A portable pump sampler for lotic periphyton

A sampling technique for collecting lotic periphyton on sedimentary substrates using a peristaltic pump is described. Quantitative samples of periphyton standing crop and colonization rate are collected by the same procedure. The technique eliminates human disturbance problems associated with floating artificial samplers by establishing permanent sampling sites directly on submerged substances.     

Initial colonization of periphyton on natural and artificial apices of Myriophyllum heterophyllum Michx

SUMMARY. 1. The initial colonization of periphyton on natural and artificial apices of Myriophyllum heterophyllum Michx was compared at three depths in the littoral zone of Lake Winnipesaukee, a soft-water New England lake. After a 1 week incubation period, the apices were sampled and the periphyton was removed and counted as numbers of periphyton organisms per centimetre of stem.
2. Initial colonization on both substrates was characterized by diatoms, particularly small single-celled species, throughout the spring and summer. Blue-green and green algae occurred in low numbers on both substrates during mid-summer, usually forming a greater percentage of the population of the natural apices. Blooms of the green alga Zygnema sp. dominated both substrates in late August.
3. Community composition generally did not differ significantly by depth or substrate on the natural and artificial apices: however, total abundance was significantly greater on the natural apices. M. heterophyllum appeared to serve as a neutral substrate in terms of community composition but had a positive effect on the total numbers of algae.     

Monitoring river periphyton with artificial benthic substrates

The objective of this research was to identify the materials and methods necessary to study the attached algal community on a river bottom in deep water. The study site was the Susquehanna River near Falls, Pennsylvania. Artificial substrates of smooth glass, frosted glass, Vermont slate, sandy slate (flagstone) and acrylic plate were placed on the stream bottom in detritus free sample holders by scuba divers. Both monthly and long-term cumulative samples were collected from the plates employing scuba and a Bar-Clamp sampler. River stones (natural substrates) were collected for comparison. Samples were analyzed in a Palmer Cell under a Bausch and Lomb research microscope. Diatoms were the most important colonizers of river stones, with the genera Nitzschia and Navicula most abundant. Highest periphyton densities occurred on natural substrates in winter with a maximum of 2.2 × 10⁴ units/ mm². Artificial substrates with one month exposure periods accumulated maximum periphyton density from May through October with relatively low densities in winter. Cumulative artificial substrates were most like river stones in patterns of colonization. Frosted acrylic is recommended for future studies employing benthic artificial periphyton substrates.This study was partially supported by the Pennsylvania Power and Light Company     

Effects of copper on periphyton communities assessed in situ using chemical-diffusing substrates

Chemical-diffusing substrates were designed to allow delivery of toxicants to mature periphyton communities under natural conditions without contaminating the surrounding environment. Artificial stream validation studies were conducted in which the effects of substrate-released copper (Cu) on periphyton communities were compared to those generated in a more conventional manner (via water column additions). Effects of copper on the following community parameters were assessed: total community biomass (measured as ash-free dry mass), relative chlorophyll a (chl a and adenosine triphosphate contents, and relative biomass of heterotrophic bacteria. Exposure of more laboratory periphyton communities to substrate-released Cu generated dose-response relationships and recovery models that were indistinguishable from those generated by the conventional route of exposure. The results of this study demonstrate the utility of chemical-diffusing substrates in field validations of laboratory toxicity tests and in investigations of the effects of stress history on periphyton tolerance to toxicants. This revised version was published online in September 2006 with corrections to the Cover Date.     

The possibilities for control of two‐spotted spider mite tetranychus urticae on field‐grown strawberries in the UK by predatory mites

Numerous field trials have been undertaken in order to obtain a deeper understanding of the behavior (persistence, dispersion, etc.) of Bacillus thuringiensis serovar. israelensis (B.t.i.) formulations when treating rivers or streams for blackfly control. After an extensive sampling of water and natural substrates (periphyton, sediments, moss), freezing is a useful procedure to prevent enzymatic deterioration or bacterial growth in samples before bioassays are to be performed. Using Aedes triseriatus neonate larvae, we quantified the effect on potency of freezing and thawing of B.t.i. suspensions at operational field concentrations. In addition, as samples varied in their content of natural substrates we tested the hypothesis that the presence of such suspended solids affected the mortality response of larvae. Our results showed that these parameters are of significant importance and should be accounted for when comparing bioassays performed on previously frozen or turbid samples.     

Phosphorus Availability Alters the Effects of Silver Nanoparticles on Periphyton Growth and Stoichiometry

Exposure to silver nanoparticles (AgNPs) may alter the structure and function of freshwater ecosystems. However, there remains a paucity of studies investigating the effects of AgNP exposure on freshwater communities in the natural environment where interactions with the ambient environment may modify AgNP toxicity. We used nutrient diffusing substrates to determine the interactive effects of AgNP exposure and phosphorus (P) enrichment on natural assemblages of periphyton in three Canadian Shield lakes. The lakes were all phosphorus poor and spanned a gradient of dissolved organic carbon availability. Ag slowly accumulated in the exposed periphyton, which decreased periphyton carbon and chlorophyll a content and increased periphyton C:P and N:P in the carbon rich lakes. We found significant interactions between AgNP and P treatments on periphyton carbon, autotroph standing crop and periphyton stoichiometry in the carbon poor lake such that P enhanced the negative effects of AgNPs on chlorophyll a and lessened the impact of AgNP exposure on periphyton stoichiometry. Our results contrast with those of other studies demonstrating that P addition decreases metal toxicity for phytoplankton, suggesting that benthic and pelagic primary producers may react differently to AgNP exposure and highlighting the importance of in situ assays when assessing potential effects of AgNPs in fresh waters.     

Responses of stream algae to grazing minnows and nutrients: a field test for interactions

Summary Previous studies have shown that an algivorous grazing minnow (Campostoma anomalum) is the major herbivore in Brier Creek, a hardwater stream in south central Oklahoma. In summer and autumn schools of Campostoma virtually eliminate algae from substrate surfaces in deeper areas of some pools. The pool-to-pool distributions of algae and Campostoma reported for this stream could occur if nutrient limitation permits grazing by Campostoma to outrun algal growth. To test this hypothesis, mesh pens were built to exclude Campostoma from substrates in each of four typical Campostoma pools. N+P+K lawn fertilizer was added daily to two of the four pools; the other two, which received no fertilizer additions and which were not visibly affected by fertilizer transported downstream from the pools enriched with nutrients, served as controls. Algae accumulated rapidly on natural substrates and on unglazed ceramic tiles in grazer-exclusion pens in pools receiving N+P+K additions and more slowly in pens in both control pools. Periphyton biomass on grazed substrates in all four pools remained low throughout the experiment. Hence, Campostoma at normal densities were able to outrun algal growth even when nutrients were added. Eleven days after the experiment started, I determined biomass, biomass-specific net primary productivity, and areal net primary productivity of periphyton on substrates exposed to all combinations of grazer (+,0) and nutrient (+,0) treatments. Grazing increased biomass-specific primary productivity, prevented accumulation of biomass, and decreased areal primary productivity of periphyton. Additions of N+P+K increased biomass-specific net primary productivity of grazed and ungrazed periphyton and markedly increased biomass of periphyton on substrates protected from Campostoma. Although food supply for Campostoma appeared to be greater with nutrient additions, condition of Campostoma in pools receiving N+P+K was not significantly different from Campostoma collected from control pools 35 days after the experiment started. I conclude that although nutrient supply limits biomass-specific primary productivity of periphyton in Brier Creek, nutrient limitation in this stream exacerbates, rather than causes, the visually conspicuous pool-to-pool complimentary distribution of algae and Campostoma: in this stream, grazing by Campostoma at natural densities can outrun periphyton growth even when nutrients are added.     

Fluctuations des nutriments au cours de la marée sur les parcs Ostreicoles de la rivière Penze (Nord-Finistère)

The design and performance of a simple, community level ecotoxicological testsystem is reported. Samples of periphyton communities, established on artificial substratum in natural streams were used to study effects on photosynthetic activity in short-term experiments. Photosynthesis was measured as light-dependent oxygen evolution or as ¹⁴CO₂-incorporation. The variability in photosynthetic activity between samples collected at the same time, expressed as coefficient of variation, was ca 20%. The variation in sensitivity of periphyton photosynthesis as dependent on sampling season was less than threefold for the two long-chained aliphatic amines and the textile industry effluent studied. Effects of the amines on periphyton from five different streams were also investigated. The ratio between maximum and minimum values of sensitivity was 5.6. It is concluded that the variation in sensitivity between different periphyton communities is similar to or less than that observed for fresh-water algal species. Some advantages with regard to ecological realism of using periphyton communities as test systems are discussed.     

Influence of the colonizing substrate on diatom assemblages and implications for bioassessment: a mesocosm experiment

Although diatoms are important bioindicators of ecological quality, their ecological traits are still not well understood. A major issue is that of substrate preferences, which may result in differences in production, and assemblage structure and composition, and which should therefore be taken into account for ecological quality assessment studies. Thus, in this work, the periphyton grown on sand and ceramic tiles in indoor controlled channels were compared to understand whether substrate differences lead to differences in: periphyton production (chlorophyll-a), chlorophyll-b and c concentrations, diatom assemblages (diversity-Shannon-Wiener, cell density, taxonomic composition, trait proportions), and ecological quality assessments (IPS-‘Indice de Polluosensibilité Spécifique’). A combined inoculum of periphyton from four Portuguese streams was introduced to the running channels (six sand and six tile) and left to colonize for 35 days. Epilithic (tiles) and epipsammic (sand) assemblages were sampled at days 14 and 35. We verified that there were no differences in chlorophyll-a concentration over time and between substrates. On both sampling occasions, the epipsammic assemblages had higher concentration of chlorophyll-c and diatom density but without significant differences over time in each substrate. The taxonomic composition was different between substrates and over time. However, these differences were not reflected in ecological quality assessment. The diversity was also similar between substrates in both sampling occasions, but it was higher at day 14. Mobile and stalked species were more abundant over the entire study and differed significantly between substrates, with the epipsammic assemblages presenting higher abundances of both traits. We concluded that the colonizing substrate influences diatom assemblages but not the ecological quality assessment.     

A comparison of algal periphyton composition on eleven species of submerged macrophytes

Summary The composition of algal periphyton was examined on eleven species of submerged macrophytes collected at a depth of 0.25 m in Sewell Lake, southwestern Manitoba, a shallow nitrogen and phosphorus rich lake. There were substantial differences in the periphyton on all macrophyte species. Diatom subcommunities were the most similar, while the green algal subcommunities were the most dissimilar on different plant hosts.Potamogeton zosteriformis differed the most from all other macrophytes with respect to the composition of its periphyton. These results and a comparison of the literature suggest that the composition and structure of periphyton communities on living substrates is a product of the interaction of many variables, determined by the characteristics of the host plant, the external environment and the algae themselves. Studies of periphyton at a given site must take into account the various substrates available.     

Periphyton communities in a pristine mountain stream above and below heavy metal mining operations

SUMMARY. 1. Changes in species composition of the periphyton on introduced substrates were determined in an oligotrophic mountain stream subject to long-term heavy metal contamination.
2. At the upstream control site, the numerically most abundant taxa were Bacillarioph yta i( Achnanlhes minutissima, Achnanthes microcephala and Achnanthes linearis ) as well as, in summer, the Chlorophyta ( Mougeotia spp. and Ulothrix subtilissima ).
3. At the downstream contaminated site the periphyton community was totally dominated by Bacillariophyta throughout the sampling period. A, minutissima and A, microcephala were co-dominants during spring. Seasonal succession patterns did not parallel those at the upstream site. Chlorophyta were virtually absent and A. minutissima comprised 94% of the community during summer.
4. Species diversity, species evenness and dissimilarity index were utilized to detect differences in species composition, abundance and number. Slight differences were found in spring samples while summer samples indicated major differences between sampling sites.     

The potential of fish production based on periphyton

Periphyton is composed of attached plant andanimal organisms embedded in amucopolysaccharide matrix. This reviewsummarizes research on periphyton-based fishproduction and on periphyton productivity andingestion by fish, and explores the potentialof developing periphyton-based aquaculture.Important systems with periphyton arebrush-parks in lagoon areas and freshwaterponds with maximum extrapolated fish productionof 8 t ha^–1 y^–1 and 7 t ha^–1y^–1, respectively. Experiments with avariety of substrates and fish species havebeen done, sometimes with supplemental feeding.In most experiments, fish production wasgreater with additional substrates compared tocontrols without substrates. Colonization ofsubstrates starts with the deposition oforganic substances and attraction of bacteria,followed by algae and invertebrates. Afterinitial colonization, biomass density increasesto a maximum when competition for light andnutrients prevents a further increase. Often,more than 50% of the periphyton ash-free drymatter is of non-algal origin. Highest biomass(dm) in natural systems ranges from 0 to 700g m^–2 and in aquaculture experiments wasaround 100 g m^–2. Highest productivity wasfound on bamboo in brush-parks (7.9 gC m^–2 d^–1) and on coral reefs (3 gC m^–2 d^–1). Inorganic and organicnutrients stimulate periphyton production.Grazing is the main factor determiningperiphyton density, while substrate type alsoaffects productivity and biomass. Better growthwas observed on natural (tree branches andbamboo) than on artifical materials (plasticand PVC). Many herbivorous and omnivorous fishcan utilize periphyton. Estimates of periphytoningestion by fish range from 0.24 to 112 mg dm(g fish)^–1 d^–1. Ingestion rates areinfluenced by temperature, fish size, fishspecies and the nutritional quality of theperiphyton. Periphyton composition is generallysimilar to that of natural feeds in fishponds,with a higher ash content due to the entrapmentof sand particles and formation of carbonates.Protein/Metabolizable Energy (P/ME) ratios ofperiphyton vary from 10 to 40 kJ g^–1.Overall assimilation efficiency of fish growingon periphyton was 20–50%. The limited work onfeed conversion ratios resulted in valuesbetween 2 and 3. A simple simulation model ofperiphyton-based fish production estimates fishproduction at approximately 2.8 t ha^–1y^–1. Together with other food resources infishponds, total fish production with thecurrent technology level is estimated at about5 t ha^–1 y^–1. Because grazingpressure is determined by fish stocking rates,productivity of periphyton is currently themain factor limiting fish production. Weconclude that periphyton can increase theproductivity and efficiency of aquaculturesystems, but more research is needed foroptimization. Areas for attention include theimplementation and control of periphytonproduction (nutrient levels, substate types andconformations), the ratio of fish to periphytonbiomass, options for utilizing periphyton inintensive aquaculture systems and with marinefish, and possibilities for periphyton-basedshrimp culture.     

Algae of periphyton of Lake Teletskoye

The generalized data are given on the composition and structure of phytoperiphyton of Lake Teletskoye on different substrates (rocks, macrophytes and their residues). It is noted that in spite of the differences in the taxonomic structure and level of development the algocenoses of periphyton of various substrates have similar ecological range. This gives a possibility of using the algocenoses of periphyton on different substrates for assessing the quality of the lake water.     

Patterns of nutrient release from nutrient diffusing substrates in flowing water

As nutrient diffusing substrates age, the availability of nutrients to periphyton may decline with time either because of diffusion or dilution of nutrients into the water column or because of the effects of grazing by herbivores. Typically, large amounts of nutrients are added to nutrient diffusing substrates (NDS) to insure continuous enrichment throughout experimental periods of 2 to 8 weeks. This study examined the release of phosphates and nitrates from NDS exposed to three different current velocities (0.07 m s^–1, 0.11 m s^–1, 0.20 m s^–1) in recirculating laboratory flumes. Replicated agar samples from four treatments (control, nitrate (N), phosphate (P), and N+P) were sampled throughout 32 days (day 1, 2, 3, 6, 12, 18, 24, 32). Increasing concentrations of agar were required to solidify the P and N+P treatments.Nutrient release rates from NDS were independent of agar concentrations (with the exception of [PO₄] in the medium velocity flume). Nutrient concentrations in the agar of spiked samples declined substantially within a week when exposed to flowing water. Nitrates were retained in agar to a greater extent than phosphates particularly when NDS were exposed to low or medium flows. Although floods physically remove or abrade periphyton in natural streams, findings from this laboratory study suggest that ambient flows deplete the availability of nutrient concentrations to potential periphyton colonizers within the first week of incubation. Because of the rapid decline of nutrients from NDS, short incubation periods in natural running waters seem warranted.     

Comparative algological and bacteriological examinations on biofilms developed on different substrata in a shallow soda lake

According to the European Water Framework Directives, benthic diatoms of lakes are a tool for ecological status assessment. In this study, we followed an integrative sample analysis approach, in order to find an appropriate substratum for the water qualification-oriented biomonitoring of a shallow soda lake, Lake Velencei. Six types of substrata (five artificial and one natural), i.e., andesite, granite, polycarbonate, old reed stems, Plexiglass discs and green reed, were sampled in May and in November. We analysed total alga and diatom composition, chlorophyll a content of the periphyton, surface tension and roughness of the substrata and carbon source utilisation of microbial communities. Water quality index was calculated based on diatom composition. Moreover, using a novel statistical tool, a self-organising map, we related algal composition to substratum types. Biofilms on plastic substrates deviated to a great extent from the stone and reed substrata, with regard to the parameters measured, whereas the biofilms developing on reed and stone substrata were quite similar. We conclude that for water quality monitoring purposes, sampling from green reed during springtime is not recommended, since this is the colonization time of periphyton on the newly growing reed, but it may be appropriate from the second half of the vegetation period. Stone and artificially placed old reed substrata may be appropriate for biomonitoring of shallow soda lakes in both spring and autumn since they showed in both seasons similar results regarding all measured features.     

Interactions between neighboring algae and snail grazing in structuring microdistribution patterns of periphyton

The micro-distribution of periphyton (filamentous algae) on homogeneous substrates was examined in experimental tanks with and without the pressure of grazing snails. The growth of periphyton attached to artificial substrate was estimated at a small spatial scale (9.3 mm×9.3 mm cells) by varying the number of grazers (0, 5, or 10 snails per tank), using image processing analysis without removing the periphyton. The results suggest that periphyton growth within a cell was negatively affected by the biomass of periphyton in the cell but was positively affected by the biomass of periphyton in neighboring cells. A semivariogram analysis indicated that spatial heterogeneity increased with increasing grazing pressure. The size of patches was not clearly related to the number of snails, but there was a tendency for relative patch size to increase with snail density. Computer simulations were also conducted to examine factors affecting the degree of spatial heterogeneity. The simulation studies indicated that snails should graze a site that was previously grazed in order to produce the observed spatial heterogeneity of periphyton. The results also indicated that the positive effects of neighboring periphyton on the growth of algae might create patches. The interactions among neighboring algae and snail grazing might be an important factor creating the spatial heterogeneity of periphyton even on homogeneous substrates.     

Periphyton growth and diatom community structure in a cooling water pond

Periphyton (Aufwuchs) accumulation was measured on artificial substrates in a pond in central Finland which receives warm cooling-water effluent from a power plant. The growth of periphyton was generally more rapid on the substrates during the first two weeks of colonization near the inflow of the warm water effluent than in the middle of the pond. The maximum accumulation of periphyton was in spring and autumn (dry weight maximum at warm effluent was in spring 3.5 mg DW cm⁻²,2.65 mg AFDW cm⁻²; chlorophyll a maximum 3.96 μg cm⁻² was found in autumn at pond-middle station). During mid-winter months the growth was strongly limited by solar radiation, but the growth was also slow at both stations in the summer months, when the power plant was out of operation. The periphyton accumulation rate was fastest near the water surface and decreased rapidly with increasing depth. A total of 167 diatom species were found in periphyton samples. However, most species were rare; many of the dominants were common to both plankton and periphyton. Species similarity analyses (Jaccard's similarity) between 10 different diatom communities (including periphyton from 9 different types of substrates and phytoplankton) indicated low similarity index values although differences between communities were not significant.     

Phosphorus removal from eutrophic lakes using periphyton on submerged artificial substrata

The potential of periphyton for phosphorus removal from lakes has been investigated using a novel method involving polypropylene (PP) substrate carriers submerged in the pelagial. The study area Lake 'Fühlinger See' in Cologne (Germany) is a complex of mesoeutrophic gravel pit lakes. The whole site is intensively used as a recreation area. Visitors are thought to be the most important single contributors to lake eutrophication. Carriers were exposed at different depths (2, 3.5, 5 m), for different time intervals (1–8 months) and from March to November PP-sheets were readily colonised by periphyton and a biofilm consisting mainly of benthic diatoms developed. Seasonal variability of periphyton on substrates was observed since filamentous green algae colonised the artificial substrates mainly between July and November. Chlorophyll a content of periphyton on the PP-fleece was up to 240-fold higher than chlorophyll a concentrations in the same volume in the epilimnion. Up to around 100 mg of total phosphorus per m² PP-fleece was bound and can be eliminated from the lake by removal of the substrate carriers together with the periphyton after four months of exposure. Though large-scale validations are needed, this method may be applicable as a technique to harvest phosphorus from the water column in larger-scale settings.     

Dreissenid mussels enhance nutrient efflux, periphyton quantity and production in the shallow littoral zone of a large lake

Dreissenid mussels are notorious invasive organisms whose establishment is associated with large, ecosystem-scale changes to patterns of productivity in aquatic systems. We investigated how localized impacts of dreissenids affect the potential of littoral substrates to support primary and secondary production using in situ incubations and comparisons of natural mussel-colonized and mussel-free substrates in the littoral zone of a large, shallow lake. We compared dreissenid-colonized and dreissenid-free substrates in terms of nutrient balance, surface area, periphyton loads as well as benthic primary production and respiration rates. Dreissenid-colonized substrates acted as sources of dissolved nutrients to the water column, with mussel mass-specific rates of dissolved phosphorus and ammonia excretion averaging 7.2 ± 5.6 (mean ± SD), and 92.6 ± 64.7 μg/g mussel shell free dry mass/h, respectively. Mussel-colonized substrates also had higher surface area, and supported approximately double the amount of periphyton and organic matter loads compared to mussel-free substrates, as well as having higher rates of primary production and community respiration. We suggest that the localized effects of dreissenids can play an important role in changing whole-ecosystem production patterns, with the extent of dreissenid impacts strongly dependent on lake size and morphometry.     

Influence of substrate type on periphyton biomass and nutrient state at contrasting high nutrient levels in a subtropical shallow lake

How substrate affects periphyton biomass and nutrient state at different, but high, nutrient levels was tested in three large enclosures in a hypereutrophic subtropical shallow lake. We compared periphytic characteristics (1) on three hard substrates (stone, bamboo, and wood) incubated for 2 weeks and 1 year, respectively, to investigate the existence of the influences of substrate type at hypereutrophic levels, and (2) on artificial plants with contrasting (parvopotamid-like and myriophyllid-like) soft substrate morphology. In general, periphytic biomass and nutrient state were sensitive to variations in nutrient level, incubation time, hard substrate type (except 2-week incubated) and substrate morphology, but to a varying extent. The periphyton nutrient content increased with increasing nutrient levels on most substrates. Long-time incubated substrates supported more periphytic biomass, had a higher nutrient content and autotrophic proportion, while the effect of nutrient level on nutrient content in the periphyton was independent of incubation time. The effects of hard substrate type on periphyton characteristics were much weaker than those of nutrient level. By contrast, the effects of soft substrate morphology on periphyton biomass and carbon: nutrient ratios surpassed those of nutrient level. Chlorophyll a, dry mass, and ash free dry mass were much higher on parvopotamid than on myriophyllid substrates. Our results show that periphyton biomass and nutrient state are influenced by both substrate and nutrient level even in hypereutrophic lakes, which might have cascading effects on the benthic food web.