Drobnitch Sarah Tepler, Nickols Kerry, Edwards Matthew
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, California, 95060, USA.
School of Natural Sciences, California State University, Monterey Bay, Seaside, California, 93955, USA.
J Phycol. 2017 Feb;53(1):85-94. doi: 10.1111/jpy.12480. Epub 2016 Nov 23.
In the Monterey Bay region of central California, the giant kelp Macrocystis pyrifera experiences broad fluctuations in wave forces, temperature, light availability, nutrient availability, and seawater carbonate chemistry, all of which may impact their productivity. In particular, current velocities and light intensity may strongly regulate the supply and demand of inorganic carbon (Ci) as substrates for photosynthesis. Macrocystis pyrifera can acquire and utilize both CO and bicarbonate (HCO ) as Ci substrates for photosynthesis and growth. Given the variability in carbon delivery (due to current velocities and varying [DIC]) and demand (in the form of saturating irradiance), we hypothesized that the proportion of CO and bicarbonate utilized is not constant for M. pyrifera, but a variable function of their fluctuating environment. We further hypothesized that populations acclimated to different wave exposure and irradiance habitats would display different patterns of bicarbonate uptake. To test these hypotheses, we carried out oxygen evolution trials in the laboratory to measure the proportion of bicarbonate utilized by M. pyrifera via external CA under an orthogonal cross of velocity, irradiance, and acclimation treatments. Our Monterey Bay populations of M. pyrifera exhibited proportionally higher external bicarbonate utilization in high irradiance and high flow velocity conditions than in sub-saturating irradiance or low flow velocity conditions. However, there was no significant difference in proportional bicarbonate use between deep blades and canopy blades, nor between individuals from wave-exposed versus wave-protected sites. This study contributes a new field-oriented perspective on the abiotic controls of carbon utilization physiology in macroalgae.
在加利福尼亚州中部的蒙特雷湾地区，巨型海带巨藻（Macrocystis pyrifera）会经历波浪力、温度、光照可用性、养分可用性和海水碳酸盐化学等方面的广泛波动，所有这些都可能影响它们的生产力。特别是，水流速度和光照强度可能会强烈调节作为光合作用底物的无机碳（Ci）的供应和需求。巨藻可以获取并利用二氧化碳（CO₂）和碳酸氢根（HCO₃⁻）作为光合作用和生长的Ci底物。鉴于碳输送（由于水流速度和溶解无机碳[DIC]的变化）和需求（以饱和辐照度的形式）的变异性，我们假设巨藻利用的CO₂和碳酸氢根的比例并非恒定不变，而是其波动环境的一个可变函数。我们进一步假设，适应不同波浪暴露程度和辐照度栖息地的种群会表现出不同的碳酸氢根吸收模式。为了验证这些假设，我们在实验室中进行了放氧试验，以测量在速度、辐照度和适应处理的正交交叉条件下，巨藻通过外部碳酸酐酶利用的碳酸氢根的比例。我们在蒙特雷湾的巨藻种群在高辐照度和高水流速度条件下，比在亚饱和辐照度或低水流速度条件下，表现出成比例更高的外部碳酸氢根利用率。然而，在深层叶片和冠层叶片之间，以及来自波浪暴露站点与波浪保护站点的个体之间，碳酸氢根使用比例没有显著差异。这项研究为大型藻类碳利用生理学的非生物控制提供了一个新的实地视角。
