A research on dessication resistance in stream macrobenthic invertebrates

Global climate change and human activities cause a variety of impacts on almost every ecosystem on Earth. One such environment is the streams, one of the freshwater ecosystems. Streams face the risk of drying up with each passing day due to climate change and anthropogenic effects. There is no doubt that macrobenthic invertebrates living in these areas will be affected in the case of rivers drying up. However, there is not enough information about which groups among macrobenthic invertebrates will be affected by the drying and how long they can survive in a desiccated environment. In search of this information, this thesis study was carried out with the goal to determine the survival times of various macrobenthic invertebrates obtained from Karasu (Istanbul) and Davul (Kocaeli) streams in a dry environment, in other words, their tolerance to desiccation. For this, field studies were carried out in the years 2021 and 2022 and some physico-chemical data of the stations were recorded. As a result of the field studies, 9 orders (Amphipoda, Ephemeroptera, Odonata, Diptera, Hemiptera, Coleoptera, Trichoptera, Oligochaeta and Gastropoda) and 15 families (Gammaridae, Caenidae, Gomphidae, Libellulidae, Calopterygidae, Platycnemidae, Tabanidae, Chironomidae, Psychodidae, Tipulidae, Corixidae, Pleidae, Dytiscidae, Limnephilidae and Lymnaeidae) and 12 species (Gammarus sp., Caenis rivulorum Eaton, 1884, Gomphus vulgatissimus Linnaeus, 1758, Onychogomphus forcipatus Linnaeus, 1758, Orthetrum coerulescens Fabricius, 1798, Calopteryx virgo Linnaeus, 1758, Platycnemis pennipes Pallas, 1771, Tabanus sp., Copropsychoda sp., Tipula sp., Platambus sp. and Helophorus sp.) were found. These families and species are new records for both Karasu and Davul streams. Desiccation experiments were carried out on 270 total individuals. Results of these experiments demonstrated that, all the individuals belonging to the Chironomidae family could survive for only one hour in the desiccated environment, while the invertebrate that survived the longest (168 hours) was an individual belonging to the Gomphus vulgatissimus species. It was observed that 50% of the individuals used in the experiment died within the first six hours in a completely desiccated environment. This is the first study on the extent of the impacts that may occur on macrobenthic invertebrates living in streams due to the loss of their water content as a result of drought or human effects. It also reveals the desiccation tolerance of different macrobenthic invertebrate groups in Turkey with temporal values for the first time.