Bailey-Watts, A.E.

Kirika, A.A.

English

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   Chapter (non‐refereed)   Bailey­Watts, A.E.; Kirika, A.A.. 1984 Eutropication of Loch Leven. In: Annual Report of the Institute of Terrestrial Ecology 1983. NERC/ITE, 19­21.   Copyright © 1984 NERC  This version available at http://nora.nerc.ac.uk/10313/    NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the authors and/or other rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access    If you wish to cite this item please use the reference above or cite the NORA entry                        Contact CEH NORA team at  nora@ceh.ac.uk Eutrophication of Loch LevenFresh waters commonly become increasingly en-riched with mineral nutrients, and lakes and riversare each subject to this eutrophication process(Vollenweider 1968). The substances of most con-cern in this context are nitrogen and phosphorus, asboth are essential for plant growth, and it is commonlythe growth response by plants to the enrichment thatcauses problems. Thus, in standing waters in parti-cular, the enrichment is shown by dense algalpopulations which may (directly or indirectly) affectman's use of the water for potable and industrialsupply, as well as fishing and other leisure activities.Depending on the particular species of alga present,the growths may form the surface 'blooms' charac-teristic of many lakes on calm and especially warmdays.Records of algae collected from Loch Leven in south-east Scotland at the turn of the century (Bachmann1906, 1907) suggest that this large shallow lake(4 m mean depth, 13 km' surface area) has beeneutrophic for a long time. Moreover, dense bloomsof blue-green algae in the loch were noted in 1937,when they were associated with poor trout anglingreturns (Rosenberg 1938), and on occasions duringthe 1950s and 1960s (Brook 1957, 1958, 1965).Fluctuations in the Loch Leven phytoplankton —monitored especially closely since 1968 (Bailey-Watts 1974, 1978, 1982) —show that the loch hasremained eutrophic. However, it is only since the late1960s that detailed chemical analyses have beenmade of Loch Leven water. Our understanding ofthe relationships between phytoplankton perform-ance and nutrient concentrations in this loch hasthus been developed from the analysis of the last 15years' records.Since 1968, it has been established that the majorsource of nitrogen to the loch is surrounding agri-cultural land (Holden Er Caines 1974: Holden 1976).To increase the yields of improved grass for cattleand of grain crops, much of the catchment of the loch(70% of a total area of 145 km2—Smith 1974) hasbeen heavily fertilized since the late 1950s. Runofffrom the agricultural land has resulted in increasesin nitrate concentrations in the inflowing streams.These increases have led to a rise of approximately1 mg N over the period 1 970-1 980 in therecorded winter (January—March) maximum concen-trations in the loch itself (Figure 9).Contrasting with nitrogen supplies, which enter theloch in a diffuse manner, most of the phosphorusreaches the loch at well-defined points (Plate 7).During the late 1960s, and up until 1972, some 65—70% of the total loading (>1-25 g P m-2 yr-1) wasassociated with a single point source, ie an outfallof woollen mill effluent (Holden 1976). By 1976,a considerable reduction in total phosphorus loading321968 1969 19701971  1980 1981 1982 1983Figure 9 Contrasts in the winter maximum nitrateconcentrations in Loch Leven between the periods1968-71 and 1980-83 (1968-71 data from Holden& Caines 1974). Shaded columns refer to a samplingstation near the outflow and unshaded columns toan open water sitewas effected by a change in the policy of the woolmanufacturers for the disposal of their effluent. Thus,by 1976, the estimated total loading had beenreduced to 0-7 g P m-2 yr1 (values calculated fromHolden Et Caines 1974).4020Freshwater and marine ecology 191979 1980 1981 1982 1983Figure 10 Mean phytoplankton biomass levels (ex-pressed as concentrations of chlorophyll  a)  in LochLeven 1979-8320 Freshwater and marine ecologyTable 3. Algae dominating the phytoplankton. of Loch Leven at the times of various biomass maxima, 1979-82SeasonJanuary—AprilMay—August1979 1980 1981 1982Unicellular centric Unicellular centricdiatoms diatomsCryptomonads and ChrysoflagellateschrysoflagellatesSeptember—December Filamentous blue- Filamentous blue-green algae green algaeThe eutrophication of Loch Leven over recent timescan, therefore, be summarized as an overall increasein nitrogen loading and a general decrease in phos-phorus loading. A desk study (Bailey-Watts 1983)suggests that the current total loading of phosphorushas changed little since 1976, and, at 0.8 g m-2 yr-1,reflects an increase attributable mainly to the contri-bution in treated sewage as a result of populationincreases in the catchment area (see also Cuttle1982).Mean algal biomass had approximately halved overthe period 1968-1976, during which time the loadingchanges referred to aboVe took place, and annualmean chlorophyll concentrations of 36, 32 and41 mg m-3 were obtained for the years 1977, 1978and 1979 respectively (Bailey-Watts 1982). AsFigure 10 shows, the pigment levels have remainedfairly low since 1979. However, changes inalgal species composition have continued through-out the period under review (Bailey-Watts 1974,1978, 1982, unpublished data); Table 3 illustratesthe range of dominant species recorded at the timesof major crop maxima during 1979-1983—the periodof relative stability in terms of mean annual biomass.Although current algal biomass levels are low com-pared to those recorded a decade ago, the generalproblems commonly associated with algal develop-ments induced by eutrophication persist. At LochLeven, these include (i) unsightly scums and odourassociated with the collapse of occasional denseblooms of blue-green algae, (ii) poor water clarity,(iii) problems in treating water for downstream in-dustrial purposes (paper making), (iv) limited cover-age by submerged rooted vegetation, and (v) poorfishing. The recent desk study to assess the feasibilityof further control of phosphorus inputs to the lochsuggested that removal of phosphorus from sewageand trade effluent should be seriously consideredphosphorus in these effluents currently appears too 0YearUnicellular centric Unicellular centricdiatoms diatomsPennate diatoms, Colonial blue-greenchrysoflagellates, algae and cryptomonadsunicellular andcolonial green algaeUnicellular green algae. Unicellular and colonialchrysoflagellates and green algae and colonialunicellular centric blue-green algaediatoms40 80 120 180Chlorophyll a  (mg m-3)Figure 11 Line illustrating relationship betweenwater transparency (expressed as Secchi discreading) and phytoplankton biomass (expressed aschlorophyll  a  concentration) in Loch Leven for1980-83 (n=130): dashed portion corresponds tothe predicted decrease in pigment concentration ifthe phosphorus loading is reduced (see text)represent over 60% of the total loading. Other work(Bailey-Watts— unpublished observations) suggeststhat some of the current densest phytoplankton cropsare prevented from increasing further because ofphosphorus shortages. The application to Loch Levendata of the findings of an OECD programme onchlorophyll—phosphorus relationships (Anon 1982)indicates that a further reduction in mean chlorophylllevels to about 15 mg m-3 might be expected. If thiswere the case, a marked increase in water claritycould result, even though no significant increase inwater transparency has been found since meanchlorophyll levels were reduced from the earliervalues of 1000 mg m-3. The relationship betweenwater transparency and pigment levels is complex(Figure 11), but a marked change in water trans-parency is observed over that part of the range ofpigment concentrations of interest here.A E Bailey-watts and A KirikaReferencesAnon.  1982. Eutrophication of waters. Monitoring assessmentand control. Paris: Organization for Economic Co-operation andDevelopment.Bachmann, H.  1906. Le plancton des lacs écossais. Archsphys. nat., 20,  359.Bachmann, H.  1907. Vergleichende Studien Ober dasPhytoplankton von Seen Schott lands und der Schweiz. Arch.Hydrobiol. Planktonk.,3, 1-19.Bailey-Watts, A. E.  1974. The algal plankton of Loch Leven,Kinross. Proc. R. Soc. Edinb. B, 74, 135-156.Bailey-Watts, A. E.  1978. A nine-year study of the phytoplankionof the eutrophic and non-stratifying Loch Leven (Kinross,Scotland).J. Ecol.,66,  741-771.Bailey-Watts, A. E.  1982. The composition and abundance ofphytoplankton in Loch Leven (Scotland) 1977-1979 and acomparison with the succession of earlier years. Int. Revue ges.Hydrobiol. Hydrogr.,67,  1-25.Bailey-Watts, A. E.  1983. A re-assessment of phosphorusloadings to Loch Leven, Kinross-shire and their implications foreutrophication control by phosphorus removal. NaturalEnvironment Research Council contract report to the NatureConservancy Council. Edinburgh: Institute of Terrestrial Ecology.(Unpublished).Brook, A. J.  1957. Notes on freshwater algae mainly from lochsin Perthshire and Sutherland. Trans. bot. Soc. Edinb.,37,  114-122.Brook, A. J.  1958. Changes in the phytoplankton of someScottish hill-lochs resulting from their artificial enrichment. Verh.int. Verein. theor. angew. Limnol., 13,  298-305.Brook, A. J. 1965. Planktonic algae as indicators of lake typeswith special reference to the Desmidiaceae. Limnol.Oceanogr.,10,  403-411.Caines, L. A.  &  Harriman, R.  1977. Chemical investigations.(Loch Leven Research Group Report for 1976). (Unpublished).Cuttle, S. P.  1982. Sources of nitrogen in surface waters withinthe catchment of Loch Leven, Kinross-shire.Report funded bythe Nature Conservancy Council to Dr K. A. Smith, EdinburghSchool of Agriculture.Holden, A. V.  1976. The relative importance of agriculturalfertilizers as a source of nitrogen and phosphorus to Loch Leven.Tech. Bull. Minist. Agric. Fish. Fd,32,  306-314.Holden, A. V.  &  Caines, L. A.  1974. Nutrient chemistry of LochLeven, Kinross. Proc. R. Soc. Edinb. B, 74, 101-121Rosenberg, M.  1938. Algae and trout. A biological aspect of thepoor trout season in 1937. Salm. Trout Mag., no. 89, 313-322.Smith, I. R.  1974. The structure and physical environment of-Loch Leven, Scotland. Proc. R. Soc. Edinb. B, 74, 81-100.Vollenweider, R. A.  1968. Scientific fundamentals of theeutrophication of lake and flowing waters, with particularreference to nitrogen and phosphorus as factors ineutrophication. (DAS/CS1/68.27). Paris: Organization forEconomic Co-operation and Development.Acid rain effects on river catchments in north-west EnglandThere is increasing concern that acid precipitationmay have deleterious effects on some fresh watersin Britain. In England, the Lake District region in thenorth-west is receiving much attention. Here, therainfall is high (1000-4000 mm yr-1) and its pH islow - the mean value for 1978-79 was 4-4Freshwater and marine ecology 21(Nicholson et al. 1980). The geology of much of thearea is dominated by volcanic rocks with low calciumbuffering capacities. Consequently, fresh waters tendto be acidic and often contain high concentrationsof aluminium-a metal which is toxic to fish (Driscollet al. 1980).The North West Water Authority (NWWA) is investi-gating the chemistry and biology at approximately100 river and lake-side sampling points throughoutthe Lake District. About 50 of these points are onthe Rivers Esk and Duddon or their tributaries (Plate5). NWWA has already reported some of its findings(Prigg 1983). It has noted the absence of fish fromstretches of river where it had expected to find some,and is also concerned about fish mortalities whichhave occurred in the Rivers Esk and Duddon in recentyears, usually after periods of heavy rain.The Freshwater Biological Association (FBA) is alsostudying the area (NERC 1983). Its studies of anumber of freshwater tarns and lakes and of rainfall(Sutcliffe et at 1982) have led it to conclude thatthere has been no evidence for acidification of thewaters studied over recent years. Nevertheless, theFBA is continuing its studies, concentrating on highaltitude lakes and tarns, which are more likely to beaffected by acidification, and on the chemistry ofaluminium and its complexes, which are particularlyrelevant to the toxic effects on fish.A research project has been started, in collaborationwith the above organizations and others working onsimilar topics in the UK, to explore several relatedavenues of research.1. Water samples are being collected from many ofthe NWWA sampling points along the Rivers Eskand Duddon, with the assistance of NWWA staff.Analysing the samples for different soluble alumi-nium compounds will give some indication of thepossible toxic effects of this metal on fish in theserivers, as some aluminium compounds are muchmore toxic to fish than others (Driscoll et at 1980).2. The acidity of precipitation is being studied, usingrain collectors, with the aim of identifying aciddeposition 'episodes' (Fowler 8- Cape in press)and relating these to the continuous pH monitoringrecords of the NWWA from the Rivers Esk andDuddon.3. Sediments collected from tributaries of the Eskand Duddon are being analysed for a range oftoxic metals, to determine if metals other thanaluminium may affect the biology of these rivers.4. Using computing methods previously applied toland classification studies in ITE (Bunce 1979),an attempt is being made to classify catchments,currently sampled by the NWWA, into different

Eutrophication of Loch Leven

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