4.4.5. Role of CAB in iron fertilisation
Pleuromamma spp. carries a similar proportion of ferric iron
reductase gene (fhuF) and ferrous iron transport protein A gene (feoA)
(Figure S6a, b). The presence of high proportion of ferric iron
reductase gene fhuF in Pleuromamma spp. needs detailed
investigation. It was reported that acidic and low-oxygen conditions in
copepod gut may assist iron dissolution and remineralisation, forming
soluble Fe (II) [13, 67]. Thus, this increases the
iron bioavailability in the surrounding, which promotes phytoplankton
growth [67]. Also, bacterial community associated
with the zooplankton, such as Bacteroidetes, Alphaproteobacteria and
Gammaproteobacteria, are known to carry genes involved in iron
metabolism [9].
An early study on Thalassiosira pseudonana fed to Acartia
tonsa was found to have Fe in the faecal pellets[68]. But, in the present analysis, Acartiaspp. was found to have less proportion of feoA gene when compared toTemora spp. and Pleuromamma spp. Moreover, genes involved
in iron metabolism were reported to be high in zooplankton associated
microbiome [9].
Since the differential iron contributions of different copepod genera
were unknown until now. For organisms that must combat oxygen limitation
for their survival (Pleuromamma spp.), pathways for the uptake of
ferrous iron are essential. Nevertheless, the meta-analysis performed
here showed that Pleuromamma spp. could be a significant
contributor to both iron bioavailability and nitrogen fixation.