Inorganic carbon turnover caused by digestion of carbonate sands and metabolic activity of holothurians

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• 作者：Kenneth Schneider ; Jacob Silverman ; Ben Kravitz ; Tanya Rivlin ; Aya Schneider-Mor ; Sergio Barbosa ; Maria Byrne ; Ken Caldeira
• 关键词：sea cucumbers ; CaCO3 dissolution ; respiration ; alkalinity ; DIC ; One Tree Reef
• 刊名：Estuarine, Coastal and Shelf Science
• 出版年：20 November, 2013
• 年：2013
• 卷：133
• 期：Complete
• 页码：217-223
• 全文大小：720 K

文摘

Recent measurements have shown that holothurians (sea cucumbers) may play an important role in the cycling of CaCO₃ in tropical coral reef systems through ingestion and processing of carbonate sediment. In this report, we present estimates of inorganic carbon turnover rates determined from laboratory incubations of Holothuria atra, Holothuria leucospilota and Stichopus herrmanni. The pH values of the gut lumen ranged from 7.0 to 7.6 when digestive tracts were filled with sediment compared with 6.1-6.7 in animals with empty digestive tracts. Empty gut volume estimates for H.聽atra and S.聽herrmanni were 36聽卤聽4聽mL and 151聽卤聽14聽mL, respectively. Based on these measurements and the density and porosity of carbonate sediments of coral reefs, it is estimated that these species process 19聽卤聽2聽kg and 80聽卤聽7聽kg CaCO₃聽sand聽yr^鈭? per individual, respectively. The annual CaCO₃ dissolution rates per H.聽atra and S.聽herrmanni individual are estimated to be 6.5聽卤聽1.9聽g and 9.6聽卤聽1.4聽g, respectively, suggesting that 0.05聽卤聽0.02% and 0.1聽卤聽0.02% of the CaCO₃ processed through their gut annually is dissolved. During incubations the CaCO₃ dissolution of the fecal casts was 0.07聽卤聽0.01%, 0.04聽卤聽0.01% and 0.21聽卤聽0.05% for H.聽atra, H. leucospilota and S.聽herrmanni, respectively. The CaCO₃ saturation state in the incubation seawater decreased markedly due to a greater increase in dissolved inorganic carbon (DIC) relative to total alkalinity (A_T) as a result of respiration by the animals. Our results support the hypothesis that deposit feeders such as sea cucumbers play an important ecological role in the coral reef CaCO₃ cycle.