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Lagoons are valuable ecosystems providing various services, such as fishing, recreational activities, and land reclamation, as well as hosting high biodiversity. Although lagoons in Turkey cover a coastal area of more than 36,000 ha, few studies of them have been conducted. Therefore, two lagoons (Dalyan and Arapciftligi) located on the coast of the Sea of Marmara in the Kocacay Delta, which is under intense anthropogenic pressure, were investigated between November 2013 and March 2015 to examine the effects of environmental factors on taxonomic diversity. In addition, ongoing high nutrient flow from the Karacabey region triggers eutrophication in the lagoons, thus causing low water transparency. In both lagoons, the zooplankton assemblages were mainly dominated by cosmopolite and eurytopic taxa. Calanoid copepod Acartia clausi was the dominant species in both lagoons and showed seasonal variation, while no seasonality appeared in nauplii. The high abundance of rotifer species of the genera Keratella and Brachionus reflects the harsh conditions in the lagoons, caused by cultural eutrophication, dystrophy, and salinity increase and also by the temperature-enhanced decrease in zooplankton evenness and richness. Flushing rate, precipitation, high temperature, and salinity influence the species composition, which shifted to a greater dominance by hypoxia/salinity-tolerant zooplankters, resulting in lower species diversity in the lagoons.

Kizilirmak River has been used as Ankara’s drinking water source for approximately 1.5 years. Therefore, this region’s water, sediment, and fish samples are measured for detecting the heavy metals. This is important for the current situation as well as the future in terms of potential impact. The amount of heavy metals in drinking water should be within the limited values; otherwise, the accumulation of heavy metals will cause many problems to living organisms. Especially high levels of arsenic, cadmium, nickel, mercury, etc. are very dangerous to freshwater ecosystems as for human if the water is being use as drinking water. In this study, water, sediment samples, muscle, and gills of three fish species (Capoeta tinca, Capoeta capoeta, Leuciscus cephalus) were analyzed for the presence of heavy metals such as (Al, Fe, As, Cd, Ni, Mn, Se, Si) to determine present accumulation levels and possible toxic effect. The accumulation pattern of heavy metals in the water, sediment, and fish tissue follows the sequence: Si > Fe > Al > Mn > As > Ni > Se > Cd, Fe > Al > Mn > Ni > As > Se > Cd, and Fe > Al > Mn > As > Ni > Si > Cd. In addition, the detected concentrations of heavy metals in the Kizilirmak and Delice Rivers are compared with other heavy metal studies in the other main rivers and lakes in Turkey.

The seasonal occurrence of medicinal leeches was studied at two lakes in the Black Sea coastland of north-western Turkey. The number of leeches attracted by a collector per hour was taken as an indicator for population density. Leeches were most abundant in May/June, and were almost absent during the cold season (November – March). Leeches with a weight of less than 1 g occurred principally between July and October with a peak in July. It is thought that these individuals represent newly hatched leeches. Although both study areas are close to each other, significant differences were found in respect to mean leech size and the seasonal frequency of leeches (both total number and certain age classes). It is suggested that leech biology is greatly dependent on factors such as microclimate and the availability of hosts, and no general conclusions on phenology can be drawn. There is therefore no scientific basis for restricting commercial leech collecting to certain months of the year.

A survey of all the major potential habitats in western Turkey showed that medicinal leeches, Hirudo medicinalis L., are widely distributed over the country and are not rare. They occur in practically all suitable habitats and the only region where they were found to be absent is that of the large river deltas in the south of the country (Cukurova deltas, Goksu delta). There may be zoogeographic reasons for this (Taurus mountains barrier). The application of a semi-quantitative survey method using collecting efficiency (number of leeches collected per hour by a single person) allowed a rapid assessment to be made of its status in a large number of wetlands. Leech density varied considerably from wetland to wetland, and the results enabled a ranking of the Turkish wetlands to be made according to their importance for medicinal leeches. Taking both the leech density and the size of leech habitats into account, the largest populations were identified on the Black Sea coast (Kizilirmak delta, Yesilirmak delta and Karagol Marshes near Sinop) and in inner and south-west Anatolia (Eber Golu, Karamik and Sultan Marshes). Commercial exploitation for the pharmaceutical industry and for other purposes takes place at only a few places and does not appear to affect the population seriously. However, many populations are threatened by the draining of their habitats.

The accumulation of heavy metals such as Pb, Hg, Co, Cr, Cu, Zn, and Br were determined in water, sediment, muscle, and gill of three fish species (Leuciscus cephalus, Capoeta tinca, Capoeta capoeta) which were collected in KA +/- zA +/- lA +/- rmak River Basin (Delice River). The metal concentration showed a general trend of Br > Zn > Pb > Cr > Cu > Hg > Co in water and Cr > Zn > Pb > Cu > Co > Hg > Br in sediment samples while Zn > Cu > Pb > Br > Cr > Hg > Co were in muscle and Zn > Pb > Cu > Cr > Br > Hg > Co were in the gill tissue.

In this study Cyanobacteria species of Mogan Lake, Beytepe Pond and Delice River were taxonomically investigated. The cyanobacteria specimens have been collected by monthly intervals from Mogan Lake and Beytepe Pond between October 2010 and September 2011. For the Delice River the laboratory samples which were collected by montly intervals between July 2007-May 2008 have been evaluated.Totally 15 genus and 41 taxa were identified, 22 species from Mogan lake, 19 species from Beytepe pond and 13 species from Delice river respectively. During the study species like Planktolyngbya limnetica and Aphanocapsa incerta were frequently observed for all months in Mogan Lake, Chrococcus turgidus and Chrococcus minimus were abundant in Beytepe Pond while Kamptonema formosum was dominant in Delice River. As a result species diversity and density were generally rich in Mogan Lake during fall and summer season while very low in the Delice River during winter season