Photosynthetic Performance of Laminaria Solidungula and L. Saccharina in the High Arctic: Adaptation to Very Low Light Levels Under Winter Ice

海带的巨大和快速生长至少部分是由于， 它们在各种光照下优化生长的能力 通过改变光合性能的条件。 这 一种北极物种海带的特征可能最为显著 solidungula，使其年产量增加超过 当辐射水平达到100000000时， 最低。 报告的开放水域饱和辐照度， 发生在夏季，一个最小的增长期，当 溶解无机氮（DIN）浓度最低。 该项目将检验光合作用 敏感性L。solidungula增加相当大的期间， 覆冰期，环境DIN增加，而不是降低 辐射水平，主要负责季节性 植物光合作用的变化。 几 光合参数将从光合作用计算 从放射性碳吸收导出的辐照度（P-I）曲线 和氧通量测量，以及光捕获 在博福特中原位培养的整株植物的特征 海 在实验室中， 在不同的光照和DIN条件下， 期间将进行比较，以具体解决这些作用 在低光照水平下调节冬季光合作用的因素。 此外，还研究了L.糖精， 在温带地区很常见，但在 阿拉斯加中部博福特海，将与L. 实心有蹄类。 两种植物的光合作用研究 光照和养分限制的自然条件将增强 我们对光适应的理解， 我们能够通过测量精确地模拟海带产量 of in situ原位irradiance辐照.

The large size and rapid growth of kelp is due, at least in part, to their ability to optimize growth under a variety of light conditions through changes in photosynthetic performance. This feature may be most pronounce in one arctic species, Laminaria solidungula, which increases its annual production by more than half over 8-months of continuous ice cover when irradiance levels are lowest. Reported open-water saturation irradiance in this occurs during the summer, a period of minimal growth, when dissolved inorganic nitrogen (DIN) concentrations are lowest. The project will test the hypothesis that photosynthetic sensitivity in L. solidungula increases considerably during the ice-covered period, and that ambient increases in DIN, not low levels of irradiance, are primarily responsible for seasonal changes in the plant's photosynthetic performance. Several photosynthetic parameters will be calculated from photosynthetic irradiance (P-I) curves derived from radioactive carbon uptake and oxygen flux measurements, and the light harvesting characteristics of entire plants incubated in situ in Beaufort Sea. In the lab, photosynthetic parameters of individuals grown under different conditions of light and DIN over a four-month period will be compared to specifically address the role of these factors in regulating winter photosynthesis at low light levels. In addition, the photosynthetic response of L. saccharina, which is common in temperate regions but is relatively rare in the central Alaskan Beaufort Sea, will be compared to that of L. solidungula. Studies of photosynthesis in both species under natural conditions of light and nutrient limitation will enhance our understanding of photoadaptation and will greatly improve our ability to accurately model kelp production from measurements of in situ irradiance.