Some new and interesting ecological observations on desmids from the Province of Vojvodina (Northern Serbia)

A detailed qualitative investigation of the desmid community in the territory of the Province of Vojvodina (Northern Serbia, part of the Pannonian Plain) revealed a surprisingly high number of desmid taxa. Although most of the desmids were marked as rare, according to the results of physico-chemical analyses of water samples, several taxa were frequently recorded in habitats that are generally deemed unsuitable for desmids. The ecological characteristics of 18 desmid taxa, some of which known as acidophilic and/or oligotrophic, are briefly discussed. The unexpected presence of many desmid taxa is explained by assuming that their tolerance threshold to various physico-chemical parameters has changed considerably. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Diversity of desmids in three Thai peat swamps

Three peat swamps situated in the southern part of Thailand were investigated for their desmid flora in relation to a number of physical and chemical habitat parameters. Altogether, 99 species were encountered belonging to 22 genera. 30 species are new records for the Thai desmid flora. Laempagarung peat swamp showed the highest diversity (45 species), followed by Maikhao peat swamp (32 species) and Jud peat swamp (25 species). Despite its relatively low species richness, Jud swamp appeared to house a number of rare taxa, e.g., Micrasterias subdenticulata var. ornata, M. suboblonga var. tecta and M. tetraptera var. siamensis which can be considered Indo-Malaysian endemics. Differences in composition of the desmid flora between the three peat swamps are discussed in relation to environmental conditions. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Diatom Succession and Interaction in Littoral Periphyton and Plankton

Periphyton and plankton samples were collected at four littoral stations in a relatively shallow, eutrophic lake (Elk Lake, B.C., Canada) over a six month period from August 1967 to January 1968. The most abundant planktonic diatoms demonstrated a pattern of seasonal succession typical of temperate lakes, and all were present in the periphyton. This pattern was identical at all stations:Fragilaria crotonensis was dominant from August to October,Asterionella formosa in November and December, andMelosira italica (plusM. varians) in January.F. virescens, although never dominant, peaked in October. Periphyton communities were dominated byAchnanthes minutissima, Cocconeis placentula, F. crolonensis andF. virescens. Considerable station variation in successional patterns occurred over different exposure periods; station differences were least in those samples immersed for monthly intervals, and greatest in those immersed for a cumulative four-month period. Interaction between the phytoplankton and periphyton was illustrated by the occurrence of species common to both habitats. A decrease in cell numbers and percent abundance of these species in planktonic populations coincided with their increase in the periphyton, a relationship which appeared dependent on the breakdown of thermal stratification in November. For example, following turnover,F. crotonensis andA. formosa settled out of the plankton and correspondingly increased in percent abundance in the periphyton. This interdependence was less evident in the four-month samples, whereA. minutissima andC. placentula dominated throughout the entire period and appeared to out-compete the more typical planktonic components for diminishing substrate area. Species interaction or competition was accentuated as exposure duration and periphyton total cell standing crops increased and species diversity decreased, and appeared to account in part, for station differences in successional patterns.     

Feeding ecology of common carp (Cyprinus carpio L.) in a rice–fish culture system of the Apatani plateau (Arunachal Pradesh, India)

For two years (2002, 2003) selective feeding ecology of the common carp (Cyprinus carpio L.) has been studied in carp-integrated rice fields in Apatani Plateau of Arunachal Pradesh (India). Sampling strategy was based on the water depths in the fields and on the flood phases: early flood phase (June–July), mid flood phase (July–August), and late flood phase (September–October). In 2003 the water level was higher and therefore periphyton availability was better. This resulted in larger gut contents and better growth of the carp compared with 2002 when the water levels were lower. Gut contents analyses revealed a total of 60 food items of which 22 belonged to the Chlorophycea, 12 to the Cyanobacteria, 10 to the Bacillariophycea and 16 to several zooplankton taxa. With the progress of flood phases, the fish increased its feeding on periphyton food items; simultaneously, feeding on plankton items gradually declined. This was caused by the increasing periphyton availability on the rice-stems. Selective feeding on plankton and periphyton taxa was studied, selectivity changed with the flood phases. Periphytic Chlorophycea and Cyanobacteria, especially, were strongly positively selected. Generally, periphyton was the most important resource for the common carp in the rice fields.     

Desmids from ephemeral pools and aerophytic habitats from the Czech Republic

The distribution and ecology of desmids in wetland habitats in the Czech Republic were studied during 2003–2007. Samples were taken also from various aerophytic habitats and temporary pools thet had not been sufficiently studied before. Altogether 110 desmids taxa were found in 31 samples which were ordinated on the basis of their desmid species composition using a multivariate statistic method. The discussion focuses on the most interesting findings and on the factors that influence the distribution of desmids in different types of aerophytic habitats. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Diversity and ecology of desmids of peat bogs in the Jizerské hory Mts

The present study focuses on diversity and ecological preferences of desmids in peat bogs in the Jizerské hory Mts (Czech Republic). Altogether 76 desmid algae taxa have been recorded at 18 sites of the study area during our investigation in 2003–2006. Taxa Actinotaenium crassiusculum (De Bary) Teiling, Hyalotheca dissiliens var. tatrica Racib., Staurastrum avicula var. subarcuatum (Wolle) West & G. S. West, S. borgeanum Schmidle, S. simonyi var. semicirculare Coesel, Staurodesmus extensus var. isthmosus (Heimerl) Coesel, S. extensus var. vulgaris (Eichler & Racib.) Croasdale and S. spencerianus (Mask.) Teiling are new for the Czech Republic. In addition, several rare and remarkable taxa were also encountered. The species richness was relatively high in comparison to similar localities in the Czech Republic. Desmid distribution was influenced by pH and conductivity. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Desmids in mountain lakes of the subpolar Urals

The species composition of desmids was studied in eight mountain lakes of the Kozhim and Malyi Patok River basins in the “Yugyd Va” National Park (subpolar Urals, Russia). A total of 98 desmid taxa representing 13 genera belonging to 4 families were identified. Geographical and ecological analyses showed that the desmid flora is typical, with a predominance of cosmopolitan species, planktic-benthic forms, acidophilic and pH indifferent species, and halophobic to salinity indifferent species. The investigated lakes can be classified as pristine and in good ecological condition on the basis of their hydrochemical and algal biodiversity characteristics. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Actinodontum,a new genus of Desmidiaceae (Streptophyta,Viridiplantae) from tropical Africa

A new desmid genus, Actinodontum Alfinito et Coesel, is described from mountain areas of tropical Africa. The newly described genus differs from the allied genus Actinotaenium by the presence of marked teeth at the base of each semicell that alternate with those on the other semicell. Morphology of the type species, Actinodontum lomaense (Alfinito et Mazzoni) Alfinito et Coesel, is dealt with in much detail. Cosmarium basituberculoides Bourrelly et Couté and Cosmarium elgonense Kusel-Fetzmann are transferred to the new genus. The geographical distribution of the genus Actinodontum is discussed.     

Desmids (Chlorophyta,Zygnematophyceae) from the Girutiskis mire complex reserve (East Lithuania)

The desmid flora of the Girutiskis mire complex reserve in Lithuania, a Natura 2000 territory and a potential Ramsar site, was investigated for the first time. Despite being a relatively small area with homogenous ecological conditions and a narrow range of pH-values, some pattern in the distribution of desmid species was observed. The lowest number of species was observed in the highly acidic lakes that were surrounded by sub-shrub bogs, and the highest number in less acidic lakes that were surrounded by trembling bogs. A total of 78 desmid taxa were found of which 16 were first records for Lithuania. Almost half of the taxa were uniquely found at one site, and only 10% were classified as frequent. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Wisconsin desmids. I. Aufwuchs and plankton communities of selected acid bogs,alkaline bogs,and closed bogs

Data are presented for 28 acid bogs, five alkaline bogs, and 12 closed bogs in Wisconsin with respect to the summer composition of the aufwuchs and plankton ccommunities, the relative importance of desmids in these communities, and the structure of aufwuchs communities associated with different macrophyte hosts. Generic diversity of desmids is highest in acid bogs and lowest in alkaline bogs and generally is greater in the aufwuchs community than in the plankton community at a given site. Whenever it was present, the greatest diversity occurred in association with the macrophyte host Utricularia. Among lakes of a given type, relationships between the occurrence of desmid genera and parameters of the chemical environment were not apparent for either the aufwuchs or plankton communities. Similarly, no clear-cut distinctions occur in the desmid communities of the three lake types in terms of population densities and percentage contribution to the total population, but acid bogs tend to have a somewhat more prominent flora quantitatively. Statistically significant differences in desmid population densities from one host to another within a given lake did occur in lakes of all three types, and this suggests that the nature of the substrate can definitely influence community size and composition. Data for other algal groups are similarly treated, and brief comparisons of the mat and open water communities of alkaline bogs are included.     

Plant community ecology of Pinus sylvestris, an extirpated species reintroduced to Ireland

Plantation forests can make a significant contribution to the conservation of native biodiversity, especially where native forest cover is low. Ireland is used as a case study to explore the contribution to biodiversity made by stands of Pinus sylvestris (Scots pine), a reintroduced species. Despite its disputed native status, P. sylvestris is being widely planted in semi-natural habitats in Ireland. The associated vegetation communities have not previously been described and their conservation value is unknown. Baseline information is needed to inform conservation and forest management strategies. Botanical surveys were carried out at 20 plots of P. sylvestris-dominated woodland and scrub throughout the Republic of Ireland. Vegetation, structural and environmental data were recorded. Data were analysed using non-parametric and multivariate statistical techniques and a synoptic table was prepared. P. sylvestris was found to be a non-specialist in terms of its environmental tolerances. β diversity among plots was high while α diversity within plots was low to moderate. The plots surveyed contained 14.2% of the Irish native flora. There was a low level of constancy of species. Four reasonably well defined vegetation communities were identified. Soil pH, altitude and slope had important roles in partitioning these vegetation types and soil pH was positively correlated with species richness. P. sylvestris is well established, well integrated and naturalising in Irish semi-natural habitats. Some of the associated vegetation communities corresponded to habitats of international conservation importance. This research demonstrates that stands of P. sylvestris represent an important resource for Ireland’s native botanical and habitat diversity.     

Laboratory experiments on the impact of biofilms on the plankton of a large river

1. Benthic organisms can have a strong effect on the plankton in rivers, although normally only members of the macrofauna are considered as important consumers. In the present study we conducted experiments on four different dates (in December, March, June and September) to assess the potential role of periphytic heterotrophic flagellates (HF), ciliates and rotifers in the control of potamoplankton (bacteria, algae, HF and ciliates). 2. Natural periphyton was established on the walls of circular flow channels by exposing them to river water (River Rhine, Germany). The experimental channels (with periphyton) and control channels (without periphyton) were filled with riverine water and the increase rates of planktonic bacteria, algae, HF and oligotrich ciliates were determined for the two treatments. 3. The abundance of periphytic ciliates and rotifers at the beginning of the four experiments showed large differences with low values in December and March, and high values in June and September. Dominant potential consumers of plankton were the heterotrich ciliate Stentor sp. and bdelloid rotifers. 4. The rates of increase of planktonic algae, HF and ciliates were significantly smaller in the presence of periphyton compared with those in their absence. Significant interactions between the treatment (with and without periphyton) and the time of experiment were found for the planktonic HF and algae, indicating that the impact of the periphyton varied temporarily. The planktonic groups responded differently to the periphyton with the planktonic HF showing the highest loss rate. Significant differences were also found among the loss rates of different HF groups and different diatom size classes. 5. These laboratory experiments demonstrate that periphytic ciliates and rotifers are potentially important consumers of different planktonic groups. The quantitative impact of periphyton on plankton with respect to the selective feeding needs further attention.     

Rocks and clocks: linking geologic history and rates of genetic differentiation in anchialine organisms

The geologic history of a region can significantly impact the development of its flora and fauna, with past events shaping community patterns and evolutionary trajectories of species. In this context, islands are excellent “natural laboratories” for studying the fundamental processes of evolution due to their discrete geographical nature and dynamic geologic histories. An island system meeting these criteria is the Hawaiian Archipelago, which is ideal for testing how island geologic history influences the processes leading to population genetic variation and differentiation. One Hawaiian endemic whose evolutionary history is closely tied to the geology of the islands is the anchialine atyid shrimp Halocaridina, whose mitochondrial cytochrome oxidase I (COI) gene is hypothesized to be evolving at the rate of 20% per million years. To validate this rapid evolutionary rate, time since divergence estimates between geographically close, yet genetically distinct, populations were calculated for Halocaridina from anchialine habitats on the islands of Hawai’i, Maui, and O’ahu. On the younger (i.e., <1.5 million years) islands of Hawai’i and Maui, where all anchialine habitats occur in basalt, application of the Halocaridina molecular clock identified a strong correlation between levels of genetic divergence and the geologic age of the region inhabited by those populations. In contrast, this relationship weakened when similar analyses were conducted for Halocaridina from limestone anchialine habitats on the older (i.e., >2.75 million years) island of O’ahu. These results suggest geologic age, basin origin and/or composition are important factors that should be taken into consideration when conducting molecular clock analyses on anchialine flora and fauna as well as island populations in general.     

Distribution and seasonality of desmids in the Maarsseveen Lakes area

The desmid flora of mesotrophic Lake Maarsseveen I, eutrophic Lake Maarsseveen II, as well as the interconnecting broads was studied during the period 1987–1991. Seasonal perodicity of euplanktonicStaurastrum andCosmarium species in the two Maarsseveen lakes fitted the well-known general pattern of desmid abundance peaks in (late) summer time. The deviating seasonality of two euplanktonicClosterium species (C. aciculare andC. acutum var.variabile) could be related to special nutritional demands. The tychoplanktonic desmid flora encountered in the interconnecting system of peat pits and canals proved to be more diversified as the influence of nutrient-poor seepage on the habitat (appearing from conductivity, transparency and the occurrence of particular macrophyte species) was greater. The rare speciesEuastrum germanicum andHeimansia pusilla had been only incidentally recorded in The Netherlands. Hanny Kooyman-van Blokland untimely died at the age of forty, in March 1994.     

COMPOSITION OF EXTRACELLULAR POLYMERIC SUBSTANCES FROM PERIPHYTON ASSEMBLAGES IN THE FLORIDA EVERGLADES1

In wetland habitats, periphyton is a common component of open‐water areas with species assemblage determined by local water quality. Extracellular polymeric substances (EPS) secreted by algae and bacteria give structure to periphyton, and differences in EPS chemistry affect the functional roles of these polymers. The Florida Everglades provide a unique opportunity to study compositional differences of EPS from distinctive algal assemblages that characterize areas of differing water chemistry. Water conservation area (WCA)‐1 is a soft‐water impoundment; periphyton was loosely associated with Utricularia stems and amorphous in structure, with a diverse desmid and diatom assemblage, and varying cyanobacterial abundance. Extracellular polymers were abundant and were loosely cell‐associated sheaths and slime layers in addition to tightly cell‐associated capsules. The EPS were complex heteropolysaccharides with significant saccharide residues of glucose, xylose, arabinose, and fucose. Carboxylic acids were also prominent, while ester sulfates and proteins were small components. Structured, cohesive cyanobacteria‐dominated periphyton was observed in WCA‐2A, a minerotrophic impoundment, and filaments were heavily encrusted with calcium carbonate and detrital matter. EPS were primarily cell‐associated sheaths, and polymer residues were dominated by glucose, xylose, fucose, and galactose, with uronic acids also a significant component of the polymers. Principal components analysis revealed that periphyton community assemblage determined the monosaccharide composition of EPS, which ultimately determines a range of biogeochemical processes within the periphyton.     

Changes in phytoperiphyton community during seasonal succession: influence of plankton sedimentation and grazing by phytophages--Chironomid larvae

The investigation of seasonal changes in spatial structure of phytoperiphyton during succession was conducted at the lower reaches of Akulovsky water channel from April to August 2000. At the beginning of succession from April to June dominant forms were chain-forming diatoms and filamentous green algae, sedimented from plankton. Later, at the middle of June under increasing pressure of herbivorous, they were replaced by stretched unicellular diatoms and colonial cyanobacteria. In late June-August, when herbivorous predation was the most intensive, the relative abundance of typical periphytonic forms decreased while that of settled planktonic forms increased. The effect of planktonic algae sedimentation on periphyton composition was evaluated as similarity between phytoperiphyton and phytoplankton communities measured with Chekanovski--Sorensen index. The value of this index tends to decrease with the development of periphyton while showing some relation to intensity of herbivorous pressure. Minimal values of Chekanovski--Sorensen index were under moderate herbivorous density, whereas maximal values were observed in periods of extremely high or low herbivorous density.     

SEASONAL DIFFERENCES IN THE TEMPERATURE RANGES OF GROWTH OF VIRGINIA ALGAE1

One hundred and fifteen clonal, unialgal strains were isolated and tested for their ability to grow over a range of temperatures from 2 to 40° C. Responses of 63 strains isolated from habitats that were 6° C when sampled and 52 strains isolated from habitats that were 20° C when sampled showed trends toward increasing adaptation to cold or warm temperatures commensurate with their seasonal in situ temperatures. Based on temperature-growth responses alone, 24% of the plankton isolates and 17% of the periphyton isolates could be perennial within the natural habitats. At 5° C, 56% of the warm water plankton isolates and 48% of the warm water periphyton isolates were incapable of growth and, therefore, probably could not be important components of the winter algal community. Likewise at 25° C, 25% of the cold water plankton isolates and 13% of the cold water periphyton isolates were incapable of growth. Thus, temperature alone probably is an important variable regulating seasonal changes in algal community structure. Pollution of these habitats by a thermal enrichment averaging + 5° C year-round could effect a pronounced change in algal species composition because many more taxa could be perennial and more taxa would be incapable of growth during naturally warm periods.     

Short term changes in pore water chemistry in river sediments during the early colonization by <Emphasis Type="Italic">Vallisneria spiralis</Emphasis>

Benthic consumers influence stream ecosystem structure and function, but these interactions depend on environmental context. We experimentally quantified the effects of central stoneroller minnows (Campostoma anomalum (Rafinesque) and Meek’s crayfish (Orconectes meeki meeki (Faxon)) on benthic communities using electric exclusion quadrats in Little Mulberry Creek before (June) and during (August) seasonal stream drying. Unglazed ceramic tiles were deployed in June and August to measure periphyton and invertebrate abundance, and leafpack decomposition and primary production were also measured in August. Relationships between stoneroller and crayfish density and the size of consumer effects were evaluated with multiple linear regression models. Average chlorophyll a abundance was greater on exposed than exclusion tiles in August, but not in June. Sediment dry mass, periphyton ash-free dry mass (AFDM), and chironomid densities on tiles did not differ among treatments in either period. Leaf packs decayed faster in exposed than exclusion treatments (k _exposed = 0.038 ± 0.013, k _exclusion = 0.007 ± 0.002), but consumer effects were stronger in some pools than others. Leafpack invertebrate biomass and abundance and tile primary productivity did not differ among treatments. Consumer effects on chlorophyll a were related to crayfish and stoneroller density, and effects on chironomid density were related to stoneroller density. These results contrast with a previous exclusion experiment in Little Mulberry Creek that demonstrated strong consumer effects. The influence of stream drying on consumer effects appears to have been reduced by strong spates, underscoring the importance of conducting multi-year studies to determine the magnitude of variability in ecological interactions.     

Geographical distribution pattern and interisland movements of Orii’s flying fox in Okinawa Islands, the Ryukyu Archipelago, Japan

The study of mobile animals such as flying foxes in insular habitats involves clarifying the population status on each island and determining the factors affecting movement patterns among the islands in their distributional range. We visited 25 of the Okinawa Islands and documented the number of Orii’s flying foxes Pteropus dasymallus inopinatus from August 2005 to May 2006. We also conducted a monthly road census on the main island (Okinawa-jima Island) and six adjacent islands from June 2006 to January 2007 and counted the number of fruit-bearing trees of the bats’ four main food plants. The results of classification and regression tree analysis suggested that distance from the main island was a primary factor in determining the distribution pattern and population size of this flying fox, whereas island area, number of plant species, and food availability did not directly affect population size. The number of flying foxes on each island tended to decrease with an increase in distance from the main island; no flying foxes existed on islands >30 km away from the main island. On the other hand, the results of the monthly census showed that the population size on each island fluctuated seasonally. Individuals may move between islands in response to seasonal changes in food availability. In conclusion, the distribution and abundance of Orii’s flying foxes in the Okinawa Islands may be determined by the rate of immigration/emigration, depending on each island’s distance from the main island. Seasonal changes in food availability may act as a trigger for interisland movement, but that movement may be restricted by island connectivity.     

Diet composition and foraging activity of <Emphasis Type="Italic">Pipistrellus pygmaeus</Emphasis> in a floodplain forest

In 2000–2002 bat droppings were collected under the emerging crevice of a nursery colony of Pipistrellus pygmaeus. The locality was situated in a floodplain forest at the confluence of the Dyje and Morava rivers (S Moravia, Czech Republic). In total, 27 samples (20 pellets in one sample) of droppings were used to analyze prey remains. In the diet, 40 taxonomic groups of invertebrates were found. As expected, small dipteran insects were the main food item in which Nematocera dominated. Besides Chironomidae and Ceratopogonidae also a high percentage of nematoceran eggs were recorded. Surprisingly, a relatively high percentage of Brachycera was recorded. Further frequent prey items belonged to the orders of Trichoptera, Hymenoptera, Coleoptera and Sternorrhyncha. A heterodyne bat detector was used to follow foraging activity of P. pygmaeus on line transects in forest and water habitats in the vicinity of the colony. A significant decrease in foraging activity over water habitats and in forest sites during the late pregnancy (mid-May — early June) and an increase during the lactation and post-lactation periods (mid-June — early August) were found. Changes in the frequency of occurrence of Chironomidae, Neuroptera, Trichoptera, Aphidinea and Simuliidae were correlated with the bats’ foraging activity.