Volume 48 (1996) Number 2 
149 
First data came from long-term mooring D1 de 
ployed in DBA for about 28 months (861 days), from 
September 1989 to January 1992 (FW ‘SONNE’ 
cruises 64 and 77). Samples were taken by Aan- 
deraa ROMS current meters at 15, 30, 50, and 200 
metres above bottom (mab). The sampling rate was 
180 minutes at 200, 50, and 15 mab, and 60 mi 
nutes at 30 mab. Data recording at 30 mab stopped 
after 400 days due to limited capacity of the ma 
gnetic tape (see Table 1). The results of this de 
ployment are discussed in detail by Klein [1993]. 
Four years later, two short-term moorings were 
deployed from January 1996 until March 1996 du 
ring RA/ ‘Sonne’ cruise 106 within the framework of 
ATESEPP 4 '; the MK1 mooring in the SEDIPERU 
area, and the MK2 mooring in DEA (see Fig. 1). 
These deployments were maintained for only about 
52 days, but the sampling intervals were much 
shorter and the bottom instruments were closer to 
the seabed. The identically designed moorings 
were equipped with Aanderaa RCM8 current me 
ters at 0.6, 4, 13, 50, 202, and 503 mab (Klein 
[1996]). The sampling rate was 5 minutes at 0.6, 4, 
Fig.1: Location of the DISCOL Experimental Area 
(DEA) with moorings D1 and MK2 and of the SE 
DIPERU site with mooring MK1. Light spotted 
areas are shallower than 3500 metres. The ar- 
rows schematically outline the circulation of 
bottom water according to Lonsdale [1976]. 
and 13 mab, and 10 minutes for the upper instru 
ments. At MK2, no data were obtained from 0.6 mab 
due to failure of the data storing unit. Unfortunately, 
both moorings did not provide information on the 
current direction at 0.6 and 4 mab. The cause of the 
failure was not found. 
Topography and bottom roughness 
The DEA proper is a cirular site centered at 
7° 4.4’ S, 88° 27.6’ W with a diameter of 2 nautical 
miles (nm) and an area of 10.8 km 2 (spotted circle in 
Fig. 2), located at the northeastern margin of the 
Peru Basin nodule field. The depth varies between 
4140 and 4170 m. D1 lies in the western part of 
DEA, MK2 about 5 nm west of the DEA centre. 2 nm 
north of DEA lies a hill of 300 m height and a max 
imum slope of 10°. Depths around the disturbed 
area vary between 3890 and 4220 m. 
Investigations at the SEDIPERU site focus on 
the area around a 250 m high conical volcanic hill at 
6° 32’ S, 90° 28’ W which is surrounded by a relati 
vely flat area with a fairly thick sediment cover (see 
Fig. 2). Depths vary between 3900 and 4300 m. 
MK1 lies 2 nm east of the foot of the hill. 
The Peru Basin is characterized by the occur 
rence of extremely large nodules with maximum 
diameters of up to 21 cm, while nodules smaller 
than 1.5 cm are scarce (von Stackelberg [1997]). 
The largest number of nodules per m 2 is found on 
top of the seamounts. At both sites, areas with 
dense nodule coverage are adjacent to erosional 
areas which are basically free of manganese 
nodules. Photo-sledge profiles show a very rapid 
transition between these areas (Wiedecke and 
Weber [1996]). The diameter of the nodules gene 
rally varies between 2 and 13 cm, the majority mea 
suring 3 to 5 cm (see Fig. 3). The number of nodules 
found on the surface of box corer samples during 
Sonne cruise 106 ranges between 1 and 143 
nodules at the DEA, and between 1 and 86 nodules 
at the SEDIPERU site (Schriever et al. [1996]). 
41 ATESEPP = Auswirkungen technischer Eingriffe in das Ökosystem der Tiefsee im Süd-Ost-Pazifik vor Peru = Impacts of potential technical inter 
ventions on the deep-sea ecosystem of the southeast Pacific off Peru