International Journal of Marine Science, 2016, Vol.6, No.21, 1-20
13
ranged more widely than inshore sites during this time (31-20°C). Significant differences were not identified at the
location or region level for TON (ANOVA; p = 0.166 and p = 0.214 respectively) or ammonium (ANOVA; p =
0.42 and p = 0.06 respectively).
Principal components 1 and 2, despite limited influence on the regional ordination of sites, imparted greater
percentages of variation to the summer environment data-space than PC3. Influential variables along principal
component 1 (20.2%) included factors that contribute to turbidity including Chl a and silicates. Western sites were
0.7 nephelometric turbidity units (NTU) more turbid than eastern sites (ANOVA; p = 0.022) and also significantly
greater in Chl a (ANOVA; p = 0.013). Silicates displayed significant variation at the zone (ANOVA; p = 0.0392)
but not regional level. Variation along PC2 was influenced by SRP, nitrate, and TOC, however significant
variation was not identified for any of these variables at the regional or site level.
Increasing the resolution of temperature data to daily monitoring at a reference inshore and offshore site provided
greater support to these findings. During three years of temperature monitoring (2011-2013) annual mean SWT at
the inshore site, Birthday reef, and offshore site, Acer 24 reef, did not significantly differ (ANOVA p = 0.828);
26.74°C and 26.77°C respectively. Monthly variance in SWT, however was 0.5°C less at Acer 24 (ANOVA p <
0.05). Additionally increased (> 30°C) and decreased (< 23°C) daily SWTs occurred more frequently (55%) at
Birthday reef compared to Acer 24.
3.3 Location-Dependent Shifts in Brightness, a Bleaching Related Characteristic
Fragments of
M. cavernosa
and
P. astreoides
transplanted to Birthday reef displayed significantly fewer signs of
bleaching (i.e. increased brightness) at Birthday reef (ANOVA; p = 2e
-16
), compared to the conspecifics
transplanted to the offshore site, Acer 24 (Figure 10). Although the occurrence of severely bleached corals
(Brightness ≥ 150) was rare, the frequency of a lesser degree of bleaching (101 ≤ Brightness ≥ 149) was
significantly greater at the offshore site, Acer 24. We did not observe a transplant dependent effect on the
brightness of corals when analyzing the total frequency of occurrences at the three brightness ranges. Observing
the quantum yield of photochemical energy conversion (Yield: ΔF/F
m
ˊ) of corals inhabiting each location, we
found significant differences at the species (p = 2.23e
-06
) and site (p = 0.0198) levels during summer months
(Figure 11). During the summer the probability of photons entering photosystem II (PSII) was greater for
P.
astreoides
and colonies of these two species inhabiting Birthday reef. Corals inhabiting Birthday reef did not
display differences in yields between winter and summer.
We observed a seasonal change in the monthly brightness of coral fragments transplanted to Birthday reef, the
inshore site, following the application of a Loess smoothing function (Cleveland and Devlin, 1988). The lightest
shade (greater brightness value) was observed during September and October while the darkest (lower brightness
value) were observed during February and March. Due to the large variance in monthly brightness values between
coral fragments, trigonometric linear regression was applied to determine if a significant trend existed. Changes in
brightness significantly fit a cosine function with 12-month period (ANOVA; p = 0.04), representative of a
significant annual pattern in coral brightness at Birthday reef (Figure 12). A significant cosine pattern was not
observed for corals at Acer 24. Instead, linear regression of coral fragment brightness at this site indicated that
mean brightness values of corals transplanted to this site increased from September 2011 to May 2013. Therefore
these corals became progressively lighter (potentially more bleached) during this period of time.
4 Discussion
The inshore patch reef system of the FKNMS has maintained stable and productive scleractinian coral
communities since the last large scale decreases in coral cover around 1999. The neighboring bank reef
communities experienced even more dramatic losses to coral cover prior to 1999 and have yet to rebound (Lirman
and Fong, 2007; Schutte et al., 2010). Our analysis of the past 16 years of data from CREMP indicates that inshore
reefs continue to support the majority of coral cover in the Lower Florida Keys (Figure 2). Analysis of the 10 reefs
from the CREMP indicated that the inshore patch reef system now accounts for greater than 70% of the coral
