Browsing by Author "Montecino, Vivian"

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    Chlorophyll-a MODIS mesoscale variability in the Inner Sea of Chiloe, Patagonia, Chile (41-43 degrees S): Patches and Gradients?
    (UNIV VALPARAISO, 2010) Lara, Carlos; Miranda, Marcelo; Montecino, Vivian; Luis Iriarte, Jose
    Satellite images are powerful tools to describe meso-and large-scale spatial structures, thus helping in the comprehension of the physical-biological processes taking place in the ocean. The objective of this study was to establish spatial (horizontal) and temporal (seasonal) variability of the autotrophic biomass measured as satellite chlorophyll concentrations (Chl-a) in the Inner Sea of Chiloe (41.0-43.5 degrees S). Remote sensing (MODIS) and geostatistics (Variograms) approaches were used to characterize Chl-a spatial-horizontal structure at the surface layer by anisotropic estimation of the Chl-a average values. A total of 27 selected images were analyzed and grouped into summer, spring, fall and winter seasons during the January 2003-December 2005 period. Image temporal analysis showed a classic pattern for the autotrophic biomass dynamics of cold temperate coastal areas, with highest Chl-a values occurring during the spring-summer period, and the lowest values during the fall-winter season. Image spatial analysis indicated that Chl-a is distributed into more homogeneous and larger than 50 km patches, during the fall-winter seasons, whereas during the spring-summer seasons more heterogeneous and smaller than 30 km patches were found. The anisotropy analysis showed a predominant angle in the East-West direction, suggesting the role of water column stratification as a modulating process of surface Chl-a spatial variability in the Inner Sea of Chiloe area.
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    Factors influencing the presence and relative abundance of Didymosphenia geminata. Impact on the composition of diatom assemblages over a broad latitudinal gradient in Chilean rivers
    (TAYLOR & FRANCIS LTD, 2025) Carrevedo, María Laura; Dézerald, Olivier; Alfaro, Fernando; Bustamante, Ramiro Ociel; Molina, Ximena; Muñoz, Paola Andrea; Montecino, Vivian
    This study explored the abiotic factors influencing Didymosphenia geminata blooms and the combined effect of D. geminata and abiotic factors on local diatom assemblages in 13 Chilean watersheds across a broad latitudinal range (37 degrees-47 degrees S). To understand the multi-scale drivers, we used generalized linear mixed-effects models to assess the abiotic factors most influential on D. geminata presence and relative abundance. We then explored the effects of D. geminata and abiotic factors on the alpha- and beta-diversity of diatom assemblages using generalized linear models and permutational analyses of variance, respectively. Three watersheds lacked D. geminata and another three had low relative abundance. Seasonally, the relative abundance of D. geminata was significantly higher in spring than in autumn. We found positive correlations between elevation, river order, pH and D. geminata presence and relative abundance, while water temperature was negatively correlated with D. geminata relative abundance. Diversity indices were significantly influenced by watershed and to a lower extent by the presence of D. geminata. We found significant spatial (i.e. between watersheds along a south-north latitudinal gradient) and temporal (i.e. between seasons) variations in beta-diversity of diatom assemblages. Moreover, increasing relative abundance of D. geminata in the assemblage was correlated with lower diatom diversity. In addition, the compositions of diatom assemblages with D. geminata were more alike and less variable than those in non-invaded sites. This study is a first attempt to understand the multi-scale drivers of diatom assemblages in Chilean lotic ecosystems.