International Journal of Marine Science, 2016, Vol.6, No.21, 1-20
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hyper and hypothermic seawater temperature events experienced (Soto et al., 2011), increased dissolved inorganic
nitrogen, soluble reactive phosphorus, and chlorophyll a, increased turbidity, greater macro algal biomass
(Lapointe et al., 2004), and closer proximity to anthropogenic sources of stress (Ginsburg et al., 2001). Several
hypotheses have been proposed regarding the proliferation of inshore reefs and the deterioration of offshore reefs
including (1) continued persistence of large fecund colonies in inshore reef zones resulting in increased inshore
recruitment, (2) diet supplementation from increased turbidity and nutrient concentration as a means to alleviate
stressful near-shore conditions, and (3) differences in seawater temperature variance resulting in a wider
temperature range allowing corals inhabiting inshore reefs the opportunity to acclimate to future changes in
seawater temperature (Soto et al., 2011).
Recruitment does not appear to be responsible for the differences in coral abundance between adjacent inshore
and offshore sites. The current state of knowledge emphasizes the importance of local recruitment for the
maintenance of coral population abundance (Mumby et al., 2008; Steneck et al., 2009) and low frequency
immigrant settlement promotes genetic diversity (Sammarco et al., 1989; Noreen et al., 2009). Co-implementation
of larval dispersal models, genetic population connectivity (Foster et al., 2012) and sensitive identification and
quantification of recruits (Schmidt-Roach et al., 2008; Hsu et al., 2014) has increased the accuracy of coral
recruitment estimation. In the Florida Keys annual recruitment at inshore and offshore reefs is highly variable
(Moulding, 2005; Shearer and Coffroth, 2006) and not a locally defining characteristic (Miller et al., 2000). Post
settlement processes and stress (i.e. hypotheses 2 and 3) are therefore more likely correlated to the difference in
reef growth and community structure observed.
We hypothesize that corals inhabiting inshore reef zones are able to respond to a wider range of stress levels as a
consequence of frequent occurrences of non-lethal stress levels characteristic of this zone. The history of abiotic
and biotic stress experienced by a reef affects the inhabitants response, growth, selection for resistant individuals,
and in the case of corals establishment of resistant symbionts following aberrant levels of stress (Haslun et al.,
2011; Palumbi et al., 2014). Gradients of increased levels of abiotic factors associated with stress extend from
offshore reefs to inshore reefs in the Florida Keys (Lapointe et al., 2004) and supporting this hypothesis a negative
correlation exists between both coral cover and colony size, as well as distance from shore (Lirman and Fong,
2007). The stress level experienced by the organism is most likely not a reflection of any one stressor but rather
the cumulative effect of stressors present. The level of one factor may provide a refuge from a factor the organism
is more susceptible to, decreasing the severity of a potentially lethal stressor. For example, increases in
chlorophyll a may occur concomitantly with increases in turbidity (Ziemann et al., 1992). Increased turbidity may
in-turn, decrease photic stress on scleractinian corals during increased water temperatures resulting in an overall
decreased level of stress.
Identification of abiotic factors contributing to the community level differences in abundance and size of corals
inhabiting inshore and offshore reefs is critical to the management of this habitat (Lirman and Fong, 2007). This
study integrated and applied coral cover data from the coral reef environmental monitoring project (CREMP),
environmental data from the water quality monitoring project (WQMP), and coral community and environmental
data from ongoing research projects coordinated by our lab group to describe the asymmetry of coral cover
currently observed between the inshore patch reef system and offshore bank reef system. We identify four coral
species with differential abundances within the nearshore and offshore zones, the study of which may increase our
understanding of the juxtaposition in coral growth between these environments. To provide a more complete
understanding of the community dynamics of a symbiotic organism we also observed the seasonal photosynthetic
competence (symbiont photo-physiology) and colony color of the identified species at two sites, one
representative of an inshore patch reef and the other representative of an offshore bank reef, over a two-year
period. From this information the seasonal response strategy of each species was determined.
