The survival of <Emphasis Type="Italic">Sicyopterus stimpsoni</Emphasis>, an endemic amphidromous Hawaiian gobiid fish,relies on the hydrological cycles of streams: evidence from changes in algal composition of diet through growth stages fish

Gut contents of larval, juvenile, and adult specimens of the Hawaiian gobiid fish Sicyopterus stimpsoni were examined to catalog the algal flora ingested by this species. The developmental stages of S. stimpsoni examined represented hallmark points in the fish’s life cycle corresponding with major migratory and metamorphic transitions. The algal flora was dominated by diatom species and shifted from taxa representative of a marine, planktonic community in larval fish to a freshwater, benthic community in juvenile and adult fish. This change in diet corresponds with the migration of larval fish to freshwater streams just prior to juvenile development in which rapid modification in mouth anatomy makes ingestion of planktonic algal species difficult. Benthic diatoms from juvenile and adult fish assemblages represented multiple genera that live in a narrow set of environmental conditions. These algae grow during a specific period in the development of the benthic algal community in Hawaiian streams. This suggests a highly specialized dietary behavior that depends heavily on continually restarting the benthic algal successional pattern, which appears to be regulated by the hydrological cycles of streams on the island.     

Edaphic diatom communities associated with Spartina alterniflora and S. patens in New Jersey

Edaphic diatoms inhabiting the sediments beneath dwarf Spartina alterniflora Loisel. and S. patens (Ait.) Muhl. in Great Bay salt marsh, Tuckerton, New Jersey were collected from 24 September 1974 through 20 August 1975. Of the 91 taxa encountered, 8 were endemic to the dwarf S. alterniflora habitat and 42 endemic to the S. patens habitat. The edaphic diatom community associated with S. patens was comprised of a much greater number of taxa and possessed higher values for species diversity (H') and evenness (J') than the community associated with dwarf S. alterniflora. The salinity of the marsh surface showed a completely opposite trend, being greatly reduced at the S. patens habitat. A highly significant relationship (P < 0.001) between the number of diatom taxa and marsh surface salinity at the S. patens habitat was demonstrated by a least squares regression. This finding led to the conclusion that the dissimilarity in the structure of the two edaphic diatom communities was primarily due to the very low marsh surface salinities at the S. patens habitat from January through June, and that this sustained. low-salinity regime allowed a very large number of taxa to coexist only in the S. patens community. Comparison of the diatom flora of Great Bay salt marsh with that of a Delaware marsh studied previously by the author showed that 67.0% of the 91 taxa encountered in New Jersey also occur on the Delaware marsh.     

DIATOM COMMUNITY STRUCTURE: TAXONOMIC AND STATISTICAL ANALYSES OF A MISSISSIPPI SALT MARSH1

Edaphic diatoms were collected on a seasonal basis from beneath five monospecific stands of spermatophytes on Graveline Bay Marsh (Mississippi) from 14 October 1976 through 21 June 1977. Of the 119 diatom taxa encountered. only seven were restricted to a single edaphic habitat, and five of these accounted for 17.2%of the individuals comprising the community associated with Distichlis spicata (L.) Greene. The single most abundant diatom was Navicula tripunctata (Müll.) Bory, which accounted for 21.5%of all individuals counted during the study. Based on a 2-way ANOVA of species diversity (H’) and the number of taxa in a sample, edaphic diatom community diversity was highest beneath D. spicata and Spartina patens (Ait.) Muhl., lowest beneath Sp. alterniflora Loisel. and Juncus roemerianus Scheele, and somewhat intermediate for the Scirpus olneyi Gray habitat. Structural differences between selected community pairs were quantified using a similarity index (SIMI) and the values generated were exceedingly variable. A multiple regression analysis revealed that structural differences amongst edaphic diatom communities were related to differences in elevation, far red light energy, ammonia nitrogen, soil moisture, and tentatively, height of the spermatophyte canopy.     

Feeding effects of the keystone deposit feeder Ilyanassa obsoleta (Neogastropoda,Gastropoda) on sedimentary diatoms

Microphytobenthos (MPB), typically comprised mainly of diatoms, is a key contributor to nearshore energy flow and nutrient cycles. Deposit-feeding invertebrates are known to alter the structure and activity of MPB. The eastern mud snail Ilyanassa obsoleta can reach extremely high densities in estuaries of the northwestern Atlantic, and their deposit-feeding and locomotion strongly influence other invertebrates and microbes. Our objective was to explore quantitative and qualitative effects of this keystone deposit-feeder on diatoms of intertidal sediments. We gathered snails from mudflat and sandflat habitats and collected their fresh fecal pellets in the laboratory. DNA metabarcoding allowed us to characterize diatom assemblages of ingested sediments and feces. We noted selective feeding such that reduction in MPB biomass with gut passage was difficult to quantify. Diatom α-diversity was reduced with gut passage in snails from both sedimentary regimes. Mudflat and sandflat diatom assemblages were distinct and differed markedly between feces and sediment in mud-feeding snails, whereas the difference in sand-feeding snails was minor. The sandy habitat was dominated by a mix of epipelic and epipsammic diatoms. In contrast, mudflat samples were dominated by epipelic and planktonic diatoms. Compositional differences between sediment and feces reflected preferential removal of planktonic taxa. Our results suggest the importance of phytodetritus to the mud snail diet, particularly in hydrodynamically quiescent environments. Due to the natural spatial patchiness of the snails and the capacity for rapid microbial recolonization, field experiments are recommended to determine whether MPB community changes attributed to gut passage are manifested at the landscape scale.     

Attached diatom communities from the lower Truckee River,summer and fall, 1986

The algal flora of the Truckee River below Reno, Washoe County, Nevada was examined during the summer and fall months of 1986. This reach of the lower Truckee River exhibited a substantial gradient in dissolved inorganic nitrogen associated with sources which included treated wastewater from the Reno metropolitan area. The algal communities were similar to those of other river systems of the Great Basin. Cyanophyta and Chlorophyta formed encrusting mats on the substrate, with the nitrogen fixer Calothrix atricha relatively abundant upstream from the nitrogen source. Diatoms were abundant within and upon this mat. A total of 139 diatom taxa and 11 taxa other than diatoms was identified from this flora. Several of the diatom taxa, including Achnanthes minutissima, Diatoma vulgare, Nitzschia dissipata, and Nitzschia palea, demonstrated distinct downriver patterns in relative abundance.     

Winter phytoplankton communities of Utah Lake,Utah, USA

Phytoplankton samples were collected from ice-covered Utah Lake during February and March, 1979 in order to characterize the winter algal flora. These samples were analyzed for presence and abundance of diatoms and non-diatom algae as well as selected water chemical parameters. A total of 159 diatom taxa and 20 non-diatoms was found in the water column under the ice. The flagellates Carteria stellifera, Euglena gracilis and Chlamydomonas globosa dominated the winter non-diatom flora while Stephanodiscus cf. dubius, Cyclotella meneghiniana, Navicula minima, Fragilaria construens var. venter, and Melosira granulata var. angustissima dominated the winter diatom flora. Species richness and abundance were elevated in the major bays of the lake.     

Relationships Between Environmental Variables and Benthic Diatom Assemblages in California Central Valley Streams (USA)

This study examines distributional patterns of benthic diatom assemblages in relation to environmental characteristics in streams and rivers in the California Central Valley ecoregion. Benthic diatoms, water quality, and physical habitat conditions were characterized from 53 randomly selected sites. The stream sites were characterized by low mid-channel canopy cover and high channel substrate embeddedness. The waters at these sites were enriched with minerals and turbidity varied from 1.3 to 185.0 NTU with an average of 13.5 NTU. A total of 249 diatom taxa were identified. Average taxa richness was 41 with a range of 7–76. The assemblages were dominated by Staurosira construens (11%), Epithemia sorex (8%), Cocconeis placentula (7%), and Nitzschia amphibia (6%). Multivariate analyses (cluster analysis, classification tree analysis, and canonical correspondence analysis) all showed that benthic diatom assemblages were mainly affected by channel morphology, in-stream habitat, and riparian conditions. The 1st CCA axis negatively correlated with mean wetted channel width (r = −0.66) and thalweg depth (r = −0.65) (Table 4). The 2nd axis correlated with % coarse substrates (r=0.60). Our results suggest that benthic diatoms can be used for assessing physical habitat alterations in streams.     

Effects of water quality and season on diatom community structure in the Damour River,Lebanon

The diatom flora in the lower Damour River, a small coastal river in Lebanon, was studied during 1981. The study area included the Damour estuary and a tributary, the el-Hamam River. Achnanthes minutissima was the most abundant diatom in the flora. Other dominant taxa included Nitzschia dissipata and Navicula cryptocephala var. veneta in the spring and Anomoeoneis vitrea in the fall. The diatom community structure was characterized by 1 or 2 dominant taxa, a few common and many rare taxa, but the taxa in these categories varied according to season and locality. The freshwater flora had a group of 20 taxa which were widely distributed in the study area throughout the study period. These taxa, in addition to a few taxa of more restricted seasonal occurrence, were the major contributers to the flora and are characteristic of this river system. Certain aspects of the flora were resistant to change. Others were more sensitive to environmental conditions. The estuarine flora reflected brackish conditions beginning in June and extending through October.     

Diatoms from surface sediments of the northern part of Lake Tanganyika

227 Diatom taxa were observed in the surface sediments of the northern part of Lake Tanganyika, including 1 new to science: Amphora tanganyikae. The diatom community of these sediments is mainly composed of benthic organisms while planktonic diatoms are rather rare. Many brackish-water and a few marine organisms were observed. Cosmopolitan organisms (77.1%) dominate the diatom flora but tropical, tropical African and African taxa are also well represented (22.9%)Deceased.Deceased.     

黑龙江省七星河湿地硅藻植物的初步研究

报道了2004年对黑龙江省七星河湿地国家级自然保护区的硅藻门植物研究的结果,共发现155个分类单位,包括113种39变种3变型,分别隶属于2纲6目9科26属,其中中国新记录2种2变种1变型共计5个分类单位,初步分析了七星河湿地硅藻植物群落的种类组成及生态类型,大部分的硅藻属于普生种类,同时出现了一些喜酸种类如：Eunotia pectinalis var. ventralis(Ehr.)Hust., Tabellaria flocculosa(Roth) Kütz.,Gomphonema augur Ehr.,Navicula subtilissima Cl.等,还有少量的嗜碱性种类出现。     

DISTRIBUTION OF INTERTIDAL DIATOMS ASSOCIATED WITH SEDIMENTS IN YAQUINA ESTUARY,OREGON1,2

Sediment samples and environmental data were collected from November 1973 to August 1974 to analyze the distribution of sediment-associated diatom assemblages relative to vertical, horizontal, and seasonal gradients in Yaquina Estuary, Oregon. The distribution of diatoms was regulated primarily by mean salinity and characteristics of the sediment, i.e., mean sediment size and percentage of organic carbon. Prominent taxa in the river above Yaquina Bay exhibited overlapping distributions along the salinity gradient to a location in brackish water where the mean salinity was approximately 5%_o. At this salinity, a relatively sharp discontinuity in the diatom flora existed which appeared to represent the biochemical and biophysical mechanisms involved in the osmotic regulation of fresh- and brackish-water diatoms. Relatively large disparities m the structure of diatom assemblages were found within relatively small areas of Yaquina Bay. These differences were attributed to properties of the sediment. Differences in diatom assemblages relative to variations in light intensity, water temperature and exposure to intertidal emergence were not apparent from the analysis of field data.     

Light,nutrients and grazing interact to determine stream diatom community composition and functional group structure

1. Benthic algal communities are shaped by the availability of nutrients and light and by herbivore consumption. Many studies have examined how one of these factors affects algal communities, but studies simultaneously addressing all three are rare. 2. We investigated the effects of nutrients, light and a herbivore (the snail Potamopyrgus antipodarum) on benthic stream algae in a fully factorial experiment in 128 circular streamside channels. Four nutrient levels (none added to highly enriched), four snail grazing pressures (no snails to 777 individuals m^?2) and two light levels (ambient and 65% reduced) were applied. Colonising algae were dominated by diatoms (Bacillariophyta), which were determined to species using acid‐cleaned samples and assigned to functional groups according to their physiognomic growth form. 3. Diatom community structure changed considerably in response to our manipulations. Light had the strongest influence (as indicated by manova effect size), whereas nutrients had an intermediate effect and grazing was fairly weak. Relative abundances of six common diatom taxa decreased under reduced light, whereas five others became more prevalent. Eight taxa benefitted from nutrient enrichment, while three became rarer. Grazing affected the relative density of only one common taxon, which increased at higher grazing pressure. 4. Diatom functional groups also responded strongly. ‘Low profile’ taxa dominated at low resource levels (nutrients and especially light), whereas ‘high profile’ and ‘motile’ taxa became markedly more prevalent at higher resource levels. 5. Two‐way interactions between experimental factors were quite common. For example, Planothidium lanceolatum and Rossithidium petersenii responded more strongly to nutrient enrichment at reduced than at ambient light, whereas Cocconeis placentula responded more strongly at ambient light. For diatom functional groups, the benefit of nutrient enrichment for ‘motile’ diatoms was greater at ambient than at reduced light. 6. Our results imply that multifactor experiments are required to determine the main forces driving the composition of benthic algal communities. Further, our findings highlight the considerable potential of using functional algal groups as indicators of changing environmental conditions to complement the traditional taxonomic approach.     

Beta diversity of stream diatoms at two hierarchical spatial scales: implications for biomonitoring

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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     

Biodiversity and ecology of epilithic diatoms in the Agnéby River,Ivory Coast

The ecology and taxonomy of the epilithic diatom flora of the Agnéby River, Ivory Coast were studied in 2012. Ten sites were investigated and diatoms were sampled on glass slides immersed for a period of 30 days during the wet and dry seasons. Physico-chemical parameters were measured at each site while sampling diatoms. Five taxa were largely dominant: Planothidium comperei CE Wetzel, N’Guessan and Tison-Rosebery, Eolimna minima (Grunow) Lange-Bertalot, Planothidium piaficum (JR Carter and Denny) CE Wetzel and Ector, Cocconeis schroederi Foged and Cocconeis scutellum var. parva (Grunow in Van Heurck) Cleve. Electrical conductivity, temperature, dissolved oxygen, nitrite and phosphorus were found to influence the distribution of taxa.     

THE DISTRIBUTION OF EDAPHIC DIATOMS ALONG ENVIRONMENTAL GRADIENTS OF A LOUISIANA SALT MARSH1

Edaphic (sediment-associated) diatoms were collected from five sites along a gradient from slightly brackish to saline marsh on 30 November 1977 and 29 April 1978. Several environmental factors change along this gradient in addition to salinity, including tidal flushing and percent organic content of the soil. A total of 112 taxa were identified, with Amphora exigua Greg., Navicula phyllepta Kütz., N. salinarum Grun., and N. tripunctata (Müll.) Bory being among the five most abundant taxa on both sampling dates. The taxonomic composition of the diatom flora was very similar to those observed for other salt marshes located along the Gulf and Atlantic coasts. Diatom taxa were generally euryhaline and distributed continuously along the gradient from brackish to saline marsh. Species diversity (H¹) and the number of taxa in a sample (S) were also similar to those reported for other North American salt marshes. The number of taxa in a sample was higher in the saline than in the brackish area on both sampling dates while species diversity was greater in the saline area only in April.     

The insight into diatom diversity,ecology, and biogeography of an extreme cold ultraoligotrophic Lake Labynkyr at the Pole of Cold in the northern hemisphere

The freshwater ultraoligotrophic Lake Labynkyr is located near the Pole of Cold in the northern hemisphere (Yakutia, Russia). The lake is covered by ice during 240 days a year. We undertook several expeditions to the lake during the ice and open water periods for sampling ice fouling, plankton and periphyton that were then analyzed by means of scanning electron microscopy. As a result, we identified a high biodiversity of diatoms—123 species and intraspecific taxa from 53 genera, among them 3 species were new for Russia and 26 taxa were new for the algal flora of Yakutia. The oligo- and xenosaprobionts and their variations dominate—71 taxa. 18 Species were evaluated as tolerant to cold oligotrophic waters, 12 occurred on the ice bottom, and 62 in the water column under ice (0–25 m). 104 taxa were found during the open water period, 70 taxa were identified in the periphyton. We showed the diatom flora of Lake Labynkyr to be unique compared with other lakes of Yakutia and to share taxa with the diatom flora of Lake Baikal. The diatoms being indicators of the global climate changes and ecological status of lakes, our data can be used as an evidence of such changes as well as to be useful studies of biogeography and history of formation of flora in Arctic and Subarctic waters.

     

Diversity, ecology and biogeography of the freshwater diatom communities from Ulu Peninsula (James Ross Island, NE Antarctic Peninsula)

The diversity, ecology and biogeography of diatoms in lakes, seepage areas and streams on the Ulu Peninsula, a large ice-free area in the northern part of James Ross Island (Weddell Sea), were studied. A diverse diatom flora of 123 taxa was observed, dominated by several Nitzschia taxa, Psammothidium papilio, Eolimna jamesrossensis, Fragilaria capucina and Fistulifera saprophila. The results from the similarity and diversity analysis suggest James Ross Island to be biogeographically positioned within the Maritime Antarctic region, yet with some affinities with the flora of Continental Antarctica, as shown by the presence of Luticola gaussii and Achnanthes taylorensis. Based on our data, James Ross Island can thus be located close to the boundary of the two main Antarctic biogeographical regions. Diatom communities present in streams and seepage areas could be clearly distinguished from those in lakes, the latter being much more species rich. Based on the multivariate analysis, conductivity and nutrients were selected as the two main environmental factors determining the diatom composition in the Ulu Peninsula lakes. The revised taxonomy of the Antarctic diatom flora induced the construction of a transfer function for water conductivity in the studied lakes that can be applied in further palaeoecological studies.     

Adult Male Density Influences Juvenile Microhabitat Use in a Territorial Lizard

Habitat choice often has strong effects on performance and fitness. For many animals, optimal habitats differ across age or size classes, and individuals shift habitat use through ontogeny. Although many studies document ontogenetic habitat shifts for various taxa, most are observational and do not identify the causal factor of size‐specific habitat variation. Field observations of the brown anole lizard (Anolis sagrei) show that juveniles perch on shorter and thinner vegetation than adults. We hypothesized that this variation is due to adult males forcing smaller juveniles to less preferred habitat. To test this assertion, we manipulated adult male densities in mesh enclosures with artificial trees to examine the response of juvenile microhabitat choice. We found that adult male density had strong effects on juvenile perch height, perch width, and substrate use, suggesting that age‐class competition contributes to the observed ontogenetic differences in habitat choice. We also found that time of day significantly affected juvenile perch height and substrate use. In many cases, our results suggest that juveniles distance themselves from adults using different microhabitats from those used in our control ‘no‐adult’ treatment. However, these findings were often body size dependent and varied depending upon time of day. This study highlights the complexity of juvenile perching behavior and demonstrates the role of intraspecific interactions in shaping habitat use by juvenile animals.     

Freshwater diatoms from Ile de la Possession (Crozet Archipelago, sub-Antarctica): an ecological assessment

An ecological study of freshwater waterbodies on Ile de la Possession (Crozet Archipelago, Antarctica) was undertaken during the austral summer of 1997/1998. Both diatom and chemistry data were collected. A highly diverse diatom flora of 210 taxa, belonging to 32 genera, was identified from 127 samples. The most abundant genera were Fragilaria, Achnanthes and Navicula. Principal Component Analysis was used to classify the samples on the basis of their chemical characteristics. The analysis revealed that pH and chloride were the main factors dividing the samples into three categories: rivers, more acid lakes, and lakes with higher chloride content. Species assemblages correspond well with this division. Forward selection with Monte Carlo permutations selected pH, chloride, habitat and hardness. Based on the analysis, four groups of samples can be made: rivers, acid lakes, circumneutral lakes with low chloride concentrations and coastal pools with relatively high chloride levels. The results also indicate that a specific diatom flora exists on the island, which is comparable to that of other islands in the same area (Kerguelen and Macquarie). Accepted: 29 March 1999