Abstract
The abundance and the distribution of trophic resources available for consumers influence the productivity and the diversity of natural communities. Nevertheless, assessment of the actual abundance of food items available for individual trophic groups has been constrained by differences in methods and metrics used by various authors. Here we develop an index of food abundance, the framework of which can be adapted for different ecosystems. The relative available food index (RAFI) is computed by considering standard resource conditions of a habitat and the influence of various generalized anthropogenic and natural factors. RAFI was developed using published literature on food abundance and validated by comparison of predictions versus observed trophic resources across various marine sites. RAFI tables here proposed can be applied to a range of marine ecosystems for predictions of the potential abundance of food available for each trophic group, hence permitting exploration of ecological theories by focusing on the deviation from the observed to the expected.
Highlights
Our study aims at describing general patterns of relative abundance of food available for trophic groups among various marine habitats
The comparison of the abundances of food items estimated by means of the proposed method with field data shows some differences, but trends coincide
As for the other trophic categories, herbivores, detritus feeder resources (DeF) and DeFHe, as well as mDeF, are slightly higher when calculated by relative available food index (RAFI), whereas mCa, mHe, Om and DeFS are slightly lower than actual
Summary
A classification of ecosystems based on the abundance of each trophic resource is theoretically possible [10]. The amount of plant biomass potentially available for macroherbivores will inevitably be much higher in seagrass meadows than unvegetated sandy substrata or marine caves [11]. The abundance of food available for macrocarnivores is higher on coral reefs than shallow seaweed meadows [12,13]. Extending such generalizations, food resources available to different trophic groups can be evaluated by considering habitat constraints
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