ES-4

Site Descriptions

The nine monitoring sites ultimately selected are shown in Fig. ES.1, and characteristics

are summarized in Table ES.1. Each site was defined as a circular area of a certain

diameter. Diameters of the nine sites were determined through an analysis of the

bathymetric data collected during Cruise 1A. Resulting site diameters ranged from 100

to 200 m. Physical oceanographic moorings and epibiont recruitment arrays

(biomoorings) were placed on areas of flat bottom near certain sites. Fig. ES.2 shows an

example of a side-scan image of Sites 1 and 3 with adjacent moorings.

Fig. ES.2. Side-scan sonar mosaic showing the setting of Sites 1 and 3.

Site diameters are 200 m for Site 1 and 150 m for Site 3.

Current meter mooring locations are indicated by flags and

the biomooring location is indicated by a triad.


























Fig. 2.3. Side-scan sonar mosaic showing the setting of Sites 1 and 3. Site diameters

are 200 m for Site 1 and 150 m for Site 3. Current meter mooring locations

are indicated by flags and the biomooring location is indicated by a triad.

Fig. 2.4. Side-scan sonar mosaic showing the setting of Site 2. Site diameter is 120 m.

There were no current meters or biomoorings located near this site.

0 100 200 METERS

0 100 200 METERS

15
Fig. 2.5. Side-scan sonar mosaic showing the setting of Site 4. Site diameter is 140 m.

Current meter mooring location is indicated by a flag and biomooring

locations are indicated by triads.

Fig. 2.6. Side-scan sonar mosaic showing the setting of Sites 5 and 6. Site diameters

are 160 m for Site 5 and 150 m for Site 6. Current meter mooring locations

are indicated by flags and the biomooring location is indicated by a triad.

0 100 200 METERS

0 100 200 METERS

16
Fig. 2.7. Side-scan sonar mosaic showing the setting of Site 7. Site diameter is

200 m. There were no current meters or biomoorings located near this site.

Fig. 2.8. Side-scan sonar mosaic showing the setting of Sites 8 and 9. Site diameters

are 100 m for Site 8 and 150 m for Site 9. Current meter mooring location is

indicated by a flag and the biomooring location is indicated by a triad.

Site 8

Site 7

0 100 200 METERS

0 100 200 METERS

17













Fig. 3.3. TAMU2

side-scan sonar mosaic of Megasite 1, showing monitoring Sites 1-3 (small boxes). Vertical stripes are individual

trackline side-scan sonar records pieced together to make the mosaic. Dark areas are high acoustic return (backscatter),

whereas light areas are low backscatter. UTM plot with axes labeled in meters.

Site 2

Site 1

Site 3

32
Fig. 3.4. Megasite 1 sonar mosaic interpretation showing mounds (black) and high-backscatter areas (gray). Plot is in UTM

coordinates.

3.258

3.257

3.256

3.255

4.40 4.42 4.44

x105 m

x10

6 m

33
Fig. 3.5. Example of high-backscatter "tail" southwest of a mound in Megasite 1 and associated

erosional gully. (Top) Chirp sonar subbottom profile showing gully approximately 3-m

deep and 150 m across. (Bottom) High-backscatter "tail" to southwest of mound. Dark

areas indicate high backscatter and light represents low backscatter. Acoustic

illumination is directed away from shiptrack (vertical line at right). Note: The two

examples are from different locations because the subbottom profiler must pass directly

over the tail feature to image it, but the side-scan sonar does not image well directly

beneath the sonar.

34


Fig. 3.7. TAMU2

side-scan sonar mosaic of Megasite 2, showing monitoring Site 4 (small box). Conventions as in Fig. 3.3.

Site 4

37
Fig. 3.8. Megasite 2 sonar mosaic interpretation showing mounds (black) and high-backscatter areas (gray). Plot is in UTM

coordinates.

4.20 4.22 4.24 4.26 4.28

3.248

3.246

3.244

3.242

x10

m

6

X10 m

5

38

Fig. 3.10. TAMU2

 side-scan sonar mosaic of Megasite 3, showing monitoring Sites 4 and 6 (small boxes). Conventions as in Fig. 3.3.

Site 6

Site 5

0

0

40
Fig. 3.11. Megasite 3 sonar mosaic interpretation showing mounds (black) and high-backscatter areas (gray). Plot is in UTM

coordinates.

4.00 4.02 4.04

3.254

3.252

3.250

x10

m

6

x10 m

5

41


Fig. 3.13. TAMU2

 side-scan sonar mosaic of Megasite 4. Conventions as in Fig. 3.3.

44


Fig. 3.15. TAMU2

 side-scan sonar mosaic of Megasite 5, showing monitoring Sites 7-9 (small

boxes). Conventions as in Fig. 3.3.

Site 8

Site 9

Site 7

47
Fig. 3.16. Megasite 5 sonar mosaic interpretation showing mounds (black) and high-backscatter areas (gray). Plot is in UTM

coordinates.

3.69 3.71 3.73 3.75

3.238

3.236

3.234

3.232

x10

m

6

x10 m

5

48
Fig. 3.17. Bathymetry of Monitoring Site 1. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

Fig. 3.18. Side-scan sonar image of Monitoring Site 1. Circle indicates the boundary of ROV

seafloor observations.

1 m

49


Fig. 3.20. Bathymetry of Monitoring Site 2. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

1 m

Fig. 3.21. Side-scan sonar image of Monitoring Site 2. Circle indicates the boundary of ROV

seafloor observations.

52


Fig. 3.23. Bathymetry of Monitoring Site 3. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

Fig. 3.24. Side-scan sonar image of Monitoring Site 3. Circle indicates the boundary of ROV

seafloor observations.

1 m

55

Fig. 3.26. Bathymetry of Monitoring Site 4. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

Fig. 3.27. Side-scan sonar image of Monitoring Site 4. Circle indicates the boundary of ROV

seafloor observations.

1 m

57


Fig. 3.29. Bathymetry of Monitoring Site 5. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

1 m

Fig. 3.30. Side-scan sonar image of Monitoring Site 5. Circle indicates the boundary of ROV

seafloor observations.

60


Fig. 3.32. Bathymetry of Monitoring Site 6. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

1 m

Fig. 3.33. Side-scan sonar image of Monitoring Site 6. Circle indicates the boundary of ROV

seafloor observations.

63

Fig. 3.35. Bathymetry of Monitoring Site 7. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

1 m

Fig. 3.36. Side-scan sonar image of Monitoring Site 7. Circle indicates the boundary of ROV

seafloor observations.

65


Fig. 3.38. Bathymetry of Monitoring Site 8. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

1 m

Fig. 3.39. Side-scan sonar image of Monitoring Site 8. Circle indicates the boundary of ROV

seafloor observations.

68


Fig. 3.41. Bathymetry of Monitoring Site 9. Contours shown at 1-m intervals. Circle

indicates the boundary of ROV seafloor observations.

Fig. 3.42. Side-scan sonar image of Monitoring Site 9. Circle indicates the boundary of ROV

seafloor observations.

1 m

71




Fig. 3.46. Side-scan sonar images showing individual "unit" mounds (Top) and a composite

mound (Bottom). Dark areas represent high backscatter and light areas are low

backscatter. Acoustic illumination is from the shiptrack (vertical line).

76

Fig. 3.47. Side-scan sonar images showing complex, irregular mounds from Megasite 2.

Conventions as in Fig. 3.46.

78
Fig. 3.48. Side-scan sonar images showing smooth-top mounds. (Top) Example from

Megasite 3. Note the smooth top shows two levels. (Bottom) Large, flat-topped

mound from Megasite 1. Monitoring Site 1 is located on the northeast edge of the

top. Conventions as in Fig. 3.46.

79















































130

Fig. 6.2. Current meter mooring locations at Site 1 (indicated by flags). Mooring 1A was in

place throughout the program (periods 1–8), whereas 1B and 1C were present only

for periods 1–4. Triad indicates biomooring (see Chapter 10).

Fig. 6.3. Current meter mooring location at Site 4 (indicated by flag). Mooring 4A was in

place throughout the program (periods 1–8). Triads indicate biomoorings (see

Chapter 10).
131

Fig. 6.4. Current meter mooring locations at Site 5 (indicated by flags). Mooring 5A was in

place throughout the program (periods 1–8), whereas moorings 5B and 5C were

present only for periods 4–8. Triad indicates biomooring (see Chapter 10).

Fig. 6.5. Current meter mooring location at Site 9 (indicated by flag). Mooring 9A was in

place throughout the program (periods 1–8). Triad indicates biomooring (see

Chapter 10).



















































































































Fig. 7.4. Distribution of Ulosa sp., unidentified Rhodophyta, orange amorphous Porifera, amorphous indistinct 

Corallinaceae, and unidentified Bryozoa according to location on hard bottom features. Bars indicate all groups combined, using data combined from all sites with surveys as replicates.

01234567

Surrounding

Seafloor Base Side Top Edge Top In

Ulosa sp.Rhodophyta, unidentifiedPorifera, orange amorphousPorifera, amorphous indistinctCrinoideaCorallinaceae

Bryozoa, unidentified

Mean Percent Cover

Location on Feature























































Fig. 9.1. Substrate classifications. A. Vertical outcrop, thick, silty veneer and large-scale

perforation with medium surface roughness. B. Mounded outcrop, moderate silty

veneer and no sand-fill.

A.

B.

304
Fig. 9.2. Substrate classifications. A. Fine sediment as thick, silty veneer on outcropped surface.

B. Coarse sediment as sandy fill with near-complete burial of outcropped surface.

A.

B.

305
Fig. 9.3. Substrate classifications. A. Combination of fine, coarse, and rubble sediment on area

of no outcropping. B. Outcropping with high surface roughness and moderate silty

veneer.

A.

B.

306


Fig. 9.4. Overview of study sites discussed in this chapter.

309
Fig. 9.5. Gorgonian orientations and mean directional water flow at Site 1. Clockwise from

upper left, the panels show the locations and orientations of sea fan colonies and site

bathymetry (contours in meters), a circular histogram of orientation frequencies, and

mean flow recorded at Mooring 1C4m above bottom and 16 m above bottom.

2

2

2 2

4

4

4 4

6

6

6 6

8

8

8 8

10

10

10 10

12

12

12 12

14

14

14 14

0°

90°

180°

270°

Site 1

Current Meter 1C 16 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0.6

0.8

1.0

1.2

0

90

180

270

10

20

30

40

50

60

70

80

100

110

120

130

140

150

160

190 170

200

210

220

230

240

250

260

280

290

300

310

320

330

340

350

Current Meter 1C 4 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0

90

180

270

20

10

30

40

50

60

70

80

100

110

120

130

140

150

160

190 170

200

210

220

230

240

250

260

280

290

300

310

320

330

340

350

310
Fig. 9.6. Gorgonian orientations and mean directional water flow at Site 3. Clockwise from

upper left, the panels show the locations and orientations of sea fan colonies and site

bathymetry (contours in meters), a circular histogram of orientation frequencies, and

mean flow recorded at Mooring 1B4m above bottom and 16 m above bottom.

Site 3

2

2

2 2

4

4

4 4

6

6

6 6

8

8

8 8

10

10

10 10

12

12

12 12

14

14

14 14

0°

90°

180°

270°

Current Meter 1B 4 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0.6

0.8

1.0

1.2

0

90

180

260

10

20

30

40

50

60

70

80

100

110

120

130

140

150

160

190 170

200

210

220

230

240

250

270

280

290

300

310

320

330

340

350

Current Meter 1B 16 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0.6

0.8

1.0

1.2

0

90

180

270

10

20

30

40

50

60

70

80

100

110

120

130

140

150

160

190 170

200

210

220

230

240

250

260

280

290

300

310

320

330

340

350

311
Fig. 9.7. Gorgonian orientations and mean directional water flow at Site 5. Clockwise from

upper left, the panels show the locations and orientations of sea fan colonies and site

bathymetry (contours in meters), a circular histogram of orientation frequencies, and

mean flow recorded at Mooring 5C 16 m above bottom and Mooring 5B 16 m above

bottom.

2

2

2 2

4

4

4 4

6

6

6 6

8

8

8 8

10

10

10 10

0°

90°

180°

270°

Site 5

Current Meter 5C 16 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0.6

0.8

1.0

1.2

250

10

20

30

40

50

60

70

80

100

110

120

130

140

150

160

190 170

200

210

220

230

240

260

0

90

180

270

280

290

300

310

320

330

340

350

Current Meter 5B 16 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0.6

0.8

1.0

1.2

0

90

180

270

10

20

30

40

50

60

70

80

100

110

120

130

140

150

160

190 170

200

210

220

230

240

250

260

280

290

300

310

320

330

340

350

312
2

2

2 2

4

4

4 4

6

6

6 6

8

8

8 8

10

10

10 10

12

12

12 12

14

14

14 14

0°

90°

180°

270°

Site 7

Fig. 9.8. Gorgonian orientations and mean directional water flow at Site 7. Left panel shows the locations and orientations of sea

fan colonies and site bathymetry (contours in meters). Right panel shows a circular histogram of orientation frequencies.

Mean flow is shown in Fig. 9.9.
Fig. 9.9. Gorgonian orientations and mean directional water flow at Site 9. Clockwise from

upper left, the panels show the locations and orientations of sea fan colonies and site

bathymetry (contours in meters), a circular histogram of orientation frequencies, and

mean flow recorded at Mooring 9A4m above bottom and 16 m above bottom.

2

2

2 2

4

4

4 4

6

6

6 6

8

8

8 8

10

10

10 10

12

12

12 12

14

14

14 14

0°

90°

180°

270°

Site 9

Current Meter 9A 4 M.A.B.

Mean flow (cm/sec)Vs Direction

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

250

260

270

280

290

300

310

320

330

340

350

0.2

0.4

0.6

0.8

1.0

1.2

Current Meter 9A 16 M.A.B.

Mean flow (cm/sec)Vs Direction

0.2

0.4

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

250

260

270

280

290

300

310

320

330

340

350

0.6

0.8

1.0

1.2

314




















335

Fig. 10.3. TAMU2 side-scan sonar mosaic of Site 1. Current meter mooring locations

are indicated by flags. Biomooring location is indicated by triad.

Fig. 10.4. TAMU2

 side-scan sonar mosaic of Site 4. Current meter mooring location is

indicated by flag. Biomooring locations are indicated by triads.
336

Fig. 10.5. TAMU2 side-scan sonar mosaic of Site 5. Current meter mooring locations

are indicated by flags. Biomooring location is indicated by triad.

Fig. 10.6. TAMU2 side-scan sonar mosaic of Site 9. Current meter mooring location is

indicated by flag. Biomooring location is indicated by triad.














































Fig. 11.1. Vertical relief (range of photographic station depths) at each site.

Vertical Relief (Range of Photo Depths within Site)

Site

1 2 3 4 5 6 7 8 9

Range of Photo Depths (m)

(height above deepest photo location)

0

2

4

6

8

10

12

14

16

18

20

West

West

West

East

East

East

Central

Central

Central

Low Relief Sites

Medium Relief Sites

High Relief Sites

9 6 3 8 4 2 7 5 1

Top of Benthic Nepheloid Layer 

(e.g., at Sites 5 and 9)

383