Solar energy capture and transformation in the sea

Abstract

Ecological energy flowSolar energy ultimately drives all biogeochemical cycles and sustains planetary habitability. All life forms and processes on Earth, including human economic and social systems, exist within a complex network of energy flow. In the sea, microorganisms comprise most of the genetic and metabolic diversity, and are responsible for a majority of the system energy flow including solar energy capture, transformation, and dissipation. All of these processes involve conversion of low quality forms of energy into a smaller fraction of higher quality energy plus degraded heat, in accordance with the basic laws of thermodynamics. Energy flow is at the core of ecosystem analysis (Odum 1968).Sunlight is the most abundant form of energy for marine microorganisms, and biophysical/biochemical mechanisms for solar energy capture have evolved by natural selection during eons of Earth's history (Brown and Ulgiati 2004;Nealson and Rye 2003). Marine ecosystems, especially the expansive subtropical gyres, have an enormous capacity for solar energy capture and transformation. Ecologists often use the term "carbon and energy flow" to describe solar energy capture, organic matter transformation, and heat dissipation through the food web via the coupled processes of photosynthesis and respiration. A number of different methods have been used to track the flow of carbon and associated bioelements (e.g., nitrogen, phosphorus, oxygen, and sulfur), but energy flow is rarely if ever measured in field studies. An untested assumption is that matter and energy flow are inextricably and quantitatively linked in space and time in the open sea.Howard T. Odum, largely in collaboration with his brother Eugene P. Odum, pioneered the discipline of systems ecology. He observed and studied a variety of aquatic ecosystems and was the first to characterize them as networks of energy circuits (e.g., Silver Springs, Florida; Odum 1956). Odum later developed an explicit energy circuit language and set of symbols that could be used to represent interactive energy capture, transformation, and dissipation in both natural and manmade systems (Odum 1983a). While some scientists have criticized "Odum's conjectures" and his energy-centric approach to the study of ecosystems (e.g., Månsson and McGlade 1993), the debate centers on the formidable obstacles to a comprehensive, quantitative analysis and understanding of ecological energy flow rather than a challenge to its fundamental importance in ecosystem analysis.In a pioneering essay on the relationship of energy flow to evolution, Alfred Lotka concluded that natural selection will operate to preserve and expand those species "possessing superior energy-capturing and directing devices" (Lotka 1922). Consequently, he reasoned, as long as there is a residue of untapped available energy, "the total organic mass of the system, the rate of circulation of mass through the system, and the total energy flux" will be maximized. This reasoning has since become known as the maximum power principle (Odum a...

Ecosystem Structure and Dynamics in the North Pacific Subtropical Gyre: New Views of an Old Ocean

“…These new pathways of solar energy capture, aerobic anoxygenic phototrophy others 2000, 2001) and proteorhodopsin phototrophy (Bé jà andothers 2000, 2001), are most likely facultative mechanisms to supplement the energy demands and to improve the growth rates/efficiencies of otherwise obligate chemoorganoheterotrophic metabolisms in select marine bacteria and archaea. These profound discoveries could fundamentally alter our views of life in the sea, but we currently lack a quantitative understanding of the rates, controls and ecological significance of these alternate energy capture pathways in nature (Karl 2007(Karl , 2014b.…”

Peruvian upwelling plankton respiration: calculations of carbon flux, nutrient retention efficiency, and heterotrophic energy production

“…3a) that occurs on the sea floor. Finally, we use the respiration models and the coupling between ETS activity and oxidative phosphorylation to calculate light-independent heterotrophic energy flow (Karl, 2014). This energy is generated in the form of ATP by ATP synthase, an enzyme motor coupled to a heterotrophic respiratory process such as O 2 utilization or NO − 3 reduction (Watt et al, 2010;Ferguson, 2010).…”

“…A generation later, Odum built on this concept to describe energy flow in freshwater streams (Odum, 1956). Reviewing this earlier work, Karl recently argued that biological energy production in the ocean should be assessed to provide insight into the variability of ocean productivity (Karl, 2014). Here, we address his concern by calculating Heterotrophic energy production (HEP) in a C-line section (Fig.…”

“…However, until now, calculations of biological energy production (shown in Fig. 2d), including HEP, in the ocean had not been made (Karl, 2014). Now the time is appropriate to make such calculations with recent research (Lane, 2002(Lane, , 2005(Lane, , 2009Wilson et al, 2012;Chen and Strous, 2013), documenting the ubiquity of respiratory ETS in the biosphere, how it relates to R O 2 , to all other ocean respiratory processes, and to HEP as ATP production.…”

Microbial metabolic rates in the Ross Sea: the ABIOCLEAR Project

“…Building on this concept, Howard Odum described energy flow in freshwater streams (Odum 1956). David Karl recently argued that biological energy production in the ocean should be assessed to understand ocean productivity better (Karl 2014).…”