\' . ECHO I CRUISE REPORT F. N. Spiess R. Hessler G. Wilson M. Weydert P.Rude Sponsored by National Science Foundation DAR-80-15593 and National Oceanic and Atmospheric Administration No. 83-SAC-00659 Reproduction in whole or in part is permitted for any purpose of the U.S. Government MARINE Document cleared for public release and sale; its distr ibution is unlimited 6 January 1984 SID REFERENCES 84-3 PHYSICAL LABORATORY of the Scripps Institution of Oceanography San Diego, California 92152
Transcript
\' .
ECHO I CRUISE REPORT
F. N. Spiess R. Hessler G. Wilson
M. Weydert P.Rude
Sponsored by National Science Foundation
DAR-80-15593 and
National Oceanic and Atmospheric Administration No. 83-SAC-00659
Reproduction in whole or in part is permitted for any purpose of the U.S. Government
MARINE
Document cleared for public release and sale; its distribution is unlimited
6 January 1984
SID REFERENCES 84-3
PHYSICAL LABORATORY of the Scripps Institution of Oceanography
San Diego, California 92152
MPL-U-78.83
UNNERSITY OF CAlJFORNIA, SAN DIEGO MARINE PHYSICAL LABORATORY OF THE
SCRIPPS INSTITUTION OF OCEANOGRAPHY SAN DIEGO. CAlJFORNIA 92132
ECHO I CRUISE REPORT
F. N. Spiess R. Hessler G. Wilson
M. Weydert P. Rude
Sponsored by National Science Foundation
DAR-80-15593 and
National Oceanic and Atmospheric Administration No. 83-SAC-00659
SIO REFERENCE 84-3
6 January 1984
Reproduction in whole or in part is permitted for any purpose of the U.S. Government
Document cleared for public release and sale; its distribution is unlimited
K. M. WATSON. Director Marine Physical Laboratory
i
ECHO I CRUISE REPORT
F. Spiess, R. Hessler, G. Wilson, M. Weydert, P. Rude
Echo I expedition, carried out in June, 1983 using RN Melville, was funded jointly by NSF and NOAA to carry out acoustic backscatter measurements in a manganese nodule area and to investigate the environmental impact of use ot a preliminary model ot a mining device. The site was located at 140 -40'N, 1250 25'W, near DOMES site C. Data sources were the MPL Deep Tow system (primarily precision sounding, Side-looking sonar and photography) with a newly added acoustic backscatter measuring system operating at 7 discrete frequencies between 4* and 160 kHz, and a box corer operated by R. Hessler's group. All observations and samples were tied together geographically by a sea floor acoustic transponder network. A Seabeam multibeam echo sounder survey, including quantitative measurement ot relative reflectivity of the bottom, had been made as a part ot this program just the month before. The dredge tracks were mapped with side-looking sonar and areas having differing nodule coverage were delineated using camera and TV. Sixteen successive successful box core samples were collected in the mining area and a control site and will be analyzed to determine whether there has been appreciable biological impact from the dredging operations. Near the end of the time on station the deep tow survey was terminated when the tow wire parted and the vehicle went to the bottom in 4500 m of water. Thanks to prior development of navigation and retrieval equipment and operational experience, the vehicle was recovered intact.
Introduction Expedition Echo I, F.N. Spiess and R.R. Hessler, co-chief scientists was sponsored
jointly by the National Science Foundation (Grant No. DAR-80-15593, Spiess, P.I.) and the National Oceanic and AtmospheriC Administration (Contr. No. 83-SAC-00659, Hessler and Spiess, P.Ls). Carried out on board R/V Melville in June, 1983 it had two primary goals, with a single integrated observation and sampling program which contributed to both. The National Science Foundation grant was made to support a study of acoustic backscattering from manganese nodule fields with associated detailed documentation of the nature of the sea floor by means of observations with the MPL Deep Tow system and bottom sampling. Early planning was concerned with this portion only. It was thus determined that the vicinity of DOMES (Deep Ocean Mining Environmental Study) site C (150 N, 125OW) (Piper et al ., 1979a, b) would be the best site to carry out that work. FollOwing this decision it was recognized that OMA (Ocean Mining Associates) had carried out a trial mining operation near that site, and NOAA became interested in determining the nature of any environmental impact which the mining might have had. Since both programs implied a substantial detailed sea floor observational program and the additional special activities r.equired for each. (acoustic backscatter measurements and an intensive box coring program respectively) were of mutual interest it was agreed that the station time would be extended and the overall working time shared.
1
The Acoustic Backscatter program has as its goal the determination of the extent to which the principal characteristics of manganese nodule fields (nodule numbers and size distribution) can be determined from simple acoustic observations made over a wide frequency range. Although the NSF funding only covered construction of equipment to operate at relatively low (5 to 20 kHz) and ·high (over 100 kHz) frequencies. the Office of Naval Research provided additional support to till the midfrequency gap with the understanding that the entire system would be used on subsequent ONR funded expeditions to document acoustic backscattering in other tYPical ocean fioor environments. The frequencies used were 4.5, 9. 15.28. 60. 110. and 160 kHz. Special transducers for these frequencies were built and mounted to transmit fan beams aft from the vehicle. Calibrations were made at the Naval Ocean Systems Center Transdec facility. The backscatter system was integrated with the normal Deep Tow equipment (Spiess and Lonsdale. 1982) so that simultaneous side looking sonar. precision echo sounder and acoustic navigation observations could be made and so that. on the same lowering. photo runs could be made as well. The acoustic data were rectified. sampled digitally at a 2 kHz rate and stored on magnetic tape for analysis ashore. The expedition objectives for this portion of 'the program were thus to obtain acoustic backscatter data over nodule areas having -different styles of coverage and to document with precision echo sounding. photography and bottom sampling, the nature of the exact locations from which the backscatter .datawere obtained.
The Min'i:ng Impru:t portion of the study was designed primarily to determine the nature of the physical and biological disturbances which the prototyp'e mining device had produced. if any. To accomplish this it was necessary to re-Iocate and map out the locations of the mining dredge tracks (a side-looking sonar and transponder navigation tas~).photograph them and then carry out a -sampling program using relay transponder navigated (Bo_egeman et a1. . 1972) box cores. Here the primary goal ·of sampling was to learn ,waet'her -.there w.e-r.e _ faunal differences evident between the sediments close to the disturbed zones and those several kilometers away. A useful by-:product was the sampling of the nodules themselves. both as a contribution to ground truth for the backscatter work and as a basis for studying biological materials UVing on the nodules.
n. Prior Work in the Area This general region had been the subject of 2 major investigations and one
operation explicitly planned to provide base data for our work. The USGS work at the DOMES sites (Bischoff and Piper, 1979) had concentrated on a nearby location and its existence. plus logistic considerations. led us to choose this area to carry out the backscatter work. OMA had worked this specific site intensively with TV. narrow beam echo sounding and dredging over a period of several years. OMA personnel were very helpful to us, providing their topographic data, bottom photographs, maps of their approximate prototype mining tracks and transponder-locations as well as descriptions of the nature of the area. They indicated that we would undoubtedly find substantial variability in nodule sizes and coverage within 10 miles of their primary work area which would be the focus of the NOM sponsored aspect of the work. This was encouraging since it indicated that we would probably be able to carry out the entire field program within one reasonable sized transponder array.
It was particularly fortunate , however. that R/V Thomas Washington, equipped with a Seabeam multibeam echo sounder augmented by an acoustic reflectivity measuring capabili~y built 'by R. Tyce. C. de Moustier. and F. V. Pavlicek. was returning from an exp.edition to the equatorial Pacific just prior to our Melville operation. It was thus arranged that de Moustier would use that combination to survey the area on Washington's transit home (Pascua, leg 5). This not only provided a comprehensive
2
S10 Reference 84-3
topographic chart (fig. 1) of the specific area which we would be working, it also resulted in a plot of the 12 kHz normal incidence reflectivity of the area (fig. 2). This was invaluable not only in confirming the OMA general assertion that we would find substantial variability of coverage, but going beyond that to show that we should expect the variability to occur over a distance of the order of 10 km. in the east-west direction.
III. Operations The expedition was carried out using R/V Melville with a crew of 23 (Appendix 1)
and a scientitlc party of 26 (Appendix 2). Principal reliance was placed on the ship's maneuverability and its main winch, equipped on alternate storage drums with the electromechanical cable for the Deep Tow and the 3 x 19 dredge wire for box coring. On deck the Deep Tow tlsh was handled by its Hyhoe crane mounted to work over the stern. while the box coring was done with the starboard A frame . The principal untried elements were the new main winch level wind system. completed only a few days before Sailing. and the acoustic backscatter system. The box corer, the basic Deep Tow system (Spiess and Lonsdale, 1982) and the acoustic transponder system (Spiess et al., 1966) had all been operated successfully on many other expeditions.
The scientitlc party consisted of 11 Deep Tow personnel, 6 box coring biologists, plus invited participants from NOAA, USGS, OMA. Korean Ocean Research and Development lnst., and Lockheed Ocean Mining, plus the normal Scripps resident and computer technicians .
Melville sailed from San Diego June 5 and arrived in the work are (14o-40'N, 1250-
25'W) on the afternoon of June 9. The first step was to match the locations of the Seabeam topography and the OMA transponder and launch our own array of 5 transponders (fig. 3). Deep Tow operations began June 10 with tows across the area in an east-west direction to test the backscatter equipment and to verify the prediction from the Seabeam reflectivity data that there should be' substantial changes of nodule cover along such tracks. After three such passes. a diagonal SE to NW run was made through the region of the dredge tracks and these were clearly delineated by the sidelooking sonars.
Once this reconnaissance phase was completed and camera runs carried out in key areas a period of several hours was spent adjusting and calibrating the backscatter system (this was the tlrst time that the entire system had been operated at sea). Following this, acoustic data were gathered along several tracks and the first lowering was terminated (morning of June 13) .
Wire was changed and box coring was begun in the control area, chosen to be in the southwest corner of the heavily nodule covered zone about 7 km from the principal dredge tracks and 2 km from the nearest such track. Six consecutive successful cores were taken (H 347 - H 352) averaging about 50 em penetration and showing 40 to 50 nodules in the 1/4 square meter area (Table 1).
While coring was proceeding the film from one of the cameras was developed, verifying the TV pictures and providing more detail. Transponder array coordinates were also adjusted based on data from the first lowering and reducing the rms range errors for individual vehicle pOSitions to 2.5 m.
Two further deep tow lowerings were then made to retine the coverage of the area for mining track identitlcation, nodule coverage and backscatter data. The first lowering of this pair was terminated early because of an electronic problem in the fish and the second because of apparent shifting of one of the main wi.nch traction unit wheels on its shaft. These lowerings clearly documented a strong transition zone from dense coverage with small ( ..... 5 cm) nodules, through a narrow region of larger ('" 15 cm) but fewer nodules and into essentially bare mud (fig. 4a, b, c, d).
Figure 1. Sea floor topography in the dredge test impact survey area. Data are from survey made with S10 Seabeam multi-beam sounding system and are in uncorrected meters.
Figure 2, 12 kHz relative reflectivity as measured with the Seabeam system.
14° 45i1t
/40
40'/V
fir 3.'~,'V
en (5 ::0 (1)
~ "1 (1)
g (1)
0) ~
t>
x x ,
;
\
, -"
I
ECHO 01 10 -21 JUNE 1983 FISH' NAVIGATION TRACK
635 m/in
• Q
Transponder s
Box Cores
:~&;;'~\'l~\m':\;'· Bockscoller Runs
eR 1-7 ___ Camero Runs
,," '" .. '
ci'
! '
Figure 3. Deep Tow track chart, including positions of box core bottom samples, camera tuns and acoustic backscattering runs, Coordinates are in meters east and north of lat 14 °34'N, long 1250S0'W.
6
12 JUN '83
lcro;" !
""" i
Table 1: BOX CORER S~IPLES TAKEN DURING R/V MELVILLE CRUISE ECHO I
SAMPLE Type Coordinates * Corrected Sub core Total Surface Buried Meiofauna Bottom Remarks NUMBER X Y Depth (m.) length Nodules Nodules Nodules Samples Photo
H347 Control 5416 7876 4511 52 em 45 41(10) 4(2) 3 No Disturbed by sampling
H348 Control 4222 7500 4504 42 em 37 37 0 0 No Good
H349 Control 5069 8091 4517 47 em 43 42 4 Yes Good
H350 Control 5712 7593 4506 42 em 43 43 0 5 No Good
H351 Control 6497 6691 4516 46 em 52 51 3 No Good
H352 Control 6606 7749 4502 45 em 38 32 6 3 No Slightly Disturbed
H353 Test 10295 14905 4516 45 em 117 116 1 (1) 4 No Disturbed in Situ
H354 Test 10380 14391 4514 46 em 93 92 No Good
H355 Test 10288 14690 4510 43 em 73 72 1 (1) 4 No Slightly Disturbed
H356 Test 10296 15580 4518 43 em 117 117 0 3 Yes Disturbed by sampling
H357 Test 10277 15002 4510 49 em 116 111 5(1) 2 Yes Good
H358 Test 10316 15099 4516 44 em 107 103 4 3 Yes Good
H359 Geology 12545 13130 4566 50 em 10 10 NA 0 Yes Good
H360 Control 4442 13599 4500 42 em 46 45(7) 1 (1) 4 Yes Very Good
H361 Control 14297 12528 4567 54 em 3 3 NA 0 Yes Very deep, oozy UJ ....... 0
H362 Control 7443 14886 4480 48 em 67 63(5) 4(4) Yes Disturbed ~ ro .....
* The origin of the coordinate system is at 14°34.00'N, 125°30.00'W. X,Y coordinates determined within MPL (I) ., Deep-Tow transponder Net parallel to lines of latitude and longitude, respectively. ro
g Numbers in parenthesis represent nodules stored at the U.S.G.S. facility in Menlo Park, CA. Remainder are at S.l.O. ro
~ ~ ,
-..J c.J
I ' ..
Figure 4, Deep Tow bottom photographs (a) Manganese nodule distribution typical of the central portion of the area. (b) Transition zone distribution typical of a northsouth band centered appro:.ldmately 12.5 km east of 1250 30'W and 100 to 500 m wide and Including box t.~ore H-3fi9 (F'ig. 3). (c) Region of very low nodule coverage typicaJ of the low reflectivtty region east of the transiUon zone. (d) An on-deck photo of a typical box core from the nodule coverage area.
With the dredge tracks well mapp(.~d (fig , 5) it was then appropriate to have a coring sequence in their vicinity. A.gain 6 cores were taken (H 353 - 358), all within 30m of dred.ge tracks, with one (H 353) having the appearance of being taken in the actual disturbed area of one of the tracks.
The fourth deep tow lowering was devoted primarily to acoustic backscatter data collection on a j\.j'W - Sl~ track crOSSing the nodule-to-mud transition zom) diagonally. Runs along this t.rack were made at 30 m otT bot.tom. 80 mot!, and a camera run at. 10 m.
8
At 10 p.m. on 20 June this run terminated when, for reasons not yet clear, the deep tow wire broke (at the ship) with about 6000 m of wire out. At this point we shifted to the dredge wire and took a box core while laying plans for recovering the Deep Tow fish (both for its intrinsic value and for the essential photographic data which its cameras held) . Recovery was effected bringing the flsh aboard undamaged 46 hours after its loss , using procedures described in section VII of this report.
Without a serviceable wire no further deep tow work could be carried out. Fortunately a substantial volume of good data had been obtained and thus the deep tow goals were achieved.
Box coring continued; however, due to lack of time before sailing from San Diego the clearance in the new level wind system was not adjusted adequately to handle the dredge wire. As a result it abraded a groove in the level wind to such a depth that it was judged that there was high probability of damaging the dredge wire. Operations were thus concluded at mid-day on 23 June, with a total of 16 consecutive successful box cores and 170 hours of deep tow operations. Melville arrived in San Diego 28 June, concluding Echo 1.
IV. Deep Tow Observations The Deep Tow observation tracks are shown in fig . 3. Precision echo sounder,
Side-looking sonar, 4 kHz sounder, vehicle depth (pressure and up-looking sounder), vehicle pitch angle, vehicle headings, water temperature and optical transmission data were collected throughout. Transponder ranges were also obtained for all of the tracks except for the extreme east and west portions of the area. Camera runs and acoustic backscatter runs are indicated in fig. 3. Camera runs were distributed with three goals - first, to sample the variability of bottom types throughout the area; second, to portray the nature of the dredge tracks; and third, to document sea floor conditions along tracks. Acoustic backscatter runs were chosen to cover areas with a variety of bottom types .
Mining dredge tracks were clearly shown by the SLS (side-looking sonar). The SLS imagery in most instances distinguished sharply defined furrows on each side of the track, indicating that the dredge rode primarily on a pair of skis or runners, separated by about 3 meters (fig. 6) . From the SLS data and transponder navigation it was possible to reconstruct the tracks in the area (fig. 5) and select box coring targets. Photos of the dredge tracks in most instances showed the immediately adjacent area (within 1 m) to be apparently undisturbed (fig. 7a). In some instances , however some additional sediment cover is evident in that zone (fig. 7b) . There may be some correlation of this difference with the fact that the dredge was not always being operated in a nodule-pumping mode , although this has yet to be established.
Acoustic backscatter data were collected in two modes - one operating at modest height off bottom (20-40 m) in order to emphasize low grazing angles and the other well off the bottom (70-90 m) to study the more intense normal incidence reflectivity. Substantial post-cruise analysis will be required to process all aspects of the digitally recorded data, however it was immediately clear that there were substantial variations (15 db) as one moved from heavy nodule cover into the non-nodule zone.
Figure 8 shows a sequence of returns for the 4.5 kHz channel for the run make with gains and geometry adjusted for normal incidence reflectivity observations along the track of camera run 4-1 (figs . 3 and 5). The wiggles at the left edge are from the tail of the transmit pulse . Note the fluctuations from ping to ping and particularly the drop in reflectivity in the middle of the sequence. At that point the vehicle crossed the dredge tracks shown in fig . 5.
10
SID Heference 84·-3
•• ,. _. wo o\.- ~_
[ ,'- . .... _"
• _ H ~_ ~ ............. '-~""'" ....:.~ .....
10Q ,m,;.,;. _~<:· . ~ . . - ..
~
100m
i,
,. -I H.'
Figure 6. E:xamplt.1 of dredge tracks as shown on the side-looking sonar. Small irnlgularitJes are caust.~d by yawing of the Deep Tow vl1hi.cle .
In order to show the gmwral trend of the data we have averaged the peak value for each frequency for flve minute intervals. this corresponds to about 200 m, which is approximately the footprint of the Seabeam echo sounder system used in the preliminary survey. Figure 9 shows the result for the enUre run. The db scales are arbitrary since source level and beam pattern information has not yet been int.rod.uced. The vertical bars associated with each average are the standard deviations of the observed values for each interval. Since the actual measurem~mt uncertainties at lhese signal-to-noIse rations are less than 1 db the spread represents the actual small-scale vdriations of effective reflectivity as one moves along tht1 trnck. This is not too surprising considering that the diameter of the first fresnel zone with the vehicle 75 m off bottom at. these frequenci.es varies from 10 m at 4-112 kHz down to 1.7 m at 160 kHz. In fact it may be possible after further analyses 'of both t.,b.e photographs and the acoustic data to use the statistics of the small-scale fiuetuations to help characterize the nodule distributions.
Figure 10 shows the change in reflectivity at each frequency based on the difference between the average values for the two extreme areas, de MousUer's value at 12 kHz falls quite reasonably at 15 db, Although the nodules are not in fact spheres (most are flatt.ened in the vertical dimension) it is reassuring to note that for an appropriate apprOximate mean nodule radjus of 2 em, ka is equal Lo 1 for a frequency of 12 kHz, not far from the peak of the curve,
1 1
1 2
Figure '1. Photogr'aphs of the edges of dredge tracks. (a.) C,,;a.mpie in which there is no appat'ent effect even with 10 em of the tn.\ck. (b) Example .in which smne sediment apparently was stirred t.o the extent that its settUng is noU'ceable one or !-,WO rrwteril frorn the track
Figure 9. Values of normal incidence relative r efle ctivit y a t six fr equencies aver aged over 200 m intervals along the track of camer a r un 4-1.
14
SIO Reference 84-3
NORMAL INC IDENCE 20/21 JU NE '83 22 :55 -02:30 GMT •
15 f--
co .-g
• u.: L.L. • 0
>-I- 10 f--> I-U W -l • • L.L. W • 0: :>-«
5 -
I I I I I 4.5 9 15 30 110 160
FREQ (kHz)
Figure 10. Change in reflectivity between nodule-covered and nodule-free zones as measured at six frequencies.
V. Biological Studies The primary purpose of the biological work on this cruise was to collect sufficient
material to evaluate the impact of the Deep-Sea Ventures test mining at DOMES site C. Our contractual goal, to collect at least 12 box corer samples, was met in spite of difficulties with the ship's equipment. In all we collected 16 sample s, 6 test, 9 control. and 1 geology (see Table 1) .
Sampling Design The sampling design was developed to test the specific null hypothesis, "there is no
faunal difference between samples taken immediately adjacent to mining tracks and samples taken several kilometers away from the mined area." This hypothesis is based on the assumption that any effects of the miner's sediment plume would be greatest adjacent to the tracks, and that the communities in the test area and the control areas were similar prior to mining. Failure to disprove the null hypothesis , or rather, failure to show that there were any effects of mining , could be caused by two possible conditions: 1. The test mining had no statistically noticeable effect on the community. 2. The assumptions on which the null hypothesis was based were not accurate in their description of the community and the presumed effects of nodule mining. Condition 2 must also be taken into account if a difference is found between the test and the control samples. Possible violation of the similarity assumption became a concern
15
during the cruise because the nodules in the test area were qualitatively smaller (but more numerous: see table 1) than those in the control area. We attempted to take additional samples with more similar nodule types, but equipment failures allowed only three extra samples. Because the control samples do vary in nodule cover, it may be possible to evaluate the effect of nodule size and density independent of the test samples.
Sample Collection Two initial sites were chosen with heavy reliance on information from the first
Deep Tow survey conducted soon atter arriving at the study area. The control area. in the southwest part of the transponder array, was chosen with
two factors in mind: 1. The site was fairly far from the area of mining (approx. ,7 km from the heaviest disturbance and approx. 2 km from the nearest dredge track) but still within the level nodule field; 2. Proximity to a path of the Deep Tow device was necessary to docUIIient the absence of nearby dredge tracks on side scan sonar, as well as providing ground truth data for the NSF backscattering research. Control sample positions were chosen in a stratified random design oriented within a half mile of the Deep Tow path (which ran east-west): 2 on the path, 2 north, and 2 south. Actual sample location varied somewhat from these locations due to ship's drift during the lowetings.
The test area was chosen on the basis of the side scan-sonar maps which showed the locations of dredge and miner tracks with good accuracy. The primary locality was in a highly disturbed portion at the northern part of the "J" shaped mined area where as many as 6 tracks ran closely parallel or crossed. This sampling pattern took .into account our uncertainty as to which of the dredge tracks were made in the nodule pumping mode: at least one of the dredge tracks must have been of this type and thus the samples should include sediment deposited by the mining plume. A mid-line was drawn with respect to the track lines, and random positions were picked along it. During the box corer lowerings, the Ship was navigated as close as possible to tracks in the near vicinity of the random points. Navigation generally put samples at or within 30 meters of a mapped location of a track.
Three additional control samples were taken to help evaluate the effects of nodule cover on the benthic infauna. These were placed at approximately the same latitude as the test site but at differing locations to the west (2 samples) and to the east (1 sample). The two western samples were on the same nodule field as the test and control samples, While the eastern sample was taken in a nearly nodule-free valley running north-south. A sixteenth sample was taken for geological studies only and was not processed for biology.
All box coring operations went extremely well and most of the samples collected were und.isturbed. The samples that were disturbed lost little material and can be considered to be quantitative. While previous boxcoring operations have been plagued with sample washing during retrieval through the water column. the box corer used on this cruise had modified seals that nearly eliminated any water circulation after closure. The top water drained off the samples was clear and had temperatures ranging from 9 to 12 degrees C., indicating there was little intermixing with the 25+ degree C. surface water. Previous lowerings with this model box corer had top water temperatures close to that of the surface water. We believe that these samples are the best that have ever been collected from this region for biological purposes.
A small camera made by Ocean Instruments, Inc . was attached to the box corer for documenting the immed.iate environment of the box corer samples prior to the device entering the bottom. The camera was successful in obtaining photographs of 8 sample sites; the remaining samples do not have similar documentation due to camera malfunctions or breakage. The box corer camera photographs will be very useful for , independent estimates of nodule cover at the sample locations.
16
SID Reference 64-S
Sample Processing
The box corer samples were subdivl(ie . .l Li such a way as to allow maximum utilization for benthic macrofaunal analysis, but permitting other analyses to be made. Other types of subsamples included meiofauna subcores, geology subcores, and collections of manganese nodules for studies of encrusting fauna, mineralogy, and acoustic backscatter. In addition, the surface of each sample was photographed using a 35 mm camera with a macro lens . For consistent documentation, the camera was attached to a frame in a fixed pOSition above the sample. Table 2 summarizes some information from each sample.
Macrofauna The macrofaunal material was collected from the top water over the core and the
top 10 em of the sediment. This material was subdivided into three main layers: a top 1 em layer, a 1 to 5 em layer, and a 5 to 10 em layer. This subdivision had two main purposes: 1. It allowed for rapid fixation of the top layer, which should contain most of the fauna; 2. Separating the layers of the sample may enhance the efficiency of the laboratory sorting process. For example, if we determine that less than 5% of the total fauna occurs in the 5 to 10 cm layers, we could omit the bottom layer from immediate sorting. We also could apply different sorting techniques to the three different layers.
The macrofaunal part of the samples were sieved through O.S rom screens on board the ship. The entire top 1 em layer and the screen residues of the lower layers were placed in 4% buffered formaldehyde-seawater for fixation. Mter several days of this treatment, plus an occasional gentle agitation to aid fixation, the screen residues were washed with fresh water and placed in 60% ethanol for long term preservation. These procedures were ' successfully completed on all the macrofaunal samples. At the writing of this report, sorting of the samples HS47 in our laboratory at Scripps is already under way, and is proceeding well.
Meiofauna A frame with four 2.5 cm diameter acrylic tubes was added to each sample box for
in situ sampling of meiofauna. While the tubes generally had good samples, a number of them were broken or had their sample disturbed by contact with nodules. In all, 40 intact meiofauna subsamples were collected.
Each meiofauna subsample was divided into three layers, similar to layering Bcheme for the macrofauna: top water and the top 1 em, 1 to 5 cm, and 5 to 10 cm. This will aid comparability between the two types of analYSis . Each layer was fixed and preserved whole in buffered formaldehyde-seawater.
Manganese Nodules, Encrusting Fauna The nodules from each sample were mapped into 10 em quadrants, and carefully
removed for further treatment. For encrusting faunal studies, a random subs ample of 15 nodules located in the inner 900 square cm was preserved and labeled. Other nodules with particularly well-preserved organisms were also collected. The remaining nodules were rinsed of sediment in a O.S mm sieve, and stored at 4 degrees C. for nonbiological purposes. Material washed off the nodules was preserved for inclusion into the macrofauna! analysis. The encrusting fauna work used several methods of preservation and storage . Plastic containers with upright supports in the boltom were used to store most of the larger and more interesting specimens. The smaller nodules were put in plastic bags and then into large nalgene containers. Most nodules were fixed in buffered formaldehyde-seawater, but apprOximately 10 specimens were carefully preserved in 2% gluteraldehyde-seawater. Some specimens were transferred to 85% ethanol to protect them from formaldehyde acidification and to make them easier to handle.
17
Subsurface nodules were divided into two groups: those that appeared to be buried in situ. and those pushed down by the box core edges and meiofauna cores. It was easy to distinguish between the two types of buried nodules. The nodules originally buried had their size and depth recorded. while those that were pushed down were photographed for use in cover estimates.
VI. Geology
Introduction The substrate samples colleeted by the biology team together with physical data ~
collected by the deep tow team have provided the information for a preliminary description of the geology of the Echo I study area.
From 16 boxcores recovered by the biology team, sediment samples and a small number of manganese nodules were collected. The sediment samples consist of 2 inch diameter sub cores (averaging 46 cm in length) from each boxcore, and surface seditnent samples of the top 1 cm layer of each boxcore held by a 63 micron sieve (after sieving by the biologists). The subcores were taken within 15 minutes after each boxcore came on board. Subcorlng immediately followed the removal of all surface nodules. To facilitate easy penetration of the 2 inch diameter plastic core tube and prevent loss of sediment. the end which pierced the sediment was sharpened and a vacuum system was employed to "pull" the core tube through the sediment. Opposite the sharpened end of the tube a stopper with two holes in it was firmly inserted with one hole connected to a vacuum pump. and the other allowing finger control of the evacuation rate as the core tube penetrated the sediment. The subcore often remained in the boxcore for 20 minutes or more, as the biology team removed the top layers of sediment and searched for buried nodules. The sediment surrounding the inserted subcore tube should have acted to keep the sediment sample from warming up appreciably during that time. When each subcore was removed from the boxcore it was tightly capped and placed in cold storage aboard the ship. These cores are now stored under refrigeration at the U.S. Geological Survey facility in Menlo Park. California. About 25% of the nodules recovered were retained by the biology group, a small number (see Table 1) were allocated to USGS and the remainder are stored in the SIO core locker for primary use by the Deep Tow group. About 50 nodules have been maintained in their original seawater particularly for use in making subsequent acoustic measurements. Buried nodules have been retained in moist condition in association with the surrounding sediment. Table 1 includes the lengths of each subcore and the total number of surface and buried nodules recovered in each boxcore.
Observations The subcores have been split lengthwise to allow sampling and sediment color and
structure observations . Except for subcore H361, the subcores all have an upper unit of dark yellowish brown (10 YR 4/2) sediment averaging 8 cm in thickness; mottling is very rare in the upper unit. Below the upper unit. in abrupt but often mottled contact. is a unit characterized by intense mottling. The mottling is of colors varying from that ot the upper unit, to moderate yellowish brown (10 YR 5/4). to a grayish orange (10 YR 7/4). The intensely mottled unit is often short (5 cm) and ends abruptly, but in some cases it continues down the core 20 cm, and tends to lose intensity with depth. Below the intensely mottled unit is generally a brown unit lighter than the upper unit, though darker brown layers and blackish discolorations are not uncommon. Subcore H361 has an upper unit similar to the rest of the subcores and an intensely mottled unit below the upper unit. The unique attribute of subcore H361 is the color of its lower half. It is grayish orange (10 YR 7/4) with mottles of brownish sediment. Subcore H361 was the
18
SIO Reference 84-3
only boxcore without any nodules greater than 2-3 cm in diameter, although it did have 3 of this size range.
Smear slides of sediment from different depths within cores H347, H348 and H349 show clay as the dominant fraction. Biogenic silica is common (5-25%) in the top 5 cm of sediment but decreases in abundance with depth. The sediment should thus be classified as a biogenic silica bearing pelagic clay, similar to other sediments collected from this area of the Pacific. No calcareous debris was observed in the smear slides .
The nodules from the study area are generally discoidal in shape though pancake, spheroidal, and irregularly shaped nodules also occur. The upper surface of the nodules tends to be smoother than the bottoms which are coarse or gritty in texture. In some cases the nodule bottoms are deeply convoluted as well as being gritty. Except for boxcores H359 and H361, nodule surface coverage averages 40-60%. Boxcore H359 contained 9 large nodules, some over 16 cm in their longest dimension. Boxcore H361 contained only 3 small (2-3 cm) nodules .
Boxcore stations H347-H352 are relatively closely spaced in one region of the study area. Boxcore stations H353-H358 are also closely spaced and are located some distance from stations H347-H352. These two sets of boxcore stations have distinct nodule populations. Boxcores H347-H352 contain large nodules (averaging about 6-8 cm in diameter) and have total populations averaging 38 individuals. In contrast, boxcores H353-H358 contain smaller nodules (averaging about 4-6 cm in diameter) and have larger populations averaging 97 individuals per boxcore.
further Studies
The Echo I study area lies within the Deep Ocean Mining Environmental Study 's (DOMES) Site C. Extensive studies of the lithic and acoustic stratigraphy (Piper et aI., 1979a) and geochemistry of the sediment and nodules (Bischoff et al., 1979 and Piper et al, 1979b) at Site C should prove valuable for comparison and insight into the geology ot the Echo I study area. A limited number of analyses should show whether the Echo I sediments and nodules are similar to those already studied at Site C. S.E. Calvert has shown interest in examining the sediment cores and manganese nodules.
The bottom photographs, side looking sonar data, Seabeam survey and high resolution acoustic data acquired by the Deep Tow team, together with the sediment and nodules should provide an adequate base from which a general geological description can be synthesized that will complement and enhance the major studies included in Echo I expedition.
VII. Fish Recovery As noted in section III, early on the morning of 21 June, the deep tow wire parted,
approximately at the outboard end of the crane, with 6,000 m of wire out in 4500 m of water. There were no precursors or indications of what caused the problem. Towing was proceeding in a stable mode over level sea fioor with the vehicle about BO m off bottom and the sea and swell were slight . Post analysis of the broken end indicated that a number of inner lay strands all within a couple of cm of one another may have been broken (or very nearly so) for some time .
Both ship and fish were being tracked in the transponder net and, as designed. the emergency transponder built into the vehicle activated itself in response to the loss of electrical power from the cable. The geometry of the situation was thus known, although not the actual disposition of the 6,000 m of wire.
Following a similar occurrence in 1967 we had devised a special drag device and successfully, on a subsequent expedition, recovered our vehicle (Spiess, 1974). Since
19
that time the drag has been taken on any expedition on which there was a dredge wire adequate to use it. Basically the device consists of a pair of plates, spring loaded to press them together in such manner that the wire will jam between them. This assures first that the wire will not slide past the drag when the load is concentrated at one end of the wire. Second, the plates are formed in such a way that the wire is held through an arc of about 1m diameter rather than being bent sharply as would be the case with a more conventional grappling hook.
The drag was secured to the trawl wire on the main winch and lowered, using the side A-frame. A relay transponder (Boege man et al., 1972) was fixed to the wire 300 m above the drag, and the unit was lowered to the sea ftoor in the viCinity of the fish. Wire was paid out and the ship maneuvered as in a conventional side A-frame dredgirtg operation, keeping the relay transponder about 100 m off bottom to assure that ttie drag would ride along the sea floor at the proper angle. Navigation was marginal at the start of the first run and the wire was not engaged. On the second pass the relay crossed the line along which the broken wire was originally tending at a distance of about 200 m from the fish. the ship was maneuvered back toward the fish position as the trawl wire was reeled in. Once the relay transponder was well off the bottom it was clear from the tension reading that the broken wire had been engaged and was being lifted off the sea floor.
In spite of the drag passing close to the fish, the wire had been snagged 4500 meters from the end to which the fish was attached. This produced some anxiety since the fish did not start up from the bottom until the drag was nearly at the waterline. It also presented the problem of having to recover 4500 m of the damaged cable in order to retrieve the fish.
Once the drag was up out of the water wrap-around preformed wire grips were used to stop off each of the two sides of the damaged wire independently. The drag was cut loose, brought on deck and detached from the trawl wire, which was then fastened to the grip on the strand presumed to be the side attached to the fish. The presumption was verified by the tension reading, equal to the in-water weight of 4500 m of wire plus the vehicle. Given the height of the A frame, the dimensions of the grips and the arrangements for stopping them ott it was possible to raise the grip 2 to 3 meters with the winch, wrap on a second grip secured near deck level, detach the trawl wire, attach it to the lower grip, remove the upper grip and lift the broken wire another 2 to 3 meters. This process was repeated until about 100 m of wire had been brought on deck. At that point the trawl wire was removed from the traction unit, the broken wire was threaded through it to the deep tow wire storage drum, secured to the broken end on the drum and the remaining 4400 m of wire was wound in.
Fortunately there were no bad kinks in the damaged wire and the fish was landed safely on deck just 46 hours after the accident occurred. The fish was completely undamaged by its 80 m fall to the bottom and any dragging associated with the recovery operation. The other section of wire was dumped in the non-nodule covered area so as not to be an impediment to future sea floor operations.
20
SID Reference 84-3
References
Bischoff J. 1., G.R. Heath, and M. Leinen (1979) Geochemistry of Deep- Sea Sediments from the Pacific Manganese Nodule Province: DOMES Sites A, B, and C. In: Marine geology and oceanography of the Pacific manganese nodule province, J .L. Bischoff and D.Z. Piper, editors, Plenum, New York, pp. 397-436.
Bischoff, J. L., and D. Z. Piper, eds. (1979) Marine Geology and Oceanography of the Pacific Manganese Nodule Province, Plenum Press, New York.
Boegeman, D. E., G. J . Miller and W. R. Normark (1969) Precise positioning for near-bottom equipment using a relay transponder. Mar. Geophys. Res., v. 1, p 381-396.
Piper D.Z., H.E. Cook and J.Y. Gardner (1979a) Lithic and acoustic stratigraphy of the equatorial North Pacific: DOMES Sites A, B, and C. In: Marine geology and oceanography of the Pacific manganese nodule province, J.L. Bischoff and D.Z. Piper, editors, Plenum New York, pp. 309-348.
Piper D.Z., K. Leong and W.F. Cannon (1979b) Manganese nodule and surface sediment chemistry: DOMES Sites A, B, and C. In: Marine geology and oceanography of the Pacific manganese nodule province, J.L. Bischoff and D.Z. Piper, editors, Plenum, New York, pp. 437-473.
Spiess, F. N., M. S. Loughridge, M. S. McGehee and D. E. Boegeman (1966) An acoustic transponder system. Navigation. J . Inst. Navigation, v. 13, no. 2, p. 293.
Spiess, F. N. (1974) Recovery of equipment from the ocean fioor. Ocean Engineering. v. 2, p . 243-249.
Spiess, F. N., and P. F. Lonsdale (1982) Deep tow rise crest exploration techniques. Marine Tech. Soc. Jour., v. 16, P 67-75.
21
APPENDICES
Appendix 1 - Ship's Force
R. Haines, Captain R. Fish, Chief Engr. A. Pelz, Mate D. McGuire, Mate J. Cox, Mate J. Addington, Engr. J. Achenback, Engr. P. Bueren, Eng. W. Collins, Deck Eng. M. Hotchkiss, Deck Engr. R. King, Elect. P. Polk, Radioman
Appendix 2 - Scientific Party
F. Spiess, Co-Chief Sci., MPL R. Hessler, Co-Chief Sci., MBRD J. Boaz, Tech. , DCPG D. Boegeman, Eng., MPL T. Clary, Tech. , MPL G. Corolla, Tech., MPL M. Crawford, Sci., Lockheed C. de Moustier, Grad. St., MPL R. Dick, Sci., OMA R. Elder, Engr., MPL E. Foell, ScL, OMA S. Han, SeL, KORDI J. Jain, Engr., MPL
Abbreviations
G. Brooks, Elect. Tech. C. Jones, Cook A. Velasco, Cook P.Andreco, Seaman A. Santos, Seaman S.Hughes, Seaman D. Smith, Seaman W. Bradley, Oiler D. Herman, Oiler T. Adiboye, Oiler J. Cozad, Bos'n
R.Lawhead, Tech,MPL C. Lowenstein, ScL, MPL R. Moe, Tech, DCPG L. Mullineaux, Grad St., MBRD P.Rude, ScL, USGS J. Snider, ScL, NOAA W. Stockton, SeL, MBRD A. Theberge, Sci., NOAA E. Varnum, Tech., MBRD M. Weydert, Grad. St. , MPL J. Wilkinson, Tech., MPL G. Wilson, Sci., MBRD R. Wino, Tech., MBRD
DCPG - S1O, Data Collection and Processing Group KORDl - Korean Ocean Research and Development Inst. MBRD - S1O, Marine Biological Research Division MPL - S1O, Marine Physical Laboratory NOAA - National Oceanic and Atmospheric Administration OMA - Ocean Mining Associates S10 - Scripps Institution of Oceanography USGS - United States Geological Survey
