How did the ottoman empire's entry into the war on the side of the central powers have a negative impact on russia

Lost port connections--within the Ottoman Empire, Russia had trade connections and use of ports to trade in the Mediterranean. 

Russia struggle with trading ports and with so few ways to access the global trade, losing one impacted their economy. Russia had trade deals with the Ottoman Empire and was able to access the Mediterranean through those deals. During WWI, becoming enemies meant loss of trade both in and out of Russia.