BENTHIC INFAUNA OF LYDONIA CANYON AND THE ADJACENT SLOPE ENVIRONMENT 



Nancy J. Maciolek 

 Senior Research Scientist 

 Battel le Ocean Sciences 

 Duxbury, MA 02332 



J. Frederick Grassle 

 Senior Scientist 



Woods Hole Oceanographic 

 Institution 



Woods Hole. MA 02543 



Among several stations sampled as part of programs funded by the 

 Minerals Management Service, stations were positioned at approximately 

 150, 550, and 2100 m in Lydonia Canyon and on the adjacent slope. 



At 150 m, two stations were sampled inside the canyon and one on the 

 adjacent slope. Of the two canyon stations, one had silty sediments 

 and was dominated by the amphipod Ampelisca aqassizi . The other 

 canyon station had coarser sediments and a much different suite of 

 dominant species. The slope station was also dominated by A. 

 aqassizi , but a much higher percentage of the fauna at the slope 

 station (35%) than at the canyon station (12%) was accounted for by 

 this species. Of the next 19 dominant species, however, only two 

 occurred in common, indicating a major difference in faunal 

 composition between the slope and canyon station, even though both 

 were dominated by A. aqassizi . Diversity was lower at both canyon 

 stations than at the slope station. Similarity analysis showed that 

 none of the three stations had a high level of similarity to any of 

 the other three, but each was most similar to other stations sampled 

 in the program. Subtle differences in sediment texture appear to 

 affect benthic community composition. 



At 550 m, the top dominant at both stations was the polychaete Thayrx 

 annulosus , but this species accounted for 32% of the fauna at the 

 canyon station and only 6% of the fauna at the slope station. Of the 

 next 19 dominant species at the canyon station, five were also among 

 the top dominants at the corresponding slope station, but generally 

 ranked lower and did not dominate the slope community to the same 

 extent. Diversity was lower at the canyon station. The slope- 

 station fauna was more similar to the fauna at another slope station 

 more than 200 km distant (but also at 550 m) than it was to the 

 adjacent canyon station. Because sediment texture was similar at the 

 canyon and adjacent slope station, it is suggested that the current 

 regime at this depth controls the benthic community. 



B-14 



