Six new chrysophycean stomatocysts ornamented with reticulum from the Great Xing’an Mountains, China

Six new chrysophycean stomatocysts ornamented with reticulum were illustrated based on SEM observation. They were described following the guidelines of the International Statospore Working Group (ISWG). All samples were collected from the Great Xing’an Mountains, China. Their taxonomic characteristics and habitats were described to provide new information on the biodiversity of chrysophycean stomatocysts. As is common with many morphotypes, their biological affinities remain unknown.     

Chrysophyte reproduction and resting cysts: A paleolimnologist's primer

Chrysophyte algae produce siliceous resting cysts (stomatocysts) that are becoming an increasingly useful class of paleoecological indicator microfossils. This paper provides a review of the role that stomatocysts play in the life cycle and reproductive ecology of freshwater planktonic chrysophytes. Such information provides paleolimnologists with greater insight into the ecology of the vegetative, planktonic growth phase of species contributing stomatocysts to lacustrine microfossil assemblages. Specific chrysophyte reproductive characteristics discussed include: temporal dynamics of vegetative growth and encystment, cyst induction, cyst survivorship, germination requirements and recruitment strategies. This information serves as an introduction to a special issue of the Journal of Paleolimnology which is dedicated to the Application of Chrysophyte Stomatocysts in Paleolimnology.This is the first in a series of four papers published in this dedicated issue entitled Application of Chrysophyte Stomatocysts in Paleolimnology. Dr. C. D. Sandgren served as guest editor for these papers.     

Chrysophycean cysts in Sierra Nevada (California) lake sediments: paleoecological potential

Thirty-three lakes in the Sierra Nevada range of California were investigated as part of a paleoecological study of the potential effects of acid deposition on sensitive lake/watershed ecosystems. Chrysophyte cysts from surface sediment samples were analyzed and compared with data on pH and alkalinity. This paper identifies the twenty-five dominant chrysophyte cyst taxa and provides information on their morphology, abundance, distribution and ecology.Chrysophycean cysts were generally abundant and well-preserved in lake sediments of our study sites. Twelve taxa occurred in more than twenty of the thirty-three lakes; these taxa were often quite abundant. In contrast, only nine taxa occurred in ten or fewer lakes. Abundance Weighted Mean (AWM) pH varied from 6.45 to 8.34 and AWM alkalinity varied from 46 to 588 eq/L. We delineated pH preference categories, based on AWM pH values and frequency diagrams of cyst abundance vs. lake-water pH. We classified five taxa as acidophilous, nine as circumneutrals, six as alkaliphilous and five as indifferent. Given that the cyst types differ greatly in their abundance relative to pH and alkalinity, it is clear that they have potential for paleolimnological studies of Sierra lakes biogeochemistry.     

金藻孢囊在水环境变化研究中的应用

金藻孢囊是金藻生殖过程的特有产物,在淡水环境中广泛存在,其硅质外壳易在沉积物中保存。金藻孢囊的孔、领、环带以及表面纹饰特征是其鉴定分类的主要依据。金藻孢囊对水环境变化响应敏感,因而被广泛应用于水环境变化研究中,包括古温度和古水文重建、水体富营养化和酸化评估等领域。已有的研究主要集中在北美和欧洲地区,其他区域研究相对较少。相比于其他生物指标,金藻孢囊鉴定相对复杂,不利于其广泛应用。因此,未来应优化金藻孢囊鉴定分类方法,提高鉴定统计效率。其次,加强金藻孢囊的现代过程调查,尤其在欧洲和北美以外的地区,以揭示全球不同地区金藻孢囊多样性及其生态属性。在此基础上,加强金藻孢囊在泥炭地环境演变、生物地理学等研究领域的应用。     

The stomatocyst of Mallomonas acaroides v. muskokana (Chrysophyceae)

The stomatocyst of Mallomanas acaroides v. muskokana is described based on observations made from both live populations and surface sediment remains. The cyst is slightly ovate in shape, covered with evenly spaced, ornamented spines and has a short cylindrical collar with a variable apex and internal annulus surrounding the pore. The spines have a thickened base, a cylindrical middle section and a flattened apex with a ring of finger-like projections. Several immature stages of development are described and the stomatocyst is compared to those described for phylogenetically similar species. Complementary investigations of stomatocysts from both living (planktonic) and sediment collections can greatly facilitate the identification of stomatocyst morphotypes.This is the second in a series of four papers published in this dedicated issue entitled Application of Chrysophyte Stomatocysts in Paleolimnology. Dr. C.D. Sandgren served as guest editor for these papers.