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Algal Biomass (algal + biomass)
Kinds of Algal Biomass Selected AbstractsDisturbance history influences the distribution of stream invertebrates by altering microhabitat parameters: a field experimentFRESHWATER BIOLOGY, Issue 5 2008MICHAEL EFFENBERGER Summary 1. We investigated the effects of local disturbance history and several biotic and abiotic habitat parameters on the microdistribution of benthic invertebrates after an experimental disturbance in a flood-prone German stream. 2. Bed movement patterns during a moderate flood were simulated by scouring and filling stream bed patches (area 0.49 m2) to a depth of 15,20 cm. Invertebrates were investigated using ceramic tiles as standardized substrata. After 1, 8, 22, 29, 36 and 50 days, we sampled one tile from each of 16 replicates of three bed stability treatments (scour, fill and stable controls). For each tile, we also determined water depth, near-bed current velocity, the grain size of the substratum beneath the tile, epilithic algal biomass and standing stock of particulate organic matter (POM). 3. Shortly after disturbance, total invertebrate density, taxon richness and density of the common taxa Baetis spp. and Chironomidae were highest in stable patches. Several weeks after disturbance, by contrast, Baetis spp. and Hydropsychidae were most common in fill and Leuctra spp. in scour patches. The black fly Simulium spp. was most abundant in fill patches from the first day onwards. Community evenness was highest in scour patches during the entire study. 4. Local disturbance history also influenced algal biomass and POM standing stock at the beginning of the experiment, and water depth, current velocity and substratum grain size throughout the experiment. Scouring mainly exposed finer substrata and caused local depressions in the stream bed characterized by slower near-bed current velocity. Algal biomass was higher in stable and scour patches and POM was highest in scour patches. In turn, all five common invertebrate taxa were frequently correlated with one or two of these habitat parameters. 5. Our results suggest that several ,direct' initial effects of local disturbance history on the invertebrates were subsequently replaced by ,indirect' effects of disturbance history (via disturbance-induced changes in habitat parameters such as current velocity or food). [source] Local disturbance history affects patchiness of benthic river algaeFRESHWATER BIOLOGY, Issue 9 2003Christoph D. Matthaei Summary 1.,Recent research has shown that high-flow events in streams leave a small-scale mosaic of bed patches that have experienced scouring, sediment deposition (fill), or remained stable. Few studies have investigated if this ,local disturbance history' contributes to the patchy distribution of benthic organisms in streams and rivers. 2.,In the present research, we demonstrate that local disturbance history in a mid-sized river can have both short- and long-term effects on epilithic algae. Chains buried vertically in the substratum of the river bed (236 in a 800-m reach) indicated that two floods (return periods ,1 year) caused a mosaic of bed patches with different disturbance histories. Once after the first and twice after the second flood, we sampled epilithic algae (mainly diatoms) in replicate patches that had been scoured, filled, or remained stable during the respective event. Algal biomass and cell density per substratum area were determined. 3.,Three months after the first flood, algal biomass, total diatom density, diatom taxon richness, and densities of six of nine most common taxa were highest in fill patches. Six days after the second flood, biomass was highest in stable patches, indicating a refugium function of these patches. The refugium patches consisted of average-sized stones, in contrast to previous studies of flood refugia for benthic algae in which these refugia were always large and/or immobile substrata. Four weeks after the second flood, diatoms tended to be most abundant in scour patches. With one exception, these differences between patch types could not be attributed to differences in local near-bed current velocity or water depth. 4.,The effects of disturbance history were more complex than a simple refugium function of stable patches because algal patterns changed with time since the last disturbance, possibly depending on the successional state of the algal mats. [source] Individual, Population, Community, and Ecosystem Consequences of a Fish Invader in New Zealand StreamsCONSERVATION BIOLOGY, Issue 1 2003Colin R. Townsend But because invaders can have unexpected indirect effects in food webs, invasion ecologists need to integrate processes at the population level and other ecological levels. I describe a series of coordinated studies in New Zealand streams that address the effect of an exotic fish on individual behavior, population, community, and ecosystem patterns. Such case studies are important as an aid to the formulation of policy about invasions that are especially likely to become problematic. At the individual level, grazing invertebrates showed changes in behavior as a result of the introduction of brown trout ( Salmo trutta), a predator that exerts a very different selection pressure than do native fish. At the population level, trout have replaced nonmigratory galaxiid fish in some streams but not others, and have affected the distributions of crayfish and other large invertebrates. At the community level, trout have suppressed grazing pressure from invertebrates and are thus responsible for enhancing algal biomass and changing algal species composition. Finally, at the ecosystem level, essentially all annual production of invertebrates is consumed by trout ( but not by galaxiids), and algal primary productivity is six times higher in a trout stream. This leads, in turn, to an increased flux of nutrients from the water to the benthic community. The trout invasion has led to strong top-down control of community structure and ecosystem functioning via its effects on individual behavior and population distribution and abundance. Particular physiological, behavioral, and demographic traits of invaders can lead to profound ecosystem consequences that managers need to take into account. Resumen: Para desarrollar procedimientos y políticas de manejo efectivos a menudo será necesario conocer la biología de la población de especies invasoras. Sin embargo, debido a que los invasores pueden tener efectos indirectos inesperados en las redes alimenticias, ecólogos de invasión necesitan integrar procesos en la población y otros niveles ecológicos. Describo una serie de estudios coordinados en arroyos de Nueva Zelanda que enfocan el impacto de un pez exótico sobre los patrones de comportamiento individual, de la población, la comunidad y el ecosistema. Tales estudios de caso son importantes como un auxiliar para la formulación de políticas sobre invasiones que pueden ser especialmente problemáticas. Al nivel individual, los invertebrados que pastorean mostraron cambios de conducta como resultado de la introducción de la trucha café ( Salmo trutta), un depredador que ejerce una presión de selección muy diferente a la de los peces nativos. En el nivel de población, las truchas han reemplazado a peces galaxídos no migratorios en algunos arroyos pero no en otros y han afectado las distribuciones de cangrejos de río y otros invertebrados mayores. Al nivel de comunidad, las truchas han suprimido la presión de pastoreo por invertebrados y por lo tanto son responsables del incremento de la biomasa de algas y del cambio en la composición de especies de algas. Finalmente, a nivel de ecosistema, la producción anual de invertebrados esencialmente es consumida por las truchas ( pero no por galaxídos), y la productividad primaria de algas es seis veces mayor en arroyos con truchas. A su vez, esto conduce a incrementos en el flujo de nutrientes del agua hacia la comunidad béntica. La invasión de truchas ha conducido a un fuerte control de arriba hacia abajo de la estructura de la comunidad y del funcionamiento del ecosistema por medio de sus efectos sobre la conducta individual y la distribución y abundancia de la población. Las características fisiológicas, de conducta y demográficas particulares de los invasores pueden llevar a consecuencias profundas en los ecosistemas que los administradores necesitan tomar en consideración. [source] Contrasting microcystin production and cyanobacterial population dynamics in two Planktothrix -dominated freshwater lakesENVIRONMENTAL MICROBIOLOGY, Issue 10 2005Ingmar Janse Summary Microcystin concentrations in two Dutch lakes with an important Planktothrix component were related to the dynamics of cyanobacterial genotypes and biovolumes. Genotype composition was analysed by using denaturing gradient gel electrophoresis (DGGE) profiling of the intergenic transcribed spacer region of the rrn operon (rRNA-ITS), and biovolumes were measured by using microscopy. In Lake Tjeukemeer, microcystins were present throughout summer (maximum concentration 30 µg l,1) while cyanobacterial diversity was low and very constant. The dominant phototroph was Planktothrix agardhii. In contrast, Lake Klinckenberg showed a high microcystin peak (up to 140 µg l,1) of short duration. In this lake, cyanobacterial diversity was higher and very dynamic with apparent genotype successions. Several genotypes derived from DGGE field profiles matched with genotypes from cultures isolated from field samples. The microcystin peak measured in Lake Klinckenberg could be confidently linked to a bloom of Planktothrix rubescens, as microscopic and genotypic analysis showed identity of bloom samples and a toxin-producing P. rubescens culture. Toxin-producing genotypes were detected in the microbial community before they reached densities at which they were detected by using microscopy. Cyanobacterial biovolumes provided additional insights in bloom dynamics. In both lakes, the microcystin content per cell was highest at the onset of the blooms. Our results suggest that while genotypic characterization of a lake can be valuable for detection of toxic organisms, for some lakes a monitoring of algal biomass has sufficient predictive value for an assessment of toxin production. [source] Direct and indirect effects of a potential aquatic contaminant on grazer,algae interactionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009Michelle A. Evans-White Abstract Contaminants have direct, harmful effects across multiple ecological scales, including the individual, the community, and the ecosystem levels. Less, however, is known about how indirect effects of contaminants on consumer physiology or behavior might alter community interactions or ecosystem processes. We examined whether a potential aquatic contaminant, an ionic liquid, can indirectly alter benthic algal biomass and primary production through direct effects on herbivorous snails. Ionic liquids are nonvolatile organic salts being considered as an environmentally friendly potential replacement for volatile organic compounds in industry. In two greenhouse experiments, we factorially crossed four concentrations of 1-N-butyl-3-methylimidazolium bromide (bmimBr; experiment 1: 0 or 10 mg/L; experiment 2: 0, 1, or 100 mg/L) with the presence or absence of the snail Physa acuta in aquatic mesocosms. Experimental results were weighted by their respective control (no bmimBr or P. acuta) and combined for statistical analysis. When both bmimBr and snails were present, chlorophyll a abundance and algal biovolume were higher than would be expected if both factors acted additively. In addition, snail growth rates, relative to those of controls, declined by 41 to 101% at 10 and 100 mg/L of bmimBr. Taken together, these two results suggest that snails were less efficient grazers in the presence of bmimBr, resulting in release of algae from the grazer control. Snails stimulated periphyton primary production in the absence, but not in the presence, of bmimBr, suggesting that bmimBr also can indirectly alter ecosystem function. These findings suggest that sublethal contaminant levels can negatively impact communities and ecosystem processes via complex interactions, and they provide baseline information regarding the potential effects of an emergent industrial chemical on aquatic systems. [source] Effects of insecticide exposure on feeding inhibition in mayflies and oligochaetesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2007Alexa C. Alexander Abstract The present study examined the effects of pulse exposures of the insecticide imidacloprid on the mayfly, Epeorus longimanus Eaton (Family Heptageniidae), and on an aquatic oligochaete, Lumbriculus variegatus Müller (Family Lumbriculidae). Pulse exposures of imidacloprid are particularly relevant for examination, because this insecticide is relatively soluble (510 mg/L) and is most likely to be at effect concentrations during runoff events. Experiments examined the recovery of organisms after a 24-h pulse exposure to imidacloprid over an environmentally realistic range of concentrations (0, 0.1, 0.5, 1, 5, and 10 ,g/L). Effects on feeding were measured by quantifying the algal biomass consumed by mayflies or foodstuffs egested by oligochaetes. Imidacloprid was highly toxic, with low 24-h median lethal concentrations (LC50s) in early mayfly instars (24-h LC50, 2.1 ± 0.8 ,g/L) and larger, later mayfly instars (24-h LC50, 2.1 ± 0.5 ,g/L; 96-h LC50, 0.65 ± 0.15 ,g/L). Short (24-h) pulses of imidacloprid in excess of 1 ,g/L caused feeding inhibition, whereas recovery (4 d) varied, depending on the number of days after contaminant exposure. In contrast to mayflies, oligochaetes were relatively insensitive to imidacloprid during the short (24-h) pulse; however, immobility of oligochaetes was observed during a 4-d, continuous-exposure experiment, with 96-h median effective concentrations of 6.2 ± 1.4 ,g/L. Overall, imidacloprid reduced the survivorship, feeding, and egestion of mayflies and oligochaetes at concentrations greater than 0.5 but less than 10 ,g/L. Inhibited feeding and egestion indicate physiological and behavioral responses to this insecticide. [source] Structural and functional responses of river biofilm communities to the nonsteroidal anti-inflammatory diclofenacENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2007John R. Lawrence Abstract Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) that has been detected widely in surface waters in North America and Europe. The impact of diclofenac on river biofilm communities was investigated at exposures of 10 and 100 ,g L,1 of diclofenac or its molar equivalent in carbon and nutrients. Experiments were carried out with river water during spring and summer using rotating annular reactors as model systems. Diclofenac or nutrients at 10 ,g L,1 were observed to have no significant effect on algal, bacterial, and cyanobacterial biomass in spring, whereas in the summer the nutrient equivalent reduced algal biomass and diclofenac reduced cyanobacterial biomass relative to control biofilms (p < 0.05). In contrast, at 100 ,g L,1 diclofenac or nutrients, the result was increased cyanobacterial and bacterial biomass, respectively, relative to control biofilms in spring. In summer, 100 ,g L,1 diclofenac significantly increased bacterial biomass and the nutrient treatment had no significant effect (p < 0.05); both treatments resulted in increased biofilm thickness. The glycoconjugate composition of the exopolysaccharide matrix was influenced differentially by the treatments in both seasons. Biolog assessments of carbon use indicated that 100 ,g L,1 diclofenac or nutrients resulted in significant depressions in the use of carbon sources in summer and significant increases in spring. Impacts on protozoan and micrometazoan populations also were assessed. Denaturing gradient gel electrophoresis analyses of community DNA and fluorescent in situ hybridization studies indicated that diclofenac had significant effects on the nature of the bacterial community in comparison with control and nutrient-treated river biofilm communities. [source] Development of photosynthetic biofilms affected by dissolved and sorbed copper in a eutrophic riverENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002Christiane Barranguet Abstract Photosynthetic biofilms are capable of immobilizing important concentrations of metals, therefore reducing bioavailability to organisms. But also metal pollution is believed to produce changes in the microalgal species composition of biofilms. We investigated the changes undergone by natural photosynthetic biofilms from the River Meuse, The Netherlands, under chronic copper (Cu) exposure. The suspended particles in the river water had only a minor effect on reduction of sorption and toxicity of Cu to algae. Biofilms accumulated Cu proportionally to the added concentration, also at the highest concentration used (9 ,M Cu). The physiognomy of the biofilms was affected through the growth of the chain-forming diatom Melosira varians, changing from long filaments to short tufts, although species composition was not affected by the Cu exposure. The Cu decreased phosphate uptake and algal biomass measured as chl a, which degraded exponentially in time. Photosynthetic activity was always less sensitive than algal biomass; the photon yield decreased linearly in time. The protective and insulating role of the biofilm, supported by ongoing autotrophic activity, was indicated as essential in resisting metal toxicity. We discuss the hypothesis that the toxic effects of Cu progress almost independently of the species composition, counteracting ongoing growth, and conclude that autotrophic biofilms act as vertical heterogeneous units. Effective feedback mechanisms and density dependence explain several discrepancies observed earlier. [source] Organic matter availability structures microbial biomass and activity in a Mediterranean streamFRESHWATER BIOLOGY, Issue 10 2009JOAN ARTIGAS Summary 1. We compared microbial biomass (bacteria, fungi, algae) and the activity of extracellular enzymes used in the decomposition of organic matter (OM) among different benthic substrata (leaves, coarse and fine substrata) over one hydrological year in a Mediterranean stream. 2. Microbial heterotrophic biomass (bacteria plus fungi) was generally higher than autotrophic biomass (algae), except during short periods of high light availability in the spring and winter. During these periods, sources of OM shifted towards autochthonous sources derived mainly from algae, which was demonstrated by high algal biomass and peptidase activity in benthic communities. 3. Heterotrophic activity peaked in the autumn. Bacterial and fungal biomass increased with the decomposition of cellulose and hemicellulose compounds from leaf material. Later, lignin decomposition was stimulated in fine (sand, gravel) and coarse (rocks, boulders and cobbles) substrata by the accumulation of fine detritus. 4. The Mediterranean summer drought provoked an earlier leaf fall. The resumption of the water flow caused the weathering of riparian soils and subsequently a large increase in dissolved organic carbon and nitrate, which led to growth of bacteria and fungi. [source] Disturbance history influences the distribution of stream invertebrates by altering microhabitat parameters: a field experimentFRESHWATER BIOLOGY, Issue 5 2008MICHAEL EFFENBERGER Summary 1. We investigated the effects of local disturbance history and several biotic and abiotic habitat parameters on the microdistribution of benthic invertebrates after an experimental disturbance in a flood-prone German stream. 2. Bed movement patterns during a moderate flood were simulated by scouring and filling stream bed patches (area 0.49 m2) to a depth of 15,20 cm. Invertebrates were investigated using ceramic tiles as standardized substrata. After 1, 8, 22, 29, 36 and 50 days, we sampled one tile from each of 16 replicates of three bed stability treatments (scour, fill and stable controls). For each tile, we also determined water depth, near-bed current velocity, the grain size of the substratum beneath the tile, epilithic algal biomass and standing stock of particulate organic matter (POM). 3. Shortly after disturbance, total invertebrate density, taxon richness and density of the common taxa Baetis spp. and Chironomidae were highest in stable patches. Several weeks after disturbance, by contrast, Baetis spp. and Hydropsychidae were most common in fill and Leuctra spp. in scour patches. The black fly Simulium spp. was most abundant in fill patches from the first day onwards. Community evenness was highest in scour patches during the entire study. 4. Local disturbance history also influenced algal biomass and POM standing stock at the beginning of the experiment, and water depth, current velocity and substratum grain size throughout the experiment. Scouring mainly exposed finer substrata and caused local depressions in the stream bed characterized by slower near-bed current velocity. Algal biomass was higher in stable and scour patches and POM was highest in scour patches. In turn, all five common invertebrate taxa were frequently correlated with one or two of these habitat parameters. 5. Our results suggest that several ,direct' initial effects of local disturbance history on the invertebrates were subsequently replaced by ,indirect' effects of disturbance history (via disturbance-induced changes in habitat parameters such as current velocity or food). [source] Nutrient dependent effects of consumer identity and diversity on freshwater ecosystem functionFRESHWATER BIOLOGY, Issue 1 2008ANDREW R. DZIALOWSKI Summary 1. Over the past decade, ecologists have tried to determine how changes in species composition and diversity affect ecosystem structure and function. Until recently, the majority of these studies have been conducted in terrestrial ecosystems and have not taken into account environmental variability. The purpose of this research was to determine how species identity and diversity in the freshwater zooplankton affected biomass of algae and zooplankton at two levels of nutrient enrichment. 2. Several species of cladocerans were grown alone and together in microcosms at both ambient and raised phosphorus concentrations to determine if the effects of consumer identity and diversity were nutrient dependent. 3. Total zooplankton biomass was greater, while algal biomass was lower, in mixed culture than in monoculture. The effects of zooplankton diversity on algal biomass, however, were only observed at raised phosphorus concentrations, suggesting that diversity effects were nutrient dependent. Specifically, diversity effects appeared to be related with biological mechanisms such as complementarity in resource use and/or facilitation. 4. More diverse communities of zooplankton appear to be better able to control algae than single species of zooplankton at high nutrient concentrations; therefore, zooplankton diversity may provide a buffer against eutrophication in freshwater ecosystems. [source] Sources and transport of algae and nutrients in a Californian river in a semi-arid climateFRESHWATER BIOLOGY, Issue 12 2007NOBUHITO OHTE Summary 1. To elucidate factors contributing to dissolved oxygen (DO) depletion in the Stockton Deep Water Ship Channel in the lower San Joaquin River, spatial and temporal changes in algae and nutrient concentrations were investigated in relation to flow regime under the semiarid climate conditions. 2. Chlorophyll- a (chl- a) concentration and loads indicated that most algal biomass was generated by in-stream growth in the main stem of the river. The addition of algae from tributaries and drains was small (c.15% of total chl- a load), even though high concentrations of chl- a were measured in some source waters. 3. Nitrate and soluble-reactive phosphorus (SRP) were available in excess as a nutrient source for algae. Although nitrate and SRP from upstream tributaries contributed (16.9% of total nitrate load and 10.8% of total SRP load), nutrients derived from agriculture and other sources in the middle and lower river reaches were mostly responsible (20.2% for nitrate and 48.0% for SRP) for maintaining high nitrate and SRP concentrations in the main stem. 4. A reduction in nutrient discharge would attenuate the algal blooms that accelerate DO depletion in the Stockton Deep Water Ship Channel. The N : P ratio, in the main stem suggests that SRP reduction would be a more viable option for algae reduction than nitrogen reduction. 5. Very high algal growth rates in the main stem suggest that reducing the algal seed source in upstream areas would also be an effective strategy. [source] Undesirable side-effects of water hyacinth control in a shallow tropical reservoirFRESHWATER BIOLOGY, Issue 6 2007DENISE DE C. BICUDO Summary 1. Based on a comprehensive data set collected monthly during 8 years (1997,2004), we evaluated the effects of mechanical removal of Eichhornia crassipes on the limnological characteristics and algal biomass of a polymictic shallow tropical reservoir. 2. Interrupted time series analyses indicated that the limnological responses to macrophyte removal can be classified as an ,abrupt permanent impact' implying that the overall mean of the time-series shifted promptly after intervention. These analyses indicated a significant increase for pH, total phosphorus, total phytoplankton and cyanobacterial biomass, and a decrease in water transparency and CO2 concentrations in the surface water; also, the increase in water stability, increase of bottom soluble reactive phosphorus (SRP) and decrease in bottom oxygen levels. 3. Cyclic anoxic periods previously observed during springs and summers were replaced by a persistent period of anoxic conditions in the sediment overlying water. Anoxic conditions were suitable for SRP release from sediments. Heavy cyanobacterial blooms became more persistent, maximum biomass (4229 mm3 L,1) was 30 times larger, the blooms frequently reached 2 m and sometimes the bottom of the reservoir, contrasting to the preremoval period in which it reached at most 1 m deep. 4. The long-term P dynamics in the system, initially driven by allochthonous nutrient loadings were replaced by internal ecological processes. Water hyacinth removal markedly accelerated the process of eutrophication due to internal feedback mechanisms, leading to a switch to a more turbid state. Biological feedback mechanisms were driven by cyanobacterial blooms by enhancing water stability, oxygen anoxia at the bottom and by increasing suitable conditions for P internal loading. These data support the hypothesis of the role of cyanobacterial blooms as an important factor impairing water quality and driving the ecosystem towards a stable degraded state. 5. These findings have important implications for the restoration of shallow stratifying eutrophic lakes, as the alternative degraded state is most likely to occur when compared with their non-stratifying counterparts. Moreover, feedback mechanisms in tropical and subtropical shallow lakes seem to be stronger than in temperate ones, as stratification events are more likely to occur over the year, intensifying system resilience to restorative strategies. [source] Priming the productivity pump: flood pulse driven trends in suspended algal biomass distribution across a restored floodplainFRESHWATER BIOLOGY, Issue 8 2006DYLAN S. AHEARN Summary 1. Chlorophyll a (Chl a) distribution across a 0.36 km2 restored floodplain (Cosumnes River, California) was analysed throughout the winter and spring flood season from January to June 2005. In addition, high temporal-resolution Chl a measurements were made in situ with field fluorometers in the floodplain and adjacent channel. 2. The primary objectives were to characterise suspended algal biomass distribution across the floodplain at various degrees of connection with the channel and to correlate Chl a concentration and distribution with physical and chemical gradients across the floodplain. 3. Our analysis indicates that periodic connection and disconnection of the floodplain with the channel is vital to the functioning of the floodplain as a source of concentrated suspended algal biomass for downstream aquatic ecosystems. 4. Peak Chl a levels on the floodplain occurred during disconnection, reaching levels as high as 25 ,g L,1. Chl a distribution across the floodplain was controlled by residence time and local physical/biological conditions, the latter of which were primarily a function of water depth. 5. During connection, the primary pond on the floodplain exhibited low Chl a (mean = 3.4 ,g L,1) and the shallow littoral zones had elevated concentrations (mean = 4.6 ,g L,1); during disconnection, shallow zone Chl a increased (mean = 12.4 ,g L,1), but the pond experienced the greatest algal growth (mean = 14.7 ,g L,1). 6. Storm-induced floodwaters entering the floodplain not only displaced antecedent floodplain waters, but also redistributed floodplain resources, creating complex mixing dynamics between parcels of water with distinct chemistries. Incomplete replacement of antecedent floodplain waters led to localised hypoxia in non-flushed areas. 7. The degree of complexity revealed in this analysis makes clear the need for high-resolution spatial and temporal studies such as this to begin to understand the functioning of dynamic and heterogeneous floodplain ecosystems. [source] Catchment urbanisation and increased benthic algal biomass in streams: linking mechanisms to managementFRESHWATER BIOLOGY, Issue 6 2004Sally L. Taylor Summary 1. Urbanisation is an important cause of eutrophication in waters draining urban areas. We determined whether benthic algal biomass in small streams draining urban areas was explained primarily by small-scale factors (benthic light, substratum type and nutrient concentrations) within a stream, or by catchment-scale variables that incorporate the interacting multiple impacts of urbanisation (i.e. variables that describe urban density and the intensity of drainage or septic tank systems). 2. Benthic algal biomass was assessed as chlorophyll a density (chl a) in 16 streams spanning a rural,urban gradient, with both a wide range of urban density and of piped stormwater infrastructure intensity on the eastern fringe of metropolitan Melbourne, Australia. The gradient of urban density among streams was broadly correlated with catchment imperviousness, drainage connection (proportion of impervious areas connected to streams by stormwater pipes), altitude, longitude and median phosphorus concentration. Catchment area, septic tank density, median nitrogen concentration, benthic light (photosynthetically active radiation) and substratum type were not strongly correlated with the urban gradient. 3. Variation in benthic light and substratum type within streams explained a relatively small amount of variation in log chl a (3,11 and 1,13%, respectively) compared with between-site variation (39,54%). 4. Median chl a was positively correlated with catchment urbanisation, with a large proportion of variance explained jointly (as determined by hierarchical partitioning) by those variables correlated with urban density. Independent of this correlation, the contributions of drainage connection and altitude to the explained variance in chl a were significant. 5. The direct connection of impervious surfaces to streams by stormwater pipes is hypothesised as the main determinant of algal biomass in these streams through its effect on the supply of phosphorus, possibly in interaction with stormwater-related impacts on grazing fauna. Management of benthic algal biomass in streams of urbanised catchments is likely to be most effective through the application of stormwater management approaches that reduce drainage connection. [source] Local disturbance history affects patchiness of benthic river algaeFRESHWATER BIOLOGY, Issue 9 2003Christoph D. Matthaei Summary 1.,Recent research has shown that high-flow events in streams leave a small-scale mosaic of bed patches that have experienced scouring, sediment deposition (fill), or remained stable. Few studies have investigated if this ,local disturbance history' contributes to the patchy distribution of benthic organisms in streams and rivers. 2.,In the present research, we demonstrate that local disturbance history in a mid-sized river can have both short- and long-term effects on epilithic algae. Chains buried vertically in the substratum of the river bed (236 in a 800-m reach) indicated that two floods (return periods ,1 year) caused a mosaic of bed patches with different disturbance histories. Once after the first and twice after the second flood, we sampled epilithic algae (mainly diatoms) in replicate patches that had been scoured, filled, or remained stable during the respective event. Algal biomass and cell density per substratum area were determined. 3.,Three months after the first flood, algal biomass, total diatom density, diatom taxon richness, and densities of six of nine most common taxa were highest in fill patches. Six days after the second flood, biomass was highest in stable patches, indicating a refugium function of these patches. The refugium patches consisted of average-sized stones, in contrast to previous studies of flood refugia for benthic algae in which these refugia were always large and/or immobile substrata. Four weeks after the second flood, diatoms tended to be most abundant in scour patches. With one exception, these differences between patch types could not be attributed to differences in local near-bed current velocity or water depth. 4.,The effects of disturbance history were more complex than a simple refugium function of stable patches because algal patterns changed with time since the last disturbance, possibly depending on the successional state of the algal mats. [source] Temporal variability of phytoplankton in a salt wedge estuary, the Swan,Canning Estuary, Western AustraliaHYDROLOGICAL PROCESSES, Issue 13 2001Peter A. Thompson Abstract The temporal cycles of variation in salinity, temperature and river flow in the Swan,Canning Estuary plus rainfall in the vicinity are examined. A ,normal' pattern is defined for rainfall and river flow based on long-term median monthly values from available historical data. Long-term monthly median rainfall and median monthly river flow were highly correlated. Deviations from the ,normal' patterns of rainfall and river flow are documented. Three years of detailed data on the temporal distribution of the algal biomass and phytoplankton community composition from the Swan,Canning Estuary are presented and discussed. Significant interannual variability in the phytoplankton biomass was observed with 1996 having a significantly lower median chlorophyll a concentration than 1995 or 1997. Different years also had pronounced differences in the timing, persistence and occurrence of algal blooms. Links with, and between, rainfall, river flow, nutrient concentrations and phytoplankton biomass are made by careful examination of the temporal patterns. Deviations from the proposed ,normal' temporal pattern of physical and chemical environmental factors relevant to the growth of phytoplankton biomass are assessed. Deviations from ,normal' rainfall and river flow, depending upon their timing and intensity, appear to be associated with occurrence of algal blooms. For example, the lack of a dinoflagellate bloom in December 1996 or January 1997 appears to be associated with a wetter than normal spring. Based upon the observed data, published reports and basic principles of algal ecology a set of predicted responses to variation in the major environmental variables (rainfall and river flow) are tabulated. The tabulated predictions are proposed as a useful tool for resource managers. Copyright © 2001 John Wiley & Sons, Ltd. [source] Post-Impoundment Biomass and Composition of Phytoplankton in the Yangtze RiverINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2007Hui Zeng Abstract Damming, and thus alteration of stream flow, promotes higher phytoplankton populations and encourages algal blooms (density >106 cells L,1) in the Three Gorges Reservoir (TGR). Phytoplankton composition and biomass were studied in the Yangtze River from March 2004 to May 2005. 107 taxa were identified. Diatoms were the dominant group, followed by Chlorophyta and Cyanobacteria. In the Yangtze River, algal abundance varied from 3.13 × 103 to 3.83 × 106 cells L,1, and algal biomass was in the range of 0.06 to 659 mg C m,3. Levels of nitrogen, phosphorus and silica did not show consistent longitudinal changes along the river and were not correlated with phytoplankton parameters. Phytoplankton abundance was negatively correlated with main channel discharge (Spearman r = ,1.000, P < 0.01). Phytoplankton abundance and biomass in the Yangtze River are mainly determined by the hydrological conditions rather than by nutrient concentrations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A hollow fiber membrane photo-bioreactor for CO2 sequestration from combustion gas coupled with wastewater treatment: a process engineering approachJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2010Amit Kumar Abstract BACKGROUND: In the presence of light, micro-algae convert CO2 and nutrients to biomass that can be used as a biofuel. In closed photo-bioreactors, however, light and CO2 availability often limit algae production and can be difficult to control using traditional diffuser systems. In this research, a hollow fiber membrane photo-bioreactor (HFMPB) was investigated to: (1) increase the interfacial contact area available for gas transfer, (2) treat high nutrient strength (412 mg NO3, -N L,1) wastewater, and (3) produce algal biomass that can be used as a biofuel. RESULTS: A bench scale HFMPB was inoculated with Spirulina platensis and operated with a 2-15% CO2 supply. A mass transfer model was developed and found to be a good tool to estimate CO2 mass transfer coefficients at varying liquid velocities. Overall mass transfer coefficients were 1.8 × 10,6, 2.8 × 10,6, 5.6 × 10,6m s,1 at Reynolds numbers of 38, 63, and 138, respectively. A maximum CO2 removal efficiency of 85% was observed at an inlet CO2 concentration of 2% and a gas residence time (membrane-lumen) of 8.6 s. The corresponding algal biomass concentrations and NO3 removal efficiencies were 2131 mg L,1 and 68%, respectively. CONCLUSION: The results show that the combination of CO2 sequestration, wastewater treatment and biofuel production in an HFMPB is a promising alternative for greenhouse gas mitigation. Copyright © 2010 Society of Chemical Industry [source] Studies on Temporal and Spatial Variations of Phytoplankton in Lake ChaohuJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2007Dao-Gui Deng Abstract Temporal and spatial variations of the phytoplankton assemblage in Lake Chaohu, a large shallow eutrophic lake in China, were studied from September 2002 to August 2003. A total of 191 phytoplankton species was identified, among which Chlorophytes (101) ranked the first, followed by Cyanophytes (46) and Bacillariophytes (28). On average over the entire lake, the maximum total algal biomass appeared in June (19.70 mg/L) with a minimum (5.05 mg/ L) in November. In terms of annual mean biomass, cyanobacteria contributed 45.43% to total algal biomass, followed by Chlorophytes (27.14%), and Bacillariophytes (20.6%). When nitrate (NO3 -N) and ammonium (NH4 -N) concentrations dropped in spring, fixing-nitrogen cyanobacterium (Anabaena) developed quickly and ranked the first in terms of biomass in summer. It is likely that dominance of zooplanktivorous fish and small crustacean zooplankton favored the development of the inedible filamentous or colony forming cyanobacteria. The persistent dominance of cyanobacteria throughout all seasons may indicate a new tendency of the response of phytoplankton to eutrophication in Lake Chaohu. [source] META-ANALYSIS OF GRAZER CONTROL OF PERIPHYTON BIOMASS ACROSS AQUATIC ECOSYSTEMS,JOURNAL OF PHYCOLOGY, Issue 4 2009Helmut Hillebrand Grazer control of periphyton biomass has been addressed in numerous experimental studies in all kinds of aquatic habitats. In this meta-analysis, the results of 865 experiments are quantitatively synthesized in order to address the following questions: (i) Do lotic, lentic, and marine ecosystems differ in their degree of grazer control of periphyton biomass? (ii) Which environmental variables affect the degree of grazer control? (iii) How much does the result of these experiments depend on facets of experimental design? Across all ecosystems, the grazers removed on average 59% of the periphyton biomass, with grazing being significantly stronger for laboratory (65%) than for field (56%) experiments. Neither field nor lab experiments showed a significant difference among lotic, lentic, and coastal habitats. Among different taxonomic consumer groups, crustaceans (amphipods and isopods) and trichopteran larvae removed the highest proportion of periphyton biomass. Grazer effects increased with increasing algal biomass, with decreasing resource availability and with increasing temperature, especially in field experiments. Grazer effects also increased with increasing total grazer biomass in field experiments but showed the opposite trend in lab experiments, indicating a tendency toward overcrowded lab experiments. Other aspects of experimental design, such as cage type, size, and duration of the study, strongly affected the outcome of the experiments, suggesting that much care has to be placed on the choice of experimental design. [source] 71 Proteomics of haematococcus pluvialis: new opportunities for study of genomics of a non-sequenced speciesJOURNAL OF PHYCOLOGY, Issue 2003Q. Hu The green alga, Haematococcus pluvialis, has become a model organism for commercial production of the high-value carotenoid astaxanthin. H. Pluvialis has also drawn significant scientific attention because fundamental biological questions relating to the massive cellular accumulation of astaxanthin have to be addressed in order to improve the yield and quality of the algal biomass. However, research has been impeded by the lack of molecular background information on this non-sequenced species. A combination of classical biochemistry with a state-of-the-art proteomic approach was used to address these questions. This was possible by taking advantage of information already available for homologous genes/gene-products in organisms whose genomes have been sequenced. The approach involved isolation of subsets of the proteome from subcellular compartments/organelles of an organism by one- or two-dimensional electrophoresis (1-DE or 2-DE) and their identification by N-terminal sequencing and peptide mass fingerprinting (PMF), involving matrix-assisted laser desorption/ionization and time-of-flight (MALDI-TOF) mass spectrometry coupled with bioinformatics. Based upon the information obtained from the combined methods, expression and physiological functions of specific genes/encoded proteins may be deduced. Examples include profiling of cell wall proteins, biogenesis and protein composition of lipid bodies, and expression patterns of soluble proteins under stress conditions. Advantages and limitations of the method for non-sequenced organisms and for cross-species protein identification will also be discussed. [source] EFFECT OF COPPER ON ALGAL COMMUNITIES FROM OLIGOTROPHIC CALCAREOUS STREAMS1JOURNAL OF PHYCOLOGY, Issue 2 2002Helena Guasch Two sets of experiments were done to quantify the effects of chronic copper exposure on natural peri- phyton in a nonpolluted calcareous river. The results of short-term (up to 6 h exposure) experiments corroborated the significance of pH on copper toxicity. Copper toxicity increased when pH was reduced from 8.6 to 7.7, and this was related to the effect of pH on copper speciation (free copper concentration increased from 0.2% to 2.3% of total copper). Longer term experiments demonstrated that periphyton communities exposed to copper under pH variation (8.2,8.6) were already affected at 10 ,g·L,1 (20,80 ng·L,1 Cu2+) after 12 days of exposure. Copper exposure caused stronger effects on structural (algal biomass and community structure) than on functional (photosynthetic efficiency) parameters of peri- phyton. Changes in community composition included the enhancement of some taxa (Gomphonema gracile), the inhibition of others (Fragilaria capucina and Phormidium sp.), and the appearance of filament malformations (Mougeotia sp.). The results of our study demonstrated that several weeks of exposure to copper (10,20 ,g·L,1) were sufficient to cause chronic changes in the periphyton of oligotrophic calcareous rivers. This degree of copper pollution can be commonly found in the Mediterranean region as a result of agricultural practices and farming activities. [source] Nitrogen Sources and Sinks Within the Middle Rio Grande, New Mexico,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2007Gretchen P. Oelsner Abstract:, Relationships between discharge, land use, and nitrogen sources and sinks were developed using 5 years of synoptic sampling along a 300 km reach of the Rio Grande in central New Mexico. Average river discharge was higher during 2001 and 2005 "wet years" (15 m3/s) than during the drought years of 2002-04 "dry years" (8.9 m3/s), but there were no differences in nitrogen loading from wastewater treatment plants (WWTPs) which were the largest and most consistent source of nitrogen to the river (1,330 kg/day). Average total dissolved nitrogen (TDN) concentrations remained elevated for 180 km downstream of the Albuquerque WWTP averaging 1.2 mg/l in wet years and 0.52 mg/l in dry years. Possible explanations for the constant elevated TDN concentrations downstream of the major point source include reduced nitrogen retention capacity, minimal contact with riparian or channel vegetation, large suspended sediment loads, and low algal biomass. Somewhat surprisingly, agricultural return flows had lower average nitrogen concentrations than river water originally diverted to agriculture in both wet (0.81 mg/l) and dry years (0.19 mg/l), indicating that the agricultural system is a sink for nitrogen. Lower average nitrogen concentrations in the river during the dry years can be explained by the input of agricultural returns which comprise the majority of river flow in dry years. [source] Does Pond Water Reflectance Influence Double-crested Cormorant Selection of Aquaculture Ponds?JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2010Andrew A. Radomski Double-crested cormorants, Phalacrocorax auritus, are a frequent and major avian predator on channel catfish, Ictalurus punctatus, and other aquaculture species throughout the southeastern USA. Although cormorant movements and occurrence within the aquaculture production region are understood, no studies have focused on the mechanisms utilized by these avian predators to select foraging sites within these high-density aquaculture systems. The objective of this study was to determine if cormorant abundance is associated with specific (ultraviolet to visible) light reflectance spectra within commercial catfish ponds. Three commercial farms were used in this study; each farm had four ponds classified as "preferred" and another four ponds classified as "avoided" based on observing cormorant numbers for 3 mo prior to reflectance measures (>100 h observation for each pond). Reflectance and pond turbidity were measured weekly for 7 wk during the period of maximal over-wintering cormorant numbers. Water samples were collected at the surface (1 cm depth) and secchi depth (10,41 cm) at two locations (upwind and downwind sides) within each pond to determine spectral reflectance and turbidity. Average pond reflectance values were not significantly different between ponds preferred and avoided by cormorants; however, upwind reflectance significantly differed from downwind reflectance between cormorant use groups. Using cross-validation discriminant analysis, the accuracy of separating upwind ponds preferred and avoided by cormorants was over 62%. Repeated measures ANOVA identified the reflectance at 370, 380, 460, 500, 510, and 620 nm as significantly different between ponds preferred and avoided by cormorants. The lower wavelengths (380,410 nm) correspond to known UV-A sensing compounds in cormorants and the other wavelengths share characteristics associated with algal biomass. Cormorants utilize ponds that have lower algal biomass when compared with avoided ponds. [source] Impact of Copper Sulfate on Plankton in Channel Catfish Nursery PondsJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2009Charles C. Mischke Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04-ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6,12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing. [source] Restoration of Lake Geneva: Expected versus observed responses of phytoplankton to decreases in phosphorusLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2002Orlane Anneville Abstract Long-term phytoplankton responses in Lake Geneva to a decline in phosphorus (P) loading are examined in terms of summer (July,September) biomass and community structure. With the rapid development of human activity on its banks and within its catchment area in the 1960s, this large subalpine hydrosystem shifted from oligotrophy to eutrophy within approximately one decade. Measures to reduce P loading were initiated successfully in the mid-1970s, when total P concentrations in the winter overturn altered from 90 ,g/L in 1980 to 40 ,g/L in 1998. Until the 1990s, algal descriptors improved as expected (biomass decline, reappearance of diatom species, increased contribution of nanoplankton). Then, paradoxically, and in contrast to the reappearance of oligotrophic species, summer algal biomass began to increase. Pre-summer (period prior to the beginning of the clear water phase) dissolved inorganic phosphorus concentrations and summer phytoplankton composition presented similar interannual trends. However, the succession of phytoplankton structure during the reoligotrophication phase differed greatly from that during the eutrophication period, and a recent abnormal upward trend in algal densities is mainly the result of the development of large species that formerly were only common from late September until November. This community change, mainly triggered by filamentous (Mougeotia gracillima, Tribonema) or motile forms (Dinobryon sociale, Cryptophycea), seems to have been induced by the earlier and greater deepening of the P-depleted layer. In addition to milder summers, this massive development of larger forms seems to be favoured by four of their biological features: tolerance to warm temperatures, tolerance to low-light intensity (might exploit deeper layers where P is not yet limiting), shapes not only providing a large surface to volume ratio or motility (adaptation to low-nutrient concentrations), but increasing resistance to zooplankton grazing. This paradoxical trend, perhaps reinforced by the decline on roach Rutilus rutilus abundance (an opportunistic planktivore), is likely to remain until the P-depleted zone is extended below the layers that can be frequently resupplied in nutrients by hydrodynamic processes. [source] Disturbance frequency and functional identity mediate ecosystem processes in prairie streamsOIKOS, Issue 6 2009Katie N. Bertrand A major consequence of climate change will be the alteration of precipitation patterns and concomitant changes in the flood frequencies in streams. Species losses or introductions will accompany these changes, which necessitates understanding the interactions between altered disturbance regimes and consumer functional identity to predict dynamics of streams. We used experimental mesocosms and field enclosures to test the interactive effects of flood frequency and two fishes from distinct consumer groups (benthic grazers and water-column minnows) on recovery of stream ecosystem properties (algal form and biomass, invertebrate densities, metabolism and nutrient uptake rates). Our results generally suggest that periphyton communities under nutrient limitation are likely to recover more quickly when grazing and water-column minnows are present and these effects can diminish or reverse with time since the disturbance. We hypothesized that increased periphyton production and biomass was the result of increased nutrient turnover, but decreased light limitation and indirect effects on other trophic levels are alternative explanations. Recovery of stream ecosystem properties after a natural flood differed from mesocosms (e.g. lower algal biomass and no long algal filaments present) and species manipulations did not explain recovery of ecosystem properties; rather, ecosystem processes varied along a downstream gradient of increasing temperature and nutrient concentrations. Different results between field enclosures and experimental mesocosms are attributable to a number of factors including differences in algal and invertebrate communities in the natural stream and relatively short enclosure lengths (mean area=35.8 m2) compared with recirculating water in the experimental mesocosms. These differences may provide insight into conditions necessary to elicit a strong interaction between consumers and ecosystem properties. [source] Limnological changes in a sub-tropical shallow hypertrophic lake during its restoration: two years of a whole-lake experimentAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2001F. Scasso Abstract 1.,Lake Rodó is a turbid system, a condition attributed to algal biomass. The proximal source of the eutrophication was stormwater discharges from an ill-defined urban area. This paper describes an attempt to restore the water quality of Lake Rodó, the first time this has been done in Uruguay. In spring 1996 it was drained, sediments were removed and stream inputs were diverted. Groundwater was used to re-fill the lake. Due to its high nutrient concentration a re-circulation system was designed, pumping water from associated pools covered with free-floating plants. 2.,After the lake was refilled, the system was characterized by oxygen saturation or over-saturation, neutral to basic pH, and high phosphorus, nitrogen and silicate concentrations. Ratios of total nitrogen (TN):total phosphorus (TP) and chlorophyll a (Chl a):TP indicated that phosphorus was the primary limiting nutrient during the period of groundwater supply. Once groundwater pumping had ceased, there was a decrease in TN:TP and Chl a:TP ratios, suggesting N-limiting conditions prevailed in some periods. 3.,Before restoration, the phytoplankton community was dominated year-round by Planktothrix agardhii; since restoration the community has been more diverse. This change has favoured grazing by mesozooplankton, and the onset of clear-water phases in spring. 4.,Abundant populations of small omnivorous fish maintained a high predation pressure on zooplankton, restricting the abundance of large-bodied herbivores, which, in turn, allowed an increase in phytoplanton biomass and a decrease in water transparency. Based on this observation, together with the phosphorus concentration and the low abundance of filamentous cyanobacteria compared with previous studies, we suggest that top-down control has played a key role in increasing transparency in Lake Rodó. 5.,A nutrient reduction programme, by the mechanical harvest of floating plants, and a removal of small omnivorous fishes and stocking strictly with piscivores, could be key factors in the achievement of a stable clear-water phase. However, if blooms of Microcystis or other similar genera occur in summer, additional measures (e.g. reduction of the hydraulic residence time) will be needed to improve water transparency. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||||||||