Deprecated: Assigning the return value of new by reference is deprecated

I have recieved this error on all subdomains and main domain of my multisite , please help
Deprecated: Assigning the return value of new by reference is deprecated
Deprecated: Assigning the return value of new by reference is deprecated in /var/www/les-guides-agir/public_html/wp-content/plugins/seo-ultimate/seo-ultimate.php on line 83 Strict Standards: Redefining already defined constructor for class SU_Module in /var/www/les-guides-agir/public_html/wp-content/plugins/seo-ultimate/modules/class.su-module.php on line 111 Strict Standards: Non-static method suio::is_dir() should not be called statically, assuming $this from incompatible context in /var/www/les-guides-agir/public_html/wp-content/plugins/seo-ultimate/plugin/class.seo-ultimate.php on line 450 Strict Standards: Non-static method suio::tslash() should not be called statically, assuming $this from incompatible context in /var/www/les-guides-agir/public_html/wp-content/plugins/seo-ultimate/includes/jlfunctions/io.php on line 15 Strict Standards: Non-static method suio::untslash() should not be called statically, assuming $this from incompatible context in