They are some of the ocean's smallest
inhabitants and on coral reefs

microorganisms are copious creatures.
Microbes are very prolific on the

surface of corals, both in healthy and
diseased corals. But in a world that's

invisible to the naked eye, drastic
changes are taking place.

Whether it's Australia or the Bahamas or the Florida
Keys, all of the scientists see this

microbial power shift. With healthy corals,
when temperatures increase pathogenic

bacteria go up and the beneficial
bacteria go down. Just like when we get

stressed out, we're more likely to get a
cold. When you stress out these corals

they could potentially be more susceptible to bleaching or getting a disease.

Throughout Florida scientists
painstakingly work to identify key

players within this microbial community.
It's estimated that you can only culture

one percent or the less of the bacteria
that are out there, but yet corals have

thousands of different kinds of bacteria
associated with them. While some of the

bacteria found on corals are important
to their health, others can lead to

disease outbreak. This bacterium that was
killing the coral, we could hypothesize

based on what we knew about the
bacterium that it might be coming from humans.

Usually we hear about pathogens
from wildlife to humans - examples are HIV,

swine flu and avian flu, but we haven't
had the reverse. And so this is a new

disease mechanism that we're not familiar
with, especially in the marine environment.

With experimental sites in
the lab and in the sea, what will

microbes reveal about coral health?

How do human activities impact the microbial balance on the reef?