This mass-specific consumption rate is used in algae_dynamics() to
calculate the algae biomass at the next time step. To get the
non-mass-specific consumption rate, use getAlgaeConsumption().
Arguments
- params
MizerParams
- n
A matrix of current species abundances (species x size)
- rates
A list of rates as returned by
getRates()
Algae consumption
This rate deliberately does not depend on feeding level or the
satiation species parameter (contrast with detritus_consumption(),
which does): in mizerReef, satiation-mediated consumption is exclusive to
detritivory. Increases in herbivorous fish density following coral
bleaching events suggest that reef herbivores respond to increased food
availability without regulating their consumption (Ledlie et al. 2007;
Pratchett et al. 2008; Khalil et al. 2013; Elma et al. 2023), and
Caribbean herbivores have been observed to fill their gut up to three
times a day (Ferreira et al. 1998; Kopp et al. 2010). Algal depletion is
therefore modelled as driven by continuous grazing pressure rather than
by any individual consumer's satiation state. getAlgaeConsumption()
reports the feeding-level-adjusted rate actually ingested by each species
for diagnostic purposes, but that adjusted rate is not what depletes the
algae pool or what tuneUR()/tuneUR_cc() use for tuning.
The rate at which herbivorous consumer groups encounter algae biomass \(E_{i.A}(w)\) is controlled by the parameter \(\rho_{A.i}\). It scales with the size of the consumer raised to an allometric exponent \(m_{alg}\) which is taken from empirical data.
$$E_{i.A}(w)=\rho_{i.A}\, w^{m_{alg}}\,B_A$$
The mass specific consumption rate then accounts for the preference of functional group $i$ for algae, \(\theta_{i.A}\). This gives the mass-specific algae consumption rate:
$$c_A = \sum_i\int\rho_{i.A}\, w^{m_{alg}} N_i(w)\theta_{i.A}\,dw$$
Examples
data(caribbean_3_model)
algae_consumption(caribbean_3_model)
#> [1] 9.21051e+12