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SOME EFFECTS OF SMELTER POLLUTION UPON AQUATIC VEGETATION NEAR SUDBURY, ONTARIO EVILLE G o R H . ~ ~ ~

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Botany Department, University of Toronto, Toronto, O?ttario AND

ALANG. GORDON Research Branch, Ontario Departnzent of Lands and Forests, Forest Biology Laboratory, Sazill Ste iVIarie, Ontario Received December 6 , 1962

Abstract T h e numbers of submerged and floating macrophyte species present ill 29 ponds and lakes are inversely related to dissolved sulphates, concentrations of which rise sharply within about 4 to 5 miles of the srrielters. A l t h o ~ ~ gpollution h often leads to strong acidification, numbers of species are low even where sulphuric acid is almost wholly neutralized, and waters are above p H 6 . Because sulphate ions are unlikely to be toxic a t the levels e n c o ~ ~ n t e r eand d , since pollution also increases the concentration of heavy metals in the waters, it is suggested t h a t these may reach toxic levels near the s~nelters. Leptodictyzinz riparizim and Eleocharis acicularis v. szib?lzersa seem to be most tolerant of smelter pollution, while Ulriczilaria uzilgaris and Potamogeto?~epiAydrus v. ?tuttallii appear rather se~lsitiveto it.

Introduction 111the course of studies upon smelter pollution and its ecological significance near Sudbury, Ontario (Gorham and Gordon 1960a, 1960b), a sharp rise in sulphate concentration of lake and pond waters was observed within about 4 to 5 miles of the smelter chimneys, owing to oxidation and fallout of sulphur dioxide emitted during the smelting process. I n order to examine the effect of smelter pollutio~lupon aquatic vegetation, a floristic survey of 29 lalies and ponds was undertaken.

Methods During the summer of 1959, 102 lakes and ponds were visited by car or helicopter, and water samples were collected for ailalysis of pH, calciunl, and sulphate (Gorham and Cordon 1960b). I n a representative selection of 14 waters the aquatic vegetation was surveyed, between Septenlber 5 and 9, by collecting and pressing material of every species of floating or submerged nlacrophyte (including bryophytes and Characeae) observed in 20 minutes swimming by two men equipped with fins, face masks, and schnorkel breathing tubes. Between August 16 and 19, 1960, a further 15 waters were examined, including 3 not visited in 1959. Species with enlergent leaves were not included, unless growing wholly submerged, as was fl-equently the case with Lysimaclzia terrestris, and once with Jzinciis militaris, which has very characteristic submerged leaves. . The locations of the lalies and ponds are given in Table I. Canadian Journal of Botany. Volun~e41 (1963)


TABLE I Numbers of aquatic macrophytes and chenlical composition of Sudbury waters La lie No.

Miles to smelter

Direction from smelter

S~nelter*

Sod, meq/1.

meq/l.

Ca,

PH aerated

S. N. NW. N. N\V. SSW. N. NW. WSW. NNE. NE. SSE. NNE. -

*F

.-

-

6.9 7.0 7.4 10.6

SSE. SSW. S\V. SW.

c-

CC C CC

0.49 0.63 0.46 0.51

0.27 0.48 0.28 0.31

5.6 7 .0 6.6 6.3

29 26 95 94 27 28

16.4 19.2 19.4 19.8 23.4 24.2

S. SW. hTNE. WN\Y. SW. SW. WNW. WNW. WNW.

CC CC 1; CC CC CC CC CC CC

0.36 0.24 0.37 0.24 0.29 0.39 0.25 0.27 0.29

0:21 0.27 0.17 0.18 0.34 0.41 0.25 0.28 0.25

4.6 7.2 4.4 6 .O 7.4 7.4

= Falconbridge. CC = Copr)er Cliff. C = Coniston smelter. = very severe, S = severe, C = considerable, M = moderate,

tVS

-

75 23 33 24

N

=

not obvious (Gorha~na n d Gordon 1961b).

Damage to terrestrial vegetationt

No. species aquatic ~nacrophytes


0

TABLE I1

8 x

Submerged and floating macrophytes identified in five or more lakes and ponds 8 1

Lake number Total no. species per lake

12 53 0 3 4

11 5 4 65 3 2 2 4

14 5 6 4 4 4 5 8

15 6 9 21 7 5 4 1

17 2 2 75 1 8 7 1

23 33 24 7 1 0 6

25 9 6 29 1 1 1 0

k 26 95 9 4 1 7 1 0

27 2 8 103 105 104 2 4 1 8 1 1 8

$ u

Leplodirlytmnr riparilr?ir* Eleoclraris acicrrlaris v. srtblnerso Jtrrtcrrs pelocarplrs I . srrbntersrrs Sagillaria (sp. or spp.) Erioca~rlonseplairgrrlare Isoeles nrtrricala Nylirphaea odorala Lobelia d o r l ? i ~ a i z ~ ~ a Isoeles riparia Myrioplrylltr?n lote!llr?,z N ~ r p h a r(sp. or spp.) Ulric~rlariaurrlgaris Polali~ogelo?~ epillydrlis v. ?rnllallii ,

Miles from nearest srnelter

'

0

0 1

2

3

4

5

10

15

20

30

35

*Might be in 11. 22. 25. 95, and 96, frorn which mosses \\.ere recorded in 1959. These moss samples have been rnislaid, and might represent either Lcplodiclyrrnt riparilr?ir or Drepa?rocladris ptrilairs.

g 2 =! z0


T A B L E I11 Submerged or floating macrophytes identified in fewer than five lakes and ponds I-Iigher plants

Brasenia scltreberi Elatine minima Eleocltaris robbiftsii Glyceria borealis Hippuris virlgaris Jirnctrs militaris Lysimachia terrestris A~yrioplzyllzrntfarwelli Najas jlexilis Polygonrrm anzphibiitm Potamogeton amplifolius P . gramineus P . pectinatus P. pusill~r~~ P . robbinszz P . spirillus Sparganiztnz fEuctuans Utricularia gibba U . intermedia U. minor U. -pirrpurea -

Lalces

27, 28, 104 25 29 69 104 103 23, 26, 28, 103 28, 103 28 17, 69 28 17, 27, 28 95 23, 25, 104 27 28, 94, 103 25, 26, 33, 1 0 4 23 96, 103 95 94, 96

*Migilt also be in 11, 22, 25, 95, and 96; mosscs from 1959 mislaid. tprobahly also in 25. 96; mosscs from 1959 mislaid. $Appearing healthy and natura!ized in several feet of water.

Bryophytes

Cladopodiella fEuitans Drepanocladus fEiritans* Fontinalis novae-angliaet Polytricltztm comnzunef

> n

Lakes

2'3

4, 21 23, 29, 9 4 26, 94, 104 54

w

> Z

z

0

c F

z> P

g m

0 1 >

2: j

6 P

.. rp

+.

a rn u

-

GORHAM A N D GORDON: SMELTER POLLUTION

375


Results Table I also gives the total number of species recorded for each body of water, together with data on water che~nistryand a visual estimate of damage to nearby terrestrial vegetation, included from the earlier study. Within 2 iniles of the smelters, the total number of species observed ranged from 0 to 4; between 2 and 5 ~nilesthis range increased to between 2 and 8 species; wllile outside 15 miles the range was frol-rl 6 to 24, except for a single lake (No. 105) where only 1 species was recorded. Ranges for dissolved sul].>hatewere 1.16 to 2.75 mecl/l. within 2 miles and 0.24 to 0.47 meq/l. outside 15 niiles. For pH, these same ranges were 3.3 to 6.1 and 4.4 to 7.4; and for calcium 0.4 to 1.0 meq/l. and 0.2 to 0.4 meq/l. Where Table I records damage n of species recorded was 8, as to terrestrial vegetation, the ~ n a x i r n u ~n~unlber against 24 where such damage was not obvious. Table I1 shows the distribution of all the species identified in five or more sites, and thus gives an idea of the aquatic flora typical of this area. (Some species may have occurred elsewhere as well, but not in identifiable form or r Sagitin the area traversed by swim~ning;and the records for N . ~ ~ p h aand taria may refer to Inore than one species, since flowers and fruits were seldom s f. available.) Both Eleoclzaris acicl~larisv. s7~bmersaand J ~ ~ n c z lpelocarpz~s submersz~swere difficult to identify conclusively fro111 keys, but finally compared well with material of the submerged forms of these species in the herbarium a t Toronto. Table 111 rounds o u t the floristic picture by giving species identified in fewer than five waters. Clzaraceae were not identified to species. Some species appeared relatively tolerant of pollution; for example Leptodictyzlm riparium (a moss) and Eleocharis acicz~larisv. submersa were found within 2 miles of the smelters. Leptodictyl~msp. has been recorded by Yoshimura (1935) as usually covering the bottom of inorga~licacid lakes in Japan, where volcanic waters rich in sulphuric acid are common. Polytrichun~.has also been recorded as a natural inhabitant of an acid Japanese lake, bearing out conzmzlne ill one of the Sudbury the apparent naturalization of Polytriclz~~m laltes (No. 54, pH 4.2, So4 1.16 nzeqjl.). I t should also be noted that wefts of algae covered much of the littoral zone in several of the most highly polluted waters, which were thus by no means devoid of vegetation. On the other hand, Utricz~lariavl~lgarisa~nclPotamogeton ep,iltydrz~sv. nt~ttalliiwere only observed beyond 15 nliles fro111 the smelters, where, however, they occurred in 5 of the 10 waters investigated.

Discussion I t is apparent from Table I that s~nelterpoll~ltiondrastically reduces the aquatic flora in the immediate vicinity of Sudbury. And while the present study was co~lcernedwith only floristic diversity, i t was also evident t h a t heavy pollutio~lgreatly reduces productivity, so that in laltes with few species the standing crops of nzacrophytes are com~nonlyvery low. The area subject to severe pollution lies within about 4 to 5 miles of the three smelters, as shown in Fig. 1, where sulphate conce~ltration(x) is plotted versus distance from the nearest smelter (2). T h e regression is adequately expressed by the equation = 1.73 z-0.555 , with the standard error of estimate f 0.13 n~eq/l.,and the correlation coefficient r = -0.92, although the log/log plot inset in Fig. 1 shows a slight tendency t o be curvilinear.

376

CANADIAN JOURNAL O F BOTANY.

VOL. 41, 1963


X

I LOG DISTANCE

I

I

5

0

10 DISTANCE

4

I

15 FROM

20 25 NEAREST SMELTER miles

30

35

z

FIG. 1. The relation between sulphate concentration in pond and lake waters and distance from smelters (point represents lake No. 105, see text).

+

LOG SULPHATE

I 0

I

0.5

1 .O

SULPHATE

1.5

2 .O

2.5

3.0

X

m e q / I.

FIG.2. T h e relation between the number of species in a pond or lake arid its sulphate corice~ltratiorl(the solid line includes all lalres, while the brolreil line excludes lalie No. 105, represented by point +).

GORI-IAM AND GORDON: SlMELTER POLLUTION

The relationship between floristic abundance and pollution is well shown by plotting species number (y) versus sulpllate concentration (x), as in Fig. 2. In this case the regressioil equation is y = 4.13 x-0,72s,as iildicated by the solid line in Fig. 2, with the standard error of estimate 2.0 species, and the correla-0.60. If lake KO. 105, with its u~liisuallylow species tion coefficierlt r number (see in Fig. 2), is onzitted, the correlation coefficient r = -0.79, and the regressioil ecluation becomes y = 4.15 x-O."~, as sl~ownby the brolcen line in Fig. 2, with the standard error of estimate 1.6 species. T h e divergeilce of lalre No. 105 from the general group is evident froin the log/log plot inset in Fig. 2, b u t this lalte is in no way unusual in its level of sulphate, calcium, or acidity (see Table I). I t differs physically froni the others in having a bottom composed largely of boulders, but a few sand patches were observecl which might have been expected to support a rather greater variety of flora. Unfortunately its illaccessibility prevelits further investigation. Whether lalte No. 105 is included in the regressioil maltes little differeilce t o the relationship illustratecl in Fig. 2, froin which it is clear that sites subject to heavy sulphur pollutioil exhibit a n~arlieddegree of floristic impoverishment. This seenls unlilcely to be caused by abu~ldanceof sulphate ion, which has beell analyzed merely as a good pollutioi~index, and inay be due in part to the high levels of acidity in many such waters (e.g. Nos. S, 11, 12, 14, all below pH 4). S t r o i ~ gacidity is not accoinparlied by low calcium levels, as is so often the case in acid bog lalres (Gorham 1957), b u t rather by higher concentrations, owing to increased weathering of calcium from the soils by sulphuric acid. Moreover, three waters with high sulphate levels are not very acid (Nos. 56, 65, 69, all above pH 6), and yet arc floristically poor, the nulnbcr of species railging from two t o five pel- lake. Since it is dificult to imagine that sulphate itself is toxic a t the levels observed (0.5 to 1.9 meqjl.), the cause of floristic poverty must be sought elsewhere. In the course of chemical analysis it was found that heavv metals were abundant in waters collected near the smelters. and had to be complexed by cyanide before satisfactory calciuin titrations could be carried out. These heavy metals might be presumed to collsist mainly of the copper and nickel smelted a t Sudbury, b u t others (e.6. iron, manganese) might also be leached from rocks and soils under the influence of sulphuric acid produced by oxidation of sulphur dioxide froin the smelter chimneys. In addition, prelimiilary investigations have revealed a strong positive correlatioll between copper and sulphate in melted snow collected a t varying distances XNW. froin the Falconbridge smelter, with high concentrations of both near the chimneys, as shown in Table IV. I t therefore seems likely that heavy inetals such a s copper, and perhaps other elements (nickel has not so far beell investigated), inay reach toxic levels in waters subject to severe aerial pollution, and so account for species impoverishment even where the ~ v a t e r sare not strongly acid. Indeed, it is quite conceivable t h a t high acidity is of minor importance, and that heavy metal toxicity is the major factor limiting floristic variety in waters receiving much fallout from the Sudbury smelters. In this connection studies of the relative tolerance of species such as Eleocharis acic~ilarisand Potamogeton epihydrzis v. nzittallii for high levels of both acidity and copper might prove informative.

"+"


377

-

CANADIAN JOURNAL O F

BOTANY. VOL.

41. 1963

TABLE IV Chemical analyses of snow samples collected on the ground near Falconbridge, February 12-15, 1960 -


Distance NNW. of smelter, ml

PH

sod, meq/l.

Ca, meq/l.

Cu* acid-sol. /%/I.

4.3 4.6 4.4 4.5

0.10 0.03 0.05 0.03

0.018 0.010 0.015 0.013

100 Ca. 5