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Notes on “Viral infection as a regulator of oceanic phytoplankton populations” by Rhodes et al. (2008)

I remember that one of the effect of viruses is to reduce the efficiency of the biological pump. It seems this model does reproduce this effect at the simplest level (nutrient is more available and primary production is reduced with viruses).

For low level of contagion, the system reaches a steady state. However, “[f]or very high levels of viral transmissibility, the system moves from stable fixed point behaviour to a high frequency limit-cycle oscillation of plankton and virus.”

See Singh, B.K., Chattopadhyay, J., Sinha, S., 2004. The role of virus infection in simple phytoplankton zooplankton system. J. Theor. Biol. 231, 153–166.

“The large population swings that occur risk rapid population extinction in the deep troughs of the cycle and are probably not realised in practice. It is likely (in the absence of other survival mechanisms, such as viral sequestration in sediment) that any highly transmissible viruses that do emerge tend to be eliminated from the ecosystem in this way.”

This is not in accord with the work of Rodrigues-Valera et al. (2008) that do consider oscillating states.

The authors consider seasonal change in phytoplankton. I always wanted to include instead episodic input as it seems what is going on around station ALOHA (see Ascani et al. 2011, in progress). For that, I need to review the literature I read a long time ago about using episodic events to explain the plankton paradox. See, in particular, Bio_Chaos/Plankton_Paradox/Roy_Chattopadhyay_07.pdf and Ebenhoh, W., 1988. Coexistence of an unlimited number of algal species in a model system. Theor. Popul. Biol. 34, 130–144. “Although most mechanisms discussed in the literature allow the coexistence of a few extra competitors, unlike the real-world, very few theories would allow the coexistence of hundreds of species on a small number of resources (an exception is the model of Ebenhoh, 1988, discussed).

Re-reading (02/01/2013)

Question: In Model 2, if infected P cannot grow, why should they be taken into account in the term of the carrying capacity? Rhodes et al. say that the infected phytoplankton do take nutrient, in order to producing the viruses.

Read Singh et al. (2004) and Malchow et al. (2005).