Periphyton Samples Research Articles

Variations of periphytic diatom sensitivity to the herbicide diuron and relation to species distribution in a contamination gradient: implications for biomonitoring

Diatoms are commonly used as bioindicators of trophic and saprobic pollution in rivers. However, more knowledge is needed concerning their sensitivity to toxicants such as agricultural herbicides. In this study, seven species of periphytic diatoms were isolated from the Morcille River (Beaujolais area, France) which presents a streamward contamination gradient by pesticides and particularly diuron. The sensitivity of these species to diuron was assessed through ecotoxicological tests based on short-term growth inhibition of monospecific cultures. After application of an appropriate toxicological model, EC50 were determined and the species were ranked according to their tolerance. EC50 values ranged from 4.5 to 19 μg L(-1). Finally, the results were related to field periphyton samples from an upstream and a downstream site in order to check if variations in specific relative abundance between sites are consistent with differences in tolerance to diuron. Species distribution between sites was only partially in accordance with toxicological results suggesting that other factors (toxic or trophic) have an important influence on diatom communities in the river. Nevertheless, diatoms showed their potential to indicate water contamination by pesticides and toxic indices could be developed in complement to existing trophic indices.

Composition, Occurrences and Checklist of Periphyton Algae of Some Water Bodies Around Benin City, Edo State, Nigeria

This paper presents an investigation of the periphyton algae of five rivers around Benin City. The rivers studied were River Okhuaihe (station 1), River Ikpoba (station II), River Ossiomo, Ologbo station (station III), River Siluko (station IV) and River Ogba (station V). Samples were collected monthly for periphyton and physico-chemical analysis. Periphyton samples were collected by scraping the roots, leaves and stems of aquatic macrophytes, dead and felled logs submerged on the banks of the rivers as well as from rocks embedded in the substratum while water samples for physical and chemical parameters were collected directly into clear plastic containers. The rivers were acidic with a pH range of 5.10-6.31 and very low in nutrients. A total of 87 taxa of periphyton algae were identified and categorized into 4 divisions, 11 orders, 9 families and 44 genera. The distribution among the division was Chlorophyta 64.37%, Bacillariophyta 22.99%, Cyanophyta 5.75% and Euglenophyta 6.89%. The majority of the green periphyton algae were desmids. Key words : Periphyton, rivers, physico-chemical, taxa.

An index of limnological conditions for urban wetlands of Bogotá city, Colombia

The urban wetlands of Bogotá are ecosystems of great importance, yet they are deteriorating. The state of deterioration must be evaluated in order to develop new methods of ecosystem monitoring and conservation. Here we describe the development of an index to assess the ecological health of five urban wetlands and one rural wetland from limnological data. The field phase of this study took place in November 2007 (rainy season) and February 2008 (dry season). Physical and chemical variables of the wetland ecosystems (temperature, dissolved oxygen, pH, conductivity, hardness, chlorides, ammonia, nitrites, nitrates, orthophosphates, and biological oxygen demand) were measured and samples of phytoplankton, periphyton, macroinvertebrates, and aquatic plants (macrophytes) were collected. The indices developed (biotic indices of communities: BI, and limnological conditions index: LICOI) allow classification of wetlands into three categories: those that have “acceptable limnological conditions” (Meridor, Jaboque and Guaimaral), those with “regular limnological conditions” (Santa María del Lago, Juan Amarillo) and those with “poor limnological conditions” (Tibanica). None of the environments studied fit a potential fourth category of “best limnological conditions.” The LICOI is a management tool that can be used to assess changes in wetlands after positive actions (restoration, cleaning, hydraulic management), or negative impacts (depletion, alien species, pollution). It also could allow regular monitoring of wetland evolution and serve as a basis for the development of indices measuring the ecological status of other aquatic environments in Colombia.

Submersion time, depth, substrate type and sampling method as variation sources of marine periphyton

Periphyton is an additional food source in African and Asian brackish and freshwater fish ponds. The present study was a preliminary assessment of periphyton development on artificial substrates in temperate marine ponds. The effects of submersion time, substrate type, water depth, and total or partial sampling methods on the quantity and quality of periphyton collected, were evaluated. Four types of substrate (W: wooden poles, S: smooth fiber-glass strips, m: mosquito screen (1 mm-mesh) and M: garden netting (5 mm-mesh)) were deployed in a marine pond, and periphyton was collected 15 and 30 days later. The total amount of periphyton per substrate unit was collected as one sample or as 5 sub-samples. Results showed that (i) periphyton biomass in a marine pond increased between day 15 and day 30, (ii) more periphyton was collected on mosquito screen than on wooden poles, fiberglass strips and garden netting, (iii) periphyton biomass increased with submersion depth, (iv) sub-sampling leads to an underestimate compared to whole unit sampling, and (v) a correction of periphyton weight must be carried out considering the dissolved inorganic salts present in periphyton samples from marine and brackish ponds. Whole substrate unit sampling using a tube and stopper is recommended to avoid underestimation of periphyton development. Finally, the autotrophic fraction in the periphyton communities was very low compared to periphyton developed on biodegradable substrates in fertilized tropical ponds. Studies on fertilization and use of biodegraded substrates (i.e. long-time submerged wood) are recommended to further optimize periphyton development in temperate marine ponds.

Spatial and temporal patterns of periphyton chlorophyll a related to pulp and paper mill discharges in four us receiving streams

Nutrients in pulp and paper mill effluent (PPME) have been implicated in increased periphyton chlorophyll a (chl a) downstream of discharges. These findings are largely based on short-term studies conducted in artificial stream channels or mesocosms and often in oligotrophic systems, and it is unclear if long-term chl a patterns in higher-nutrient systems would show similar response. We conducted a long-term study of 4 receiving waters (Codorus Creek, Pennsylvania; the Leaf River, Mississippi; and the McKenzie and Willamette rivers, Oregon) in which periphyton samples and associated data on water quality (nitrogen and phosphorus concentrations, pH, color, and conductivity) and 2 physical habitat variables (depth and current velocity) were collected over an 8-y period from multiple sites upstream and downstream of PPME discharges. Study streams represented different ecoregions, warm- and coldwater systems, gradients of in-stream effluent concentration (<1-33%), and mill process types. General Linear Models examining the main and interaction effects of site, season, and year on periphyton chl a for each of the 4 streams showed periphyton chl a downstream of the PPME discharge in Codorus Creek and the McKenzie River was greater at some, but not all upstream sites, suggesting these differences may be due to factors other than PPME. Mean periphyton chl a ranged from <1 to 285 mg/m2 across streams, with relatively consistent site patterns across seasons and years. Overall, chl a in the spring and summer was greater than in the fall in Codorus Creek and on sand substrates in the Leaf River, with overall differences across years seen on rare occasions in the Leaf and Willamette rivers. Regression models examining environmental-chl a relationships explained 45.4% and 30.2% of variation in periphyton chl a in the McKenzie River and Codorus Creek, respectively, and <10% in the Leaf and Willamette rivers. Physical variables (stream depth and current velocity) were the most important model variables in the McKenzie River, while total nitrogen and color were of greatest importance in Codorus Creek. The findings of this study demonstrate the inherent variability of chl a standing crops, highlight the complexity of lotic periphyton communities, and reiterate the importance of long-term, multi-season studies in elucidating spatial and temporal patterns.

Diatoms from the Colombian and Peruvian Amazon: the Genera Encyonema, Encyonopsis and Gomphonema (Cymbellales: Bacillariophyceae)

The diatom flora of the Colombian and Peruvian Amazon is far less studied than the flora of the Brazilian sector of the basin. Here we present results related to the genera Encyonema, Encyonopsis and Gomphonema. Plankton and periphyton samples were collected in lotic and lentic waterbodies from the Amazonian-Andean region, the Amazon River, Japurá River and Porvenir River basins during 1993, 1994, 2001 and 2003. At each sampling station pH, temperature, water transparency and conductivity were registered. Samples were analyzed with phase contrast microscope (LM) and scanning electron microscope (SEM). Ten taxa are new records for the area; Encyonema for the Peruvian and Colombian Amazon and Encyonopsis for the Colombian Sector. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum and G. contraturris are recorded for the first time in Colombia; Encyonema venezolanum and G. neoapiculatum in Colombia and Peru and the latter also for Amazonia. E. angustecapitatum was mentioned in Colombia before at a pond located at 3000 m asl. We describe a new species from Porvenir River, Amazonas, Colombia: Encyonema amazonianum.

The epiphytic communities of various ecological types of aquatic vegetation of five pastoral ponds

Five small water bodies located within the agricultural region of Wielkopolska (west Poland) underwent inves- tigation. Periphyton samples were collected from various macrophyte habitats representing rush vegetation (in five water bodies), submerged aquatic plants (in three) and nymphaeids (in one): Pal˛ edzie - Ceratophyllum demersum, Potamogeton crispus, Typha latifolia; Batorowo - Phragmites australis ;P iotrowo -Potamogeton natans, Ceratophyllum submersum, Ty- pha latifolia; Tarnowo Podgorne - Typha latifolia ;D ˛ - Zannichellia palustris, Potamogeton pectinatus, Phragmites australis. The main goal of the study was to determine the composition and abundance of the periphytic communities inhabiting various types of rush and water vegetation of five water bodies located within a mid-field landscape area. Diatoms such as Achnanthidium minutissimum, Amphora ovalis, Cocconeis placentula orNavicula cincta revealed signifi- cantly higher densities in the zone of elodeids, while green algae prevailed among nymphaeids. As a result of this study it was found that the epiphytic algae were characterised by much lower diversity in respect to a specific water body, though much greater diversity was observed in its relation to the type of substratum. Two types of habitats were distinguished - the first of simple build (helophytes and nympheids) and the second containing the complicated architecture of plant stems (elodeids).

Spatial heterogeneity of periphytic microbial communities in a small pesticide-polluted river

Spatial variability in the microbial community composition of river biofilms was investigated in a small river using two spatial scales: one monitored the upstream-downstream pesticide contamination gradient, referred to as the 'between-section variability', and the other monitored a 100-m longitudinal transect (eight sampling sites per section) within each sampling section, referred to as the 'within-section variability'. Periphyton samples were collected in spring and winter on artificial substrates placed in the main channel of the river. Denaturing gradient gel electrophoresis (DGGE) was used to assess the prokaryotic and eukaryotic community richness and diversity, and HPLC pigment analysis to assess the global taxonomic composition of the photoautotrophic community. In order to try to reduce the biological variability due to differences in flow velocity and in light conditions within each sampling section, and consequently to take into account only the changes due to water chemistry, nine plates (three per sampling section) subjected to similar physical conditions were chosen, and the results for these plates were compared with those obtained for all 24 plates. As shown by DGGE and by HPLC analyses, using these three substrate plates exposed to similar environmental conditions did indeed reduce the within-section variability and maximize the between-section variability. This sampling strategy also improved the evaluation of the impact of pollutants on the periphytic communities, measured using short-term sensitivity testing.

Analysis of interrelation between water quality and hydrologic conditions on a small karst catchment area of sinking watercourse Trbuhovica

Sinking watercourse Trbuhovica is located at the topping karst of Gorski Kotar in Croatia, near the Slovenian border. About 900 inhabitants live in Trbuhovica catchment area. Sewage system had not been built. The project KEEP WATERS CLEAN (INTERREG III A project) was approved by EU commission and has a purpose of investigating water resources of that area, their appropriate protection and improving management of those resources. This paper presents project's 1st phase investigation results: hydrologic conditions and water quality at several locations on stream and at the springs of Trbuhovica, Mlake and Obrh. Climatologic (precipitation, air temperature and snow cover), basic hydrologic characteristics (flow and water temperature), water quality parameters (pH, electric conductivity, alkalinity, oxygen regime, nutrients and mineral oils) and microbiology indicators have been monitored. Samples of micro invertebrates and samples of periphyton have been collected in the field. Biological results have been elaborated via Saprobial Index according to Pantle-Buck. Analyses results showed a strong connection between hydrologic condition and selected water quality parameters. The groundwater quality changes are very quick. Maximum pollutions occur during the period of intensive rain. Water at the spring of Mlaka is very clean and is classified in the first to second water category, while Trbuhovica shows higher organic pollution.

Planktonic and Biochemical Composition of Periphyton Grown on Some Biodegradable and Non-Degradable Substrates

ABSTRACT Ten locally available substrates, five biodegradable and five non-degradable, were evaluated for their potential to harbor periphyton in cement tanks fertilized with poultry manure. The tanks were fertilized regularly and the periphyton was allowed to grow for 70 days. Weekly samples of periphyton and plankton were collected for enumeration and biochemical analyses. Among the substrates, earthen tiles harbored negligible amount of periphyton. The phytoperiphyton genera encountered on the substrate belonged mainly to Chlorophyceae (14 genera), followed by Cyanophyceae (2 genera), Chrysophyceae (1 genus), Bacillariophyceae (1 genus), and Dinophyceae (1 genus). Nauplius, Keratella, Diaptomus, Cyclops, Moina, Chironomus and insect eggs were the zooplankton encountered on substrates. Phytoplankton density was higher on tyre (86,426 cells or colonies/cm2) and palm leaf (85,808 cells or colonies/cm2) and lowest on ceramic tile (21,081 cells or colonies/cm2). Glass plates harbored the highest number of zooplankton species per unit area (1050 cells or colonies/cm2), while arecanut leaf-sheath had the lowest (210 cells or colonies/cm2). All five families of phytoplankton present on the substrates were also present in tank water. While periphyton contained 26 genera, tank water had only 24. Periphytic dry matter, ash, ash-free dry matter, plankton density on substrates and water showed a general increase with respect to time. Polyvinyl chloride (PVC) (0.972 mg/cm2), glass (0.913 mg/cm2), and bamboo (0.897 mg/cm2) had higher periphytic dry matter and ceramic tile (0.262 mg/cm2) the lowest. All the proximate composition parameters of periphyton, except nitrogen free extract (NFE) varied significantly (P < 0.05) between the substrates. The moisture content of periphyton ranged from 85.58% (bamboo) to 95.27% (arecanut leaf-sheath). Crude protein was high in periphyton from bamboo (3.77%) and tyre (3.66%) and low in that from arecanut leaf-sheath (0.99%).

Non-intrusive characterization methods for wastewater-affected groundwater plumes discharging to an alpine lake

Streams and lakes in rocky environments are especially susceptible to nutrient loading from wastewater-affected groundwater plumes. However, the use of invasive techniques such as drilling wells, installing piezometers or seepage meters, to detect and characterize these plumes can be prohibitive. In this work, we report on the use of four non-intrusive methods for this purpose at a site in the Rocky Mountains. The methods included non-invasive geophysical surveys of subsurface electrical conductivity (EC), in-situ EC measurement of discharging groundwater at the lake-sediment interface, shoreline water sampling and nutrient analysis, and shoreline periphyton sampling and analysis of biomass and taxa relative abundance. The geophysical surveys were able to detect and delineate two high-EC plumes, with capacitively coupled ERI (OhmMapper) providing detailed two-dimensional images. In situ measurements at the suspected discharge locations confirmed the presence of high-EC water in the two plumes and corroborated their spatial extent. The nutrient and periphyton results showed that only one of the two high-EC plumes posed a current eutrophication threat, with elevated nitrogen and phosphorus levels, high localized periphyton biomass and major shifts in taxonomic composition to taxa that are commonly associated with anthropogenic nutrient loading. This study highlights the need to use non-intrusive methods in combination, with geophysical and water EC-based methods used for initial detection of wastewater-affected groundwater plumes, and nutrient or periphyton sampling used to characterize their ecological effects.

Efficacy of algal metrics for assessing nutrient and organic enrichment in flowing waters

Summary1. Algal‐community metrics were calculated for periphyton samples collected from 976 streams and rivers by the U.S. Geological Survey’s National Water‐Quality Assessment (NAWQA) Programme during 1993–2001 to evaluate national and regional relations with water chemistry and to compare whether algal‐metric values differ significantly among undeveloped and developed land‐use classifications.2. Algal metrics with significant positive correlations with nutrient concentrations included indicators of trophic condition, organic enrichment, salinity, motility and taxa richness. The relative abundance of nitrogen‐fixing algae was negatively correlated with nitrogen concentrations, and the abundance of diatom species associated with high dissolved oxygen concentrations was negatively correlated with both nitrogen and phosphorus concentrations. Median algal‐metric values and nutrient concentrations were significantly lower at undeveloped sites than those draining agricultural or urban catchments.3. Total algal biovolume did not differ significantly among major river catchments or land‐use classifications, and was only weakly correlated with nitrate (positive) and suspended‐sediment (negative) concentrations. Estimates of periphyton chlorophyll a indicated an oligotrophic–mesotrophic boundary of about 21 mg m−2 and a mesotrophic–eutrophic boundary of about 55 mg m−2 based on upper and lower quartiles of the biovolume data distribution.4. Although algal species tolerance to nutrient and organic enrichment is well documented, additional taxonomic and autecological research on sensitive, endemic algal species would further enhance water‐quality assessments.

Influence of velocity and chlorophyll standing stock on periphyton δ13C and δ15N in the Ste. Marguerite River system, Quebec

In a previous laboratory experiment, water velocity had a strong negative effect on periphyton δ13C and δ15N, probably reflecting the effect of flow on boundary-layer exchange. To determine whether similar patterns could be detected in situ at different spatial scales, we examined several reaches, each with a wide range in water velocity and chlorophyll standing stock. Periphyton samples were uniform in composition, composed predominantly of living and dead diatoms of very few species. δ13C signatures were more variable (–17.7‰ to –31.5‰) than δ15N signatures (–0.4‰ to 5.7‰). Velocity and chlorophyll were significant predictors of periphyton δ13C within reaches, mainly at medium scales (10–500 m) where persistent alternations between fast and slow current (riffles–runs–pools) produced inverse fluctuations of periphyton δ13C. However, none of the variability in δ15N could be explained, possibly a result of severe boundary-layer N depletion. Similarly, the velocity and chlorophyll predictors could not explain the among-reach signature differences for either isotope. δ13C signatures tended to be13C-depleted in the tributary streams and13C-enriched in the downstream reaches.

Mercury Accumulation in Periphyton of Eight River Ecosystems1

Abstract: In 2003, the U.S. Geological Survey (USGS) National Water‐Quality Assessment (NAWQA) program and U.S. Environmental Protection Agency studied total mercury (THg) and methylmercury (MeHg) concentrations in periphyton at eight rivers in the United States in coordination with a larger USGS study on mercury cycling in rivers. Periphyton samples were collected using trace element clean techniques and NAWQA sampling protocols in spring and fall from targeted habitats (streambed surface‐sediment, cobble, or woody snags) at each river site. A positive correlation was observed between concentrations of THg and MeHg in periphyton (r2 = 0.88, in log‐log space). Mean MeHg and THg concentrations in surface‐sediment periphyton were significantly higher (1,333 ng/m2 for MeHg and 53,980 ng/m2 for THg) than cobble (64 ng/m2 for MeHg and 1,192 ng/m2 for THg) or woody snag (71 ng/m2 for MeHg and 1,089 ng/m2 for THg) periphyton. Concentrations of THg in surface‐sediment periphyton had a strong positive correlation with concentrations of THg in sediment (dry weight). The ratio of MeHg:THg in surface‐sediment periphyton increased with the ratio of MeHg:THg in sediment. These data suggest periphyton may play a key role in mercury bioaccumulation in river ecosystems.

Phenotypic characterization and molecular taxonomic studies on Bacillus and related isolates from Phragmites australis periphyton

Reeds may play important role in the self-purification of aquatic habitats due to the filtration capacity and their periphyton communities developing on the underwater plant surfaces. The efficiency of this process and the transformation of organic substances can be influenced by the species composition and activity of microbial communities, including Bacillus and related species. For cultivation based bacteriological examinations reed periphyton samples were collected from 30 cm beneath the water surface of Lake Velencei and the Soroksár Danube branch (Hungary). After a primary selection 40 Bacillus and related strains were investigated by traditional morphological, biochemical tests, API 20E, API 50CHB and BIOLOG GP2 systems, and identified by 16S rDNA sequence comparison. The isolated strains were characterized by wide biochemical activity spectrum (i.e., the metabolism of carbohydrates and biopolymers) as well as widespread ecological tolerance based on their NaCl and pH range investigations. Species with facultative alkaliphilic features ( Marinibacillus marinus, Bacillus firmus) were detected only from the reed biofilm of Lake Velencei, while alkalitolerant Bacillus and related species from both sampling sites. 22 endospore-forming strains were identified as members of species B. cereus, B. firmus, B. flexus, B. licheniformis, B. megaterium, B. muralis, B. pumilus, B. subtilis and Marinibacillus marinus. Only one species, with 95–96% sequence similarities to B. pumilus was found to be common among the strains from Lake Velencei and the Soroksár Danube branch. Altogether, 18 strains could not be identified as known species of Bacillus, Brevibacillus and Paenibacillus, hence they may represent new bacterial taxa.

Within‐lake variability in carbon and nitrogen stable isotope signatures

Summary1. We assessed spatial and temporal variation in carbon and nitrogen isotopic signatures in different compartments of a single lake ecosystem. Stable isotope analyses were made on samples of particulate organic matter (POM), zooplankton, periphyton, macrophytes, macroinvertebrates and fish collected from several locations throughout the ice‐free period.2. No spatial variation in δ13C or δ15N values was found for pelagic samples of POM and zooplankton. However, pelagic δ15N signatures increased steadily through the summer resulting in an almost 6‰ average increase in POM and zooplankton. A concurrent decrease in epilimnetic nitrate concentrations suggested that the increase in δ15N of POM and zooplankton could have resulted from a progressive 15N‐enrichment of the available inorganic nitrogen pool as the size of this pool was reduced.3. Significant spatial variation in isotopic ratios was observed within littoral and profundal communities. Some spatial differences were likely related to lake‐specific characteristics, such as a major inlet and a small harbour area and some were interconnected with temporal events.4. Marked differences between spring and autumn δ15N and δ13C values of fish at one site probably reflected a spring spawning immigration from a larger downstream lake and also indicated limited dispersal of these immigrants.5. Our results indicate that restricted sampling of ecosystem components from lakes may provide misleading single values for the isotope end members needed for quantitative uses of stable isotopes in mixing models and for estimating trophic position. Hence we strongly advise that studies of individual lakes, or multiple lake comparisons, that utilise stable isotope analyses should pay more attention to potential within lake spatial and temporal variability of isotope ratios.

Substrate specificity of periphytic desmids in shallow softwater lakes in Belgium

At 6 sites in 5 mesotrophic softwater lakes in the wetland Zwart Water (Belgium), periphyton samples were collected on different substrates ranging from macrophytes to mosses and sandy sediment. Significant differences between substrates were observed at 5 out of 6 sites studied. The differences between the substrates, however, could not be related to known effects of these substrates on their chemical environment (e.g., excretion of H+ ions, CO2 or allelopatic substances) nor to their morphology. Therefore, differences between substrates were probably related to differences in local environmental conditions associated with these substrates. Differences in desmid community composition between substrates within a lake were always smaller than differences with samples from other lakes.

EVALUATION OF PIGMENT EXTRACTION METHODS AND A RECOMMENDED PROTOCOL FOR PERIPHYTON CHLOROPHYLL a DETERMINATION AND CHEMOTAXONOMIC ASSESSMENT1

Many methods have been proposed to extract and quantify algal pigments. Comparative studies have found that pigment extraction efficiency varies among solvent and mechanical disruption protocols due to differential cellular resistance, thereby, leading to potential misinterpretation of pigment data. When the type or resistance of algae are unknown, a method is required that efficiently extract pigments from all taxonomic groups. The objective of this study was to develop a simple and efficient one stage periphyton pigment extraction protocol by comparing the extractability of four solvents (acetone, methanol, methanol/acetone, and methanol/acetone/N,N‐dimethylformamide), the effects of grinding, and the effects of freeze‐drying. The best overall extraction was obtained using freeze‐dried samples extracted with methanol/acetone/DMF/water (MAD). Eighty‐six percent more chlorophyll was extracted when the sample was freeze‐dried relative to fresh/frozen samples extracted with 90% acetone. Freeze‐drying greatly improved the extraction of both polar and non‐polar (lipophilic/hydrophobic) pigments while MAD increased the extractability of polar pigments and improved peak resolution of all pigments. Chemotaxonomic assessment differed between samples that were fresh/frozen or freeze‐dried before extraction. The relative abundance of cyanobacteria was greater for freeze‐dried material compared with fresh/frozen due to the improved extractability of cyanobacterial pigments. Based on the results of this study, the traditional approach of 90% acetone as a solvent is not recommended for periphyton samples containing cyanobacteria or when the composition of the mat is unknown. The combination of freeze‐drying and MAD was sufficient for the extraction of pigments from a periphyton mat containing filamentous cyanobacteria, green algae, and diatoms.

Algal indicator system of environmental variables in the Hadera River basin, central Israel

We identified 126 species of algae and cyanoprokaryotes from seven divisions in 21 samples of plankton and periphyton collected at 8 stations over the Hadera River in 2003 – 2005. The chlorophytes strongly prevail. Of these, 110 species are indicators of environmental conditions. The indicators of saprobity (Watanabe's scale) show a medium level of organic pollution. The saprobity index S (Sládecek's scale) varies from 1.73 to 2.80, corresponding to II – IV classes of water quality. The environmental pollution index (EPI) varies from 2 to 5 indicating a range of slightly to strongly polluted water of classes III and IV. The Water Ecosystem State Index, WESI = 0.6, testifies to a toxic impact on the algae in the middle reaches. The River Pollution Index for saprobity (RPIs = 2.35 – 2.42), temperature (RPIt = 17.1 in winter), conductivity (RPIε = 3.31 – 4.5), nitric nitrogen (RPIN = 15.3), and pH (RPIpH = 7.6 – 8.3) indicate alkaline, moderately mineralized waters with an occasional input of nitrates all year round, corresponding to classes III – IV of water quality, and the beta- to alfa-mesosaprobic self-purification zone. According to our results, the self-purification capacity of the Hadera River ecosystem is rather high. This study shows the potential of the algal bioindication method for aquatic ecosystems of Israel.

Low algal carbon content and its effect on the C : P stoichiometry of periphyton

Summary1. We examined the contribution of algal cells to periphytic organic carbon and assessed the effects of variable biomass composition on the carbon : phosphorus (C : P) ratio of periphyton. We compiled more than 5000 published and unpublished observations of periphytic carbon : chlorophyll a (C : Chl) ratios, an index of algal prevalence, from a variety of substrata collected from lake and low‐salinity coastal habitats. In addition, we converted estimates of algal biovolume into algal C to obtain an independent measure of cellular algal carbon in periphyton. This information was used in a model relating periphyton C : P ratio to algal cellular carbon, the algal C : P ratio, and the C : P ratio of non‐algal organic matter in periphyton.2. The mean C : Chl ratio of periphyton (405) was relatively high with values in &gt;25% of the samples exceeding 500. On average, 8.4% of total periphyton C was accounted for by C in algal cells. Only 15% of samples were found to have more than 15% periphyton C in cellular algal carbon. Our model showed a nonlinear relationship between periphytic C : P ratios and the C : P ratio of algal cells in the periphyton when non‐algal organic matter was present. However, even at relatively low cellular algal C (&lt;10% of total C), algal C : P ratios can strongly affect the C : P ratio of periphyton as a whole (i.e. algal cells plus other organic matter).3. The high C : Chl ratios and the low biovolume‐derived algal C of periphyton samples in our data set indicate that algal cells are typically a minor component of organic carbon in periphyton, However, this minor contribution would not preclude algal cellular stoichiometry from notably influencing periphyton C : P ratios.