Diatom Communities In Lakes Research Articles

On the biodiversity of diatom communities in lakes of East China: Geochemical effects dominated after eutrophication

AbstractAimOver the last century, lakes all over the world have experienced significant eutrophication and become more susceptible to critical transitions. This has prompted a growing need to understand how community dynamics shift following ecological perturbations. This study aims to elucidate the present status, spatial patterns and determinants of biological diversity, and how they have changed in response to alterations driven by eutrophication.LocationLakes of East China, mostly in the Yangtze River Basin.TaxaBacillariophyceae (163 species in 33 genres, see taxa names in Appendix S1).MethodsThe environmental conditions of over 60 lakes were assessed based on parameters such as water quality, physical characteristics and biogeochemical constituents. Surface sediment samples and high‐resolution sediment records were collected to quantify the biodiversity of diatom communities, and principal component analysis (PCA) was used to determine the major environmental gradients. Meanwhile, linear regression, canonical correlation analysis and Mantel tests were used to quantify the correlations between variables.ResultsBiodiversity metrics showed no distinct geographic patterns, although areas near large lakes showed comparatively high evenness. Smaller pairwise dissimilarities were observed among hypereutrophic lakes in comparison to lakes with a lower trophic status. The past century has witnessed a decrease in both pairwise dissimilarity and the standard deviation of evenness. A significant statistical association was found between dissimilarity and ionic concentration and composition in the surface sediment of lakes, rather than nutrient levels.Main ConclusionsFollowing regional eutrophication and human disturbance, a significant reduction in biodiversity differentiation was observed in lakes located in East China. Currently, the dominant factor in determining the beta diversity of diatom communities is geochemical conditions rather than nutrient concentrations. Long‐term stress caused by cultural eutrophication may also have altered the dominant determinant of regional biodiversity and diatom community dynamics.

РЕАКЦИЯ ДИАТОМОВЫХ ВОДОРОСЛЕЙ ОЗЕРА ГРЯЗЕВОЕ (МАГАДАНСКАЯ ОБЛАСТЬ) НА ИЗМЕНЕНИЯ ОКРУЖАЮЩЕЙ СРЕДЫ СЕВЕРНОГО ПРИОХОТЬЯ В ПОЗДНЕМ ПЛЕЙСТОЦЕНЕ-ГОЛОЦЕНЕ

The study of diatoms from the sediments of well Gz-1 (Gryazevoe Lake, Magadan Region) allowed us to identify the response of diatom communities to environmental changes in the Late Pleistocene and Holocene and establish the main stages of the transformation of the lake ecosystem. Three diatom zones and four subzones were identified based on changes in the concentration of diatom floras in sediments, the ratio of representatives of ecological groups and dominants, reflecting the evolution trend of the lake diatom flora during the transition period from the last glacial maximum to the Holocene. This trend is similar to the changes in the lake diatom communities of the Arctic regions noted for the last millennium in terms of the change of taxonomic composition and dominants. The data of diatom studies, lithological and petrophysical characteristics of sediments indicate that the most significant changes in the natural environment occurred at the Pleistocene-Holocene boundary from 12.6 to 11.1 thousand years ago.

Diatom Response to Global Warming in Douhu Lake, Southeast China

AbstractA large number of lacustrine sedimentary records indicate that global warming is the main factor leading to significant changes in diatom communities in lakes of the northern hemisphere. However, due to the intensification of human activities since 1850, some scholars have emphasized that the increasing lake trophic level may be the main reason for the changes in diatom communities. The debate is ongoing. In order to avoid falling into the complex relationship between diatom changes and the seasonal cycle that characterizes lakes in mid and high latitudes, we chose a lake located at a low latitude, where the relationship between diatoms and temperature is not indirect but direct. The diatom record spans the past ca. 100 years and reveals that the abundance of Aulacoseira granulata increased from 1900 until 1985, replacing the previously dominant Aulacoseira ambigua. These changes are in agreement with the increasing trend in global temperature. Since 1985, the percentages of the small‐celled Discostella stelligera and the benthic diatom Navicula heimansioides have increased, while Aulacoseira granulata has decreased. This latest shift is caused by further global warming. We conclude that warming is the main factor leading to changing diatom communities in Douhu Lake.

Ecological uniqueness of stream and lake diatom communities shows different macroecological patterns

AbstractAimTo discover whether lake and stream diatom communities show different patterns in species richness and in their local (LCBD) and species (SCBD) contributions to beta diversity in relation to macroscale environmental characteristics.LocationFinland.MethodsAs biological data, we used diatom samples collected from Finnish stream (n = 492) and lake (n = 290) sites. As explanatory variable data, we used information on macroscale environmental and historical aspects, such as bedrock, soil and post‐glacial highest shoreline. We also accounted for catchment areas, different levels of isolation and relative centrality of the study sites. We ran multiple linear models and selected best models based on AICc values.ResultsWe found that macroscale factors affecting diatom richness and ecological uniqueness differed clearly between streams and lakes. LCBD and species richness of stream communities were more affected by regional environmental characteristics, whereas LCBD and species richness of lake communities were more often driven by spatial measures. The measures of LCBD and species richness showed a slightly negative relationship in streams, but no such relationship was detected in lakes. Also, we showed that, for both streams and lakes, SCBD was strongly determined by the number of sites occupied by a species and the overall abundance of a species.Main conclusionsOur findings related to the distinction between the determinants of lake and stream species richness or LCBD may be tied to the different hydrological connectivity levels occurring in freshwater lotic and lentic systems. Also, in streams, sites with exceptional ecological uniqueness seem to have a rather low number of species. Our findings may be applied to biological conservation and monitoring planning, emphasizing that not only species‐rich but also unique low‐richness sites may be valuable conservation goals.

Nitrogen subsidies in glacial meltwaters have altered planktonic diatom communities in lakes of the US Rocky Mountains for at least a century

We examined sedimentary diatom profiles from alpine lakes in the US Rocky Mountains to assess when glacially fed lakes started receiving nitrogen subsidies and whether that timing varies across regions. We focused on lake sediment cores from Glacier National Park and compared them to previously published work from the Greater Yellowstone Ecosystem. The only contemporary feature of these glacially fed lakes that differs from snowmelt-fed lakes is nitrate concentration, with glacially fed lakes having about 40 times higher nitrogen than snow-fed lakes; lake thermal structure and temperatures do not differ between lake types. Increases in Asterionella formosa, a strong indicator of nitrogen enrichment, occurred much earlier in glacially fed compared to snow-fed lakes across both regions. Responses to nitrogen enrichment in glacially fed lakes started at least a century ago, and in some cases, many centuries ago, whereas they occurred after 1970 in the snow-fed lakes. Furthermore, diatom assemblages in glacially fed lakes showed declines in species richness over time and greater community turnover compared to snow-fed lakes. Multiple lines of evidence indicate that throughout the late Holocene glacially fed lakes in both regions of the Rocky Mountains have followed different ecological trajectories than snow-fed lakes as a result of increasing nitrogen concentrations.

Nitrogen Deposition Effects on Diatom Communities in Lakes from Three National Parks in Washington State.

The goal of this study was to document if lakes in National Parks in Washington have exceeded critical levels of nitrogen (N) deposition, as observed in other Western States. We measured atmospheric N deposition, lake water quality, and sediment diatoms at our study lakes. Water chemistry showed that our study lakes were ultra-oligotrophic with ammonia and nitrate concentrations often at or below detection limits with low specific conductance (<100 μS/cm), and acid neutralizing capacities (<400 μeq/L). Rates of summer bulk inorganic N deposition at all our sites ranged from 0.6 to 2.4 kg N ha−1 year−1 and were variable both within and across the parks. Diatom assemblages in a single sediment core from Hoh Lake (Olympic National Park) displayed a shift to increased relative abundances of Asterionella formosa and Fragilaria tenera beginning in the 1969–1975 timeframe, whereas these species were not found at the remaining (nine) sites. These diatom species are known to be indicative of N enrichment and were used to determine an empirical critical load of N deposition, or threshold level, where changes in diatom communities were observed at Hoh Lake. However, N deposition at the remaining nine lakes does not seem to exceed a critical load at this time. At Milk Lake, also in Olympic National Park, there was some evidence that climate change might be altering diatom communities, but more research is needed to confirm this. We used modeled precipitation for Hoh Lake and annual inorganic N concentrations from a nearby National Atmospheric Deposition Program station, to calculate elevation-corrected N deposition for 1980–2009 at Hoh Lake. An exponential fit to this data was hindcasted to the 1969–1975 time period, and we estimate a critical load of 1.0 to 1.2 kg N ha−1 year−1 for wet deposition for this lake.

The structure and species composition of the diatom communities in tropical volcanic lakes of eastern Mexico

Six nutrient-rich tropical volcanic lakes in eastern Mexico were investigated to document their characteristic diatom floras. Plankton and sedimentary diatom communities were compared to verify the representativity of the sediment assemblage by identifying the plankton species present in the sediment. Relationships between surface sediment diatom communities and 20 physico-chemical variables were evaluated using multivariate analysis. High phosphorus concentrations were measured in all the lakes sampled and chlorophyll a concentrations were found to be useful in describing lake trophic status which ranged from meso- to hypereutrophic. The results showed that the species composition and distribution of the diatom community in these lakes was most influenced by nutrient availability (P) and ionic composition. Canonical correspondence analysis showed that cation dominance explained a significant amount of the variation in the diatom community composition. It allowed the identification of three lake types: (1) Na+-dominated lakes where diatom communities had>50% Achnanthidium minutissimum (Grunow) Czarnecki; (2) Mg2+-dominated lakes, where the characteristic species were A. minutissimum (<30%) and Cymbella microcephala Grunow (<50%); and (3) one Ca2+-dominated lake, where Navicula arvensis Hustedt and Discostella pseudostelligera (Hustedt) Houk & Klee were the most abundant diatoms (>20%). The results suggest that some epiphytic diatoms (e.g., A. minutissimum, C. microcephala) can use other plankton algae as substrate; this is a strategy that allows them to remain within the euphotic zone in deep, eutrophic, turbid lakes. The lakes with the lowest nutrient levels had the best preserved terrestrial vegetation cover on the crater walls. This suggests that deforestation has been a factor that has accelerated the process of lake eutrophication during recent decades in this region.

Comparing pre-industrial and post-limed diatom communities in Swedish lakes, with implications for defining realistic management targets

In the 1960s and 1970s, acidification was identified as a major environmental problem in Scandinavia, Great Britain and North America. In Sweden, a liming program was launched in order to counteract the effects of acidification on surface waters. More than 30 years after large-scale liming began, there is still debate about whether liming actually achieves its goals, i.e., to prevent acidification in acid-sensitive surface waters and to restore natural conditions in acidified waters. We used Detrended Correspondence Analysis (DCA) and analogue matching of diatom assemblages in surface sediment samples (recent conditions) from 31 limed lakes and pre-industrial samples from 291 reference lakes to help answer the question as to whether the Swedish liming program achieves its goals. Diatoms are important primary producers in lakes and established indicator organisms for lake-water quality. First we compared pre-industrial with post-limed diatom communities to address the question whether liming causes unnatural conditions, i.e., diatom communities that have not previously occurred in Swedish lakes. Second, we addressed the issue of what is a realistic condition to use as a reference (natural condition) or a target in management programs. We found that the diatom communities in limed lakes were not different from the communities in the reference lakes. Most of the limed lakes had one or more analogues within the reference data set and many of them had at least one within-lake analogue. Hence, liming does not create unique diatom communities in lakes. Based on this and previous paleolimnological studies in Swedish lakes we suggest a conceptual model integrating the natural lake condition, the historical human impact, and the recent and contemporary human impact, when defining realistic targets in management programs.

Freshwater diatoms on sub-Antarctic Macquarie Island: an ecological survey of 14 lakes

A survey of the diatom (Bacillariophyceae) populations in 14 lakes and ponds on sub-Antarctic Macquarie Island identified 102 species hom 34 genera, including species considered endemic to the sub-Antarctic region. Multivariate analysis of the diatom communities divided the lakes into two broad groups; oligotrophic plateau lakes dominated by species including Bmchysira exilis, Fragilaria capucina var. gracilis, Psammothidium abundans, Ps. confosum and Ps. confusum var. atomoides, and lowland peat-based lakes dominated by species including Fragilaria pulchella, Planothidium lanceolatum and Pl. quadripunctatum. Factors relating to lake elevation rather than water pH or conductivity appeared to have most influence on the lake diatom communities.

Climate‐lake interactions recorded in varved sediments from a Swedish boreal forest lake

AbstractA 1100‐year long record of lake ecosystem response to climate and catchment change with precise chronological control is reported. Diatom and pollen assemblages of an annually laminated (varved) sediment from a northern Swedish lake (Kassjön, Våsterbotten) were used as records of lake diatom communities and catchment vegetation. These data were compared with summer temperature estimates based on tree‐ring records of the same geographical area to identify the effects of climate change and catchment disturbance on diatom assemblages in the lake. In a canonical ordination, 23% of the variability in the total diatom assemblages for the period AD1040–1804 was accounted for by changes in pollen data which reflect agricultural development in the catchment. Diatom species richness, however, exhibited a stronger relationship with summer temperature and, significantly, declined with the lower temperatures associated with the Little Ice Age minimum (early 17th century). Summer temperature accounted for 23% of the variability in diatom species richness 20 years later. The mechanism behind this time‐lag is unclear, but may be related to catchment‐mediated effects, given recent evidence for lags in the response of boreal‐forest vegetation regeneration cycles to climatic variability. These results suggest that climate‐related effects on lakes occurring over medium timescales can be resolved in lake sediments. Moreover, it is possible to identify these effects despite cultural‐related signals, but as the latter become more extreme in the late 20th century the climate signal is obscured.

Late Cenozoic lacustrine and climatic environments at Tule Lake, northern Great Basin, USA

Cores of lake sediment to a depth of 334 m in the town of Tulelake, Siskiyou County, northern California, document the late Cenozoic paleolimnologic and paleoclimatic history of the northwestern edge of the Great Basin. The cores have been dated by radiometric, tephrochronologic and paleomagnetic analyses. Lacustrine diatoms are abundant throughout the record and document a nearly continuous paleolimnologic history of the Tule Lake basin for the last 3 Myr. During most of this time, this basin (Tule Lake) was a relatively deep, extensive lake. Except for a drier (and cooler?) interval recorded by Fragilaria species about 2.4 Ma, the Pliocene is characterized by a dominance of planktonic Aulacoseira solida implying a warm monomictic lake under a climatic regime of low seasonality. Much of the Pleistocene is dominated by Stephanodiscus and Fragilaria species suggesting a cooler, often drier, and highly variable climate. Benthic diatoms typical of alkaline-enriched saline waters commonly appear after 1.0 Ma, and tephrochronology indicates slow deposition and possible hiatuses between about 0.6 and 0.2 Ma. The chronology of even-numbered oxygen isotope stages approximately matches fluctuations in the abundance of Fragilaria since 800 ka indicating that glacial periods were expressed as drier environments at Tule Lake. Glacial and interglacial environments since 150 ka were distinct from, and more variable than, those occurring earlier. The last full glacial period was very dry, but shortly thereafter Tule Lake became a deep, cool lacustrine system indicating a substantial increase in precipitation. Aulacoseira ambigua characterized the latest glacial and Holocene record of Tule Lake. Its distribution indicates that warmer and wetter climates began about 15 ka in this part of the Great Basin. Diatom concentration fluctuates at 41 000 year intervals between 3.0 and 2.5 Ma and at approximately 100 000 year intervals after 1.0 Ma. In the late Pliocene and early Pleistocene, Aulacoseira solida percentages wax and wane in an approximately 400 000 year cycle. The possible response of Tule Lake diatom communities to orbitally-induced insolation cycles underscores the importance of this record for the study of late Cenozoic paleoclimate change.

The effect of land use on the diatom communities in lakes

The effect of land use on the diatom communities in lakes