Hydrobiologia 326/327 : 305-310, 1996 .

305S. C. Lindstrom & D. J. Chapman (eds), Fifteenth International Seaweed Symposium.©1996 Kluwer Academic Publishers . Printed in Belgium .

Long-term changes in heavy metal loadings of Ascophyllum nodosum fromthe Firth of Clyde, UK

Fergus J. Molloy & Jeremy M. HillsUniversity Marine Biological Station, Millport, Isle of Cumbrae, Scotland, KA28 OEG, UK

Key words : Clyde, environmental impact, marine pollution, metals, seaweed

Abstract

The aim of this work is to describe changes in heavy metal concentrations in Ascophyllum nodosum from 1964 to1994 . Samples were collected from three sites in the Firth of Clyde and analysed for zinc, manganese, iron, copper,lead and nickel. The results were analysed using the multivariate technique Principal Components Analysis (PCA) .At the Wemyss Bay site there was a trend towards increasing lead and nickel over the study period, which couldnot be accounted for by local industrial activity . At the Hunterston site, two groups were well separated by thePCA ordination, based on manganese and zinc concentrations, which corresponded to land reclamation activitiesin the area . The separation of samples at the Ardneil Bay site correlated well with copper concentration and thiscorresponded to the termination of industrial effluent with heavy copper loadings . Other changes in industrialeffluent were also reflected in the Hunterston and Ardneil Bay site ordinations . The PCA technique highlighted theinterplay between metals . The work demonstrated the potential for using multivariate analysis of seaweed metalconcentrations in monitoring a posteriori the environmental impact of industrial change .

Introduction

The bioaccumulation of metals by brown seaweedsmakes them suitable for pollution monitoring studies(Phillips, 1980). Benthic seaweeds have the advan-tage of a sessile nature and macrophytic size, enablingrelatively easy collection of large quantities of tis-sue (Levine, 1984). Accumulation of metals has beenfound to be related to concentration in the water (Bryan,1969 ; Bryan & Hummerstone, 1973 ; Morris & Bale,1975 ; Myklestad et al., 1978), and influenced by sea-son (Bryan & Hummerstone, 1973 ; Fuge & James,1974), vertical distribution in the intertidal (Bryan &Hummerstone, 1973), and the particular portion of theplant which was analysed (Bryan & Hummerstone,1973 ; Myklestad et al., 1978 ; Eide et al ., 1980) .

Glasgow with the Clyde river, in the 19th and early20th centuries, was one of the world centres of indus-trialisation . The birth place of the steam engine, steamship and many other innovations, the Clyde historyis one of engineering and engineering development(Tivy, 1986). During the industrial era the popula-

tion of Glasgow grew from 77000 (1801) to 500 000(1868), 761000 (1900) and by 1931 the population was1 .1 million, with a total Clyde area population of 1 .4million (Porter, 1973) . With the increase in industrial-isation and population there was a concurrent increasein industrial and domestic sewage, this rendered theClyde river water `a risk to human health' by the endof the 19th century (Haig, 1986) . Action was taken in1894 with the construction of sewage treatment worksand the dumping of sewage sludge at Garroch Head inthe Firth of Clyde from 1904 to the present .

Post Second World War, the industrial focus of theregion shifted from Glasgow and the Clyde estuary tothe Firth of Clyde. Light petrochemical and pharma-ceutical industries were established in the Irvine area,a deep sea iron ore and coal unloading facility, an oilrig construction site and a nuclear power station wereall constructed in the Hunterston area, and an oil-firedpower station was built near Wemyss Bay (Figure 1) .There was a movement of some of the Glasgow pop-ulation to inland new-towns and to the west coast ofthe Firth of Clyde . These developments resulted in an

306

Figure 1 . Map of the study area . Towns, industrial activities andcollection sites are indicated.

increase in domestic and industrial sewage dischargeinto the Firth of Clyde . All of the coastal towns dis-charge sewage, with little treatment, directly into theFirth which is a popular sailing and recreational desti-nation .

The aim of this work is to describe changes in heavymetal concentrations in a brown seaweed species overa 31 year period, 1964-1994, from 3 localities in theClyde estuary . Rather than treating each metal in isola-tion, a multivariate approach was taken which charac-terises the metal loading of the seaweed in terms of theconcentrations of a set of metals . Such a data set canpotentially be used to retrospectively identify environ-mental change, in terms of heavy metals, within thelocalities of the study sites . The relationship betweenindustrial activity and metal loading within the Clydelocalities will be addressed .

Materials and methods

Seaweed analysis

Samples of Ascophyllum nodosum (L .) Le Jolis werecollected at 3 stations viz . Wemyss Bay (national gridref. NS 191 693), Hunterston (NS 179 517) and Ard-neil Bay (NS 188 483) . Two kilograms of whole plantswere collected in April of each year, cleaned of epi-phytes and epifauna, oven dried at 160 °C to constantweight. The oven dried seaweed was then milled andashed in a furnace at 430 °C overnight . The sampleswere originally collected for radionuclide analysis andwere subsequently stored in sealed containers until thepresent study .

All glassware and crucibles used in the analy-sis were cleaned in the surface active cleaning agent'Decon 90' (Decon Laboratories Ltd .), acid washed in25% HCl and rinsed in double distilled water . Subsam-ples (± I g) were re-ashed in crucibles at 500 °C for20 h, and 0.1 g of the re-ashed samples was placedin boiling tubes. The sample was digested with theaddition of 1 ml of 50% 'Aristar' grade HCI, and wasevaporated at 90 °C to dryness . The residue in theboiling tubes was dissolved in 2 ml of 'Aristar' gradeconc. HNO3 and heated at 100 °C with a dry heat-ing block for 70 h, with reflux stoppers . The refluxstoppers were sealed glass bubbles with a point pro-truding into the tube . After digestion the final volumeof the digest was taken up to 5 ml with double distilleddeionised (MilliQ) water. The solutions were trans-ferred to sealed plastic centrifuge tubes and spun at1398 x g for 15 mins .

Analyses for Zn, Fe, Mn, Cu, Pb and Ni were per-formed using a Pye Unicam flame atomic absorptionspectrophotometer with background correction . Thedigestion and analysis procedure was tested using cer-tified reference standard seaweed (NIES No . 9 Sargas-so, National Institute for Environmental Studies, JapanEnvironment Agency), and was found to be satisfacto-ry. Initially two subsamples were analysed per samplebut as these were not different, subsequent analysiswere performed on only one sample .

Samples were not available for every year between1964 and 1994. At Wemyss Bay samples for the peri-ods 1967-1973, 1981-1983 and 1992 and 1994 weremissing. At Hunterston 1976, 1978-1982 and 1984were missing . Ardneil Bay was the most complete dataset with only 1965, 1981 and 1994 missing .

Statistical analysis

A multivariate ordination technique, Principal Compo-nents Analysis (PCA), was used to summarise the met-al concentrations in the seaweed samples and describechanges between samples over time. PCA is an objec-tive ordination technique which permits projection ofa set of samples, described multi-dimensionally, intolow-dimensional space (Gauch, 1982) . The axes of thePCA are orthogonal .

The use of PCA in this study allows :

1 . The summary of seaweed samples in terms of theirconstituent metal loadings.

2. The identification of changes over time in metalconcentrations .

3 . The identification of the principal axes of variationin these data, and the metal species to which theseaxes are most related .

To achieve normal distributions in the metal con-centration data all metal concentrations were loggedprior to PCA analysis. For each PCA analysis eachmetal species was standardised such that the concen-trations ranged between 1 and 100 .

Table 1 . Summary of the heavy metal concentrations in Ascophyllum nodosumfor the time period 1964-1994 from sites in the Clyde estuary at WemyssBay, Hunterston and Ardneil Bay .

Mn

Cu

Pb

Ni

87.8 15 .0 2 .2 7 .440 .4 6.9 1 .9 3 .746 .6 5 .5 0.4 2.9204 .6

32.1

7.5

15.4

149.1 20.0 4.0 12 .373.5 8.5 3.6 9.866.3 9.2 0.8 4.2

369.3

46.7

19.1

48.3

106.7 13 .8 2.2 7 .178.9 6.3 2.2 5 .039 .1 5 .0 0.4 2 .2

424.9

28.1

12.1

26.1

Results

The statistical properties of the metal concentrationsat the three study sites are displayed in Table 1 . Theconcentrations of the metal species were variable at allof the sites over the studied time period, the standarddeviation generally being between half and the wholevalue of the mean . The Hunterston site had the greatestmean concentration for all of the studied metal species .Hunterston also had the maximum value for all metalspecies except for Mn which was higher at ArdneilBay .

PCA was used to compare the metal loadings in the3 studied sites, Wemyss Bay, Hunterston and ArdneilBay from 1964-1994 (Figure 2) . The first three axes ofthe PCA explained over 85% of the total variation inthese data suggesting that the metal species were notacting completely independently of each other. Thethree study sites were not greatly separated within theordination space meaning that the metal loadings weresimilar in the three sites . However, the Hunterstonsamples make up most of the points low on axis 1 andhigh on axis 2 (Figure 2) . Certain of the Hunterstonsamples had characteristic metal loadings .

The PCA axes scores were related to the heavy met-al concentrations to determine which metal species bestexplained the variation in the samples . PCA axis 1 wascorrelated to Ni (r= -0.86) and Pb (r= -0.86) and to a

307

Zn Fe

a) Wemyss Bay (n = 19)Mean

113.5 276 .6Standard deviation 66 .9 245 .6Range :

min 49.8 93 .7max 309 .4 1040 .6

b) Hunterston (n = 24)Mean 167 .5 700 .8Standard deviation 109 .2 314 .2Range :

min 75.0 262 .5max 432 .4 1209 .4

c) Ardneil Bay (n = 28)251 .6Mean 113 .8

Standard deviation 71 .8 145 .4Range :

min 46.1 110 .8max 348 .1 654 .8

308

Table 2. The metal species (up to 3) which are mostcorrelated (p<0 .01) to the first three axes of a PCAfor the three study areas (when more than one met-al species was selected they were placed in order ofdecreasing r) .

lesser extent Fe (r= -0.79) and Mn (r= -0.78) . PCAaxes 2 was most strongly correlated to Cu (r=0 .65) .The segregated samples from Hunterston were thusrelatively high in Ni, Pb, Fe and Mn, but also high inCu. From the 3 studied sites, certain of the Hunterstonsamples had the greatest metal loadings .

PCA analysis was carried out for each of the threesites separately over the 31 year time period (Figures 3,4 & 5). Changes in metal loadings in Wemyss Bay weresummarised using PCA, the first three axes accountedfor 87% of the variation in these data . There was atrend towards increasing lead and nickel concentrationover the time period (Figure 3) .

The Hunterston site was summarised using PCA,with the first 3 axes explaining 83% of the variation inthese data . There was a division between the samples ;the 1964-1977 samples tended to be at the lower end ofthe second axis, whereas the 1983-1994 samples tend-ed to be higher up the axis (Figure 4) . Data for 1978-1983 were unavailable. The second axis was relatedto manganese and zinc concentration in the seaweed,suggesting a lowering of manganese and zinc concen-trations in the last decade . The PCA ordination alsoindicated that the 1983-1994 group had higher leadand nickel concentrations than the 1964-1977 group .

At Ardneil Bay 89% of the variation in the data wasexplained by the first 3 PCA axes . The samples could bedivided into two periods, 1964-1980 and 1981-1993(Figure 5) . The samples from 1969 and 1975 were out-liers to these two groups, the reasons for which wereunclear. The early period, 1964-1980, were found gen-erally to be at the higher end of axis 1, whereas samplesfrom 1981-1993 were found high on the second axis .The second axis was related to copper concentrations(r= -0.90), suggesting that copper loadings have sta-bilised at a lower level over the last decade .

A summary for the three study sites showing themetal species (up to 3) which were most correlat-ed (p<0.01) to the first three PCA axes is given in

-2

-4

-3

-2

-1

0

1

2

3

4

axis 1Wemyss Ba,,HunterstonArdneil Bay

Figure 2 . Principal components analysis scores for heavy metal con-centrations at Wemyss Bay, Hunterston and Ardneil Bay from 1964-1994 (eigen-score : axis 1=0 .568, axis 2=0 .167) . Metals are repre-sented by arrows .

2

Ni

'Cu

axis 1Figure 3 . Principal components analysis scores for heavy metal con-centrations at Wemyss Bay, 1964-1994 (eigen-score : axis 1=0.504,axis 2=0 .199) . Metals are represented by arrows .

Table 2 . Two metals, Pb and Ni, appeared to be vary-ing in a similar fashion as they were both related tothe first axis of variation at the 3 study sites . Variationin copper appeared to be unrelated to other metals . AtWemyss Bay (axis 3) and Ardneil Bay (axis 2) copperwas selected as the only metal to which the axis wasrelated. These data suggest that the variation in cop-per over the last 31 years at the three sites was largelyuncorrelated to the variation in Pb and Ni .

640

740

/ Cu85

87 !101

1l

`~" 89Zn / 0i

-4

-3

-2

-1

0

1

2

3

88

x

Site Axis 1 Axis 2 Axis 3

Wemyss Bay Pb, Ni, Mn Zn CuHunterston Ni, Pb, Fe Mn, Zn FeArdneil Bay Pb, Ni, Mn Cu

-3 -2 0

axis I

Figure 4 . Principal components analysis scores for heavy met-al concentrations at Hunterston ; the two displayed groups corre-spond to 1964-1977 and 1983-1994 (eigen-score : axis 1=0.43,axis 2 = 0 .255) . Metals are represented by arrows .

r

a

axis 1

1 2 3

0 64-7783-94

69 0

75

3

C 64-80- 81-93

Figure 5. Principal components analysis scores for heavy metal con-centrations at Ardneil Bay ; the two displayed groups correspond to1964-1980 (except 1969 and 1975) and 1981-1993 (eigen-scores :axis 1 = 0 .597, axis 2=0.17) . Metals are represented by arrows .

Discussion

Prior to the 2nd World War the source of most of thepollutants in the Firth of Clyde came from Glasgow andthe lower Clyde estuary, becoming more dilute withdistance down stream . This is no longer the case and isevidenced by the lack of separation of the three sites onthe combination PCA ordination . Nowadays it appearsthat local inputs are more important in determining theheavy metal loadings of the study areas .

309

The Wemyss Bay collection site is adjacent to asmall town and a non-operational oil-fired power sta-tion, where there have been no industries of note inthe area for at least thirty years before this study . Thetrend towards higher lead and nickel loading from thebeginning to the end of the sampling period cannot beexplained by local industrial activity but may have beencaused by an increase in atmospheric lead or higherlead and nickel concentrations emanating from furtherup the Clyde river.

In contrast, industry has been very active in theHunterston area . From the beginning of the data set to1978/1979 land was reclaimed for the nuclear powerstation, the iron ore and coal unloading jetty and the oilrig construction yard . In total 136 ha of the intertidalmud flats were reclaimed (Clokie & Boney, 1980) . ThePCA for the Hunterston site (Figure 4) separates thepost reclamation years from the reclamation years . Theseparation is strongly correlated to a decrease in man-ganese and zinc in the post-reclamation years suggest-ing that these metals were introduced through sedimentdisturbance and dumping of infill . Other sources ofpollution in the Hunterston area are of a more episodicnature and include loss of iron ore and coal dust fromthe jetty (Venn & Boney, 1984), occasional flooding ofthe rig yard and dredging of a deep channel on com-pletion of a project, and the pre-operational cleaningphase of the power station prior to going on line, 1963-1964 for A station and 1973-1974 for B station . Thispre-operational cleaning phase entails the cleaning outof all the sea water coolant circulating pipes and con-densers . The Hunterston collection site is close to thecoolant outfall and so potentially would be stronglyeffected by it . The cooling sea water was dosed withferrous sulphate, to protect the condenser pipes, on aregular basis from 1964 to 1982; dosing stopped withthe use of titanium pipes . The sewage sludge dumpedoff Garroch Head (Figure 1) did not influence met-al levels in the vicinity of the study sites (Mackayet al., 1972). The metals which correlate with the firstaxis (nickel, lead and iron) probably came from theseepisodic sources .

Ardneil Bay is 10 km north of Irvine, where thereare a number of industrial outfalls . Imperial ChemicalIndustries (ICI) petrochemicals discharged effluentshigh in copper until 1981, the organics division of ICIswitched their discharge from the Garnock River estu-ary to a long sea outfall off Irvine. Also in 1981, SmithKline Beecham Pharmaceuticals increased the volumeof their marine outfall near Irvine (Clyde River Purifi-cation Board, 1981) . The separation of the two major

310

groups along axis 2 of the Ardneil Bay PCA is basedon copper concentration, 1981 to 1993 having lowercopper levels . This correlates well with the decreasein copper input with the termination of effluent fromICI petrochemicals. Axis 1 on the PCA correlates withlead, nickel and manganese. The apparent increase inthe latter part of the data set can be explained by theincrease in effluent output by Smith Kline BeechamPharmaceuticals and the commencement of effluentdischarge by ICI organics .

Comparison of metal concentrations between waterbodies is difficult using this method of collection andanalysis as results are strongly influenced by the prox-imity of outfalls, rivers, sediments and sediment dis-turbance . Sampling the water column for metals is dif-ficult as contaminants are usually in very low concen-trations (Phillips & Rainbow, 1993) and contaminantsmay vary widely with time (Phillips, 1980) . Further-more, comparison of these results with those of previ-ous authors is difficult as different seaweed species ordifferent portions of the same species have been used .

The utilisation of seaweeds for biomonitoringheavy metals, coupled with multivariate ordinationprocedures, identified the major changes in industri-al activity in local areas of the Clyde over the studiedtime period . Besides permitting an objective summa-ry of heavy metal changes over time, the multivariateapproach identified metals which appeared to be oper-ating in concert and those acting independently . Suchinsights into the interplay between metals might haveproved more difficult to identify using uni- or bi-variateanalyses of single metals . This work highlighted thepotential for the use of multivariate analysis in moni-toring the environmental impact of industrial change .Such an approach could potentially be used, for exam-ple, in post-Environmental Impact Assessment (EIA)monitoring, which, at present is sadly lacking (Speller-berg, 1991) .

Acknowledgments

The authors would like to thank Scottish Nuclear,Hunterston for allowing access to their ashed seaweedcollection and for the use of their analytical equipment.FJM is also the recipient of the Scottish Nuclear Sea-weed Fellowship . JMH was supported by the SheinaMarshall Fellowship and The Royal Society .

Clyde River Purification Board, in particularR. Kerr, and Dr P Barnett from the Marine Biological

Station Millport helped with descriptions of industrialchange and sewage contents .

References

Bryan, G . W ., 1969 . The absorption of zinc and other metals by thebrown seaweed Laminaria digitata . J . mar. biol . Ass . U .K . 49 :225-243 .

Bryan, G . W. & L . G . Hummerstone, 1973 . Brown seaweed as anindicator of heavy metals in estuaries in south-west England . J .mar. biol . Ass . U .K . 53 : 705-720 .

Clokie, J . J . P. & A . D. Boney, 1980 . The assessment of changes inintertidal ecosystems following major reclamation work : Frame-work for interpretation of algal-dominated biota and the use andmisuse of data . In : The shore environment . Vol . 2 (SystematicsAssociation special volumes ; 17B) . Price, J. H ., D. E. G. Irvine,& W. F. Farnham, (eds). Academic Press Inc . London : 609-676 .

Clyde River Purification Board, 1981 . Seventh annual report . EastKilbride, Glasgow : 74 pp.

Eide, I ., S . Myklestad & S . Melsom, 1980 . Long-term uptake andrelease of heavy metals by Ascophyllum nodosum (L .) Le Jol .(Phaeophyceae) in situ . Envir. Pollut . Ser. A . 23 : 19-28 .

Fuge, R . & K . H. James, 1974. Trace metal concentrations in Fucusfrom the Bristol Channel . Mar. Pollut . Bull . 5 : 9-12 .

Gauch, H . G ., 1982 . Multivariate analysis in community ecology .Cambridge University Press, Cambridge : 298 pp .

Haig, A . J . N ., 1986 . Use of the Clyde Estuary and Firth for thedisposal of effluents . Proc . r. Soc . Edinb . 90B : 393-406.

Levine, H. G ., 1984 . The use of seaweeds for monitoring coastalwaters . In : Algae as ecological indicators . Shubert, L . E. (ed .) .Academic Press Inc., London : 189-210.

Mackay, D . W., W. Halcrow & I. Thornton, 1972 . Sludge dumpingin the Firth of Clyde . Mar. Pollut. Bull . 3 : 7-11 .

Morris, A. W . & A . J . Bale, 1975 . The accumulation of cadmium,copper, manganese and zinc by Fucus vesiculosus in the BristolChannel . Estuar. coast . mar. Sci . 3 : 153-163 .

Myklestad, S ., I . Eide & S . Melsom, 1978 . Exchange of heavymetals in Ascophyllum nodosum (L .) Le Jol . in situ by means oftransplanting experiments . Envir. Pollut. 16: 277-284 .

Phillips, D . J . H ., 1980. Quantitative aquatic biological indicators :their use to monitor trace metal and organochlorine pollution .Applied Science Publishers, London.

Phillips, D . J . H . & P. S . Rainbow, 1993 . Biomonitoring of traceaquatic contaminants . Chapman and Hall, London : 371 pp.

Porter, E ., 1973 . Pollution in four industrial estuaries . Her Majesty'sStationery Office, London .

Spellerberg, 1. F., 1991 . Monitoring Ecological Change . CambridgeUniversity Press, Cambridge : 320 pp.

Tivy, J ., 1986 . The geography of the Firth of Clyde . Proc . r. Soc.Edinb ., 90B : 7-23 .

Venn, T. & A . D . Boney, 1984 . Cargo spillage at an iron ore unloadingterminal . Mar. Pollut . Bull . 15 : 25-28 .