Abstract
Habitat modification of coral reefs is becoming increasingly common due to increases in coastal urban populations. Coral reef fish are highly dependent on benthic habitat; however, information on species-specific responses to habitat change, in particular with regard to trophic strategies, remains scarce. This study identifies variation in the trophic niches of two herbivorous coral reef fishes with contrasting trophic strategies, using Stable Isotopes Bayesian Ellipses in R, along a spatial gradient of changing coral reef habitats. In the parrotfish, Chlorurus bleekeri, a roving consumer, the range of 15N (positive) and 13C (negative) and their niche area (positive) displayed significant relationships with the amount of rubble in the habitat. In contrast, the farming damselfish, Dischistodus prosopotaenia, showed a narrow range of both 15N and 13C, displaying little change in niche parameters among sites. This may indicate that parrotfish vary their feeding according to habitat, while the damselfish continue to maintain their turf and invertebrate resources. Assessing isotopic niches may help to better understand the specific trophic responses to change in the environment. Furthermore, the use of isotopic niches underline the utility of stable isotopes in studying the potential impacts of environmental change on feeding ecology.
Highlights
The effects of terrestrially-derived disturbance gradients in marine waters across coral reefs have been noted from many parts of the world (Edinger et al, 1998; Mallela et al, 2004; Fabricius et al, 2005; Lirman and Fong, 2007; Teichberg et al, 2018)
This study examines the variation of the trophic niches of the two herbivorous fish species across an environmental gradient, assuming that variation in habitat degradation may alter their trophic niche space through modification of available benthic food items; it is assumed that variation in the isotopic niche will be greater in C. bleekeri than D. prosopotaenia due to the latter’s predisposition to self-maintain its nutritional resources
This study was conducted in November 2014, at six islands of the Spermonde Archipelago, Indonesia varying in distance from the city of Makassar (Figure 1)
Summary
The effects of terrestrially-derived disturbance gradients in marine waters across coral reefs have been noted from many parts of the world (Edinger et al, 1998; Mallela et al, 2004; Fabricius et al, 2005; Lirman and Fong, 2007; Teichberg et al, 2018). Anthropogenic impacts can alter the resource availability and predator-prey relationships on a coral reef affecting habitat use and the trophic niche of the biotic constituents (Jones and Syms, 1998; Syms and Jones, 2000). Changes in coral reef communities along disturbance gradients may be associated. The trophic structure of coral reef communities is highly complex, and discerning the specific change of habitat use of any individual species can be challenging due to the high biological diversity on reefs (Fenner, 2012). Revealing trophodynamics of a coral reef community may allow for better interpretation of community change under varying environmental stress (Done, 1992) and help facilitate management decisions that break negative feedback loops (Glaser et al, 2018)
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