FACT SHEET ON THE STATE OF THE MARINE ENVIRONMENT Of THE ST. LAWRENCE

MERCURY CONTAMINATION OF NORTHERN SHRIMP IN THE SAGUENAY FJORD

The Saguenay Fjord is a well-documented case of In the early 1970s, government and university scien­ mercury contamination both in Canada and world­ tists found high levels of mercury in organisms that wide. The Saguenay Fjord is also one of the few live or feed near the bottom of the Saguenay Fjord. The northern Specifically, concentrations of mercury in northern shrimp, places in Eastern Canada where fishing is prohibited Panda/us borea/is. because of chemical contamination. shrimp, Panda/us borealis, were 20 times higher than the Canadian Guideline for Contaminants in Fish and Fish Products. This limit is recommended by Health Canada and is set at 0.5 µg of mercury per gram of wet weight of edible flesh (µg/g). These observations led to the closure of the shrimp fishery in the Saguenay Fjord and it has not been reestablished since then. In 1971, sales of shrimp from the Fjord were prohibited by the Department of Fisheries and Environment Canada. Furthermore, since the mer­ QH cury pollution was caused 541.5 mainly by industrial effluents, .SJ F48 in 1972, this federal depart­ No ment established regulations 2E to limit industrial discharges of mercury effluents into the environment.

Fisheries and Oceans Peches et Oceans ••• Canada Canada Canada SOURCES OF CONTAMINATION GRADUAL IMPROVEMENT

Mercury can occur naturally in low concentrations in The northern shrimp feeds in the water column but continental soils, the earth's crust, water and the atmos­ also close to bottom sediments where its diet phere. However, many human activities have led to includes suspended particles, sediments, and ben­ substantial releases of mercury into the environment. thic organisms such as marine worms and amphipods. The feeding habits of this species Industrial effluents from chloralkali plants and pulp make it a good bio-indicator of the state of the and paper mills as well as municipal sewage are the environment, and it has been used extensively as main point sources of mercury. Groundwater and such to monitor mercury levels in the Saguenay run-off from urban, industrial and agricultural activi­ Fjord. In fact, the northern shrimp is the only organism ties, hazardous waste sites, atmospheric inputs, in the Fjord for which there is data describing tissue tributaries and salt water intrusions from the St. levels of mercury over the past 20 years (see Fig. 1) . Lawrence Estuary constitute non-point sources of mercury. As a result of the reduction in mercury effluents in the early 1970s and the total elimination of dis­ The ALCAN Smelters and Chemicals Ltd. chloralkali charges when the chloralkali plant closed in 1976, complex in Jonquiere has been identified as the the degree of contamination of shrimp has principal historical source of mercury contamination declined considerably. In 1983, mercury concen­ in the Saguenay Fjord . This plant produced chlorine trations were approximately 20 times lower than in and caustic soda by a mercury cell process until its 1970. However, to date, mercury levels measured closure in 1976. Up until 1972, when the federal in shrimps sampled in the Fjord are still 4 to 5 government enforced regulations restricting mercury times higher than those found in shrimps of similar levels in industrial effluents, the plant apparently size in the Estuary and Gulf of St. Lawrence as well discharged at least 145 metric tonnes of mercury as in areas not affected by a direct source of pollu­ waste into the Saguenay. It is estimated that tion. Over the last ten years, mercury concentra­

Map of the between 20 and 120 metric tonnes of this amount tions in shrimp from the Saguenay Fjord appear to Saguenay Fjord have become buried in sediments of the Saguenay have stabilized at approximately 0.5 µg/g. and location of the three deep Fjord, while the remainder would have been trans­ basins and their sill. ported to the St. Lawrence Estuary.

0

N 50 THE SAGUENAY FJORD ,... A ....,E 100 The Saguenay Fjord, located about 160 km northeast ~ 150 Of Quebec City, extends over nearly 100 kilometres ~ 200 between Sa1nt-Fulgence and Tadoussac. Its waters 250 flow in an ancient glacial valley and are discharged into the Lower St. Lawrence Estuary. The upper part of the Fjord is "Y" -shaped, with the southern arm forming Ba1e des Ha! Ha! and the northern arm, the main branch of the Fjord into which the Saguenay River outflows. Three sills, which form underwater mountains, delimit three deep basins. The Inner Basin, located upstream, 1s 275 metres deep and covers three quarters of the Fjord. The Middle and Outer Basins are respectively 180 and 275 metres deep.

II TOXICITY OF MERCURY

Mercury is a non-essential metal for living organisms. While the inorganic form of this metal is only slightly toxic, methylmercury, an organic compound, is more toxic than the inorganic mercury. Methylmercury is produced mainly by bacteria in anoxic layers of sediment which are rich in organic matter. Its bioavailability being higher than that of inorganic mercury, methyl mercury is the principal chemical form of mercury bioaccumulated by aquatic organisms. Beyond certain thresholds of accumulation, methylmercury can impair cellular function by interfering with various biochemical processes. Methylmercury is particularly toxic to aquatic organisms and humans, since it damages the nervous system. It is bioaccumulated throughout the food chain, making it unsafe to exploit certain species of fish and shellfish for human consumption.

As a result of the hydrodynamics of the Saguenay m 12 --~~~~~~~~~~~~~---. Fjord, fine-grained sediments, with which contami­ e; ...... Canadian Guideline for Contaminants ,a. 10 In Fish and Fish Products =0.5 µg/g nants tend to associate, are deposited primarily in ~ :J the deep basins. Abrupt changes in topography ~ 8 E and water circulation which characterize the upper 0 6 c: part of the Inner Basin, between Saint-Fulgence and 0 Fig . 1 ti 4 the mouth of Baie des Ha! Ha!, make it one of the Temporal trends ~ in mercury main areas of sedimentation and therefore of mer­ c:~ 2 concentrations 0 cury accumulation in the Fjord. The contamination (µgig) in Saguenay u o J:::.:.::.:..:.:;.:.:::.:=::.;.::::.::::~~~9!!!1:;::::.~~~ Fjord shrimp since 1968 1972 1976 1980 1984 1988 1992 1996 problem was thus particularly severe in the upper the early 1970s. Year part of the Fjord, which received the bulk of indus­ trial effluents from the choralkali complex. SEDIMENTS: A RESERVOIR OF MERCURY In the 1960s (see Fig. 2), mercury concentrations in surface sediments of the Inner Basin of the Saguenay Why do shrimps in the Saguenay Fjord still contain Fjord were up to 40 times higher than natural levels mercury concentrations higher than natural levels, if (0.05 µg of mercury per gram of dry sediment) the polluting plant stopped its mercury discharges which existed before the industrial era. The low nearly 20 years ago? Is it possible that the habitat of concentrations of mercury measured in these sur­ the shrimp is still contaminated with mercury face sediments in the early 1970s correspond to the despite the shutdown of the plant? Research on major landslide that occurred at Saint-Jean-Vianney contaminated sediments in the Saguenay Fjord has in 1971. Massive quantities of uncontaminated sedi­ shed some light on this situation. ments that were deposited in the Fjord at that time covered the contaminated layer, resulting in a dra­ 10 ma~ic reduction in observed mercury levels. ~ 9 ...... Pre-Industrial level =0.05 µg/g O> Excluding this exceptional event, mercury levels in ,a. 8 $' 7 sediments began to decline in the mid-1970s. ~ G> 6 Although mercury concentrations in the Fjord sedi­ E 0 5 ments were appreciably lower in 1983, they were Fig. 2 g 4 Salnl-Jean-Vlanney's landslide still 4 to 17 times higher than pre-industrial levels. Temporal trends 3 in mercury Ec: The most recent mercury concentrations in surface G> 2 concentrations 0c: 1 sediments, reported in 1992, revealed a continuing (µgig) in surface u0 sediments of the 0 ' decrease. However, they were still 7 times above Inner Basin of the 1960 1965 1970 1975 1980 1985 1990 1995 baseline levels and twice as high as those reported Saguenay Fjord. Year from sites in the Lower St. Lawrence Estuary. II A RECORD OF THE PAST Concentration of mercury (µg/g) 0 2 3 4 5 6 7 A sediment core contains successive layers of sedi­ 1976 0 ments that have been deposited over time. Thus, the analysis of sediment cores allows the establish­ 1972 2 ment of a chronology of mercury inputs, meaning a reconstruction of their history using sediment depo­ 1968 4 sition. Consequently, this illustrates the temporal trend of contamination in sediments of the 1964 Saguenay Fjord (see Fig. 3). 6

1960 'E Sediment cores collected in the Saguenay FJord 0 0 8 ...... QI typically present profiles of mercury levels which >- ~ 1956 QI are reflective of changes in operations at the chloral­ 0 10 kali plant. Mercury contamination of the sediments 1952 appears to have begun around 1950, which cor­ responds to initial operation of the plant. The highest 12 1948 concentrations are detected 1n sediments deposited r during the 1960s, when production capacity was 1944 14 increased. As a result of effluent control since 1972, a drastic reduction in mercury levels has been 1940 16 found in more recent sediment layers.

Fig . 3 Mercury concentrations in a sediment core collected in the north arm of the Saguenay Fjord.

WHY IS THERE STILL MERCURY IN SURFACE SEDIMENTS OF THE SAGUENAY FJORD?

The fact that surface sediments still contain mercury may seem surprising at first. The constant influx of uncontaminated or barely contaminated sediment should be expected to cause a gradual decrease in mercury concentrations.

Sediment \he most widely accepted hypothesis to explain core collected in this situation centres on bioturbation. This process the Saguenay Fjord. involves the physical mixing of sediments by the movements of benthic organisms which transfers \ mercury from deeper layers of sediment to the sur­ The similarity in temporal trends between mercury l face layer. As a result, mercury buried for decades levels in shrimp and those in surface sediments in bottom sediments of the Fjord's basins may illustrates the close link between this species and become re-incorporated into surficial sediments the quality of its habitat. In other words, the persis- 'and maintain their contamination. According to tence of mercury contamination in sediments may some researchers, it will be several decades before have a d irect influence on the degree of contami- we see a complete decontamination of surface nation of shrimp. sediments of the Saguenay Fjord. II ECOSYSTEM STILL AT RISK resources of the Saguenay Fjord. Further research wi II be necessary if we want to expand our current As a result of the enactment of federal regulations knowledge on the transfer mechanisms of mercury and the closure of the chloralkali plant, the from water and sediments to benthic organisms, on Saguenay Fjord appears to have partially recovered the environmental factors that regulate the bioaccu­ from its severe mercury contamination problem. mulation of methylmercury, and on the possible Mercury levels in shrimp from the Saguenay Fjord links between contamination and its potential bio­ have highly diminished since 1970s, but are still logical effects. With a better understanding of these usually close to the Canadian Guideline for con- processes, we will improve our capacity to predict the fate and effects of the different forms of mer­ cury in aquatic ecosystems.

Box corer used to sample sediments.

GLOSSARY

Anoxic: without oxygen. Benthic organism : aquatic organism that lives in contact with bottom sediments. Bioaccumulation : process whereby certain aquatic organisms accumulate chemicals directly from ambient water and sediments or from food sources. Bioavailability : portion of a contaminant present in the environment that can be accumulated by a .living organism. , Bio-indicator : organism used to monitor the sumption of Fish and Fish Products. Sediments 1degree of environmental contamination. 1 remain a reservoir of mercury and appear to be Bioturbation : process of physical mixing of sedi­ perpetuating mercury contamination in Saguenay ments by the movements of benthic organisms. Fjord shrimps. This situation explain$ the continued\ ban on all activities such as bottom trawling which Effluent : liquid discharges from a given pollution could resuspend contaminated sediments. The ) source. resuspension of sediments could increase the Habitat : part of the environment in which an bioavailability of mercury in the environment and organism, a species, a population or a group of thus cause mercury levels in shrimp to rise. species lives, and on which the organisms' survival depends directly or indirectly. It is important to continue to monitor mercury con­ centrations in northern shrimp and its habitat in µg (microgram) : unit of mass, 1 µg = 0.000001 order to ensure the continuing health of fisheries gram. a QH 541.5 .SJ F48 No 2E Maurice Lamontagne Insti .. . Mercury contamination of northern shrimp in the ... 194030 07013416

View of the Cap Trinite in the Saguenay Fjord. ~

BIBLIOGRAPHY fOR MORE INFORMATION ...

ARGUS Groupe-Conseil inc. 1992. Synthese et analyse des For more information on mercury contamination of connaissances relatives aux ressources naturelles du shrimp in the Saguenay Fjord, please refer to the Saguenay et de l'estuaire du Saint-Laurent. Pare marin du bibliography or contact the Communications Saguenay (version finale). Unpublished report submitted Branch of the Maurice Lamontagne Institute at ( 418) to Canadian Parks Service, Quebec Region, 29-20 pages. 775-0526. Cossa, D. 1990 (and cited references). Chemical contami­ nants in the St. Lawrence Estuary and Saguenay Fjord. General Information In: M. El-Sabh et N. Silverberg (eds). Oceanography of a large-scale estuarine system, the St. Lawrence. Coastal Maurice Lamontagne Institute and Estuarine Studies 39: 239-262. Fisheries and Oceans Canada 850 route de la Mer Fortin, G. R. and M. Pelletier. 1995. Synthese des connais­ P.O. Box 1000 sances sur les aspects physiques et chimiques de l'eau Mont-Joli, Quebec et des sediments du Saguenay. Rapport technique. Canada G5H 3Z4 Zones d'intervention prioritaire 22 et 23. Environnement Telephone: (418) 775-0500 Canada-Region du Quebec, Conservation de l'environ­ Fax : ( 418) 775-0542 nement, Centre Saint-Laurent, 212 pages. Egalement disponible en franc;ais Gagnon, M. 1995. Bilan Regional-Secteur du Saguenay. Zones d'intervention prioritaire 22 et 23. Environnement ©Minister of Supply and Services Canada 1996 Canada-Region du Quebec, Conservation de l'environ­ Cat. No. Fs 23-269/1-1996E ISBN 0-662-24407-9 nement, Centre Saint-Laurent, 76 pages. March 1996 Mousseau, P. and A Armellin. 1995. Synthese des con­ naissances sur les communautes biologiques du Saguenay. Rapport technique. Zones d'intervention pri­ Fisheries and Oceans Peches et Oceans oritai re 22 et 23. Environnement Canada-Region du l+I Canada Canada Quebec, Conservation de l'environnement, Centre Saint-Laurent, 246 pages. Science Sciences II