Light-Dependent Oxygen Cycling in Marine Systems Measured by 18o Tracer Techniques

Kana博士将讨论海水中“轻度呼吸”的一般问题。大量的直接和间接证据表明，光可以显著影响氧气的消耗：在某些情况下，光会使氧气的消耗速率提高到黑暗呼吸速率的10倍。从有机循环的角度来看，这种对氧气消耗的刺激意味着什么，由于历史上测量通量的困难，以及至少5个可区分的氧气吸收过程同时发生，人们对此知之甚少。卡纳博士的实验室最近发展了两种同位素(180)方法，能够测量光中的氧循环，为解决这一问题提供了基础。这项研究协调了河口栖息地依赖光的氧气摄取和演化的现场测量与从研究地点分离的浮游植物物种氧循环的对照实验室研究。感兴趣的主要变量是浮游植物组成，由季节周期定义，以及光照强度。现场实验的中心是描述季节性和事件尺度现象对氧气循环的影响，特别是在浮游植物的调节下。实验室实验的中心是识别与光相关的氧气摄取的生理过程。在一项相关的研究中，卡纳博士将继续与卡彭特和卡彭博士合作，研究毛霉的氧循环。

Dr. Kana will address the general question of "light respiration" in marine waters. Considerable direct and indirect evidence indicates that light can significantly affect oxygen consumption: in some cases elevating the rate up to 10 times the rate of dark respiration. What this stimulation of oxygen consumption means in terms of organic cycling is very poorly understood due to the historical difficulty in measuring the fluxes and the simultaneous occurance of at least 5 distinguishable oxygen uptake processes. Recent development in Dr. Kana's laboratory of two isotope (180) methods capable of measuring oxygen cycling in the light provide the basis for tackling this problem. The research coordinates field measurements of light-dependent oxygen uptake and evolution in an estuarine habitat with controlled laboratory studies of oxygen cycling in phytoplankton species isolated from the study site. The major variables of interest are phytoplankton composition, defined by seasonal cycles, and light intensity. Field experiments center around characterizing the effects of seasonal and event scale phenomena on oxygen cycling, especially as mediated by the phytoplankton. Laboratory experiments center around the identification of the physiological processes responsible for light-dependent oxygen uptake. In a related study, Dr. Kana will continue collaboration with Drs. Carpenter and Capone in the study of oxygen cycling in Trichodesmium.