The Science of the Total Environment, 6 (1976) 55-63 © Elsevier Scientific Publishing Company, Amsterdam - - Printed in Belgium
MUSSELS (Mytilus sp) AS AN INDICATOR OF LEAD POLLUTION
TSAIHWA J. CHOW, H. GEORGE SNYDER and CARRIE B, SNYDER Scripps Institution of Oceanography, La Jolla, CaliJ~ 92093 (U.S.A.) (Received October 29th, 1975)
ABSTRACT
The lead contents of two species of mussels (Mytilus californianus and M. edulis) collected along the Pacific coast from Piedras Blancas, California to Punta Banda, Baja California were determined by isotope dilution method. The whole soft parts of the mussels, on a dry weight basis, contained from 0.27 to 42 ppm of lead, which can be related to their local habitats. The gill tissues of the mussels showed the highest lead concentration.
INTRODUCTION
Adverse effects of toxic substances on the environmental quality have become a concern in recent years. Lead is one of the identifiable heavy metal pollutants (Chow, 1973), and its rate of introduction into the ocean through man's activity surpasses that by river runoffs (IDOE, 1971). Thus, the lead content of coastal surface sea water has increased considerably in relation to that in the deep ocean water (Chow and Patterson, 1966; Patterson, 1974); this is especially evident along the industrialized coastal zones. Trace metal concentrations of sea water are one of the factors which influence those concentrations in marine organisms. Vinogradov (1953) and Goldberg (1965) reviewed earlier literature on chemical composition of marine organisms. More recently, contents of heavy metals, including lead, were determined in molluscs from various geographic regions (Brooks and Rumsby, 1965; Pringle, et al., 1968; Graham, 1971; Segar, et al., 1971; Nickless, et al., 1972; Bryan, 1973; Schulz-Baldes, 1972, 1973, 1974). SAMPLING AND ANALYSIS
Mytilus sp. w a s c h o s e n as t h e r e p r e s e n t a t i v e o r g a n i s m for this s t u d y bec a u s e o f its w o r l d - w i d e d i s t r i b u t i o n a n d g e n e r a l availability in t h e intertidal zone.
55
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Fig. 1. Collection sites of Mytilus sp. along the California and Baja California coasts, and description of their habitats. 1 = Piedras Blancas. South of Coast Guard Lighthouse exposed coast, rocky low intertidal reef. 2 = Cayucos. 6 km North of Village---exposed coast, rocky low intertidal reef. 3 = Cayucos. 0:6 km North of Village--semi-protected coast, sandy beach with elevated rocks in sand. 4 = Cayucos. Pier about 3 km South of Village---open coast, piling community. S = Gaviota. California State Beach--exposed coast, rock ledges and boulders. 6 = Goleta Point. University of California at Santa Barbara----exposed coast, rocky. 7 = Santa Barbara. Harbor Marina--protected inlet. 8 = Rincon Point. Sere/protected coast, rocky with tidal flats. 9 = Long Beach. Harbor Marina--protected inlet. 10 = Anaheim Bay. Gasoline Station Fueling Dock--mud flats and protected slough, piling community. 11 = San Clemente. Pier--open coast, piling community. 12 = Oceans/de. Harbor Marina--protected inlet. 13 = La Jolla. Scripps Institution of Oceanography Pier---open coast, piling community. 14 = San Diego. Pacific Beach Pier--open coast, piling community. 15 = San Diego. Quivera Basin-protected inlet. 16 = San Diego. Shelter Island-lsemiprotected harbor channel. 17 = La Salina, Baja California. Open coast, sandy beach and rocky tide pools. 18 = Ensenada, Baja California. Harbor-protected inlet. 19 = Punta Banda, Baja California. Open coast, rock ledges and tide pools.
56
Specimens were collected along the Pacific coast in 1972 and 1973 from Piedras Biancas (35°40'N, 121°17'W) near San Simeon, Calif., to Punta Banda (31°45'N, 116°45'W) near Ensenada in Baja California, Mexico. This coastal zone depicts varying degrees of industrialization ranging from relatively undisturbed to heavily populated regions. The geographic locations as well as the description of their habitats are given in Fig. 1. In the laboratory the specimens were stored in a freezer at a temperature of -15°C. Frozen specimens were cleaned and allowed to defrost. Then, they were weighed, measured, and dissected. From additional specimens of selected localities, the soft parts were dissected for various anatomical organs. Due to the small size of some organs, several specimens from the same site were pooled in order to provide sufficient material for analysis. The wet tissues were dried at 110°C to constant weight and then ashed at 500°C to destroy the organic matter. Known weight of stable m6Pb tracer was equilibrated with the lead in the ash during digestion and oxidation; the lead isotope mixtures were isolated by ion-exchange and dithizone extraction, and were analyzed in a mass spectrometer. Separate samples without adding the stable lead tracer were used for the isotope ratios determination. The reagent blank was 0.1 gg of lead per sample of 10g size. The following 90 96 confidence interval limits were assigned: ~ P b / ~ P b , 0.3 %; ~Pb/mTpb, 0.1%; and ~ P b / ~ P b , 0.2 96. RESULTS AND DISCUSSION Previous investigators reporting trace metal concentrations of marine organisms have used either a wet or a dry weight basis. Since this practice often causes some difficulty when attempting to compare results from different laboratories, we report our results, which were amended to account for the reagent blank, on both a wet and a dry weight basis (Table 1). A least square fit is derived by plotting the average lead contents of wet versus dry weight basis of the soft parts of mussels representing respective sampling locations. The Anaheim Bay saml)le was excluded in the calculation because it contained an abnormally high lead concentration. A linear relationship between wet and dry weight basis of lead contents is obtained. Pb (wet weight)=0.139xPb (dry weight)+0.03 Individual samples, which mostly were composed of whole soft parts of one or two Mytilus, showed variability in lead contents. The mean deviations from the concentration average of respective locations ranged from 8 to 48 %. These variations may be attributed to the diversity in size and age of the specimens, as well as to their position in the intertidal zone. Specimens located at the high water habitat would be exposed to the most lead pollutants (Graham, 1971). Schulz-Baldes (1973) found similar lead concentration variations among M. edulis collected near Bremerhaven, G.F.R. He reported that individual samples of 57
TABLE 1 LEAD CONTENTS IN WHOLE SOFT PARTS OF Mvtilus sp. Pb (p.p.m.) Location Piedras Blancas South of lighthouse
Date collected
Species
Length (mnO
Wet wt.
Dry wt.
10/21/72 M. cal(lornianus
50, 80 58 54, 72 49
0.094 0.150 0.174 0.179
0.556 0.824 0.958 1.057
Cayucos, 6 km north of village 10/22/72 M. cal~/ornianus
39, 43 45, 47 42, 50 37, 47
0.135 0.147 0.153 0.194
0.683 0.738 0.815 0.993
Cayucos, 0.6 km nonh of village 09/14/73
M. caliJbrnianus
78 80 76
0.104 0.125 0.170
0.386 0.507 0.688
Cayucos, 3 km south of village Pier
09/14/73
M. cal(lornianus
103 74 89 107
0.065 0.082 0.086 0.094
0.265 0.325 0.339 0.342
Gaviota State Beach
10/23/72 M. caliJornianus
95 86 84
0.118 0.159 0.170
0.568 0.808 0.859
Goleta Point
10/24/72 M. caliJornianus~
85 87 80 77
0.131 0.199 0.235 0.252
0.664 1.054 1.150 1.355
Santa Barbara Harbor Marina
10/24/72 M. edulis
77 95 77
0.586 0.630 1.086
2.471 3.500 4.395
Santa Barbara Harbor Marina
09/13/73
77 78 80
0.651 1.746 2.062
4.752 11.54 18.87
Rincon Point
10/25/72 M. caliJornianus
87 100 97 95
0.124 0.202 0.276 0.426
0.596 0.968 1.312 2.341
Long Beach Harbor Marina
04/11/73
M. edulis
78 68, 70 69 85 79
1.422 1 696 2.311 3.051 4.012
8.11 9.48 19.81 24.92 24.46
Anaheim Bay Gasoline station fueling dock
04/11/73
M. edulis
78 73 57, 61 70 68, 73
3.222 3.360 3.669 4.083 4.162
24.62 30.53 31.63 41.97 36.32
San Clemente Pier
04/13 / 73 M. cal(/ornianus (20 juveniles)
20-25
0.520
58
M. edulis
3.393
TABLE 1 (Continued) Pb (p.p.m.) Location
Date collected
Species
Length (mnO
I+'et wt.
Dry wt.
60, 62 55, 57, 65 50, 70, 75 70 72
0.338 0.498 0.619 0.700 0.898
4.878 5.150 5.669 6.917 9.963
Oceanside Harbor Marina
04/11/73 M. edulis
San Diego La Jolla SIO Pier
04/12/73 M. cal~ornmnus
92 100 110 104 97
0.817 0.884 0.922 0.952 1.400
6.276 6.542 7.617 8.334 11.03
San Diego Pacific Beach Pier
05/24/73 M. cal~brnianus
106 96 82 97 97
0.681 0.966 1.291 1.302 1.462
4.489 6,487 7.737 9.679 9.210
0.312 0.334 0.354 0.419
1.870 1.954 2.128 2.440
0.229 0.520 0.536 0.955 1.533
1.455 2.847 4.394 4.917 9.622
M. edulis
42, 45, 42, 40,
42, 46, 42, 41,
48, 48, 44, 47,
54 50 51 48
San Diego Quivera Basin
05/24•73 M. edulis
55, 59, 66, 63, 50,
68 64 74 64 75
San Diego Shelter Island
05/24/73 M. edulis
69 98 71 75
0.657 0.957 1.892 1.750
3.486 5.487 12.89 12.89
La Salina, Baja California
05/09/73 M. caliJornianus
118 111 124 135
0.177 0.207 0.254 0.466
1.136 1.403 2.329 4.179
Ensenada, Baja California Harbor Marina
05/08/73 M. edutis
60, 66, 60, 62,
73 68 73 65
0.179 0.504 0.643 0.833
1.172 3.639 4.519 5.723
Punta Banda, Baja California
05/08/73 M. cal(lbrnianus
61, 66, 75, 66,
65 76 77 85
0.335 0.322 0.390 0.588
2.188 2.451 3.090 4.327
the same sizes (15, 22, and 35 mm long, respectively) could differ about 10 to 20 % in their lead content. Lead concentrations among these three groups of samples could vary as much as 35 96. He also stated that specimens of small size con59
tained more parts per million of lead than those of large size. Our results did not show this relationship. (Except in the case of the San Clemente sample, which consisted of 20 juveniles, all of our Mytilus were mature specimens which measured 40 to 98 mm in length for M. edulis, and 37 to 135 mm for M. californianus.) A definite correlation between the lead content of Mytilus and man's activity along the coastal zone was observed. For regions in California such as Piedras Blancas, Cayucos and Gaviota, which are sparsely populated, the lead content of the soft parts of M. californianus was lowest, averaging from 0.32 to 0.85 ppm on a dry weight basis. Lead contents of those collected at Goleta Point and Rincon Point increased slightly to 1.06 and 1.30 ppm, respectively. Higher lead contents were obtained in M. californianus collected southward along the more densely populated coast. The highest average for M. californianus, which was found in La Jolla specimens, was 7.96 ppm of lead, a value about 15-fold higher than that of the Cayucos samples. Mytilus edulis is usually found in quiet waters; therefore, with one exception, specimens of M. edulis were collected from docks in marinas or bays where
TABLE 2 LEAD CONTENTS IN VARIOUS ORGANS OF Mytilus sp.
Location
Muscle
Gill
Stomach
Gonad
Umbo shell
Posteriorshell
Pb(p.p.m.)
Pb (p.p.m.)
Pb (p.p.m.) Pb (p.p.m.) Pb (p.p.m.) Pb (p.p.m.)
Wet Dry
Wet Dry
Wet Dry
Wet Dry
Wet Dry
Wet Dry
0.315 1.671 0.102 0.627
0.103 0.542 0.081 0.483
0.526 0.544 0.311 0.337
0.275 0.286 0.344 0.366
Mytilus caliJbrnianus Gaviota State Beach0.144 0.662 0.520 3.280 0.082 0.414 0.234 1.824 San Diego 0.971 6.098 LaJolla, Scripps Pier 0.544 3.401 La Salina Baja California
0.262 1.550 0.886 7.971 0.375 2.302 0.856 6.212 * 0.432 2.443
Punta Banda Baja California
2.356 20.13 . 0.653 4.029 0.572 4.311 1.105 9.093 0.179 1.469 0.312 2.251
0.793 8.140
0.230 1.470 0.070 0.554
0.319 2.103 0.t08 0.707
1.182 1.265 1.666 1.748 1.252 1.351 1.341 1.404 0.264 0.280 0.280 0.298
0.265 1.738 0.179 1.408
0.320 0.341 0.436 0.458 0.291 0.304
0.198 1.017 0.441 3.554 0.196 1.007 0.450 3.556
0.222 1.318 0.222 1.483 0.394 0.420 0.476 0.490 0.076 0.465 0.260 1.987 0.579 0.602 0.805 0.833
Santa Barbara Harbor Marina
0.494 2.310 0.451 2.248
3.455 22.96 2.059 14.64
0.876 4.862 0.699 3.387 0.962 5.412 0.253 1.322
1.973 2.157 1.652 1.770
2.658 2.737** 1.699 1.850
Long Beach Harbor Marina
1.782 9.358 1.599 9.253
3.952 31.04 3.602 31.44
1.060 7.864 0.739 4.792 1.069 7.914 1.236 8.076
3.897 4.139 3.977 4.439
7.863 8.529 6.113 6.797
San Diego Shelter Island
0.359 1.737 0.923 6.063 0.962 4.789 1.832 15.33
0.478 2.493 2.102 2.205 0.290 1.821 1.969 2.094
1.759 1.879 2.172 2.328
Mytilus edulis
* One large specimen. ** One whole valve.
60
0.968 4.717 0.334 2.105
the effect of man's activity is definitely evident. Mytilus edulis from Anaheim Bay showed the highest lead content average of 33 ppm. This concentration is about 100 times that of the lowest concentration found. The lead content of the soft parts of M. edulis taken at Santa Barbara harbor marina showed a significant increase from 3.45 ppm in October 1972 to 11.7 ppm in September 1973. The Baja California samples also showed relatively high lead contents in the soft parts of both mussel species, averaging from 2.3 to 3.8 ppm. From San Diego's Pacific Beach Pier, both species of mussels were collected from the same pier piling, with M. californianus facing the ocean and M. edulis on the landward side. The lead content average of M. californianus (7.5 ppm) was considerably higher than that of M. edulis (2.1 ppm). Schulz-Baldes (1973) showed that the lead content of the soft parts of M. edulis collected near Bremerhaven was 6.4 ppm and decreased seaward reaching a concentration of 1.9 ppm at the Helgoland Island, which is about 80 km offshore. In this case, the source of lead pollutants was the discharge from the Weser estuary. The lead concentrations of various organs in representative mussels selected from those locations showing high and low lead content in whole soft parts were determined. Gill, stomach, muscle, and gonad tissues were dissected from 3 or 4 specimens. Results of lead analyses of these pooled organs and the calcareous shells are given in Table 2. Duplicate samples of each tissues showed variations in lead content similar to those observed for the whole soft parts analyses. Organs from harbor mussels contained higher lead content than corresponding parts in mussels from relatively undisturbed regions. Since we did not find both species at the same site in the less polluted areas, species orientation of lead content could not be evaluated. Among various organs the gill tissues contained the highest amount of lead. This finding might be expected due to the-fact that sea water is continuously circulated past the gills, and the removal of heavy metals from sea water by the gills through chelation and physical trapping would promote pollutant concentration in this organ. The relatively high lead content in the stomachs of mussels from polluted harbors resulted from food intake. The lead content of mussel shells also reflects habitat lead concentrations, with the highest lead contents in the harbor mussels. The lead distribution in the shell was not uniform, as shown in the analyses of the umbo portion versus posterior portion. The umbo part of the shell generally contained less lead than the posterior region. No difference was observed in the average isotope ratios of lead in Mytilus edulis and in M. californianus (Table 3). For Santa Barbara and Long Beach samples, lead in both the calcareous shell and soft parts showed similar isotope ratios. The average isotope ratios of lead in Mytilus sp. collected six months apart in 1972 and 1973 were similar within analytical error; the time span was too short to reflect any long-term change in lead isotope ratios. The mussel lead isotope ratios were in reasonable agreement with those of the 1969-1971 aerosol lead which were ~ P b / ~ P b = l S . 6 8 , ~PbP°rPb=l.187, and ~Pb/~Pb--0.4859 (Chow et al., 61
TABLE 3 ISOTOPE RATIOS OF LEAD IN My#/us sp. Location
Species
Date collected
Material
~aaPb 21~pb
ao6Pb ~
~l~pb
Piedras Blancas South of lighthouse
M. cal~ornianus
10/21/72
soft parts
18.79
1 . 1 9 3 0.4859
Gaviota State Beach
M. cal~ornianus
10/23/72
soft parts
--
1.191
Santa Barbara Harbor Marina
M. edulis
10/24/72
soft parts shell
18.54 18.47
!.183 0.4845 1 . 1 8 2 0.4841
0.4839
Long Beach Harbor Marina
M. edulis
04/11/73
soft parts shell
18.68 18.56
1 . 1 8 7 0.4842 1 . 1 8 7 0.4869
(~eanside Harbor Marina
M. edulis
04/11/73
soft parts
18.59
1 . 1 8 4 0.4855
San Diego La Jolla Scripps Pier and Pacific Beach Pier
M. calilornianus
04/12/73 05/24/73
soft parts shell
18.60 18.38
1.185 0.4843 1 . 1 7 8 0.4746
Punta Banda and La Salina M. callJornianus Baja California
05/08/73 05/09/73
soft parts
18.37
1 . 1 7 6 0.4790
1975). From the geographic distribution of samples, there was a significant difference in lead isotope ratios between the Piedras Blancas, California and the Baja California mussel samples. With limited isotopic data on hand, no attempt was made to interpret the meaning of that differenre. ACKNOWLEDGEMENTS
This study was supported by a National Science Foundation IDOE grant. We thank Raelyn Cole for editing the manuscript. REFERENCES Brooks, R. R. and R. G. Rumsby, Limnol. Oceanogr., 10 (1965) 524. Bryan, G. W., J. Mar. BioL Ass. U.K.~ 53 (1973) 145. Chow, T. J., ('hem. Brit., 9 (1973) 258. Chow, T. J. and C. C. Patterson, Earth Planet. Sci. Lett., 1 (1966) 397. Chow, T. J., C. B. Snyder and J. L. Earl, Isotope ratios of lead as pollutant source indicator, in Joint FAO/IAEA Symposium on Isotope Ratios As Pollutant Source and Behaviour Indicator, 1AEA, Vienna, 1975, pp. 95-108. Goldberg, E. D., Review of Trace Element Concentrations 01 Marine Organisms, Puerto Rico Nuclear Center, Mayaguez, 1965, 535 pp. Graham, D., Veliger, 14 (1971) 365. International Decade of Ocean Exploration (IDOE), Marine Environmental Quality, National Science Foundation, Washington, D. C., 1971, 107 pp. Nickless, G., R. Stenner and N. Terrille, Mat'. Pollut. Bull., 3 (1972) 188. Patterson, C. C., Mar. Chem., 2 (1974) 69. Pringle, B. H., D. E. Hissong, E. L. Katz and S. T. Mulawka, J. Sanit. Eng. Div., Amer. Soc. Cir. Eng., 94 (1968) 455.
62
Segar, D. A., J. D. ColLins and J. P. Riley, J. Mar. Biol. Ass. U.K., 51 (1971) 131. Schulz-Baldes, M., Mar. Biol., 16 (1972) 226. Schulz-Baldes, M., Mar. Biol., 21 (1973) 98. Schulz-Baldes, M., Mar. Biol., 25 (1974) 177. Vinogradov, A. P., The Elementary Composition of Marine Organisms, Sears Found. Mar. Res. Mem. New Haven, 1953, 647 pp.
63
MUSSELS (Mytilus sp) AS AN INDICATOR OF LEAD POLLUTION
TSAIHWA J. CHOW, H. GEORGE SNYDER and CARRIE B, SNYDER Scripps Institution of Oceanography, La Jolla, CaliJ~ 92093 (U.S.A.) (Received October 29th, 1975)
ABSTRACT
The lead contents of two species of mussels (Mytilus californianus and M. edulis) collected along the Pacific coast from Piedras Blancas, California to Punta Banda, Baja California were determined by isotope dilution method. The whole soft parts of the mussels, on a dry weight basis, contained from 0.27 to 42 ppm of lead, which can be related to their local habitats. The gill tissues of the mussels showed the highest lead concentration.
INTRODUCTION
Adverse effects of toxic substances on the environmental quality have become a concern in recent years. Lead is one of the identifiable heavy metal pollutants (Chow, 1973), and its rate of introduction into the ocean through man's activity surpasses that by river runoffs (IDOE, 1971). Thus, the lead content of coastal surface sea water has increased considerably in relation to that in the deep ocean water (Chow and Patterson, 1966; Patterson, 1974); this is especially evident along the industrialized coastal zones. Trace metal concentrations of sea water are one of the factors which influence those concentrations in marine organisms. Vinogradov (1953) and Goldberg (1965) reviewed earlier literature on chemical composition of marine organisms. More recently, contents of heavy metals, including lead, were determined in molluscs from various geographic regions (Brooks and Rumsby, 1965; Pringle, et al., 1968; Graham, 1971; Segar, et al., 1971; Nickless, et al., 1972; Bryan, 1973; Schulz-Baldes, 1972, 1973, 1974). SAMPLING AND ANALYSIS
Mytilus sp. w a s c h o s e n as t h e r e p r e s e n t a t i v e o r g a n i s m for this s t u d y bec a u s e o f its w o r l d - w i d e d i s t r i b u t i o n a n d g e n e r a l availability in t h e intertidal zone.
55
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Fig. 1. Collection sites of Mytilus sp. along the California and Baja California coasts, and description of their habitats. 1 = Piedras Blancas. South of Coast Guard Lighthouse exposed coast, rocky low intertidal reef. 2 = Cayucos. 6 km North of Village---exposed coast, rocky low intertidal reef. 3 = Cayucos. 0:6 km North of Village--semi-protected coast, sandy beach with elevated rocks in sand. 4 = Cayucos. Pier about 3 km South of Village---open coast, piling community. S = Gaviota. California State Beach--exposed coast, rock ledges and boulders. 6 = Goleta Point. University of California at Santa Barbara----exposed coast, rocky. 7 = Santa Barbara. Harbor Marina--protected inlet. 8 = Rincon Point. Sere/protected coast, rocky with tidal flats. 9 = Long Beach. Harbor Marina--protected inlet. 10 = Anaheim Bay. Gasoline Station Fueling Dock--mud flats and protected slough, piling community. 11 = San Clemente. Pier--open coast, piling community. 12 = Oceans/de. Harbor Marina--protected inlet. 13 = La Jolla. Scripps Institution of Oceanography Pier---open coast, piling community. 14 = San Diego. Pacific Beach Pier--open coast, piling community. 15 = San Diego. Quivera Basin-protected inlet. 16 = San Diego. Shelter Island-lsemiprotected harbor channel. 17 = La Salina, Baja California. Open coast, sandy beach and rocky tide pools. 18 = Ensenada, Baja California. Harbor-protected inlet. 19 = Punta Banda, Baja California. Open coast, rock ledges and tide pools.
56
Specimens were collected along the Pacific coast in 1972 and 1973 from Piedras Biancas (35°40'N, 121°17'W) near San Simeon, Calif., to Punta Banda (31°45'N, 116°45'W) near Ensenada in Baja California, Mexico. This coastal zone depicts varying degrees of industrialization ranging from relatively undisturbed to heavily populated regions. The geographic locations as well as the description of their habitats are given in Fig. 1. In the laboratory the specimens were stored in a freezer at a temperature of -15°C. Frozen specimens were cleaned and allowed to defrost. Then, they were weighed, measured, and dissected. From additional specimens of selected localities, the soft parts were dissected for various anatomical organs. Due to the small size of some organs, several specimens from the same site were pooled in order to provide sufficient material for analysis. The wet tissues were dried at 110°C to constant weight and then ashed at 500°C to destroy the organic matter. Known weight of stable m6Pb tracer was equilibrated with the lead in the ash during digestion and oxidation; the lead isotope mixtures were isolated by ion-exchange and dithizone extraction, and were analyzed in a mass spectrometer. Separate samples without adding the stable lead tracer were used for the isotope ratios determination. The reagent blank was 0.1 gg of lead per sample of 10g size. The following 90 96 confidence interval limits were assigned: ~ P b / ~ P b , 0.3 %; ~Pb/mTpb, 0.1%; and ~ P b / ~ P b , 0.2 96. RESULTS AND DISCUSSION Previous investigators reporting trace metal concentrations of marine organisms have used either a wet or a dry weight basis. Since this practice often causes some difficulty when attempting to compare results from different laboratories, we report our results, which were amended to account for the reagent blank, on both a wet and a dry weight basis (Table 1). A least square fit is derived by plotting the average lead contents of wet versus dry weight basis of the soft parts of mussels representing respective sampling locations. The Anaheim Bay saml)le was excluded in the calculation because it contained an abnormally high lead concentration. A linear relationship between wet and dry weight basis of lead contents is obtained. Pb (wet weight)=0.139xPb (dry weight)+0.03 Individual samples, which mostly were composed of whole soft parts of one or two Mytilus, showed variability in lead contents. The mean deviations from the concentration average of respective locations ranged from 8 to 48 %. These variations may be attributed to the diversity in size and age of the specimens, as well as to their position in the intertidal zone. Specimens located at the high water habitat would be exposed to the most lead pollutants (Graham, 1971). Schulz-Baldes (1973) found similar lead concentration variations among M. edulis collected near Bremerhaven, G.F.R. He reported that individual samples of 57
TABLE 1 LEAD CONTENTS IN WHOLE SOFT PARTS OF Mvtilus sp. Pb (p.p.m.) Location Piedras Blancas South of lighthouse
Date collected
Species
Length (mnO
Wet wt.
Dry wt.
10/21/72 M. cal(lornianus
50, 80 58 54, 72 49
0.094 0.150 0.174 0.179
0.556 0.824 0.958 1.057
Cayucos, 6 km north of village 10/22/72 M. cal~/ornianus
39, 43 45, 47 42, 50 37, 47
0.135 0.147 0.153 0.194
0.683 0.738 0.815 0.993
Cayucos, 0.6 km nonh of village 09/14/73
M. caliJbrnianus
78 80 76
0.104 0.125 0.170
0.386 0.507 0.688
Cayucos, 3 km south of village Pier
09/14/73
M. cal(lornianus
103 74 89 107
0.065 0.082 0.086 0.094
0.265 0.325 0.339 0.342
Gaviota State Beach
10/23/72 M. caliJornianus
95 86 84
0.118 0.159 0.170
0.568 0.808 0.859
Goleta Point
10/24/72 M. caliJornianus~
85 87 80 77
0.131 0.199 0.235 0.252
0.664 1.054 1.150 1.355
Santa Barbara Harbor Marina
10/24/72 M. edulis
77 95 77
0.586 0.630 1.086
2.471 3.500 4.395
Santa Barbara Harbor Marina
09/13/73
77 78 80
0.651 1.746 2.062
4.752 11.54 18.87
Rincon Point
10/25/72 M. caliJornianus
87 100 97 95
0.124 0.202 0.276 0.426
0.596 0.968 1.312 2.341
Long Beach Harbor Marina
04/11/73
M. edulis
78 68, 70 69 85 79
1.422 1 696 2.311 3.051 4.012
8.11 9.48 19.81 24.92 24.46
Anaheim Bay Gasoline station fueling dock
04/11/73
M. edulis
78 73 57, 61 70 68, 73
3.222 3.360 3.669 4.083 4.162
24.62 30.53 31.63 41.97 36.32
San Clemente Pier
04/13 / 73 M. cal(/ornianus (20 juveniles)
20-25
0.520
58
M. edulis
3.393
TABLE 1 (Continued) Pb (p.p.m.) Location
Date collected
Species
Length (mnO
I+'et wt.
Dry wt.
60, 62 55, 57, 65 50, 70, 75 70 72
0.338 0.498 0.619 0.700 0.898
4.878 5.150 5.669 6.917 9.963
Oceanside Harbor Marina
04/11/73 M. edulis
San Diego La Jolla SIO Pier
04/12/73 M. cal~ornmnus
92 100 110 104 97
0.817 0.884 0.922 0.952 1.400
6.276 6.542 7.617 8.334 11.03
San Diego Pacific Beach Pier
05/24/73 M. cal~brnianus
106 96 82 97 97
0.681 0.966 1.291 1.302 1.462
4.489 6,487 7.737 9.679 9.210
0.312 0.334 0.354 0.419
1.870 1.954 2.128 2.440
0.229 0.520 0.536 0.955 1.533
1.455 2.847 4.394 4.917 9.622
M. edulis
42, 45, 42, 40,
42, 46, 42, 41,
48, 48, 44, 47,
54 50 51 48
San Diego Quivera Basin
05/24•73 M. edulis
55, 59, 66, 63, 50,
68 64 74 64 75
San Diego Shelter Island
05/24/73 M. edulis
69 98 71 75
0.657 0.957 1.892 1.750
3.486 5.487 12.89 12.89
La Salina, Baja California
05/09/73 M. caliJornianus
118 111 124 135
0.177 0.207 0.254 0.466
1.136 1.403 2.329 4.179
Ensenada, Baja California Harbor Marina
05/08/73 M. edutis
60, 66, 60, 62,
73 68 73 65
0.179 0.504 0.643 0.833
1.172 3.639 4.519 5.723
Punta Banda, Baja California
05/08/73 M. cal(lbrnianus
61, 66, 75, 66,
65 76 77 85
0.335 0.322 0.390 0.588
2.188 2.451 3.090 4.327
the same sizes (15, 22, and 35 mm long, respectively) could differ about 10 to 20 % in their lead content. Lead concentrations among these three groups of samples could vary as much as 35 96. He also stated that specimens of small size con59
tained more parts per million of lead than those of large size. Our results did not show this relationship. (Except in the case of the San Clemente sample, which consisted of 20 juveniles, all of our Mytilus were mature specimens which measured 40 to 98 mm in length for M. edulis, and 37 to 135 mm for M. californianus.) A definite correlation between the lead content of Mytilus and man's activity along the coastal zone was observed. For regions in California such as Piedras Blancas, Cayucos and Gaviota, which are sparsely populated, the lead content of the soft parts of M. californianus was lowest, averaging from 0.32 to 0.85 ppm on a dry weight basis. Lead contents of those collected at Goleta Point and Rincon Point increased slightly to 1.06 and 1.30 ppm, respectively. Higher lead contents were obtained in M. californianus collected southward along the more densely populated coast. The highest average for M. californianus, which was found in La Jolla specimens, was 7.96 ppm of lead, a value about 15-fold higher than that of the Cayucos samples. Mytilus edulis is usually found in quiet waters; therefore, with one exception, specimens of M. edulis were collected from docks in marinas or bays where
TABLE 2 LEAD CONTENTS IN VARIOUS ORGANS OF Mytilus sp.
Location
Muscle
Gill
Stomach
Gonad
Umbo shell
Posteriorshell
Pb(p.p.m.)
Pb (p.p.m.)
Pb (p.p.m.) Pb (p.p.m.) Pb (p.p.m.) Pb (p.p.m.)
Wet Dry
Wet Dry
Wet Dry
Wet Dry
Wet Dry
Wet Dry
0.315 1.671 0.102 0.627
0.103 0.542 0.081 0.483
0.526 0.544 0.311 0.337
0.275 0.286 0.344 0.366
Mytilus caliJbrnianus Gaviota State Beach0.144 0.662 0.520 3.280 0.082 0.414 0.234 1.824 San Diego 0.971 6.098 LaJolla, Scripps Pier 0.544 3.401 La Salina Baja California
0.262 1.550 0.886 7.971 0.375 2.302 0.856 6.212 * 0.432 2.443
Punta Banda Baja California
2.356 20.13 . 0.653 4.029 0.572 4.311 1.105 9.093 0.179 1.469 0.312 2.251
0.793 8.140
0.230 1.470 0.070 0.554
0.319 2.103 0.t08 0.707
1.182 1.265 1.666 1.748 1.252 1.351 1.341 1.404 0.264 0.280 0.280 0.298
0.265 1.738 0.179 1.408
0.320 0.341 0.436 0.458 0.291 0.304
0.198 1.017 0.441 3.554 0.196 1.007 0.450 3.556
0.222 1.318 0.222 1.483 0.394 0.420 0.476 0.490 0.076 0.465 0.260 1.987 0.579 0.602 0.805 0.833
Santa Barbara Harbor Marina
0.494 2.310 0.451 2.248
3.455 22.96 2.059 14.64
0.876 4.862 0.699 3.387 0.962 5.412 0.253 1.322
1.973 2.157 1.652 1.770
2.658 2.737** 1.699 1.850
Long Beach Harbor Marina
1.782 9.358 1.599 9.253
3.952 31.04 3.602 31.44
1.060 7.864 0.739 4.792 1.069 7.914 1.236 8.076
3.897 4.139 3.977 4.439
7.863 8.529 6.113 6.797
San Diego Shelter Island
0.359 1.737 0.923 6.063 0.962 4.789 1.832 15.33
0.478 2.493 2.102 2.205 0.290 1.821 1.969 2.094
1.759 1.879 2.172 2.328
Mytilus edulis
* One large specimen. ** One whole valve.
60
0.968 4.717 0.334 2.105
the effect of man's activity is definitely evident. Mytilus edulis from Anaheim Bay showed the highest lead content average of 33 ppm. This concentration is about 100 times that of the lowest concentration found. The lead content of the soft parts of M. edulis taken at Santa Barbara harbor marina showed a significant increase from 3.45 ppm in October 1972 to 11.7 ppm in September 1973. The Baja California samples also showed relatively high lead contents in the soft parts of both mussel species, averaging from 2.3 to 3.8 ppm. From San Diego's Pacific Beach Pier, both species of mussels were collected from the same pier piling, with M. californianus facing the ocean and M. edulis on the landward side. The lead content average of M. californianus (7.5 ppm) was considerably higher than that of M. edulis (2.1 ppm). Schulz-Baldes (1973) showed that the lead content of the soft parts of M. edulis collected near Bremerhaven was 6.4 ppm and decreased seaward reaching a concentration of 1.9 ppm at the Helgoland Island, which is about 80 km offshore. In this case, the source of lead pollutants was the discharge from the Weser estuary. The lead concentrations of various organs in representative mussels selected from those locations showing high and low lead content in whole soft parts were determined. Gill, stomach, muscle, and gonad tissues were dissected from 3 or 4 specimens. Results of lead analyses of these pooled organs and the calcareous shells are given in Table 2. Duplicate samples of each tissues showed variations in lead content similar to those observed for the whole soft parts analyses. Organs from harbor mussels contained higher lead content than corresponding parts in mussels from relatively undisturbed regions. Since we did not find both species at the same site in the less polluted areas, species orientation of lead content could not be evaluated. Among various organs the gill tissues contained the highest amount of lead. This finding might be expected due to the-fact that sea water is continuously circulated past the gills, and the removal of heavy metals from sea water by the gills through chelation and physical trapping would promote pollutant concentration in this organ. The relatively high lead content in the stomachs of mussels from polluted harbors resulted from food intake. The lead content of mussel shells also reflects habitat lead concentrations, with the highest lead contents in the harbor mussels. The lead distribution in the shell was not uniform, as shown in the analyses of the umbo portion versus posterior portion. The umbo part of the shell generally contained less lead than the posterior region. No difference was observed in the average isotope ratios of lead in Mytilus edulis and in M. californianus (Table 3). For Santa Barbara and Long Beach samples, lead in both the calcareous shell and soft parts showed similar isotope ratios. The average isotope ratios of lead in Mytilus sp. collected six months apart in 1972 and 1973 were similar within analytical error; the time span was too short to reflect any long-term change in lead isotope ratios. The mussel lead isotope ratios were in reasonable agreement with those of the 1969-1971 aerosol lead which were ~ P b / ~ P b = l S . 6 8 , ~PbP°rPb=l.187, and ~Pb/~Pb--0.4859 (Chow et al., 61
TABLE 3 ISOTOPE RATIOS OF LEAD IN My#/us sp. Location
Species
Date collected
Material
~aaPb 21~pb
ao6Pb ~
~l~pb
Piedras Blancas South of lighthouse
M. cal~ornianus
10/21/72
soft parts
18.79
1 . 1 9 3 0.4859
Gaviota State Beach
M. cal~ornianus
10/23/72
soft parts
--
1.191
Santa Barbara Harbor Marina
M. edulis
10/24/72
soft parts shell
18.54 18.47
!.183 0.4845 1 . 1 8 2 0.4841
0.4839
Long Beach Harbor Marina
M. edulis
04/11/73
soft parts shell
18.68 18.56
1 . 1 8 7 0.4842 1 . 1 8 7 0.4869
(~eanside Harbor Marina
M. edulis
04/11/73
soft parts
18.59
1 . 1 8 4 0.4855
San Diego La Jolla Scripps Pier and Pacific Beach Pier
M. calilornianus
04/12/73 05/24/73
soft parts shell
18.60 18.38
1.185 0.4843 1 . 1 7 8 0.4746
Punta Banda and La Salina M. callJornianus Baja California
05/08/73 05/09/73
soft parts
18.37
1 . 1 7 6 0.4790
1975). From the geographic distribution of samples, there was a significant difference in lead isotope ratios between the Piedras Blancas, California and the Baja California mussel samples. With limited isotopic data on hand, no attempt was made to interpret the meaning of that differenre. ACKNOWLEDGEMENTS
This study was supported by a National Science Foundation IDOE grant. We thank Raelyn Cole for editing the manuscript. REFERENCES Brooks, R. R. and R. G. Rumsby, Limnol. Oceanogr., 10 (1965) 524. Bryan, G. W., J. Mar. BioL Ass. U.K.~ 53 (1973) 145. Chow, T. J., ('hem. Brit., 9 (1973) 258. Chow, T. J. and C. C. Patterson, Earth Planet. Sci. Lett., 1 (1966) 397. Chow, T. J., C. B. Snyder and J. L. Earl, Isotope ratios of lead as pollutant source indicator, in Joint FAO/IAEA Symposium on Isotope Ratios As Pollutant Source and Behaviour Indicator, 1AEA, Vienna, 1975, pp. 95-108. Goldberg, E. D., Review of Trace Element Concentrations 01 Marine Organisms, Puerto Rico Nuclear Center, Mayaguez, 1965, 535 pp. Graham, D., Veliger, 14 (1971) 365. International Decade of Ocean Exploration (IDOE), Marine Environmental Quality, National Science Foundation, Washington, D. C., 1971, 107 pp. Nickless, G., R. Stenner and N. Terrille, Mat'. Pollut. Bull., 3 (1972) 188. Patterson, C. C., Mar. Chem., 2 (1974) 69. Pringle, B. H., D. E. Hissong, E. L. Katz and S. T. Mulawka, J. Sanit. Eng. Div., Amer. Soc. Cir. Eng., 94 (1968) 455.
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Segar, D. A., J. D. ColLins and J. P. Riley, J. Mar. Biol. Ass. U.K., 51 (1971) 131. Schulz-Baldes, M., Mar. Biol., 16 (1972) 226. Schulz-Baldes, M., Mar. Biol., 21 (1973) 98. Schulz-Baldes, M., Mar. Biol., 25 (1974) 177. Vinogradov, A. P., The Elementary Composition of Marine Organisms, Sears Found. Mar. Res. Mem. New Haven, 1953, 647 pp.
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