UNIALGAL CULTURES OF CLADOPHORA GLOMERATA (L.) KÜTZ.12

Unialgal cultures of Cladophora glomerata (L.) Kütz. grew with increasing vigor at temperatures between 15 and 30 C. Vegetative cells were killed upon freezing or when exposed to temperatures above 30 C. No growth occurred at 5 C and only slight growth was observed at 10 C. Effects of near lethal temperature on C. glomerata were dependent upon the duration of exposure in addition to the actual temperature attained. The response of this alga to various temperatures under culture conditions is in accord with tolerance limits established for naturally occurring populations. It seems probable that the annual periodicity of C. glomerata is regulated in large measure by seasonal variations in water temperature, greatest abundance coinciding with water temperatures between 15 and 30 C.     

Studies on the growth of riverainCladophora in culture

Summary Techniques were developed for studying the effects of environmental factors on the growth in culture ofCladophora glomerata from flowing waters.Cladophora still attached to rocks was transferred from the river to a laboratory stream and incubated there for 4 days under standard conditions. Small pieces of this material were cut off, cleaned, and used as inocula for shake culture experiments. These experiments were mostly designed to test the effect of various agents which have been widely quoted, in literature based on field observations, as limiting the growth ofCladophora. The alga is particularly sensitive to copper and zinc among the metals tested, and to DOBS-055, a soft detergent, among the detergents tested. The experimental results support the hypothesis that the alga may occasionally be limited by high natural iron concentrations, but not that it is so sensitive to high temperature that this factor alone would often limit its growth in British rivers.     

Occurrence of Escherichia coli and enterococci in Cladophora (Chlorophyta) in nearshore water and beach sand of Lake Michigan

Each summer, the nuisance green alga Cladophora (mostly Cladophora glomerata) amasses along Lake Michigan beaches, creating nearshore anoxia and unsightly, malodorous mats that can attract problem animals and detract from visitor enjoyment. Traditionally, elevated counts of Escherichia coli are presumed to indicate the presence of sewage, mostly derived from nearby point sources. The relationship between fecal indicator bacteria and Cladophora remains essentially unstudied. This investigation describes the local and regional density of Escherichia coli and enterococci in Cladophora mats along beaches in the four states (Wisconsin, Illinois, Indiana, and Michigan) bordering Lake Michigan. Samples of Cladophora strands collected from 10 beaches (n = 41) were assayed for concentrations of E. coli and enterococci during the summer of 2002. Both E. coli and enterococci were ubiquitous (up to 97% occurrence), with overall log mean densities (+/- standard errors) of 5.3 (+/- 4.8) and 4.8 (+/- 4.5) per g (dry weight). E. coli and enterococci were strongly correlated in southern Lake Michigan beaches (P < 0.001, R(2) = 0.73, n = 17) but not in northern beaches (P = 0.892, n = 16). Both E. coli and enterococci survived for over 6 months in sun-dried Cladophora mats stored at 4 degrees C; the residual bacteria in the dried alga readily grew upon rehydration. These findings suggest that Cladophora amassing along the beaches of Lake Michigan may be an important environmental source of indicator bacteria and call into question the reliability of E. coli and enterococci as indicators of water quality for freshwater recreational beaches.     

Use ofCladophora glomerata to monitor heavy metals in rivers

Methods were developed for the use ofCladophora glomerata to monitor heavy metal concentrations in flowing waters. At least under conditions without marked fluctuations in ambient metal concentration, there was no detectable difference in the metal concentrations of young plants between terminal 2-cm lengths of filament and whole plants. In order to establish the relationship between metal concentration in plant and that in water, 60 algal and water samples were analyzed from sites in northern England for Fe, Cu, Zn, Cd and Pb. Other environmental variables were measured at the time in order to assess their influence on metal accumulation. There were highly significant correlations for each of the five metals between concentrations in alga and water. The regression equations relating metal in alga to metal in water permit an unknown environmental metal concentration to be estimated from the algal concentration. Multiple stepwise regression analyses were used to indicate environmental factors which may influence metal accumulation; for instance, Fe appears to have a positive influence on Cu accumulation. In generalCladophora accumulates much less metal than bryophytes, but the slope relating metal in alga to metal in water is steeper, particularly for Pb. This means thatCladophora is especially useful where there is a need for a sensitive indicator of differences between sites or sampling occasions.     

SOME FACTORS IN THE COMPETITION OR ANTAGONISM AMONG BACTERIA, ALGAE, AND AQUATIC WEEDS

Field observations of changes in the populations of aquatic weeds and phytoplankton have confirmed that aquatic weeds have antagonistic activity toward phytoplankton. Nutritional studies in the laboratory indicate that cultures of the aquatic weeds, Myriophyllum sp., Ceratophyllum sp., and duckweed (Lemma minor L.); liquid cultures of barley (Hordeum vulgare L., Dickson variety); and cultures of the filamentous green algae, Cladophora sp. and Pithophora oedogonium (Mont.) Withrock, will remain relatively free of epiphytes or competing phytoplankton if the cultures are nitrogen-limited. Field observations of Cladophora sp. have confirmed that the growth of epiphytes on the Cladophora is related to conditions of surplus available nitrogen compounds. It is proposed that this antagonistic activity may be due to a “nitrogen sink” effect in which the aquatic weeds or filamentous green algae prevent the growth of contaminating algae by competition for the limited nitrogen compounds available. However, the presence of bacteria-sized organisms which have selective toxicity to certain algae indicates that perhaps multiple factors exist. Discussed are the ecological implications of associations of certain algae with bacteria that have selective toxicities for other species of algae under certain environmental conditions such as nitrogen-limited growth.     

The food-web of theCladophora-belt fauna

Summary 1. The species composition of the fauna in theCladophora glomerata belts of the Baltic sea has been studied quantitatively.2. Examples are presented to illustrate composition and density of the epiphytic diatom flora.3. The dry weight ofCladophora glomerata was determined with the aid of length measurements under a microscope. It amounts to 0.25 mg per 1000 mm length of alga filaments, and to 15.9 mg for a tuft with a total surface area of 1 dm².4. The productivity ofCladophora glomerata was calculated. It amounts to 3105 m alga filaments per dm² per month.5. The following biomasses per dm² rock surface have been estimated:Cladophora (dry weight): 0.78 g, diatoms (dry weight): 1.15 g, animals (number of individuals): 12 544.6. The fauna of theCladophora-belt has been subdivided according to feeding types.7. Some herbivores have been studied in laboratory experiments. The epiphytic diatoms are important for survival of the first postmarsupial stages of the isopodIdotea baltica as well as for maximum growth rates of the gastropodHydrobia ulvae and chironomid larvae.8. The daily consumption ofCladophora-filaments has been determined for juveniles of the isopodIdotea baltica and the amphipodGammarus oceanicus by microscope examinations of faecal pellets.9. The diatom diet of the rotiferProales reinhardti has been listed according to genera or species. Among the animals living in theCladophora-belt,P. reinhardti attains the highest numbers of individuals.10. Examples of food-chains within theCladophora community are presented.

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Die Nahrungskette der Fauna derCladophora-Zone

Kurzfassung In der Ostsee bildet die GrünalgeCladophora glomerata große, gürtelförmige bestände in Ufernähe. Diese Bestände und ihre Fauna sind für die ökologischen Verhältnisse in der Ostsee von großer Bedeutung. Es wurde daher das Artengefüge dieser Fauna analysiert und Trockengewichtsbestimmungen anC. glomerata durchgeführt. Die Produktivität dieser Alge beträgt 3105 m Algenfilamente pro Quadratdezimeter pro Monat (mittleres Trockengewicht eines 1000 mm langen Algenfilamentes: 0,25 mg). Pro Quadratdezimeter Felsenoberfläche ergeben sich folgende Werte für die Hauptorganismengruppen: Trockengewicht fürCladophora: 0,78 g, für Diatomeen: 1,25 g; Anzahl Tiere: 12 544 Individuen. In Laboratoriumsexperimenten konnte nachgewiesen werden, daß epiphytische Diatomeen derCladophora für die ersten postmarsupialen Stadien des IsopodenIdotea baltica lebensnotwendig und für den GastropodenHydrobia ulvae sowie für Chironomidenlarven zur Erzielung maximaler Wachstumsraten erforderlich sind. Der tägliche Konsum anCladophora-Filamenten wurde für jungeIdotea baltica undGammarus oceanicus an Hand der ausgeschiedenen Faeces ermittelt. Die Nahrungskette innerhalb der Fauna derCladophora-Zone wird an Hand von Beispielen illustriert.

     

A comparison of attack rates in a native and an introduced population of the parasitoid Cotesia glomerata

The attack rate of a population of the braconid parasitoid Cotesia glomerata, introduced into the USA over 100 years ago as a parasitoid of Pieris rapae, was compared with that of a native British population, which normally attacks P. brassicae, and with that of a P. rapae specialist, Cotesia rubecula. British C. glomerata attacked P. brassicae at a much higher rate than it attacked P. rapae. In comparison with British C. glomerata, C. rubecula showed a higher attack rate with P. rapae. American C. glomerata attacked P. rapae at a slightly higher rate than did British C. glomerata, but not at as high a rate as that achieved by C. rubecula. The differences in each comparison were statistically significant. The possible causes of the differences between British and American C. glomerata attacking P. rapae are discussed. They may be due to genetic or environmental effects. Egg load did not appear to be a factor limiting the number of hosts parasitized under the conditions of the experiments.     

Plasticity and acclimation to light reflected in temporal and spatial changes of small-scale macroalgal distribution in a stream

The small-scale distribution pattern of macroalgae in the river Ilm, in Germany was monitored. These patterns were then related to abiotic factors and tested to discover whether the distribution of the common macroalgae, Cladophora glomerata (L.) Kütz. and Vaucheria sp., was linked to differences in their photosynthetic plasticity. Cladophora glomerata revealed higher maximum photosynthetic electron transport rates after acclimation to high light (HL) compared with low light (LL) acclimated samples. By contrast, Vaucheria sp. did not acclimate to different growth light conditions. The photosynthetic performance of both algae also varied according to diurnal conditions. High light caused a reversible decrease of the dark-adapted quantum yield (F(v)/F(m)) in C. glomerata and a concomitant reversible decrease of the light-adapted quantum yield (DeltaF/F'(m)). In Vaucheria sp., F(v)/F(m) remained mostly unchanged over the day, whereas DeltaF/F'(m) decreased during the morning at low light. Photosynthetic pigments confirmed acclimational differences between the species. HL C. glomerata showed increased chlorophyll a:chlorophyll b ratios, and higher amounts of xanthophyll-cycle pigments compared with LL samples, whereas Vaucheria sp. did not reveal differences between the light treatments. While preferences for substrate size, water velocity, and depth are similar for C. glomerata and Vaucheria sp., the physiological responses to light conditions are different. It is concluded that light conditions significantly affect the small-scale spatial distribution of macroalgae and that fitness is enhanced in species with a higher plasticity in photosynthetic acclimation in unstable environments.     

EFFECTS OF WATER VELOCITY ON THE ARCHITECTURE AND EPIPHYTES OF CLADOPHORA GLOMERATA (CHLOROPHYTA)1

The architecture of the filamentous green alga Cladophora glomerata (L.) Kütz. and the composition of this alga's epiphytes [primarily the diatoms Epithemia turgida (Ehrenb.) Kütz., Epithemia sorex Kütz., and Cocconeis pediculus Ehrenb.] were examined in different velocity regimes. After transferring algal-bearing cobbles among velocities, the effects of changes in velocity were also examined. Cladophora branching pattern did not initially differ among slow, medium, and fast velocities, indicating that stable water velocities did not affect branching pattern. Two weeks after cobble transfer, Cladophora in fast velocity had fragmented more (i.e. had fewer filaments and fewer branch points per length of filament and had a higher percentage of unbranched filaments) than Cladophora in slow velocity. Fragmentation was greatest in tufts moved from slow velocity, suggesting velocity-associated differences in susceptibility to breakage. Epiphytic assemblage composition differed among slow, medium, and fast velocities and between locations on the filament (base and apex). Cocconeis pediculus dominated where exposure to high velocity was greater (filament apices in medium and fast velocities), whereas the Epithemia spp. dominated where lower velocities occurred (filament bases in all velocities and apices in slow velocity). Two weeks after the cobble transfer, the translocated diatom assemblages had changed and the original pattern of diatom distribution was restored.     

EFFECTS OF SUSPENDED SEDIMENT ON BIOMASS AND CELL MORPHOLOGY OF CLADOPHORA GLOMERATA (CHLOROPHYTA) IN THE COLORADO RIVER, ARIZONA

This study assessed changes in biomass, filament length, and cell morphology in Cladophora glomerata (L.) Kütz. along a suspended sediment gradient in the Colorado River below Glen Canyon Dam, Arizona. Suspended sediments ranged from 2.0 mg·L⁻¹ at Lees Ferry (Rkm 0.8) to 4.2 mg·L⁻¹ at Gorilla Island (Rkm 352). There was a 74% decrease in Cladophora biomass along the river transect through Grand Canyon National Park and a significant decrease in filament and cell length, but cell width increased. Similar changes in cell morphology occurred after 19 days when C. glomerata was transplanted from a low suspended sediment site (2.0 mg·L⁻¹) at Lees Ferry to a habitat with high suspended sediments (≥20.0 mg·L⁻¹). Cell length increased and cell width decreased when plants were transplanted back to the low suspended sediment habitat for 24 days. In situ studies with reduced light in the absence of suspended sediments showed no change in cell morphology. These in situ experiments imply that changes in cell morphology by C. glomerata in waters with high suspended sediments are adjustments in structural integrity to accommodate the abrasive force of suspended particles. Our study suggests that cell dimensions in Cladophora might be too plastic under varying environmental conditions to be used in taxonomic determinations.     

PHYLOGENETIC RELATIONSHIPS WITHIN CLADOPHORALES (ULVOPHYCEAE,CHLOROPHYTA) INFERRED FROM 18S rRNA GENE SEQUENCES,WITH SPECIAL REFERENCE TO AEGAGROPILA LINNAEI 1

The phylogenetic position of a freshwater green alga, Aegagropila linnaei (Cladophorales, Ulvophyceae), was investigated using nuclear 18S rRNA gene sequences. This alga has usually been called Cladophora aegagropila (L.) Rabenhorst or Cladophora sauteri (Nees ex Kütz.) Kütz. Based on morphology, it was formerly classified into the section Aegagropila or into the subgenus Aegagropila, together with several marine species of the genus Cladophora. This classification is not supported by the present phylogenetic analyses in which two very distinct Cladophorales clades are recognized. Aegagropila linnaei groups together in a well‐supported clade with Cladophora sp., Pithophora sp., Chaetomorpha okamurae, Arnoldiella conchophila, Wittrockiella lyallii, and Cladophora conchopheria. Aegagropila linnaei and its closely related species share some ultrastructural and biochemical characteristics, like pyrenoid structure, carotenoid composition, and cell wall composition. Freshwater species, included in the analysis, were located in two distantly related lineages, indicating that adaptation from a marine to a freshwater habitat has happened at least twice independently in the Cladophorales.     

Growth of enterobacteria on algal mats in the eastern part of the Gulf of Finland

Model experiments on a possibility that pathogenic enterobacteria Salmonella enteritidis (Gartneri) can grow on decaying algal mats with prevalence of the filamentous algae Cladophora glomerata (L.) Kütz were carried out. Samples of algal mats have been collected in the eastern part of the Gulf of Finland in the Baltic Sea. A bacterial culture of Salmonella enteritidis was placed into tubes containing samples of mats. The intensive growth of salmonella was noted in alga samples collected in the freshwater zone (salinity 0.2–1.5‰); growth was practically absent in the samples of algae collected in a zone with salinity 2–3‰, while salmonella remained viable in the control tubes with water without algae. The growth of coliform enterobacteria initially inhabited in the algal mats was discovered in all experiments. Studies carried out in 2009 show that the thickness of the algal mats in the costal zones of the Gulf of Finland reached 20 cm and their biomass reached a few tons per 1 km². These experiments showed that dead algal mats stimulate the growth of enterobacteria in the littoral zone of the Baltic Sea, especially in the freshwater part, and can promote the development of these pathogenic microorganisms.     

COMPETITIVE INTERACTIONS BETWEEN THE OPPORTUNISTIC MACROALGAE CLADOPHORA VAGABUNDA (CHLOROPHYTA) AND GRACILARIA TIKVAHIAE (RHODOPHYTA) UNDER EUTROPHIC CONDITIONS1

In a eutrophic embayment (Waquoit Bay, Massachusetts), Cladophora vagabunda (L.) van den Hoek occurs in thick (sometimes > 1 kg dry wt -m^?2), nearly monospecific unattached mats in deeper regions (2 m), whereas Grac-ilaria tikvahiae McLachlan is largely restricted to shallow (<1 m) areas. We explored these distribution patterns, investigating competitive interactions between these opportunistic species by varying the limiting resource, photon flux density (PFD), and species composition under conditions of N sufficiency in microcosms. Under lower biomass loadings, neither species showed a difference in growth rates in single- and mixed-species stands. With a 25% increase in initial biomass loading, Gracilaria tikvahiae had significantly higher growth rates under saturating PFD and consistently showed greater performance when grown in single-species rather than in mixed-species stands. While growth rate was 2×greater for C. vagabunda in single-species than in mixed-species stands at saturating PFD, this pattern was reversed under limiting irradi-ances. In mixed-species stands at high PFD (comparable to shallow regions of the bay), the growth rate of G. tikvahiae was over 4×higher than that of C. vagabunda. Cladophora vagabunda grew at a faster rate than G. tikvahiae only in the low PFD, mixed-species treatment. Results of this study suggest that the observed distributional patterns of these macroalgae are due in part to interspecific exploitative competition but that tolerance of low PFD by C. vagabunda has led to dominance of these species in distinctive regions of the embayment.     

Silicon,a required nutrient for Cladophora glomerata (L) Kütz. (Chlorophyta)

Summary Physiological and ultrastructural studies of unialgal cultures demonstrated that silicon is a required nutrient and a component of the cell walls of Cladophora glomerata. Addition of silicon promoted growth of the alga, and the addition of germanium, an analogue of silicon, inhibited growth of C. glomerata in culture. An electron-dense outer layer was a conspicuous part of the cell walls of filaments taken from silicon rich medium.Abbreviation SWE soil water extract     

Effects of an epiphytic alga on abundances of fish and decapods associated with the seagrass Zostera capricorni

During a field experiment to test effects of changes to leaf height and density of Zostera capricorni on associated fish and decapods, more than one-third of the substratum at some sites was covered by the epiphytic brown alga Giffordia mitchelliae. This paper reports apparent effects of the alga on the 13 most abundant species of fish and decapods, and interactions between effects of the alga and those due to height and density of the seagrass leaves. Abundances of three species were significantly lower, and those of two species were significantly greater where the alga occurred. There were interactions between effects of the alga and those of leaf height and/or density for another four species. In all four cases, when the alga had an effect, it was to decrease abundance. The effects of Giffordia were generally opposite to those reported for drift algae in seagrass habitats elsewhere. The lower abundances of seven species where algal cover was great are best explained by an existing model for seagrass habitats that predicts reductions in abundance of individuals when the ratio of plant material to substratum is very high.     

Growth inhibition by high light intensities in algae from lakes undergoing acidification

Blooms ofChrysochromulina breviturrita Nich. (Prymnesiophyceae) have been found to be restricted to lakes above pH 5.5 even though the alga is able to tolerate pH 4.0 in laboratory culture. A possible explanation is the increased transparency in acidifying lakes and a sensitivity ofC. breviturrita to high light intensities. A comparison was made withMougeotia sp., a filamentous green alga which co-occurs in moderately acidic lakes and has a similar pH tolerance range. This alga forms dense, floating mats or amorphous clouds in the upper littoral zone, where it would be exposed to full sunlight irradiances. In cultures ofC. breviturrita, prolonged exposures to 1600 μE · m⁻² · s⁻¹ (I₀′) resulted in reductions in cell yield which were dependent age at the onset of exposure to high light intensity. Only cultures exposed to high light intensities during late stationary phase were able to recover to control levels and no recovery occurred if these cultures were nitrogen deficient.Mougeotia was more tolerant of both high light intensity and nitrogen limitation during the recovery period. The inability ofC. breviturrita to recover from the effects of high light intensity during nitrogen deprivation may be particularly important in small, stratified lakes which are undergoing acidification. The slow rate of vertical circulation, and increasing transparency, would prolong exposure of the alga to the high irradiance levels of nutrient-deficient epilimnetic waters. This suggests that the geographic distribution ofC. breviturrita may be explained in part by the increasing light intensities in lakes undergoing acidification.     

绿球藻目的几个中国新记录属种

6个生境比较特殊而有趣的绿球藻目物种首次在我国发现,它们分别是生于土壤的香喇网绿藻(Dictyochloris fragrans Vischer ex Start),寄生于眼子菜叶片的浮萍绿点藻(Chlorchytrium lemmae Cohn.),气生种类—生长在樟树皮上的分层胶囊藻(Gloeocystis polydermatica(Kutz.) Hindak),与真菌共生形成地衣的土著共球藻(Trebouxia aboricola de Puymaly)和团集共球藻(Trebouscia glomerata(Waren) Ahmadjian),还有附生于一种刚毛藻(Cladophora sp.)细胞表面的伊乐外生藻(Ectogeron elodeae Dangeard)。除胶囊藻属(Gloeocystis)外,其它属均为中国新记录属。     

Seasonal variations in the growth and amino acid pattern ofCaulerpa prolifera (Foerskal) Lamouroux

The amino acid pattern — free and bound — ofCaulerpa prolifera plants was studied. Maximum values for the total free amino acids were observed during periods of minimum growth, while minimum values occurred during periods of maximum growth of the alga. The bound amino acids showed a reverse trend.     

UPTAKE AND RELEASE OF METHYLMERCURY-203 BY CLADOPHORA GLOMERATA1

Cladophora glomerata was exposed to CH₃²⁰³HgCl at concentrations of 10, 50, and 100 μg/liter of water. Formalin-killed alga was exposed to a concentration of 50 μg CH₃²⁰³HgCl/liter. Uptake was monitored at 2 and 12 hr, and days 1, 2, 4, 8, and 16. At the end of this period, the Cladophora was placed in uncontaminated water, and release of methylmercury was monitored at 1, 2, 4, 8, and 16 days. Sorption occurred at all concentrations, and the live algal material accumulated more methylmercury than the dead alga, at equal exposure concentrations. Accumulation of methylmercury by the live Cladophora peaked on or near the second day for all exposure concentrations, suggesting that the uptake rate was independent of methylmercury concentration in the water. Uptake was greatest at the 50 μg/liter exposure. Desorption was nominal during the 16-day release period. The mechanisms of methylmercury uptake by Cladophora are discussed.     

Seasonal succession of planktonic and epiphytic algae in a canal in Southern England

The standing crop of phytoplankton in a canal in southern England remained low during 1973 and 1974, seldom exceeding 5 × 10⁴ cells/1. Since phosphorus, nitrogen and silicon occurred abundantly in the water, competition with higher plants for some other substance must have limited development. Although the standing crop of epiphytic algae associated withNasturtium officinale andGroenlandia densa seemed to be limited by the number of attachment sites, this factor was of little importance in the case of algae attached toCladophora glomerata. Achnanthes minutissima v.cryptocephala was always predominant in the epiphytic assemblages, representing 50–8o% by numbers of the flora. The limited pool of predominant epiphytic taxa may have restricted the communities' ability to adapt to fluctuations in environmental conditions. The grazing of isopods, amphipods and molluscs probably never limited algal densities.