The ecology of algae in the Moruya river,Australia

The standing crop of benthic and planktonic algae in the Moruya River, Australia, was, in general, low compared with values given for northern hemisphere rivers. Diatoms always accounted for more than 90% of the algae on the sediments with the most common species being typical of holarctic flora. The relative abundance of each of six predominant taxa was similar at the three sampling localities and did not show marked seasonal variation. However, Gomphonema spp. contributed a relatively greater number in the downstream area whereas Cocconeis placentula Ehr. was comparatively more abundant upstream. The highest standing crop (1.47 × 10⁶ cells/cm²) was found downstream and in the calmest part of the river between January and March, coincident with maximum water temperatures. A true phytoplankton succession comprising filamentous chlorophytes, Scenedesmus, Melosira varians Ag., Dactylococcopsis, Eudorina and Merismopedia was observed at the most downstream site during the spring and summer, with a maximum standing crop of 126.7 × 10³ cells/litre being attained in December. The gut of larval lampreys > 100 mm contained large numbers (44,000–525,000 cells) of algae. Scenedesmus and Dactylococcopsis occurred much more frequently in the gut than in either the sediment or water, but the reverse was true for filamentous algae.     

Seasonal succession of algae in a eutrophic stream in Southern England

The epipelic and epilithic algal communities in a small eutrophic stream situated in southern England expanded rapidly during March of both 1973 and 1974 primarily in response to changing light conditions. Although numbers varied greatly during the summer, these fluctuations were probably not due to nutrient, temperature or light conditions. High rates of disappearance of algae from the substrate were correlated with flooding, a deterioration of attachment characteristics and high metabolic rates. The episammic algal community consisted of only a few species, all of which showed maximum development during the summer. Although the well developed attachment mechanism and small size of the species undoubtedly aid in their ability to colonize sand grains, each species must be able to withstand frequent burial in the bottom deposits. Although temperature was probably an important factor controlling the number of epiphytes associated with Cladophora glomerata, light seemed to be of relatively less importance. Large numbers of isopods, amphipods and copepods occurred in the stream but their grazing seemed to have had little effect of the standing crop of the algae.     

Composition and dynamics of epilithic algae in a forest stream at Shillong (India)

The seasonal dynamics of epilithic algae in a third order pristine forest stream were analyzed over a period of 2 years. Stream water was slightly acidic and nutrient poor. Encrusting, filamentous flocs, and filaments were found. Algal standing crop was high (mean concentration of Chl a 16–43 mg m^–2) in spring. Filamentous algae contributed most to standing crop. Diatoms made up over 85% by number of the epilithon. Blue-greens were abundant upstream, and chlorophytes downstream. This shift was ascribed to greater light availability downstream. The community was more diverse during spring. Water current was the most important variable regulating epilithon structure. Total phosphorus (TP), orthophosphate (O-PO _inf4 ^su3– ), silica (Si⁴⁺), nitrate (NO _inf3 ^su– ) and conductance correlated negatively with flow rate. Green algae showed a positive correlation to phosphorus during low and stable flow. During rapid runoff, diatoms were the most resistant forms. Seasonal change in the epilithic community was mainly regulated by fluctuations in flow rate.     

人工滩涂湖泊滴水湖浮游藻类群落特征

于2009年3月—2010年2月逐月对中国最大人工滩涂湖泊——滴水湖的浮游藻类群落特征进行研究。利用CANOCO4.5软件对浮游藻类数据和环境因子数据进行典范对应分析(CCA),以揭示浮游藻类对生态环境的响应。结果表明:全年共检测到浮游藻类186种及变种,隶属于8门92属,其中绿藻门种类最多,其次是蓝藻门和硅藻门;主要优势种为小席藻、微小平裂藻、银灰平裂藻、不定微囊藻、弱细颤藻、啮蚀隐藻、四尾栅藻、扁圆卵形藻;藻类的年均丰度和年均生物量分别为(4552.29±4591.33)×104cells·L-1和8.15±6.63mg·L-1,藻类现存量各月份间差异极显著(P<0.01),但站点间差异不显著;多样性分析显示,藻类物种多样性较好;典范对应分析表明,水温、总氮等是影响滴水湖藻类群落结构的主要因素。     

Changes in the benthic fauna and flora after application of temephos to a stream on Mt. Tsukuba

A dose of 2 ppm of temephos in emulsifiable formulation was applied to a mountain stream to observe its effects on the zoobenthos and the subsequent changes in benthic algae. Most zoobenthos in the treated region drifted but there were slight differences among taxa. Ephemeroptera and Plecoptera disappeared but some Trichoptera and Diptera survived. Chironomids recolonized earlier than other invertebrates and reached a higher density level than before the treatment. A bloom of benthic algae occurred following the destruction of fauna. The increase in the standing crop of algae was accompanied by an increase in the number of species. Among these, Achnanthes lanceolata, Meridion circulare and Tetraspora gelatinosa were predominant. The end of the bloom began with the recovery of the zoobenthos population.     

The spatial and temporal distribution of an epiphytic algal community in a shallow prairie-parkland lake – Alberta, Canada

In Hastings Lake (longitudes 113°15' and 53°50'N), a shallow eutrophic lake, the spatial and temporal changes in species composition. diversitv. standing crops, and primary productivity of the epiphytic algae attached to Phragmnes australis and Scirpus validus were investigated in relation to the physico-chemical environment. Of the dominant species, cyanophycean algae ( Lyngbya diguetii and Calothrix sp.) developed best in the 25 cm region below the water surface, while the chlorophycean alga, Stigeoclonium nanum and the diatoms (Cocconeis placentula, Gomphonema parvulum and Rhoicosphenia curvata) did so in the 50 cm and 75 cm regions, respectively. Certain dominant species persisted throughout, interrupted by "shock periods" which created spring, summer, and autumn peaks. Species diversity indices increased with depth, and generally decreased spring through winter. Standing crop maxima occurred within the top 25 cm of the host stems, and showed spring and larger autumn peaks before declining to low. yet significant winter levels. Productivity, too, was greatest in the top 25 cm region, and again peaked in the spring and autumn. Cross incubation studies elucidated vertical and seasonal relationships among productivity, photosynthetic index, and efficiency, and productivity efficiency. An interplay of "sun and shade" adapted populations within the community was found. The epiphytic algae displayed but a muted seasonal response to physico-chemical fluctuations: however, there was an association with overall nutrient changes as determined by meq HCO₃⁻I⁻¹.     

Invertebrate drift lost to the sea during low flow conditions in a small coastal stream in Western Canada

The invertebrate drift leaving the lower end of a small coastal stream on the east coast of Vancouver Island was recorded during low flow conditions. 20,156 animals, weighing 0.96 g (dry weight), were collected in drift nets over a 5 day period in early summer. High and low drifting taxa are listed. Considerable daily variation in total captures occurred and was attributed to a few dominant taxa (primarily harpacticoid copepods, mites and chironomid larvae) exhibiting atypical drift patterns. 0.004% of the stream's invertebrate standing crop was estimated to be in the water column at any instant in time. The possible use of the outgoing animals as food for juvenile salmon in the estuary is discussed.     

Atyid shrimps (Decapoda: Atyidae) influence the spatial heterogeneity of algal communities over different scales in tropical montane streams, Puerto Rico

1. Atyid (Decapoda: Atyidae) shrimps influence the distribution of algal communities over different scales in tropical montane streams of Puerto Rico. Within pools of an atyid-dominated stream, atyid shrimps enhanced patchiness in algal communities along the depth gradient. Algal bands occurred in shallow pool margins where atyids did not forage (< 3 cm below water surface), with significantly greater standing crop, taxon richness, and structural complexity than deeper areas. In deeper water, atyids reduced small-scale patchiness in algal community composition and maintained a low-growing understorey turf dominated by sessile diatoms (Bacillariophyta) and, sometimes, closely cropped, filamentous blue-greens (Cyanophyta).
2. Among pools of the atyid-dominated stream, atyids interacted with light to determine algal patchiness between stream margins and deeper areas. In sunny pools, algal standing crop was 140-fold greater in pool margins than in deeper areas where atyids foraged. In shaded pools, however, standing crop in pool margins was only 5-fold greater than in deeper areas. Effects of light on algal standing crop were greater outside atyid foraging areas than within, indicating that shrimp grazing overrides the positive effects of light.
3. In contrast to the atyid-dominated stream, algal communities in an atyid-poor stream were characterized by a high biomass of loosely attached epipelic diatoms and no depth zonation. Interstream rock and shrimp transplant experiments indicated that atyids significantly reduced algal standing crop and altered community composition on rocks from atyid-poor streams within 24 h. Results support the hypothesis that atyid shrimps play a major role in determining observed interstream differences in algal communities.     

Atyid shrimps (Decapoda: Atyidae) influence the spatial heterogeneity of algal communities over different scales in tropical montane streams, Puerto Rico

1. Atyid (Decapoda: Atyidae) shrimps influence the distribution of algal communities over different scales in tropical montane streams of Puerto Rico. Within pools of an atyid-dominated stream, atyid shrimps enhanced patchiness in algal communities along the depth gradient. Algal bands occurred in shallow pool margins where atyids did not forage (< 3 cm below water surface), with significantly greater standing crop, taxon richness, and structural complexity than deeper areas. In deeper water, atyids reduced small-scale patchiness in algal community composition and maintained a low-growing understorey turf dominated by sessile diatoms (Bacillariophyta) and, sometimes, closely cropped, filamentous blue-greens (Cyanophyta).
2. Among pools of the atyid-dominated stream, atyids interacted with light to determine algal patchiness between stream margins and deeper areas. In sunny pools, algal standing crop was 140-fold greater in pool margins than in deeper areas where atyids foraged. In shaded pools, however, standing crop in pool margins was only 5-fold greater than in deeper areas. Effects of light on algal standing crop were greater outside atyid foraging areas than within, indicating that shrimp grazing overrides the positive effects of light.
3. In contrast to the atyid-dominated stream, algal communities in an atyid-poor stream were characterized by a high biomass of loosely attached epipelic diatoms and no depth zonation. Interstream rock and shrimp transplant experiments indicated that atyids significantly reduced algal standing crop and altered community composition on rocks from atyid-poor streams within 24 h. Results support the hypothesis that atyid shrimps play a major role in determining observed interstream differences in algal communities.     

Periphyton, chlorophyll a, and diatoms of the Middle Fork of the Salmon River, Idaho

Periphyton samples were collected at 15 sites in the Middle Fork of the Salmon River drainage basin, Idaho, USA to test certain principles of the River Continuum Concept (RCC) and to characterize the diatom communities. The standing crop of chlorophyll a increased from 2nd to 4th order streams, peaked in the 5th order stream, and declined in higher orders. These data support the RCC predictions except that peak values were reached somewhat earlier, in terms of stream order, because of the lack of shading in these streams. Also, downstream decreases were not completely attributable to increasing turbidity and decreasing benthic productivity, and may be partially related to discharge. The number of scraping invertebrates was positively correlated with the standing crop og periphyton (AFDM, not chlorophyll a); this, too, supports the predictions of the RCC. One hundred forty-five species of diatoms were identified and the system is characterized by an Achnanthes minutissima – Fragilaria pinnata - Navicula seminulum – Cocconeis placentula community.     

PERIODICITY OF EPIPELIC UNICELLULAR VOLVOCALES (CHLOROPHYCEAE) IN A SHALLOW ACID POOL1

The occurrence, periodicity and growth of twenty species of unicellular Volvocales on sediments in an acidic pool are described. Minimum populations were recorded in winter, but during the rest of the year standing crops fluctuated rapidly. The greatest species diversity and primary productivity occurred in late spring-early summer and in autumn, when maximum numbers of Chlamydomonas spp. and Chloromonas spp. increased exponentially on the sediments. The chlamydomonads were more numerous in the epipelon than other major algal components such as diatoms, euglenoids, bluegreen algae and desmids. Growth of the chlamydomonad population occurred after the period of maximum diatom standing crop. Evidence shows that rates of primary production were greater in late spring and late summer when species diversity and standing crop or apparent growth rates of unicellular Volvocales were high. Thus these algae which are normally neglected may be more important in primary productivity than previously believed since they grow during periods when larger algae are scarce. Analysis of the data using the multivariate technique of Reciprocal Averaging confirmed seasonal periodicity in this community of epipelic flagellates. It also identified species with distinctive ecological requirements. A relationship between the bicarbonate-alkalinity of the overlying water and the chlamydomonad population was demonstrated by ordination analysis.     

Pathways for algal recolonization in seasonally‐flowing streams

1. In semi‐arid climates, seasonally‐flowing streams provide most of the water required for human use, but knowledge of how water extraction affects ecological processes is limited. Predicted alterations in stream flows associated with the impacts of climate change further emphasize the need to understand these processes. Benthic algae are an important base for stream food webs, but we have little knowledge of how algae survive dry periods or respond to altered flow regimes. 2. We sampled 19 streams within the Grampians National Park, south‐eastern Australia and included four components: a survey of different drought refuges (e.g. permanent pools, dry biofilm on stones and dry leaf packs) and associated algal taxa; a survey of algal regrowth on stones after flows recommenced to determine which refuges contributed to regrowth; reciprocal transplant experiments to determine the relative importance of algal drift and regrowth from dry biofilm in recolonization; direct measurement of algal drift to determine taxonomic composition in relation to benthic assemblage composition. 3. Algae showed little specificity for drought refuges but did depend on them; no species were found that were not present in at least one of the perennial pool, dry biofilm or leaf pack refuges. Perennial pools were most closely correlated with the composition of algal assemblages once flows resumed, but the loss or gain of perennial pools that might arise from stream regulation is unlikely to affect the composition of algal regrowth. However, regulated streams were associated with strong increases in algal density in dry biofilm, including increased densities of Cyanobacteria. 4. A model for algal recolonization in seasonally‐flowing streams identified three pathways for algal recolonization (drift‐dependent, dry biofilm‐dependent and contributions from both), depending on whether streams are diatom‐dominated or dominated by filamentous algae. The model predicted the effects of changes to stream flow regimes on benthic algal recolonization and provides a basis for hypotheses testable in streams elsewhere.     

Concentration and distribution of chlorophyll in fertilized plots in a Massachusetts salt marsh

The amount of algal chlorophyll on the mud surface of a salt marsh was not affected directly by additions of urea or sewage sludge fertilizer but was proportional to light reaching the surface. Fertilization affected the algae by increasing the standing crop of grass and theregy reducing the light underneath. Vertical distribution of total chlorophyll depended on the species and biomass of grass present. Algal chlorophyll was concentrated at the mud surface and horizontally was very patchy. Locally the quantity exceeded the amount found in other productive marine ecosystems.     

Interactions among nutrients, algae and invertebrates in a New Zealand mountain stream

SUMMARY. 1. Colonization of nutrient-diffusing substrata by periphyton and invertebrates was investigated at forested and open sites in a small, mountain stream and a spring in the South Island of New Zealand.
2. Substrata had colonization surfaces made from 100μm mesh plankton netting that enabled algal assemblages to be removed intact for scanning electron microscopy. They also allowed small volumes of solvent to be used for the extraction of photosynthetic pigments.
3. At all sites, periphyton assemblages were dominated by species of Achnanthes, Cocconeis and Gomphonema , and except in the forest in winter, periphyton biomass was always greater on enriched (N + P added) than control substrata.
4. Invertebrates colonizing diffusion substrata were principally larval Chironomidae (Orthocladiinac). No larvae were present in winter, but in three spring and summer trials mean larval densities were higher on nutrient-enriched than control substrata at all sites.
5. The inclusion of an insecticide Malathion in diffusion substrata, reduced insect colonization at open and forested sites. After 28 days, no concurrent increases in algal pigment concentration were observed on nutrienl-enriched or control substrata at the forested site. However, pigment concentrations were higher on substrata incorporating Malathion at the open site suggesting that algal standing crop was depressed by the activities of grazers.     

Seasonal Changes in the Quantity and Nitrogen Content of Coarse Detritus in a Southern Ontario Stream

Seasonal changes in standing crop of coarse, benthic detritus at five locations across a second-order stream were studied between May 1971 and May 1972. Standing crop near the banks varied seasonally with highest quantities in the autumn and winter, whereas near midstream seasonal changes in standing crop were negligible. Mean annual standing crop was 747 g/m² (ash-free dry weight) near the banks and 225 g/m² (AFDW) at midstream. Deposition experiments showed that standing crops of detritus came to equilibrium in 2–3 days at midstream and in about one week near the banks. Nitrogen content of coarse detritus, which ranged between 0.65 and 3.51% (AFDW), did not vary seasonally but was significantly greater near the banks than at midstream.     

Grazing catfish,fishing birds,and attached algae in a Panamanian stream

Synopsis In streams where algivorous fishes abound, striking variation of attached algae often develops along depth gradients, with bands of high standing crops in shallow water (<20 cm) and sparse standing crops on deeper substrates. Experimental results from a stream in central Panama support the hypothesis that vertical variation in algal standing crops arises when grazing fishes avoid predators in shallow water by forgoing food resources that accumulate there. When 38 rocks bearing algae in a stream in central Panama were transferred from shallow (<20 cm) to deeper (>20 cm) water, algae were rapidly consumed by grazing catfish. Catfish were removed from three stream pools and left in place in three control pools. Ten days after catfish removal, algal standing crops in deep and shallow areas of removal pools were similar, while algal standing crops were higher in shallow than in deep areas of control pools. Catfish were exposed to fishing birds in open-topped enclosures. In one of three series of these pens, most catfish in shallow pens (10 and 20 cm) disappeared after 14 days, while catfish in deeper pens (30 and 50 cm) did not. Other groups of catfish which were caged 8 days showed differences in behavior depending on whether they had been fed or starved. After their release into their home pool, starved catfish spent more time feeding than did fed catfish. Despite their apparently increased hunger levels, starved catfish did not venture into shallow water to obtain algae. These results support the view that predator induced avoidance by grazers of certain areas can produce spatial pattern in the flora of flowing water communities.     

COLONIZATION AND STANDING CROPS OF EPILITHIC ALGAE IN THE SUSQUEHANNA RIVER,PENNSYLVANIA1

A SCUBA diver, using a bar-clamp sampler, collected quantitative epilithic algae samples from artificial substrates (slate and acrylic plates) and river stones at two stations on the Susquehanna River bottom in 1974. At Falls, Pennsylvania, algal colonization on monthly plates (submerged for ca. 30 day periods) was most rapid between September and October. In winter, when algal density on cumulative plates (submerged 2–13 mo) and on stones present in the river peaked at 18,100 and 21,900 units/ mm², respectively, colonization of clean monthly plates nearly ceased. Similar colonization patterns were observed in a portion of the river polluted by coal mine drainages (SSES), but expansion of the algae population at SSES was inhibited by iron in the effluents, and densities never exceeded 2,400 units/mm² on stones or plates. Diatoms composed 95% of the overall standing crop at Falls and 65% at SSES.     

Semiarid grassland responses to short-term variation in water availability

Standing crop and species composition in semiarid grassland are linked to long-term patterns of water availability, but grasslands are characterized by large single-season variability in rainfall. We tested whether a single season of altered water availability influenced the proportions of grasses and shrubs in a semiarid grassland near the northern edge of the North American Great Plains. We studied stands of the clonal shrub snowberry (Symphoricarpos occidentalis) and adjacent grassland dominated by the native grasses Stipa spartea and Bouteloua gracilis. Rain was excluded and water supplied in amounts corresponding to years of low, medium, and high rainfall, producing a 2 − 4-fold range in monthly precipitation among water supply treatments. There were ten replicate plots of each water treatment in both snowberry stands and grassland. Grass standing crop increased significantly with water availability in grassland but not inside snowberry stands. Total standing crop and shrub stem density increased significantly with water supply, averaged across both communities. In contrast, water had no effect on shrub standing crop or light penetration. In summary, our finding that water has significant effects on a subset of components of grassland vegetation is consistent with long-term, correlational studies, but we also found that a single season of altered water supply had no effect on other important aspects of the ecosystem. This revised version was published online in June 2006 with corrections to the Cover Date.     

钛酸盐纳米材料介导下微藻净化生活污水的效应

为研究钛酸盐纳米材料(TNTs)介导下微藻对生活污水的处理效应,设置不同的TNTs添加方式与5种微藻协同处理生活污水,比较不同藻种和处理方式下叶绿素的光化学效率和光合色素含量,筛选优势藻种和高效处理方式。结果表明, TNTs能够显著加强微藻对生活污水的处理效果。在添加TNTs后, 5种微藻细胞均出现团聚现象,叶绿素a和类胡萝卜素的含量均有所上升。微藻对生活污水的处理效果均在TNTs介导2d后最好,斜生四链藻(Tetradesmus obliquus)对COD和NH₃-N的去除率最高,达到95.00%和88.62%;普通小球藻(Chlorella vulgaris)对TN的去除率最高,达到95.00%;四尾栅藻(Scenedesmus quadricauda)对TP的去除率最高,达到79.43%。与微藻单独处理相比, TNTs添加显著提升了污染物的降解率(>10%)和微藻除污率(>5%)。TNTs介导在微藻深度处理生活污水中具有一定的应用前景。     

Structure and grazing of stone surface organic layers in some acid streams of southern England

SUMMARY.

• 1 Stone surface organic layers were investigated at five sites on small, acid streams in the Ashdown Forest, southern England. Sites differed in stream water pH (means 4.3–6.6) and some other physicochemical features.
• 2 Organic layers at the stream bed surface differed between sites in structure and in the amount of organic carbon present. Algae were abundant at the sites with higher conductivity and pH, iron bacteria (mainly Leptothrix sp.) predominated in the iron-rich Broadstone stream, whereas the surface layer at the most acid site was predominantly a rather structure less organic film with few living organisms.
• 3 Amounts of organic carbon on stones buried within the stream bed for 3 months were almost identical at all sites. When viewed with the scanning electron microscope (SEM), organic layers on buried stones were rather structure less with some amorphous, floceulent material. The paucity of microflora suggests that these layers may have been formed primarily by abiotic mechanisms.
• 4 X-ray microanalysis of organic layers indicated that complexes of organic matter with the metals iron, aluminium and manganese were present.
• 5 Laboratory experiments with seven species of invertebrates showed that all were able to remove and at least partially ingest organic layers and underlying sandstone. The weight of material removed was highest on microbially impoverished layers from the most acid site, and was substantially lower where algae were abundant. 6. The role of stone surface organic layers in stream systems is discussed. They may be important sites of dissolved organic matter (DOM) uptake and transfer to the benthos. A major impact of acidity on running water could be through its effect on the structure and function of organic layers.