پديد آورندگان :
اولادي كلاريجاني، مهشيد دانشگاه شهيد بهشتي، تهران - دانشكده علوم و فناوري زيستي - گروه زيست شناسي و زيست فناوري دريا و آبزيان , شكري، محمدرضا دانشگاه شهيد بهشتي، تهران - دانشكده علوم و فناوري زيستي - گروه زيست شناسي و زيست فناوري دريا و آبزيان , رجبي مهام، حسن دانشگاه شهيد بهشتي، تهران - دانشكده علوم و فناوري زيستي - گروه علوم و زيست فناوري جانوري
كليدواژه :
زوگزانتلا , سفيد شدگي , ضريب ميتوزي , رنگدانه , خليج فارس , جزيره قشم
چكيده فارسي :
در اين مطالعه وجود تنش در مرجان‌هاي گونه Wallace, 1999 Acropora downingi با مقايسه خصوصيات مورفولوژيك و پويايي‌جمعيت جلبك همزيست آن‌ها (زوگزانتلا) در كلوني‌هاي نرمال و سفيد شده در جزيره قشم مورد بررسي قرار گرفت. كلوني‌هاي نرمال و سفيدشده مرجان در پاييز 1394 طي عمليات غواصي از جنوب شرقي جزيره قشم جمع‌آوري شدند. شكل‌هاي مختلف زوگزانتلا (سالم، رنگ‌پريده، تخريب شده و درحال تقسيم) زير ميكروسكوپ نوري مورد بررسي قرار گرفت و توسط لام هموسيتومتر شمارش گرديد. همچنين غلظت رنگدانه‌هاي كلروفيل α و c توسط روش اسپكتروفتومتري بدست آمد و ميزان تمامي متغيرها بين كلوني‌هاي سالم مرجاني و كلوني‌هايي كه در اثر تنش سفيد شده بودند، مقايسه شد. نتايج نشان داد كه تراكم زوگزانتلا بطور كلي در كلوني مرجاني سفيد شده 32 درصد نسبت به كلوني نرمال كاهش يافته است. در اين ميان تراكم زوگزانتلا‌هاي سالم 25 درصد در كلوني تحت تنش كاهش يافته و برعكس به طور معناداري تراكم زوگزانتلا‌هاي رنگ‌پريده (t=7.03, P=0.00) و تخريب شده (t=3.56, p=0.02) در كلوني مرجان تحت تنش نسبت به كلوني سالم افزايش داشته است. همچنين ضريب ميتوزي در كلوني‌هاي مرجاني سفيدشده افزايش معناداري نسبت به كلوني‌هاي سالم داشت (z=-3/06, P=0.002). هرچند اختلاف معناداري در ميزان رنگدانه‌هاي كلروفيل α (t=0.49, P=0.63) و كلروفيل c (t=0.13, P=0.89) ميان كلوني‌هاي مرجاني سالم و سفيد شده مشاهده نشد. يافته‌هاي اين تحقيق نشان دادند كه مشاهده عيني سفيدشدگي مي‌تواند به عنوان شاخصي براي تشخيص بيشينه آستانه تحمل مرجان‌ها به‌كار آيد و همچنين بررسي پويايي جمعيت اشكال مورفولوژيك مختلف زوگزانتلا مي‌تواند شاخصي براي تشخيص آغاز تنش ميزبان باشد. بنابراين ممكن است مرجان‌هاي جزيره قشم تحت تنش باشند و بسياري از آن‌ها، هرچند با ظاهر نرمال، در مراحل ابتدايي و مياني سفيدشدگي باشند.
چكيده لاتين :
The present study investigates the correlation between bleaching event and morphological condition and population dynamics of the symbiotic algae (zooxanthellae) residing within the hermatypic coral Acropora downingi Wallace, 1999 in Qeshm Island, Persian Gulf. Fragments of normal and bleached coral colonies were collected by SCUBA diving from southeastern coastal waters of Qeshm Island in the fall of 2015. Healthy, bleached, degraded and dividing zooxanthellae were observed and appraised with a light microscope using a haemocytometer. Spectrophotometric method was used for the measurement of pigment content of zooxanthellae. Comparisons of the mentioned characteristics between normal and bleached coral colonies showed a 50 percent population decline of zooxanthellae in bleached colonies. While density of normal zooxanthellae decreased by 25 percent in bleached colonies, number of bleached (t=7.03, P=0.00) and degraded (t=3.56, p=0.02) zooxanthellae along with mitotic index (z=-3/06, P=0.002) had a significant rise in the mentioned colonies. There was no significant difference between chlorophyll-α (t=0.49, P=0.63) and chlorophyll-c (t=0.13, P=0.89) content of the studied corals. Our results may reveal that corals in Qeshm Island are probably suffering from severe environmental conditions and it is likely that many of the healthy looking colonies are already half way through bleaching.
The present study investigates the correlation between bleaching event and morphological condition and population dynamics of the symbiotic algae (zooxanthellae) residing within the hermatypic coral Acropora downingi Wallace, 1999 in Qeshm Island, Persian Gulf. Fragments of normal and bleached coral colonies were collected by SCUBA diving from southeastern coastal waters of Qeshm Island in the fall of 2015. Healthy, bleached, degraded and dividing zooxanthellae were observed and appraised with a light microscope using a haemocytometer. Spectrophotometric method was used for the measurement of pigment content of zooxanthellae. Comparisons of the mentioned characteristics between normal and bleached coral colonies showed a 50 percent population decline of zooxanthellae in bleached colonies. While density of normal zooxanthellae decreased by 25 percent in bleached colonies, number of bleached (t=7.03, P=0.00) and degraded (t=3.56, p=0.02) zooxanthellae along with mitotic index (z=-3/06, P=0.002) had a significant rise in the mentioned colonies. There was no significant difference between chlorophyll-α (t=0.49, P=0.63) and chlorophyll-c (t=0.13, P=0.89) content of the studied corals. Our results may reveal that corals in Qeshm Island are probably suffering from severe environmental conditions and it is likely that many of the healthy looking colonies are already half way through bleaching.
The present study investigates the correlation between bleaching event and morphological condition and population dynamics of the symbiotic algae (zooxanthellae) residing within the hermatypic coral Acropora downingi Wallace, 1999 in Qeshm Island, Persian Gulf. Fragments of normal and bleached coral colonies were collected by SCUBA diving from southeastern coastal waters of Qeshm Island in the fall of 2015. Healthy, bleached, degraded and dividing zooxanthellae were observed and appraised with a light microscope using a haemocytometer. Spectrophotometric method was used for the measurement of pigment content of zooxanthellae. Comparisons of the mentioned characteristics between normal and bleached coral colonies showed a 50 percent population decline of zooxanthellae in bleached colonies. While density of normal zooxanthellae decreased by 25 percent in bleached colonies, number of bleached (t=7.03, P=0.00) and degraded (t=3.56, p=0.02) zooxanthellae along with mitotic index (z=-3/06, P=0.002) had a significant rise in the mentioned colonies. There was no significant difference between chlorophyll-α (t=0.49, P=0.63) and chlorophyll-c (t=0.13, P=0.89) content of the studied corals. Our results may reveal that corals in Qeshm Island are probably suffering from severe environmental conditions and it is likely that many of the healthy looking colonies are already half way through bleaching.
The present study investigates the correlation between bleaching event and morphological condition and population dynamics of the symbiotic algae (zooxanthellae) residing within the hermatypic coral Acropora downingi Wallace, 1999 in Qeshm Island, Persian Gulf. Fragments of normal and bleached coral colonies were collected by SCUBA diving from southeastern coastal waters of Qeshm Island in the fall of 2015. Healthy, bleached, degraded and dividing zooxanthellae were observed and appraised with a light microscope using a haemocytometer. Spectrophotometric method was used for the measurement of pigment content of zooxanthellae. Comparisons of the mentioned characteristics between normal and bleached coral colonies showed a 50 percent population decline of zooxanthellae in bleached colonies. While density of normal zooxanthellae decreased by 25 percent in bleached colonies, number of bleached (t=7.03, P=0.00) and degraded (t=3.56, p=0.02) zooxanthellae along with mitotic index (z=-3/06, P=0.002) had a significant rise in the mentioned colonies. There was no significant difference between chlorophyll-α (t=0.49, P=0.63) and chlorophyll-c (t=0.13, P=0.89) content of the studied corals. Our results may reveal that corals in Qeshm Island are probably suffering from severe environmental conditions and it is likely that many of the healthy looking colonies are already half way through bleaching.
