There have been several ecological studies of the USS Arizona and the impact that the rupturing oil bunkers will have. The reason for these studies though is that the Arizona is sitting in a rather small harbor so the oil will have an impact before it dissipates into the surrounding ocean.

There is some debate over whether it would be proper to remove the oil from the ship now as it is likely that the oil itself is providing some structural support. Draining the oil bunkers could cause the ship to collapse earlier than it otherwise would. However, if the oil is left, once the ship collapses, as it eventually will, all of the oil will hit the harbor at once and will cause an ecological disaster (for the immediate area anyway).

Outside of the Arizona, I am not aware of any other studies of any wrecks. My guess though is that the volume of water surrounding the ship or sub is so great in most cases that the impact would be very minimal. Pearl gets attention because of the enclosed harbor. If the Arizona was out in the middle of the Pacific with lots of current and water, it wouldn't hurt much of anything.

From what I have read, it seems the biggest environmental problem is oil leakage.

NOAA has this report of oil pollution from shipwrecks, including merchant ships sunk in WWII: http://www.noaanews.noaa.gov/stories2013/20130520_shipwrecks.html

But the worst is not in US coastal waters, but in Pacific. For example, more than 50 sunken ships/boats in the Ironbottom Sound, slowly rusting away, and the leakage has been increasing. I remember there was a National Geographic report about the leaks but can't find it at the moment, here is a report about this on news.

One other noteable example, besides the Arizona, is the wreck of the German heavy cruiser Blucher. The Blucher was sunk at extremely close range by Norwegian coastal defenses in shallow water in a fjord just near Oslo during the German invasion in April 1940 in the Battle of Drøbak Sound.

By 1994, the leaking had progressed to the extent that Norway decided to remove all reachable oil from the ship.

Bikini Atoll had several ships sunk in it's lagoon during Operation Crossroads. The fleet sunk there would have been the 6th largest navy in the world. 95 ships ranging from aircraft carriers and battleships to small amphibious troop transports were set up in the lagoon and then had a nuclear bomb dropped on them. The they had a nuclear bomb exploded under the surface of the water. Not all of them actually sank in the harbor. Some of them survived and were used as targets for later exercises.

Many of the ships had fuel and ordinance onboard. The environmental impact of the fuel and ordinance of course comes behind the impact of the nuclear blasts and radiation but sea life is coming back to the area and the coral is recovering.