HR: 1330h
AN: OS42A-0828 [PDF]
TI: Environmental Impact of a Submarine Cable: Case Study of the Acoustic Thermometry of Ocean Climate
(ATOC)/ Pioneer Seamount Cable
AU: * Kogan, I
EM: kogan@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 United States
AU: * Kogan, I
EM: kogan@mbari.org
AF: Monterey Bay National Marine Sanctuary, 299 Foam St, Monterey, CA 93940 United States
AU: Paull, C K
EM: paull@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 United States
AU: Kuhnz, L
EM: linda@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 United States
AU: von Thun, S
EM: svonthun@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 United States
AU: Burton, E
EM: erica.burton@noaa.gov
AF: Monterey Bay National Marine Sanctuary, 299 Foam St, Monterey, CA 93940 United States
AU: Greene, H G
EM: greene@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 United States
AU: Barry, J P
EM: barry@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 United States
AB:
To better understand the potential impacts of the presence of cables on the seabed, a topic of interest for which little data
is published or publicly available, a study of the environmental impacts of the ATOC/Pioneer Seamount cable was conducted.
The 95 km long, submarine, coaxial cable extends between Pioneer Seamount and the Pillar Point Air Force Station in Half Moon
Bay, California. Approximately two thirds of the cable lies within the Monterey Bay National Marine Sanctuary. The cable is
permitted to NOAA- Oceanic and Atmospheric Research for transmitting data from a hydrophone array on Pioneer Seamount to
shore. The cable was installed unburied on the seafloor in 1995. The cable path crosses the continental shelf, descends to a
maximum depth of 1,933 m, and climbs back upslope to 998 m depth near the crest of Pioneer Seamount. A total of 42 hours of
video and 152 push cores were collected in 10 stations along cable and control transects using the {\it ROVs Ventana} and
{\it Tiburon} equipped with cable-tracking tools. The condition of the cable, its effect on the seafloor, and distribution of
benthic megafauna and infauna were determined.
Video data indicated the nature of interaction between the cable and the seafloor. Rocky nearshore areas, where wave energies
are greatest, showed the clearest evidence of impact. Here, evidence of abrasion included frayed and unraveling portions of
the cable's armor and vertical grooves in the rock apparently cut by the cable. The greatest incision and armor damage
occurred on ledges between spans in irregular rock outcrop areas. Unlike the nearshore rocky region, neither the rocks nor
the cable appeared damaged along outcrops on Pioneer Seamount. Multiple loops of slack cable added during a 1997 cable repair
operation were found lying flat on the seafloor. Several sharp kinks in the cable were seen at 240 m water depths in an area
subjected to intense trawling activity. Most of the cable has become buried with time in sediment substrates on the
continental shelf whereas much of the cable remains exposed in sediments at deeper depths. The cable is exposed in rocky
environments of the nearshore region and on all of Pioneer Seamount.
The main biological features associated with the cable were organisms utilizing the cable as substrate and occasionally as
shelter. Considerable care was taken to count megafauna in video transects and macrofauna from the top 5 cm of push cores.
Few differences were found between cable and control sites at the 95% confidence level. Anemones {\it Metridium farcimen}
and {\it Stomphia sp.} colonized the cable and were more abundant in cable transects at most soft sediment sites. Coarse
extrapolation of the transect data suggest that more than 5,000 {\it M. farcimen} may live on the continental shelf portion
of the cable. Several other species of anemones living on the cable are common along deeper sections of the cable route.
Where the cable was buried, the presence of linear rows of sea anemones proved to be a reliable indicator of the cable's
position. Flatfish and rockfish apparently congregate near the cable and were as much as 1 order of magnitude more abundant
near the cable at some sites.
DE: 3045 Seafloor morphology and bottom photography
DE: 3094 Instruments and techniques
DE: 4294 Instruments and techniques
DE: 4804 Benthic processes/benthos
DE: 4815 Ecosystems, structure and dynamics
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting