UCN-CEAZA
Herbivorous amphipods inhabit protective microhabitats within thalli of giant kelp Macrocystis pyrifera.
Gutow, L., Long, J., Cerda, O., Hinojosa, I., Rothäusler, E., Tala, F., & Thiel, M.
Many small marine herbivores utilize specific algal hosts, but the ultimate factors that shape host selection are not well understood. For example, the use of particular microhabitats within algal hosts and the functional role of these microhabitats have received little attention, especially in large algae such as kelps. We studied microhabitat use of the herbivorous amphipod Peramphithoe femorata that inhabits nest-like domiciles on the blades of giant kelp Macrocystis pyrifera. The vertical position of nest-bearing blades along the stipe of the algal thallus and the position of the nests within the lateral blades of M. pyrifera were surveyed in two kelp forests in northern-central Chile. Additionally, we conducted laboratory and field experiments to unravel the mechanisms driving the observed distributions. Peramphithoe femorata nests were predominantly built on the distal blade tips in apical sections of the stipes. Within-blade and within-stipe feeding preferences of P. femorata did not explain the amphipod distribution. Amphipods did not consistently select distal over proximal blade sections in habitat choice experiments. Mortality of tethered amphipods without nests was higher at the seafloor than at the sea surface in the field. Nests mitigated mortality of tethered amphipods, especially at the seafloor. Thus, protective microhabitats within thalli of large kelp species can substantially enhance survival of small marine herbivores. Our results suggest that differential survival from predation might be more important than food preferences in determining the microhabitat distribution of these herbivores.
Año: 2012
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Referencia APA: Gutow, L., Long, J., Cerda, O., Hinojosa, I., Rothäusler, E., Tala, F., & Thiel, M. (2012). Herbivorous amphipods inhabit protective microhabitats within thalli of giant kelp Macrocystis pyrifera. Marine Biology, 159(1), 141-149.
Gene expression analysis in Mytilus chilensis populations reveals local patterns associated with ocean environmental conditions.
Núñez-Acuña, G., Tapia, F., Haye, P., & Gallardo-Escárate, C.
Marine ecosystems involve relationships between genomic interactions of marine populations with shared biogeographic ranges and the environmental conditions. These relationships, studied mainly through neutral DNA markers, are not always consistent with actual biogeographic patterns or the evolutionary history of marine species. In addition, increased information at functional genomic level from non-model species allows the study of adaptive responses in marine populations. This work reports local transcriptomic patterns in populations of the mussel Mytilus chilensis and their correspondence with oceanographic variability in southern Chile. Analysis of gene expression patterns was conducted through qPCR of seven candidate genes involved in the response to environmental stress (HSP70, HSP90), iron metabolism (Ferritin), pathogens (Mytilin B, Defensin) and oxidative stress (SOD-CuZn, Catalase) in at five study sites located in southern Chile, from Valdivia (39°56′S–73°36′W) to Melinka (43°52′S–73°44′W). Multivariate and correlation analyses were used to assess the relationship between levels of individual gene expression and site features characterized using satellite data on surface temperature, chlorophyll concentration and total suspended sediments. Two main groups of sites with differential patterns of gene expression were identified. Individuals exposed to higher temperatures showed an overexpression of HSP70, HSP90 and Ferritin genes. The expression of SOD-CuZn and Catalase was correlated with local chlorophyll-a (i.e. food availability for mussels), although with opposite correlations. In addition, Mytilin B showed higher levels of expression in areas with higher freshwater influence. Patterns of gene expression across the region of interest suggest that spatial variability in environmental conditions induce phenotypic changes in different populations of the same mussel species. In addition, the analysis of expression patterns in candidate genes can reveal local patterns in populations where other molecular markers show no genetic structure.
Año: 2012
Palabras claves: Gene expression; Mytilus chilensis; Adaptative response; Environmental stress; Thermal tolerance; Sea surface temperature
Referencia APA: Núñez-Acuña, G., Tapia, F., Haye, P., & Gallardo-Escárate, C. (2012). Gene expression analysis in Mytilus chilensis populations reveals local patterns associated with ocean environmental conditions. Journal Of Experimental Marine Biology And Ecology, 420-421, 56-64.
Testing sustainable management in Northern Chile: harvesting Macrocystis pyrifera (Phaeophyceae, Laminariales). A case study.
Borras-Chavez, R., Edwards, M., & Vásquez, J.
Kelp harvesting in northern Chile is managed by local fishermen and is part of an organized industry. However, the lack of standardized harvesting protocols has made regulation difficult. This, in combination with the impacts of oceanographic disturbances has resulted in some kelp populations being considerably reduced during the last decade. Consequently, harvest methods that maintain kelp resources are sorely needed if harvesting is to remain a viable industry in Chile. Here, experiments were done to identify sustainable methods for harvesting Macrocystis pyrifera along the coast of northern Chile. Three methods were compared with regard to their impacts on kelp populations; one that involves extracting half of the fronds from each individual in a population, one that involves extracting all the fronds from half of the individuals in a population, and a third that involves extracting all the fronds from all of the individuals in a population (i.e., the method currently used). Following this, populations were evaluated over a 2-month period to monitor re-growth of the remaining individuals and recruitment of new individuals, as well as changes in understory algal diversity and herbivore abundance. Our results indicate that removing half of the fronds from each individual in a population was the best method for maintaining the resource for future harvest because, it (1) maintains rapid growth of new fronds on the harvested individuals, (2) promotes recruitment of new individuals, and (3) reduces herbivore densities through physical abrasion. Consequently, this method is recommended for future harvesting of M. pyrifera in Northern Chile.
Año: 2012
Palabras claves: EcologyKelp, harvesting, Macrocystis, Phaeophyta, Sustainability
Referencia APA: Borras-Chavez, R., Edwards, M., & Vásquez, J. (2012). Testing sustainable management in Northern Chile: harvesting Macrocystis pyrifera (Phaeophyceae, Laminariales). A case study. J Appl Phycol, 24(6), 1655-1665.