Date of Award
2004
Degree Type
Dissertation
First Advisor
Emily Carrington
Abstract
Corals and macroalgae often co-occur on temperate reefs, where macroalgae provide a majority of the bio-complexity and small scleractinian corals occur in low abundance. Macroalgae typically outcompete adjacent organisms for resources such as space, light, and nutrients, and one mechanism for this competitive success is abrasion. This study explores factors that may influence the interactions between corals and macroalgae, in particular macroalgal abrasion, on a temperate reef in Narragansett Bay, Rhode Island. Chapter One examines how exposure, depth and orientation influence the abundance and morphology of the coral Astrangia poculata, as well as the percent cover of macroalgae and other invertebrates. Coral colony density increased, and algal percent cover decreased, with depth and from horizontal to vertical substrates. The morphology of corals at shallow depths and on horizontal substrates, where macroalgae dominated, were more commonly short, rather than tall. Both short and tall corals were common to vertical substrates at depth, where algae were less abundant. These results led to the hypothesis that short colonies have a survivorship advantage over tall colonies on algal dominated substrates. Chapter Two examines how coral morphology may influence the outcome of abrasion by macroalgae. Transplant experiments were conducted with short and tall morphologies of Astrangia poculata in cleared areas, Laminaria saccharina (kelp) areas and Chondrus crispus areas. Short colonies survived better and experienced less macroalgal contact than tall colonies in algal dominated habitats. In addition, intermittent algal abrasion was noted in kelp areas, while chronic, constant abrasion was observed in C. crispus areas. Survival of coral transplants in algal areas was prolonged in summer compared to fall, suggesting the severity of abrasion may be influenced by water flow. In Chapter Three, laboratory flume experiments were conducted to examine the influence of algal morphology and flow on contact rate of Astrangia poculata. Of the four morphologies of Chondrus crispus examined, the heavier and highly branched morphotype that is common subtidally contacted corals most frequently. Of the three coral heights examined, the shortest corals were less frequently contacted by all algal morphotypes, and these differences were magnified with increasing flow speed.
Recommended Citation
Grace, Sean Patrick, "Ecomorphology of the temperate scleractinian Astrangia poculata: Coral-macroalgal interactions in Narragansett Bay" (2004). Open Access Dissertations. Paper 1976.
https://digitalcommons.uri.edu/oa_diss/1976
Terms of Use
All rights reserved under copyright.
