

A two-decade (1989–2008) time series of lake phyto-and zooplankton, water characteristics and climate in 17 Danish lakes was analysed to examine the long term changes and the effects of lake restoration efforts. The analyses of the pair-wise correlations across time series revealed a strong synchrony in climatic variables among the lakes. A signifi...

1. To help improve our understanding of the nitrogen cycle in lakes, particularly in the context of climate change, we analysed total nitrogen (TN) and nitrate (NO � 3 -N) data from six mesocosm experiments (in Denmark, U.K., China and Turkey) covering different climatic regions. We assessed the effects of nitrogen (N) and phosphorus (P) loading, t...

To help improve our understanding of the nitrogen cycle in lakes, particularly in the context of climate change, we analysed total nitrogen ( TN ) and nitrate ( ‐N) data from six mesocosm experiments (in Denmark, U.K., China and Turkey) covering different climatic regions. We assessed the effects of nitrogen (N) and phosphorus (P) loading, temperat...

Groups of organisms often have congruent patterns of diversity or community structure due to similar environmental requirements. However, ecological interactions across trophic levels may also promote congruence independent of environmental drivers through selective predation, niche partitioning, or facilitation. We examined congruence between phyt...

1. Climate warming in (sub)arctic regions is expected to increase freshwater fish overwinter survival and dispersal, potentially with strong implications for macroinvertebrate assemblage composition and ecosystem processes. Several studies worldwide have shown large effects of top predators (usually fish) on macroinvertebrates in streams. However,...

Climate warming in (sub)arctic regions is expected to increase freshwater fish overwinter survival and dispersal, potentially with strong implications for macroinvertebrate assemblage composition and ecosystem processes. Several studies worldwide have shown large effects of top predators (usually fish) on macroinvertebrates in streams. However, the...

Environmental species sorting and dispersal are seen as key factors in community assembly, but their relative importance and scale dependence remain uncertain, as the extent to which communities are consistently assembled throughout their biomes. To address these issues, we analysed bird metacommunity structure in a 1200‐km ² forested landscape (Is...

Eutrophication resulting from high nutrient loading has been the paramount environmental problem for lakes world-wide for the past four decades. Efforts are being made in many parts of the world to reduce external nutrient loading via improved wastewater treatment or diversion of nutrient-rich inflows. However, even after a reduction of the externa...

Understanding of the forces driving the structure of biotic communities has long been an important focus for ecology, with implications for applied and conservation science. To elucidate the factors driving phytoplankton genus richness in the Danish landscape, we analyzed data derived from late-summer samplings in 195 Danish lakes and ponds in a sp...

Climate change might have profound effects on the nitrogen (N) dynamics in the cultivated landscape as well as on N transport in streams and the eutrophication of lakes. N loading from land to streams is expected to increase in North European temperate lakes due to higher winter rainfall and changes in cropping patterns. Scenario (IPCC, A2) analyse...

A breeding bird survey in the Istranca (Yıldız) mountains of Turkish Thrace seawards to the Black sea was conducted May–August 2009. Eighty-eight days of field work in 697 locations generated novel breeding evidence for several species. The survey provided the first certain evidence of Wood Warbler Phylloscopus sibilatrix breeding in Turkey. Strong...

1. Recent experimental and field studies on temperate shallow lakes indicate that nitrogen may play a greater role in their functioning than previously thought. Several studies document that abundance and richness of submerged macrophytes, both central in shallow lake ecology, may decrease with increasing nitrogen loading, especially at high phosph...