Temporal organization of phytoplankton communities linked to physical forcing

Abstract

The performance of individual phytoplankton species is strongly governed by the thermal stratification's impact on vertical mixing within the water column, which alters the position of phytoplankton relative to nutrients and light. The present study documents shifts in phytoplankton structure and vertical positioning that have accompanied intensified long-term stratification in a natural ecosystem. Ordination analysis is used to extract gradients in phytoplankton composition in Lake Tahoe, an extremely nutrient-poor lake, over a 23-year period of records. Community structure in the 1980s was associated most strongly with resource availability (low nitrogen to phosphorus ratios, deeper euphotic zone depth), while intensified stratification dominated the phytoplankton structure since the late 1990s. Within diatoms, small-sized cells increased with reduced mixing, suggesting that suppressed turbulence provides them with a competitive advantage over large-sized cells. Among the morphologically diverse chlorophytes, filamentous and coenobial forms were favored under intensified stratification. The selection for small-sized diatoms is accompanied by a shoaling trend in their vertical position in the water column. In contrast, the motile flagellates displayed a deeper vertical positioning in recent years, indicating that optimal growth conditions shifted likely due to reduced upwelling of nutrients. As the thermal stratification of lakes and oceans is strongly linked to climate variables, the present study confirms that climate warming will alter phytoplankton structure and dynamics largely through effects on nutrient availability and sinking velocities. Intensified stratification should favor the expansion of small-sized species and species with the capability of buoyancy regulation, which may alter primary productivity, nutrient recycling, and higher trophic productivity.

Reorganization of algal communities in the Lake of the Woods (Ontario, Canada) in response to turn‐of‐the‐century damming and recent warming

“…7D). Additionally, small planktonic C. pseudostelligera, often associated with increased thermal stability (Winder and Hunter 2008) and low nutrient conditions (Wunsam et al 1995), decreases during this time (from . 15% to , 1% relative abundance) (Fig.…”

“…), indicating that elevated TP is not a necessary pre-condition for blooms. Other warming-mediated effects include phenological changes in primary production that have been found to lead to trophic mismatches in freshwater aquatic ecosystems (Winder and Schindler 2004;Adrian et al 2006), with cascading implications throughout food webs. At a finer taxonomic scale, climate-driven changes in diatom species composition resulting in an increase in planktonic taxa have been reported across a wide spectrum of lake ecosystems throughout the Northern Hemisphere (Smol et al 2005;Smol and Douglas 2007;Rü hland et al 2008).…”

“…A common thread throughout these various studies is the biological implications of recent temperature increases (particularly during winter) on lake ice phenology (i.e., ice-off date, ice-on date, ice-free period) and on water column properties. These climate metrics were found to substantially alter aquatic habitat availability and quality as well as the onset, duration, and strength of the thermal stratification period (Gerten and Adrian 2002;Winder and Schindler 2004;Peeters et al 2007). Although the effects of climatic warming on lake ecosystems are complex and the degree of ecological change will undoubtedly vary among lakes and lake types (Keller 2007), there appears to be some degree of commonality in the response of aquatic biota to this warmer climate regime (Smol et al 2005;Blenckner et al 2007;Rü hland et al 2008).…”

Biogeochemical processes controlling oxygen and carbon isotopes of diatom silica in Late Glacial to Holocene lacustrine rhythmites

“…The two possible mechanisms for this input are enhanced vertical mixing of the water column that upwells nutrient-rich waters from the hypolimnion to the lake surface (Margalef, 1978;Winder and Hunter, 2008), and nutrient injection by increased runoff (Harris, 1986). Turbulence will be, in turn, dependent on both external forcing such as wind stress, surface heat flux, turbidity currents or river inflow and outflow, among others, and lake morphometry constraints (Imboden and Wüest, 1995).…”

Temporal changes of phytoplankton community at different depths of a shallow hypertrophic reservoir in relation to environmental variables

“…Temporal variability in the structure and function of the phytoplankton community in a lake is of fundamental importance to lake metabolism (Calijuri et al, 2002), studies of which are important to aid understanding of lake ecosystems as well as for effective management of lake water quality. Many studies have investigated temporal changes in phytoplankton communities in lakes, including long-term changes (Reynolds, 1984;Romo and Miracle, 1994;Chen et al, 2003;Winder and Hunter, 2008) and seasonal dynamics (Salmaso, 1996(Salmaso, , 2002Wang et al, 2007). Typical seasonal succession models of the phytoplankton community in temperate lakes shows that Bacillariophyceae dominate during early spring, Chlorophyceae dominate in late spring, and Cyanophyceae dominate during summer (Reynolds, 1984).…”