Potential consequences of climate change for primary production and fish production in large marine ecosystems

Abstract

Existing methods to predict the effects of climate change on the biomass and production of marine communities are predicated on modelling the interactions and dynamics of individual species, a very challenging approach when interactions and distributions are changing and little is known about the ecological mechanisms driving the responses of many species. An informative parallel approach is to develop size-based methods. These capture the properties of food webs that describe energy flux and production at a particular size, independent of species' ecology. We couple a physical–biogeochemical model with a dynamic, size-based food web model to predict the future effects of climate change on fish biomass and production in 11 large regional shelf seas, with and without fishing effects. Changes in potential fish production are shown to most strongly mirror changes in phytoplankton production. We project declines of 30–60% in potential fish production across some important areas of tropical shelf and upwelling seas, most notably in the eastern Indo-Pacific, the northern Humboldt and the North Canary Current. Conversely, in some areas of the high latitude shelf seas, the production of pelagic predators was projected to increase by 28–89%.

Climate change in size-structured ecosystems

“…Moreover, shifts in the body-mass distributions of populations can be triggered by warming or drought of freshwater ecosystems [17,73,93]. These modifications in the community size structure can relax top-down control causing modifications in primary production [14], secondary production [13], community metabolism and biogeochemical fluxes exceeding the direct consequences of warming [9].…”

“…Interestingly, fish production depends more on primary production than on direct effects of temperature, thus stressing the importance of thermal bottom-up cascades (figure 2) in marine systems. Predicted declines of 30-60% in fish production will impose severe threats on the security of the future food supply [13]. These studies suggest that warming may have complex effects on community-level patterns (figure 1d) that feed back to determine population persistence, with high-trophic-level species being most threatened.…”

“…The stability implications of warming may thus represent a double-edged sword [11]. Similarly, synthetic models of size-spectrum communities and ocean-biogeochemical processes can be used to predict the consequences of warming for community-level patterns such as primary and fish production in marine ecosystems [13]. Interestingly, fish production depends more on primary production than on direct effects of temperature, thus stressing the importance of thermal bottom-up cascades (figure 2) in marine systems.…”

“…This theme issue integrates novel approaches for addressing the consequences of climate change in complex, sizestructured ecosystems. This includes the development of novel concepts [7][8][9][10], model analyses [11][12][13] and empirical studies in marine [14,15], freshwater [16,17] and terrestrial ecosystems [18][19][20][21][22]. In the following, we will introduce the framework of this theme issue by describing the complexity and the size structure of natural communities and how they might interact with climate change in determining top-down or bottom-up control, community stability and spatial processes.…”

Climate change in metacommunities: dispersal gives double-sided effects on persistence

“…This increases the total amount of time an individual spends dispersing and naturally also the exposure to the dispersal mortality. Empirical studies have demonstrated the sensitivity of top predators to even small disturbances [45][46][47], which probably stems from their susceptibility to indirect effects [48]. Disturbances to top predators can have far-reaching consequences owing to their wide-ranging distributions and long generation times, slowing recovery and thereby making their sensitivity even more alarming.…”