Qualitative modelling of the kelp forest of Lessonia nigrescens Bory (Laminariales: Phaeophyta) in eulittoral marine ecosystems of the south–east Pacific: an approach to management plan assessment

This contribution aims at the assessment of the sustainability of a management plan for Lessonia nigrescens in Chilean coastal ecosystems, specially when the harvest pressure could be increased due to that this macroalgae is considered as a food source for the abalon (Haliotis discus hannoi) farming along the Chilean coast. Three qualitative conceptual models were developed and compared; the first and second ones assuming homogeneous and heterogeneous environmental conditions, respectively, and the third expanded one considering eco-social components under the assumption of environmental heterogeneity. For all these models, the factors described by Vásquez Bot. Mar. 38 (1995) 251] were included in the management plan for the harvesting of brown macroalgae. Based on Levins's Loop Analysis, the system will have a just weakly unstable moving equilibrium if the harvesting activities do not negatively affect the macrophyta's reproduction and recruitment processes. Therefore, coincidence of reproduction and/or recruitment with harvesting must be avoided in a putative management plan. Regarding the qualitative predictions of the system's behaviour after negatively affecting reproduction and recruitment, only an ecological model assuming a heterogeneous environment shows realistic responses in comparison to experimental studies on the same species. This contribution is the first approach considering the dynamical behaviour of L. nigrescens and its surroundings. Nevertheless, further models, based on the same modelling theory, may integrate more variables from social and economical fields in order to improve the scope of this complex system. Further comparative studies should focus on the assessment of the significance of the structural functions of L. nigrescens and other macroalgae for the conservation of this benthic system.