The phrase "altered markedly" is correct and usable in written English.
It can be used to describe a significant change or modification in something, often in a formal or academic context.
Example: "The results of the experiment showed that the conditions had altered markedly from the previous trials."
Alternatives: "changed significantly" or "modified considerably."
By the time of Rameau, the concept of the dissonance had altered markedly.
In these works over the years Bickerton has pursued an inlaid patterning arrangement of flat multisided stones, and the moods of these works have altered markedly with time.
Components of carpal bone motion were altered markedly at all positions of dorsal angulation of the distal radius.
The absorption spectrum of 1 was altered markedly upon mixing with a few rare earth metal ions and some transition metal ions.
The semiarid tropical scrublands are reasonably intact across large areas, but the more southerly chenopod scrublands have been altered markedly during the past 150 years by intense sheep grazing.
The religious makeup of Samoa was altered markedly in the late 20th century, as many in the country joined the Mormon church.
However, nutrient losses through guttation at times may be of sufficient magnitude to alter markedly the behavior of the plant.
4CP has been shown to alter markedly the anodic kinetics of Ag: active corrosion in chloride environment is changed to a pseudo-passivating behaviour and potential oscillations, typical for the formation of thick AgCl layers, are suppressed.
This can alter markedly the normal lung sounds that could be heard from the ventilation of a healthy lung.
Gender difference in T0 response indicating that boys were less likely than girls to respond positively (p = .088) did not alter markedly post-intervention.
Furthermore, p53 in the unirradiated mammospheres was shown to be more highly phosphorylated at serines 9 and 15, and again this did not alter markedly with dose.
