Abstract
Structural complexity spanning fine to broad spatial scales can influence the distribution and activity of key organisms within marine ecosystems. However, the relative importance of hard (e.g., corals) and/or soft (e.g., macroalgae) structural complexity for marine organisms is often unclear. This study shows how both broad-scale (seascape configuration of coral structure) and fine-scale habitat complexity (structure height, number of holes, and presence of macroalgae) can influence the abundance and spatial ecology of reef fish. Underwater visual census of fish, surveys of habitats, remote underwater videos, and behavioral observations by following individual fish were used to quantify fine-scale habitat characteristics (e.g., complexity, coral structure height, macroalgae presence) and the abundance, size structure, and behavior (rates of herbivory, tortuosity ratios and total distance travelled) of abundant parrotfish. Both seascape configuration and macroalgae influenced the patterns of fish abundance and rates of herbivory. However, these relationships varied with trophic groups and ontogenetic stages. Abundance of adult and intermediate-phase parrotfishes was positively influenced by densely aggregated coral structures, whereas juvenile abundance was positively influenced by the presence of macroalgae. Foraging path and bite rates of an abundant parrotfish, Chlorurus spilurus, were not influenced by coral structure configuration or height, but the presence of macroalgae increased the bite rates of all juvenile parrotfish. Our results suggest that a combination of seascape configuration, fine-scale habitat complexity, and microhabitat selectivity influence reef fish community structure and foraging behavior, thus altering herbivory. However, these relationships can differ among functional groups of fish and life-history stages. Information on these fish–habitat interactions is critical for identifying habitats that facilitate ecological functions and ensures the successful management and conservation of essential habitats.
Highlights
Landscape configuration and habitat heterogeneity can influence both distribution patterns of organisms and how ecological processes operate over fine to broad spatial scales [1,2]
We studied the coupling between broad- and fine- scale complexity by addressing the following questions: How does complexity measured at different spatial scales influence the distribution and abundance of (1) fish from different functional groups and (2) scraping/excavating parrotfish at different life history stages, and (3) foraging and feeding patterns of scraping/excavating parrotfish
Rugosity calculated by photogrammetry in Remote underwater videos (RUV) had a significant positive effect on the total fish abundance. Both configuration of hard coral structure and the presence of macroalgae growing on the coral structure influenced reef fish abundance and herbivory
Summary
Landscape configuration and habitat heterogeneity can influence both distribution patterns of organisms and how ecological processes operate over fine to broad spatial scales [1,2]. By understanding the relationships between these patterns and processes we can predict how changes within the landscape (e.g., habitat loss and fragmentation) might alter biodiversity and ecosystem function [3]. Species distribution of birds, moths, and butterflies are mainly affected by landscape heterogeneity, while richness of amphibians and reptiles are more closely related to the abundance of specific types of habitats [4]. Loss of complexity and specific niches during the replacement of old growth forest with palm oil plantations for instance, have had devastating effects on the abundance and biodiversity of wildlife, despite the habitat type (forest) still being present [5]. Habitat preferences are species-specific, and what might be beneficial for one species might not be advantageous for others [6]
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