Premium
Herbivory and Structure in a Midlittorial Rocky Community: A Case in Southern Chile
Author(s) -
Jara H. Fernando,
Moreno Carlos A.
Publication year - 1984
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1939455
Subject(s) - herbivore , ecology , biology , ecological succession , dominance (genetics) , abundance (ecology) , intertidal zone , crustose , algae , biochemistry , gene
The abundance of the red alga Iridaea boryana and the role of herbivores in structuring the mid—intertidal community were studied during a 2—yr period at a semiprotected site in Mehuin, Chile. Herbivore densities wee manipulated on three contiguous rocky areas having similar initial communities. In one treatment, herbivores were totally removed every 15 d.; herbivores were maintained at double the control density in a second treatment; and an undisturbed area was used as a control. Percent cover of sessile organisms was measured at monthly intervals from September 1978 to September 1980. Changes which occurred in the 2—yr period are interpreted as follows. Herbivore removal allowed high cover (>80%) of I. boryana. Herbivore addition and a natural increase in herbivores on the control caused a drastic decline in this alga, and the substrate became dominated by barnacles and crustose algae. Ephemeral algae (e.g., Petalonia and Scytosiphon) were frequent in the presence of herbivores (control and addition), while in the absence of herbivores, invasion by ephemerals was precluded by the high abundance of I. boryana. In winter, herbivores and high wave action caused a significant reduction in algal abundance, which did not occur on the removal rock. Light seemed to be the main limiting resource in the absence of herbivores, where I. boryana was the competitive dominant. Two patterns of community development were found after new space (burned and scraped) was created. (1) Succession following spring denudations began with algal colonization leading to a dominance of I. boryana. (2) Succession following autumn denudations began with barnacles and terminated in a community dominated by barnacles and crustose algae. The natural regional mosaic of I. boryana dominance and barnacles plus crustose algae depends, locally, on the season of the last disturbance and on herbivore abundance. Differences between this southern Chilean and equivalent North American intertidal communities are discussed.