Quantifying contributors to light attenuation is useful for the management of seagrass meadows. Epiphytic growth on seagrasses can lead to diminished light for the host plant, impairing photosynthesis and growth. Here, we quantify the contributions of the water column and epiphytic load to light attenuation in a Cymodocea rotundata meadow at Chek Jawa, Singapore. Using a modified spectrometer and seagrass mimics (clear polyethene strips) colonised by epiphytes, we determined the relationship between light transmission (400–700 nm) and epiphyte load. Subsequently, we derived the percentage of surface light that reaches the leaf surface (PLL) over a range of epiphyte biomass and water-column light-attenuation coefficients (Kd). Results indicated that the relative contribution to light attenuation by epiphytic biomass was greater in clearer waters (Kd < 0.5) than in turbid waters. As Kd increases, the amount of epiphytic material required to reduce PLL to minimum light requirement (11%) decreases exponentially. At Chek Jawa, the average epiphytic load was 32 mg DW cm−2, which was close to the estimated amount (33 mg DW cm−2) required to reduce PLL to 11% at prevailing turbidity levels. Our findings suggest that high epiphyte load is benign in clear waters, but becomes critical in turbid waters.

中文翻译：

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附生植物负荷对海草叶片光衰减的贡献很小，但在混浊水域中至关重要

量化光衰减的因素对于海草草地的管理很有用。海草上的附生生长会导致寄主植物的光照减弱，从而损害光合作用和生长。在这里，我们量化了新加坡 Chek Jawa 的 Cymodocea rotundata 草甸中水柱和附生负载对光衰减的贡献。使用改进的光谱仪和附生植物定植的海草模拟物（透明聚乙烯条），我们确定了光透射（400-700 nm）和附生植物负载之间的关系。随后，我们得出了在一定范围的附生植物生物量和水柱光衰减系数 (Kd) 内到达叶面 (PLL) 的表面光的百分比。结果表明，在较清澈的水域（Kd < 0.5）中，附生生物量对光衰减的相对贡献比在浑浊的水域中更大。随着 Kd 的增加，将 PLL 降低到最低光照要求 (11%) 所需的附生物质数量呈指数下降。在 Chek Jawa，平均附生负载为 32 mg DW cm-2，这接近在主要浊度水平下将 PLL 降低至 11% 所需的估计量（33 mg DW cm-2）。我们的研究结果表明，高附生植物负载在清澈的水中是良性的，但在浑浊的水中变得至关重要。这接近在主要浊度水平下将 PLL 降低到 11% 所需的估计量（33 mg DW cm-2）。我们的研究结果表明，高附生植物负载在清澈的水中是良性的，但在浑浊的水中变得至关重要。这接近在主要浊度水平下将 PLL 降低到 11% 所需的估计量（33 mg DW cm-2）。我们的研究结果表明，高附生植物负载在清澈的水中是良性的，但在浑浊的水中变得至关重要。