BENTHIC AMPHIPODA OF SUBMARINE CWi-ONS 

 AND BASINS OF C\LIFORNLA 



by J- Laurens B.\rx.\rd 



INTRODUCTION 



The shelf of southern California and its offshore islands is indsed by 

 numerous submarine canyons, many of which debouch onto trough and 

 basin floors of the borderland area (Emery, 1960: Emery and Hulse- 

 mann, 1963). They are of particular interest to biologists, because they 

 bring bathyal depths (200 - 1000 m) close to shore where food supplies 

 might be higher than in comparable depths on the continental slopes. 

 Their gradients and possibly their sediments are probably similar to 

 those of regular continental slopes, although sediments of the slopes in 

 southern California have not been well explored (Emery, 1960). 



Where canyon heads come close to shore, sand moved by longshore 

 currents is entrapped and flows down canyon axes. Sediments accumu- 

 lating on the shoreward canyon floors occasionally are set in motion as 

 turbidity flows, possibly either as the result of seism^ic activity or because 

 of increments in overburden. These sedimentary masses, mixed with 

 water, flow down the canyon axes and in certain can}-ons flow onto the 

 fans of submarine basin slopes (Emery and Hulsemann. 1963). An in- 

 herent catastrophic unstability to the substratum of the biota proves 

 worthy of examination. 



Particularly interesting is the opportxmity to report upon bathyal 

 gammaridean amphipods collected in quantitative samples. Because the 

 canyon bathyal fauna merges with that of the subsill and somewhat m:i- 

 poverished borderland basins, amphipod assesanents already published by 

 Hartman and Barnard (193S. 1960) have been perfected and included 

 herein, along with data from the continental slopes that ha\-e accumu- 

 lated from examination of samples reported upon by Hartman (1955). 



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