EPA's Vessel General Permit and Small Vessel General

even slightly more acidic sea water (thereby eroding the shells which form coral hard
parts)(Anthony et al. 2008, De’ath et al. 2009, Wei et al. 2009, Crawley et al. 2010).
Acidification also reduces the thermal tolerance of corals, meaning that bleaching can occur at
lower temperatures (Anthony et al. 2008). Hurricanes can cause wide-scale inhibition of
recruitment in years following storm passage as well as physical damage to coral colonies
themselves (Mallela and Crabbe 2009).
White band disease is thought to be the major factor responsible for the rapid loss of Atlantic
Acropora due to mass mortalities. White band disease is the only coral disease to date that has
been documented to cause major changes in the composition and structure of reefs (Humann and
Deloach 2003). In 2011, Sutherland et al. (2011) were able to definitively identify human waste
as a cause for white pox disease in elkhorn corals.
Reductions in long-term water clarity can also reduce the coral photosynthesis to respiration ratio
(P/R ratio). Telescnicki and Goldberg (1995) and Yentsch et al. (2002) found that elevated turbidity
levels did not affect gross photosynthetic oxygen production, but did lead to increased respiration
that consumed the products of photosynthesis with little remaining for coral growth.
Unfortunately, since staghorn corals are broadcast spawners once colonies become rare, the
distance between colonies may limit fertilization success and there is substantial evidence to
suggest that sexual recruitment of staghorn corals is currently compromised. Reduced colony
density in some areas is compounded by low genotypic diversity, indicating that fertilization
success and consequently, larval availability, is likely reduced. This can have long-term
implications for genetic variability of remaining colonies due to the reduced potential for
exchange of genetic material between populations that are spatially further apart (Bruckner
2002).
Data on levels of genetic diversity and population structure suggest that there is a population
structure among islands, and even over spatial scales of no more than 20 km, as well as varying
degrees of genetic diversity within local populations (Lirman 2002, Vollmer 2002). For
instance, one clone of staghorn coral may dominate areas up to 10 m 2 in size and the clones are
generally spatially discrete with larval exchange between staghorn populations as close as 2 to 15
km being extremely limited, suggesting that larval sources need to be conserved on a very small
spatial scale (Baums et al. 2005, Vollmer and Palumbi 2007).
Anthropogenic threats
Threats to staghorn coral are exacerbated further by eutrophication, sedimentation, and
anchoring, which degrade coral condition and increase synergistic stress effects (e.g. bleaching).
Excessive sedimentation can smother corals and increased nutrient availability promotes algal
growth on corals, leading to light blockage to zoozanthelle and death of corals (Acropora
Biological Review Team 2005). Although reefs in the Florida Keys currently experience about
10% macroalgal cover or less, much of the wider Caribbean Sea may exceed 20% cover (Bruno
2008), inhibiting and reducing coral survival. Global warming is also projected to have negative
impacts on coral survival through coral bleaching, increased storm intensity, and reduced
calcification (Acropora Biological Review Team 2005).
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