Multitrophic Interactions in the Sea: Assessing the Effect of Infochemical-Mediated Foraging in a 1-d Spatial Model

Abstract

Abstract. The release of chemicals following herbivore grazing on primary producers may provide feeding cues to carnivorous predators, thereby promoting multitrophic interactions. In particular, chemicals released following grazing on phytoplankton by microzooplankton herbivores have been shown to elicit a behavioural foraging response in carnivorous copepods, which may use this chemical information as a mechanism to locate and remain within biologically productive patches of the ocean. In this paper, we use a 1D spatial reaction-diffusion model to simulate a tri-trophic planktonic system in the water column, where predation at the top trophic level (copepods) is affected by infochemicals released by the primary producers forming the bottom trophic level. The effect of the infochemical-mediated predation is investigated by comparing the case where copepods forage randomly to the case where copepods adjust their vertical position to follow the distribution of grazing-induced chemicals. Results indicate that utilization of infochemicals for foraging provides fitness benefits to copepods and stabilizes the system at high nutrient load, whilst also forming a possible mechanism for phytoplankton bloom formation. We also investigate how the copepod efficiency to respond to infochemicals affects the results, and show that small increases (2%) in the ability of copepods to sense infochemicals can promote their persistence in the system. Finally we argue that effectively employing infochemicals for foraging can be an evolutionarily stable strategy for copepods.

Revisiting the Stability of Spatially Heterogeneous Predator–Prey Systems Under Eutrophication

“…An increase in the size of the habitat can also either destabilize or stabilize the system. This result is somewhat counterintuitive since in earlier works it was shown that for an exponential parametrization of r(h), an increase in the spatial gradient of the growth function or the size of the habitat will always facilitate stabilization of the system [30,27].…”

“…Modelling predator-prey interaction in a spatially heterogeneous habitat, where an exact location of individuals on a demographic timescale cannot be properly assigned, requires the implementation of partial integro-differential equations. However, the complexity of this framework makes it rather difficult to treat the model analytically: all previous findings have been obtained by direct numerical simulations of the equations for particular parameterisations of the model ingredients [30,27]. This, obviously, cannot be considered as a rigorous proof of stabilization of the system.…”

Mathematical Modelling of Spatiotemporal Dynamics of Oxygen in a Plankton System

“…There is considerable literature concerned with various aspects of plankton dynamics in space and time. Conceptual prey-predator-type models to describe the phytoplankton and zooplankton interaction in marine ecosystems subject to turbulent mixing were considered in much detail in [4,16,20,21,31] but with no attention to the oxygen production. In another mathematical study, Edwards and Brindley [7] investigated the dynamics of a coupled plankton-nutrients system, but did not pay any attention to their possible relation to dissolved oxygen.…”

Tri-trophic Plankton Models Revised: Importance of Space, Food Web Structure and Functional Response Parametrisation

“…When taking into account fast and slow moving grazers, we can realistically assume that a typical plankton food web is tri-trophic [27,28]: it includes producers such as phytoplankton, slow moving predators such as microzooplankton and fast displacing higher predators such as copepods. The stability of tri-trophic food chains including local and global predators has recently been explored by Lewis et al 2013 [35], where the authors found that primary producers can be controlled by grazers, although the phytoplankton density can 'bloom' and have their high values near the surface. However, these findings were obtained using some particular assumptions about the structure of the food web and the formulation of the functional response of the predator.…”

“…In theoretical ecology such predation is known as 'intragild' predation, and it is a widespread phenomenon in food webs [45]. Another important assumption in [35] was that the spatial distribution of copepods followed info-chemicals released as a result of grazing of phytoplankton by microzooplankton, which may not always be correct [4].…”