Diatoms of surface sediments of Utah Lake,Utah, U.S.A.

Diatoms in fifty-seven surface sediment samples from Utah Lake were examined. Three hundred and fifteen taxa in forty-three genera were identified and quantified. Statistical analyses of the data showed that distinct geographical subregions of the lake could be delineated according to population patterns of the bottom sediment diatoms. In particular, both Provo Bay and Goshen Bay were distinct from each other and from other areas of the lake.     

The effects of a new reservoir on the attached diatom communities in Huntington Creek,Utah, U.S.A.

A study was made to determine whether a new reservoir being constructed on Huntington Creek, Utah would have significant effects on the attached diatom communities of the stream. Cluster analysis and other statistical methods indicated only small differences in the diatom communities before and after construction of the dam.     

A comparison of marine planktonic and sediment core diatoms in Hong Kong with emphasis on Pseudo-nitzschia

Potentially toxic diatoms belonging to the genus Pseudo-nitzschia were observed for the first time in plankton samples from Hong Kong collected in 1996. To determine whether potentially toxic diatoms had become more common during the last six decades, three gravity cores were taken from the anaerobic sediments of Kowloon Bay in Victoria Harbour. Anaerobic sediments are thought to be ideal for palaeoecological reconstructions because their vertical stratigraphy is undisturbed by bioturbidation. Analysis of the Kowloon Bay sediment cores indicated that very few individual diatoms belonged to the genus Pseudo-nitzschia, even though Pseudo-nitzschia was found in abundance in many of the plankton samples taken from a nearby site. The relative absence of Pseudo-nitzschia frustules was interpreted as indicating that these thin walled, poorly silicified, planktonic diatoms failed to preserve in the saline (32–34‰), slightly alkaline (pH 7.6–7.8), anaerobic sediments of Kowloon Bay. Dissolution of thinly silicified diatoms rather than predation was believed to be the reason for their virtual absence in the core. The anaerobic conditions near the bottom of Kowloon Bay and the shallowness of the Bay, 12 m, makes predation an unlikely explanation. Diatom abundance declined in the sediment cores below a depth of 15 cm (ca 1955). This was attributed to the decrease in nutrient loading to Victoria Harbour prior to 1955 rather than enhance diatom dissolution in the deeper sediments. Benthic diatoms became proportionately more abundant below the15 cm core depth. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Metals,trace elements,and organochlorine compounds in bottom sediment of Tuttle Creek Lake,Kansas, U.S.A.

Bottom-sediment cores were used to investigate the occurrence of 44 metals and trace elements, and 15 organochlorine compounds in Tuttle Creek Lake, a reservoir with an agricultural basin in northeast Kansas, U.S.A. On the basis of U.S. Environmental Protection Agency sediment-quality guidelines, concentrations of Ag, As, Cr, Cu, Ni, and Zn frequently or typically exceeded the threshold-effects levels for toxic biological effects. Organochlorine compounds either were not detected or were detected at concentrations generally below the threshold-effects levels. Statistically significant positive depositional trends were determined for several elements. However, because the vertical profiles of element concentrations typically indicated a bimodal distribution and much of the variability could be attributable to analytical variance, the statistical trends may not represent actual trends. DDE concentrations reflected the history of DDT use. Substantial increases in grain corn and soybean production, irrigated land, and hog production in the basin have not had a discernible effect on sediment quality in the reservoir. Future research focused on small impoundments throughout the basin may enhance understanding of the effects of human activity on sediment quality within the Tuttle Creek Lake system and elsewhere.     

The effects of dissolved heavy metals on attached diatoms in the Uintah Basin of Utah,U.S.A.

The relationships of diatom species to dissolved heavy metals in the streams of the Uintah Basin of Utah were studied through four seasons of 1977–1978. Niche center gradient analysis, cluster analysis and correlation analysis were performed.Achnanthes minutissima, Cyclotella meneghiniana, Cymbella minuta, Gomphonema parvulum, Navicula secreta var.apiculata, Nitzschia frustulum, Nitzschia frustulum var.perminuta, Nitzschia frustulum var.perpusilla, Nitzschia palea, andSynedra ulna appear to be indicator species of high or low heavy metal concentrations. Several other species also showed meaningful relationships to high or low heavy metal concentrations.Dept. of Physics and Astronomy, Brigham Young UniversityDept. of Physics and Astronomy, Brigham Young University     

Spatial and temporal distribution of freshwater sponges in Connecticut lakes based upon analysis of siliceous spicules in dated sediment cores

A survey of 28 Connecticut water bodies for spicular remainsoffreshwater sponges preserved in lacustrine sediments revealed14species representing 10 genera. Sediments were examined atfivelevels (ca 1991, ca 1970, ca 1934, ca 1890, ca 1875)todocument changes in species composition, distribution, andabundance. Five species were recorded statewide in all fivegeologic regions: Spongilla lacustris, Heteromeyeniatubisperma, Anheteromeyenia ryderi, Eunapius fragilis, andEphydatia muelleri. Spongilla lacustris was the mostcommonand widely distributed species. Factors that may havecontributedto the observed distribution of the spongillids in Connecticutareregional differences in lake water chemistries, individualspeciestolerances, and differences in extent of dispersal of variousspecies. Most of the more abundant species are widelydistributedwith respect to water quality parameters. Anheteromeyeniaargyrosperma, Duosclera mackayi and Trochospongillapennsylvanica appear to be restricted to waters exhibitingthelower ranges for conductivity, alkalinity and calcium content.Ingeneral, a greater number of spicules was found in bottomsedimentsof the surveyed lakes as compared with the surface sediments.Oftenthis was correlated with increased sediment accumulation ratesinmore recent periods. When this fact is taken into account, itappears that populations of a number of sponge species haveremained relatively constant in many of the lakes over thepastcentury. However, in some lakes exhibiting lower or onlyslightlyhigher sediment accumulation rates at the surface, fewerspiculeswere also found in more recent sediments, suggesting an actualdecline in sponge population sizes. Changes in abundance overthelast 100 years may be related to changes in land use practicesinsurrounding watersheds and the associated changes in waterchemistries.     

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.     

The effects of selected physical and chemical factors on attached diatoms in the Uintah Basin of Utah,U.S.A.

The relationships of diatom species to selected physical and chemical parameters in the streams of the Uintah Basin of Utah were studied through four seasons of 1977–1978. Niche center gradient analysis, cluster analysis and correlation analysis were performed.Achnanthes minutissima, Cyclotella meneghiniana, Cymbella minuta var.latens, Fragilaria capucina, andNavicula secreta var.apiculata appear to be indicator species of high or low levels of certain water quality parameters. Several other species also showed meaningful relationships to selected physical and chemical parameters.     

Mercury accumulation in sediment cores and along food chains in two regions of the Brazilian Pantanal

The Pantanal is a 140,000 km² floodplain wetland stretching acrosswestern Brazil and parts of Bolivia and Paraguay. Gold mining withmercury (Hg) amalgamation has thrived since 1980 along its northern rim. We quantified Hg accumulation in sediment cores (N = 5) and food chainsin this general region of the northern Pantanal and in a reference region,200 km deeper into the wetland (Acurizal). Cores were dated with²¹⁰Pb and ¹³⁷Cs using direct gamma-assay. Total Hg wasanalyzed by cold-vapor atomic fluorescence using a gold-meshpre-concentration trap. Average pre-1940 Hg accumulation in cores wasnot significantly different (N = 5, p= 0.14) between both regions andcomparable with rates calculated for global reference sites. Post gold-rushHg (post-1980) deposition averaged 55 ± 11.3 g m^-2yr^-1 in the northern impacted region and was more than 1.5 timeshigher than the post-1980 rate in Acurizal, implying a regional Hg effectof gold mining. Post-1980 Hg accumulation in Acurizal, in turn, was 2.1times the rate reported for a global reference during that time period,suggesting an additional basin-wide effect over such reference sites. Bycombining our core data with assessments of the size of the impacted areaand the amount of Hg released to the region since 1980, we estimated thatonly 2–8% of this Hg was recovered as a sedimentary signal. Theremainder of the Hg was lost to the atmosphere, downstream areas, orstored in biota. Hg concentrations in surface sediments in the northernPantanal (45.5 ± 5.5 ng g_dry ^-1) were significantlyhigher than those in our reference region (29.1 ± 0.7ng g_dry ^-1). Hg levels in primary producers were alsoelevated in the northern Pantanal. Eichhornia crassipes rootscontained 2.7–3.0 times more mercury than shoots in both regions and Salvinia auriculata, suggested as a biological monitor for Hg pollution,contained almost four times more mercury in the northern Pantanal (90.7± 9.1 ng g_dry ^-1) than in Acurizal (24.5 ± 3.3ng g_dry ^-1). Plant grazers and scavengers, such as apple snails(Pomacea sp.) and adult water beetles (Fam. Hydrophilidae), werelow in Hg, confirming previous data showing that the channeling of mercuryfrom lower to higher trophic levels along herbivorous links was inefficientcompared to transfer along carnivorous links. Collections of 12–16individuals of four species of Characidae (Aphyocharax sp., Tetragonopterus sp., Serrasalmus spiropleura and Pygocentrisnattereri) in both regions showed elevated Hg body burdens in bothpiranhas S. spiropleura and P. nattereri from the northernPantanal (149.9 ± 84.2 and 302.2 ± 159.1ng g_dry ^-1, respectively). Fish length for each species was notstatistically different between regions. P. nattereri length correlatedsignificantly (p<0.001) with Hg content in both regions, but the slopeof the regression in the northern Pantanal was 2.6 times the slope for theAcurizal collection, indicating an elevated rate of biomagnification in theHg-impacted region. Signals of Hg use in mining can be quantified insediment core chronologies and biological tissues, although species atdifferent trophic levels show dissimilar impacts. Mechanisms involved in Hgmagnification along food chains deserve more attention, particularly intropical regions where the threat of chronic exposure to this neurotoxinmay have the greatest implications for biodiversity.     

Diatoms of Lake Peipsi-Pihkva: a floristic and ecological review

463 taxa of diatoms have been recorded from the pelagic and littoral plankton, benthos and periphyton of Lake Peipsi-Pihkva. This typical eutrophic plain lake has many common features with large lakes of both Central and North Europe. As to the richness of diatom taxa, L. Peipsi- Pihkva surpasses other eutrophic lowland lakes, which can be explained by the size of this lake, and by the variety of living conditions in it. The list of taxa as well as notes about rare and phytogeographically interesting diatoms are presented.Deceased.     

Eutrophication,recovery and temperature in Lake Mjøsa: detecting trends with monitoring data and sediment records

1. How climate warming may interact with other pressures on aquatic ecosystems is an important issue for research and management. We combined lake monitoring data with a palaeolimnological study to explore the combined effects of eutrophication and subsequent oligotrophication with a long‐term temperature increase in epilimnetic waters. Our goals were (i) to evaluate how well sediment‐based reconstructions reflect the instrumental observations, (ii) to use the palaeo‐record to characterise a reference state for the lake and (iii) to explore whether data from the sediment record can aid in separating the effects of nutrient load and temperature in a large and deep lake. 2. Lake Mjøsa is a large and deep lake in south‐eastern Norway. Eutrophication symptoms peaked in the 1970s, which led to extensive measures to reduce the phosphorus load. A monitoring programme has run continuously from 1972. Monitoring has documented a marked decrease in phosphorus load and algal biomass and also revealed an increase in epilimnetic temperature and extended summer stratification. 3. Records of algal pigments and diatoms were extracted from sediment cores taken from 236 m depth. The pigment record documented dramatic changes in lake production consistent with the monitoring record. The diatom record reflected well the eutrophication history of the lake and also demonstrated that the assemblage of the recent recovery stage differs from that of the pre‐eutrophication period. 4. Ordination of diatom assemblages over time constrained by proxies for nutrient load and temperature indicated that the diatom assemblage correlated with both factors, which together accounted for 60% of the variation in diatom composition. No interaction was detected between these factors. The results suggest that the diatom assemblage has responded to varying nutrient loads as well as to changes in temperature and/or factors that correlate with temperature. 5. Reconstructions of algal biomass and total phosphorus content mirrored known changes through the monitoring period, although the absolute phosphorus estimates were too high relative to the instrumental record. The sediment record from Lake Mjøsa provides a baseline for lake production in terms of algal pigments and organic contents, and for the diatom assemblage composition in a pristine stage.     

Patterns of vegetation surrounding springs in Goshen Bay,Utah County,Utah U.S.A.

Saline meadows in Goshen Bay, Utah County, Utah, USA, occur interspersed among large areas of salt playa. Springs irrigate these meadows which show concentric vegetational zones surrounding each spring. Each vegetational zone demonstrates its own unique dominant vascular plant species. The central zone is dominated primarily by Scirpus americanus, the middle zone by Eleocharis palustris and the outer zone by Juncus balticus, Distichlis spicata and Muhlenbergia asperifolia. As distance increases from the springs, pH and soluble salt concentration increase, while percent organic matter, percent moisture and phosphorus decrease. With the increase in salt levels and decrease in water levels, halophytic plant species generally increase with distance from the springs.     

Zooplankton (Cladocera, Ostracoda), Chironomidae and other benthic faunal remains in sediment cores from nine North African wetland lakes: the CASSARINA Project

Palaeolimnological studies were carried out on sediment cores from nine North African wetland lakes. The lakes represented a variety of habitats ranging from freshwater to mixohaline conditions and with and without direct connections to the sea. Sediment cores were examined for records of recent environmental change during the 20th century period. Faunal remains analysed in the sediments included those of Cladocera, Ostracoda, Chironomidae, Mollusca and, at the sites with marine connections, Foraminifera. Cyprideis torosa littoralis was the most common ostracod, occurring in sediments from the seven sites linked with the sea and also in brackish water Sidi Bou Rhaba. In acid Megene Chitane ostracods were scarce, being represented by a single species (Cypria ophtalmica). Candona neglecta completely disappeared at two sites (Sidi Bou Rhaba and Bokka) during the 20th century. Of the Cladocera, Chydorus sphaericus was common in the moderately mixohaline sites and but Heterocypris salina occurred only where marine salinities were occasionally achieved (in Zerga, Ichkeul and Korba). Microinvertebrate assemblages in the Nile Delta lake cores and to a less extent in Zerga showed a clear response indicative of more fresher conditions occurring during the latter part of the 20th century. However the freshening trend began prior to construction of the Aswan High Dam (mid 1960s).With the exception of the most saline site (Korba), microinvertebrate communiuties at all the CASSARINA sites have experienced major disturbances during the 20th century. Changes in freshwater availability associated with increased human usage of water resources is perceived as a major factor regulating the abundance and occurrence of aquatic microinvertebrate species at these sites     

Diatoms in Lowland Ponds of Koshi Tappu,Eastern Nepal – Relationships with Chemical and Habitat Characteristics

Epiphytic and epipelic diatom assemblages were studied in relation to water chemistry and habitat character in lowland ponds of Koshi Tappu, Nepal. Epiphytic assemblages from different microhabitats, such as morphologically different plants, roots, stems, filamentous algae and decomposing leaves, within the same ponds were similar. Assemblage composition of epiphytic diatoms reflected gradients in water chemistry and habitat character of the pond with respect to pond vegetation and substratum type, bank profile and land use in the catchment. Epiphytic and epipelic assemblages responded to chemical gradients in the surface water, particularly concentrations of Ca, Mg and Na, but epipelic diatoms also indicated differences in SO₄. Epipelic diatoms were also sensitive to interstitial water chemistry variations in PO₄, Si, Ca and Mg. There were no relationships between species richness, diversity or evenness and gradients in water chemistry and habitat character. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Interpretation of bryozoan microfossils in lacustrine sediment cores

Bryozoan statoblasts were isolated from the surficial sediments of 30 Florida lakes representing a gradient of trophic conditions. A prerequisite for lake selection was a good data base for water chemistry that was collected within the past 5–10 years. A novel technique of employing 210-Pb as a dilution tracer was used to estimate sedimentation rates for each lake. The net annual accumulation rate for bryozoan statoblasts was calculated for each lake and correlated with twelve physical, chemical, and biological variables. The results suggest that bryozoan distributions are strongly controlled by the extent of the littoral zone and phytoplankton biomass. It appears that bryozoan abundance in excessively weeded lakes may be limited by phytoplankton in spite of the richly developed habitat. Separation of the importance of food requirements from habitat requirements was not possible from this initial survey.     

The Diatoms,Productivity and Morphometry of 43 Lakes in New York State,U.S.A

Diatoms were examined in surface sediments collected from 43 lakes throughout New York State to determine the interrelationships among the abundances of various diatom taxa,' lake productivity and lake morphometry. Diatom ratios, including the A/C, C/P and five new quotients, were not well correlated with lake productivity, probably because of the diversity of the taxa which they employ. The abundance of individual genera or combinations of genera were better indicators of productivity. Cyclotella was the best single indicator of productivity being most abundant in low productivity lakes. Several fairly distinct diatom associations were identified by correlations between all possible pairs of diatom taxa. Finally, lake productivity was found to be significantly correlated with morphometry, being highest in small/shallow lakes.     

Seasonal changes in sedimenting material collected by high aspect ratio sediment traps operated in a holomictic eutrophic lake

Cylindrical sediment traps with an aspect ratio (height (60 cm): diameter (5.1 cm)) of 11.8 were located 1 m above the surface sediment by a rigid metal framework support. Traps were exposed in Lough Neagh for one year, from May 1978. Each trap collected between 11 and 12 cm of faintly laminated sediment. One 12 cm sediment column was examined using conventional palaeolimnological techniques of core extrusion and analysis. The algal record in trapped sediment is shown to correspond with successional changes in phytoplankton abundance in the lake during the year of study. The sediment accumulation rate measured by the traps is an order of magnitude greater than that measured in dated sediment cores and redeposited and inwashed sediment formed the bulk of trapped material. However, the value of these high aspect ratio traps is that they provide a continuous but qualitative account of compositional changes in sedimenting material through time. Their potential as long term biological monitoring devices is emphasized.