  We report nine years of optical spectroscopy of the metal-polluted white
dwarf SDSS J104341.53+085558.2, which presents morphological variations of the
line profiles of the 8600 \AA\ Ca II triplet emission from the gaseous
component of its debris disc. Similar changes in the shape of the Ca II triplet
have also been observed in two other systems that host a gaseous disc, and are
likely related to the same mechanism. We report the Mg, Si, and Ca abundances
of the debris detected in the photosphere of SDSS J1043+0855, place upper
limits on O and Fe, and derive an accretion rate of (2.5 - 12)x$10^8$ g/s,
consistent with those found in other systems with detected debris discs. The
Mg/Si ratio and the upper limit on the Fe/Si ratio of the accreted material
broadly agree with those found for the crust of the Earth. We also review the
range of variability observed among white dwarfs with planetary debris discs.
