The physiological and ecological functions of volatile halogen production by marine diatoms

海洋是卤素的主要储存库，包括以卤化物离子形式存在的氯、溴和碘。各种生物和化学反应将卤化物转化为挥发性卤素，这些卤素可以穿过海面进入大气。海洋环境中产生的挥发性卤素包括CH2I2和CH2BrI等有机化合物以及I2和Br2等活性无机物质。卤素一旦进入大气，就会参与臭氧循环，影响云的形成。海洋中有机和无机挥发性卤素的主要来源是一种被称为硅藻的浮游植物群，它们生活在开阔水域和海冰中。虽然实验表明硅藻会产生挥发性卤素，但我们不明白它们为什么会这样做，也不明白它会如何影响周围的其他生物。一种说法是，硅藻产生挥发性卤素是为了保护自己免受活性氧的伤害，另一种说法是，它们这样做是为了保护自己免受其他微生物或食草无脊椎动物的伤害。重要的是，我们要了解硅藻产生挥发性卤素的原因，以便我们知道卤素从海洋排放到大气的时间和地点，并能够预测气候变化将如何影响这一点。这对于正在经历快速变暖的极地地区尤其重要，在那里已经看到了气候引起的硅藻群落变化。在这项研究中，我将进行实验室实验，以探索挥发性卤素的产生是否有助于保护硅藻免受氧化应激，以及这是否对周围海水中细菌的丰度或组成有任何影响。这将使我能够建立数学关系来描述在细菌存在下硅藻产生的挥发性卤素。这些关系将允许开发海水中挥发性卤素产生的计算机模型，这将告诉我们卤素排放在未来将如何变化以及这将如何影响大气化学。

The oceans are a major reservoir of halogens including chlorine, bromine and iodine in the form of halide ions. Various biological and chemical reactions convert the halides to volatile halogen species which can move across the sea surface and into the atmosphere. The volatile halogens produced in the marine environment include organic compounds like CH2I2 and CH2BrI and reactive inorganic species like I2 and Br2. Once in the atmosphere the halogens are involved in ozone cycling and can influence the formation of clouds. A major source of organic and inorganic volatile halogens in the oceans is a phytoplankton group known as diatoms which live in open waters and in sea-ice. While experiments have shown that diatoms produce volatile halogens we do not understand why they do this or how it might impact other organisms around them. One idea is that diatoms produce volatile halogens to protect themselves against damage from reactive oxygen species and another is that they do this to defend themselves against other microbes or grazing invertebrates. It is important that we understand the reasons why diatoms produce the volatile halogens so we known when and where halogen emissions from the oceans to the atmosphere will take place and are able to predict how climate change will influence this. This is especially crucial for polar regions experiencing rapid warming where climate-induced changes in diatom communities have already been seen. In this study I will carry out laboratory experiments to explore if volatile halogen production helps to protect the diatoms from oxidative stress and if this has any impact on the abundance or composition of bacteria in the seawater around them. This will allow me to produce mathematical relationships that describe volatile halogen production by diatoms in the presence of bacteria. These relationships will allow computer models of volatile halogen production in seawater to be developed which will tell us how halogen emissions will change in the future and how this will impact atmospheric chemistry.