The baby dolphin lay on its side, one flipper pointed toward cloudy skies, rocking back and forth with the waves near Innarity Point, FL

“I looked and saw a baby porpoise, a terrible sight to see,” local resident Chris McCune told WKRG-TV News out of nearby Mobile, AL.

This young dolphin was one of the most recent of at least 138 dolphins that have died in the Gulf this year, nearly half of them premature or newborn calves.

But that’s just the tip of the iceberg, scientists say. Many more dolphins are dying in the Gulf than are officially counted. New research released today shows that the average number for most species may be 50 times higher than what’s reported now, a conservative figure according to the authors.

Dolphins at play near Orange Beach, AL Photo by Rocky Kistner/NRDC

That suggests that so far this year, more than 6,500 dolphins may have died, and, according to the report, for some species of mammals, the rate is 250 times higher. As NRDC’s Michael Jasny notes in his blog today, the researchers point out that the media have reported that the BP oil disaster may have modest environmental impacts due to the low numbers of wildlife and mammal mortalities. That is far from the case.

This frightening math makes determining the provenance of the 130 stranded animals all the more urgent. As I’ve said before, the dolphin communities that have made their homes in the Gulf’s bays, sounds, and estuaries are small and semi-isolated, and the death of even a few babies can have outsized effects on the group. The shelf and offshore populations are larger but not vast, and the death of hundreds, let alone thousands, of animals would far exceed the government’s estimate of what they can reasonably sustain.

A NOAA spokeswoman said the agency is looking at the new data, but that it has always pointed out that the true number of dead mammals is much higher than what washes onshore. “We’ve been saying for a long time, a lot of marine mammals die in the ocean that we never will see.”

There are many reasons for this, but mostly because sea mammals this size that die are quickly consumed by other predator fish or sink to the bottom of the ocean. As Michael Jasny explains in a previous blog, determining what caused these deaths is not easy. The results of a special federal investigation into dolphin deaths could take many months or years.

Determining the cause of death in stranded whales and dolphins can be tricky business, even with a major offshore spill in the backdrop. We know that oil exposure can upset reproduction in wild mammals, and that dolphins aren’t particularly adept at avoiding sheens and emulsified oil. On the other hand, the calves might have died of infectious disease, or their mothers’ exposure to unrelated toxins, or any one of a variety of other causes, and their high reported numbers could be an artifact of the intensified monitoring that presumably has followed the spill.

The Gulf will soon witness the return of vacationers and college kids on spring break heading to the beaches, hoping to find some relaxation in the sun after a long winter up north. But for residents who live there, the arrival of spring has brought more confusion and concern. "We can't seem to get any answers from anybody about anything and that's very frustrating," one resident told WKRG-TV

That seems to be the norm these days in the Gulf, from deaths of sea turtles to the safety of the seafood. But many people in the Gulf are certain about one thing: The unfolding of this oil disaster is far from over.