Studies on freshwater phytoplankton, with special reference to the Desmidiaceae

The papers submitted herewith relate to personal researches on various aspects of the biology of phytoplankton principally in Scottish freshwater lochs but also of the river plankton in the White and Blue Niles in the Sudan. The latter studies were conducted as part of a programme of work on the fundamental hydrobiology of the Nile initiated by Dr. J. Rzoska and the author, who together inaugurated the Nile Hydrobiological Research Unit. An introduction to this work is the systematic account of the algal plankton of both rivers (1) and is based on collections made between 1949 and 1952 from the Blue Nile at Khartoum and from many places between Khartoum and the Sudd region on the White Nile. Some of the effects, on the river's plankton and hydro -chemistry, of impounding water above the Gebel Aulyia Dam on the White Nile, south of Khartoum, were studied by taking a succession of samples from the Dam upstream for 325 Km (2). It was found that the plankton showed a numerical increase of more than 100 -fold, the increase being; associated with the change from river -to lake -like conditions as the Dam was approached. The seasonal development of the plankton in the White and Blue Nile has also been investigated (3). This study was based on regular samples collected over a period of three years, from 1951 -53, and indicates that although regular annual fluctuations in plankton density occur in both rivers, their peaks do not coincide but show a marked dependance on the specific hydrological regimes of the two rivers, which are briefly summarised. Related to these studies on Nile algae are some observations on the ecology of the terrestrial alga, Fritschiella tuberosa which makes a seasonal appearance on drying mud on the banks of the Blue Nile (4.). Some details of the exacting environmental conditions under which this alga grows are presented. A comprehensive survey and bibliography of the literature relating to the freshwater algae of Africa has also been compiled (5). The papers on the phytoplankton of Scottish freshwater lochs have been assigned to three categories. These relate to studies: - I. On water replacement in relation toe plankton productivity (6). Here it has been shown that water inflow and outflow in small lakes may be a factor of over -riding importance in determining the abundance of plankton. This study is related to the observations made on the White Nile plankton at the Jebel Aulyia Dam (2). II. On the effects on the phytoplankton of addin mineral fertilizers to hill lochs (7 & 8), These studies which are contributions towards investigations of the factors affecting the biological productivity of Scottish freshwaters, show that quite small additions of phosphate produce quite profound and prolonged effects on the phytoplankton of the treated lochs. Also bearing on this work are observations made on the aquatic fauna as an ecological factor in studies of the occurrence of freshwater algae (9). During the course of all these investigations the phytoplankton of many lochs were examined and observations made on this somewhat neglected aspect of Scottish vegetation. These have been published in a series of short papers (10 -14). III. On the desmid- plankton which is especially prominent in many Scottish lochs (15=22). This aspect of phytoplankton research was begun in an attempt to use plankton algae as indications of the trophic status of lakes (15 & 16). It was found, however, that the taxonomy of the most commonly occurring genus, Staurastrum, was so confused that before any real progress could be achieved a detailed reinvestigation would have to be made of many of the supposedly well established, commonly occurring species. Most prominent amongst these were S. paradoxum and S. gracile, species which, according to the literature are amongst the most widespread of plankton organisms not only in the British Isles and Europe, but throughout the world. An attempt has therefore been made to rationalize the taxonomy of these two supposedly cosmopolitan species (17 - 21). Studies have also been made on other desmids from the British freshwater plankton again with special reference to the genus Staurastrum (22 - 25). PUBLISHED PAPERS:- (01) A systematic account of the phytoplankton of the Blue and White Nile. Ann. Mag. Nat. Hist. Ser. 12, vol. 7, 195+, 648 -656. || (02) The influence of the Gebel Aulyia Dam on the development of Nile plankton. J. Animal Ecol., 23, 1954, 101 -111+. (with J. Rzoska). || (03) Seasonal plankton development in the White and Blue Nile near Khartoum. Verh. int. Ver. Limnol., 12, 1955, 327 -331+. (with J. Rzoska, and G.A. Prows. || (04) On the ecology of the terrestrial alga, Fritschiella tuberosa, in the Sudan. New Phytol., 56, 1956, 130 -132. || (05) A bibliography of African freshwater algae. Rev. Algol. 1957, 207 -238. (with Ross, Kufferath & Sims). || (06) Some observations on the effects of water inflow and outflow on the plankton of small lakes. J. Animal Ecol., 22, 1956, 22 -35. (with W.B. Woodward). || (07) Fertilization experiments on Scottish freshwater lochs. I. Loch Kinardochy. Sci. Invest. Freshwat. Fish. Scot. 17, 1957, 30 pp. (with A.V. Holden). || (08) Changes in the phytoplankton of some Scottish hill lochs resulting from their artificial enrichment. Verh. internat. Ver. Limnol. XIII, 1958, 298 -305. || (09) The aquatic fauna as an ecological factor in studies of the occurrence of freshwater algae. Rev. algol., (N.W.) 1, 1955, 11+1 -11+50 || (10) Notes on some uncommon algae from lochs in the Tu.mmel -Garry catchment area. Trans. bot. Soc. Edinb., 36 (3), 1954 -, 207 -211+. || (11) Notes on some uncommon algae from lochs in Kinross, Perthshire and Caithness. Trans. bot. Soc. Edinb., 1955, 309 -16. || (12) Notes on freshwater algae, mainly from lochs in Perthshire and Sutherland, Trans. bot. Soc. Edinb., IL 1957, 114 -122. || (13) Notes on algae from the plankton of some Scottish freshwater lochs. Trans. bot. Soc. Edinb., 37 (3), 1958, 174 -181. || (14) On some forms of Micrasterias new to or rare in Britain. Naturalist, Lond., April -June, 1957, 37 -39. || (15) The status of desmids in the phytoplankton and the determination of phytoplankton quotients. J. Ecol., 4-7, 1959, 429 -445. || (16) The phytoplankton of some Irish loughs and an assessment of their trophic status. Proc. Roy. Irish Acad., 60 B. (4), 1959, 167 -191. (with F.E. Round). || (17) Notes on desmids of the genus Staurastrum III. S. paradoxum Meyen in the Jenner Herbarium of the British Museum. Naturalist Lond., July -Sept. 1959, 81 -83. || (18) The published figures of the desmid Staurastrum paradoxum. Rev. Algol. 4-, 1959, 239 -255. || (19) Staurastrum paradoxum Meyen and S. gracile Ralfs in the British freshwater plankton, and a revision of the S. anatinum - group of radiate desmids. Trans. Roy. Soc. Edinb. LXIII No. 26, 1959, 589 -628. || (20) De Brebisson's determinations of Staurastrum paradoxum Meyen and S. gracile,Ralfs. Nova Hedwigia, 1(2), 1959, 163 -166. || (21) The varieties of Staurastrum paradoxum Meyen - nomen dubium. Nova Hedwigia, 1(4.), 1960, 431 -422. || (22) Notes on desmids of the genus Staurastrum I. S. pseudopelagicum, S. subcruciatum, S. avicula and S. denticulatum. Naturalist, Lond., July -Sept. 1957, 97-100. || (23) Notes on desmids of the genus Staurastrum. II. S. leptodermum, S. longispinum, S. brasiliense, S. setigerum, S. clevei and S. tohopekaligense var. trifurcata. Naturalist, Lond. July - Sept. 1958, 91 -95e || (24) Staurastrum pendulum var. pinguiforme Croasdale. S. micron, West, f. major f. nov., fac. quadrata and S. micron var. perpendiculatum (Cronblad) nov. comb., desmids new to the British freshwater plankton. Nova Hedwigia, 1(2), 157 -162, || (25) Desmids from the plankton of some Irish loughs. Froc. Royl. Irish Acad. B (6), 1958, 71 -91.