[Coral-List] Extensive bleaching documented in parts of the Florida Keys

[Marilyn Brandt]

Extensive coral bleaching has been observed over the past several weeks at
two inshore patch reef sites of the middle Florida Keys, U.S.A and recently
at three inshore patch reef sites of Biscayne National Park as well.  Some
paling and bleaching has also been observed over the several week time
period at two offshore reef sites in the upper Florida Keys. What follows
are short bleaching reports from these three regions. Links to pictures will
follow in a later email.

Middle Keys Patch Reefs

At two Florida Keys inshore patch reef sites, Cheeca Rocks and Coral
Gardens, extensive coral bleaching has been observed affecting up to 80% of
scleractinian corals.  Cheeca Rocks and Coral Gardens are located offshore
of the middle Florida Keys and these sites are currently being monitored as
part of a dissertation study on coral disease. Five 16m2 permanent plots
were established at each of these sites in August of 2004 and a total of 266
corals at Cheeca Rocks and 350 corals at Coral Gardens have been monitored
for the incidence of bleaching and disease since that time.

On August 11th, 2005, I observed some partial bleaching affecting only a few
of the monitored colonies. When I returned on August 16th, paling and
partial bleaching was occurring on 19% and 33% of the monitored corals at
Cheeca Rocks and Coral Gardens respectively.  This bleaching was mainly
affecting species of Colpophyllia natans and Montastrea faveolata. However,
at this point all of the monitored colonies of Agaricia agaricites within
the quadrats were completely bleached.  

On September 1st, I revisited the sites to find that 74% of monitored corals
at Cheeca Rocks and 80% of monitored corals at Coral Gardens were
experiencing some extent of bleaching (paling, partial bleaching, or total
colony bleaching).  The proportions of all colonies experiencing total
bleaching (i.e. no observable color from zooxanthellae) were 11% at Cheeca
Rocks and 15% at Coral Gardens.  Species most affected by the bleaching were
C. natans, M. faveolata, and A. agaricites.  Other species found bleaching
included M. annularis, M. cavernosa, Dichocoenia stokesii, Diploria clivosa,
D. strigosa, D. labrynthiformis, Favia fragum, Meandrina meandrites, Mussa
angulosa, Porites astreoides, P. porites, Siderastrea radians, S. siderea,
and Stephanocoenia intersepta.  Species other than scleractinian corals
observed to be bleaching included Millepora alcicornis, M. complanata,
Palythoa caribaeorum, Erythropodium caribaeorum, Briareum asbestinum, and
some other gorgonians. The only notable exception was individuals of
Mycetophyllia spp. which appeared healthy and experienced no noticeable
bleaching.

The sites were again revisited on September 6th and no recovery was
observed. In addition, three new Black-band diseases had begun affecting
100% bleached colonies of C. natans at Coral Gardens and though they were
not found within the quadrats, similar infections were observed on colonies
of C. natans at Cheeca Rocks. 

Water temperature was recorded during each site visit with a YSI-30 at
depths of 1 meter and 5 meters from the surface.  Water temperatures in
degrees Celsius were recorded as follows: 
8/11/05: 
Cheeca Rocks; 1m: 31.7, 5m: 31.7
Coral Gardens: 1m: 31.8, 5m: 31.8
8/16/05: 
Cheeca Rocks; 1m: 31.7, 5m: 31.7
Coral Gardens; 1m: 32.0, 5m: 32.0
9/1/05: 
Cheeca Rocks; 1m: 31.1, 5m: 31.1
Coral Gardens; 1m: 31.1, 5m: 31.4
9/6/05: 
Cheeca Rocks; 1m: 30.5, 5m: 30.3
Coral Gardens; 1m: 30.6, 5m: 30.6

Upper Keys Offshore Reef Sites

In August of 2004, five 16m2 permanent quadrats were also established at two
offshore reef sites in the upper Florida Keys, French Reef and Little
Grecian. 366 corals at French Reef and 269 corals at Little Grecian have
been monitored since the establishment of the quadrats and in recent weeks
some bleaching has been observed.  This bleaching is not nearly to the
extent as that seen in the inshore patch reefs. 

On August 9th and 17th, 2005, these two sites were visited and monitored
colonies were examined and their condition documented. At this time, some
paling of A. agaricites was occurring.  When sites were visited again on
September 2nd, colonies of A. agaricites, M. alcicornis, M. complanata, S.
radians, and S. siderea were noted to be bleaching. At total of 30% of
monitored colonies at French Reef and 9% of monitored colonies at Little
Grecian were experiencing some bleaching.  8% at French Reef and 1% at
Little Grecian were totally bleached.  When these sites were visited again
on September 7th, the condition of the bleached colonies had not changed and
no new bleaching had occurred. 

Temperature readings in degrees Celsius recorded during each site visit were
as follows: 
8/9/05: 
French Reef; 1m: 30.6, 5m: 30.6, 10m: 30.6
Little Grecian: 1m: 31.2, 5m: 30.9
8/17/05: 
French Reef; 1m: 30.9, 5m: 30.8, 10m: 30.9
Little Grecian: 1m: 31.3, 5m: 31.3
9/2/05: 
French Reef; 1m: 29.6, 5m: 29.5, 10m: 29.5
Little Grecian: 1m: 29.7, 5m: 29.4
9/7/05: 
French Reef; 1m: 29.2, 5m: 29.3, 10m: 29.3
Little Grecian: 1m: 29.1, 5m: 29.1

Biscayne National Park Inshore Patch Reefs (Tyler B. Smith)

On September 10th, 2005, A total of eight 10 meter transects were
haphazardly laid at several inshore patch reef sites in Biscayne National
Park.  Three transects in the vicinity of Marker 9, two near Marker 13, and
three in the area of Bache Shoals were conducted.  Coral colonies that were
under the line were recorded and their condition was evaluated. Condition
categories were: okay, slightly pale (lightened), pale (very lightened),
partial bleaching (patches of total bleaching), and bleached (100% w/o
zooxanthellae color). 

Of the colonies measured [89 colonies, 10 species (incl. Palythoa
caribaeorum)] 11% were normal and 89% exhibited some bleaching (30% were
totally bleached and 58% had paling or patchy bleaching).

In the transects, species affected were Agaricia agaracites, Diploria
clivosa, Diploria strigosa, Montastrea annularis, Porites asteroides,
Porites porites, Sidereastrea siderea, Stephanocoenia mechellini and
Palythoa sp. Species unaffected were Dichocoenia stokesii

Outside the transect, species affected were Acropora cervicornis (A. palmata
was not seen at the reefs) and Montastrea cavernosa, Millepora complanata,
M. alcicornis, Erythropodium caribaeorum (encrusting gorgonian) and Briaream
asbestinum. Species that were unaffected included Eusmilia fastigiata.


*****
Inquiries regarding the middle Keys inshore patch reef sites and upper Keys
offshore reef sites may be directed to Marilyn Brandt
(mbrandt at rsmas.miami.edu).

For information regarding the inshore patch reef sites of Biscayne National
Park contact Tyler Smith (tsmith at rsmas.miami.edu). 




Marilyn E. Brandt
National Center for Caribbean Coral Reef Research (NCORE)
Rosenstiel School of Marine and Atmospheric Science (RSMAS)
University of Miami
4600 Rickenbacker Cswy.
Miami, FL 33149
 
Ph. 305.421.4827  Fx. 305.421.4910
www.ncoremiami.org