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Thesis - NSU Access Only
Edward O. Keith
Robert S. Pomeroy
James D. Thomas
Sessile marine invertebrates often exhibit non-random distributions both horizontally and vertically. The larvae of scleractinian corals settle and metamorphose in response to numerous environmental stimuli including substrate composition and the presence of chemical signals, such as extracts of certain red crustose coralline algae. In this study, seven different substrates common to past research efforts were infused with an extract from the red crustose coralline alga, Hydrolithon boergesenii, and placed on the bottom of the ocean, as were similar plates containing no extract. Substrate plates were deployed during the months following the August 1999 coral-spawning event on a reef near Fort Lauderdale, Florida.
Larvae settled on plates placed on the shoreward side of the reef 2.12 times as often as plates placed on the seaward side of the reef. This difference was significant whether the plates contained algal extracts (p=0.004 by two-way ANOVA) or did not contain algal extracts (P = 0.003 by Two-way ANOVA). Reef location also influenced settling independent of plate composition. Peak settlement was observed on unglazed ceramic tiles on the shoreward side of the reef, while the lowest settlement was observed on glass plates on the shoreward side of the reef. Two-way ANOVA with replication showed significant differences in plate material (P = 0.031), presence or absence of algal extract (P = 0.002), and in the interaction of these variables (P = 0.009). Larvae settled on plates containing the algal extracts 2.60 times as often as plates without algal extract.
Multiple analysis of variance (MANOVA) for the interaction of all variables indicated significant interactions for extract presence (P = 0.002), reef zone location (P = 0.036), and plate material (P = .031). The interactions between algal extract presence and reef zone were also significant (P = 0.009), as were the interactions between plate material and algal extract presence (P = 0.009). Simultaneous MANOVA for all variables was not significant (P = 0.071), probably due to large variation in settling plate composition, variation in the concentration and activity of the algal extracts applied to the plates, as well as variation in the microhabitat across the reef.
Christopher David Petrie. 2000. Effectiveness of Chemical Inducers on Settling and Settlement of Scleractinian Coral Larvae on Various Substrates. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, Oceanographic Center. (310)