Oliver N. Ross

The role of cost–benefit analysis in models of phytoplankton growth and acclimation

Background: A key current issue in pelagic ecosystem modelling is obtaining better representations of the growth of phytoplankton so as to increase our understanding of the links between climate change and ocean biogeochemistry. Aims: Here we explore the use of cost-benefit analysis within the context of assessing the optimal distribution of resources for maximizing phytoplankton growth. Methods: We focus on capital and running costs by revisiting some of John Ravens cost-benefit analyses of chloroplast structure/function relations. Then, we describe a general framework for application of cost-benefit considerations in models of phytoplankton growth. Conclusions: Key to applying optimality criteria to phytoplankton growth models is quantifying the costs and benefits of alternative acclimation strategies. Costs include (1) capital costs of the structural and functional components of the cell, (2) running costs of CO2 fixation, nutrient acquisition, biosynthesis and repair, (3) opportunity costs for exploiting variability in the environment, and (4) taxes imposed by losses associated with transport to unfavourable environments, grazers and parasites. On short timescales of phytoplankton blooms, benefits can be assessed through influences on net growth rate, which can be increased by maximising resource gain (r-strategy) or minimizing losses (K-strategy). On longer timescales from years to millennia, the benefit is survival.

Hyperspectral remote sensing of phytoplankton assemblages in the ocean: Effects of the vertical distribution

The increasing availability of hyperspectral technology on remote sensing observing platforms provides marine scientists the potential to better map the phytoplankton community composition in the ocean globally. In this study, this approach is examined using unsupervised cluster techniques applied to data sets of hyperspectral remote sensing reflectance obtained by radiative simulations. Different oceanic environments in terms of phytoplankton biodiversity were satisfactorily classified. Furthermore, an assessment of the effect of a variable stratified water column scenario on the remote sensing reflectance points out that vertical distributions of phytoplankton communities along the water column play an essential role in the accurate phytoplankton assemblages mapping by remote sensing.

Comparing the use of hyperspectral Irradiance Reflectance and Diffuse Attenuation Coeficient as indicators for algal presence in the water column

Remarkable advances are being achieved on spectroradiometric systems technology, allowing the development of spectrometers aimed at in-situ measurements. However, the use of numerical modelling of the ocean optical properties can help to understand how these properties react to changes in the water columns composition. In this work, HydroLight-EcoLight was used in order to simulate different scenarios to study how two Apparent Optical Properties (AOPs) such as Irradiance Reflectance (R) and Diffuse Attenuation Coefficient (Kd) could be used to detect the presence of a specific phytoplankton group in the water column.