Patterns of seasonal succession of freshwater epipelic algae

Download Patterns of seasonal succession of freshwater epipelic algae

Post on 27-Mar-2017




0 download

Embed Size (px)


<ul><li><p>This article was downloaded by: [Southern Taiwan University of Science andTechnology]On: 20 November 2014, At: 23:22Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK</p><p>British Phycological JournalPublication details, including instructions for authors andsubscription information:</p><p>Patterns of seasonal succession offreshwater epipelic algaeF.E. Round aa Department of Botany , University of BristolPublished online: 17 Feb 2007.</p><p>To cite this article: F.E. Round (1972) Patterns of seasonal succession of freshwater epipelicalgae, British Phycological Journal, 7:2, 213-220, DOI: 10.1080/00071617200650221</p><p>To link to this article:</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all the information(the Content) contained in the publications on our platform. However, Taylor&amp; Francis, our agents, and our licensors make no representations or warrantieswhatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions andviews of the authors, and are not the views of or endorsed by Taylor &amp; Francis. Theaccuracy of the Content should not be relied upon and should be independentlyverified with primary sources of information. Taylor and Francis shall not be liablefor any losses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly or indirectly inconnection with, in relation to or arising out of the use of the Content.</p><p>This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden.Terms &amp; Conditions of access and use can be found at</p><p></p></li><li><p>Br. phycol. J. 7:213-220 15 July 1972 </p><p>PATTERNS OF SEASONAL SUCCESSION OF F R E S H W A T E R EPIPELIC A L G A E </p><p>By F. E. ROUND </p><p>Department of Botany, University of Bristol </p><p>The seasonal succession of algal species in the epipelon of two small pools over a period of three years is described in relation to changes in silica, nitrate-nitrogen and phosphate- phosphorus concentrations in the water above the sediments. Recurring patterns of seasonal growth of the various species are discussed. </p><p>Much has been wri t ten over the years concerning the seasonal succession o f bo th mar ine and freshwater p l ank ton ic algae but, wi th the no tab le except ion o f a few intensely s tudied species, the control l ing factors cont inue to be elusive. In a recent paper , R o u n d (1971), some prob lems were discussed with reference to the succession o f species o f f reshwater p lank ton and it was po in ted ou t tha t the ac tual seasonal succession o f the non-p lank ton ic algal popu la t ions had ye t to be documented in any detail . Cer ta in pat terns o f seasonal d i s t r ibu t ion and the concept o f ' shock ' events in br inging abou t the sudden col lapse o f popu l a - t ions was pos tu la ted to expla in the often s imul taneous col lapse o f popu la t ions in geographical ly isola ted lakes. These ' shock ' per iods cor responded to per iods o f r ap id change in the aqua t ic hab i t a t usually associa ted with cri t ical levels being reached in the physical environment . These opera te largely t h rough strat if icat ion and de-s t ra t i f icat ion in bodies o f water deep enough to fo rm a thermocline. D a t a for a s imilar s tudy o f epipelic communi t ies are scarce and two years ' cont inuous observat ions are a min imum requirement . The fol lowing da t a were ob ta ined over three years and f rom ext remely shal low and small ponds where no th ing more than d iurna l thermal s trat i f icat ion is l ikely to occur, thus e l iminat ing no rma l s t rat i f icat ion as a direct factor . However , s tudy o f such a s i tuat ion has cons iderable bear ing on s imilar communi t i es in larger bodies o f water capab le o f the rmal s trat i f icat ion since the epipel ic popu la t ions in large water bodies tend to occur only above the thermocl ine wi th the result tha t the effects o f s t rat i f icat ion on this associa t ion are no t necessari ly so d ramat ic . The seasonal sequence o f species is, however, jus t as p ronounc e d as it is in the p lankton . </p><p>M E T H O D S </p><p>A small amount of surface sediment was drawn off by means of a pipette and rubber bulb from the ponds approximately once every two weeks. The sediments were allowed to settle and then poured into Petri dishes and the excess water removed. Cover glasses were placed on the surface and left for 24 h. These were then removed and the algae adhering to the undersurface identified and counted along standard transects (20 mm), after which the whole coverglass was scanned for rare species. Silicate, nitrate and phosphate content of the water drawn off from directly above the sediment of the ponds was estimated by the methods in Mackereth (1963). Pool 1 was extremely shallow, a few centimetres of water at most covering the sediment. Pool 2 was approximately 50 cm deep. The outflow of Pool 1 ran into Pool 2. The two pools are situated in the Botanical Garden of the University of Birmingham and are </p><p>213 </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Sout</p><p>hern</p><p> Tai</p><p>wan</p><p> Uni</p><p>vers</p><p>ity o</p><p>f Sc</p><p>ienc</p><p>e an</p><p>d T</p><p>echn</p><p>olog</p><p>y] a</p><p>t 23:</p><p>22 2</p><p>0 N</p><p>ovem</p><p>ber </p><p>2014</p></li><li><p>214 F.E. ROUND </p><p>so close as to be under virtually identical conditions of shade, etc. Water percolated into Pool 1 from a surrounding rockery and then overflowed down a short channel into Pool 2. Pool 1 was approximately 1 m and Pool 2 was several metres wide. </p><p>RESULTS </p><p>Figs 1 and 2 show the seasonal distribution of the major diatoms and other algae on the sediments of the two pools plotted on a similar basis together with data for silicate, phosphate and nitrate contents of the water. The vertical lines are drawn quite arbitrarily mid-way through the year and at the end of the year. These points are, however, important in that they correspond very approximately to the point of longest and shortest day length, i.e. of greatest and least solar radiation and of high and low water temperature. </p><p>A characteristic of these seasonal cycles is their general reproducibility from year to year. Obviously there is some variation but this is only to be expected since the 'correct' set of conditions for each species is dependent on the vagaries of the climate in each year. However, without this reproducibility the problem would be even more baffling than it is. For convenience of discussion the species with clear-cut distributions are dealt with first. These can be separated into groups growing at approximately the same time in each year. </p><p>Stauroneis anceps Ehrenb., Nitzschia dissipata (Kiitz.) Grun. and Oscillatoria sp. grew in the early part of the year (January/February-May/June) as tem- perature and light intensity were increasing and then declined while these factors were still increasing; one must not, however, presuppose that these are neces- sarily the limiting factors. Navicula pupupla var. capitata Hust. had a slightly more extended growth period but was confined to the first six months of the year in Pool 2 while in Pool 1 it continued growth until slightly later (August) in Years 1 and 3. For some reason its whole growth period was shifted to a later period (May-November) in Year 2. </p><p>Nitzschia acicularis W. Sm. is a mid-summer (i.e. high light/high temperature) species in both ponds. In Year 1 and Year 3 it was prominent in June/October but, interestingly, in Year 2 it commenced growth early (January/February) in both pools and ceased growth early (June/July). Cymatopleura elliptica (Brrb.) W. Sm. is another mid-season species and was again maintained in the popula- tion until November in Year 2 (cf. Navicula pupula var. capitata). In Pool 1 this species occurred only in Year 3, somewhat earlier in the year. This is such an obvious species that it could not have been overlooked in previous years. Another June-October species is Navicula pupula Kiitz. in Pool 2, though in Year 2 it occurred much later (September-December). Interestingly, this species followed its variety capitata in the seasonal sequence in both pools but in Pool 1 it grew much later (see below). </p><p>Caloneis amphisbaena (Bory) CI., Navicula cuspidata Kiitz., N. radiosa Kiitz., N. pupula (in Pool 1), and N. oblonga Kiitz. (in Pool 2), fall into the category of species growing in cold water under low light conditions. However, in Pool 1, N. oblonga was more widespread throughout the year, though it was still pos- sible to discern a pattern of seasonal distribution with a fairly extended period of occurrence in the first six months of each year followed by a second small burst of growth in August/September. </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Sout</p><p>hern</p><p> Tai</p><p>wan</p><p> Uni</p><p>vers</p><p>ity o</p><p>f Sc</p><p>ienc</p><p>e an</p><p>d T</p><p>echn</p><p>olog</p><p>y] a</p><p>t 23:</p><p>22 2</p><p>0 N</p><p>ovem</p><p>ber </p><p>2014</p></li><li><p>S e a s o n a l success ion o f epipel ic a l g a e 215 </p><p>0.~ I </p><p>- I l i l i i ~ l l - q l ~ J l i l . . , . . I r ?lNl-,,~41.. </p><p>\ / </p><p>I I ,x I eL _ _ l _ _ N </p><p>,.et,.~., "~e" k i ' ~ . ~ l / 'i-ll--_-o .i~" F~e..," " e C ' ~ " e i - . - " ' o - o - . , ~ </p><p>1 I P </p><p>.o , '" / % , ' " , ........ .---" </p><p>i i I i t o-o I I </p><p>l 1 I i I . </p><p>I " '&lt; : s, I "it Z \ i i I </p><p>I ' , , ' " . , \ # , I o.e ? , i ~ ' - o I </p><p>~ - o O I I I - . " N i - . I S t o n I </p><p>a t \ : ,' x , / x I I ' . : t " * , - - ' , </p><p>2 ~ if X I - - ? - ' v " x ~ - .-0 , No cr I , e . 1,,~... ~ - - i o , l ~ , </p><p>4 ~ / I </p><p>i o-'N'qN,, ~ NO pu ~'~, e.._l % p~ n ~ ~_ 1 _..e" e'l\ o--o.O. </p><p>. / t ' t . / ? " , _ ,,,,";- ,,: .oou co, ' " " " " ] "o,' ! ~ rO . " . , ~ ~ " . 0 . 0 I , . I ' , \ I V = , \ </p><p>. . . . o d " - - I , : -- .~. / , t / % I N o hu CO I </p><p>.*--.- "" x I ~ ...-. " ' " % l , ; , , e io" v ~. ? k / : * ' . ; , , P V V \ / , " \ - - </p><p>" " ' I S / " \ d " 1 | t </p><p>? /O.o. ~ i ) r NO ob "O ~ I O L </p><p>r"~ o, / \ , . . . ' ' ,P 'o ' F"~- I w ' - - ' </p><p>3 ~ 2 </p><p> I 3 - " ~ - ~ - . * 2;,.' \ -" \ ',Z "",. I X I/ \ . ~ </p><p>I </p><p>zF# \ .+ ." . - '~ . ,i W ~ / . , v\ | ~ i - - M/o".a </p><p>I I i </p><p>4 </p><p>5 2 I </p><p>2 I </p><p>I +4,+-+-I- + - I -+++ ICh + + + I ++.1-.t- + + "t'++ Sy , i </p><p>F: , ' , ; vV" \ T',</p></li><li><p>216 F . E . R O U N D </p><p>i ' i N % 1 . 0 - I /i~ . .o , , / o I i . o,O I </p><p>Z- Z~i! tl.o/t ', P O' "0--- </p><p>' l ~ , . , " .o, ~,-- , . , . . , - , , . . . . . +,.--,.,.,</p></li><li><p>Seasonal succession of epipelic algae 217 </p><p>Three species, Navicula cryptocephala Kiitz., Navicula hungariea var. capitata (Ehrenb.) C1. and Nitzschia palea (Kiitz.) W. Sin., have more extended growing periods. However, two of these, N. cryptocephala and N. palea, are notoriously difficult to identify since many closely related forms can be grouped together and in counting live material less confidence can be placed on the results for these two species. Indeed, there is evidence of two or three growth periods on the graphs of the two species, suggesting the existence of morphologically similar forms varying in their ecological requirements. If this is so one must discount the possibility that some species can grow through the 'shock' periods to which most of these microscopic algae are susceptible. Navicula hungariea vat. capitata is, however, one of the easily recognisable species and is unlikely to be confused with another diatom. In Pool 2 its presence extended roughly from January to October, while in Pool 1 it was present throughout the year but in extremely low numbers in October-November (December) in two of the three years. In Year 2 no reduction in cell numbers occurred in the autumn period which is notably a time of low algal growth in this habitat (a very similar pattern was shown by Nitzsehia palea in Pool 1). </p><p>The few remaining algae are difficult to fit into any pattern, possibly because the plots are of groups of species, e.g. cryptomonads and euglenoids. How- ever, the latter, at least, seem to show little growth in June]July/August; this is rather surprising since they are usually associated with high organic matter content which usually coincides with periods of high temperature and hence high rate of decay. In Pool 1 these flagellates occurred only in the first year, a feature which may be related to the chemical conditions which obviously underwent a change after this. </p><p>The chemical data show some considerable differences from year to year, due, I believe, to cultivation and fertilisation of the adjacent soils through which the water percolated into these pools. Pool 1 was fed entirely by water dripping out of the soil and in Year 1 had high silicate and phosphate concentrations but very low nitrate. Nitrate then increased somewhat in Years 2 and 3. Pool 2 receives water draining from Pool 1 and from the surrounding soil but, being larger, is more buffered; even so, there was again a tendency for high silicate and phosphate values in Year 1, though nitrate was fairly constant through the three years. </p><p>DISCUSSION </p><p>A study of the data raises many problems though only a few possible explana- tions can be suggested. </p><p>The sequence (Fig. 3 (a)) envisaged by Round (1971) with four growth periods (A - D) during the year was shown to occur fairly frequently in the plankton though the four growth periods tended to fuse as eutrophication in- creased. A hypothesis was suggested based on the assumption that species may persist in the plankton for some period after active growth has ceased and thus seasonal patterns might extend more (as in Fig. 3 (b)). Such a situation probably applies to some species of the epipelic flora and it is possible to select species from these two pools to fit such a graph (Fig. 3 (c)) in which A is represented by a species such as Stauroneis anceps, B by Nitzschia aeicularis, C by Navieula pupula in Pool 2 and D by Navicula cuspidata. As with the plankton the growth </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Sout</p><p>hern</p><p> Tai</p><p>wan</p><p> Uni</p><p>vers</p><p>ity o</p><p>f Sc</p><p>ienc</p><p>e an</p><p>d T</p><p>echn</p><p>olog</p><p>y] a</p><p>t 23:</p><p>22 2</p><p>0 N</p><p>ovem</p><p>ber </p><p>2014</p></li><li><p>218 F. E. R O U N D </p><p>(b) </p><p>(e) </p><p>O F M A M O O A S O N D </p><p>FIG. 3. (a) Hypothetical growth curves for freshwater populations, assuming fairly rapid death of population following termination of growth (see text for further detail). (b) Hypothetical growth curves with live ceUs r...</p></li></ul>