THE ECOLOGY OF EPIPELIC ALGAE OF FIVE WELSH LAKES,WITH SPECIAL REFERENCE TO VOLVOCALEAN GREEN FLAGELLATES (CHLOROPHYCEAE)1

The ecology of epipelic algae on the marginal sediments of five Welsh lakes was studied over an annual cycle. The lakes, Llydaw, Cwellyn, Padarn, Maelog and Coron ranged from very oligotrophic to nutrient-rich. Attention was focussed on chlamydomonad flagellates, diatoms, blue-green algae and euglenoids and the different proportions of these in algae in the epipelon of lakes of contrasting water quality. A total of 75 algal taxa was found in the five lakes, 25 were species of volvocalean flagellates. Mean annual population density of these flagellates differed by an order of magnitude between the lakes. The greatest population density was recorded for Chlamydomonas anticontata Schiller in nutrient-rich Llyn Maelog. Twenty species of pennate diatoms were recorded frequently in the epipelon. In the nutrient-rich lakes, Maelog and Coron, pennate diatoms were dominant on the sediments, where they exhibited population maxima in spring and autumn. Increase in numbers of epipelic diatoms was recorded when silica concentrations were minimum in the overlying lake waters. Navicula hungarica Grun. achieved the maximum population density, 260 000 cells · cm^?2. Euglenoids formed large epipelic populations during late-summer and autumn in these nutrient-rich lakes. Blue-green algae were more important, proportionally, in the nutrient-poor mountain lakes, which had sediments of higher organic content. Chlamydomonads were the major algal component of the epipelon in the mountain lakes, Llydaw and Cwellyn, where the sediments were characterized by larger particle size, and higher organic content. In the nutrient-rich lakes, where the sediments had higher calcium content, chlamydomonads formed significant populations only during spring and summer, when nutrient levels were minimal in the overlying lakewaters.     

A preliminary checklist of the phytoplankton of New Calabar River,Lower Niger Delta

As part of the general study of the hydrobiology of the southeastern Nigerian deltaic waters, phytoplankton samples were collected (Jan.–August, 1981, to Dec., 1984 irregularly). Sixty-seven species were identified, thirty-nine of which were diatoms. The diatoms constituted the dominant taxa especially in the brackish zone while desmids, green algae and blue-green algal species occurred more commonly in the freshwater usptream zone.     

Effect of pollution on phytoplankton in the Ashar Canal,a highly polluted canal of the Shatt al-Arab Estuary at Basrah,Iraq

The effect of pollution on the phytoplankton in the Ashar Canal was studied during March and June 1976. Higher temperatures were recorded in June. The canal water was more turbid than that of the adjoining Shatt al-Arab estuary due to high algal populations and sewage disposal. The chlorosity values were remarkably high in the canal, due to sewage disposal. The flood waters in June lowered the chlorosity in both estuary and canal. Sewage disposal into the canal decreased its dissolved oxygen content. The lower oxygen values in the estuary in June were accompanied with higher temperatures. The pH values were generally higher in the estuary and were also higher in June than in March.Eighty-six algal taxa were recorded, 45 of which were diatoms. The phytoplankton in the estuary was more abundant in March, due to the increase in currents and turbidity in June. The Chlorophyta, Conjugatophyta, Myxophyta and Bacillariophyta in the estuary showed reverse seasonal trends from those of the total phytoplankton. These algal seemed to flourish during periods of high temperatures. The dense blue-green algae recorded in June is attributed to the high temperature and dissolved organic matter. The Chrysophyta recorded high populations in the estuary in March and were totally absent in June. Lower temperatures and high transparency in March might have led to their relative abundance.The total phytoplankton in the Ashar Canal followed two different seasonal trends, one resembling and the other differing from those in the estuary. The disposal of domestic sewage and agricultural wastes in the canal seemed to lead to such adverse seasonal variations. The diatoms only dominated the phytoplankton at one station in both months. The sewage and agricultural wastes disposal seemed to favour the abundance of the other phyla than the diatoms. Increased organic load in the canal has led to a considerable increase in the Myxophyta in June. Blooms of Chlamydomonas sp. and Euglena acus increased the phytoplankton densities in March at stations II and IV, respectively. Benthic or periphytic algae were found in the phytoplankton populations. Raised salinity seemed to restrict the distribution of the planktonic diatom Bacillaria paradoxa. Among the noticeable widespread planktonic algae in the study area are Dinobryon sertularia, Pediastrum duplex and P. simplex.     

An annotated check-list of microalgae from Øvre Heimdalsvatn and its tributaries

About one hundred genera with more than 300 species have been identified in water samples, net haul material, periphyton samples from artificial substrate, and benthos and sediment samples collected during 1969–1972. More than 40 taxa of lower rank (subspecies, varieties, forms) were recorded. The most prominent algal groups were diatoms with 138 taxa, and green algae with 122 taxa of which the majority was desmids. The material from the epipelic and epilithic communities in the lake is very scarce, while the list of plankton species is relatively complete, with the exception that a large number of small flagellates could not be identified to species level. The taxa which were identified, are presented in a list with additional notes on occurrence.     

宁夏沙坡头地区藻类及其分布

通过野外采样,室内培养、观察、鉴定,研究了沙坡头地区藻类多样性和分布特点,并为当地藻类资源利用提出建议。研究发现沙坡头地区藻类植物共计40种(包括1变型),其中蓝藻17种,绿藻10种,硅藻9种,裸藻4种,全为普生种,陆地生境中种类最丰富。亚气及陆地生境中蓝藻在种类数(除灌溉林地结皮)、生物量方面占主导地位;贫瘠水体生境中硅藻占主要地位,营养较丰富水体中绿藻处于优势地位。另外,陆生生境中多以具鞘微鞘藻Microcoleus vaginatus为优势种,小席藻Phormidium tenue为主要种。     

Long-term response of the biotic community to fluctuating water levels and changes in water quality in Cootes Paradise Marsh,a degraded coastal wetland of Lake Ontario

During the early 1900s, more than 90% of the surface area of Cootes Paradise Marsh was covered with emergent vegetation; currently, less than 15% of the surface is covered with aquatic vegetation and the remainder is wind-swept, turbid, open water. The loss of emergent cover is significantly correlated with mean annual water levels that increased more than 1.5 m over the past 60 years. Species diversity and the percent cover of the submerged macrophtye community also declined dramatically after the 1940s, coincident with decreased water clarity and increased nutrients from pollution by sewage and stormwater effluent. Phosphorus levels in the marsh dropped ten-fold after the sewage plant was upgraded to a tertiary-treatment facility in 1978; however, there was no measurable improvement in water clarity, in spite of a decrease in chlorophyll concentrations. Long-term changes in the composition of the planktonic, benthic and fish communities accompanied changes in water clarity, nutrient status and macrophyte cover. Phytoplankton changed from a community dominated by diverse taxa of green algae and diatoms during the 1940s, to a less diverse community dominated by a few taxa of green and blue-green algae in the 1970s, then to a much more diverse community recently, including many taxa of green algae, diatoms and chrysophytes; however, because water turbidity continues to be high, and algae tolerant of low light levels are now very abundant. Daphnia, which were prominent during the 1940s (especially in the vegetated sites) were replaced in the 1970s by smaller zooplankton such as the cladoceran, Bosmina, and several rotifer species including Brachionus, Asplanchna and Keratella. In the recent survey conducted in 1993 and 1994, small-bodied forms still dominate the turbid open-water areas, while medium-sized cladocerans such as Moina were common near macrophyte beds. Generally, total herbivorous zooplankton biomass tended to be highest next to Typha beds and declined with increasing distance from the plants. Conversely, biomass of edible algae at these sites increased with distance from the macrophytes. Species diversity of aquatic insects declined dramatically over the past 40 years, from 57 genera (23 families and 6 orders) in 1948, to 9 genera (6 families and 3 orders) in 1978, to only 5 genera (3 families and 2 orders) in 1995. The diverse benthic community present 5 decades ago has now been replaced by a community consisting primarily of chironomid larvae, oligochaetes and other worms associated with low-oxygen environments. These successional changes illustrate the impact of natural (fluctuating water levels) and anthropogenic (deterioration in water quality) stressors on the character of the biotic communities, and reveal the complex interactions among the various trophic levels and the abiotic environment as degradation and remediation proceeded.     

SEM observations of some noteworthy diatoms from the Ikpoba reservoir,Nigeria

ABSTRACT

Eighteen taxa of diatoms from the Ikpoba reservoir, southern Nigeria are listed in this report. They belong to the genera Cymbella, Stenopterobia, Eunotia, Brachysira, Frustulia, Navicula, Pinnularia, Stauroneis and Surirella. The occurrences and distribution of the algae are indicated. Two of these taxa occurred very frequently, six frequently and four occasionally. Five taxa had rare occurrences while one was very rare. They were compared with national as well as regional records.     

The insight into diatom diversity,ecology, and biogeography of an extreme cold ultraoligotrophic Lake Labynkyr at the Pole of Cold in the northern hemisphere

The freshwater ultraoligotrophic Lake Labynkyr is located near the Pole of Cold in the northern hemisphere (Yakutia, Russia). The lake is covered by ice during 240 days a year. We undertook several expeditions to the lake during the ice and open water periods for sampling ice fouling, plankton and periphyton that were then analyzed by means of scanning electron microscopy. As a result, we identified a high biodiversity of diatoms—123 species and intraspecific taxa from 53 genera, among them 3 species were new for Russia and 26 taxa were new for the algal flora of Yakutia. The oligo- and xenosaprobionts and their variations dominate—71 taxa. 18 Species were evaluated as tolerant to cold oligotrophic waters, 12 occurred on the ice bottom, and 62 in the water column under ice (0–25 m). 104 taxa were found during the open water period, 70 taxa were identified in the periphyton. We showed the diatom flora of Lake Labynkyr to be unique compared with other lakes of Yakutia and to share taxa with the diatom flora of Lake Baikal. The diatoms being indicators of the global climate changes and ecological status of lakes, our data can be used as an evidence of such changes as well as to be useful studies of biogeography and history of formation of flora in Arctic and Subarctic waters.

     

上海市滩涂夏季底栖硅藻初步研究

报道了上海市夏季滩涂底栖硅藻的种类组成和生态分布的情况。样品于2005年8月从7个站点中采集,经处理、镜检观察,从中鉴定出硅藻98个分类单位,包括种、变种和变型,分别隶属于2纲7目10科31属。舟形藻属(Navicula)最多,共发现15个分类单位;其次为菱形藻属(Nitzschia),有10个分类单位。其中Cyclotella meneghiniana,Gyrosigma spencerii,Surirella ovata为优势种,Fragilaria capucina,Gyrosigma attenuatum,Naicula acceptata等为常见种,Melosira italica,Coscinodiscus wittianus,Navicula pygmaea等只在个别站点采到。数量分析表明,硅藻总细胞丰度变化为7.0×106-28.5×106 cells m-2,平均为17.39×106cellsm-2,在径流入海口处硅藻数量相对较多,其中淡水种比海生种多,这主要是因为长江口近岸河口水域是多种水系相混合的水体,淡水入海带来较多的淡水种类。     

Species richness in macroalgae and macrofauna assemblages on Fucus serratus L. (Phaeophyceae) and Zostera marina L. (Angiospermae) in Skagerrak, Norway

The macrophytes Fucus serratus and Zostera marina form similar substrates for associated flora and fauna in shallow waters in Norway. While F. serratus forms a more or less continuous belt on rocky substrate along the coast, Z. marina forms disjunct populations on sandy or muddy bottoms. This study focused on the organisms associated with these two macrophytes in two localities in the Skagerrak region. In total, 130 taxa of epiphytic organisms were identified: 22 green algae, 41 red algae, 32 brown algae, eight diatoms and 27 sessile animals. One hundred and twenty-seven taxa of mobile macrofauna were registered. The dominant group was crustaceans, with amphipods as the order containing most species. Many species of both plants and animals preferred one or the other habitat. It is concluded that coastal macrophyte systems have high species diversity.     

The distribution and abundance of algae in saline lakes of Saskatchewan,Canada

Collections of algae, mainly planktonic, were made from 41 saline lakes in southern Saskatchewan ranging in salinity from 3.2 to 428 g l^-1. Algae in 7 phyla, 8 classes, 42 families, 91 genera and 212 species and varieties were identified. Fourteen species were restricted to hypersaline (50 g l^-1) waters and eleven of these were diatoms. In general, species diversity was inversely related to lake salinity. Algae that were important community constituents over a broad spectrum of salinities were the green algae Ctenocladus circinnatus, Dunaliella salina and Rhizoclonium hieroglyphicum, the blue-green Lyngbya Birgei, Microcystis aeruginosa, Oscillatoria tenuis, O. Utermoehli and Nodularia spumigena and the diatoms Melosira granulata, Stephanodiscus niagarae and Chaetoceros Elmorei. In general green algae were dominant when lake salinity exceeded 100 g l^-1 although diatoms played important roles in most of these highly saline lakes except for Patience Lake.     

Algae in urban drinking waters in N.E. Spain

Tap waters from Barcelona and several other locations in N.E. Spain were analyzed to determine the algal occurrence and to assess their probable origin and fate. In general, a low number of taxa (2–9) occurred per sample, while cell density was highly variable (from 20 to more than 1000 cells ml^-1). Green algae were usually the most abundant, most of the taxa being common in natural phytoplankton assemblages from mesotrophic or eutrophic waters. The proportion of planktonic to benthic taxa differed between samples, there being only one sample (Lérida) with a predominant planktonic composition. Analysis of treated water revealed that algae were not completely removed at the end of the treatment, meaning that a low number could reach the distribution network. Moreover, other organisms (flagellates) had their origin in storage water tanks. No seasonal pattern of occurrence was apparent since there were many occasional taxa, implying a lack of direct connection between natural populations and tap water algae. It is therefore suggested that algae can reach the distribution network by several possible origins. Algae were sometimes viable; culture experiments showed occasional growth in June, but not in August samples.     

Limnological investigations on the Rosetta branch of the Nile. III. Phytoplankton

SUMMARY.

• 1 Seasonal qualitative and quantitative studies of the phytoplankton of the Rosetta branch of the River Nile are reported. Most of the genera were Bacillariophyceae, with Chlorophyceae and Cyanophyceae second and third. Only two genera of Dinophyceae were present. The phytoplankton can be broadly described as eurythermal and euryhaline.
• 2 Phytoplankton tended to be more concentrated in surface waters and showed large variations from station to station, with noticeably lower values in the estuarine region except in January.
• 3 Most of the genera were recorded at all times but seasonally the highest numbers of diatoms and green algae were found in July during a period of high temperature and low discharge whereas blue-greens achieved maximum density in October.

     

COMMUNITY STRUCTURE DYNAMICS OF EPILITHIC AND EPIPHYTIC DIATOMS IN A MISSISSIPPI STREAM1

Epilithic and epiphytic diatoms were collected monthly from 18 June 1979 through 19 May 1980 from both shaded and unshaded sites of Sessums Creek, a shallow, oligotrophic and strongly alkaline stream in northeastern Mississippi. The dominant macroalgae were filamentous green algae belonging to the non-mucilage producing genera Cladophora and Rhizoclonium. Ninety taxa were identified with Navicula minima Grun. and Nitzschia dissipata (Kütz.) Grun. accounting for 50% of all valves counted. Other important taxa were Navicula menisculus var. upsaliensis (Grun.) Grun., N. cryptocephala var. veneta (Kütz.) Rabh., Achnanthes minutissima Kütz. and Cymbella turgida (Greg.) Cl. With few exceptions, the more dominant taxa were equally abundant in the shaded and unshaded sites and also in the epilithon and epiphyton. Species diversity (H') and the number of taxa in a sample in all four habitats showed an identical pattern, being lowest in winter and highest in fall. No one pair of habitats was more structurally similar than any-other pair when compared by a similarity index (SIMI). Apparently, differences in light intensity and substrate type had little effect on diatom distribution in Sessums Creek and it was concluded that the locality sampled supported a single, nearly homogeneous diatom community.     

A checklist of algal species found in the East Siberian Sea in May 1987

Summary A checklist of microalgae found in sea-ice in the East Siberian Sea in May 1987 has been compiled. A total of 122 taxa have been identified, consisting of 101 taxa in 18 genera of pennate diatoms, 14 taxa in 8 genera of centric diatoms, 4 taxa in 3 genera of dinoflagellates (including Ebria sp.), and 2 taxa in 1 genus of chrysophytes (silicoflagellates); choanoflagellates (Craspedomonadales) were found in one sample.     

Ecological description of the sodium chloride mineral springs in the Kirenga River basin and the upper reaches of the Lena River: 2. Flora of non-vascular plants: Algae,lichens

For the first time, the flora of algae and aquatic lichens is studied in the sodium chloride mineral springs of the Northern Baikal region flowing from the Lower Cambrian salt-bearing formations. The full list of algae found in six springs is presented. In total, 257 taxa are identified belonging to six divisions: Cyanoprokaryota (=Cyanophyta), Euglenophyta, Bacillariophyta, Xanthophyta, Chlorophyta, and Streptophyta. The flora of diatoms is the richest (196 taxa, or 76%). The similarity of algoflora of different springs is negligible. Species that are indifferent to salinity prevail in most of the mineral springs; mesohaline species dominate in the Ust’-Kutskii spring. Nineteen taxa of halophile diatoms are identified. The marine species Percursaria percursa (Chlorophyta) is recorded in Klyuchevskoi and Ust’-Kutskii springs. In the three springs, seven lichen species from the four genera are identified, five species are truly aquatic and two species may stand flooding; all these species are found in the freshwater ponds and streams. Two species of the genus Bagliettoa are probably relict in the Baikal region.     

Benthic feeding by krill, Euphausia superba Dana, in coastal waters off West Antarctica and in Admiralty Bay, South Shetland Islands

Diatoms in the food of krill caught in the summer in coastal waters close to the South Shetland Islands and in the summer and three winters in Admiralty Bay, King George Island were investigated. The diatoms were used as indicators of sources of krill food. Principal component analysis divided the diatom taxa into two groups, one being pelagic diatoms and from the food of krill in coastal waters, and the other being benthic diatoms and taxa from the food of krill in Admiralty Bay. All pelagic taxa of diatoms were consumed by krill. In the summer in coastal waters, benthic diatoms in krill food originated from the sublittoral. In the summer in Admiralty Bay, besides phytoplankton, diatoms were noted from the sublittoral and littoral in the food of krill. However, in the winter mostly sublittoral and epiphytic diatoms were present in krill food. Accepted: 20 March 2000     

江汉平原47号钻孔中的化石硅藻及其在古环境分析上的意义

江汉平原47号钻孔,位于湖北省江汉平原的江陵县,在其上段的46.6-2.2m层位上,有丰富的化石硅藻,约有26属148种,其中绝大多数是现存的淡水种类,并以附生性、沿岸带和浅水性的种类为主。种类较多的属有:Navicula(28种)、Cymbella(23种)、Achnanthes(15种)、Gomphonema(14种)和Eunotia(13种)。主要种类有Gomphonema tropicale var. nonpunctatum、Cyclotella comta、Cocconeis placemula vat. lineata和Stephanodiscus dubius等。硅藻中的种数(种/层)和数量(个/每克干沉积物)经历了一个从无到有、由少到多再逐渐减少直至消失的过程。这反映了水体环境也相应地经历了一个漫长的变迁过程:河流(可能是长江古道)→边滩和河漫滩→泛滥平原的积水洼地(湖泊或沼泽)→水体变深加宽→水体消失。从不同沉积相中各种类型(适酸碱度不同)的硅藻比例(即硅藻种谱),可以推测当时水体的酸碱度的变化不大,在中性或中性偏碱的范围。由化石硅藻并结合孢粉的矿物分析,可以推测当时硅藻大量生长繁殖时期的水温较凉,气候可能偏冷。硅藻的数量与沉积物的平均粒度呈明显的相关性,硅藻的种数与沉积物的平均粒度也呈明显的相关性。