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Composition and distribution of diatom assemblages from core and surface sediments of a water supply reservoir in Southeastern Brazil. Biota Neotropica. 16(2): e20150129. http://dx.doi.org/10.1590/1676-0611- BN-2015-0129 Abstract: Fresh water biodiversity is an increasing concern due to growing human impact. Herein, we report a long-term survey (ca. 90 years) of sedimentary diatoms and the modern flora from surface sediments and their biodiversity changes along a eutrophication gradient. Study was carried out in one of the most important water supply reservoirs (Guarapiranga Reservoir) of Sã o Paulo Metropolitan Region, Brazil. Results are based on 75 core subsamples (subfossil assemblages from core) previously dated by 210 Pb and 14 samples from surface sediments (modern assemblages). Overall, 84 taxa were reported, belonging to 30 genera, 71 species and eight non-typical varieties, besides five probable new taxa. Results expanded two new additions for the Brazilian diatom flora (Chamaepinnularia submuscicula and Stauroneis acidoclinata) and 30 infrageneric taxa for the state of Sã o Paulo. 47.6% of total taxa inventoried were accounted exclusively for the subfossil assemblages indicating a significant biodiversity change over time. Access to past oligotrophic conditions and to contemporary mesotrophic regions of the Guarapiranga Reservoir accounted for these new additions representing 25% of the total diatom flora. Decline in the total species number along the trophic state gradient occurred for subfossil and modern assemblages. This pattern was even clearer when considering the changes in species richness over time. Eunotia with 21 taxa was the far most represented genera particularly in the oligotrophic phase. During the transitional period , richness gradually declined. With the onset (in the 1970s) and the major eutrophication period (since ca. 1990) occurred a drastic reduction in richness and the replacement of oligotrophic to eutrophic species. Human management also caused abrupt changes in richness. Marked decline occurred (1933) assotiated with hydrological impacts (water discharge increase) with the initial use of the reservoir as a public water supply. Unlike, sudden increase occurred probably associated with the application of algaecide to control cyanobacterial blooms. Present findings highlight the need for surveying the diatom assemblages in protected environments or in less degraded conditions for biodiversity assessment. Furthermore, reinforce the use of paleolimnological approach as in many cases the only tool to assess biodiversity changes encompassing time scales relevant to human-induced degradation and pre-anthropogenic impacts. Keywords: Bacillariophyta, biodiversity change, eutrophication, Guarapiranga Reservoir, paleolimnology, species richness.FAUSTINO, S.B., FONTANA, L., BARTOZEK, E.C.R., BICUDO, C.E.M., BICUDO, D.C. Composic¸ão e distribuic¸ão das diatomáceas de perfil sedimentar e sedimentos superficiais em reservatório de abastecimento no Sudeste do Brasil. Biota Neotropica. 1...

We present a 2000-year high-resolution diatom record from Bosten Lake (Yanqi Basin, Xinjiang), which is the largest inland freshwater lake in China. Our aims were to investigate the influence of climate change and human activity on its aquatic ecology during the late Holocene. During AD 280–480, a low water level and high salinity occurred, based on the dominance of epipelic and brackish diatoms. In addition, the diatom stratigraphy, combined with records of mean grain size and carbonate content, suggests that the lake experienced a high level of eolian input from the surrounding dunes. We hypothesize that during this interval, Loulan Kingdom, an important city of the Han Dynasty, located downstream of Bosten Lake, was abandoned due to the increasing scarcity of water resources and related harsh environmental conditions, including stronger eolian activity, which were the consequences of climate change. The dominance of meso-eutrophic small fragilarioid diatoms coincides with warm and arid intervals which also correspond to intensified human activity. These intervals correspond to the development of the Tang Dynasty (from ~AD 600), the ‘Medieval Warm Period’ (AD 1000–1200), and the last ~200 years. A shift from meso-eutrophic/benthic diatoms to oligotrophic/planktonic diatoms occurred during an interval of enhanced precipitation throughout the humid ‘Little Ice Age’ (AD 1600–1800). A return to markedly eutrophic conditions and a decreasing lake level occurred after the ‘Little Ice Age’, reflecting the more arid regional environment of the last 200 years. The high variability of the proxies suggests that both climate change and human activity were the major drivers of the ecological status of Bosten Lake during the late Holocene. We suggest that both the continuous increase of human activity and ongoing global warming will cause the major eutrophication or salinization of the freshwater lakes in the arid zone of northwest China.

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-(Diatoms (Bacillariophyceae) from superficial sediments of cascade reservoirs in the Paranapanema River (SP/ PR, Brazil): Coscinodiscophyceae and Fragilariophyceae). Floristic survey of Coscinodiscophyceae and Fragilariophyceae from superficial sediments of cascade reservoirs in the Paranapanema River is presented. Sediment samplings were gathered with dredge in three sampling stations of four reservoirs located in the upper Paranapanema River (Jurumirim and Chavantes reservoirs) and middle portion (Salto Grande and Capivara reservoirs), and in two sampling stations in the lower river (Rosana reservoir). Thirteen infrageneric taxa were identified, six of them belonging to class Coscinodiscophyceae and the other seven to Fragilariophyceae.

-(Biodiversity and distribution of diatoms (Bacillariophyceae) from surface sediments in the cascading reservoirs of Paranapanema river, São Paulo and Paraná States, Brazil). Paper presents the taxonomic survey and distribution of diatoms (class Bacillariophyceae) from the surface sediments of five cascading reservoirs of the Paranapanema river. Samples were dredged from three sampling stations (upstream, middle portion, and close to the dam) of reservoirs. 44 taxa belonging to 22 genera were identified, 23 (52.3%) of which represent new records for the Paranapanema river basin, four (9.1%) for the São Paulo State, and two (4.5%) for the Paraná State. Morphometric data, relevant comments, and local spatial distribution of species in the São Paulo and Paraná States are available. Taxonomic richness was markedly greater in the first reservoir (Jurumirim) and in the sampling station with influence of the Tibagi river. Present work is a pioneer contribution to the country in regard to biodiversity and spatial distribution of diatoms in cascade reservoirs, contributing for future studies on conservation and monitoring of the Paranapanema river basin. Key words: algae, cascade reservoirs, flora, sediment RESUMO -(Biodiversidade e distribuição das diatomáceas (Bacillariophyceae) de sedimentos superficiais nos reservatórios em cascata do rio Paranapanema, SP/PR, Brasil. O trabalho apresenta os resultados do inventário e da distribuição das diatomáceas da classe Bacillariophyceae de sedimentos superficiais de cinco reservatórios em cascata do rio Paranapanema. Amostras foram coletadas com draga em três locais (montante, região intermediária e lacustre) dos reservatórios. Foram identificados 44 táxons infragenéricos, sendo 23 (52,3%) novas citações para a bacia do rio Paranapanema, quatro (9,1%) para o Estado de São Paulo e duas (4,5%) para o Estado do Paraná. São disponibilizados dados morfométricos, comentários relevantes, distribuição espacial e local de ocorrência das espécies para os Estados de São Paulo e Paraná. A riqueza de espécie foi nitidamente mais elevada no primeiro reservatório da série (Jurumirim) e na estação com influência do rio Tibagi. Este trabalho traz contribuição pioneira para o país no que se refere à biodiversidade e distribuição espacial das diatomáceas em reservatórios em cascata, podendo subsidiar futuros estudos sobre conservação e monitoramento na bacia hidrográfica do rio Paranapanema. Palavras-chave: algas, flora, represas em cascata, sedimentos IntroduçãoOs sedimentos superficiais acumulam os eventos que ocorreram na bacia de drenagem ao longo de um passado recente, fornecendo uma amostra rica em informações sobre a biodiversidade, uma vez que integra diferentes hábitats (plâncton, perifíton, bentos) ao longo do tempo e inviável de ser obtida a partir de amostras vivas (Bennion 1995). Dessa forma, o estudo das diatomáceas acumuladas no sedimento contribui de forma mais abrangente para o conhecimento da biodiversidade dos ecossistemas aquáticos, podendo subsidiar estudos sobre co...

Arid Central Asia (ACA) is characterized by sparse freshwater resources and fragile ecosystems (Narisma et al., 2007). The acceleration of urbanization and the development of agriculture in the region have led to a sharp increase in freshwater consumption (Scanlon et al., 2007). The lakes of the region are important freshwater resources and have a major influence on both its social and ecological systems. However, during the past several decades, excessive utilization of water resources has led to the significant shrinking and salinization of many lakes in ACA, resulting in the degradation of lake ecosystems (Bai et al., 2011). Therefore, a comprehensive understanding of the mechanisms driving water-storage change of the lakes in the region is not only important for the protection and restoration of lake ecosystems, but also as a reference for formulating strategies of inland water resources management.

In arid central Asia, the geo-ecological environment of the well-vegetated high mountains differs from that of the extensive arid Gobi desert areas, with the forested areas having experienced a different pattern of humidity variations compared to the dryland regions. Therefore, the moisture history of the forest areas reconstructed by tree rings may differ from that of the dryland areas. In the extremely arid area of the western Qilian Mountains and the surrounding dryland areas, where forest is absent, it is unclear how humidity conditions have changed over the past several centuries. Here, we use a pollen record from Tian'E Lake, with a chronology based on 210 Pb and 137 Cs, and with an average temporal resolution of ∼2 years, to reconstruct the humidity changes over the past 300 years. The results show that the pollen assemblage is dominated by Artemisia and Amaranthaceae (Chenopodiaceae), and therefore, the A/C (Artemisia/ Chenopodiaceae) ratio can be used to reconstruct changes in humidity conditions.