Question

beachipods were abundant dueing paleozoic fimd fhan now , for brachiopods feeding biology,

1) what effect might this decline have had on bacterial biomass in ocean

3) what role might the rising abundance of bivalve mollusks during the mesozic and cenzoic periods have played in this decline?

Answer 1

1.The brachiopods generally preferred seeps with abundant hydrocarbons at bottom waters above the seep, such as oil seeps or methane seeps , whereas seeps with strong fluid flow and hence abundant hydrogen sulfide were less favorable for them. At methane seeps typified by diffusive seepage and oil seeps, oxidation of hydrocarbons in the bottom water by chemotrophic bacteria enhances the growth of bacterioplankton, on which the brachiopods could have filter fed. Whereas chemosymbiotic bivalves mostly relied on sulfide-oxidizing symbionts for nutrition, for the brachiopods aerobic bacterial oxidation of methane and other hydrocarbons played a more prominent role. Hence bacterial biomass producing geofuels have become less due to decline in Brachiopods.

2.Brachiopods and bivalves feed in similar ways and have occupied the same environments through geological time, but brachiopods were far more diverse in the Palaeozoic time whereas bivalves dominated the era of post-Palaeozoic.There is also evidence of dominance in factors such as metabolic activity. Here,from the perspective of energy use, finding that bivalves already accounted for a larger share of metabolic activity in Palaeozoic oceans. We also find that the metabolic activity of bivalves has increased by more than two orders of magnitude over this interval, whereas brachiopod metabolic activity has declined by more than 50%. Consequently, the increase in bivalve energy metabolism must have occurred via the acquisition of new food resources rather than through the displacement of brachiopods. The canonical view of a mid-Phanerozoic transition from brachiopod to bivalve dominance results from a focus on taxonomic diversity and numerical abundance as measures of ecological importance. From a metabolic perspective, that's why the biomass of chemotropic bacteria has reduced with decline in number of brachiopods