carto.css

#occurrence {
        marker-fill: #a82400;
        marker-opacity: 1;
        marker-width: 2;
        marker-line-color: white;
        marker-line-width: 0.3;
        marker-line-opacity: 0.5;
        marker-placement: point;
        marker-type: ellipse;
        marker-allow-overlap: true;
}
#occurrence[zoom>=5] {
        marker-width: 4.5;
}
#occurrence[zoom>=7] {
        marker-width: 5;
        marker-line-width: 0.6;
}
#occurrence[zoom>=9] {
        marker-width: 5.5;
        marker-line-width: 0.9;
}
#occurrence[zoom>=11] {
        marker-width: 6;
        marker-line-width: 1;
}
#occurrence[zoom>=13] {
        marker-width: 6.5;
        marker-line-opacity: 1.2;
}
#occurrence[zoom>=15] {
        marker-width: 7;
}
#occurrence[zoom>=17] {
        marker-width: 7.5;
        marker-line-width: 1.5;
}
#occurrence[zoom>=19] {
        marker-width: 8;
        marker-line-width: 1.7
}