Marine Biology

fa بررسی ارتباط پدیده سفید شدگی با خصوصیات مورفولوژیک و پویایی جمعیت جلبک همزیست با مرجان سختAcropora downingi Wallace, 1999 در جزیره قشم The correlation between bleaching and morphological condition and population dynamics of symbiotic algae with Acropora downingi Wallace, 1999 in Qeshm Island شیلات Fisheries پژوهشي Research در این مطالعه وجود تنش در مرجان‌های گونه Wallace, 1999 Acropora downingi با مقایسه خصوصیات مورفولوژیک و پویایی‌جمعیت جلبک همزیست آن‌ها (زوگزانتلا) در کلونی‌های نرمال و سفید شده در جزیره قشم مورد بررسی قرار گرفت. کلونی‌های نرمال و سفیدشده مرجان در پاییز 1394 طی عملیات غواصی از جنوب شرقی جزیره قشم جمع‌آوری شدند. شکل‌های مختلف زوگزانتلا (سالم، رنگ‌پریده، تخریب شده و درحال تقسیم) زیر میکروسکوپ نوری مورد بررسی قرار گرفت و توسط لام هموسیتومتر شمارش گردید. همچنین غلظت رنگدانه‌های کلروفیل α و c توسط روش اسپکتروفتومتری بدست آمد و میزان تمامی متغیرها بین کلونی‌های سالم مرجانی و کلونی‌هایی که در اثر تنش سفید شده بودند، مقایسه شد. نتایج نشان داد که تراکم زوگزانتلا بطور کلی در کلونی مرجانی سفید شده 32 درصد نسبت به کلونی نرمال کاهش یافته است. در این میان تراکم زوگزانتلا‌های سالم 25 درصد در کلونی تحت تنش کاهش یافته و برعکس به طور معناداری تراکم زوگزانتلا‌های رنگ‌پریده (t=7.03, P=0.00) و تخریب شده (t=3.56, p=0.02) در کلونی مرجان تحت تنش نسبت به کلونی سالم افزایش داشته است. همچنین ضریب میتوزی در کلونی‌های مرجانی سفیدشده افزایش معناداری نسبت به کلونی‌های سالم داشت (z=-3/06, P=0.002). هرچند اختلاف معناداری در میزان رنگدانه‌های کلروفیل α (t=0.49, P=0.63) و کلروفیل c (t=0.13, P=0.89) میان کلونی‌های مرجانی سالم و سفید شده مشاهده نشد. یافته‌های این تحقیق نشان دادند که مشاهده عینی سفیدشدگی می‌تواند به عنوان شاخصی برای تشخیص بیشینه آستانه تحمل مرجان‌ها به‌کار آید و همچنین بررسی پویایی جمعیت اشکال مورفولوژیک مختلف زوگزانتلا می‌تواند شاخصی برای تشخیص آغاز تنش میزبان باشد. بنابراین ممکن است مرجان‌های جزیره قشم تحت تنش باشند و بسیاری از آن‌ها، هرچند با ظاهر نرمال، در مراحل ابتدایی و میانی سفیدشدگی باشند. 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. <div>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.</div> زوگزانتلا, سفید شدگی, ضریب میتوزی, رنگدانه, خلیج فارس, جزیره قشم. Zooxanthellae, Bleaching, Mitotic Index, Pigment, Persian Gulf, Qeshm Island 1 10 http://jmb.ahvaz.iau.ir/browse.php?a_code=A-10-400-2&slc_lang=fa&sid=1 مهشید اولادی کلاریجانی 10031947532846004352 10031947532846004352 No محمدرضا شکری 10031947532846004353 10031947532846004353 Yes حسن رجبی مهام 10031947532846004354 10031947532846004354 No