This might vary between airports but if a Checker vehicle (usually that's the aerodrome authority) finds a problem with the runway, it's their airport and they'll ususally tell ATC what they want to do. These day's it's probably an immediate suspension of operations (breaking traffic off approach, stopping deps etc) until the problem can be fixed in some way. Due to liability concerns, etc, it's unusual for pilots to be told that there's debris or damage on the runway but "you're cleared to land" anyway. Better to confirm that there's nothing to burst tyres or get sucked into engines before allowing any further movements.
"Seagull" is usually a birdscaring unit who's constantly tasked with keeping birds away from the runway.