Jim received his PhD in Oceanography from the University of Hawaii.  After receiving his degree in 2002, he worked as an Assistant Researcher at the Hawaii Institute of Marine Biology before moving to School of Earth and Environment at the University of Western Australia a year ago where he currently works as a Research Assistant Professor.  His current research is focused on how the growth and metabolism of benthic marine communities respond to changes in their physical and chemical environment.  His ultimate goal is to understand how large-scale climatic variability influences the dynamics of growth and material exchange at the community and ecosystem scales using a combination of targeted mesocosm experiments, field observations, and numerical hydrodynamic-biogeochemical models.

ABSTRACT:

Rates of growth and metabolism in coral reef communities are ultimately constrained by principles of thermodynamics and mechanics.  In shallow reef communities, gross rates of carbon fixation are set by limits to the efficiency of light transformation whereas rates of nutrient uptake are dictated by the limits of convective mass transfer across concentration boundary layers.  Under conditions of mass transfer limitation, rates of nutrient uptake are first-order with respect to water column concentrations where the first-order rate constants are defined by the mass transfer coefficient (m d-1).  In algal-dominated communities, Net Primary Production (mmol C m-2 d-1) represents the aggregate growth of the entire benthic primary producer community and is determined by two important factors: 1) the rate of nutrient supply to the community, and 2) the elemental stoichiometry of plant growth (i.e., community C:N:P). The large variation in C:N:P in marine algae with location and taxa, along with prior evidence from other marine primary producer communities, indicate the potential for reef algal communities to adjust their elemental composition in response to differential forcing by light, water chemistry, and water motion.  Recent work in Hawaii, however, shows little seasonal adjustment of community C:N:P to differential forcing by light and convective mass transfer indicating that such variations may be more prominent at other spatial and temporal scales.  In coral-dominated communities, the formation of mineral biomass via calcification (mmol CaCO3 m-2 d-1) rather than net organic production best represents the aggregate growth of the community.  Although the dominant variables driving calcification appear to be light and aragonite saturation state, the role that nutrient loading plays in influencing rates of calcification still remains unclear.  Coral-dominated communities at Ningaloo exhibit high rates of production and calcification under high rates of nutrient loading that are, in turn, subject to temporal variation in the composition of offshore waters.