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Marine algae as collectors of iron ore dust
Volume 9/Number
7 ' J u l y 1978
maintained. Otherwise there would be several hundred thousand more great whales in the world than there are now. This is why I personally support the ten-year whaling moratorium, agreed to almost unanimously at the Stockholm U.N. Conference on the Environment, and advocated by both the International Union for Conservation of Nature and by the World Wildlife Fund, as well as by m a n y other conservation bodies, such as the Fauna Preservation Society and the New York Zoological Society. This moratorium has never been accepted by the International Whaling Commission, whose national representatives regularly vote down the pledge given by their countries at Stockholm in 1972. The extermination tradition of hunter-gatherer man is too strong. What has happened to the great whales happened earlier to the fur seals, all stocks of which were at one time or another brought below harvestable level by the operation of the Colin Clark effect. The sub-antarctic Kerguelen fur seal, curiously named Arctocephalus tropical&, has the melancholy distinction of having been 'exterminated' three times over. The first occasion was in the 1820s, when a million and a quarter skins were being harvested annually. Fifty years later the colonies had revived enough for sealing to start again but, after an average of 45 000 skins had been taken for some sixteen years, the southern race was believed to be extinct. There was a minor resurgence of sealing when 800 skins of the northern race were taken from Prince Edward Island in the southern Indian Ocean in 1921. Not until 1929 was the southern race rediscovered, on Bouvet Island, and since then it has recovered more widely, and for instance there were 33 000 fur seals on Bird Island off South Georgia by 1962. All are currently protected, but there is some argument as to whether sealing can safely start again. If it does, the only safe prediction that can be made is that excessive quotas will be fixed, and the southern fur seal will sooner rather than later become too scarce to harvest once more. The southern
elephant seal Mirounga leonina, to which the sealers transferred when they had knocked out the fur seal, has had a similar chequered history. The much publicized harp and hood seal fishery off Newfoundland is still in a fairly early stage of decline, but trends already established show that sooner or later the Canadian Government will be forced to eat its words, and admit that it has allowed too large quotas to be fixed and operated. The most hopeful story in the long and shameful history of the exploitation of marine m a m m a l s - a n d the same thing is happening with marine turtles - is that of the Pribilof fur seal Callorhinus ursinus. In 1786, eighteen years after the demise of Steller's sea cow, the Russian navigator Gerassim Pribilof discovered the breeding ground of this seal on the two islands that still bear his name. There were then perhaps two and a half million seals in the rookeries. Within twenty years the sealers of Russia, Canada and the United States had brought them to the verge of extinction. Throughout the 19th century the Russians and, after the islands were sold to the U.S. in 1867, the Americans operated a stopgo system of moratoria to allow the stocks to build up again. In the 1880s however, the British and Canadians started pelagic sealing on a large scale, and this brought the final crisis. By the time the riparian states were persuaded to agree to prohibit pelagic sealing in the North Pacific in 1911, only 200000, less than a tenth of the original stocks, were left. Under planned United States management stocks have built up again to well over a million and a half, and there is now a carefully controlled harvest, which is an important addition to the Alaskan economy, with Japanese and Canadian sealers each being allotted fifteen per cent of the proceeds. So it can be done, but only by a single strong and conservation-minded government. If it is left to the hunting instincts of hunter-gatherer man, as personified in the modern nation state engaging in a free-for-all, any animal stock of any economic value, terrestrial or marine, will be exterminated.
)d~trine Pollution Bulletin. Voi. 9. pp. 175-180 C~)25-326XTS/071~I -OI75 $02.000
Pergamon Press Ltd. 1978. Printed in Great Britain
Marine Algae as Collectors of Iron Ore Dust A. D. BONEY
Department of Botany, University of Glasgow, Glasgow G12 8QQ, Scotland Marine algae from intertidal habitats, when shaken in iron ore dust suspensions in seawater, take up appreciable quantifies of the dust load. The quantities taken up vary with the modes of thallus construction. Considerable quantities of ore dust are retained by the plants after
shaking for periods of up to 15h in dust free seawater. Marine algae can be used as a monitoring system for ore dust loading of seawater due to accidental spiilages in the vicinity of ore unloading terminals.
175
Marine Pollution Bulletin
Current industrial developments in the Hunterston region of the north Ayrshire coast in the Firth of Clyde, Scotland, include the construction of an iron ore unloading terminal to be linked with an inland processing plant. This constitutes the first stage of a major industrial development in the area. The deep waters of the upper Firth have facilitated this development, and will allow large ore-carrying ships to anchor close inshore for unloading. Construction of an offshore jetty and of a covered conveyor belt transportation system for carrying the crushed ore to storage areas has been in progress since 1975 and is due to become operational early in 1978. A base-line study of the benthic marine algae in the Firth, with due regard to the area designated for industrialization, was commenced in 1972 with grant support from the Natural Environmental Research Council up to 1975, and with continuing grant support from British Steel since then. As part of this work on marine algae, attention has been focused on suspended iron ore dust as an environmental factor in the sea. Whilst it is clearly not the intention of British Steel to offload into the sea a valuable commodity transported at considerable cost from foreign ore deposits, the possibility of accidental spillage, or of windborne deposition in the sea must not be overlooked. The research programme instituted, of which the present work forms part, may be regarded as a type of 'early warning' system, in which answers to environmental questions are being sought before the industrial complexes become operational. There is little available information on the effects of suspended inorganic particulate matter on marine algae. Five categories of inorganic particulate matter have been described (Johnston, 1976): (I) Dredged 'spoil', (2) 'acid iron waste', (3) 'red mud' (mainly alkaline), (4) coal wastes and (5) china clay residues. Of these, dredged 'spoil' is the large-scale transportation and deposition of dredged sea-bed material, and will influence benthic organisms both by being removed and later deposited elsewhere. China clay residues tend to be mainly deposited in rivers and estuaries although some inshore deposition does take place. Each of the remaining three categories involve forms of particulate iron compounds. Acid iron waste consists of sulphates and chlorides of iron dissolved in strong solutions of the corresponding mineral acids, and contains the iron residues remaining after the separation of titanium from the minerals illmenite and rutile. Red mud is the alkaline iron waste after the manufacture of alumina from bauxite. Coal wastes are similarly rich in particulate iron, either as aqueous (acid) wastes containing both iron and manganese salts, or as iron-rich solid waste 'leachates' from coal refuse dumped offshore, or in coastal 'bings' unguarded from the sea. All these residues form hydrated iron oxide following their release into the sea, and as such will constitute part of the silt load. Suspended particulate matter, if present in sufficient quantity, will cut down light penetration and form surface coatings on seaweeds, with resulting decreases in growth rates and possible changes in species diversity. Animals using seaweeds for attachment of eggs will be affected, as well as those which use the plants as food and as substrata for settlement. The 176
plants will also be affected by the smothering of sporelings and juvenile stages, and possibly from the blockage of reproductive 'pores' in fertile plants. Effects of diminished light intensity due to silt load in reducing Laminaria photosynthesis have been reported (Bellamy & Whittick, 1968; Bellamy et al., 1969, 1972), and effects on growth form (Burrows & Pybus, 1971). Silting of rock faces prevents spore settlement in Laminaria (Burrows & Pybus, 1971), and Himanthalia (Moss et aL, 1973). There is a lack of quantitative data on algae as dust collectors. The present work is an examination of the role of marine algae of different forms of thallus construction as collectors of particulate iron compounds, particularly the oxides of iron present in iron ore dust.
Materials and Methods Four samples of iron ore dust were supplied by British Steel: 'Bolivar', 'Lac Jeanine', 'Mang Ore' and 'Tazadit'. Mang Ore is a black powder; the remaining three are red. Particulate size distributions were determined using a Coulter Electronic Counter Model TA 1 I. Ore dust suspensions in filtered seawater were shaken with algal thalli in conical flasks on a laboratory orbital shaker at constant speed. Retention of ore dust by algal thalli was measured using round bottomed flasks containing similar volumes of seawater, and using a laboratory flask shaker set at a speed which was constant for all of the experiments. The transmission of radiant energy through membranaceous thalli after coating with ore dust was measured using an Instrumentation Specialities Company Model SR Spectroradiometer with an iodinequartz light source in a dark-room. Measurements were made with the moist algal thalli spread on the base of a petri-dish at a fixed distance from the light source, and with the probe of the spectroradiometer fixed against the underside of the dish. The quantities of ore dust remaining after shaking the suspensions with algae, or after the dust-laden algae had been shaken in seawater, were determined gravimetrically in pre-weighed and dried Gooch crucibles lined with magnesium carbonate. Each crucible plus ore dust was dried to constant weight over several days at 60°C in an oven, and stored for 6h in a desiccator until weighed on each occasion. Five species of marine algae were used in the experiments: Rhodophyceae Porphyra umbilicalis (L.) J.Ag. Plumaria elegans (Bonnem.) Schm. Polysiphonia lanosa (L.) Tandy Chlorophyceae Cladophora rupestr& (L.) K0tz.
(membranaceous) (plumose branching) (much branched, dichotomous) (abundant branching, plant densely tufted)
Phaeophyceae Pelvetia canaliculata (L.) Dcne et Thur. (a 'fucoid' alga)
All are of common occurrence on the shores of the Isle of Cumbrae in the Firth of Clyde. Plants were used as soon as possible after collection. Storage for 1-2 days in polythene bags in a refrigerator was sometimes necessary, and plants stored in this way were equilibrated in filtered seawater at room temperature (ca 20°C) for 12 h prior to an experiment.
Volume 91Number 7 / J u l y
1978
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Fig. 1 Particle diameter size groups of the ore dust samples. 'Tazadit' measured immediately after shaking with seawater, the remaining ore dust samples after overnight suspension in seawater.
Results Size ranges of ore dust particles in sea water If measured quantities of ore dust are mixed with similar volumes of distilled water and seawater, and the rates of sedimentation compared, it will be observed that the dust in seawater settles out more rapidly. This aggregation of the fine particles is shown in Fig. 1, in which the particle size distributions are compared. The 'Tazadit' sample was measured within 60 min. of mixing with the seawater, and the remaining three measured after several hours had elapsed. After thorough mixing with seawater, the particles were mainly in the size (diameter) range of 8-25 Mm.
Transmission of radiant energy through the ore-coated membranaceous thalli ofPorphyra umbilicalis In these experiments similar fresh weights of Porphyra umbilicalis were shaken with 0.5 g of ore dust in 100 ml filtered seawater. Porphyra thalli vary in colour on the shore, and comparisons were first made of energy transmission by 'pale brown' and 'dark' coloured plants (Fig. 2 A, B). Energy transmission through the petridish (GD), compared with the dry and wet thalli of the pale brown coloured Porphyra showed that greater quantities of radiant energy are reflected and retained by the dried than by the wet thalli. This can be linked
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Fig. 2 Spectral intensity measurements of radiant energy transmitted through pale-brown coloured (B) and dark coloured (D) Porphyra thalli. (A) Pale-brown thalli, wet and dry. (B) Dark thalli, wet and dry. (GD Glass vessel). with the protection such dried thalli can afford to underlying algae during periods of intense insolation at times of exposure to air. With the dark Porphyra thalli such differences in energy transmission by dry and wet thalli are less marked. The energy absorbing and reflecting properties of ore-dust coated dark Porphyra thalli are shown in Fig. 3A. This shows the radiant energy not transmitted at each wave length. These values were obtained by comparing the transmission through the glass vessel and the untreated and dust-laden thalli. The coating with 'Mang Ore' dust produced maximum absorption and reflection, with the more significant effects being observed between 550-750 nm. After shaking the dust-laden thalli for 3 h in filtered seawater, the measurements of radiant energy absorption and reflection showed that some ore dust coating remained (Fig. 3B), but whilst 'Mang Ore', 'Lac Jeanine' and 'Bolivar' formed the denser coatings initially, after shaking in seawater 'Tazadit' dust would seem the more tenaceous. Some persistent adherence of ore dust to the mucilaginous outermost layers of Porphyra is evident from these experiments.
Retention of "Bolivar" ore dust by the branched filamentous algal ihalli o f Plumaria elegans and Cladophora rupestris Fresh-weights of thalli were determined after gently compressing the plants between layers of filter paper 177
Marine Pollution Bulletin
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Fig. 3 (A) Measurements of radiant energy not transmitted through dark-coioured Porphyra thalli after shaking with ore-dust suepensions for 6 h. (B) Measurements of radiant energy not transmitted through ore-dust treated Porphyra thalli after shaking for 3 h in filtered seawater. P = Porphyra thallus alone --B,L,M.T--Porphyra thalli with Bolivar, Lac Jeanine, Mang Ore and Tazadit dust respectively. GD = glass vessel.
C
TABLE 1 Weights of iron-ore dust retained by thalli after shaking for 6 h. (0.5 g ore dust 'Bolivar' in 100 ml seawater).
Plumaria elegens A B
Cladophora rupestris A B
Fresh weights (g)
2.16
2.15
2.29
2.28
Ore dust retained by plants (g)
0.415
0.425
0.475
0.480
% of original ore dust sample retained
83
85
95
96
Weight of ore dust (g) retained per 1 g fresh weight of plant
0.192
0.198
0.208
0.2 l0
until no further absorption o f water was obtained. The plants were then shaken for 6 h in a suspension of 0.5 g 'Bolivar' ore dust in 100 ml filtered seawater, and the quantities o f retained ore dust then measured (Table 1). The Plumaria plants used retained 83 and 85°70 ore dust and Cladophora plants 95 and 96°70. When compared in terms of equivalent fresh weights (e.g. per 1 g fresh weight of each plant) then the compact plumose branched form of Plumaria shows dust-retaining properties similar to that of the densely tufted Cladophora. Examination 178
I Fig. 4 (A) Plumaria--terminal branches with Bolivar dust. (B) Cladophora--filaments with Bolivar dust coating. (C) Pelvetia --Bolivar dust covering of thalli after 6 h shaking in filtered seawater. Scale line by A = 200 ~um. Scale line by C = 2 cm.
of the dust-coated filaments showed that the particles were densely packed between the plumose branches in the apical region of the Plumaria thallus (Fig. 4A). With Cladophora the dust particles form a dense coating on the older cells of the filaments compared with the younger cells in the apical regions (Fig. 4B). When the dust-laden thalli were shaken in filtered seawater over a 15 h period and the quantities o f dust released measured at intervals o f 3, 6, 9 and 15 h, it was evident that the Cladophora tufts were the more retentive, holding on to
Volume9/Number 7/July t978 0.5
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Fig. 6 (A) Ore-dust retention by Pelvetiaplants of similar fresh weights after shaking
in filtered seawater. (B) Ore-dust retention by Polysiphonia plants after shaking in filtered seawater. The !ower curves are for fresh weights of 4.54-4.57 g. The upper curve is for a plant of fresh weight 7.5 g.
58°70 of the original ore dust 'load' after 15 h compared with the 3807o retained by Plumaria plants (Fig. 5 A, B). Greater quantities of ore-dust were shed by Plumaria plants in the first 3-6 h of shaking, whereas with Cladophora there was steadier rate of loss of dust particles over the period of experiment.
Retention o f "Bolivar" ore dust by Polysiphonia lanosa and Polvetia canaliculata Whilst Polysiphonia lanosa is characterized by an extensively branched thallus form, the branches are of wider angles than those of Plumaria and Cladophora, and the thallus is of a more rigid overall construction. In the experiments on dust retention it was evident that the Polysiphonia thallus retained smaller quantities of dust per g fresh weight of plant than either Plumaria or Cladophora (Table 2), and in fact showed a similar dust-
retaining capacity to that of the fucoid alga Pelvetia canaliculata. O f the two plants, however, Pelevetia retained 34°7o of its dust load after shaking, whilst similar fresh weights of Polysiphonia retained 2 6 % . of the original dust picked up (Fig. 6 A, B). With Pelvetia plants the dust cover was more extensive and remained more firmly attached in the basal regions of the thalli (Fig. 4C). The apical regions with their mucilage cover were noticeably less affected. Apical branches functioning as young receptacles with numerous developing conceptacles were also less coated than the lower parts of the branches and the holdfast regions. It was also noticed that Pelvetia plants which were air-dried in the laboratory for 2-3 days were less retentive of ore dust than wet thalli. Reimmersion of the dried plants was accompanied by release o f a soluble yellow substance, and this loss of extracellular material may account for the subsequent reduced dust load. 179
Marine Pollution Bulletin TABLE 2 Weights of iron-ore dust retained by thalli after shaking for 6 h. (0.5 g ore dust 'Boli',ar' in 1190ml sea~ater).
Polysiphonia lanosa A B
Pelvetia canaliculata A B
Fresh weight (g)
4.545
4.575
4.50
4.65
Ore dust retained by plants (g)
0.265
0.245
0.220
0.225
53
49
44
45
0.060
0.054
0.049
0.048
% of original ore dust sample retained Weight of ore dust (g) retained per I g fresh weight of plant
TABLE 3 Accumulation of 'Bolivar' ore by similar fresh weights of Polysiphonia lanosa when shaken for 6 h in varying quantities of dust. Fresh wt o f plant (g)
Wt of ore dust (g) per 100 ml seawater
4.185 4.170 4.185 4.170 4.180
0.050 0.100 0.250 0.500 0.750
W t of ore dust % or origiual (g) taken up ore dust quantity by plant taken up by plant 0.005 0.015 0.115 0.245 0.225
10 15 46 49 30
Discussion As already stated, there appears to be no quantitative data on suspended particulate iron compounds in the sea and their uptake by marine algae. 'Red muds', for example, along with coal dust, china clay and fly ash from power stations, may bring about changes in the character of the sea bottom which may not be entirely harmful, and may in fact encourage the greater production of a benthic fauna (Portmann, 1970; Howell & Shelton, 1970; Cole, 1972). The effects of the silt load in the water on light penetration will clearly be an environmental factor of significance with benthic algae, however. The coating of algae with particulate matter will also inhibit uptake of radiant energy as well as reducing uptake of nutrients and gaseous exchange. A smothering effect can also lead to overloading of the plants, making them more susceptible to physical damage by wave action. Juvenile plants and sporeling stages will also be adversely affected, and longer term effects may include changes in species diversity. In turn these effects on the plant populations could be detrimental to the associated fauna. From the preliminary survey reported in the present work it is evident that marine algae of different thallus constructions are all capable of accumulating iron ore dusts of the particle size ranges utilised in the present experiments, and that some of the dust remains attached after the plants have been vigorously shaken for 12-15 h. The means by which the dust particles become bound to algal thalli are in need of investigation. Whilst the excessive accumulation of an iron ore dust load may well be detrimental, it would be of interest to know whether small quantities of the bound iron compounds 180
may be utilized as a nutrient source by the plants, since such a use of attached colloidal iron has been described for some diatoms (Harvey, 1937). The quantities of ore dust used in the present work were an entirely arbitrary choice. There is no information on the spillage quantities involved because the experimental work is in advance of the industrial operations. The quantities used in the present experiment (0.5 g in 100 ml filtered seawater) represents a particle load in the sea of 5 kg m -3. Clearly this particle 'load' factor will be of crucial importance. The effects of varied ore dust quantities in suspension on the accumulation by Polysiphonia lanosa is shown in Table 3. The results indicate that with small quantities of dust well dispersed in the sea there is as expected an appreciably lower accumulation by the plant. At quantities of 0.75 g/100 ml (7.5 kg m-3), the Polysiphonia plants seem to accumulate less ore dust than with 0.5 g/100 ml, possibly due to the denser silt load in the water dislodging material caught up in the branches. The methods described in the present work offer an effective means of assessing the loading of algal thalli when in contact with suspended iron ore dust. There are algae with other forms of thallus construction which need to be examined however. Thus, the gelatinous thalli of Nemalion and Helminthocladia and the much branched and tufted Callithamnion species are examples in the red algae. The spongy siphonaceous thalli of the Codium species in the green algae, and the mucilage covered macroscopic thalli of the Fucus species and Laminaria species in the brown algae are other examples worthy of examination. If the quantities taken up by plants with the dust 'loading' of the sea can be established for a suitable representative number of common marine algae, one aspect of the potential environmental risk can be assessed. It then needs to be established whether such accumulations of dust by algae are entirely harmful in terms of effects on metabolic processes. I thank the British Steel Corporation Scottish Group, Ravenscraig and Gartcosh Works for their support of the overall research programme, and particularly Mr J. Little, Manager, Chemical and Environmental Services, for his co-operation and supply of the ore dust samples. Bellamy, D. J. & Whittick, A. (1968). Problems in the assessment of the effects of pollution on inshore marine ecosystems dominated by attached macrophytes. Field Studies, 2, 49-54. Bellamy, D. J., Whittick, A. & Jones, D. J. (1969). How to live with pollution. Spectrum, 62, 8-I 1. Bellamy, D. J., J o h n , D. M., Jones, D. J., Starke, A. & Whittick, A. (1972). The place of ecological monitoring in the study of pollution of the marine environment. In Marine Pollution and Sea Life (M. Ruivo, Ed.) Fishing News (Books), London. Burrows, E. M. & Pybus, C. (1971 ). Laminaria saccharina and marine pollution in north-east England. Mar. Pollut. BulL, 2, 53-56. Cole, H. A. (1972). North sea pollution. In Marine Pollution and Sea Life (M. Ruivo, Ed.) pp. 3-10. Fishing News (Books), London. Harvey, H. W. (1973). The supply of iron to diatoms. J. mar. biol. Ass. U.K., 22,205-220. Howell, B. R. & Shelton, R. G. J. (1970). The effect of china clay on the bottom fauna of St. Austell and Mevagissey Bays. J. mar. biol. Ass. U.K., 50,595-607. Johnston, R. (1976). Mechanisms and problems of marine pollution in relation to commercial fisheries. In Marine Pollution (R. Johnston, Ed.) pp. 3-156. Academic Press, London. Moss, B., Mercer, S. & Sheader, A. (1973). Factors affecting the distribution of Himanthalia elongata (L.) S.F. Gray on the northeast coast of Eogland. Estuarine Coastal Mar. Sci., 1,233-243. P o r t m a n n , J. E. (1970). The effects of china clay on the sediments of St. Austell and Mevagissey Bays. J. mar. biol. Ass. U.K., 50, 577-592.
7 ' J u l y 1978
maintained. Otherwise there would be several hundred thousand more great whales in the world than there are now. This is why I personally support the ten-year whaling moratorium, agreed to almost unanimously at the Stockholm U.N. Conference on the Environment, and advocated by both the International Union for Conservation of Nature and by the World Wildlife Fund, as well as by m a n y other conservation bodies, such as the Fauna Preservation Society and the New York Zoological Society. This moratorium has never been accepted by the International Whaling Commission, whose national representatives regularly vote down the pledge given by their countries at Stockholm in 1972. The extermination tradition of hunter-gatherer man is too strong. What has happened to the great whales happened earlier to the fur seals, all stocks of which were at one time or another brought below harvestable level by the operation of the Colin Clark effect. The sub-antarctic Kerguelen fur seal, curiously named Arctocephalus tropical&, has the melancholy distinction of having been 'exterminated' three times over. The first occasion was in the 1820s, when a million and a quarter skins were being harvested annually. Fifty years later the colonies had revived enough for sealing to start again but, after an average of 45 000 skins had been taken for some sixteen years, the southern race was believed to be extinct. There was a minor resurgence of sealing when 800 skins of the northern race were taken from Prince Edward Island in the southern Indian Ocean in 1921. Not until 1929 was the southern race rediscovered, on Bouvet Island, and since then it has recovered more widely, and for instance there were 33 000 fur seals on Bird Island off South Georgia by 1962. All are currently protected, but there is some argument as to whether sealing can safely start again. If it does, the only safe prediction that can be made is that excessive quotas will be fixed, and the southern fur seal will sooner rather than later become too scarce to harvest once more. The southern
elephant seal Mirounga leonina, to which the sealers transferred when they had knocked out the fur seal, has had a similar chequered history. The much publicized harp and hood seal fishery off Newfoundland is still in a fairly early stage of decline, but trends already established show that sooner or later the Canadian Government will be forced to eat its words, and admit that it has allowed too large quotas to be fixed and operated. The most hopeful story in the long and shameful history of the exploitation of marine m a m m a l s - a n d the same thing is happening with marine turtles - is that of the Pribilof fur seal Callorhinus ursinus. In 1786, eighteen years after the demise of Steller's sea cow, the Russian navigator Gerassim Pribilof discovered the breeding ground of this seal on the two islands that still bear his name. There were then perhaps two and a half million seals in the rookeries. Within twenty years the sealers of Russia, Canada and the United States had brought them to the verge of extinction. Throughout the 19th century the Russians and, after the islands were sold to the U.S. in 1867, the Americans operated a stopgo system of moratoria to allow the stocks to build up again. In the 1880s however, the British and Canadians started pelagic sealing on a large scale, and this brought the final crisis. By the time the riparian states were persuaded to agree to prohibit pelagic sealing in the North Pacific in 1911, only 200000, less than a tenth of the original stocks, were left. Under planned United States management stocks have built up again to well over a million and a half, and there is now a carefully controlled harvest, which is an important addition to the Alaskan economy, with Japanese and Canadian sealers each being allotted fifteen per cent of the proceeds. So it can be done, but only by a single strong and conservation-minded government. If it is left to the hunting instincts of hunter-gatherer man, as personified in the modern nation state engaging in a free-for-all, any animal stock of any economic value, terrestrial or marine, will be exterminated.
)d~trine Pollution Bulletin. Voi. 9. pp. 175-180 C~)25-326XTS/071~I -OI75 $02.000
Pergamon Press Ltd. 1978. Printed in Great Britain
Marine Algae as Collectors of Iron Ore Dust A. D. BONEY
Department of Botany, University of Glasgow, Glasgow G12 8QQ, Scotland Marine algae from intertidal habitats, when shaken in iron ore dust suspensions in seawater, take up appreciable quantifies of the dust load. The quantities taken up vary with the modes of thallus construction. Considerable quantities of ore dust are retained by the plants after
shaking for periods of up to 15h in dust free seawater. Marine algae can be used as a monitoring system for ore dust loading of seawater due to accidental spiilages in the vicinity of ore unloading terminals.
175
Marine Pollution Bulletin
Current industrial developments in the Hunterston region of the north Ayrshire coast in the Firth of Clyde, Scotland, include the construction of an iron ore unloading terminal to be linked with an inland processing plant. This constitutes the first stage of a major industrial development in the area. The deep waters of the upper Firth have facilitated this development, and will allow large ore-carrying ships to anchor close inshore for unloading. Construction of an offshore jetty and of a covered conveyor belt transportation system for carrying the crushed ore to storage areas has been in progress since 1975 and is due to become operational early in 1978. A base-line study of the benthic marine algae in the Firth, with due regard to the area designated for industrialization, was commenced in 1972 with grant support from the Natural Environmental Research Council up to 1975, and with continuing grant support from British Steel since then. As part of this work on marine algae, attention has been focused on suspended iron ore dust as an environmental factor in the sea. Whilst it is clearly not the intention of British Steel to offload into the sea a valuable commodity transported at considerable cost from foreign ore deposits, the possibility of accidental spillage, or of windborne deposition in the sea must not be overlooked. The research programme instituted, of which the present work forms part, may be regarded as a type of 'early warning' system, in which answers to environmental questions are being sought before the industrial complexes become operational. There is little available information on the effects of suspended inorganic particulate matter on marine algae. Five categories of inorganic particulate matter have been described (Johnston, 1976): (I) Dredged 'spoil', (2) 'acid iron waste', (3) 'red mud' (mainly alkaline), (4) coal wastes and (5) china clay residues. Of these, dredged 'spoil' is the large-scale transportation and deposition of dredged sea-bed material, and will influence benthic organisms both by being removed and later deposited elsewhere. China clay residues tend to be mainly deposited in rivers and estuaries although some inshore deposition does take place. Each of the remaining three categories involve forms of particulate iron compounds. Acid iron waste consists of sulphates and chlorides of iron dissolved in strong solutions of the corresponding mineral acids, and contains the iron residues remaining after the separation of titanium from the minerals illmenite and rutile. Red mud is the alkaline iron waste after the manufacture of alumina from bauxite. Coal wastes are similarly rich in particulate iron, either as aqueous (acid) wastes containing both iron and manganese salts, or as iron-rich solid waste 'leachates' from coal refuse dumped offshore, or in coastal 'bings' unguarded from the sea. All these residues form hydrated iron oxide following their release into the sea, and as such will constitute part of the silt load. Suspended particulate matter, if present in sufficient quantity, will cut down light penetration and form surface coatings on seaweeds, with resulting decreases in growth rates and possible changes in species diversity. Animals using seaweeds for attachment of eggs will be affected, as well as those which use the plants as food and as substrata for settlement. The 176
plants will also be affected by the smothering of sporelings and juvenile stages, and possibly from the blockage of reproductive 'pores' in fertile plants. Effects of diminished light intensity due to silt load in reducing Laminaria photosynthesis have been reported (Bellamy & Whittick, 1968; Bellamy et al., 1969, 1972), and effects on growth form (Burrows & Pybus, 1971). Silting of rock faces prevents spore settlement in Laminaria (Burrows & Pybus, 1971), and Himanthalia (Moss et aL, 1973). There is a lack of quantitative data on algae as dust collectors. The present work is an examination of the role of marine algae of different forms of thallus construction as collectors of particulate iron compounds, particularly the oxides of iron present in iron ore dust.
Materials and Methods Four samples of iron ore dust were supplied by British Steel: 'Bolivar', 'Lac Jeanine', 'Mang Ore' and 'Tazadit'. Mang Ore is a black powder; the remaining three are red. Particulate size distributions were determined using a Coulter Electronic Counter Model TA 1 I. Ore dust suspensions in filtered seawater were shaken with algal thalli in conical flasks on a laboratory orbital shaker at constant speed. Retention of ore dust by algal thalli was measured using round bottomed flasks containing similar volumes of seawater, and using a laboratory flask shaker set at a speed which was constant for all of the experiments. The transmission of radiant energy through membranaceous thalli after coating with ore dust was measured using an Instrumentation Specialities Company Model SR Spectroradiometer with an iodinequartz light source in a dark-room. Measurements were made with the moist algal thalli spread on the base of a petri-dish at a fixed distance from the light source, and with the probe of the spectroradiometer fixed against the underside of the dish. The quantities of ore dust remaining after shaking the suspensions with algae, or after the dust-laden algae had been shaken in seawater, were determined gravimetrically in pre-weighed and dried Gooch crucibles lined with magnesium carbonate. Each crucible plus ore dust was dried to constant weight over several days at 60°C in an oven, and stored for 6h in a desiccator until weighed on each occasion. Five species of marine algae were used in the experiments: Rhodophyceae Porphyra umbilicalis (L.) J.Ag. Plumaria elegans (Bonnem.) Schm. Polysiphonia lanosa (L.) Tandy Chlorophyceae Cladophora rupestr& (L.) K0tz.
(membranaceous) (plumose branching) (much branched, dichotomous) (abundant branching, plant densely tufted)
Phaeophyceae Pelvetia canaliculata (L.) Dcne et Thur. (a 'fucoid' alga)
All are of common occurrence on the shores of the Isle of Cumbrae in the Firth of Clyde. Plants were used as soon as possible after collection. Storage for 1-2 days in polythene bags in a refrigerator was sometimes necessary, and plants stored in this way were equilibrated in filtered seawater at room temperature (ca 20°C) for 12 h prior to an experiment.
Volume 91Number 7 / J u l y
1978
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Fig. 1 Particle diameter size groups of the ore dust samples. 'Tazadit' measured immediately after shaking with seawater, the remaining ore dust samples after overnight suspension in seawater.
Results Size ranges of ore dust particles in sea water If measured quantities of ore dust are mixed with similar volumes of distilled water and seawater, and the rates of sedimentation compared, it will be observed that the dust in seawater settles out more rapidly. This aggregation of the fine particles is shown in Fig. 1, in which the particle size distributions are compared. The 'Tazadit' sample was measured within 60 min. of mixing with the seawater, and the remaining three measured after several hours had elapsed. After thorough mixing with seawater, the particles were mainly in the size (diameter) range of 8-25 Mm.
Transmission of radiant energy through the ore-coated membranaceous thalli ofPorphyra umbilicalis In these experiments similar fresh weights of Porphyra umbilicalis were shaken with 0.5 g of ore dust in 100 ml filtered seawater. Porphyra thalli vary in colour on the shore, and comparisons were first made of energy transmission by 'pale brown' and 'dark' coloured plants (Fig. 2 A, B). Energy transmission through the petridish (GD), compared with the dry and wet thalli of the pale brown coloured Porphyra showed that greater quantities of radiant energy are reflected and retained by the dried than by the wet thalli. This can be linked
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Retention of "Bolivar" ore dust by the branched filamentous algal ihalli o f Plumaria elegans and Cladophora rupestris Fresh-weights of thalli were determined after gently compressing the plants between layers of filter paper 177
Marine Pollution Bulletin
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Fig. 3 (A) Measurements of radiant energy not transmitted through dark-coioured Porphyra thalli after shaking with ore-dust suepensions for 6 h. (B) Measurements of radiant energy not transmitted through ore-dust treated Porphyra thalli after shaking for 3 h in filtered seawater. P = Porphyra thallus alone --B,L,M.T--Porphyra thalli with Bolivar, Lac Jeanine, Mang Ore and Tazadit dust respectively. GD = glass vessel.
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TABLE 1 Weights of iron-ore dust retained by thalli after shaking for 6 h. (0.5 g ore dust 'Bolivar' in 100 ml seawater).
Plumaria elegens A B
Cladophora rupestris A B
Fresh weights (g)
2.16
2.15
2.29
2.28
Ore dust retained by plants (g)
0.415
0.425
0.475
0.480
% of original ore dust sample retained
83
85
95
96
Weight of ore dust (g) retained per 1 g fresh weight of plant
0.192
0.198
0.208
0.2 l0
until no further absorption o f water was obtained. The plants were then shaken for 6 h in a suspension of 0.5 g 'Bolivar' ore dust in 100 ml filtered seawater, and the quantities o f retained ore dust then measured (Table 1). The Plumaria plants used retained 83 and 85°70 ore dust and Cladophora plants 95 and 96°70. When compared in terms of equivalent fresh weights (e.g. per 1 g fresh weight of each plant) then the compact plumose branched form of Plumaria shows dust-retaining properties similar to that of the densely tufted Cladophora. Examination 178
I Fig. 4 (A) Plumaria--terminal branches with Bolivar dust. (B) Cladophora--filaments with Bolivar dust coating. (C) Pelvetia --Bolivar dust covering of thalli after 6 h shaking in filtered seawater. Scale line by A = 200 ~um. Scale line by C = 2 cm.
of the dust-coated filaments showed that the particles were densely packed between the plumose branches in the apical region of the Plumaria thallus (Fig. 4A). With Cladophora the dust particles form a dense coating on the older cells of the filaments compared with the younger cells in the apical regions (Fig. 4B). When the dust-laden thalli were shaken in filtered seawater over a 15 h period and the quantities o f dust released measured at intervals o f 3, 6, 9 and 15 h, it was evident that the Cladophora tufts were the more retentive, holding on to
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in filtered seawater. (B) Ore-dust retention by Polysiphonia plants after shaking in filtered seawater. The !ower curves are for fresh weights of 4.54-4.57 g. The upper curve is for a plant of fresh weight 7.5 g.
58°70 of the original ore dust 'load' after 15 h compared with the 3807o retained by Plumaria plants (Fig. 5 A, B). Greater quantities of ore-dust were shed by Plumaria plants in the first 3-6 h of shaking, whereas with Cladophora there was steadier rate of loss of dust particles over the period of experiment.
Retention o f "Bolivar" ore dust by Polysiphonia lanosa and Polvetia canaliculata Whilst Polysiphonia lanosa is characterized by an extensively branched thallus form, the branches are of wider angles than those of Plumaria and Cladophora, and the thallus is of a more rigid overall construction. In the experiments on dust retention it was evident that the Polysiphonia thallus retained smaller quantities of dust per g fresh weight of plant than either Plumaria or Cladophora (Table 2), and in fact showed a similar dust-
retaining capacity to that of the fucoid alga Pelvetia canaliculata. O f the two plants, however, Pelevetia retained 34°7o of its dust load after shaking, whilst similar fresh weights of Polysiphonia retained 2 6 % . of the original dust picked up (Fig. 6 A, B). With Pelvetia plants the dust cover was more extensive and remained more firmly attached in the basal regions of the thalli (Fig. 4C). The apical regions with their mucilage cover were noticeably less affected. Apical branches functioning as young receptacles with numerous developing conceptacles were also less coated than the lower parts of the branches and the holdfast regions. It was also noticed that Pelvetia plants which were air-dried in the laboratory for 2-3 days were less retentive of ore dust than wet thalli. Reimmersion of the dried plants was accompanied by release o f a soluble yellow substance, and this loss of extracellular material may account for the subsequent reduced dust load. 179
Marine Pollution Bulletin TABLE 2 Weights of iron-ore dust retained by thalli after shaking for 6 h. (0.5 g ore dust 'Boli',ar' in 1190ml sea~ater).
Polysiphonia lanosa A B
Pelvetia canaliculata A B
Fresh weight (g)
4.545
4.575
4.50
4.65
Ore dust retained by plants (g)
0.265
0.245
0.220
0.225
53
49
44
45
0.060
0.054
0.049
0.048
% of original ore dust sample retained Weight of ore dust (g) retained per I g fresh weight of plant
TABLE 3 Accumulation of 'Bolivar' ore by similar fresh weights of Polysiphonia lanosa when shaken for 6 h in varying quantities of dust. Fresh wt o f plant (g)
Wt of ore dust (g) per 100 ml seawater
4.185 4.170 4.185 4.170 4.180
0.050 0.100 0.250 0.500 0.750
W t of ore dust % or origiual (g) taken up ore dust quantity by plant taken up by plant 0.005 0.015 0.115 0.245 0.225
10 15 46 49 30
Discussion As already stated, there appears to be no quantitative data on suspended particulate iron compounds in the sea and their uptake by marine algae. 'Red muds', for example, along with coal dust, china clay and fly ash from power stations, may bring about changes in the character of the sea bottom which may not be entirely harmful, and may in fact encourage the greater production of a benthic fauna (Portmann, 1970; Howell & Shelton, 1970; Cole, 1972). The effects of the silt load in the water on light penetration will clearly be an environmental factor of significance with benthic algae, however. The coating of algae with particulate matter will also inhibit uptake of radiant energy as well as reducing uptake of nutrients and gaseous exchange. A smothering effect can also lead to overloading of the plants, making them more susceptible to physical damage by wave action. Juvenile plants and sporeling stages will also be adversely affected, and longer term effects may include changes in species diversity. In turn these effects on the plant populations could be detrimental to the associated fauna. From the preliminary survey reported in the present work it is evident that marine algae of different thallus constructions are all capable of accumulating iron ore dusts of the particle size ranges utilised in the present experiments, and that some of the dust remains attached after the plants have been vigorously shaken for 12-15 h. The means by which the dust particles become bound to algal thalli are in need of investigation. Whilst the excessive accumulation of an iron ore dust load may well be detrimental, it would be of interest to know whether small quantities of the bound iron compounds 180
may be utilized as a nutrient source by the plants, since such a use of attached colloidal iron has been described for some diatoms (Harvey, 1937). The quantities of ore dust used in the present work were an entirely arbitrary choice. There is no information on the spillage quantities involved because the experimental work is in advance of the industrial operations. The quantities used in the present experiment (0.5 g in 100 ml filtered seawater) represents a particle load in the sea of 5 kg m -3. Clearly this particle 'load' factor will be of crucial importance. The effects of varied ore dust quantities in suspension on the accumulation by Polysiphonia lanosa is shown in Table 3. The results indicate that with small quantities of dust well dispersed in the sea there is as expected an appreciably lower accumulation by the plant. At quantities of 0.75 g/100 ml (7.5 kg m-3), the Polysiphonia plants seem to accumulate less ore dust than with 0.5 g/100 ml, possibly due to the denser silt load in the water dislodging material caught up in the branches. The methods described in the present work offer an effective means of assessing the loading of algal thalli when in contact with suspended iron ore dust. There are algae with other forms of thallus construction which need to be examined however. Thus, the gelatinous thalli of Nemalion and Helminthocladia and the much branched and tufted Callithamnion species are examples in the red algae. The spongy siphonaceous thalli of the Codium species in the green algae, and the mucilage covered macroscopic thalli of the Fucus species and Laminaria species in the brown algae are other examples worthy of examination. If the quantities taken up by plants with the dust 'loading' of the sea can be established for a suitable representative number of common marine algae, one aspect of the potential environmental risk can be assessed. It then needs to be established whether such accumulations of dust by algae are entirely harmful in terms of effects on metabolic processes. I thank the British Steel Corporation Scottish Group, Ravenscraig and Gartcosh Works for their support of the overall research programme, and particularly Mr J. Little, Manager, Chemical and Environmental Services, for his co-operation and supply of the ore dust samples. Bellamy, D. J. & Whittick, A. (1968). Problems in the assessment of the effects of pollution on inshore marine ecosystems dominated by attached macrophytes. Field Studies, 2, 49-54. Bellamy, D. J., Whittick, A. & Jones, D. J. (1969). How to live with pollution. Spectrum, 62, 8-I 1. Bellamy, D. J., J o h n , D. M., Jones, D. J., Starke, A. & Whittick, A. (1972). The place of ecological monitoring in the study of pollution of the marine environment. In Marine Pollution and Sea Life (M. Ruivo, Ed.) Fishing News (Books), London. Burrows, E. M. & Pybus, C. (1971 ). Laminaria saccharina and marine pollution in north-east England. Mar. Pollut. BulL, 2, 53-56. Cole, H. A. (1972). North sea pollution. In Marine Pollution and Sea Life (M. Ruivo, Ed.) pp. 3-10. Fishing News (Books), London. Harvey, H. W. (1973). The supply of iron to diatoms. J. mar. biol. Ass. U.K., 22,205-220. Howell, B. R. & Shelton, R. G. J. (1970). The effect of china clay on the bottom fauna of St. Austell and Mevagissey Bays. J. mar. biol. Ass. U.K., 50,595-607. Johnston, R. (1976). Mechanisms and problems of marine pollution in relation to commercial fisheries. In Marine Pollution (R. Johnston, Ed.) pp. 3-156. Academic Press, London. Moss, B., Mercer, S. & Sheader, A. (1973). Factors affecting the distribution of Himanthalia elongata (L.) S.F. Gray on the northeast coast of Eogland. Estuarine Coastal Mar. Sci., 1,233-243. P o r t m a n n , J. E. (1970). The effects of china clay on the sediments of St. Austell and Mevagissey Bays. J. mar. biol. Ass. U.K., 50, 577-592.