For clarification, the events at the dredged harbor station were 

 separated from those at the station receiving dredged material. Since 

 disposal did not destroy the whole assemblage, it was referred to as 

 dredged material disturbance with subsequent recovery. Dredging at the 

 harbor station removed all the fauna; however, the area was recolonized. 



Maintenance dredging of the Moss Landing Harbor was done during 

 August 1971. A bucket dredge was used to load dredged material aboard 

 barges that were towed to the disposal area at the Monterey Canyon head 

 (Fig. 1). About 91,400 cubic meters of material were disposed of in 

 water depths of 10 to 60 meters. Coarse sand from between harbor jetties 

 was dredged first; finer sediments were dredged later as dredging pro- 

 gressed into the inner harbor. From November 1971 to April 1972, "clean- 

 up" dredging operations were performed by the Moss Landing Harbor District, 

 using a small pipeline dredge. Material was periodically piped to the 

 end of the Moss Landing Pier and dumped in 10 meters of water. Cleanup 

 involved less than 9,100 cubic meters of material. 



Permanent biological stations were established in the canyon head, on 

 an adjacent flat bottom, and in the harbor (Fig. 1). Sampling began 

 before dredging in June 1971 and continued after dredging from September 

 1971 to April 1973. 



II. SEDIMENT MOVEMENT AT THE MONTEREY CANYON HEAD 



Monterey Canyon is the largest submarine canyon on the west coast of 

 the United States. Sediment movement at the canyon head, which involves 

 the dynamics of sediment transport to greater depths, was reported by 

 Shepard (1948) , Charlock (1970) , and Arnal (1971) . This study was ini- 

 tiated in 1971 in response to the need for recommendations on optimal 

 disposal techniques and periods required for a better understanding of 

 sediment movement in the canyon. 



The canyon head is fed by three main branches: (a) The jetty branch, 

 (b) the main branch, and (c) the southern branch which has several 

 smaller tributaries. The axis of the southern branch is flanked on the 

 east by a large submarine ridge with a fairly flat top, located in approx- 

 imately 15.2 meters of water (Fig. 2). North of this ridge is the main 

 branch of the canyon head (Shepard, 1948). The main branch is bounded on 

 the south by a smaller submarine ridge that begins in 18.3 meters of water 

 and slopes steeply to about 30.5 meters. The primary disposal station for 

 biological studies (P-3) is located at a depth of 18.3 meters on the shore- 

 ward edge of this ridge (Figs. 2, 3, and 4). A smaller southern tributary 

 runs parallel to the main axis to the south, then joins it in about 30.5 

 meters of water (Figs. 2 and 3). The main branch leads directly to the 

 head of the Moss Landing Pier. A number of shallow channels or tributarie: 

 with heads at the shoreward end of the north ridge (Fig. 2) , traverse the 

 north canyon wall of the main axis. The bottom slopes gently to 4.6 or 

 6.1 meters near the end of the Moss Landing Pier, then dips abruptly to 

 12.2 meters. A shallow-water terrace up to 6.1 meters high borders most 

 of the southern branch at these depths (Fig. 2) . Its slope ranges from 



