Epiphytic Algal Community Research Articles

Present-day characteristics of phytoplankton, microphytobenthos and phytoepiphyton of the Kaniv Reservoir

The paper studies quantitative diversity and dominant complexes of phytoplankton, microphytobenthos and phytoepiphyton in lotic and lentic biotopes within the Kaniv Reservoir in summer seasons of 2017–2022, considers their association with some abiotic variables, assesses the trophic state, information diversity according to Shannon’s index and water quality. The cell count of planktonic algae varied within 2780–124155 thous. cells · dm–3, biomass – 0.631–11.636 mg · dm–3, benthic algae – 390–13874 thous. cells · 10 cm–2 and 0.162–2.651 mg mg · 10 cm–2, epiphytic algae – 50–680 thous. cells mg · 10 cm–2 and 0.050–1.679 mg · 10 cm–2 respectively. In lotic biotopes the phytoplankton cell count was higher than in lentic biotopes due to algal inflow from the Kyiv Reservoir and tributaries. The structural organization of phytoplankton and microphytobenthos is represented by oligodominant complexes of Cyanobacteria – Bacillariophyta and Bacillariophyta – Cyanobacteria respectively, and phytoepiphyton – by monodominant complex of Bacillariophyta. The necessity to distinguish dominant complexes according to cell count and biomass has been proven. The dominant complexes of algal communities clearly divide into three clusters (for plankton, benthos and epiphyton), and each of them – into two clusters (for lotic and lentic biotopes). The Sorensen similarity between phytoplankton and microphytobenthos was higher than between phytoplankton and phytoepiphyton, which can be explained by sedimentation of planktonic forms on the bottom under different ecological conditions. High cell count and biomass, diverse dominant complex of algal communities depend upon some abiotic variables (solar radiation, photic layer thickness, water temperature in summer, nutrient content). According to phytoplankton the trophic state of the Kaniv Reservoir is assessed as eutrophic–polytrophic, and according to contour algal communities – as oligo-mesotrophic–mesotrophic. This difference complies with the “alternative stable states” theory. That is, in summer the water reservoir is in “turbid state”, when planktonic Cyanobacteria grow intensively, screen the water surface and suppress the photosynthesis of benthic and epiphytic algal communities. The water quality of the Kaniv Reservoir is within the 1st–3rd classes (clean–satisfactory clean waters), there are no point of diffuse sources of water pollution, which mainly coincides with retrospective data.

Effects of Enrofloxacin on the Epiphytic Algal Communities Growing on the Leaf Surface of Vallisneria natans.

Enrofloxacin (ENR) is a member of quinolones, which are extensively used in livestock farming and aquaculture to fight various bacterial diseases, but its residues are partially transferred to surface water and affect the local aquatic ecosystem. There are many studies on the effect of ENR on the growth of a single aquatic species, but few on the level of the aquatic community. Epiphytic algae, which are organisms attached to the surface of submerged plants, play an important role in the absorption of nitrogen and phosphorus in the ecological purification pond which are mainly constructed by submerged plants, and are commonly used in aquaculture effluent treatment. Enrofloxacin (ENR) is frequently detected in aquaculture ponds and possibly discharged into the purification pond, thus imposing stress on the pond ecosystem. Here, we performed a microcosm experiment to evaluate the short-term effects of pulsed ENR in different concentrations on the epiphytic algal communities growing on Vallisneria natans. Our results showed an overall pattern of “low-dose-promotion and high-dose-inhibition”, which means under low and median ENR concentrations, the epiphytic algal biomass was promoted, while under high ENR concentrations, the biomass was inhibited. This pattern was mainly attributed to the high tolerance of filamentous green algae and yellow-green algae to ENR. Very low concentrations of ENR also favored the growth of diatoms and cyanobacteria. These results demonstrate a significant alteration of epiphytic algal communities by ENR and also spark further research on the potential use of filamentous green algae for the removal of ENR in contaminated waters because of its high tolerance.

Invasion of water hyacinth and water lettuce inhibits the abundance of epiphytic algae

AbstractAimThe invasion of exotic macrophytes causes native biodiversity loss in aquatic ecosystems of China. However, the influence of invasive free‐floating macrophytes on epiphytic algal communities has rarely been reported, especially in comparison with those of native free‐floating macrophytes.RegionSouthern China.MethodsWe investigated the interrelationship between epiphytic algal communities on the roots of three free‐floating macrophytes [two invasive species (Eichhornia crassipes and Pistia stratiotes) and one native species (Hydrocharis dubia)] and environmental factors in 40 natural freshwater ecosystems throughout southern China. We also tested the relationship between allelochemicals from the macrophytes and epiphytic algae. A mesocosm experiment was conducted to verify the discoveries of the field investigation.ResultsThe abundance of epiphytic algae on the invasive macrophytes was lower than that on the native species in the field investigation and mesocosm experiment. Macrophyte traits were the main factor explaining the epiphytic algal abundance in both the field investigation and mesocosm experiment. In linear models, the slopes of epiphytic algal abundance were lower across gradients of native macrophyte biomass and coverage than across gradients of invasive macrophyte biomass and coverage. The allelochemical contents secreted by the invasive macrophytes were significantly higher than those secreted by the native species. The composition of allelochemicals was another factor that drove the decrease in epiphytic algal abundance. Among the allelochemicals, organic acids and alkaloids were abundant.Main ConclusionsThe inhibitory effect of two invasive free‐floating macrophytes on epiphytic algae is stronger than that of the native macrophyte H. dubia. The main reason for this finding is that the invasive macrophytes have greater biomass and occupied more space, resulting in greater limitations on spatial niches and resources. Moreover, invasive macrophytes release more allelochemicals than native macrophytes, leading to stronger inhibitory effects on epiphytic algae.

Fairy ring disease affects epiphytic algal assemblages associated with the moss Sanionia uncinata (Hedw.) Loeske (Bryophyta) on King George Island, Antarctica.

Since the nineteenth century, a ring-forming disease attacking Antarctic mosses has been reported. However, to date, only the effects on the mosses themselves are known. In this study, we used DNA metabarcoding to investigate the effects on the moss epiphytic algal community at different stages of disease progression. As the disease progressed, algal species richness decreased, although overall abundance was not significantly affected. Prasiolales appeared unaffected, whereas Ulotrichales were more sensitive. Trebouxiales dominated the advanced disease stage, suggesting a possible benefit from the disease, either through the elimination of competition or creation of new niches. Infection is responsible for moss death, leading to habitat loss for other organisms, but pathogenic effects on algae cannot be ruled out. Our data indicate that the disease not only impacts mosses but also other groups, potentially resulting in loss of Antarctic biodiversity. This study provides the first report of the disease effects on epiphytic algal communities of Antarctic bryophytes.

Community composition and correlations between bacteria and algae within epiphytic biofilms on submerged macrophytes in a plateau lake, southwest China

Epiphytic biofilms are complex matrix-enclosed communities comprising large numbers of bacteria and algae, which play an important role in the biogeochemical cycles in aquatic systems. However, little is known about the correlations that occur between these communities or the relative impact of environmental factors on their composition. In this study, epiphytic biofilms on three different aquatic plants were sampled in a typical plateau lake (Caohai, southwest China) in July and November of 2018. Bacterial diversity was assessed using Miseq sequencing approaches and algal communities were assessed using light microscopy. Gammaproteobacteria (54.64%), Bacteroidetes (17.50%) and Firmicutes (13.99%) were the dominant bacterial taxa and Chlorophyta (47.62%), Bacillariophyta (28.57%) and Euglenophyta (19.05%) were the dominant algae. The alpha diversity values of the epiphytic bacterial and algal communities were greater during the macrophyte decline period (November) than during the growth period (July). Microbial community composition was significantly affected by abiotic factors (water temperature, NH4+, pH or TP) and biotic factors (algae or bacteria). Interestingly, in July and November, the epiphytic algal community dissimilarity was stronger than that observed for bacterial community dissimilarity, suggesting that bacterial community dissimilarity may increase more slowly with environmental change than algal community dissimilarity. Furthermore, association network analysis revealed complex correlations between algal biomass and bacteria phylotype, and that 67.83% of correlations were positive and 32.17% were negative. This may indicate that facilitative correlations between algae and bacteria are predominant in epiphytic biofilms. These results provide new information on algal–bacterial correlations as well as the possible mechanisms that drive variations in the microbial community in epiphytic biofilms in freshwater lakes.

Effects of Water Quality Adjusted by Submerged Macrophytes on the Richness of the Epiphytic Algal Community

Submerged macrophytes and epiphytic algae play significant roles in the functioning of aquatic ecosystems. Submerged macrophytes can influence the epiphytic algal community by directly or indirectly modifying environmental conditions (nutrients, light, etc.). From December to June of the following year, we investigated the dynamics of the dominant winter species Potamogeton crispus, its epiphytic algae, and water quality parameters in the shallow Liangzi Lake in China. The richness of epiphytic algae had a trend similar to that of P. crispus coverage, which increased in the first four months and then decreased in the following three months. The structural equation model (SEM) showed that P. crispus affected the richness of epiphytic algae by reducing nutrient concentrations (reduction in total organic carbon, total nitrogen and chemical oxygen demand) and enhancing water transparency (reduction in turbidity and total suspend solids) to enhance the richness of epiphytic algae. The results indicated that high amounts of submerged macrophyte cover can increase the richness of the epiphytic algal community by changing water quality.

Distribution of epipelic algae and related environmental nutrients in Taihu Lake, revealed by HPLC analysis

Epipelic algal biomass and composition (determined by HPLC pigment analysis) and related environmental nutrients were investigated in a phytoplankton-dominated area (Meiliang Bay), a macrophyte-dominated area (East Taihu Lake) and a transition zones (Gonghu Bay) in a shallow eutrophic freshwater lake (Taihu Lake, eastern China). Surface sediment samples were collected at 11 sampling sites in April and August 2016. Average epipelic algal biomass for Meiliang Bay, Gonghu Bay and East Taihu Lake was 6.5, 4.9 and 4.6μg chlorophyll (Chl)-ag–1 sediment respectively in April, and 3.8, 7.4 and 2.7μg Chl-ag–1 sediment respectively in August. The maximum biomass of epipelic algae appeared at the G1 sampling site (9.6μg Chl-ag–1 sediment) in August, whereas the minimum biomass of epipelic algae appeared at the E4 sampling site (1.7μg Chl-ag–1 sediment). Pigment (fucoxanthin, zeaxanthin and Chl-b) to Chl-a ratios indicated that epipelic algae were primarily diatoms, secondarily cyanobacteria and lastly green algae in Taihu Lake. Epipelic algae were significantly correlated with total nitrogen in the water and total phosphorus in the sediment (P<0.05), except for green algae. In general, using pigment as an indicator revealed that the epiphytic algal community varied over time and space. The distribution of variations in epipelic algae was related to the heterogeneity of environmental factors.

Comparative study of epiphytic algal communities on Typha latifolia L. and Phragmites australis (Cav.) Trin. ex Steud in the shallow Gala Lake (European Part of Turkey)

The aim of this study was to determine the species composition, biodiversity and, relative abundance of epiphytic algae and their relationship with environmental variables on Typha latifolia and Phragmites australis at Lake Gala (National Park). Epiphytic algae were gathered monthly by collecting aquatic plants between March 2014 and November 2014. In the epiphytic flora were a total of 133 taxa were identified, 107 taxa were identified on T. latifolia and 96 were discovered on P. australis. While the mean species richness, species diversity and evenness values of the algae identified on T. latifolia were 46, 1.85 and 0.51 respectively, these values were respectively 43, 1.51 and 0.43 on P. australis. While diatoms were generally dominant, other dominant groups in the epiphytic flora included green algae and blue-green algae. The algae that had the highest relative biovolume on T. latifolia were Spirogyra affinis, Oscillatoria sancta and Gomphonema acuminatum, while the algae that had the highest relative biovolume on P. australis were Epithemia adnata, Oscillatoria sancta and Rhopalodia gibba. Results show that species composition of epiphytic algae was different, but diversity values were similar on all the macrophytes. The hydrological pulse is one of the most important factors determining the physical and chemical environment of the epiphytic algal community. It was found that some environmental factors were highly effective on community distribution in the epiphyton. Additionally, it was observed that some epiphytic algae species had a substrate preference between T. latifolia and P. australis.

Interaction between Phytoplankton and Epiphytic Algae in the Kaniv Water Reservoir (Ukraine)

The paper considers the patterns of interaction between algae relating to different ecological groups (phytoplankton and epiphytic algae) in the upper section of the Kaniv Water Reservoir (Ukraine). Phytoplankton and epiphytic algae have been shown to form the dynamic system, wherein phytoplankton makes an impact upon the epiphytic algal community structure, and, on the contrary, epiphytic algae in certain periods of the year can influence the phytoplankton structure. Several species were simultaneously present in both communities, and this was caused by: their habitat versatility, algae sedimentation from plankton to higher aquatic plant surface and transition of typically epiphytic species to plankton owing to hydrodynamic processes. The “phase opposition” was observed between phytoplankton and epiphytic algae: the maximal biomass of phytoplankton was recorded in summer, while that of epiphytic algae – in autumn. Such “phase opposition” is explained by different temperature optimums of dominant species and divisions in these communities, and also by shading of epiphytic algae by phytoplankton in case of intensive growth of the latter.

Interaction between Phytoplankton and Epiphytic Algae in the Kaniv Water Reservoir (Ukraine)

The paper considers the patterns of interaction between algae relating to different ecological groups (phytoplankton and epiphytic algae) in the upper section of the Kaniv Water Reservoir (Ukraine). Phytoplankton and epiphytic algae have been shown to form the dynamic system, wherein phytoplankton makes an impact upon the epiphytic algal community structure, and, on the contrary, epiphytic algae in certain periods of the year can influence the phytoplankton structure. Several species were simultaneously present in both communities, and this was caused by: their habitat versatility, algae sedimentation from plankton to higher aquatic plant surface and transition of typically epiphytic species to plankton owing to hydrodynamic processes. The “phase opposition” was observed between phytoplankton and epiphytic algae: the maximal biomass of phytoplankton was recorded in summer, while that of epiphytic algae – in autumn. Such “phase opposition” is explained by different temperature optimums of dominant species and divisions in these communities, and also by shading of epiphytic algae by phytoplankton in case of intensive growth of the latter.

Epiphyton alters the quantity and quality of radiation captured by leaves in submerged macrophytes

This study investigates the effects of the epiphyton and the leaf morphological and biochemical properties on the quality and quantity of radiation reflected from the adaxial leaf surface and radiation transmitted through the leaf tissue. The radiation in the range from 290nm to 800nm was analysed for submerged leaves of Potamogeton perfoliatus, Potamogeton lucens and Sagittaria sagittifolia. In all of these plant species, the epiphytic algal community was dominated by the diatom Cocconeis placentula. The presence of the epiphyton had more pronounced effect on the amount of transmitted light compared to the amount of reflected light. Most of the variability of the reflectance spectra was explained by the epiphyton dry mass at the adaxial surface (15%). Redundancy analysis to explain the variability of the transmittance spectra showed that the epiphyton layer at the abaxial surface of the leaves has a more important role than that at the adaxial surface, with 18% and 3% of the spectra variability explained, respectively. An additional 21% of the transmittance spectra variability was explained by the leaf carotenoid content. Removal of the epiphyton from the adaxial leaf surface resulted in a significant increase in the leaf reflectance along the spectra, with pronounced differences in the UV, violet and blue ranges. The transmittance spectra measured after removal of the epiphyton also showed a marked increase in the UV, violet and blue ranges. This demonstrates the important role of the epiphyton dominated by diatoms for the prevention of potential harmful effects of short-wave radiation.

Community structure of epiphytic algae on three different macrophytes at Acarlar floodplain forest (northern Turkey)

The aim of this study was to determine the species composition, biodiversity and, relative abundance of epiphytic algae and their relationship with environmental variables on three different macrophytes (Nymphaea alba, Ceratophyllum demersum, Typha latifolia ) at Acarlar Floodplain Forest (AFF). Epiphytic algae were gathered monthly by collecting aquatic plants between November 2011 and October 2012, except in winter when there were no plants. In this study, 67 taxa on N. alba, 66 taxa on C. demersum and 66 taxa on T. latifolia were identified as epiphytic algae. The mean value of species richness was 17, that of diversity was 1.5 and that of evenness was 0.54 for epiphytic algae on N. alba, 17, 1.1, and 0.39 on C. demersum, and 18, 1.64, and 0.56 on T. latifolia, respectively. Oscillatoria sp. and Komvophoron crassum (Vozzen) Anagnostidis and Komarek were the most abundant and consistent epiphytic algal species, occurring in high abundance on all macrophytes. Results show that species composition of epiphytic algae was different, but diversity values were similar on all the macrophytes. The hydrological pulse is one of the most important factors determining the physical and chemical environment of the epiphytic algal community. However, substrate type also affected the colonization by F. capucina, O. sancta, P. catenata, and L. truncicola more than the epiphytic algal seasonality.

Seasonal dynamics of the structure of epiphytic algal community on different substrates from a Neotropical floodplain

This study aimed at analyzing the structure of epiphytic algal community on aquatic macrophytes morphologically different and in distinct hydrological periods at a lentic environment (Pombas Lake) located in the Upper Parana River floodplain. In this study we tested the hypothesis that epiphyton richness, diversity, density, and composition, associated with submerged macrophytes are affected by hydrological dynamics and by habitat heterogeneity. The macrophytes used as substrates were Eichhornia azurea Kunth, an emergent macrophyte, and Egeria najas Planch, a submerged macrophyte. The samplings were performed quarterly in 2009, the species richness, diversity, density, and composition of the epiphytic algal community were evaluated. The species richness was not different between the substrates. Regardless of the evaluated substrate, the month of March had the highest species richness and diversity, especially of Desmids and Chlorophyceae. E. najas recorded the greater variation in abundance, compared with E. azurea. Bacillariophyceae, independent of the period and substrate, represented over 50 % of total density. The species composition was different among the periods, in which March and June (low water) were more similar and formed the group I, while September and December (high water) formed the group II. In summary, the hypothesis was accepted, since we verified that the hydrological dynamics of the floodplain is the direct controlling factor on structure of epiphytic algal community, and the substrate heterogeneity is the indirect controlling factor.

Effects of macrophyte architecture and leaf shape complexity on structural parameters of the epiphytic algal community in a Pampean stream

Habitat heterogeneity is one of the main factors determining distribution of organisms, and vegetation is of primary importance in shaping the structural environment in aquatic systems. The effect of macrophyte complexity on macroinvertebrates has been well researched; however, much remains to be revealed about the influence of complexity on epiphytic algae. Here, we used fractal dimension to study the effect of complexity at two scales, macrophyte architecture and leaf shape, on several parameters of the epiphytic algal community (number of individuals, biomass, taxon richness and diversity) in a Pampean stream. Four submerged macrophyte species with different complexities and associated algae were sampled in late spring, summer and autumn. Important differences were found in fractal dimension of the whole plant and leaves among macrophyte species. The particulate organic matter and chlorophyll a associated positively to leaf fractal dimension, but not to plant fractal dimension, partially supporting the hypothesis of a positive effect of macrophyte complexity on periphyton biomass. No association was found in fractal dimension with algal abundance, taxon richness or diversity. Complementary, a mesocosm experiment was performed with plastic imitations of different plant fractal dimensions. After four weeks, there were differences in chlorophyll a and autotrophy index between treatments that suggested a positive effect of complexity on autotrophic periphyton biomass. These results indicate that the well-known positive effect of macrophyte complexity on macroinvertebrates might be partially explained by a positive effect of complexity on periphyton biomass.

Depth-related variation in epiphytic communities growing on the brown alga Lobophora variegata in a Caribbean coral reef

Lobophora variegata is a dominant macroalga on coral reefs across the Caribbean. Over the last two decades, it has expanded its vertical distribution to both shallow and deep reefs along the leeward coast of the island of Curacao, Southern Caribbean. However, the ecological implications of this expansion and the role of L. variegata as a living substratum are poorly known. This study compared epiphytic algal communities on L. variegata blades along two depth transects (6–40 m). The epiphytic community was diverse with a total of 70 species of which 49 were found directly attached to L. variegata. The epiphytic community varied significantly between blade surface, depth and site. The greatest number of genera per blade was found growing on the underside of the blades regardless of site and depth. Filamentous red algae (e.g. Neosiphonia howei) were commonly found on the upperside of the blades over the whole depth gradient, whereas the underside was mainly colonized by calcifying (e.g. Hydrolithon spp., Jania spp., Amphiroa fragillissima), fleshy red algae (e.g. Champia spp., Gelidiopsis spp., Hypneaspinella) and foliose brown alga (e.g. Dictyota spp.). Anotrichum tenue, a red alga capable of overgrowing corals, was a common epiphyte of both blade surfaces. L. variegata plays an important role as a newly available substratum. Thus, its spread may influence other algal species and studies of benthic macroalgae such as L. variegata should also take into consideration their associated epiphytic algal communities.

Effects of habitat-modifying invasive macroalgae on epiphytic algal communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 400:87-100 (2010) - DOI: https://doi.org/10.3354/meps08391 Effects of habitat-modifying invasive macroalgae on epiphytic algal communities Emily Jones1,2,*, Carol S. Thornber1 1Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881, USA 2Bodega Marine Laboratory, University of California Davis, Bodega Bay, California 94923, USA *Email: emjones@ucdavis.edu ABSTRACT: Although invasive species can negatively impact communities via processes such as resource competition, they may also add new resources that facilitate the distribution and/or abundance of other organisms. In rocky intertidal systems, many benthic macroalgae compete for primary substrate, while providing secondary substrata to which sessile organisms can attach. Using field surveys and laboratory experiments, we investigated algal host–epiphyte dynamics in a New England rocky intertidal system. First, we compared the composition, abundance, richness, and diversity of epiphytes on 2 invasive macroalgal species, Codium fragile ssp. tomentosoides and Grateloupia turuturu, to 2 native macroalgal species, Chondrus crispus and Fucus vesiculosus. We found significant differences among epiphyte communities, as all macroalgal hosts supported different assemblages of species. While epiphyte richness and diversity were generally low on F. vesiculosus and G. turuturu year-round, they were low on C. crispus during the winter only. In contrast, epiphyte richness and diversity on C. fragile remained high throughout the year, suggesting that C. fragile plays an important role for supporting epiphytes during the cooler months. Second, we examined the relationship between epiphytes and a common herbivorous snail, Lacuna vincta. The abundance of juvenile L. vincta was positively correlated with 1 of the 2 most common epiphyte species, Neosiphonia harveyi. However, L. vincta showed a significant consumption preference for the other abundant epiphyte, Ceramium virgatum, in laboratory assays. Our results suggest that epiphyte facilitation by these invasive algal hosts is not only seasonally important for maintaining species richness and diversity, but may also provide both food and habitat for higher trophic levels. KEY WORDS: Invasive macroalgae · Epiphyte · Habitat-modification · Codium fragile · Grateloupia turuturu · Lacuna vincta Full text in pdf format PreviousNextCite this article as: Jones E, Thornber CS (2010) Effects of habitat-modifying invasive macroalgae on epiphytic algal communities. Mar Ecol Prog Ser 400:87-100. https://doi.org/10.3354/meps08391 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 400. Online publication date: February 11, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Invasive reed effects on benthic community structure in Lake Erie coastal marshes

We examined how dominance (% canopy cover) and invasion history of common reed, Phragmites australis, affected benthic macroinvertebrate diversity and density in 8 marshes along Lake Erie’s southern shoreline. We also compared macroinvertebrate densities among patches (0.25 m2) of reed, cattail (Typha spp.), and native flora (e.g., Sagittaria, Sparganium) and epiphytic algal communities on submerged stems of reed and cattail. Narrow-leaf cattail (T. angustifolia) is also a common invasive plant to these wetlands, but does not greatly change plant community composition or ecosystem conditions like reed. Macroinvertebrate diversity (Shannon–Weaver H′) was positively related to reed cover and was highest (4.6) in two marshes with ~35- and 5-year invasion histories. Shading from high reed cover increased H′-diversity, in part, by reducing the abundance of floating duckweed, which harbored many Hyalella azteca amphipods. Percent Ephemeroptera, Odonata, and Trichoptera was low to moderate across marshes, regardless of reed cover and invasion history. Macroinvertebrate density was not affected by reed cover or average plant stem density, and did not differ among plant types. However, epiphyton densities and % diatoms were greater on reed than on cattail, suggesting reed provides a better feeding habitat for microalgal grazers than Typha. Abundance rankings of common species in these diatom-dominated communities were also typically dissimilar between these plant types. Although % grazers was unrelated to epiphyton densities and % diatoms, grazer identity (snails) differed between natural and diked marshes, which had different microalgal food supplies. Our findings suggest that Phragmites does not necessarily adversely affect macroinvertebrate community structure and diversity and that invasion history alone has little effect on the H′-diversity–reed dominance relationship.

Seasonal Variation in the Biomass of Eelgrass (Zostera marina) and Epiphytic Algae in Two Eelgrass Beds around Namhae Island in Korea

Seasonal variation in the biomass of eelgrass (Zostera marina) and epiphytic algae in two eelgrass beds (Dongdae and Aenggang Bay) around Namhae Island was investigated throughout 2005. Shoot density and eelgrass biomass differed across months and locations. Peak shoot density occurred from April to August 2005, whereas eelgrass biomass was higher in July and August 2005. Shoot density as well as eelgrass biomass were higher in Dongdae Bay compared to Aenggang Bay. A total of 21 epiphytic algal species (4 Chlorophyta, 2 Phaeophyta, and 15 Rhodophyta) were collected, and dominant species included Polysiphonia japonica, Lomentaria hakodantensis, Symphyocladia latiuscula, Champia sp., and Heterosiphonia japonica. Seasonal variation in both the species composition and biomass of epiphytic algae was substantial: peak epiphytic algal biomass occurred in January and December 2005. We also observed high epiphytic algal biomass in the eelgrass bed of Dongdae Bay. Seasonal changes in the biomass of eelgrass and epiphytic algae were primarily influenced by water temperature, whereas those of the epiphytic algal community were also correlated with eelgrass (substrate) morphology and growth, the life cycle of epiphytic algae, and physical characteristics within eelgrass beds. The spatial variation of eelgrass density and biomass were also limited by sediment characteristics.

A Survey of Algal Epiphytes from Vallisneria americana Michx. (Hydrocharitaceae) in the Lower St. Johns River, Florida

Epiphytic algae may be responsible for a signifi cant amount of primary productivity in aquatic ecosystems, but also reduce available light, compete for nu- trients, and increase drag on their living substrates. A survey of the epiphytic algal community of the submersed aquatic macrophyte Vallisneria americana Michx. (Hydrocharitaceae) in the lower St. Johns River, FL was conducted over a 17-month period. A total of 122 infrageneric taxa were collected at four sites along a 93-km stretch of the river, yielding 32 diatoms (Bacillariophyta), 42 green algae (Chlo- rophyta), 45 blue-green algae (Cyanobacteria), 2 euglenoids (Euglenophyta), and 1 dinofl agellate (Pyrrophyta) taxa identifi ed over the study period. However, only diatoms and cyanobacteria were seen at all sampling dates, and only a Cocconeis sp. was identifi ed at all sites on all dates. This study provides baseline survey data of the epiphytic algal community in order to assess future anthropogenic effects.

Response of epiphytic algae to nutrient loading and fish density in a shallow lake: a mesocosm experiment

Studies on the effect of eutrophication on the ecology of shallow lakes, usually pay scant attention to changes within the epiphytic algal community, though the contribution of this to the ecosystem dynamics is transcendental. In order to test the influence of nutrient loadings and fish densities in the structure of algal epiphyton in a shallow lake, an experiment was performed using in situ mesocosms. Nutrient additions were related to significant decreases in the total epiphyton biovolume and that of bacillariophyceans and zygnematophyceans, but with increases in the abundance of cyanobacteria. The different response of algal groups at the higher nutrient concentrations (increases or decreases in their abundance and/or biovolume) can be related to their ecophysiological constraints such as different resistance to toxicant ammonium accumulation. Plant-associated macroinvertebrates numbers were positively correlated with total numbers of epiphyton. The presence of planktivorous fish enhanced the abundance and biovolume of all algal groups, except cyanobacteria. Fishes enhanced the abundance of plant-associated animals and of total epiphyton. Fish indirect effects (e.g., nutrients release) and their dietary particularities were among the factors that together with nutrients influenced epiphyton growth. The role of indirect effects of fishes and the importance of their dietary particularities are stressed as key factors to understand the processes controlling epiphyton ecology and the food web structure of shallow lakes.