I added an on click event on the anchor element that closes its corresponding accordion item:
$(function() {
$( "#accordion" ).accordion({
active: false,
collapsible: true,
heightStyle: "content",
navigation: true,
header: ".menuitem"
});
var hash = window.location.hash;
var anchor = $('a[href$="'+hash+'"]');
if (anchor.length > 0){
anchor.click();
}
//$("#accordion").on('click', '.ui-accordion-content a', function(){
$("#accordion").on('click', '.ui-accordion-content .reduce', function(){ //edit
$(this).parent().slideToggle();
});
});