Display author nickname

I’m trying to get the author nickname to display but it’s not working and I’m obviously doing something wrong!
Here is what I have: (nothing displays and there is something in the nickname field)

<?php
$rand_posts = get_posts('numberposts=5&orderby=post_date&order=DESC&cat=16');
foreach( $rand_posts as $post ) :
echo '<div class="twelve columns blog">';
$selected_id = get_the_ID();
$queried_post = get_post($selected_id);
$selected_content = $queried_post->post_content;
$selected_name = get_the_title($selected_id);
$selected_excerpt = wp_trim_words($queried_post->post_content,$num_words = 50, $more = null);
$selected_link = get_permalink($selected_id);
$selected_pic = get_the_post_thumbnail($selected_id, 'rsm-medium');
$selected_author = get_the_author_meta('nickname');
$selected_date = $queried_post->post_date;
$newDate = date("F j, Y", strtotime($selected_date));

echo '<h2 style="font-size:34px;font-weight:200;"><a href="'.$selected_link.'" >' . $selected_name . '</a></h2>';
echo $selected_pic;
echo '<div class="blog-author-date">Posted by' . $selected_author;
echo $newDate . '</div>';
echo $selected_excerpt;
echo '</div> <!-- / twelve -->';
endforeach;	?>