Epiphytism is a common phenomenon in macroalgal aquaculture worldwide. This problem can affect the productivity and quality of the farmed species which may have socioeconomic consequences for the human communities that depend on this activity. In southern Chile, the aquaculture of the red macroalga Agarophyton chilense in the area of Maullín River has suffered losses in local production (> 90%) due to the proliferation of the filamentous green epiphyte Rhizoclonium sp. This epiphyte becomes entangled with A. chilense fronds, diminishing its quality and preventing its sale as raw material. Thus, the aim of this study was to investigate the effects of light intensity (90 and 180 μmol photons m⁻² s⁻¹) on the competitive interaction between the epiphyte Rhizoclonium sp. and the basiphyte A. chilense co-cultured at different initial biomass proportions in a replace series experiment. At the end of the experiment, the presence of Rhizoclonium sp. did not affect negatively the growth of A. chilense, but both species showed stress responses (i.e. reduced F_v/F_m and C:N ratio, suggesting nutrient limitation) in co-culture compared with monocultures. The epiphyte-basiphyte interaction was not modulated by light availability at any initial co-culture proportion and could have been related to nutrient availability during experimentation. Using the replacement series approach, an interspecific competition was observed at all initial co-culture proportion under 180 μmol photons m⁻² s⁻¹ while competition was found at the initial co-culture 1:1 under 90 μmol photons m⁻² s⁻¹. Our results suggest that the interaction in co-culture between both A. chilense and Rhizoclonium sp. seems to be regulated by nutrient availability as well as it demands utilization rather than light availability.

附生是全世界大型藻类水产养殖中的常见现象。该问题可能影响养殖物种的生产力和质量，这可能对依赖于此活动的人类社区产生社会经济影响。在智利南部，由于丝状绿色附生植物根瘤菌菌种Rhozoclonium sp的繁殖，毛利河地区的红色大型藻类Agarophyton chilense的水产养殖遭受了当地生产的损失（> 90％）。这种附生植物被奇异奇异菌纠缠在一起，降低了其质量并阻止了其作为原料销售。因此，本研究的目的是研究光强度（90和180μmol光子m ^-2  s ^-1）关于附生根瘤菌属sp。并在替代系列实验中以不同的初始生物量比例共培养了basiphyte A. chilense。在实验结束时，存在Rhizoclonium sp。不会对A. chilense的生长产生负面影响，但是两种物种都表现出胁迫反应（即F _v / F _m降低）。和C：N比，表明营养限制）。在任何初始共培养比例下，附生植物-基生植物之间的相互作用都不受光利用度的调节，并且可能与实验过程中的养分利用度有关。使用更换系列方法中，在所有的初始共培养比例中观察到在180个微摩尔光子的间竞争中号^-2 小号^-1而竞争被发现在初始共培养1：1下90微摩尔光子中号^-2 小号^{- 1}。我们的研究结果表明，这两个之间的共培养的互动A. chilense和Rhizocloniumsp。似乎受养分利用率的调节，并且要求利用率而不是光的利用率。