IJEE 2208 Tay et al

Int. J. Environmental Engineering, Vol. x, No. x, xxxx 1

Copyright © 200x Inderscience Enterprises Ltd.

Environmental monitoring of two fish waste ocean disposal sites in Newfoundland and Labrador, Canada

Kok-Leng Tay* Environment Canada, Atlantic Region, 45 Alderney Drive, Dartmouth, Nova Scotia, Canada B2Y 2N6 E-mail: [email protected] *Corresponding author

Glenn Worthman Environment Canada, Atlantic Region, Newfoundland and Labrador District Office, 6 Bruce Street, Mount Pearl, Canada A1N 4T3 E-mail: [email protected]

Rick Wadman Environment Canada, Atlantic Region, Newfoundland and Labrador District Office, 6 Bruce Street, Mount Pearl, Canada A1N 4T3 E-mail: [email protected]

Patrick Stewart Envirosphere Consultants Limited, Unit 5-120 Morison Drive, P.O. Box 2906, Windsor, Nova Scotia, Canada B0N 2T0 E-mail: [email protected]

Abstract: Sediment contaminant and benthic community surveys were conducted at two fish waste ocean disposal sites in Newfoundland and Labrador, Canada, to assess the environmental impacts of the disposal activities. Despite a dispersive ocean environment, fish wastes accumulated at both sites, initially disturbing the benthic community through organic enrichment and oxygen depletion, but causing no elevation of sediment contaminants. After three years without disposal, the benthic community at one of the sites shows signs of recovery from the disturbance.

Keywords: fish wastes; ocean disposal; monitoring; sediment contaminants; benthic community.

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Reference to this paper should be made as follows: Tay, K-L., Worthman, G., Wadman, R. and Stewart, P. (xxxx) ‘Environmental monitoring of two fish waste ocean disposal sites in Newfoundland and Labrador, Canada’, Int. J. Environmental Engineering, Vol. x, No. x, pp.xxx–xxx.

Biographical notes: Kok-Leng Tay obtained his Masters and PhD Degrees from Dalhousie University, Halifax, Nova Scotia, Canada. He is currently working on a special assignment for the Disposal at Sea Program at the Environment Canada’s Atlantic Regional Office. He has worked in the field of sediment environmental assessment for the last 30 years. His research interests include sediment toxicology, biomarkers, benthic community studies and environmental monitoring.

Glenn Worthman obtained his Masters Degree from Memorial University, St. John’s, Newfoundland, Canada. He is currently Head of the Environmental Assessment and Marine Program Unit of the Environment Canada, Atlantic Region District office in Mount Pearl, Newfoundland and Labrador. His responsibilities include the planning and implementation of a multi-disciplinary work unit comprising programs in environmental assessment and disposal at sea in Newfoundland and Labrador.

Rick Wadman had been working for Environment Canada for the last 30 years in a variety of positions, currently as the officer in charge of assessing the acceptability of disposal at sea projects. He is also involved in the promotion and assessment of community funding programs administered by Environment Canada in Newfoundland and Labrador.

Patrick Stewart obtained his Masters Degree in biological oceanography from Dalhousie University, Halifax, Nova Scotia, Canada, focusing on benthic ecology and energetics. In his career, he has worked as a consultant focusing on marine benthic communities, environmental impact assessment, and monitoring, particularly in the evaluation of human impacts on benthic communities resulting from hydrocarbon development and organic enrichment.

1 Introduction

In Canada, disposal of wastes at sea is regulated by a permit system under Part VII of the Canadian Environmental Protection Act (CEPA, 1999). Permit applications are assessed by a waste assessment framework adapted from the London Convention (LC 99) Waste Assessment Guidance (WAG). The framework incorporates pollution prevention and waste management principles and provides guidance for the consideration of all reasonable measures for waste prevention, recycling and reuse before any permit approval for ocean disposals. Under CEPA’ 99, disposal at sea permits are only issued for the following wastes:

• Dredged material

• Fish waste and other organic matter resulting from industrial fish processing operations

• Ships, aircraft, platforms or other man made structures

• Inert, inorganic geological matter

Environmental monitoring of two fish waste ocean disposal sites 3

• Uncontaminated organic matter of natural origin

• Bulky substances.

The majority of wastes permitted for ocean disposal in Canada are dredged materials and inorganic geological matter. Fish wastes amount to only 5–6% of the total quantity of the permitted wastes and the majority of fish waste disposal occurs only in the remote areas of Newfoundland and Labrador where transportation is limited and facilities for recycling and reuse of the wastes are unavailable. In 2006, Environment Canada’s record indicated that 39 permits were issued for the disposal of approximately 60,000 tonnes of fish wastes in Newfoundland and Labrador.

The environmental impacts of fish waste discharges or disposals resulting from industrial fish processing operations and fish farming activities have been studied extensively (Ahumada et al., 2004; Hall-Spencer et al., 2006; Hargrave et al., 2005; Lu and Wu, 1998; Smith et al., 2005; Yorio and Caille, 2004). These studies focused mainly on changes of temperature, dissolved oxygen, ammonium concentration, enrichment of organic matter and surface oil and grease caused by the discharges or disposals resulting from these activities on land, in the coastal zone, or at sea. Smith et al. (2005) did measure Zn, Cu and Pb concentrations in sediment cores collected within the ‘footprint’ of previously abandoned salmon fish farms. However, the aim of the study was to use these heavy metals as indirect tracers of fish farm activities. Peer-reviewed publications on the environmental impacts of disposal of fish wastes on the marine environment at designated ocean disposal sites are rare (Champ et al., 1981).

Since 1985, several surveys have been conducted at selected fish waste disposal sites in Newfoundland to assess sediment contamination and uptake of chemicals in organisms collected at the disposal sites. None of these studies found measurable impacts and the data were not published (Barrie, 1985; Fudge and Associates, 1989; Jacques Whitford, 1996; LGL, 1997; Walsh, 2004). This paper further examines the question of impacts of these activities, through an analysis of monitoring data obtained in 2001 using sediment chemistry and benthic community as effect endpoints from two disposal sites located on the east coast of Newfoundland.

2 Materials and methods

Fish waste disposal sites located on the east coast of Newfoundland, Valleyfield and Aquaforte, were selected for this study based on the criteria that both sites are dispersive sites with less than 25 metres of water depth. The dominant fish wastes disposed at the Valleyfield site are groundfish, pelagic fish and shellfish, while the Aquaforte site is used mainly for shellfish disposal.

From 1990 to 2001 Valleyfield received a total of 27,960 tonnes of fish wastes. The most recent dumping occurred on 2 June, 2001, and the dumping continued until the start of the monitoring program in September 2001. The Aquaforte site received a total of 1,683 tonnes of fish wastes since 1990. The last dumping was in 1999 when 800 tonnes of fish wastes were disposed at the site.

To monitor the disposal activities at the two sites, Environment Canada conducted a diver survey and benthic characterisation study in September, 2001. The diving survey consisted of a visual and photographic reconnaissance by scuba divers at the Valleyfield and Aquaforte disposal sites. A series of photographs were collected to document the

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bottom terrain and identify the boundary of the disposal sites. Additional scuba diving and bottom photography were conducted again in March, 2004 at the disposal sites to further assess accumulation of the fish offal (Narwhal Environmental Consultants Ltd. under contract to Environment Canada (Walsh, 2004)).

Benthic invertebrate community sampling in September 2001 consisted of collection of nine replicate sediment samples by Van Veen grab (0.1 m2) at four locations (the Valleyfield and Aquaforte sites and two corresponding reference sites) (Figure 1). A Garmin Model 12 × L handheld GPS was used for positioning. A subsample of sediment for physical and chemical analyses was obtained from each grab, kept under 6–11°C, and sent on the same day to the Environment Canada’s Environmental Quality Laboratory in Moncton, New Brunswick (for Valleyfield and its reference site, only five subsamples were sent). The remaining sample in each grab was placed in plastic buckets, mixed well, and preserved in 10% buffered formalin, prior to shipment to Envirosphere Consultants Limited in Windsor, Nova Scotia, for benthic macrofaunal sorting and classification.

Figure 1 Sampling locations at (A) Valleyfield disposal and reference sites and (B) Aquaforte disposal and reference sites

(A)

(B)


2.1 Sediment physical and chemical analyses

Grain size analysis was performed by sieve and pipette, following the method recommended by Walton (1978). Total organic carbon was determined by the Leco combustion/infrared method (US EPA, 1995). Analyses of sulphide and ammonia were performed by specific ion electrode (Silver/Sulfide Electrode – ATI Orion 9416BN; Fisher Ammonia Ion Selective Electrode) according to the manufacturer’s instructions following the procedure recommended by the Environment Canada Environmental Quality Laboratory (Environment Canada, 1999).

Sediment heavy metal analysis was performed following the US EPA (1994) methods (US EPA, 1994a, 1994b). PAHs and PCBs were measured by the Environment Canada Atlantic Region Monitoring and Evaluation Branch method (Environment Canada, 1997). Results were reported on a dry weight basis.

2.2 Benthic community sorting and classification

In the laboratory, sediment samples collected for benthic community study were sieved through an 0.5 mm sieve and stored in 70% isopropyl alcohol before sorting and identification. Sorting was carried out under a stereomicroscope at 8x magnification and 10% of the samples were resorted by a second technician to determine sorting efficiency, which was >95%. Samples having large numbers of organisms and large quantities of detritus were subsampled by one-quarter (one sample from Valleyfield and all the Aquaforte samples were subsampled). All large organisms were first removed for later identification, and then the remainder of the sample was placed in a 25 cm diameter circular tray into which a divider was inserted to divide the tray into quarters. The four quarters of the sample were removed manually and kept in separate containers. All ¼ subsamples had more than 200 organisms, a minimum target number for the procedure. The number of organisms in the subsample was multiplied by the subsample factor (4) and the number of organisms initially removed from the sample was added, to give a final estimate of abundance in the sample. Biomass was determined by weighing organisms after blotting to remove surface water. Organisms were identified to the lowest possible taxonomic level, typically to species, using standard taxonomic literature for the area and verified reference material, by one of the authors (PLS, Envirosphere Consultants Limited, an experienced taxonomist). A reference collection containing verified specimens of representative species was retained for future reference.

Community measures determined from the data set included abundance (number/m2), number of species per sample, Shannon-Wiener diversity index, Pielou’s Evenness Index, MacIntosh’s Index, Simpson’s Index, Margalef’s Index (Legendre and Legendre, 1983; Pielou, 1974; Sneath and Sokal, 1973). The Shannon-Wiener index is widely used in ecology and represents both the number of species and distribution among individuals, with higher numbers of species generally resulting in increased values and high values of single species resulting in low diversity measures. Pielou’s evenness index (J') is commonly used to express equitability of distribution of individuals among species. McIntosh's index measures evenness (a measure of whether the species are present in about the same numbers or whether single species dominate). Margalef’s Index measures species richness (number of species per individual) and so is generally higher when more species are present, although it can be reduced for a given number of species if single

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species are present in high abundance. Simpson’s Index measures dominance and is higher when a few species make up a large proportion of the individuals in a sample.

Abundance Biomass Comparison (ABC) curves, a graphic approach which has been used to show benthic community stress (Lambshead et al., 1983; Clarke and Warwick, 1994), were also estimated from the data. Stations were grouped based on similarity of community composition by clustering stations based on the Bray-Curtis similarity index and Multidimensional Scaling (MDS) using the Primer software package (Clarke and Gorley, 2001) to demonstrate differences and similarities between the benthic community composition at the disposal and reference sites.

3 Results and discussion

3.1 Divers observation and sea bed photographs

The Valleyfield disposal site at a depth of 6 to 12 metres received mostly groundfish, pelagic fish, and shellfish wastes. Waste residues, especially shellfish, were clearly visible at the site bottom following the June 2, 2001 dumping; however, areas of significant deposition or waste material accumulation could no longer be found in March 2004, but shell and bone fragments were noted to be thoroughly mixed with bottom sediments. In areas of rocky substrate, shell and bone fragments were observed to be somewhat more abundant in protected areas or depressions among rocks. Some algal growth, frequent large gastropods and occasional crabs were also observed at the site. Sand ridges in water depths greater than 10 metres observed at the site indicates high energy storm events were frequent and significant in this area. The presence of these storm events and the bottom currents generated sufficient energy to transport the disposed fish wastes away from the site.

The average water depth at the Aquaforte disposal site was about 21 metres. The site received shellfish waste almost exclusively. Debris of the waste was not clearly visible at the site and delimiting the boundaries of the disposal site prior to sampling was time consuming. Some crab shell fragments were visibly embedded in the sediments at the site. While the quantity of waste disposed at the site were not large in recent years, the dispersive capability of the site was readily apparent by the minimal amount of debris on the sea floor.

3.2 Sediment physical and chemical characteristics

Sediment samples from the Valleyfield disposal site and the corresponding reference site were mostly sand (63.3–78.8%) and anoxic, containing high levels of ammonia (up to 3,040 mg/Kg) and sulphide (up to 894 mg/Kg). All samples, with the exception of the first two replicates, contained fish wastes, including fish jaws, bones, vertebrae, and scales as well as decapod shell debris. Sediments from the Aquaforte disposal site and its reference site were mostly silty mud (57.4–70.7%) and the levels of ammonia and sulphide were not as high as the Valleyfield site sediments (Table 1).

The mean concentrations of contaminants in sediment samples collected from all the studied sites were lower than the Canadian Disposal at Sea Lower Action Levels (LAL) and the Canadian Interim Sediment Quality Guidelines (ISQG) (Environment Canada, 1995; CCME, 1999). Several cadmium concentrations in the Valleyfield disposal site


samples (0.6–0.8 mg/Kg) and the Aquaforte reference site samples (one sample was 1.3 mg/kg) were slightly higher than the Canadian Disposal at Sea LAL for cadmium (0.6 mg/Kg) (Table 2).

Table 1 Sediment physical characteristic, total organic carbon, NH3 and S

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Table 2 Sediment metals and organic contaminants


3.3 Benthic communities

3.3.1 General

Characteristic species and community measures of benthic communities at the Valleyfield disposal and reference site, and at the Aquaforte disposal and reference site are summarised in Table 3 and Figure 2. The sites supported species known to be common to Newfoundland waters and community measures were comparable to those found at uncontaminated seabed communities at similar depths elsewhere in Atlantic Canada (Stewart et al., 1999). Statistical comparison of community measures for all four sites (Two-way Analysis of Variance) (Table 4), showed significant differences between areas (e.g., between the four sites) in terms of all parameters except number of species; significant differences between treatments (e.g., disposal site vs. reference) for all measures except abundance and biomass (Table 4); and a significant interaction between treatments and areas (indicating the degree of difference between disposal and reference sites was different between areas). Much of the difference between disposal sites and reference was due to large differences between the disposal and reference sites at Valleyfield.

Table 3 Dominant benthic organisms and comparison of community metrics at fish offal disposal sites in Valleyfield and Aquaforte, Newfoundland and Labrador, and associated reference stations. Species indicated in bold are numerically dominant. Unbolded species names indicate other species which were relatively abundant at the site. For crustaceans (a) = amphipod; (c) = cumacean; and (i) = isopod

Valleyfield Aquaforte

Disposal site Reference site Disposal site Reference site

Dominant species

Polychaetes Capitella capitata Chaetozone setosa Capitella capitata Chaetozone setosa

Microphthalmus sp.

Nephtys spp. Ophelina acuminata Nephtys spp.

Chaetozone setosa Phyllodoce mucosa Pholoe sp. Phyllodoce mucosa

Pholoe sp. Pectinaria granulata Pholoe sp.

Prionspio steenstrupi Phyllodoce mucosa Prionspio steenstrupi

Spio filicornis Polydora socialis Spio filicornis

Prionospio steenstrupi

Scoloplos armiger

Spio filicornis

Crustaceans Orchomenella minuta (a)

Caprella sp. (a) Orchomenella minuta (a) Photis reinhardi (a)

Orchomenella pinguis (a)

Photis reinhardi (a) Diastylis sculpta (c)

Photis reinhardi (a) Diastylis sculpta (c)

Phoxocephalus holbolli (a)

Edotea montosa (i)

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Table 3 Dominant benthic organisms and comparison of community metrics at fish offal disposal sites in Valleyfield and Aquaforte, Newfoundland and Labrador, and associated reference stations. Species indicated in bold are numerically dominant. Unbolded species names indicate other species which were relatively abundant at the site. For crustaceans (a) = amphipod; (c) = cumacean; and (i) = isopod (continued)

Valleyfield Aquaforte

Disposal site Reference site Disposal site Reference site

Dominant species

Diastylis sculpta (c)

Molluscs Ensis directus Modiolus modiolus Macoma calcarea Macoma calcarea

Nuculidae

Other Taxa Edwardsia elegans

Relative Status of Selected Community Measures1

Abundance High High High High

Biomass Moderate Moderate to High High2 High

Species Richness Low to Moderate High Moderate to high Moderate to high

Shannon-Wiener diversity

Low High High High

Pielou’s Evenness

Low to moderate Moderate Moderate Moderate

1Compared to levels for uncontaminated seabed communities at similar depths elsewhere in the Canadian Atlantic Region (Stewart et al., 1999). 2High biomass caused by abundance of the bivalve Macoma calcarea.

Figure 2 Benthic communities at the disposal and reference sites: (A) abundance; (B) biomass; (C) Shannon-Wierner Diversity Index; (D) number of species; (E) Simpson’s Index and (F) Propotion of Capitellid Polychaetes species (Capitella capitata and Mediomastus sp.) (see online version for colours)

(A) (B)


Figure 2 Benthic communities at the disposal and reference sites: (A) abundance; (B) biomass; (C) Shannon-Wierner Diversity Index; (D) number of species; (E) Simpson’s Index and (F) Propotion of Capitellid Polychaetes species (Capitella capitata and Mediomastus sp.) (see online version for colours) (continued)

(C) (D)

(E) (F)

Table 4 Biological community measures and the significance of difference (Kruskal Wallace One-way Analysis of Variance) between these measures at the Valleyfield and Aquaforte disposal and reference sites. S.D. = Sample Standard Deviation; p = probability; NS = not significantly different

Abundance number/m2 Biomass grams/m2 Number of

species/sample Shannon-Wiener diversity (log10)

Station Mean S.D. Mean S.D. Mean S.D. Mean S.D

Valleyfield 3062.2 3000.4 39.9 58.1 9 8.3 0.366 0.285 Valleyfield reference 9638.9 6938.1 89.9 153.5 38 12.1 1.125 0.087

Aquaforte 11961.1 4978.6 386.4 182.4 24 4.1 0.951 0.192 Aquaforte reference 9313.3 3843.3 471.0 171.4 23 4.1 0.971 0.034

Valleyfield p < 0.05 NS p < 0.001 p < 0.001 Aquaforte NS NS NS NS

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3.3.2 Comparison of Valleyfield disposal and reference sites

The disposal site at Valleyfield differed in most community measures from the reference site, although the two sites had some species in common. The benthic community at the Valleyfield disposal site had a low evenness and a high Simpson’s Index (Table 5) (Figure 2), illustrating the tendency for few species to be dominant at the station. In contrast the community at the reference site had moderate to high evenness and a low Simpson’s Index, illustrating that no species in particular was dominant (Table 5) (Figure 2). Community measures at the Valleyfield reference site were uniform between replicates, and the presence of seaweed and organisms associated with it in samples contributed to the high diversity and number of species at the station. Abundance, Shannon-Wiener Diversity, and number of species, were all lower at the disposal site, and Simpson’s Index was higher (Kruskal Wallace One-Way Analysis of Variance, Tables 4–5). Fish remains from fish offal were also present in most samples at the disposal site, demonstrating the modified habitat at the site due to the disposal practice. Dominance by the polychaete Capitella capitata and low diversity and numbers of species at the disposal site, suggest that the seabed environment is ‘disturbed’. With the exception of two replicates, Capitella was a dominant in all samples at the Valleyfield disposal site. The species is a member of the family Capitellidae, which can multiply in great numbers (an ‘r-strategist’ or opportunist (MacArthur and Wilson, 1967; Pearson and Rosenberg, 1978)), and is a colonist species, being among the first to occupy environments in which animal communities have been removed by disturbance (e.g., Pocklington and Wells, 1992). Capitellid polychaetes as a proportion of the number of polychaete species were highest at the Valleyfield disposal site (Figure 2). The dominance of Capitella and small number of species (species richness) was reflected in the cumulative percent abundance (dominance) curve of organisms at Valleyfield (Figure 3), showing a rapid initial rise towards 100% abundance. In contrast, the cumulative percent abundance curve for the reference site was more typical of established biological communities which have not experienced disturbance.

Table 5 Biological community measures, Valleyfield and Aquaforte fishery waste disposal and reference sites. S.D. = Sample Standard Deviation

Pielou’s Evenness (J’) McIntosh’s Index Simpson’s Index Margalef’s Index Station Mean S.D. Mean S.D. Mean S.D. Mean S.D.

Valleyfield 0.395 0.213 0.251 0.204 0.634 0.260 1.524 1.230 Valleyfield reference 0.728 0.084 0.694 0.062 0.117 0.031 5.645 1.240

Aquaforte 0.687 0.123 0.588 0.124 0.197 0.121 3.325 0.622 Aquaforte reference 0.721 0.041 0.627 0.020 0.157 0.013 3.213 0.427


Figure 3 Cumulative abundance of the benthic communities at (A) Valleyfield disposal and reference sites and (B) Aquaforte disposal and reference sites (see online version for colours)

(A) (B)

3.3.3 Comparison of Aquaforte disposal and reference sites

Characteristic species and community measures of benthic communities at the Aquaforte disposal and reference site are summarised in Table 3. Community measures were generally uniform among replicates. The community had moderate to high evenness and a low Simpson’s Index (Table 4) illustrating that several species shared dominance. Similarly, the reference site had moderate to high evenness and a low Simpson’s Index (Table 5). Although similar species occurred at both the Aquaforte disposal and reference sites, the disposal site had lower abundance of brittlestars Ophiura sarsi and Ophiura sp., cumaceans (Diastylis sculpta) and ascidians, and elevated abundance of the polychaete Capitella capitata and the amphipod Orchomenella minuta compared to the reference site. None of the community measures, however, differed between disposal and reference sites (Kruskal-Wallace One-Way Analysis of Variance, p < 0.05) (Table 3). Several of the samples at the disposal site where fish waste was observed, showed elevated abundance of Capitellid polychaetes (indicative of disturbance), but the overall number of species was moderate and the fraction made up by them relatively small. The presence of numerous Capitellids in combination with other species, suggested that there may have been some disturbance, but that the other organisms have had a chance to colonize (i.e., the community was in a later stage in succession). Cumulative percent abundance curves (ABC) were similar for the disposal and reference sites at Aquaforte (Figure 3) illustrating the lack of dominance by individual species, in particular Capitellid polychaetes, at both disposal and reference sites.

3.4 Clustering and non-metric Multi-Dimensional Scaling (MDS)

Hierarchical clustering and a non-metric Multi-Dimensional Scaling (MDS) of benthic communities from Valleyfield and Aquaforte disposal and reference sites illustarted the similarities and differences in communities and showed the Valleyfield disposal site to differ significantly from the other samples (Figure 4). Benthic samples V3, 5–9 from the Valleyfield disposal site grouped together, reflected the predominance of the opportunistic polychaete, Capitella capitata, there and not at the other stations (Figure 5).

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C. capitata is commonly found in locations subject to disturbance, in particular associated with high levels of organic loading which leads to anoxic conditions, and tolerates sulfide in sediments (Grassle and Grassle, 1974; Pearson and Rosenberg, 1978; Lu and Wu, 1998). High sediment ammonia and sulphide in sediments at the site reflects reduced oxygen conditions due to decomposition of the fish wastes. Particle size in the sediments at the Aquaforte disposal site was finer than at the reference site, and at both the Valleyfield sites, reflecting a less-dispersive environment and greater potential for developing low-oxygen conditions.

Figure 4 Dendrogram showing similarity of macrobenthic infauna from the Valleyfield, Aquaforte disposal and reference sites (see online version for colours)

Figure 5 Non-metric multi-dimensional scaling of the polychaete species, Capitella capitata, at the Valleyfield disposal site. Bubbles showed present of C. capitata. Number of the organism is represented by the different size of the bubbles (V – disposal site samples; VR – reference site samples) (see online version for colours)


4 Conclusions

This study has shown that despite a dispersive ocean environment, fish wastes deposited on the seabed at two designated ocean disposal sites, accumulated to a degree which initially caused oxygen reduction and organic enrichment of the seabed sufficient to cause a removal of the existing community and its replacement by a community dominated by opportunistic benthic species. The duration of the impact is unknown, but at one of the sites studied, evidence of the defaunation and organic enrichment occurred (shown by diver observations) as much as three years after the fish waste disposal took place. Overall, the benthic communities at the Valleyfield disposal site displayed community measures, patterns of organism dominance, and types of dominant species, that indicate response of the community to environmental disturbance, compared to the reference site. This community dominated by the opportunistic polychaete Capitella capitata differed significantly from the communities found at its reference site and the Aquaforte disposal and reference sites, and reflects organic loading and consequent reduced oxygen conditions leading to a dieoff of existing benthic communities, and later replacement by C. capitata. Although the bottom survey conducted by divers showed that this was a high energy area, fish waste was still found in most of the sediments collected from the site, and its occurrence corresponded to indications of disturbance observed in the biological community; in contrast, replicates which did not contain fish waste appeared more normal in terms of the measures used. Since the concentrations of contaminants were low in the sediments, the disturbance observed in the benthic community was most likely caused by other factors, such as the decomposition of fish wastes. The high levels of sediment ammonia and sulphide at the Valleyfield disposal site were a good indication of this impact.

Seabed biological communities at the Aquaforte disposal site displayed similar communities in terms of species present, community measures, dominance pattern, and types of dominant species, to those of the reference site indicating that the environment at the site was for the most part not disturbed by fish waste disposal. The community at this site was very similar to the communities found at the two reference sites in this study. However some evidence such as the presence of fish waste in one replicate sample and the occurrence of the polychaetes, Capitella capitata, as a dominant species in several replicates at the disposal site, suggested that there were minor effects and that the community at the site may be at a stage in recovery from the disturbance. The fact that the site had not received any disposal of fish wastes for three years before the start of this study may further support the site recovery assumption.

Acknowledgement

The authors would like to acknowledge the support of the Environment Canada Disposal at Sea Program Research Funds.

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