About project

Modern civilisation relies heavily on two sources of energy from living resources: newly produced plant biomass and fossil fuel produced from preserved biomass. The first source is renewable and relies on the Sun; the second one is finite.One might add that a small portion of the renewable biomass serves as food, sustaining all animal populations, including humankind. With the economy not yet fully decoupled from carbon, emissions tend to rise along with the economy. As present the total global emissions are around 10 Gt of carbon per year (Friedlingstein, et al., 2020), one half of which ends up in the atmosphere, one quarter on land and one quarter in the oceans. For comparison, the total global uptake of carbon in photosynthesis (primary production), both on land and sea, is 100 Gt of carbon per year (Field et al., 1998). Therefore, for the first time in human historyanthropogenic carbon emissions are just an order of magnitude lower than the productivity of the Earth’s biosphere (Lenton & Watson, 2014).

This productivity is split equally amongst the terrestrial and the ocean ecosystems, each being around 50 Gt of carbon per year. Around 8% of global annual marine primary production sustains global fisheries (Pauly & Christensen, 1995). However, the carbon biomass of the biosphere itself is unequally split, with the ocean autotrophic biomass, mostly composed of phytoplankton, being a meagre 1% in comparison to the terrestrial biomass (Bar-On et al., 2018). Having comparable productivity, with such a sharp contrast in biomass, is only possible due to phytoplankton having a rapid turnover time, on the order of weeks, with land biomass having a turnover time on the order of years (Carvalhais et al., 2014). This rapid response of phytoplankton to external stress makes phytoplanktona good indicator of ocean climate change, due to its rapid response to external stressors.

Consequences of changes in ecosystem functioning have socio-economic repercussions: crashes of Peruvian anchoveta and of cod in Canada serve as stark reminders of the interplay between the ocean biota and the economy. On a global scale, the socioeconomic value of the ocean ecosystem has been estimated at 21 trillion US dollars per year (Costanza et al., 1997). Future value of ocean ecosystems services is uncertain, and its quantification is becoming increasingly important due to threats posed by climate change. Climate tipping points, critical thresholds after which perturbations irreversibly alter the dynamics of the system, are considered one of the biggest threats ocean ecosystems face (Lenton et al., 2008). Whereas physical tipping points in the ocean have been explored for some time now (Stommel, 1961; Weijer et al., 2019), the tipping points in marine ecosystems have been studied only sporadically (Heinze et al., 2021). In fact, the stability of phytoplankton photosynthesis, the base of the marine food web, as a productive system has been taken for granted and has not been questioned even on a theoretical basis, although numerous studies on climate change and phytoplankton have been published: Hays (2005), Falkowski & Raven, (2007), Boyce et al. (2010), to name a few.

There is now a rich body of knowledge on bio-optical models of marine photosynthesis and the field can be said to have come of age. A straightforward application of such models is the estimation of global scale primary production that is carried out using remote sensing and in situ data merged in state of the art models. Efforts to forecast likely changes in global primary production over the next century using simulation models have yielded results with large uncertainties (Frolicher et al., 2016; Kwiatkowski et al., 2020), which have been attributed, among other factors, to “incomplete understanding of fundamental processes” (Laufkotter, et al. 2015). Recent studies of time series of satellite data to extract trends in primary production admittedly suffer from the short length of the time series. Therefore, uncertainty in future estimates of marine primary production should be addressed.

In the ocean, the attenuation of light and the response of phytoplankton to light are both nonlinear (Platt et al.,1990; Kirk, 2011; Kovač et al., 2016), making photosynthesis a strong function of depth. Modern models of marine primary production use bio-physical laws to describe the photosynthesis-light relation and to predict the amount of carbon assimilated in photosynthesis. They are applicable from mesoscale to the global scales. To quantify and predict primary production using these models the essential step is the assignment of model parameters. The key parameters are the photosynthesis parameters, which dictate the rate of inorganic carbon assimilation in photosynthesis and link light intensity, a physical variable, to the rate of carbon assimilation, a biological process. Accurate assignment of photosynthesis parameters effects global estimates of primary production (Kulk el al., 2021).

Historically, modelling concepts and ideas in bio-physical models of marine primary production came largely from the physical (optical) and algal physiology literature. Unbeknownst to the vast majority of physicists and ecologists working on primary production lies the rich economics literature on production theory. Likewise, unbeknownst to many economists is the rich literature on primary production theory in the ocean. The two disciplines have not communicated well, and the flux of ideas was virtually non-existent between the two fields, in stark contrast to fisheries, where the transfer of knowledge did occur. This is rather unfortunate, given that phytoplankton primary production is arguably the oldest productive system on Earth: stable marine phytoplankton assemblages have persisted for some 2 Ga. As such it should be studied extensively as a blueprint example of sustainability, with physical economics and modern thermodynamics, as promising avenues for exploring these issues.

Using the analogy between heat and money, energy and capital and finally work and production, thermodynamic laws can be used to derive the production function (Richmond et al., 2013). The production function depends on three quantities: capital, the advancement of technology and the size of the labour force. The physical economics theory (Econophysics) explains economic profit in a production cycle in the same way that work is explained in a Carnot cycle. A gradient of temperature drives a heat engine, whereas a gradient in income drives an economic engine. In the ocean a light gradient drives photosynthesis and in turn photosynthesis drives the entire ecosystem. Therefore, combining thermodynamics, economics and biophysical models of primary production will give way to new models which will may potentially yield bioeconomic indicators as emerging intrinsic properties of the structure and functioning of the marine ecosystem. This is crucial, as the current oceanographic understanding of the interplay between physics and biology is not adequate to address climate-change related threats to the marine ecosystem. Developing new models in the service of sustainable management of marine ecosystems is a must to ensure the presence of these ecosystems in the future.

Of major concern in the context of climate change is the response of primary production to changing surface ocean stratification and subsequently surface mixing, which exerts a strong control on both phytoplankton phenology and primary production (Kovač et al., 2021). For oceanic primary production, variability in the intensity of mixing presents a strong disturbance, controlling the average light levels in the mixed-layer as well as the supply of nutrients into the layer (Platt et al., 2003). Mixed-layer shallowing favours phytoplankton growth, as it increases the average light conditions in the mixed layer, whereas mixed-layer deepening decreases it, provided the nutrients are not limiting.


However, there is an asymmetry in the response of mixed layer production to deepening, in contrast to shallowing, caused by the non-linearities in the response of photosynthesis to the underwater light field. In relative terms, shallowing can cause a greater increase in mixed-layer production, than the reduction caused by a mixed-layer deepening of the same magnitude. This asymmetry calls for a re-examination of the notions of stability and resilience in aquatic primary production (Kovač et al., 2020). A plausible way of exploring primary production stability and resilience is through the lenses of economic theory.

The PHOTOCLIM project proposes to apply modern capital theory directly to the study of marine primary production at the biophysical level for the first time. The project aims to reforge the current understanding of the interplay between biology, physics and economics in the ocean, by adopting a first principles approach, in what was historically largely an inductive enterprise. The objective of the project is to assess the current state and to forecast the future state of ocean ecosystems using newly defined bioeconomic indicators.

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