Coccoid Algae Research Articles

Differences Among Coccoid Green Algal Communities in Minnesota and North Dakota Lakes

AbstractVery little is known about the diversity and distribution of freshwater unicellular coccoid green algae. The simple morphology and small size of these organisms make reliable identification extremely difficult. Current hypotheses suggest that species of coccoid algae are widely distributed, opportunistic organisms that are always present in aquatic systems. These hypotheses are based on the assumption that phytoplankton communities include only one or a few species of coccoid algae. We examined the diversity and distribution of green‐colored autosporic coccoid algae in Itasca State Park in Minnesota and Arrowwood National Wildlife Refuge in North Dakota using molecular techniques and light microscopy. Our preliminary results indicate a higher level of diversity of coccoid green algae than has been reported in regional flora. Contrary to current hypotheses, communities of coccoid green algae vary among the different lakes.

Diversity of Coccoid Algae in Minnesota and North Dakota Lakes

AbstractThe coccoid algae (a.k.a ‘little green balls’) are important primary producers in freshwater communities, but very little is known about their diversity. This lack of knowledge results from the extremely small size and simple morphology of these organisms, which makes identification by light microscopy essentially impossible. However, molecular techniques allow differentiation of taxa at various levels and can ultimately lead to species identification. We have isolated several hundred cultures of coccoid algae from lakes and ponds in Itasca State Park in north‐western Minnesota and Arrowwood National Wildlife Refuge in central North Dakota. Many of these isolates have been examined by light microscopy, 18S rDNA PCR–RFLP analysis, and 18S rDNA sequence analysis. In addition, some taxa with multiple isolates have been examined by rbcL and ribosomal RNA ITS sequence analysis. Our results indicate a high level of diversity, including possible new species of Chlorella, Muriella, Pseudomuriella and Mychonastes, among others. We will discuss the results of our analyses, including implications for identification of taxa and higher level systematics. Supported by National Science Foundation Grants DBI‐00703867, MCB‐0084188 and DEB‐0128952.

The effect of spectral composition of light on morphogenesis of green coccoid algae (Chlorophyta)

The effect of spectral composition of light on morphogenesis of green coccoid algae (Chlorophyta)

Diversity of coccoid algae in shallow lakes during winter

Very little is known about the distribution and diversity of freshwater unicellular coccoid algae, primarily because of the simple morphology and small size of these organisms, which make reliable identification extremely difficult. In this study, we examined the diversity of autosporic coccoid algae from under ice in the shallow lakes of Arrowwood National Wildlife Refuge, North Dakota. Coccoid algae were isolated from phytoplankton samples collected during three consecutive winters (1994–1997) at four sites in three lakes. Seventy-five isolates were examined by high-performance liquid chromatography analysis of photosynthetic pigments, specific polymerase chain reaction (PCR) primers, and PCR-restriction fragment length polymorphism of the 18S rDNA. Thirteen 18S rDNA types of coccoid Trebouxiophyceae, three types of coccoid Chlorophyceae and one type of coccoid eustigmatophyte were detected. One of the green algae was tentatively identified as Mychonastes homosphaera; the other green algae are probably undescribed species. These results indicate a much higher level of diversity in coccoid green algae than has been reported in regional floras.

Herbivory in an acid stream

SUMMARY 1. Spatial and temporal variation in the distribution and feeding of non-predatory macroinvertebrates was investigated in a first-order, acid stream in the Ashdown Forest, southern England. 2. Stonefly (Nemouridae) and chironomid (Orthocladiinae) larvae were abundant on the upper surfaces of mineral substrata of three sizes (small stones, large stones, bedrock). The density of larvae in each taxonomic group did not vary among substrata of different sizes, although strong seasonal variation existed. 3. Nemourids and chironomids (H. marcidus) collected from the upper surfaces of substrata exhibited generalist feeding habits, consuming algae (diatoms, coccoid and filamentous green algae), detritus (biofilm matrix material and fine particulate organic matter (FPOM)) and inorganic debris. 4. There was spatial variation in the gut contents of nemourids. The proportion of algae in the guts of larvae often increased with the size of the substratum from which they were collected. Strong temporal variation in the composition of the diet also existed. Nemourids ingested a large quantity of attached algae and biofilm matrix from the biofilm in spring and winter, but consumed loose FPOM and associated microflora in summer and autumn. 5. We conclude that, in this acid stream, the trophic linkage between algae and grazers is maintained by ‘detritivorous’ stonefly and chironomid species. The relationship between the feeding habits of these larvae and other life-history attributes, such as mouthpart morphology and mobility, is discussed.

Laminar Micrite Crusts and Associated Foreslope Processes, Red Sea

ABSTRACT Forereef slopes in the Red Sea of Sudan exhibit a uniform biozonation that is independent from the topography of the slopes. Below - 120 m, ledges protrude horizontally from sleep cliffs of barrier reefs and atolls as well as from patches of in situ lithified slope sediment on inclined fringing reef slopes. Free surfaces and cavities within these ledges are partly covered by laminar micrite crusts of 7-20 mm thickness. The ledges are formed by an organic framework of living azooxanthellate corals, bryozoans, serpulids and fossil red algae. They are affected by repeated episodes of boring, infilling, and cementation which obliterate much of the original fabric. Concomitant cementation and boring result in asymmetric cement linings which often show geopetal fabrics. The laminar m crite crusts, however, show no significant traces of bioerosion, which are a typical feature of fossil deep-water stromatolites. Two types of lamination have been observed: 1) vertically stacked, irregular, anastomosing laminate with ragged outlines and little lateral persistence which are often accentuated by iron staining, and 2) 0.5-mm-thick laminae of light-grey micrite, rich in fine bioclasts, showing smooth, thin coatings of dark homogenous micrite, which are weakly fluorescent in ultraviolet light. No algal films are preserved, but micritic tubes 10-30 µm in diameter, often bifurcated, form a dense network on the upper surface of the crusts by overgrowing and binding particles. Associated aragonitic rosettes 30-40 µm in diameter may represent calcified coccoid algae or bacteria. If true, these organisms suggest a formation of the latter type of crust by biogenic processes not related to the photic zone. Fenestral porosity and Frutexites textures are absent. Radiocarbon dates from corals within the ledges provide ages of 10,500 YBP. From the time-related decrease in oxygen isotope ratios (versus PDB) of boring micrite (18O = +3.72), micrite crusts (18O = +1.69), and unlithified mud (18O = +0.47) within the youngest voids of the hard substrates, we conclude that crust formation must have taken place in shallower water when sea level was lower during the Early Holocene rise of sea level.

Some size relationships in phytoflagellate motility

Data from the literature are used to assess some hypothesised adaptive advantages of the flagellate life form among phytoplankton. Possible advantages include increased nutrient uptake by movement through a homogeneous medium as opposed to exploitation of spatial hetrogeneity of the environment. Maximal migrational amplitudes and maximal swimming velocities of phytoflagellates were compared to body size. Both were found to increase with size. Relative amplitudes and relative velocities, however, were found to decrease with size. Hydrophysical considerations show that additional gain of nutrients by swimming through a homogeneous medium is only minimal for small flagellates at their attainable swimming velocities. It is suggested that exploitation of environmental heterogeneity in nutrient distribution may be one of the most important advantages for flagellates over coccoid algae.

Zellteilung und Sporulation als wichtige Unterscheidungsmerkmale bei Grünalgen (Chlorophyta)

Summary The cell division is an important character in the filamentous green algae, mainly in the unicellular forms where the cell division is the only modus of reproduction and where with they differ from the unicellular coccoid algae reproducing by sporulation. Sometimes it is difficult to distinguish between both processes if only two autospores in coccoid algae are produced. The cell division is a process where one cell divides into two equal parts (daughter cells) by mitosis and following cytokinesis. Both daughter cells using the mother cell wall grow up and divide again. In contrary the sporulation is a process where the cell mostly divides into few or many daughter protoplasts (precursors of spores), while the mother cell wall is forming the sporangium. In multicellular algae the cell division serves to the growing, development and differentiation of the multicellular organism, while the sporulation only to the reproduction. The cell division in green is sometimes algae also a modus of reproduction: As schizotomy (bipartition) in naked Phytomonadina and as cytotomy (vegetative cell division) in the unicellular algae of Stichococcus- or Closterium-type. With regard to the characters it will be relatively easy to distinguish between cell division and sporulation. Only an example where both terms were taken by mistake are pseudofilaments (Cylindrocapsa, Radiofilum) or diads and tetrads (Chlorosarcinales) with modified sporulations. A survey of all differences between cell division and sporulation is enclosed.