A new model for periphyton growth in running waters

A new model for biofilm growth is based on a logistic approach but accounts for detachment of the biofilm by the running water and the existence of a threshold point for growth. Above a critical current velocity, development of periphyton is not stable. A stability analysis shows the existence of a fold catastrophe in the model and the amplification of water velocity fluctuations by the algal biomass.     

First report of three benthic dinoflagellates,Gambierdiscus pacificus,G. australes and G. caribaeus (Dinophyceae), from Hainan Island,South China Sea

Species of the marine benthic dinoflagellate genus Gambierdiscus are the principal cause of Ciguatera fish poisoning. This genus has been recorded from tropical to temperate oceans, although Gambierdiscus species have rarely been found in Chinese waters. Our work revealed the morphological and genetic characteristics of three potentially toxic Gambierdiscus species observed in the temperate to subtropical waters of China. The fine thecal morphology was determined based on light microscopy and scanning electron microscopy analyses, and these species were also characterized by sequencing the D1–D3 and D8–D10 regions of the LSU rDNA. The morphological and genetic data indicated that these three Gambierdiscus species were G. pacificus, G. australes and G. caribaeus. This work provides the first report of these species in Chinese waters, which increases the known species distribution of this genus.     

Phenology of cryptomonads and the CRY1 lineage in a coastal brackish lagoon (Vistula Lagoon,Baltic Sea)

Cryptomonadales have acquired their plastids by secondary endosymbiosis. A novel clade—CRY1—has been discovered at the base of the Cryptomonadales tree, but it remains unknown whether it contains plastids. Cryptomonadales are also an important component of phytoplankton assemblages. However, they cannot be readily identified in fixed samples, and knowledge on dynamics and distribution of specific taxa is scarce. We investigated the phenology of the CRY1 lineage, three cryptomonadales clades and a species Proteomonas sulcata in a brackish lagoon of the Baltic Sea (salinity 0.3–3.9) using fluorescence in situ hybridization. A newly design probe revealed that specimens of the CRY1 lineage were aplastidic. This adds evidence against the chromalveolate hypothesis, and suggests that the evolution of cryptomonadales’ plastids might have been shorter than is currently assumed. The CRY1 lineage was the most abundant cryptomonad clade in the lagoon. All of the studied cryptomonads peaked in spring at the most freshwater station, except for P. sulcata that peaked in summer and autumn. Salinity and concentration of dissolved inorganic nitrogen most significantly affected their distribution and dynamics. Our findings contribute to the ecology and evolution of cryptomonads, and may advance understanding of evolutionary relationships within the eukaryotic tree of life.     

Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions

We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is built and can be transported to a temporary work space close to field sampling site(s) to facilitate rapid analysis. Cores are extruded into a portable glove bag, where they are sectioned and each 1-3 cm thick section (depending on core diameter) is sealed into 50 ml centrifuge tubes. Pore waters are separated with centrifugation outside of the glove bag and then returned to the glove bag for separation from the sediment. These extracted pore water samples can be analyzed immediately. Immediate analyses of redox sensitive species, such as sulfide, iron speciation, and arsenic speciation indicate that oxidation of pore waters is minimal; some samples show approximately 100% of the reduced species, e.g. 100% Fe(II) with no detectable Fe(III). Both sediment and pore water samples can be preserved to maintain chemical species for further analysis upon return to the laboratory.     

Distribution of aquatic yeasts — Effect of incubation temperature and chloramphenicol concentration on isolation

Fresh (river), estuarine, and marine waters in and along the coastline of Connecticut were cultured by the membrane filter technique at 20 and 37°C on a complex medium containing 0–1000 mg/L of chloramphenicol. Using counts on medium with 500 mg/L antibiotic as a base, ratios of total and pink yeast counts were recorded for other chloramphenicol concentrations at both temperatures for the waters sampled. Variable results were obtained; in general, both total and pink yeast counts decreased with increasing antibiotic levels, being most apparent at > 400 mg/L chloramphenicol. Medium without antibiotic and with 100 mg/L always produced baterial overgrowth. A total of 209 white yeasts were isolated from all platings; the genera Torulopsis, particularly T. Candida, and Candida were dominant with lesser numbers of Cryptococcus, Trichosporon, sporogenous genera, and Kloeckera. Most species isolated were found on media at all chloramphenicol levels. Comparisons were made of yeast distributions in these temperate waters with reports from other areas.Contribution No. 101 from the University of Connecticut Marine Research Laboratory.     

Location of Biomphalaria glabrata (Say) by miracidia of Schistosoma mansoni Sambon in natural standing and running waters on the West Indian Island of St. Lucia

Upatham E. S. 1973. Location of Biomphalaria glabrata (Say) by miracidia of Schistosoma mansoni Sambon in natural standing and running waters on the West Indian Island of St. Lucia. International Journal of Parasitology3: 289–297. The ability of S. mansoni miracidia to locate B. glabrata in natural ditches and streams was investigated. Miracidia located and infected snails at distances of 9–14 and 97-54 in horizontally in standing and running waters respectively. In running water, no infection occurred above a velocity of 13.11 $\text{cm}\text{sec}$. In both types of habitat, infection rates in snails increased with increasing levels of miracidia but decreased as the location of caged snails moved away from the miracidial point of entry. Laboratory experi- ments showed that the number of daughter sporocysts was proportional to the number of miracidia. Judging by the number of daughter sporocysts recovered only a small percentage of miracidia succeeded in locating and penetrating snails (6.8–13-7 % and 1.4–6.2 % in standing and running waters respectively). In standing water, infection may be inhibited by the limited ability of miracidia to move horizontally. In running water, the flow extends significantly the effective scanning capacity of the miracidia, giving them a better chance of coming into contact with snails, which is of importance in the epidemiology of schistosomiasis. Owing to a con- siderable wastage of miracidia and the higher relative efficiency of miracidia at lower densities in detecting snails, control measures such as chemotherapy or provision of safe water supplies designed to lower egg output and reduce contamination may not seriously influence transmission unless S. mansoni egg production or contamination is massively reduced.     

Application of multiple discriminant analysis on the analysis of the correlation between macrophyte vegetation and water quality in running waters of Central Europe

124 sections of water courses from Northwest Germany and 154 sections of water courses from Southern Germany were classified into ten groups with regard to water quality and physico-chemical water type. Vegetation data were transformed into a two-step scale. Using the 39 most frequent water plant species as predictor variables a stepwise multiple discriminant analysis was carried out.29 species proved to be suitable for optimal discrimination of the groups. Most of the species correspond to those to which a certain indicator value had already been adjudged, using other methods. Species number, which was also tested, was not taken into the analyses. The score of right predictions ranges between 70 and 85 per cent depending on the technique of analysis and the number of data. Totaly wrong predictions with regard to water quality, as well as to water type were not frequent. Some possibilities for an explanation of mispredictions were suggested with respect to the fact that a statical model will never immediately indicate changes in the investigated systems.Finally, an ordination of the groups was carried out. The position of the groups in the canonical discriminant space could partly be interpreted in terms of succession.

---

Zusammenfassung 124 Gewässerabschnitte aus Nordwestdeutschland (eigene Aufnahmen) sowie 154 Gewässerabschnitte aus Süddeutschland (nach Veröffentlichungen der Arbeitsgruppe Kohler) wurden nach der Gewässergüte und dem physiko-chemischen Gewässertyp in 10 Gruppen eingeteilt. Die Vegetation wurde in einer 2-teiligen Skala geschätz bzw. umgerechnet. Mit den 39 häufigsten Wasserpflanzenarten as Prädiktoren wurde eine schrittweise Multiple Diskriminanzanalyse durchgeführt.Es zeigt sich, daß 29 Arten geeignet sind, die Gruppen optimal zu trennen. Einigen dieser Arten war auch schon vorher mit Hilfe anderer Methoden ein Zeigerwert zugesprochen worden. Die Artenzahl wird nicht in die Trennung der Gruppen einbezogen. Die Trefferquote für die richtige Zuordnung schwankt zwischen 70 und 85% je nach Methode und Datenmenge. Absolute Falschzuordnungen (sowohl nach Gewässergüte als auch Gewässertyp) sind selten. Einige Möglichkeiten der Erklärung von Falschzuordungen werden angedeutet, unter Bezug auf die Tatsache, daß ein statisches Modell Veränderungen im System nicht sofort widerspiegeln kann.Abschließend wird eine Ordination der Gruppen durchgeführt. Die Lage der Gruppen im kanonischen Diskriminanzraum kann teilweise im Sinne einer Sukzession interpretiert werden.

     

Photosynthesis of Gelidium sesquipedale: effects of temperature and light on pigment concentration,C/N ratio and cell-wall polysaccharides

Tanymastix stagnalis is known from seven locations in Ireland. These range from small to large temporary water bodies. It was earlier shown that the best hatching and survival of eggs and young stages occurred in the presence of soil and at temperatures between about 10° and 15°. Some eggs hatched after one drying period, others after up to at least 4 drying and wetting periods. It was found from field observations that the habitat appeared after a minimum of 200 mm of rain in a 2-month period. This occurred on average more than once per year, mostly between June and February. A computer model was constructed using field data, and meteorological data (rainfall and temperature) covering 100 years, to decide how secure the organism was in two contrasting habitats. This showed that in both habitats there was little likelihood of extinction from metorological causes. There was, however, the possibility of destruction of the smaller habitats either through drainage or conversion to permanent ponds through compaction of the soil by heavy farm animals. The distribution and the possibility of harvesting the organisms is briefly discussed.     

Phytoplankton primary production in a eutrophic cooling water pond

The seasonal variation of phytoplankton photosynthesis was measured with ¹⁴C-method in a warmed ice-free pond in central Finland. Simultaneously with in situ measurements the photosynthesis was also measured in an incubator with different water temperatures and constant light (ca. 16 W m^–2). The total annual photosynthesis was 57.2 C m^–2 a^–1. The portion of the winter and spring production of the annual photosynthesis was 18.4%, that of the autumn production ws 17.4%. Thus 64.3% of the total annual phytoplankton photosynthesis occurred in the three summer months. The range of the daily integrated photosynthesis per unit area was 1.9—563 mg C m^–2d^–1. The photosynthetic rate per unit chlorophyll a varied in situ from 0.94 to 33.1 mg C (mg chl. a)^–1 d^–1. The highest value was measured in the beginning of July and the lowest in mid-January. The photosynthetic rate increased in situ exponentially with increasing water temperature. In the incubator the highest photosynthetic rate values were also found in July and August (at+20 °C) when the phytoplankton population was increasing and the minimum values occurred after every diatom maximum both in spring and autumn. Light was a limiting factor for photosynthesis from September to Mid-January, low water temperature was a limiting factor from late January through May. The efficiency of the photosynthesis varied between 0.1 and 0.7% of P.A.R. According to the incubator experiments the Q₁₀ values for the photosynthesis were 2.45 and 2.44 for the winter population between 1 and 10° C and for the summer population between 5 and 15° C, respectively, but the Q₁₀ values decrease at the higher temperatures. The main effect of the warm effluents on the yearly photosynthesis was the increase of production in spring months due to the lack of ice cover. However, the increase of total annual phytoplankton photosynthesis was only ca. 10–15%, because the water temperature was during the spring months below 10° C.