The present study is aimed at providing a primary description of the nutrient availability through macrophyte detritus from the brown kelp Lessonia trabeculata in the bay of Punta de Tralca, a semi-sheltered, rocky subtidal habitat on the coast of central Chile. The abundance and immediate fate of the detritus were studied, to establish baseline knowledge of the nutrient subsidy system around this brown kelp. We counted 410 live kelps on an area of 2400m2, distributed over 39 patches with a mean kelp density of 0.56± 0.13SD. In 48m2, 346 detrital fragments were counted, estimated to a total biomass of 7857.9g. The data modelling revealed an interactive effect of the presence of live kelp in across the depth levels on the detritus abundance. We predict the highest amount of drift kelp in shallow (6.4m-8.3m) kelp beds and at an intermediate depth 8.3m-10.5m in barren areas. We conclude that detritus abundance can be predicted based on environmental variables. Retention rates within kelp beds were lower than in barren sites, and were indeed depending on physical characteristics of the detritus type. We conclude that drift kelp leaving the source areas habitat consists of detritus with fronds, while stipes are retained and consumed locally.
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