شناسایی، معرفی و نوسانات جمعیت سخت پوستان کلادوسر و کوپه پود در دریاچه تار- دماوند

پیشینه و اهداف: دریاچه تار در ارتفاع 3230 متری از سطح دریا و درمیان کوه هایی قرار گرفته است که از سطح دریاچه بین 50 تا 500 متر ارتفاع دارند. وجود این ارتفاعات در کنار یکدیگر بدون آنکه دره‌ای آن را شکافته باشد موجب پیدایش گودالی شده است که دریاچه تار در آن قرار گرفته است. زوپلانکتون های سخت پوست و بویژه کلادوسرا نقش مهمی را در اکثر دریاچه های آب شیرین برعهده دارند و به دلیل حساسیت به تغییرات محیطی در گروه شاخص های زیستی مهم برای ارزیابی کیفیت آب و سلامت اکوسیستم مورد توجه قرار گرفته‌اند. لذا  این مطالعه در خصوص شناسایی، معرفی، مطالعه ساختار، تنوع و بوم‌شناسی گونه‌های مختلف سخت پوستان کوچک در دریاچه‌ کوهستانی تار انجام شد.روش‌ها‌: در این تحقیق نمونه برداری در امتداد سه ایستگاه به صورت ماهانه بین فروردین تا شهریور1400  انجام شد و پارامترهای محیطی شامل دمای آب، ph، هدایت الکتریکی (ec)، و اکسیژن محلول (do) در محل اندازه گیری شدند. همچنین به منظور تجزیه و تحلیل کمی، در هر نمونه برداری زوپلانکتون ها با فیلتراسیون 100 لیتر آب توسط تور پلانکتون 100 میکرون جمع آوری گردیدند. یافته‌ها: در دریاچه تار و طی ماه های مورد مطالعه، مقادیر اکسیژن محلول (do) بالا بود و بالاترین مقدار در ماه فروردین به حداکثر 13 میلی‌گرم در لیتر رسید. مقادیر ph در طول دوره بررسی بین 23/7 تا 3/8 متغیر بود که نشان می دهد مقادیر قلیایی و دامنه کم تغییرات تحت تاثیر ذوب برف و زمین‌شناسی محیط اطراف قرار دارد. این در حالی است که مقادیر و الگوی فصلی پارامترهای محیطی در محدوده دامنه پارامترهای دریاچه های الیگوتروفیک قرار دارد. همچنین در دریاچه تار طی ماه های بدون یخبندان، سه گونه دافنی وچهار گونه سیکلوپویید شناسایی شدند. daphnia laevis و daphnia ambigua به ‌عنوان رایج‌ترین و فراوان‌ترین گونه‌های سخت پوستان ثبت‌شده شناخته شدند. گونه های سیکلوپویید شناساسایی شده عبارت بودند از: cyclops scutifer، cyclops latipes، cyclops venustus و cyclops exilis. در جامعه‌ی سخت‌پوستان دریاچه تار،  فراوانی کوپه پودهای بالغ سیکلوپوئید بمراتب کمتر از فراوانی  کلادوسرا بود (43 عدد در متر مکعب)، و علیرغم غالبیت کلادوسرا،  میانگین تراکم جمعیت گونه های دافنی به حداکثر480 عدد در متر مکعب رسید که در محدوده تراکم کلادوسرا در دریاچه های کوهستانی الیگوتروفیک است. همچنین نتایج نشان داد دریاچه تار یک دریاچه تیپیک کلادوسر- کوپه پود و به شکل خاص دریاچه تیپیک دافنی- سیکلوپس است که در آن ماهی‌های پلانکتون‌خوار حضور ندارند.نتیجه‌گیری: در این دریاچه کوچک و دورافتاده، بیشتر عواملی که می‌توانند بر حضور و توزیع زئوپلانکتون‌ها تاثیر بگذارند، از نظر زمانی متغیر و غیرقابل پیش‌بینی هستند. نتایج مربوط به ترکیب سخت پوستان کلادوسر و کوپه پود مشتمل بر اولین ثبت گونه های daphnia laevis، daphnia ambigua ،daphnia rosea cyclops scutifer، cyclops latipes، cyclops venustus و cyclops exilis در ایران، و نقش مهمی که دریاچه های خاص کوهستانی می‌توانند به‌عنوان ذخایر تنوع زیستی آبی ایفا کنند، را روشن ساخت. در نهایت بنظر می رسد این دریاچه های طبیعی، کهن و منحصر به فرد نیازمند تلاش‌های بیشتری در زمینه تحقیق و پایش، از جمله مطالعات مرتبط با مهاجرت های عمودی و مکانیسم‌های تطبیقی جوامع سخت پوستان در دوره های یخبندان هستند.

identification, introduction, and population fluctuations of cladocerans and copepods in lake tar, damavand

background and objectives: lake tar is situated at an altitude of 3,230 meters above sea level and is surrounded by mountains ranging from 50 to 500 meters in height above the lake. the existence of these elevations next to each other, without a valley splitting them, has created a depression in which lake tar has formed. crustacean zooplankton, especially cladocera, play a significant role in most freshwater lakes and have become important bioindicators for assessing water quality and ecosystem health due to their sensitivity to environmental changes. therefore, this study was conducted regarding the diversity and ecology of various microcrustacean species in the mountain lake tar.methods: in this study, sampling was conducted monthly along three stations from april to september 2021, and environmental parameters including water temperature, ph, electrical conductivity (ec), and dissolved oxygen (do) were measured on-site. additionally, for quantitative analysis, zooplankton were collected by filtering 100 liters of water through a 100-micron plankton net during each sampling.findings: in lake tar, during the studied months, dissolved oxygen (do) levels were high, with the highest value reaching a maximum of 13 milligrams per liter in april. the ph values varied between 7.23 and 8.3 during the study period, indicating alkaline values and a low range of variability influenced by snowmelt and the geology of the surrounding environment. meanwhile, the values and seasonal patterns of environmental parameters fell within the range characteristic of oligotrophic lakes. additionally, during the ice-free months in lake tar, three species of daphnia and four species of cyclopoid were identified. daphnia laevis and daphnia ambigua were recognized as the most common and abundant recorded crustacean species. the identified cyclopoid species included cyclops scutifer, cyclops latipes, cyclops venustus, and cyclops exilis. in the crustacean community of lake tar, the abundance of adult cyclopoid copepods was significantly less than that of cladocera (43 individuals per cubic meter). despite the dominance of cladocera, the average population density of daphnia species reached a maximum of 480 individuals per cubic meter, which is within the density range of cladocera in oligotrophic mountain lakes. the results also indicated that lake tar is a typical cladocera-copepod lake and specifically a typical daphnia-cyclops lake, in which planktivorous fish are absent.conclusion: in this small and remote lake, most factors that can affect the presence and distribution of zooplankton are temporally variable and unpredictable. the results regarding the composition of cladocera and copepod crustaceans included the first records of daphnia laevis, daphnia ambigua, cyclops scutifer, cyclops latipes, cyclops venustus, and cyclops exilis in iran, highlighting the important role that specific mountain lakes can play as aquatic biodiversity reserves. ultimately, it seems that these natural, ancient, and unique lakes require greater efforts in research and monitoring, including studies related to vertical migrations and the adaptive mechanisms of crustacean communities during freezing periods.background and objectives: lake tar is situated at an altitude of 3,230 meters above sea level and is surrounded by mountains ranging from 50 to 500 meters in height above the lake. the existence of these elevations next to each other, without a valley splitting them, has created a depression in which lake tar has formed. crustacean zooplankton, especially cladocera, play a significant role in most freshwater lakes and have become important bioindicators for assessing water quality and ecosystem health due to their sensitivity to environmental changes. therefore, this study was conducted regarding the diversity and ecology of various microcrustacean species in the mountain lake tar.methods: in this study, sampling was conducted monthly along three stations from april to september 2021, and environmental parameters including water temperature, ph, electrical conductivity (ec), and dissolved oxygen (do) were measured on-site. additionally, for quantitative analysis, zooplankton were collected by filtering 100 liters of water through a 100-micron plankton net during each sampling.findings: in lake tar, during the studied months, dissolved oxygen (do) levels were high, with the highest value reaching a maximum of 13 milligrams per liter in april. the ph values varied between 7.23 and 8.3 during the study period, indicating alkaline values and a low range of variability influenced by snowmelt and the geology of the surrounding environment. meanwhile, the values and seasonal patterns of environmental parameters fell within the range characteristic of oligotrophic lakes. additionally, during the ice-free months in lake tar, three species of daphnia and four species of cyclopoid were identified. daphnia laevis and daphnia ambigua were recognized as the most common and abundant recorded crustacean species. the identified cyclopoid species included cyclops scutifer, cyclops latipes, cyclops venustus, and cyclops exilis. in the crustacean community of lake tar, the abundance of adult cyclopoid copepods was significantly less than that of cladocera (43 individuals per cubic meter). despite the dominance of cladocera, the average population density of daphnia species reached a maximum of 480 individuals per cubic meter, which is within the density range of cladocera in oligotrophic mountain lakes. the results also indicated that lake tar is a typical cladocera-copepod lake and specifically a typical daphnia-cyclops lake, in which planktivorous fish are absent.conclusion: in this small and remote lake, most factors that can affect the presence and distribution of zooplankton are temporally variable and unpredictable. the results regarding the composition of cladocera and copepod crustaceans included the first records of daphnia laevis, daphnia ambigua, cyclops scutifer, cyclops latipes, cyclops venustus, and cyclops exilis in iran, highlighting the important role that specific mountain lakes can play as aquatic biodiversity reserves. ultimately, it seems that these natural, ancient, and unique lakes require greater efforts in research and monitoring, including studies related to vertical migrations and the adaptive mechanisms of crustacean communities during freezing periods.