Late Miocene—Early Pliocene paleotemperatures for California from marine diatom evidence

Paleotemperatures have been interpreted from the evidence of the diatom flora for an Upper Miocene section of marine diatomaceous sediment near Lompoc, California. The diatom flora has been compared with the distribution of modern diatoms in surface sediments of the North Pacific Ocean to propose a Miocene sea paleotemperature curve for this area of California. Temperatures declined sharply in the Late-Mohnian (Upper Miocene) to a winter minimum of about 10°C. Thereafter, a gradual and fluctuating rise in temperature characterized the latest Miocene (Delmontian); minimum seasonal temperatures approached 17°C by the Early Pliocene.This diatom assemblage paleotemperature curve is supported by other evidence. Independent studies of particular diatom temperature indicator species show the same trends, as do the paleotemperature indications of a fossil fish fauna and the foraminiferal fauna in the section. Furthermore, the curve shows a marked correspondence to paleotemperature curves based on planktonic foraminifers and on radiolarians for the Upper Miocene of southern California, providing an additional tool for paleotemperature reconstruction.     

The epipsammon; a relatively unknown freshwater algal association

A freshwater diatom flora has been shown to exist on sand grains. The species have been determined from samples of four bodies of water. This epipsammic flora is composed of minute diatoms, many of which require electron microscope study before their identification can be made certain. The chemistry of the water undoubtedly influences the association of species.     

Seasonality and distribution of epilithic diatoms,macroalgae and macrophytes in a spring-fed stream system in Ontario,Canada

A study of the epilithic diatom, macroalgal and macrophyte communities from a spring-fed stream in Ontario, Canada was undertaken from September 1996 to July 1997. The relative abundance of the epilithic diatom flora, percent cover of macroalgal and macrophyte taxa, and several physical and chemical stream conditions were monitored along a 20-m stretch at each of four sites, approximately every 2 months. Several stream conditions were relatively constant over the sampling period (pH, maximum width and maximum depth), while others exhibited a distinct seasonal pattern (water temperature, specific conductance and daylength) and some fluctuated strongly with no discernable seasonal pattern (turbidity, current velocity). A total of 124 taxa were identified from the four sites, including 79 epilithic diatoms, three macroalgal diatom species (large gelatinous masses), one cyanobacterium, two red algae, eight green algae, one chrysophyte alga, one tribophyte alga, three mosses, three horsetails and 23 angiosperm taxa. Species richness was positively correlated to stream channel maximum width and depth, indicating that the total number of species tends to increase in a downstream direction. Distribution of several diatom and macroalgal species was significantly correlated to stream conditions (e.g. Gomphonema parvulum and Phormidium subfuscum with current velocity); however, the vast majority of species did not display seasonal variation in abundance that could be explained by changes in stream conditions. Many of the taxa identified from Blue Springs Creek are common elsewhere in North America.     

Diatom communities in soils influenced by the wandering albatross (Diomedea exulans)

Soil diatom communities within two breeding colonies of the wandering albatross (Diomedea exulans) on Île de la Possession (Crozet Archipelago) were investigated. Samples were collected around occupied and abandoned nests and compared with control samples taken from soils lacking any animal influence. A total of 163 diatom taxa has been identified. Differences in the diatom flora were recorded between the two colonies, but the results show that it is almost impossible to identify a single diatom community typical for albatross-influenced areas. Diatom species composition varied markedly between control samples, occupied and abandoned nests. A turnover in the diatom community (shift from eutraphentic to oligotraphentic taxa) was observed when moving away from both occupied and abandoned nests, although no significant differences in diversity have been found. In summary, soil diatom species composition seems to indicate the impact of animal perturbations. However, it is too early to draw sound conclusions and further studies regarding the topic should be performed to confirm the results of the present study.     

The cryptogamic flora of an isolated rainforest fragment in Tasmania

The cryptogamic flora of a small isolated natural fragment of rainforest in south-eastern Tasmania has retained its rainforest character but has been modified in comparison to the flora of large, well-buffered rainforest stands. There is a high proportion of widespread wet forest species and many typical rainforest lichens and bryophytes are absent or represented only by depauperate and/or sterile individuals. The relative proportions of hepatics to mosses is reversed compared with that normally found in rainforest and there is a much lower diversity in the bryophyte flora. In spite of these modifications, the flora of the rainforest fragment is quite distinct from that of the surrounding sclerophyll vegetation. The community acts as a refuge for many species and contributes significantly to the overall biodiversity of the area. The site is very important for biological conservation but the data suggest that the ecosystem is extremely fragile and must be protected from future disturbance if its rainforest flora is to survive. The new combination, Bacidia vallatula (Jatta) Kantvilas, is proposed, and the lichen Byssoloma subdiscordans (Nyl.) P. James is recorded from Tasmania for the first time.     

Diatom Flora of the Grand River,Ontario, Canada

Summary This paper describes the diatom flora of the Grand River, Ontario, Canada. Samples were collected systematically from the river over a period of several years at tweleve stations. The diatom flora of the river is typical of temperate alkaline rivers. The flora is rich in species and variaties, and is similar to that from many parts from North Eastern United States. A total of 273 taxa of diatoms were identified. There is a tendency for the number of species per sample to increase downstream. The flora of the estuary in characteristic with a great variety of taxa occuring in small numbers. Most of the species are alkaliphilous and indifferent in the halolian spectra. Part of Ph. D. thesis (1970) of senior author     

Spatial and temporal variations in moss-inhabiting summer diatom communities from Potter Peninsula (King George Island, Antarctica)

This work represents the first analysis of the spatial and temporal variations in the diversity and community structure of diatoms associated with mosses, either dry or wet, sampled during the summer season from the littoral zone of three ponds in Potter Peninsula (King George Island, South Shetland Islands). It also seeks to explore the effect moisture content in the mosses can have on the structure of the diatom assemblages. The ponds approximately had the same number of species, and differences were found between the dry and wet sampling points. The same 4 species were predominant in the three ponds (Nitzschia alpina, N. perminuta, Staurosira oldenburgiana, and Pinnularia subantarctica var. elongata), but not in the same proportions. The first three species differed from those which were found to be dominant in other basins covered by mosses in southern South America and in the sub-Antarctic region. The latter, P. subantarctica var. elongata, had only been found to be abundant in a moss sample from another South Shetland Island. The diatom assemblages were found to be more strongly related to habitat traits (e.g. distance to the sea, ponds’ areas, and the vegetation’s moisture levels) than to the physical–chemical variables measured in the water.     

Diatom communities from the sub-Antarctic Prince Edward Islands: diversity and distribution patterns

During an extensive survey of the freshwater and moss-inhabiting diatoms of the Prince Edward Islands, a total of 214 taxa belonging to 60 genera were found. Three main communities can be found on the two islands. A large part of the samples was grouped into an aquatic group, bringing together all samples from lentic and lotic waterbodies. A second, contrasting, group was formed by all dry samples whereas in a third group all habitats with higher mineral contents were found. The habitats differed clearly in taxa composition reflecting that way possible environmental differences. Although the diatom composition between the two islands of this island group (Marion and Prince Edward Island) showed some minor qualitative differences, no marked quantitative differences have been observed. The diatom flora shows a distinct similarity with the other islands in the southern Indian Ocean, such as the Crozet archipelago and the Kerguelen Islands forming a biogeographical entity in this part of the ocean, distinctly separated from the non-marine diatom flora in other parts of the (sub-)Antarctic Region.     

The diatom flora of Lake Eyre South: a large episodically filled salt lake in South Australia

Thirty-three diatom taxa were collected from the large terminal salt lake, Lake Eyre South, located in south-central Australia. The diatom assemblage included taxa that were widely distributed in marine and saline athalassic habitats in both northern and southern hemispheres, with the diatom flora of Lake Eyre South most similar to that of southern Africa. This study represents the first report on the diatom flora of Lake Eyre South and supports the findings that episodically filled lakes do not appear to be good evolutionary loci.     

Diatoms from surface sediments of Amurskiy Bay,Sea of Japan

The results of a study of diatoms from surface sediments (0–1 cm) of Amurskiy Bay are presented for the first time. The specific composition (221 species and intraspecific taxa) and ecological structure of the diatom flora were determined. The diatom species composition of phytoplankton, periphyton, and surface sediments is compared.     

Lithophytic algae: A major threat to the karst formation of show caves

Depending on the intensity, quality and duration ofthe illumination, necessary for viewing show caves,conditions conducive for algal growth are created. Although algae are the major component of this flora,ferns and mosses have also been recorded. Little isknown of the algae, except that they are considered anuisance in terms of discoloration and damage to thekarst formations. The occurrence and possible controlof the algal flora has been studied in the CangoCaves, one of the most important touristic sites inSouth Africa. The algal flora is sparse in speciesdiversity and primitive forms are present. They haveparticular physiological adaptations and usingmicro-oxygen liberation and fluorescence measurements,their photosynthetic characteristics were established. Environmentally friendly control measures wereinvestigated and a solution for their control is proposed.     

DIATOM ASSOCIATIONS IN YAQUINA ESTUARY,OREGON: A MULTIVARIATE ANALYSIS1

A cluster analysis and a principal components analysis were performed to examine the degree to which the diatom flora of Yaquina estuary can be partitioned into discrete associations and to relate the composition of the flora to selected physical properties of the estuary. The species composition of the diatom flora during the winter was more closely associated with salinity and intertidal exposure them in the summer. A cluster of freshwater taxa obtained for the winter data was the most conspicuous diatom association defined by the cluster analysis. Although taxa within a cluster had more similar distributions than taxa from different clusters, there was considerable variation in the distributions of marine and brackish water taxa within a multispecies cluster.     

Diatoms in sediment cores in Utah Lake,Utah, U.S.A.

Diatoms from sediment cores taken from Provo Bay, Geneva and midlake sites in Utah Lake, Utah County, Utah were studied. Algal communities from strata at four centimeterintervals of the cores were analyzed. This study has demonstrated that the diatom flora in Utah Lake has changed through time and that the diatom communities of Provo Bay are floristically unique from those of the main body of the lake.     

The diatoms ingested by freshwater snails: temporal,spatial, and interspecific variation

Seventeen species of diatoms, representing a broad range of sizes, shapes, and growth habits, were collected from rocks in rapidly-flowing sections of the Mitchell River, North Carolina. The diatoms ingested by adult Goniobasis proxima, juvenile Leptoxis carinata, and adult Physa sp. co-occurring in this habitat were indistinguishable from one another, in spite of great differences in radular morphology. All snails sampled the diatom flora almost randomly, with only one or two of the larger diatom species under-represented in the gut contents. Some snails also seemed to selectively ingest the smaller individuals of the larger diatom taxa, and larger individuals of the smaller diatom taxa. The diatoms identifiable in juvenile Goniobasis guts were somewhat more distinctive, although this seemed to be due at least partly to more mechanical breakage. The diatom flora of quiet, muddy pools was much different from that of shallow, rocky areas, but once again, Goniobasis seemed to sample the available flora randomly. Seasonal variation was also apparent in the diatom diet of Goniobasis. We suggest that in some cases, it may be reasonable to use snails to sample the diatom assemblage present in a particular habitat, if more direct methods are impractical.     

EFFECTS OF CHIRONOMID (INSECTA: DIPTERA) TUBE-BUILDING ACTIVITIES ON STREAM DIATOM COMMUNITIES1,2

Chironomid retreats, constructed out of sand grains upon submerged wood debris, increase the surface area available for diatom colonization. The three dimensional substratum afforded by chironomid tubes supports up to twelve times the diatom biavolume found upon adjacent, unmodified substratum in a northern Michigan stream. Diatom enumeration within scrapings from small defined areas on artificial substrata, combined with examination of intact natural substrata through scanning electron microscopy (SEM), reveals distinct, microdistribution patterns. The larval retreats of two major taxa of tube-dwelling chironomid's (Micropsectra sp. and Pseudodiamesa cf. pertinax Garrett) display significantly different diatom communities relative to adjacent masonite substratum. Substratum without chironomid tubes is primarily colonized by Achnanthes minutissima Kütz. and Cocconeis placentula Ehr., exhibiting the lowest species diversity of microhabitats examined. The diatom flora upon sand tubes of Micropsectra sp. is dominated by Opephora martyi Herib., as is the flora of sand grains collected from the stream sediment load. These two micro-habitats exhibit a high community similarity (SIMI). The SIMI index also suggests that the flora of P. pertinax tubes is highly similar to that of sand grains. Diversity, however, is almost three times greater on P. pertinax tubes and SEM observations reveal that this microhabitat is characterized by a more spatially complex flora; Nitzschia and Navicula spp. dominate the upperstory, and O. martyi is located on underlying sand grains. Results indicate that tube-building chironomids in Carp Creek affect diatom microdistribution by: (1) stabilizing sand grains and associated flora within their retreats, (2) providing a ‘refugium’ for upperstory diatom taxa from the mayfly grazer, Baetis vagans McDunnough (Insecta: Ephemeroptera), and (3) through local nutrient enrichment.     

Diatoms in river water-monitoring studies

Diatoms grow abundantly in rivers, colonising almost all suitable habitats. They have been used extensively in studies related to the monitoring of water quality. This review attempts to draw together data from a wide variety of approaches. The advantage of sampling discrete habitats is stressed and particular attention is paid to the diatom flora of stone surfaces (epilithon) which is the favoured source in many studies. The advantages and drawbacks of the techniques are discussed and some hopefully helpful suggestions made. The historical development of the topic is briefly surveyed, but no attempt has been made to present a comprohensive review of the literature which has increased enormously in the last few decades.     

The eutrophication history of Lake Särkinen,Finland and the effects of lake aeration

Lake Särkinen is a small lake in the parish of Sotkamo, Finland. The lake has been strongly enriched since the middle of the 1960's. The nutrient load was greatly reduced in 1969 and aeration was started in 1980.According to ²¹⁰Pb dating sediment accumulation rates are lowest (ca 9 mg cm^–2 yr^–1) between about 1920 and 1960. Thereafter they rise to the present level (22 mg cm^–2 yr^–1).The diatom flora indicates rising eutrophy from the beginning of the 20th century and again in the 1950–60's period. The surface sample, which represents the 1980's, shows a change in diatom flora indicating lake recovery. Changes in nutrient concentrations and in the solubility of phosphorus in the sediments indicate signs of oxygen depletion.     

Deep-water occurrence of the moss Bryum pseudotriquetrum in Radok Lake, Amery Oasis, East Antarctica

Mosses form an important component of the flora in terrestrial and lacustrine ecosystems of Antarctica. Here we report the occurrence of mosses in Radok Lake, Amery Oasis, East Antarctica, which has a maximum water depth of c. 360 m and is presumed to be the deepest freshwater lake in Antarctica. Aquatic mosses, determined as Bryum pseudotriquetrum, were found at water depths of up to 81 m, growing on the sediment surface at different locations in the lake basin. This is the deepest record of living mosses in Antarctic lakes. The modern oligo- to ultra-oligotrophic hydrological characteristics of Radok Lake may be an indispensable precondition for the growth of the moss at these water depths.     

The species composition and distribution of diatom algae in sphagnum bogs in European Russia: The Polistovo-Lovatskii land tract

The species composition of diatom algae in the Polistovo-Lovatskii sphagnum tract (Rdeiskoye bog, Novgorod oblast) \are studied. The systematic and ecological-geographical analyses of the flora are performed. A total of 256 species and intraspecific taxa differing in ecological specificities and frequencies of occurrence in samples are revealed. A considerable number of centric diatoms is found. It is shown that primary and secondary diatom communities are formed in large sphagnum tracts. The horizontal heterogeneity of diatom communities in sphagnum bog is revealed. The species diversities of diatom algae in different bogs are compared.