Jackson2013-Status and Trendsof Caribbean Coral Reefs

Pacific lionfish Pterois volitans throughout the
entire wider Caribbean over the past decade
(De Leon et al. 2011; Hackerott et al. 2013) or
the uncontrolled spread of the alga Caulerpa
taxifolia in the northern Mediterranean
(Meinesz et al. 1993, 2001). The effects
of lionfish on Caribbean invertebrates and
fishes could be very considerable, especially
in exacerbating the consequences of
overfishing by depleting juvenile parrotfishes
and surgeonfishes (Albins and Hixon 2011).
However, it is too soon to tell whether native
predators might eventually have an impact
of lionfish, especially in marine reserves
where predators could regain their former
abundance (Mumby et al. 2013).
Far too little attention has been paid,
however, to the introduction of the myriad
marine organisms we cannot see, including
virtually all microorganisms and pathogens.
The case of the unidentified pathogen that
caused the mass mortality of Diadema
antillarum in 1983-1984 is a case in point.
Diadema mortality began next door to the
Caribbean entrance to the Panama Canal,
whence it spread like wildfire on ocean
currents eastward to Trinidad and Tobago
and northward throughout the western
Caribbean, Greater Antilles, and Florida all
the way to Bermuda, with mortality in the
eastern Caribbean arriving from both the
north and the south in 1984 (Lessios et al.
1984; Lessios 1988). Introduction via ballast
water from the Pacific is seemingly the only
explanation.
This begs the question of why so many
Caribbean coral diseases first appeared in
the 1970s and early 1980s for which there
is no compelling environmental explanation.
These first coral diseases include black band
disease that first appeared in 1973 and
white band disease that first appeared in
1977 (possibly earlier) that is by far the most
devastating of the coral diseases through
its virtual elimination of formerly dominant
Acropora palmata and A. cervicornis
throughout most of the Caribbean by
the early 1980s (Weil and Rogers 2011).
Temperatures were not excessively warm in
the 1970s and heating in relation to El Nino
in 1983 was small compared to the episodes
in 1995, 1998, 2005, and 2010. There is
also no evidence of a pervasive decline in
Caribbean water quality before the 1980s or
later.
In contrast, the volume of international
shipping exploded in the late 1960s with
the advent of bulk carriers and enormous
cruise ships that discharged untold volumes
of ballast water into coastal waters before
stricter regulations may have begun to take
effect (Carlton 1996). Greater speed of
transport among distant ports may also be a
contributing factor. Many introduced species
have been transported by ballast water, and
this is especially true for microbes that have
been calculated to be transported in numbers
on the order of 10 20 /year into the lower
Chesapeake Bay alone (Ruiz et al. 2000;
Drake et al. 2007). None of this proves that
Diadema disease or WBD were introduced
into the Caribbean from another ocean. But
given the numbers, it is remarkable that all
marine diseases have not been introduced
throughout the global ocean.
Once introduced, different environmental
factors may retard or promote the growth
of introduced species including species that
cause disease. But it is important not to
confuse the causes of an initial outbreak from
factors that may subsequently promote or
inhibit its spread and increase.
It is therefore of considerable interest that the
Caribbean is by far the most geographically
isolated of all the tropical oceans with
extensive coral reefs. The Caribbean has
been separated from the vast Pacific to the
west by the Isthmus of Panama for about
3½ million years (Coates and Stallard 2013;
Jackson and O’Dea 2013) and from the
tropical Indian Ocean to the east by the
continents of Africa and Asia, the subtropical
Mediterranean, and the inhospitable eastern
Atlantic. It is therefore of considerable interest
that the effects of diseases on Caribbean
reef associated species have been so much
more extreme than in other tropical seas.
Nothing like the mass mortality of Diadema
has affected any echinoderm throughout the
entire Indian Ocean or Pacific, nor has any
genus of Indo-Pacific coral suffered such
broad extirpation as Caribbean Acropora.
All of this suggests that isolation has been a
64 STATUS AND TRENDS OF CARIBBEAN CORAL REEFS: 1969-2012