کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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4532705 | 1626180 | 2011 | 10 صفحه PDF | دانلود رایگان |

Large microalgae, such as diatoms can generate high levels of biomass, unlike small phytoplankton components in the austral fjords and estuarine systems of Chile. We propose a cell-size-based diversity index (H′sizeH′size) measured as chlorophyll-a concentrations (Chl-a) to determine if the relationship between H′sizeH′size versus Chl-a results in a hump-shaped distribution considering: (i) the intermediate disturbance hypothesis, (ii) phytoplankton size colonization strategies, and (iii) predictions of low H′sizeH′size with high or low Chl-a levels and peaks in H′sizeH′size with intermediate Chl-a levels. The functional responses of phytoplankton are tightly coupled to environmental conditions. Could, then, the relationship between H′sizeH′size and Chl-a occur on a particular temporal/spatial scale? Herein, we analyze data from three CIMAR-Fiordos cruises performed between 2001 and 2002 within areas of different continental influence from 41° to 47°S. Phytoplankton samples were taken at different locations and depths, filtered to obtain Chl-a with and without size-fractionation (>20 μm, <11 μm), and then used to calculate H′sizeH′size. Total Chl-a (TChl-a) changed by two orders of magnitude between different cruises and areas. The small phytoplankton fraction (<11 μm) dominated with low TChl-a values (≤1 mg m–3), as did the large phytoplankton fraction (>20 μm) with high TChl-a values (≥1 mg m–3). Although other relationships can be found on smaller scales, we determined unimodal (hump-shaped) relationships through quadratic quantile regressions between the H′sizeH′size index and TChl-a and between H′sizeH′size or TChl-a and the abiotic factors when considering data from all three cruises and areas. H′sizeH′size versus TChl-a was driven by one variable or by different combinations of variables, and according to low–high disturbance level: high TChl-a and larger size classes predominated in deeper upper mixed layers having higher light availability, whereas shallower upper mixed layers with lower light availability presented lower TChl-a and predominantly smaller cell size classes. Thus, the larger temporal/spatial scales used here allowed us to test the hypothesis of the unimodal expression of phytoplankton patterns in these coastal ecosystems.
Journal: Continental Shelf Research - Volume 31, Issues 3–4, 1 March 2011, Pages 272–281