bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial activity and phosphorus dynamics in eutrophic lake sediments enriched with Microcystis colonies
Authors: BRUNBERG ANNA‐KRISTINA 
Published: May 2006

SUMMARY1. Sediments from hypereutrophic Lake Vallentunasjön were enriched with Microcystis colonies from the lake water, thereby simulating the conditions after the autumn sedimentation. Release of phosphorus to the overlying lake water was followed during 2–3 weeks in the laboratory. X‐ray microanalysis of individual Microcystis and bacterial cells, and chemical phosphorus fractionation, were used to assess the phosphorus pool size in different fractions of the sediment.2. Benthic Microcystis colonies, most of these having survived within the sediment for 1 year or more, were less susceptible to decomposition, and the specific growth rate of bacteria in their mucilage was lower than for other sediment bacteria.3. Pelagic Microcystis colonies from late August were resistant to decomposition, when placed on the sediments. When Microcystis colonies from a declining pelagic population in October were added to the sediments, however, a substantial fraction of these colonies was decomposed. The specific growth rate of mucilage bacteria was five times higher than for other sediment bacteria.4. Release of molybdate‐reactive phosphorus to the overlying lake water was larger from sediment cores enriched with Microcystis colonies than from control cores. Chemical phosphorus fractionation showed a decrease in organic‐bound phosphorus (residual P).5. X‐ray microanalysis showed that the phosphorus bound in Microcystis cells decreased by ‐0.300 mg g−1 DW in the October experiment, due both to a decrease in biomass (i.e. mineralization) and to a decrease in phosphorus content in the remaining cells. Heterotrophic bacteria increased their cellular concentration of phosphorus. The net release of phosphorus from the Microcystis and bacterial pools corresponded to 74% of the decrease of organic‐bound phosphorus in the chemical phosphorus fractionation, and to 65% of the decrease of total phosphorus in the upper 0–1 cm of the sediment.6. Benthic bacteria and cyanobacteria may thus contribute significantly to changes in phosphorus content and turnover of the sediment by changes in their biomass, turnover rate and cellular phosphorus content.
Seed dispersal, germination and seedling growth of six helophyte species in relation to water‐level zonation
Authors: COOPS HUGO , VAN DER VELDE GERARD 
Published: May 2006

SUMMARY1. Seed dispersal, germination, and seedling growth characteristics of six helophyte species. Iris pseudacorus, Phalaris arundinacea, Phragmites australis, Typha angustifolia, T. latifolia and Scirpus lacustris, were investigated in relation to their water‐level zonation.2. The experiments demonstrated a large variation in these characteristics between the species.3. Propagule floating capacities range from < 1 h (S. lacustris) to > 1000 h (I. pseudacorus).4. Seed germination in a water‐level gradient revealed two groups with respect to germination percentage ‐ exposed soil species (I. pseudacorus, Phalaris arundinacea, Phragmites australis) and submerged soil species (T. angustifolia, T. latifolia).5. There were two contrasting types of seedling growth response to submergence and exposure: one group of species formed longest leaves under exposed conditions (Phalaris arundinacea, Phragmites australis, I. pseudacorus), and the other under submerged conditions (S. lacustris, T. latifolia, T. angustifolia).6. The results suggest that early life‐history characteristics of the species relate to their locations in the riparian zonation: Phalaris arundinacea and Iris pseudacorus at the higher end, Phragmites australis intermediate, and Typha spp. and Scirpus lacustris at the lower end. Species occurring at lower locations show adaptations to (periodical) flooding of the soil (submersed germination and growth), while those from higher locations require prolonged exposed soil conditions to germinate and to survive the establishment stage.
The reaction time of leech and triclad species to crushed prey and the significance of this for their coexistence in British lakes
Authors: SEABY R.M.H. , MARTIN A.J. , YOUNG J.O. 
Published: May 2006

SUMMARY1. Three species of leeches, Erpobdella octoculata, Glossiphonia complanata and Helobdella stagnalis, and four species of triclads, Polycelis nigra, P. tennis, Dugesia polychroa and Dendrocoelum lacteum, commonly coexist on stony shores in productive British lakes. All species are food limited and there is much overlap in their diet. For both leech and triclad communities, coexistence of species is through the occurrence of food refuges. Leeches are more successful than triclads at capturing live prey, whereas both groups feed on damaged prey, comprising incapacitated, live or dead animals that are leaking body fluids. If triclads are better than leeches at exploiting damaged prey, this could be a mechanism for their coexistence.2. Laboratory experiments investigated the comparative speeds at which leeches and triclads responded to crushed prey. Young and adult predators were offered a crushed specimen of the oligochaete Tubifex tubifex, the snail Lymnaea peregra, the crustacean Asellus aquaticus or the chironomid Chironomus sp., and their reaction times recorded. These four prey groups constitute the main diet of the predators in the field. Only D. polychroa and D. lacteum showed a significantly different reaction time between young and adults to crushed prey, and the reason for this is unclear. All predators, except H. stagnalis and D. polychroa, showed a difference in reaction time to the four types of prey, presumably a consequence of differences in both the ‘quality’ and ‘concentration’ of the different prey fluids, and there were some differences between predators in their speed of reaction to the same prey type. The following sequence, from fastest to slowest, in general reaction time to prey was obtained: E. octoculata, D. polychroa, P. tenuis, D. lacteum, P. nigra, H. stagnalis and G. complanata.3. The location of the damaged food by the predators can be explained partly in terms of their foraging behaviour, with E. octoculata, D, polychroa and P. tenuis exhibiting a more seek‐out strategy than other species which have a more sit‐and‐wait behaviour, and partly on the level of sophistication of their chemosensory system used to detect leaked prey fluids. This system is highly developed in triclad species but poorly developed in leeches.4. In a second type of experiment in which prey, L. peregra, A. aquaticus or Chironomus sp., were offered at different time intervals after crushing to H, stagnalis and P. tenuis, few predators fed on food crushed for 24 h or longer, although a few leeches fed on Chironomus crushed for up to 72 h.5. It is concluded that coexistence of leech and triclad species on stony shores in lakes is assisted by partitioning of food on a damaged or live basis.
Vertical zonation and production rates of epiphytic algae on Phragmites australis
Authors: MÜLLER UTE 
Published: May 2006

SUMMARY1. The vertical distribution of chlorophyll in epiphyton on Phragmites australis showed a peak in the middle sections of the submerged parts. Just below the water surface and above the sediment, chlorophyll concentrations were much less.2. During winter and early spring, loosely attached diatoms were predominant just below the water surface and on the middle sections of the Phragmites plants. Near the bottom, adnate diatoms, parenchymatous thalli of chlorophytes and cyanobacteria were abundant.3. At high photosynthetic active radiation (PAR) during May, filamentous species of Ulpthricophyceae and Zygophyceae developed dense populations on the middle sections of the stems.4. Primary production rate was proportional to chlorophyll concentration although production maxima were recorded above the biomass maxima.5. Where illumination was low, the chlorophyll‐specific rate of photosynthesis (PB rate) decreased proportionally with the vertical decrease of PAR in the littoral zone, independent of the chlorophyll concentration on the stems.6. When illumination was high, the PB rate decreased as biomass increased, and was independent of surface radiation.7. The dependence of primary production rate on chlorophyll concentration produced a saturation curve with a maximum production at 4.6 μgC cm−2h−1.
Factors controlling hyporheic respiration in a desert stream
Authors: JONES J.B. 
Published: May 2006

SUMMARY1. Experimental manipulations were performed to determine the biological, chemical and physical attributes that govern sediment respiration in the hyporheic zone of Sycamore Creek, a Sonoran Desert stream.2. Hyporheic respiration per unit volume of sediment was inversely related to diameter of sediment particles, indicating that respiration is affected by availability of substrate for microbial colonization (i.e. sediment surfaces). Respiration rate per unit surface area on sediments was positively correlated with particle diameter, indicating greater metabolic activity of microbes on larger sediments.3. Hyporheic respiration was more than twice as high in water collected from the surface flow than from subsurface flow. Further, hyporheic respiration was highest immediately following exposure of sediments to surface water and declined over time, presumably due to exhaustion of labile organic matter.4. Microbial activity was stimulated by addition of algal leachate; however, amendments of leaf leachate had little effect. Respiration was also elevated with dextrose and leucine amendments, but not with inorganic nitrogen additions, indicating hyporheic respiration is carbon limited.5. Water from the stream surface is probably enriched in labile organic matter derived from algae and stimulates respiration at points of hydrologic downwelling where surface water enters hyporheic sediments. The physical structure of sediments further affects metabolism by affecting the area available for microbial attachment.
Food quality of gelatinous colonial chlorophytes to the freshwater zooplankters Daphnia pulicaria and Diaptomus oregonensis
Authors: STUTZMAN PAUL 
Published: May 2006

SUMMARY1. The capacities of the gelatinous colonial chlorophytes Pandorina morum and Sphaerocystis schroeteri to sustain survival and reproduction in the calanoid copepod Diaptomus oregonensis and the cladoceran Daphnia pulicaria were evaluated quantitatively. Control groups of animals were fed equivalent biovolumes of Cryptomonas reflexa, which is known to favour high levels of survival and reproduction.2. On a biovolume basis, all three algae sustained equal survival of Daphnia, but Cryptomonas and Pandorina allowed longer survival of Diaptomus than did Sphaerocystis.3. Both animals produced significantly more offspring clutch−1 and more total offspring on Cryptomonas than on either chlorophyte. Both animals produced more total offspring on Pandorina than on Sphaerocystis.4. The interclutch duration for Daphnia was significantly longer on Pandorina than the other algae, and the interclutch duration for Diaptomus was longer on Pandorina than on Cryptomonas.5. Daphnia utilized the gelatinous chlorophytes more effectively than did Diaptomus.
Phytoplankton nutrient deficiency in lakes of the McMurdo dry valleys, Antarctica
Authors: PRISCU JOHN C. 
Published: May 2006

SUMMARY1. The influence of inorganic nitrogen and phosphorus enrichment on phytoplankton photosynthesis was investigated in Lakes Bonney (east and west lobes), Hoare, Fryxell and Vanda, which lie in the ablation valleys adjacent to McMurdo Sound, Antarctica. Bioassay experiments were conducted during the austral summer on phytoplankton populations just beneath the permanent ice cover in all lakes and on populations forming deep‐chlorophyll maxima in the east and west lobes of Lake Bonney.2. Phytoplankton photosynthesis in surface and mid‐depth (13 m) samples from both lobes of Lake Bonney were stimulated significantly (P < 0.01) by phosphorus enrichment (2 μM) with further stimulation by simultaneous phosphorus plus NH4+ (20 μM) enrichment. Similar trends were observed in deeper waters (18 m) from the east lobe of Lake Bonney, although they were not statistically significant at P < 0.05. Photosynthesis in this lake was never enhanced by the addition of 20 μM NH4+ alone. Simultaneous addition of phosphorus plus nitrogen stimulated photosynthesis significantly (P < 0.01) in both Lake Hoare and Lake Fryxell. No nutrient response occurred in Lake Vanda, where activity in nutrient‐enriched samples was below unamended controls; results from Lake Vanda are suspect owing to excessively long sample storage in the field resulting from logistic constraints.3. Ambient dissolved inorganic nitrogen (DIN) (NH4++ NO2−+ NO3−): soluble reactive phosphorus (SRP) ratios partially support results from bioassay experiments indicating strong phosphorus deficiency in Lake Bonney and nitrogen deficiency in Lakes Hoare and Fryxell. DIN : SRP ratios also imply phosphorus deficiency in Lake Vanda, although not as strong as in Lake Bonney. Particulate carbon (PC): particulate nitrogen (PN) ratios all exceed published ratios for balanced phytoplankton growth, indicative of nitrogen deficiency.4. Vertical nutrient profiles in concert with low advective flux, indicate that new (sensu Dugdale & Goering, 1967) phytoplankton production in these lakes is supported by upward diffusion of nutrients from deep nutrient pools. This contention was tested by computing upward DIN : SRP flux ratios across horizontal planes located immediately beneath each chlorophyll maximum and about 2 m beneath the ice (to examine flux to the phytoplankton immediately below the ice cover). These flux ratios further corroborated nutrient bioassay results and bulk DIN : SRP ratios indicating phosphorus deficiency in Lakes Bonney and Vanda and potential nitrogen deficiency in Lakes Hoare and Fryxell.5. Neither biochemical reactions nor physical processes appear to be responsible for differences in nutrient deficiency among the study lakes. The differences may instead be related to conditions which existed before or during the evolution of the lakes.
Secondary analysis of relationships between pelagic invertebrate predators and phytoplankton abundance and water clarity
Authors: FRANCE R. , YAN N. , OLESIUK P. , NERO R. , DEL GIORGIO P. A. , KELLER W. 
Published: May 2006

SUMMARY1. Several models predict that elevated levels of zooplanktivory will promote increases in phytoplankton abundance and corresponding decreases in water clarity. Because estimates of zooplanktivorous fish abundance are logistically difficult, empirical testing of these models has been limited. Our goal was to examine whether the impact of mysids and larval chaoborids on their herbivorous zooplankton prey is either transmitted to, or becomes uncoupled at, the phytoplankton and water quality levels.2. A secondary analysis of ninety‐eight correlation coefficients from twenty‐five published and unpublished data sets indicated that on average 71% of all correlations agreed with the predictions of top‐down trophic interactions, although most did so with only marginal or weak support.3. Potential confounding by variable nutrient concentrations, alternative determinants of water clarity and omnivory may complicate simple interpretation of the influence of pelagic invertebrates on zooplankton in lakes.
The validation of diatom‐phosphorus transfer functions: an example from Mondsee, Austria
Authors: BENNION HELEN , WUNSAM SYBILLE , SCHMIDT ROLAND 
Published: May 2006

SUMMARY1. A diatom‐phosphorus weighted averaging (WA) transfer function, derived from a training set of currently oligotrophic to mesotrophic European Alpine lakes, was applied to a high‐resolution sediment core with annual laminae from Mondsee, an Austrian pre‐alpine lake, in order to reconstruct the eurrophication history of the lake.2. The water chemistry records of total phosphorus (TP) available for Mondsee were compared with the diatom‐inferred TP from the model for the period 1975–93. The trend in TP values as inferred by the model paralleled the monitored trend in TP values closely, with matching peaks in 1979/80, a decrease in values from the early 1980s, a second smaller peak in 1986/7, and a further reduction in concentrations in the last 6 years.3. However, there was a clear mismatch between the actual timing of the major TP peak, with the water chemistry records reporting its occurrence in 1979, and the diatom model indicating a small peak in 1980 and the highest concentrations in 1982. This can be attributed to the uncertainty of the sediment chronology for this section of the core, and possibly to the inconsistency between the core resolution and the resolution of the diatom model.4. In terms of the actual concentrations of TP inferred by the model, they compared reasonably well with the measured data, although the model tends to underestimate for the lower core section owing largely to poor diatom assemblage analogues. In the upper part of the core, the diatom‐inferred TP values were in extremely close agreement with the monitored chemical data.5. This validation study indicates that diatom‐phosphorus transfer functions are robust and are able reliably to infer past‐TP concentrations from fossil diatom assemblages in sediment cores. Despite the natural intra‐ and interannual variability in diatom assemblages and epilimnetic water chemistry, the technique can provide accurate estimates of TP with an annual resolution. The model can be applied to selected sites with suitable sediment records to reconstruct lake TP histories, thus providing a pragmatic management tool for addressing lake eutrophication problems.
Disturbance and the community structure of stream invertebrates: patch‐specific effects and the role of refugia
Authors: PALMER MARGARET A. , RENSBURGER PETER A , BOTTS P. SILVER , HAKENKAMP CHRISTINE C. , REID JANET W. 
Published: May 2006

SUMMARY1. We have previously shown that the impact of spates on stream invertebrates may differ among patches separated by distances of metres or less. Here we analyse the species‐specific flood responses of larval chironomids and adult and near mature copepods living in different patch types. Four patch types (with eight replicates of each) were compared: the sandy mid‐channel, fine sediments around dams, coarse sediments around dams, and dam debris. Additionally, since some fine sediment patches had been shown previously to act as flow refugia while others did not, we also examined species‐specific responses in refugium vs. non‐refugium fine sediment patches. Detrended correspondence analysis was used to test for changes in assemblage structure (species composition and relative abundance).2. Species richness was not altered in a predictable manner by floods; the least stable patch types (mid‐channel and coarse patches) did not necessarily show reduced species richness during the spate.3. As indicated by the spread of DCA ordination scores, there was generally a high degree of overlap in the species composition among the four patch types. Nevertheless, copepod species composition and relative abundance were more similar among patch types during the spate than pre‐spate. Spates may induce a re‐distribution of copepod species among the patch types. Chironomid species composition and relative abundance were no more similar among patch types during the spate than pre‐ or post‐spate.4. For both chironomids and copepods, species composition and relative abundance (as assessed by DCA ordination scores) in refugium patches changed more in response to the spate than in the non‐refugium patches. An influx of individuals from just a few species for each group was responsible for the change in assemblage structure. Thus, despite the fact that our past work has shown that refugia may confer enhanced resistance and resilience of copepod and chironomid assemblages in terms of total faunal abundances, the present work suggests that resistance and resilience of the species composition of the community apparently are no greater in refugium patches than in non‐refugium patches.
Changes in a deep lake following sewage diversion – a challenge to the orthodoxy of external phosphorus control as a restoration strategy?
Authors: CARVALHO LAURENCE , BEKLIOGLU MERYEM , MOSS BRIAN 
Published: May 2006

SUMMARY1. The restoration of deep lakes has traditionally focused on reducing the external phosphorus loading.2. Following the diversion of sewage effluent, that led to marked reductions in nutrient concentrations in its main inflow, Rostherne Mere has shown no reduction in phosphorus or chlorophyll a concentrations. A shallow lake upstream (Little Mere), however, has shown a marked response to effluent diversion.3. Nutrient budgets for Rostherne Mere reveal that sewage effluent was by far the most significant external source of total phosphorus and that diffuse drainage from the catchment was the most significant external source of dissolved inorganic nitrogen. Phosphorus loads from groundwater and a bird roost were insignificant. Internal sources of phosphorus were, however, considerable and were largely responsible for the observed delay in recovery.4. Phosphorus limitation of phytoplankton biomass may never be attainable because of substantial internal and diffuse sources of phosphorus, combined with a long retention time. Nitrogen is likely to be more important in limiting phytoplankton biomass. Control of diffuse nitrogen sources may therefore be more effective in the restoration of the deeper lakes of this region.
The construction of a diatom‐based chlorophyll a transfer function and its application at three lakes on Signy Island (maritime Antarctic) subject to differing degrees of nutrient enrichment
Authors: JONES V.J. , JUGGINS S. 
Published: May 2006

SUMMARY1. Canonical correspondence analysis of a diatom and water chemistry dataset from fifty‐nine maritime Antarctic lakes situated on Signy and Livingston Islands showed that nutrients and functions of nutrients (NH4+, chlorophyll a) accounted for a significant fraction of the variance in the diatom data.2. Weighted averaging regression was used to construct a diatom‐based transfer function for inferring chlorophyll a concentrations from sediment core diatom assemblages.3. The transfer function was applied to 210Pb‐dated sediment cores from three lakes (Moss, Sombre and Heywood) receiving different levels of nutrient input from fur seal populations, i.e. low, medium and high, respectively.4. Moss Lake showed relatively stable reconstructed chlorophyll a values, and no evidence of recent eutrophication, agreeing with measured chlorophyll a concentrations at the site.5. Changes in diatom assemblages and results of chlorophyll a reconstructions at Sombre Lake suggested that nutrient enrichment had occurred, which could be clearly linked to fluctuations in the measured water chemistry over the last 10–14 years.6. Despite recorded increases in recent nutrient inputs there was no apparent diatom response at Heywood Lake.