Travis Meador
Scripps Institution of Oceanography
Geosciences Research Division
9500 Gilman Drive
La Jolla, CA 92093-0208
email: tmeador (at) ucsd (dot) edu
phone: 858-822-0988
CV:
For an alternative 'elevator conversation' click here
Life in the oceans began ~3.5 billion years ago and has since played a large part in shaping the Earth’s environment that we experience today. This is due to the enormity of the oceans, which cover 2/3 of the Earth’s surface and are up to 5000m deep! Marine life processes are thus directly tied to planetary chemistry and microorganisms that form the basis for life in the oceans are perhaps the most important for sustaining a hospitable environment for life on Earth.
Understanding the controls on marine microorganisms is thus of significant scientific interest. In the surface ocean for example, investigators have shown that the type of available nitrogen exerts a strong control on the community structure of photosynthesizing organisms. The marine nitrogen cycle represents a suite of interactions that can control and define ecosystems, having significant implications for ocean biodiversity and productivity. This is largely a result of the need for nitrogen in cellular biochemical processes. Both the structure and productivity of an ecosystem have important implications for the partitioning of carbon into various reservoirs and the oceans ability to store CO2. Therefore, understanding the relationship between N and C is central to predicting both the impacts of earth's biogeochemical processes on environmental conditions (e.g. global climate), and vice versa. 
In the surface ocean for example, investigators have shown that the type of available N exerts a strong control on the community structure of photosynthesizing organisms. Studies often focus on the availability of the inorganic forms of nitrogen such as nitrate and ammonia, but in large areas of the surface ocean, these chemical species are present at near-undetectable concentrations and the most available form of N is the dissolved organic nitrogen (DON) pool. Despite advances in chemical characterization and laboratory studies examining the importance of DON as a nutrient source for phytoplankton, the role of DON in the marine N cycle is still ambiguous. Another concern is to understand nitrogen trafficking in these areas of the ocean where inorganic N is scarce. In fact, the major input of new nitrogen into the world's oceans is thought to occur in exactly these oceanic environments where bacteria fix atmospheric nitrogen into their cells, thereby fertilizing the ocean (see the Trichodesmium bloom pitured from space to the left). N2-fixation may contribute as much as 50% of the total 'new' nitrogen entering the oligotrophic oceans (Karl et al. 1997), which constitute ~70% of ocean surface waters. However, the mechanisms by which this N is transferred to other photosynthesizing organisms and on to the rest of the ecosystem remains a mystery. Advancements in both of these pursuits have been hampered by the inability to observe manipulations of the DON pool and the failure to trace the fate of newly fixed N. 
The specific work in my thesis seeks to identify, characterize, and assess the bioavailability of the major components of the oceans' pool of DON, particularly those compounds contributed by nitrogen fixers. To begin to answer these questions I have both improved traditional bulk characterization methods and ventured beyond these to apply techniques new to the field of organic biogeochemistry, including various compound isolation methods, MALDI-MS, and gel electrophoresis. Also, I have generated a spatially comprehensive data set on the nitrogen isotope composition of marine DON, allowing for the first time a comparison of the extent of reactivity of various N reservoirs in the open ocean. These studies should help to define the importance of N2-fixation (and the physical oceanic conditions that promote this process) on carbon assimilation and distribution in the marine environment, and enhance our ability to recognize and predict the effect of both natural and anthropogenic perturbations to the environment. This study represents a new approach to our understanding of global nutrient cycles by attempting to identify and quantify molecular level processes that dominate marine ecosystems. Bridging the molecular component of ocean systems to global processes is a recent initiative in oceanography that promises to create avenues for defining and resolving human concerns about the environment; specifically, identifying the role of DON in the marine N cycle and food webs could have significant implications for understanding global carbon distribution and feedbacks on global climate. Furthermore, the ability to identify molecular components of the oceans' DON pool could promote the study of compound specific functions of DON in the marine environment such as metal chelation, selective preservation of organic compounds in the water column and sediments, and remote sensing of the onset of harmful algal blooms. This study has the capacity to expand our understanding of both the marine N and C cycles, the biocomplexity of ocean ecosystems (especially in relation to N2-fixation), and could provide a novel set of tools for identifying the role of specific biomolecules in the marine environment.
An Elevator Conversation
Elevator passenger: So why are you studying oceanography?
Travis: Oceanography is a science that draws from many disciplines, and is unique in its emphasis on field work (and much more fun!). The combined efforts of multi-disciplinary thinking and making measurements at sea has continued to reveal processes that sustain global health. Advancements in the understanding of global processes help to define the laws and boundaries that mankind constantly seeks to stretch and extend. It is important for the United States to actively monitor the effects of technological advances on the world we inhabit. This goal must be achieved in order to begin to address other advancements in our society. For example, during WWI Fritz Haber developed a technique using high temperatures and pressures to convert atmospheric nitrogen into ammonia gas. Although it first served as a method for making explosives, the Haber process was found highly applicable and valuable for agricultural purposes (i.e. FERTILIZER!!). It wasn’t until decades later that the adverse effects of nutrient loading on the environment were noticed. The radical changes in species composition and productivity of coastal ecosystems were not well understood, and are still being explained as scientists continue to unveil the dynamic processes that are involved in the onset of harmful algal blooms and eutrophication. Similarly, my research seeks to explore the cycling of nitrogen in the oceans and to further understand the dynamics of marine food webs. Our knowledge of these systems allows us to better recognize and predict the effect of both natural and anthropogenic perturbations to the environment.
