During feeding, echinoids remove a large proportion of calcium carbonate in addition to the algae growing on dead coral and are consequently of importance in estimating the turnover of organic and inorganic carbon in coral reefs. Rates of herbivory and the erosion of dead coral substratum, referred to as bioerosion, by the most abundant echinoid species in Kenyan reefs, Echinothrix diadema (Linnaeus), Diadema setosum (Leske), D. savignyi (Michelin) and Echinometra mathaei (de Blainville), were compared in three different reef categories with different histories of fishing and its exclusion. These were reefs: (i) protected within Marine National Parks, which exclude all forms of fishing, coral and shell collection for more than 25 years; (ii) one reef within a Marine Park, which has received protection from fishing activities for 8 years (referred to as 'newly protected' reef); and (iii) unprotected reefs, which experience heavy fishing and some coral collection. The aim was to investigate the grazing and bioerosion activity by the above echinoid species in these reef categories. We surveyed sea urchin population densities and determined their rates of bioerosion and herbivory per individual and square meter. Individual rates of bioerosion and herbivory, of the species D. setosum, D. savignyi and E. diadema were estimated from laboratory gut content analysis and gut evacuation experiments in the field, using elevated underwater cages. Individual rates of bioerosion and herbivory of E. mathaei were obtained from a previous field study [J. Exp. Mar. Biol. Ecol. 147 (1991) 121]. Sea urchin bioerosion was greater than herbivory for all studied species and proportional to the body size of the sea urchin species. The large-bodied E. diadema exhibited the highest bioerosion and herbivory rates (5.5+/-0.9 and 2.2+/-0.3 g individual(-1) day(-1), respectively) followed by D. setosum (1.8+/-0.3 and 1.1+/-0.2 g individual(-1) day(-1)) and D. savignyi (0.7+/-0.2 and 0.4+/-0.1 g individual(-1) day(-1)). Highest sea urchin densities were recorded at unprotected reefs (6.2+/-1.5 individual m(-2)), and therefore, bioerosion and herbivory by sea urchins were also highest in this reef category (1180+/-230 g CaCO(3) m(-2) year(-1) and 450+/-77 g algae m(-2) year(-1)). Protected reefs recorded 20 times lower sea urchin bioerosion and herbivory rates (50.3+/-25.8 g CaCO(3) m(-2) year(-1) and 20.7+/-10.4 g algae m(-2) year(-1)), due to the low sea urchin population densities in these reefs (0.06+/-0.01 individual m(-2)). The newly protected reef, with intermediate number of sea urchins (1.2+/-0.1 individual m(-2)), had intermediate rates of sea urchin bioerosion and herbivory (711+/-157 g CaCO(3) m(-2) year(-1) and 299+/-63 g algae m(-2) year(-1)). These findings suggest that echinoids are important in the carbon cycle and reef development, and that fishing can influence these ecological processes.

中文翻译：

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肯尼亚珊瑚礁上的海胆生物侵蚀和食草动物：防止捕鱼的作用

在摄食过程中，海胆除了去除死珊瑚上生长的藻类外，还会去除大部分碳酸钙，因此在估计珊瑚礁中有机和无机碳的周转率方面具有重要意义。肯尼亚珊瑚礁中最丰富的海胆类物种 Echinothrix diadema (Linnaeus)、Diadema setosum (Leske)、D. savinyyi (Michelin) 和 Echinometra mathaei (de Blainville) 的食草率和死珊瑚基​​质的侵蚀，称为生物侵蚀)，在三个不同的珊瑚礁类别中进行了比较，这些珊瑚礁类别具有不同的捕鱼历史和排除历史。这些是珊瑚礁： (i) 在海洋国家公园内受到保护，禁止所有形式的捕鱼、珊瑚和贝类采集超过 25 年；(ii) 海洋公园内的一处礁石，已获得 8 年禁止捕鱼活动的保护（称为“新保护”珊瑚礁）；(iii) 未受保护的珊瑚礁，经历了大量捕捞和一些珊瑚收集。目的是研究这些珊瑚礁类别中上述海胆类物种的放牧和生物侵蚀活动。我们调查了海胆的种群密度，并确定了它们每个体和每平方米的生物侵蚀和食草率。使用高架水下网箱，通过实验室肠道内容分析和田间肠道疏散实验，估计了 D. setosum、D. savigniyi 和 E. diadema 物种的个体生物侵蚀和食草率。E. mathaei 的个体生物侵蚀和食草率是从先前的实地研究中获得的 [J. 经验。三月生物。生态。147 (1991) 121]。对于所有研究的物种，海胆的生物侵蚀大于食草动物，并且与海胆物种的体型成正比。大体 E. diadema 表现出最高的生物侵蚀和食草率（分别为 5.5+/-0.9 和 2.2+/-0.3 g 个体（-1）天（-1）），其次是 D. setosum（1.8+/- 0.3 和 1.1+/-0.2 克个体 (-1) 天 (-1)) 和 D. savignyi（0.7+/-0.2 和 0.4+/-0.1 克个体（-1）天（-1））。在未受保护的珊瑚礁中记录了最高的海胆密度（6.2+/-1.5 个个体 m(-2)），因此，海胆的生物侵蚀和食草在该珊瑚礁类别中也是最高的（1180+/-230 克 CaCO(3) m(-2) 年 (-1) 和 450+/-77 克藻类 m(-2) 年 (-1))。受保护的珊瑚礁记录的海胆生物侵蚀和食草率降低 20 倍（50.3+/-25.8 g CaCO(3) m(-2) year(-1) 和 20.7+/-10.4 g 藻类 m(-2) year(-1) )), 由于这些珊瑚礁中的海胆种群密度较低（0.06+/-0.01 个体 m(-2)）。新保护的珊瑚礁，具有中等数量的海胆（1.2+/-0.1 个体 m(-2)），具有中等海胆生物侵蚀和食草率 (711+/-157 g CaCO(3) m(-2)年（-1）和 299+/-63 克藻类 m（-2）年（-1））。这些发现表明，海胆在碳循环和珊瑚礁发育中很重要，捕鱼可以影响这些生态过程。