Synurophyte Algae

Siver, Peter A.

doi:10.1016/b978-012741550-5/50015-5

Cited by 32 publications

(40 citation statements)

References 98 publications

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“…Chrysophytes, which are generally considered to be good competitors at a low phosphorus concentration (Lehman and Sandgren 1985;Siver 2003), are the only taxonomic group that showed a significant decline in Lake Tahoe despite increased nitrogen:phosphorus ratios. These ecophysiological requirements cannot explain the declining trend of this group relative to others, although their resource physiologies can be quite diverse (Nicholls and Wujek 2003).…”

Section: Discussionmentioning

confidence: 99%

Temporal organization of phytoplankton communities linked to physical forcing

2008

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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.

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Section: Discussionmentioning

confidence: 99%

Temporal organization of phytoplankton communities linked to physical forcing

2008

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“…Scaled chrysophytes are freshwater heterokonts in the Chrysophyceae or Synurophyceae with cells covered by flat, overlapping, siliceous scales (Nicholls & Wujek, 2003; Siver, 2003a). They are unicellular or colonial planktonic flagellates commonly found in lakes, ponds, sluggish rivers and wetlands.…”

Section: Introductionmentioning

confidence: 99%

Biogeographic patterns in scaled chrysophytes from the east coast of North America

Siver

Lott

2011

Freshwater Biology

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1. We assessed the distribution of scaled chrysophytes in fresh waters along 3200 km of the east coast of North America (29°to 48°N) to determine any biogeographic patterns in relation to chemical, physical, climatic and spatial variables. 2. Scaled chrysophytes were identified using scanning electron microscopy and counted from 264 waterbodies in nine regions (20 subregions). Eighteen chemical, physical and climate variables were determined for each waterbody. We used Sorensen's similarity index and analysis of similarity (ANOSIM) to evaluate whether the floras differed between regions, subregions, glaciated and non-glaciated areas, as well as within sets of waterbodies with similar chemical and physical characteristics but situated in different regions. Distance-based linear modelling (DISTLM) was used to evaluate the relative importance of the chemical, physical and climate factors in explaining the variability in the assemblages of scaled chrysophytes, and the resulting models were visualised using redundancy analysis (RDA). 3. Significant differences in the flora were found between all regions and most subregions, and between glaciated and non-glaciated areas. Significant differences were also recorded between waterbodies with similar chemical and physical characteristics but situated in different regions. Many species were abundant along specific sections of the latitudinal gradient, but lacking from others. A set of environmental variables explained significant and independent portions of the variation in scaled chrysophytes, with pH and mean minimum July temperature accounting for 20% of the total. 4. The distribution of scaled chrysophytes along the east coast of North America is not homogeneous and there are biogeographic patterns, despite apparent dispersal mechanisms (migratory birds and wind events) that might act to reduce differences between regions. Rather, differences exist even between neighbouring subregions containing sites with statistically similar chemical and physical attributes. Environmental variables clearly play a significant role in determining whether species will inhabit a given site. However, species were not always found in waterbodies likely to support growth, implicating inadequate dispersal, poor transportability or both.

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“…Takahashi, 1978;Wee, 1982;Siver, 1991a;2003;Kristiansen, 2002) are based largely on the morphological design of the siliceous scales and less on the structure of the bristles. However, as observed in this study, the fine detail of the bristles on M. muskokana and M. dispar relative to other species in the genus indicates that closer examination and comparison of bristle structure between species is warranted.…”

Section: Discussionmentioning

confidence: 98%

Taxonomic significance of asymmetrical helmet and lance bristles in the genusMallomonas(Synurophyceae) and their discovery in Eocene lake sediments

Siver

Lott

Wolfe

2009

European Journal of Phycology

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Complex bristle types formed by species in the genus Mallomonas include those with helmet or lance-shaped apices. The ornamentation on each side of the helmet has been thought to be equivalent or symmetrical, whereas on a lance-shaped bristle an expanded portion folds over one side of the shaft to form an asymmetrical structure. We describe, for the first time, helmet bristles with a distinctly asymmetrical design, also formed by the folding of a siliceous membrane over one side of the helmet. We postulate that the asymmetrical helmet represents a structure that combines the formation of a symmetrical helmet and a lance-shaped design on the same bristle. Further, we report structurally similar asymmetrical helmet bristles, lance-shaped bristles and scales that are unambiguously assigned to Mallomonas asmundiae in Middle Eocene sediments from a maar lake in northern Canada, supporting the hypothesis that scale and bristle morphology in the Synurophyceae has undergone extensive prolonged evolutionary stasis. Given differences in scale morphology and the presence of asymmetrical helmet bristles, we transfer the North American endemic Mallomonas acaroides var. muskokana to the rank of species. Further, we formally describe Mallomonas dispar and M. lancea, fossil species with asymmetrical helmet bristles and lance-shaped bristles, respectively. The taxonomic and biogeographic significance of asymmetrical and lance-bearing bristles is discussed.

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Synurophyte Algae

Cited by 32 publications

References 98 publications

Temporal organization of phytoplankton communities linked to physical forcing

Temporal organization of phytoplankton communities linked to physical forcing

Biogeographic patterns in scaled chrysophytes from the east coast of North America

Taxonomic significance of asymmetrical helmet and lance bristles in the genusMallomonas(Synurophyceae) and their discovery in Eocene lake sediments

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