SESSION SUMMARY: BENTHIC ECOLOGY - HARD SUBSTRATA 



Robert S. Steneck 



Ira C. Darling Marine Laboratory 



Walpole, ME 04575 



Rock outcrops along the shores and scattered throughout the 

 Gulf of Maine contribute to its high habitat diversity and 

 productivity. Because productivity, abundance and diversity of 

 rock-dwelling organisms is greater (per unit area) than it is for 

 other habitats, research on their ecology will allow more 

 realistic estimates to be made of total productivity, carrying 

 capacity, and food webs of the Gulf of Maine. 



Research on hard substratum habitats targeted an offshore 

 site at Ammen Rock Pinnacle (part of the Cashes Ledge complex) 

 which is centrally located in the Gulf. Communities there are 

 unique in species composition, abundance of organisms (including 

 commercially important finfishes) and the nature of their food 

 webs. Specifically, they provide us with a rare opportunity to 

 study benthic primary productivity in a region isolated from 

 coastal habitats which are affected by intense herbivory and 

 variable nutrient inputs from terrestrial runoff and tidal 

 mixing. They also allow us to conduct research on a benthic 

 community dominated by fish rather than the invertebrate 

 predators that characterize coastal habitats throughout the Gulf 

 of Maine. NURP support of manned submersibles and scuba diving 

 operations have allowed protracted and wide-ranging manipulative 

 studies to be conducted on these deep water rock assemblages. 

 Such studies, together with extensive research in shallower 

 coastal habitats allow comparisons to be made of the patterns, 

 processes and mechanisms structuring nearshore vs offshore 

 communities. 



The research at Ammen Rock Pinnacle and other offshore sites 

 is very much "in progress". The strategy has been to quantify 

 patterns in the distribution and abundance of benthic organisms 

 and their predators and then to focus on the processes such as 

 recruitment, productivity, growth, competition and predation 

 important to the observed patterns. The paper of Vadas and 

 Steneck reports on the zonation pattern of deep water algal 

 populations on Ammen Rock Pinnacle where three distinct zones of 

 dominance appear at various depths, each with distinct 

 morphologies. Witman and Sebens studied patterns of benthic 

 invertebrates, predators and aspects of the local physical 

 oceanography. These two teams have been collaborating in NURP- 

 UCAP sponsored submersible projects in this area over past four 

 years. This collaboration has grown this year to include joint 

 projects on kelp competition and fish predation. 



