colorful niches of phytoplankton shaped by the spatial connectivity in a large river ecosystem a riverscape perspective色彩斑斓的利基市场的浮游植物的空间连接在一个大的河流生态系统riverscape角度.pdfVIP

Colorful Niches of Phytoplankton Shaped by the Spatial Connectivity in a Large River Ecosystem: A Riverscape Perspective 1 1 2 Jean-Jacques Frenette *, Philippe Massicotte , Jean-Franc¸ois Lapierre ´ ´ ´ ` ` ` ´ ´ ´ ´ 1 Departement de Chimie-Biologie, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, Quebec, Canada, 2 Departement des sciences biologiques, Universite du Quebec ` ´ ´ ´ a Montreal, Montreal, Quebec, Canada Abstract Large rivers represent a significant component of inland waters and are considered sentinels and integrators of terrestrial and atmospheric processes. They represent hotspots for the transport and processing of organic and inorganic material from the surrounding landscape, which ultimately impacts the bio-optical properties and food webs of the rivers. In large rivers, hydraulic connectivity operates as a major forcing variable to structure the functioning of the riverscape, and–despite increasing interest in large-river studies–riverscape structural properties, such as the underwater spectral regime, and their impact on autotrophic ecological processes remain poorly studied. Here we used the St. Lawrence River to identify the mechanisms structuring the underwater spectral environment and their consequences on pico- and nanophytoplankton communities, which are good biological tracers of environmental changes. Our results, obtained from a 450 km sampling transect, demonstrate that tributaries exert a profound impact on the receiving river’s photosynthetic potential. This occurs mainly through injection of chromophoric dissolved organic matter (CDOM) an