Giant clams (Subfamily Tridacninae), are important members of Indo-Pacific coral reefs, playing multiple roles in the framework of these communities. Although they are prominent species in Red Sea reefs, data on their distribution and densities in the region are scarce. The present study provides the first large-scale survey of Red Sea Tridacna spp. densities, where we examined a large proportion of the Saudi Arabian Red Sea coast (1,300 km; from 18° to 29°N). Overall, Tridacninae were found at densities of 0.19 ± 0.43 individuals m–2 (±SD). Out of the total 4,002 observed clams, the majority (89%) were Tridacna maxima, with 0.17 ± 0.37 individuals m–2, while only 11% were Tridacna squamosa clams with 0.02 ± 0.07 individuals m–2. We also report on a few (total 6) Tridacna squamosina specimens, found at a single reef. We identified different geographical parameters (i.e., latitude and distance to shore) and local environmental factors (i.e., depth and reef zone) as the main drivers for local Tridacna spp. densities. Our results show that the drivers influencing the densities of Red Sea giant clams are complex due to their co-occurrence and that this complexity might explain the high variation in Tridacninae abundances across the Indo-Pacific, but also within a given reef. We also estimate that giant clam calcification likely contributes to an average of 0.7%, but potentially up to 9%, of the overall mean calcium carbonate budget of Red Sea coral reef communities.

中文翻译：

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Tridacna spp 丰富的驱动因素。红海中的巨蛤

巨蛤（Tridacninae 亚科）是印度-太平洋珊瑚礁的重要成员，在这些群落的框架中发挥着多重作用。虽然它们是红海珊瑚礁中的重要物种，但关于它们在该地区的分布和密度的数据很少。本研究提供了对红海 Tridacna spp 的首次大规模调查。密度，我们在那里检查了沙特阿拉伯红海沿岸的大部分地区（1,300 公里；从 18° 到 29°N）。总体而言，在密度为 0.19 ± 0.43 个体 m–2 (±SD) 的情况下发现了砗磲亚科。在观察到的总共 4,002 只蛤中，大多数 (89%) 是砗磲，有 0.17 ± 0.37 个个体 m–2，而只有 11% 是砗磲蛤，有 0.02 ± 0.07 个个体 m–2。我们还报告了在单个珊瑚礁中发现的一些（总共 6 个）Tridacna squamosina 标本。我们确定了不同的地理参数（即纬度和到海岸的距离）和当地环境因素（即深度和珊瑚礁区）作为当地 Tridacna spp. 的主要驱动因素。密度。我们的研究结果表明，影响红海巨蛤密度的驱动因素由于它们的共同出现而很复杂，这种复杂性可能解释了整个印度洋 - 太平洋以及给定珊瑚礁内 Tridacninae 丰度的高度变化。我们还估计，巨蛤钙化可能占红海珊瑚礁群落总体平均碳酸钙预算的 0.7%，但可能高达 9%。我们的研究结果表明，影响红海巨蛤密度的驱动因素是复杂的，因为它们同时出现，这种复杂性可能解释了整个印度洋 - 太平洋以及给定珊瑚礁内 Tridacninae 丰度的高度变化。我们还估计，巨蛤钙化可能占红海珊瑚礁群落总体平均碳酸钙预算的 0.7%，但可能高达 9%。我们的研究结果表明，影响红海巨蛤密度的驱动因素是复杂的，因为它们同时出现，这种复杂性可能解释了整个印度洋 - 太平洋以及给定珊瑚礁内 Tridacninae 丰度的高度变化。我们还估计，巨蛤钙化可能占红海珊瑚礁群落总体平均碳酸钙预算的 0.7%，但可能高达 9%。