STUDY FOR MITIGATION OF A
S.E. FLORIDA U.S.A. CORAL REEF DAMAGED BY THE GROUNDING OF A NUCLEAR SUBMARINE
R.E. Dodge*, R.E. Spieler*, D.S. Gilliam*, T.P. Quinn*,
E.A. Glynn*, K. Banks+, L. Fisher+, D. Stout+, W. Jaap#,
* National Coral Reef Institute, Nova Southeastern University Oceanographic Center, 8000 North Ocean Drive, Dania Beach, FL, USA 33004
E-mail address: firstname.lastname@example.org
+ Broward County Department of Planning and Environmental Protection, 218 S.W. 1st Avenue, Ft. Lauderdale, FL 33301
# Florida Fish and Wildlife Commission, Florida Marine Research Institute, 100 8th Ave, S.E., St. Petersburg, FL 33701
The United States Submarine Memphis (Figure 1) ran aground in approximately 10 meter depth on a coral reef off southeast Florida (Figure 2) February
25, 1983. Extensive physical damage to the reef substrate and injury to the coral community were attributed to the initial grounding and subsequent attempts to tree the submarine from the impacted reef (Figures 3 and 4). The impact of
the grounding was assessed, and the area of damage was determined through field and photographic studies.
An impacted area of 2,310 m² was assessed with 1,205
m² having been totally destroyed (Figures 3 and 4). In 1997, the State of Florida was awarded a settlement
of $750,000 by the Federal government for environmental damages caused by the submarine grounding. A plan to perform hypothesis testing
of restoration techniques was developed and initiated.
Using artificial reefs as experimental platforms, we are examining three restoration strategies: 1)
the potential of enhancing coral recruitment through the use of coral larval
attractants, 2) the effect of reef structure on the associated fish assemblages, and 3) the interaction between fish assemblages and coral recruitment and
|Figure 3. Trench
hole (3 m depth) excavated by the submarine's propeller during
attempts to free itself from
|Figure 4. Entry
gouge approximately four years after the grounding.
One hundred and sixty small artificial reef modules (Reef Balls™) will be deployed in 11 m of water on a sand flat between reef hacks adjacent to the
U.S.S. Memphis grounding sit (Figure 5). The Reef Balls will be organized into 40, 4-module reef units (quad) in a square configuration having approximately 4 m sides (Figure 6). The separation of individual Reef Balls (2 m) is
judged sufficient to avoid interaction effects between Reef Balls in terms
of coral settlement, but close enough for the 4 balls to function as a single
reef unit in terms of fish recruitment. Each quad will be located a minimum of 30 m from
any hardbottom or other quads.
Large scale configuration of Reef Ball deployment. Each
circle represents 30 m diameter. Each X represents one
quad of Reef Balls. the Reef Balls will be deployed
between two reef tracks.
Model representation of a Reef Ball quad. Each individual
Reef Ball will have 2 m separation from the other Reef Balls in
Settlement plates on each Reef Ball (Figure T) will be used to test hypotheses on enhancing coral recruitment through the use of larval attractants. The settlement plates attached to each Reef Ball wilt ire treated with a potential attractant (Iron, algal extract, coral transplants) and compared with control plates (no attractant). Coral transplants will
be 4' cores drilled from large donor colonies (Figures 8 and 9). Eighty coral cores will be transplanted onto the Reel Bell modules (forty cores of each of two different species). Control corals occurring on the natural reef, and of comparable she to the donor corals, will be monitored
for comparison of growth and mortality.
Attractants: Each individual Reef
Ball in a quad will incorporate one of four different attractants on the settlement
Iron additive « »
Coral transplants « » Control
7. Reef Ball with settlement plates. Each Reef Ball will have
two adjoining settlement plates. Settlement plates have smooth and rough
surfaces to investigate the effects of surface texture on the
preferential settlement of coral recruits. Each individual Reef
Ball in a quad will incorporate one of four different attractants on the
settlement plates: iron additive, algal extract, coral transplant, or
|Figure 8. Coring
donor corals for transplantation. Eighty coral cores will be transplanted onto
the Reef Ball modules (forty cores of each of two different
|Figure 9. Transplant
Reef Balls will hold one core of each species (Montastrea
cavernosa or M. faveolata and Diploria clivosa). Coral
transplants will be placed in the pre-fabricated transplant holes
adjacent to the settlement plates (yellow arrow).
Coral Transplantation and Monitoring:
At quarterly intervals the donor corals, coral transplants, and control corals will be visually assessed to provide information on
individual colony health, growth, and mortality.
The 40 quads will be divided into 4 different levels of structural complexity to test the hypothesis that multiple refuge
size and the resultant diverse fish assemblages may affect coral recruitment, survival, and growth. One set of 10 quads will have the void space of all the Reef
Balls filled with large refuge structure (Figure 10). One set will have the void spaces of all filled with small refuge structure.
Another set will be mixed and have one Reef Ball empty, one with large refuge, and the last two with small
refuge. The final set will have the void space of all the Reef Balls empty. The assemblage or fishes (species, number, and size) associated with each quad will be recorded every three months by visual census (Figure
Complexity: Each type of
fill will be used for 10 quads.
- Large fill -
4 concrete blocks to each Reef Ball of the quad.
- Small fill -
¾" plastic mesh in each Reef Ball of the quad.
- Mixed fill - 1 Reef
Ball of the quad with blocks, 1 empty and 2 with mesh.
- No fill -
all 4 Reel Balls of the quad are empty.
|Figure 10. Inside
Ball with large fill complexity.
|Figure 11. Diver
conducting a fish survey on a Reef Ball displaying structural
complexity of large refuge size.
Artificial reefs are commonly used to provide structure to damaged reef areas.
This project has been designed to use artificial reefs to not only mitigate
for lost reef structure but to provide experimental platforms to examine several restoration strategies.
The examination of these strategies will aid in making reef restoration decisions that involve: 1) the potential enhancement of coral recruitment through the use of
coral larval attractants, 2) the effect of reef structure on fish assemblages, and 3) the
interaction between fish assemblages and coral recruitment and survival.