Lake Plankton Research Articles

Fate of Typical Lake Plankton in Streams

Fate of Typical Lake Plankton in Streams

泥炭地池沼の研究

There is a small bog lake by the fishery village of Tokotan situated 4 km from the Akkeshi Marine Biological Station on the coast of Akkeshi Bay. The lake is elongated elliptical, 150 m in .length, 47m in greatest width, and 3.5m in greatest depth. It is surrounded by Sphagnvm-moss and is connected by a short canal with Lake Tokotan which is larger than the former and not boggy. Floating lakeward margins are 2-6m in width and mainly consist of a network of stems of Menganthes trifoliata growing thick around the lake. Colour of water is deep brown. The transparency varies from 1.15 to 1.70 in meter and is changeable dependent upon the amount of zooplankton, especially Rotatoria which are the most important group in the plankton of this bog lake. Bottom deposits are generally composed of peat debris. Thermal stratification was observed during June-September in summer and during December-March in winter, and the spring overturn is frozen through the winter stagnation period. takes place in April and May and the autumn one in October and November. The surface of the lake The water of this lake is generally acid (smallest pH value, 6.05), but surface water is sometimes weakly alkaline (greatest pH value, 7.4). Dissolved oxygen is often free in a thin layer of deeper water immediately above the bottom during the summer stagnation period.From this hog lake and also from Lake Tokotan, have been known seven kinds of fishes, including Cyprinus carpio L., Carassius auratus (L.), and Hypomesus olid a (PALLAS), etc. as usefull fishes. Some of C. a'uratus are of reddish colour in natural propagation. Such naturally reddish coloured individuals inhabiting lakes are distributed on the Pacific coast of the eastern part of Hokkaido. There have been found in this lake 2 species of Mollusks, 2 of leeches, 1 of lsopoda, and several kinds of insect larvae from Merzyantlaes zone, and also found 2 species of Mollusks and one fresh water sponge from the next Equisehon-zone of 1-2 m wide.Zooplankton is considerably superior to phytoplankton in amount. The decrease of the latter seems to be mainly due to the fact that the latter becomes prey of the former. The following pelagic animals were detected in the plankton of this lake: 2 kinds of insect larvae, 1 Hydracarina, a single form of Copepoda, 3 Cladocera, 1 Nematoda, 21 species of Rotatoria, 1 Gastrotricha, 18 Ciliata, 8 Amoebina including some of Testacea, and 2 Heliozoa. Insect larvae belonging to bottom dwellers are common in deeper water, but Copepoda and Cladocera occur more frequently in surface collections of summer plankton. The Rotatoria are the most abundant among the zooplankton and richer in the surface layer than in the deeper one.The Ciliata are very rare in surface water, being abundant near the bottom where the amount of dissolved oxygen is scarce or free. The Amoebina are not found in surface collections, but found very rarely in deeper water only in summer. The Flagellata are the most excellent quantitatively in the phytoplankton of this lake, 21 species being secured, 23 forms of Chloropbyceae, 22 species of Facillarieae, and 5 kinds of Myxophyceae, have been found. Most of these usually appear very rarely in deeper water of the lake.The small boa lake at Tokotan is of the distrophic type, but is not poor in production of zooplankton as compared with eutrophic lakes in Hokkaido.

Scientific results of the Cambridge Expedition to the East African Lakes 1930-1.-No. 17. The vertical distribution and movements of the plankton in Lakes Rudolf, Naivasha, Edward, and Bunyoni.

Since little quantitative work has been done on the vertical distribution of the plankton in tropical lakes, it is considered important to put on record the data from Lakes Rudolf, Naivasha, Edward, and Bunyoni. The plankton was collected by vertical hauls with Nansen type nets of both fine and coarse mesh. The material was counted by special methods devised for the purpose, and the results were plotted in the form of histograms representing the actual numbers of individuals. Lake Rudolf is characterized by a very high temperature, alkalinity, and pH. The phytoplankton was scarce and poor in species, particularly of diatoms. The ciliate Thuriwla folliculata was the most abundant form of the small zooplankton, Lake Rudolf is characterized by a very high temperature, alkalinity, and pH. The phytoplankton was scarce and poor in species, particularly of diatoms. The ciliate Thuriwla folliculata was the most abundant form of the small zooplankton, and its association with symbiotic vorticellids is analysed. The macroplankton was very rich in Copepoda and poor in Cladocera. A 24-hour series of observations showed the diurnal migration of Diaptomus to be in the opposite direction from the usual, so that the animals were near the surface in the day and in the deeper water at night. This reversal may be due to a low sensitivity to light. The diurnal migrations of Cyclops and the Cladocera, though less marked, were in the normal direction Lake Naivmhu has a lower temperature, alkalinity, and pH, and is comparatively shallow. The phytoplankton was abundant both in numbers and species, and the diatom Melosira was dominant. The day and night distribution of the species of the phytoplankton and small zooplankton is compared, and shows an apparent migration of non-motile as well as active forms. Water currents were probably responsible for these changes in distribution. The mecroplankton contained four species at the station where the observations made, but only two were abundant. The Cladocera were nearly as numerous as the Copepoda, and their diurnal migrations were similar as shown by a 24-hour series of hauls. The numbers caught by day were much smaller than those by night, probably because the animals were concentrated at or near the bottom during the light. The nauplii and young Cyclops showed little movement. Lake Edward is the deepest of the lakes, with a thermocline between 40 and 60 metres. The temperature, alkalinity, and pH were intermediate between Lakes Rudolf and Naivasha. The phytoplankton was abundant, and consisted mainly of diatoms and blue-green Algae. Fine net hauls were taken in the deep water, and showed that there was very little life below the thermocline. The macroplankton was rich in species and individuals of both Copepoda and Cladocera. Cycclops hyalinus was the dominant form in numbers, but the greatest volume of the plankton was contributed by the larvae of Chaoborua. Lake Bunyoui is a small lake situated at a high altitude and characterized by relatively fresh water. The graphs representing the temperature and pH values at different depths show that there was no turnover of the water. The phytoplankton caught was extremely scarce, but, since the zooplankton was abundant, there must have been more plant material present, which probably escaped through the meshes of the net. The macroplankton was rich in species, and its distribution at a day and a night station waa examined. The Copepoda were more abundant than the Cladocera, and Chaoborus larvae were again present. Prawns also occurred in appreciable numbers. The main sources of error in this type of quantitative work are discussed: the most important are the lack of uniformity in the horizontal distribution, the inability to fish the bottom 2 metres, and the differences in the sizes of the day and night catches. The importance of these factors depends partly on the depth of the lake and partly on the differences in behaviour of the various species. The flora and fauna of the plankton in each lake is compared. All the lakes differ from those of temperate regions in the uniformity of the conditions and the absence of a true thermocline. The limited range of migration is perhaps due to the turbidity of the water. The East African lakes are aberrant from the Naumann Thienemann classification: they are essentiafiy eutrophic, but are modified by alkalinity. Much work on the measurement of controlling factors in the field and experimental work on the behaviour of different organisms must be performed and correlated before a complete and general explanation can be given of the distribution and movements of plankton.

The Plankton of Lake Michigan

The chief purposes of this paper are: (1) to present a general picture of the plankton of Lake Michigan (2) to determine the relative abundance of its constituent organisms, and (3) to incorporate and summarize the facts now known relating to the plankton of the Great Lakes.

A Regular Fortnightly Exploration of the Plankton of the two Icelandic Lakes, Thingvallavatn and Myvatn

During the last five years the greater part of my time has been taken up by the study of the plankton in the fresh-water lakes of Denmark, and in the spring of 1904 the first part of an extensive paper upon this subject was published by me. In that paper I have compared the results arrived at by me with the results of plankton explorations in other countries, and have tried to collect together everything known at the present moment regarding the periodicity and geographical distribution of the European freshwater plankton.

The Plankton of Fresh Water Lakes

The Plankton of Fresh Water Lakes

Rotifers in Lake Bassenthwaite

IF the occurrence of Asplanchna as a conspicuous member of the pelagic fauna of lakes has not hitherto been recorded in Britain, it can only be attributed to the lack of attention in this country to the systematic investigation of our fresh-water fauna. On the continent of Europe and in North America, Asplanchna priodonta with its variety helvetica and other members of the genus are constantly recorded as among the commonest constituents of the lake plankton. I have on several occasions found A. priodonta in lochs near Dundee in swarms similar to that described by Prof. Hickson, and I have no reason to suppose that there is anything exceptional in the phenomenon. Mr. John Hood, of this city, a veteran student of the Rotifera, tells me that its occurrence under these conditions has long been familiar to him. He states that the domestic water supply of Dundee, which always contains a variety of pelagic organisms, was on one occasion rendered quite turbid by swarms of the same species.