There were thousands of txs there. Was anyone experimenting small amount txs on Dec. 5th?
My best guess would be a bloating attack.
More destroyed coins around this date (http://peerchain.net/charts_supply.html) 
For reference: https://www.reddit.com/r/peercoin/comments/2oi8t5/peercoin_total_number_of_transactions_about_to/