thicket patches are mainly located on the crest of the ridges and are facing generally northwards (Fig. 10.13). The observations made from the submersible
videos corroborate the remotely sensed acoustic data, and thus indicate that the
asymmetric distribution of dense coral thicket patches are a defining characteristic
of the ridges at the Miami Terrace.
Along the Miami Terrace site, the non-random distribution of dense corals is
driven by local hydrodynamics. Bottom current data, recorded continuously by the
AUV for over 24.5 h, indicates a constant southward flowing current, with an
average velocity of 18 cm/s and maximum velocity of 60 cm/s (Fig. 10.14c). Thus
the AUV current data corroborate previous findings of a regional deep countercurrent at the base of the Miami Terrace, flowing in the opposite direction to the
main northward Florida Current (Hurley and Fink 1963; Düing and Johnson 1971;
Neumann and Ball 1970). The southward current flows into the northern sides of
the ridges where most dense coral patches are located. The correlation between
current direction and coral spatial distribution suggests that coral survivorship is
highest on the current-facing sides of the Miami Terrace ridges. We hypothesize
that the current-facing coral colonies intercept a greater number of food particles
than the colonies positioned in the lee of the current (e.g., Messing et al. 1990;
Dorschel et al. 2007). Thus the integrated dataset and spatial analyses presented
here not only provide quantitative information on the distribution of cold-water
corals, but also contribute to hypotheses regarding the environmental parameters
that underlie coral distribution at an ecological scale. Such information is crucial
for predicting where additional cold-water coral habitats most likely exist, and
thus, prioritizing regions for future exploration.
10.4 Conclusions and Recommendations
This chapter described an integrated survey approach for remote sensing coldwater coral fields at regional and local scales. Based on the comparison of different
mapping tools, it is clear that high-resolution (0.5–3 m) AUV-generated maps are
crucial for characterizing the detailed distribution of coral ridges and mounds in
the Straits of Florida. However, AUVs are costly to operate and have relatively
narrow swaths. Thus, to maximize survey cost effectiveness, reconnaissance
mapping at regional scales followed by deployment of the AUV in identified areas
of interest is highly recommended. Hull-mounted multi-beam systems are ideal for
reconnaissance surveys given their wide swaths and relatively low operating costs.
In unexplored, potential cold-water coral habitats, the EM120 is recommended
given that its swath width, survey speed, and thus, total area covered per survey are
greatest. In areas where cold-water coral features have previously been documented, the EM1002 system is recommend for reconnaissance because it provides
a moderate level of resolution while still covering a relatively large area.
In identified areas of interest, the combination of AUV-generated maps with
ground-truthing data enables the quantitative assessment of cold-water coral
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T. B. S. Correa et al.
videos corroborate the remotely sensed acoustic data, and thus indicate that the
asymmetric distribution of dense coral thicket patches are a defining characteristic
of the ridges at the Miami Terrace.
Along the Miami Terrace site, the non-random distribution of dense corals is
driven by local hydrodynamics. Bottom current data, recorded continuously by the
AUV for over 24.5 h, indicates a constant southward flowing current, with an
average velocity of 18 cm/s and maximum velocity of 60 cm/s (Fig. 10.14c). Thus
the AUV current data corroborate previous findings of a regional deep countercurrent at the base of the Miami Terrace, flowing in the opposite direction to the
main northward Florida Current (Hurley and Fink 1963; Düing and Johnson 1971;
Neumann and Ball 1970). The southward current flows into the northern sides of
the ridges where most dense coral patches are located. The correlation between
current direction and coral spatial distribution suggests that coral survivorship is
highest on the current-facing sides of the Miami Terrace ridges. We hypothesize
that the current-facing coral colonies intercept a greater number of food particles
than the colonies positioned in the lee of the current (e.g., Messing et al. 1990;
Dorschel et al. 2007). Thus the integrated dataset and spatial analyses presented
here not only provide quantitative information on the distribution of cold-water
corals, but also contribute to hypotheses regarding the environmental parameters
that underlie coral distribution at an ecological scale. Such information is crucial
for predicting where additional cold-water coral habitats most likely exist, and
thus, prioritizing regions for future exploration.
10.4 Conclusions and Recommendations
This chapter described an integrated survey approach for remote sensing coldwater coral fields at regional and local scales. Based on the comparison of different
mapping tools, it is clear that high-resolution (0.5–3 m) AUV-generated maps are
crucial for characterizing the detailed distribution of coral ridges and mounds in
the Straits of Florida. However, AUVs are costly to operate and have relatively
narrow swaths. Thus, to maximize survey cost effectiveness, reconnaissance
mapping at regional scales followed by deployment of the AUV in identified areas
of interest is highly recommended. Hull-mounted multi-beam systems are ideal for
reconnaissance surveys given their wide swaths and relatively low operating costs.
In unexplored, potential cold-water coral habitats, the EM120 is recommended
given that its swath width, survey speed, and thus, total area covered per survey are
greatest. In areas where cold-water coral features have previously been documented, the EM1002 system is recommend for reconnaissance because it provides
a moderate level of resolution while still covering a relatively large area.
In identified areas of interest, the combination of AUV-generated maps with
ground-truthing data enables the quantitative assessment of cold-water coral
278
T. B. S. Correa et al.