Collaborative Reseach: Nitrogen Limitation and Ultraviolet Stress in Marine Macroalgae

众所周知，光、温度和营养物质的可用性等物理因素限制了海洋生产力，并在决定物种分布和群落结构方面发挥着重要作用。大多数对物理因素的作用的理解是基于对单个变量的研究，而其他条件对生长是优化的。因此，几乎没有关于自然环境的生理反应的信息，在自然环境中，几个物理因素可能是次优的。要了解对海洋生产力的制约，不仅需要了解潜在的协同或拮抗相互作用，而且还需要分析它们对不同生态策略的藻类的影响。本研究将考察海洋红藻对同时存在的氮素限制和紫外线胁迫的响应。众所周知，这两个因素都是海洋初级生产力的重要决定因素，它们经常同时出现。不仅热带地区如此，像缅因湾这样的寒温带海洋也是如此。之所以选择红藻进行这项研究，是因为它们为研究紫外线和氮素限制之间的相互作用提供了机会，这些藻类具有相似的生理和形态特征，但在紫外线耐受性和类霉菌素类氨基酸含量方面存在明确的差异。此外，与浮游植物相比，底栖大型藻类经历了更可预测的光照气候，并且相对较长的寿命，使个人暴露在更广泛的环境条件下。来自缅因湾的红藻研究将包括脐带紫菜、角叉菜、膜翅目和藻类。这些物种的范围从耐紫外线的潮间带和浅潮下物种到较深的潮下对紫外线敏感的物种。研究人员预计，耐紫外线和限制氮素的影响的成本和收益将在耐紫外线和敏感紫外线的物种之间有所不同。研究将集中于氮代谢(有限或完全)对(A)紫外线胁迫的短期和长期影响(例如，光合作用、脂质过氧化和生长的短期抑制)、(B)紫外线光保护，包括防晒霜(如霉菌素样氨基酸(MAAs))、抗氧化剂(如抗坏血酸、谷硫酮和生育酚)以及活性氧代谢酶(如过氧化氢酶、超氧化物歧化酶和抗坏血酸过氧化物酶)的影响，以及(C)从紫外线胁迫中恢复的能力(例如，蛋白质合成在恢复中的作用)。这项研究还将研究紫外线胁迫对氮代谢的影响(例如，氮含量以及吸收和同化速率)。这项研究将包括现场收集的材料的测量，在受控条件下的实验室实验，以及由各种紫外线和光合作用有效辐射(PAR)过滤器操纵的流动海水和自然辐射的室外实验。这项研究将大大有助于理解紫外线和无机氮的有效性对海洋生产力的影响，特别是阐明这些因素之间相互作用的重要性。这项研究涉及本科生教学机构(马萨诸塞州韦斯特菲尔德州立学院)和陆地和海洋赠款研究大学(缅因州大学)的教职员工之间的合作。除了研究生教育，该项目还拥有丰富的本科生研究经验，为韦斯特菲尔德州立学院的本科生提供了参与研究的机会。

Davison - 9907305Physical factors such as light, temperature and nutrient availability are known to limit marine productivity and play an important role in determining species distribution and community structure. Most understanding of the role of physical factors is based on studies with a single variable with other conditions being optimized for growth. Consequently, little information is available on physiological responses to the natural environment where several physical factors may be suboptimal. The ability to understand the constraints on marine productivity requires not only an understanding of potential synergistic or antagonistic interactions but also an analysis of their effects on algae with different ecological strategies. This investigation will examine the response of marine red macroalgae to simultaneous nitrogen limitation and ultraviolet radiation stress. Both factors are known to be important determinants of marine primary productivity and they frequently co-occur. This is true not only of the tropics, but also in cold- temperate oceans such as the Gulf of Maine. Red macroalgae were selected for this research because they provide the opportunity to study interactions between UV and nitrogen limitation in a group of algae with similar physiological and morphological characteristics but with well-defined differences in UV-tolerance and well-characterized contents of mycosporine-like amino acids. Furthermore, in contrast to phytoplankton, benthic macroalgae experience a more predictable light climate and are relatively long-lived, exposing individuals to a wider range of environmental conditions. The red algae studied from the Gulf of Maine will include Porphyra umbilicalis, Chondrus crispus, Membranoptera alata and Phycodry rubens. These species range from UV-tolerant intertidal and shallow sublittoral species to UV-susceptible species from the deeper sublittoral. The investigators anticipate that the costs and benefits of UV-tolerance and the impact of nitrogen limitation will vary between UV-tolerant and UV-susceptible species. The research will focus on the effect of nitrogen metabolism (limited or replete) on (a) short and long-term effects of UV-stress (e.g., short-tem inhibition of photosynthesis, lipid peroxidation, and growth), (b) UV-photoprotection including contents of sunscreens such as mycosporine-like amino acids (MAAs), antioxidants such as ascorbate, gluathione and tocopherols, and enzymes of reactive oxygen metabolism such as catalase, superoxide dismutase and ascorbate peroxidase, and (c) ability to recover from UV-stress (e.g., the role of protein synthesis in recovery). The research will also examine the effect of UV-stress on nitrogen metabolism (e.g., nitrogen content and rates of uptake and assimilation). The research will involve measurements on field-collected material, laboratory experiments under controlled conditions and outdoor experiments in flowing seawater and natural radiation manipulated by a variety of UV and photosynthetically active radiation (PAR)-filters. The research will substantially contribute to an understanding of the effect of UV and inorganic nitrogen availability on marine productivity and, in particular, elucidate the importance of interactions between these factors. The research involves collaboration between faculty at an undergraduate teaching institution (Westfield State College, MA) and a Land and Sea Grant research University (University of Maine). In addition to graduate education, the project has a substantial research experience for undergraduate component, providing undergraduates from Westfield State College with the opportunity to become involved in research.