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Benthic marine debris in the Bay of Fundy, eastern Canada: Spatial distribution and categorization using seafloor video footage
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Baseline
Benthic marine debris in the Bay of Fundy, eastern Canada: Spatial distribution and categorization using seafloor video footage Alexa J. Goodmana,b,d, , Tony R. Walkerb, Craig J. Brownc,d, Brittany R. Wilsond, Vicki Gazzolad, Jessica A. Sameotoe ⁎
a
Marine Affairs Program, Dalhousie University, Halifax, Canada School for Resource and Environmental Studies, Dalhousie University, Halifax, Canada c Department of Oceanography, Dalhousie University, Halifax, Canada d Applied Research, Ivany Campus, Nova Scotia Community College, Dartmouth, Canada e Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Canada b
ARTICLE INFO
ABSTRACT
Keywords: Benthic marine debris Abandoned, lost, discarded fishing gear Bay of Fundy (BoF) Seafloor video Plastic pollution
Marine debris, particularly plastic and abandoned, lost and discarded fishing gear, is ubiquitous in marine environments. This study provides the first quantitative and qualitative assessment of benthic debris using seafloor video collected from a drop camera system in the Bay of Fundy, Eastern Canada. An estimated 137 debris items km−2 of seafloor were counted, comprising of plastic (51%), fishing gear (including plastic categories; 28%) and other (cable, metal, tires; 21%). Debris was widespread, but mainly located nearshore (within 9 km) and on the periphery of areas with high fishing intensity. This baseline benthic marine debris characterization and estimate of abundance provides valuable information for government (municipal, provincial and federal) and for other stakeholders to implement management strategies to reduce plastic and other categories of benthic marine pollution at source. Strategies may include limiting plastic use and reducing illegal dumping through improved education among fishers.
Marine debris, mainly comprised of single-use plastics and abandoned, lost and discarded (ALD) fishing gear, is a pervasive global issue threatening the health of marine ecosystems (Macfadyen et al., 2009; Walker, 2018; Avery-Gomm et al., 2019). Sources of marine debris pollution are widespread, with inputs from a wide range of terrestrial and marine sources (e.g., fishing industry, shipping and tourism) (Galgani et al., 2015). Although most studies report between 80 and 90% of marine debris originate from land-based sources (Walker et al., 2006; Ambrose et al., 2019), marine areas subject to intense fishing activity have been subject to large quantities of fishing related debris (Walker et al., 1997). Plastic fragments pose hazards to fish, seabirds and marine mammals as ingestion can be lethal (Wilcox et al., 2016; Worm et al., 2017). ALD fishing gear poses entanglement risks to marine life and ALD traps and lines can smother or damage seafloor habitat though physical abrasion (Barnette, 2001; Macfadyen et al., 2009). With the discovery of a plastic bag on the Mariana's Trench seafloor, the deepest part of the ocean in 1998 and again in 2019, there is growing evidence that the benthic zone is a sink for marine debris (Galgani et al., 2000; Angiolillo et al., 2015; Chiba et al., 2018; Morelle, 2019). Shoreline cleanup data
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has helped quantify marine debris from coastal ecosystems and scientific studies have documented impacts of plastic debris and ALD gear on marine life, resulting in increasing international policies to reduce marine debris and single-use plastics (Worm et al., 2017; Xanthos and Walker, 2017; Schnurr et al., 2018; Goodman et al., 2019). Although research has been conducted to quantify and assess impacts of benthic marine debris in Europe using trawls (Galgani et al., 2000), remotely operated underwater vehicles (ROVs) (Angiolillo et al., 2015; Melli et al., 2017) and submersibles in California (Watters et al., 2010), there has been limited research conducted in Canadian waters. The Bay of Fundy (BoF), located in Eastern Canada between New Brunswick and Nova Scotia, is a highly dynamic and productive embayment with a maximum tidal range of 16 m, supporting many industries, including shipping, aquaculture and commercial fisheries (Graham et al., 2002). Several areas of the BoF have been designated by federal Fisheries and Oceans Canada (DFO) as Ecologically and Biologically Significant Areas, supporting finfish (groundfish, mackerel), diadromous (eel, gaspereau), and shellfish (lobster, scallop, mussels) fisheries, valued at $3.4 billion CAD for the entire Maritimes ScotiaFundy Region in 2017, which covers the northern tip of Cape Breton to
Corresponding author at: Marine Affairs Program, 6100 University Avenue, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. E-mail address: [email protected] (A.J. Goodman).
https://doi.org/10.1016/j.marpolbul.2019.110722 Received 12 September 2019; Received in revised form 31 October 2019; Accepted 6 November 2019 Available online 14 November 2019 0025-326X/ © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Please cite this article as: Alexa J. Goodman, et al., Marine Pollution Bulletin, https://doi.org/10.1016/j.marpolbul.2019.110722
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Fig. 1. Total seafloor video footage stations (n = 281) in the Bay of Fundy. Footage was collected throughout April, June, October and December 2017; July and August 2018; and July 2019. Locations of observed debris, categorized by type, are shown. Station locations where no debris was observed are included to indicate geographical distribution of camera stations.
the New Brunswick-Maine border (Fisheries and Oceans Canada, 2019; Fisheries and Oceans Canada, 2018) suggesting that integrated management across multiple industries is needed to ensure their protection (Buzeta, 2014; Barnett et al., 2016). Studies have shown that coastal marine debris is numerous and problematic in the area from competing stakeholders (Barnett et al., 2016; Goodman et al., 2019), suggesting that benthic debris and areas of accumulation are likely (Martens and Huntington, 2012). To assess the extent and magnitude of the problem caused by benthic marine debris in the region and to develop mitigation strategies, baseline information is required on the type, quantity and distribution of debris accumulating on the seabed. This baseline study quantitatively and qualitatively assessed benthic marine debris in the BoF using seafloor video footage, categorizing observed items into broad types (i.e., plastic, fishing and other debris), and evaluated patterns of distribution against bathymetry, substrate, bottom current and fishing effort. Fishing debris items comprised traps, bait bags, rope and gloves, other debris includes cables, metal and tires. This study offers the first evaluation of the type and quantity of benthic debris in the region, providing an insight into the magnitude of the problem in Eastern Canadian waters. Underwater video surveys using a passive drop camera system were conducted in the BoF as part of a wider seafloor habitat mapping study. Video stations were selected based on existing multibeam echosounder data (bathymetry and backscatter) to validate seafloor habitat characteristics within the region. The drop camera system comprised a protective drop-frame onto which were mounted four high-powered LED lights and a 4 k Panasonic GH4 ultra-high definition (UHD) camera housed in a subsea pressure housing with two scaling lasers 10 cm apart. The frame was lowered from the stern of the FV Brittany and Madison VI, a fishing vessel charted for the surveys, to approximately 1–2 m above the seafloor. The vessel was then allowed to drift for 5–15 min. (mean duration of each transect was 8 min.) as the camera
system recorded footage of the seafloor. High definition (1080p) video was transmitted through a subsea cable to the surface for real-time viewing to allow camera elevation above the seafloor to be adjusted, and to assess image quality. UHD footage was recoded directly on the camera for detailed evaluation of seafloor characteristics and identification of debris following the surveys. GPS position of the camera was recorded based on vessel position during each camera deployment. Horizontal positional accuracy was estimated at ± 16 m and was calculated by matching discrete boundaries of substrate changes on both the video and multibeam echosounder backscatter data (at 5 m resolution) and measuring the distance between the two points. Drift transects were taken at 281 different locations in the BoF (Fig. 1). A total of 146 camera stations were observed in 2017 completed over 14 days throughout April, June, October and December. An additional 120 stations were observed in 2018 over 10 days throughout July and August, and 15 stations over 2 days in July 2019. The combined data from these stations totaled 33 h of 4 k seafloor video footage. Seafloor footage was reviewed manually, and observed debris was categorized as fishing gear (e.g., rope, traps and bait bags), plastic (e.g., bags) and other (e.g., metal and tires). GPS location of each identified item of debris was determined by matching the time stamp of the video with the GPS data. Seafloor substrate for each transect was also described based on the Wentworth grain size classification (Wentworth, 1922). To assess impacts of the marine debris on the surrounding environment, additional information was recorded on visible impact to benthos, biofouling attached to the debris (as an indicator of length of time in situ), and visible evidence of ghost fishing. Locations of observed debris were compared in ArcGIS Pro with other geospatial information, including bathymetry, backscatter as an indication of seafloor surficial geology (Brown et al., 2019) extracted from available multibeam sonar data, fishing intensity (Fisheries and Oceans Canada, 2018; Koen-Alonso et al., 2018), and seafloor current strength (mean shear velocity) (Li et al., 2015) (Fig. 2). To determine 2
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Fig. 2. Seafloor variables overlaid with debris observations: A indicates bathymetry; B indicates backscatter; C indicates fishing effort (information from Fisheries and Oceans Canada, 2018); and D indicates bottom current from wave sheer velocity (Li et al., 2015).
the area of seafloor observed by the camera system, 10 images were extracted from each transect with a distance of 10 m between each image. Extracted frames were scaled using the lasers (10 cm apart) and the width of each frame was measured in Image J - Fiji (Schindelin et al., 2012) to obtain a maximum, minimum and mean field of view (dependent on height of the camera frame above the seafloor). Using the combined length of all transects and average estimated field of view, a swept area of observed seafloor was estimated using ArcGIS Pro. From the swept area, 47 items of debris were observed from 26 stations (Fig. 3). If upscaled to cover the entire BoF (13,453 km2), then there is potentially 1.8 million pieces of litter in existence on the BoF seafloor (i.e., 137 items km−2) (Table 1). Plastic comprised 51% of the litter, fishing gear 28% and 21% other man-made materials (Table 2).
Debris composition are comparable with other studies, which noted plastic and fishing gear as dominant debris sources (Watters et al., 2010; Angiolillo et al., 2015; Maes et al., 2018; Gerigny et al., 2019). In NW Europe, plastic bags are a significant source of seafloor debris (Maes et al., 2018), which aligns with observations in this study as the most numerous items. Mean debris density in the BoF was comparable to the Celtic Sea (24.2 items km−2 inshore and 21.9 items km−2 offshore) and the Greater North Sea (49.1 items km−2 inshore and 40.5 items km−2 offshore) in NW Europe (Maes et al., 2018), and to the continental shelves and canyons in French Mediterranean waters with densities range from 49.63 to 289.01 items km−2 (Gerigny et al., 2019). In comparison to the NW Mediterranean Sea (0.12 items m−2 or roughly 3
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Fig. 3. Observed debris from the Bay of Fundy seafloor video footage. Images show: A - blue lobster band; B - tire with barnacle growth; C - partially buried blue plastic bag, D - lobster trap rope bait bag; and E - blue fishing rope. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Table 1 Debris density per km−2 estimated from total swept area.
Maximum Mean Minimum
Video field of view (m)
Estimated area of seafloor viewed from all camera stations (km2)
Estimated density of debris (km−2)
2.50 1.55 1.06
0.549 0.342 0.235
86 137 200
Table 2 Benthic debris occurrence categorized by fishing gear (28%), plastic (51%) or other (21%). Debris Type Fishing Gear⁎
Plastic Other Total ⁎
Rope Lobster Traps Bait Bags Gloves Other Bags Other Cables Metal Tires
Table 3 Benthic debris occurrence and proportion on observed Bay of Fundy substrate types.
Occurrence
Substrate Type
Occurrence
Proportion (%)
4 3 1 3 2 17 7 5 4 1 47
Mud Cobble and Mud Fine Sand Fine Sand and Gravel Sand Sand and Gravel Sand, Gravel and Shell Gravel Cobble and Gravel Boulders and Fine Sand Total
1 1 5 2 19 9 2 1 6 1 47
2.1 2.1 10.6 4.3 40.4 19.1 4.3 2.1 12.9 2.1 100.0
Note: Fishing gear also comprises various plastic categories.
and gives relative abundances for each transect. That study does not use total swept area across all transects, therefore making comparisons to the overall abundance in the BoF challenging. To illustrate that the BoF is several magnitudes lower, the hotspot identified at station 413 had 13 items per 1000 m2, making 0.013 items m−2, a value comparable to the 0.12 items m−2 from the NW Mediterranean. On average, most debris items were observed within 9 km from
120,000 items km−2, Angiolillo et al., 2015) the abundance in the BoF is several orders of magnitude lower. The discrepancy between the BoF and the NW Mediterranean Sea could presumably be due to huge differences in population density and differences in tidal flushing between the two regions. However, the relative abundance in the NW Mediterranean (Angiolillo et al., 2015) was only recorded for single stations 4
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Fig. 4. Derelict lobster trap found in the Bay of Fundy at station 17, with a moon snail (Euspira heros) shell located underneath a bent portion of the trap.
shore. The mid-bay debris observations on the periphery of fishing areas were exclusively fishing related debris. Although, there were no strong patterns in the spatial distribution relative to fishing pressure, the distribution may be due to strong bottom currents, generally > 0.5 cm s−1, in the BoF (Li et al., 2015). Additionally, there were two areas with multiple debris observations (Digby ferry terminal area and off Gardner Creek) which can be considered hot spots (Gerigny et al., 2019). One station had 12 garbage bags which were partially buried in sand (Gardner Creek) and the other was mixed debris, which may indicate dumping grounds. The area around the Digby ferry tract - informally called ‘the Dump’ between Digby Neck and Victoria Beach, was identified by fishers as a dumping hot spot (Goodman et al., 2019). Hot spots have also been identified in the French Mediterranean (Gerigny et al., 2019) and areas with higher than average debris densities in NW Europe (Maes et al., 2018). Debris was detected on sand (40.4%), mixed cobble and gravel (12.8%), fine sand (10.6%) and mixed sand and gravel (19.1%) (Table 3). This contrasts to results from the literature which suggest that harder/coarser benthic environments serve as dominant substrates for debris accumulation (Watters et al., 2010; Melli et al., 2017). This variation may be attributed to the unique benthic environment, sediment transportation and bottom currents in the BoF region, and because fewer stations were sampled on harder/coarser vs. softer/finer sediment bottoms (Li et al., 2015; Fig. 2). High turbidity from sedimentation, high current speeds (e.g., 3 kts), and surface wave action (> 1 m) may have contributed to underestimates of debris items and subsequent characterization using seafloor video collected by the drop camera system. For example, items < 10 cm could be detected from transects where survey conditions were optimal (i.e., slack current, low turbidity and a consistent 1 m height off the seafloor). For transects with higher drift speeds, lower visibility and high wave action, items < 10 cm may have gone undetected. However, we did not evaluate stations by tidal flow. Colour of debris and seafloor may have also posed detection limitations. Shell fragments and debris may have been indistinguishable from each other if litter was white, and non-uniformly colored substrata, such as rocks, may camouflage debris better than uniformly colored substrata such as sand, alluding to better detectability over sandy substrate types. However, some debris may become buried by sediment if settled on the seafloor for extended periods, reducing detectability. There were no observed incidences of ghost fishing, although one derelict lobster trap had shown seafloor abrasion and contained a moon
snail (Euspira heros) shell (Fig. 4). All other debris were either laying on or fixed to the seafloor with no visible impact to the benthic environment. This contrasts from the literature which shows direct links between debris and benthic habitat destruction (Angiolillo et al., 2015; Melli et al., 2017). There was limited biofouling on some debris (57%), while others (22%) showed moderate fouling with barnacles and light algal growth. Based on these findings, seafloor debris in the BoF is numerous and widespread, regardless of parameters used for comparisons. Quantities of debris stranded on the seafloor in the BoF and elsewhere remain problematic, because plastic debris continues to fragment into secondary microplastics, where long-term exposure at environmentally relevant concentration levels can negatively impact benthic biota (Bour et al., 2018; Karbalaei et al., 2018). Although, seafloor marine debris often goes unnoticed as it is out of sight, it is important to limit sources of marine debris pollution (Pettipas et al., 2016). In terms of future solutions, marine debris retrieval efforts in the BoF are unrealistic due to the highly dynamic nature of the marine environment. Implementation and enforcement of policies to eliminate single-use plastic items (e.g., Xanthos and Walker, 2017; Schnurr et al., 2018; Prata et al., 2019) and to improve education among fishers to reduce illegal dumping of fishing gear and related waste (Goodman et al., 2019) is recommended. This research highlights point source pollution from the fishing industry, providing empirical data to better monitor and manage waste associated with the industry. Some fishers' have mixed perceptions and understandings of their environmental impact on the marine environment. This creates barriers to limiting illegal disposal atsea, which needs to be addressed in the future by improving education to limit illegal disposal at-sea (Goodman et al., 2019). Given that Canada recently signed on to the Ocean Plastics Charter and to the Global Ghost Gear Initiative, both in 2018 (G7, 2018; Global Affairs Canada, 2018; Karbalaei et al., 2018), there is a growing sense of urgency to move forward with these commitments to improve land and oceanbased waste management. Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Acknowledgments
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This study was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), Grant/Award Number: RGPIN2018-04119 to Tony R. Walker, and the NSERC Industrial Research Chair for Colleges grant CIRC 472115-14, NSERC Engage grant 50220016 in partnership with the Full Bay Scallop Association and Fisheries and Oceans Canada grants MECTS-#3674626 and MECTS-#3802469 to Craig J. Brown. Special thanks to Larissa Pattison from the Applied Oceans Research Group at NSCC for analysis support. References Ambrose, K.K., Box, C., Boxall, J., Brooks, A., Eriksen, M., Fabres, J., Fylakis, G., Walker, T.R., 2019. Spatial trends and drivers of marine debris accumulation on shorelines in South Eleuthera, the Bahamas using citizen science. Mar. Pollut. Bull. 142, 145–154. Angiolillo, M., Lorenzo, B.D., Farcomeni, A., Bo, M., Bavestrello, G., Santangelo, G., … Canese, S. 2015. Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy). Mar. Pollut. Bull., 92(1–2), 149–159. doi: https:// doi.org/10.1016/j.marpolbul.2014.12.044. Avery-Gomm, S., Walker, T.R., Mallory, M.L., Provencher, J.F., 2019. There is nothing convenient about plastic pollution. Rejoinder to Stafford and Jones “Viewpoint–Ocean plastic pollution: a convenient but distracting truth?”. Mar. Policy 106, 103552. Barnett, A.J., Wiber, M.G., Rooney, M.P., Maillet, D.G., 2016. The role of public participation GIS (PPGIS) and fishermens perceptions of risk in marine debris mitigation in the Bay of Fundy, Canada. Ocean Coast. Manag. 133, 85–94. https://doi.org/10. 1016/j.ocecoaman.2016.09.002. Barnette, M.C., 2001. Effects of litter from fishing gear. In: Commercial Fishing: The Wider Ecological Impacts, NMFS-SEFSC-449, pp. 28–29. Bour, A., Haarr, A., Keiter, S., Hylland, K., 2018. Environmentally relevant microplastic exposure affects sediment-dwelling bivalves. Environ. Pollut. 236, 652–660. https:// doi.org/10.1016/j.envpol.2018.02.006. Brown, C.J., Beaudoin, J., Brissette, M., Gazzola, V., 2019. Multispectral multibeam echo sounder backscatter as a tool for improved seafloor characterization. Geosci. Can. 9 (3), 126. https://doi.org/10.3390/geosciences9030126. Buzeta, M.I., 2014. Identification and review of ecologically and biologically significant areas in the Bay of Fundy. DFO Can. Sci. Advis. Sec. Res. Doc 2013/065. vi + 59 p. Chiba, S., Saito, H., Fletcher, R., Yogi, T., Kayo, M., Miyagi, S., ... Fujikura, K., 2018. Human footprint in the abyss: 30 year records of deep-sea plastic debris. Mar. Policy 96, 204–212. https://doi.org/10.1016/j.marpol.2018.03.022. Fisheries and Oceans Canada, 2018. Fishing effort within Significant Benthic Areas in Canada's Atlantic and Eastern Arctic marine waters. Record ID: 273df20a-47ae-42c0bc58-01e451d4897a. [dataset]. Retrieved from. https://open.canada.ca/data/en/ dataset/273df20a-47ae-42c0-bc58-01e451d4897a. Fisheries and Oceans Canada, 2019. Canada's fisheries fast facts. Retrieved from. http:// www.dfo-mpo.gc.ca/stats/facts-Info-17-eng.htm 2018. G7, 2019. Ocean Plastics Charter. pp. 2–4. Retreived from. http://publications.gc.ca/ collections/collection_2018/amc-gac/FR5-144-2018-32-eng.pdf 2018. Galgani, F., Leaute, J., Moguedet, P., Souplet, A., Verin, Y., Carpentier, A., … Nerisson, P. 2000. Litter on the sea floor along European coasts. Mar. Pollut. Bull., 40(6), 516–527. doi: https://doi.org/10.1016/s0025-326x(99)00234-9. Galgani, F., Hanke, G., Maes, T., 2015. Global distribution, composition and abundance of marine litter. Mar. Anthro. Lit. 29–56. https://doi.org/10.1007/978-3-319-165103_2. Gerigny, O., Brun, M., Fabri, M., Tomasino, C., Moigne, M.L., Jadaud, A., Galgani, F., 2019. Seafloor litter from the continental shelf and canyons in French Mediterranean water: distribution, typologies and trends. Mar. Pollut. Bull. 146, 653–666. https:// doi.org/10.1016/j.marpolbul.2019.07.030. Global Affairs Canada, 2018. Environment, oceans and energy ministers ready to take action on our oceans and seas; conclude G7 joint meeting on healthy oceans, seas and resilient coastal communities. Retrieved from. https://www.canada.ca/en/globalaffairs/news/2018/09/environment-oceans-and-energy-ministers-ready-to-takeaction-on-our-oceans-and-seas-conclude-g7-joint-meeting-on-healthy-oceans-seasand-resilient-.html. Goodman, A.J., Brillant, S., Walker, T.R., Bailey, M., Callaghan, C., 2019. A ghostly issue: managing abandoned, lost and discarded lobster fishing gear in the Bay of Fundy in
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Baseline
Benthic marine debris in the Bay of Fundy, eastern Canada: Spatial distribution and categorization using seafloor video footage Alexa J. Goodmana,b,d, , Tony R. Walkerb, Craig J. Brownc,d, Brittany R. Wilsond, Vicki Gazzolad, Jessica A. Sameotoe ⁎
a
Marine Affairs Program, Dalhousie University, Halifax, Canada School for Resource and Environmental Studies, Dalhousie University, Halifax, Canada c Department of Oceanography, Dalhousie University, Halifax, Canada d Applied Research, Ivany Campus, Nova Scotia Community College, Dartmouth, Canada e Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Canada b
ARTICLE INFO
ABSTRACT
Keywords: Benthic marine debris Abandoned, lost, discarded fishing gear Bay of Fundy (BoF) Seafloor video Plastic pollution
Marine debris, particularly plastic and abandoned, lost and discarded fishing gear, is ubiquitous in marine environments. This study provides the first quantitative and qualitative assessment of benthic debris using seafloor video collected from a drop camera system in the Bay of Fundy, Eastern Canada. An estimated 137 debris items km−2 of seafloor were counted, comprising of plastic (51%), fishing gear (including plastic categories; 28%) and other (cable, metal, tires; 21%). Debris was widespread, but mainly located nearshore (within 9 km) and on the periphery of areas with high fishing intensity. This baseline benthic marine debris characterization and estimate of abundance provides valuable information for government (municipal, provincial and federal) and for other stakeholders to implement management strategies to reduce plastic and other categories of benthic marine pollution at source. Strategies may include limiting plastic use and reducing illegal dumping through improved education among fishers.
Marine debris, mainly comprised of single-use plastics and abandoned, lost and discarded (ALD) fishing gear, is a pervasive global issue threatening the health of marine ecosystems (Macfadyen et al., 2009; Walker, 2018; Avery-Gomm et al., 2019). Sources of marine debris pollution are widespread, with inputs from a wide range of terrestrial and marine sources (e.g., fishing industry, shipping and tourism) (Galgani et al., 2015). Although most studies report between 80 and 90% of marine debris originate from land-based sources (Walker et al., 2006; Ambrose et al., 2019), marine areas subject to intense fishing activity have been subject to large quantities of fishing related debris (Walker et al., 1997). Plastic fragments pose hazards to fish, seabirds and marine mammals as ingestion can be lethal (Wilcox et al., 2016; Worm et al., 2017). ALD fishing gear poses entanglement risks to marine life and ALD traps and lines can smother or damage seafloor habitat though physical abrasion (Barnette, 2001; Macfadyen et al., 2009). With the discovery of a plastic bag on the Mariana's Trench seafloor, the deepest part of the ocean in 1998 and again in 2019, there is growing evidence that the benthic zone is a sink for marine debris (Galgani et al., 2000; Angiolillo et al., 2015; Chiba et al., 2018; Morelle, 2019). Shoreline cleanup data
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has helped quantify marine debris from coastal ecosystems and scientific studies have documented impacts of plastic debris and ALD gear on marine life, resulting in increasing international policies to reduce marine debris and single-use plastics (Worm et al., 2017; Xanthos and Walker, 2017; Schnurr et al., 2018; Goodman et al., 2019). Although research has been conducted to quantify and assess impacts of benthic marine debris in Europe using trawls (Galgani et al., 2000), remotely operated underwater vehicles (ROVs) (Angiolillo et al., 2015; Melli et al., 2017) and submersibles in California (Watters et al., 2010), there has been limited research conducted in Canadian waters. The Bay of Fundy (BoF), located in Eastern Canada between New Brunswick and Nova Scotia, is a highly dynamic and productive embayment with a maximum tidal range of 16 m, supporting many industries, including shipping, aquaculture and commercial fisheries (Graham et al., 2002). Several areas of the BoF have been designated by federal Fisheries and Oceans Canada (DFO) as Ecologically and Biologically Significant Areas, supporting finfish (groundfish, mackerel), diadromous (eel, gaspereau), and shellfish (lobster, scallop, mussels) fisheries, valued at $3.4 billion CAD for the entire Maritimes ScotiaFundy Region in 2017, which covers the northern tip of Cape Breton to
Corresponding author at: Marine Affairs Program, 6100 University Avenue, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. E-mail address: [email protected] (A.J. Goodman).
https://doi.org/10.1016/j.marpolbul.2019.110722 Received 12 September 2019; Received in revised form 31 October 2019; Accepted 6 November 2019 Available online 14 November 2019 0025-326X/ © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Please cite this article as: Alexa J. Goodman, et al., Marine Pollution Bulletin, https://doi.org/10.1016/j.marpolbul.2019.110722
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Fig. 1. Total seafloor video footage stations (n = 281) in the Bay of Fundy. Footage was collected throughout April, June, October and December 2017; July and August 2018; and July 2019. Locations of observed debris, categorized by type, are shown. Station locations where no debris was observed are included to indicate geographical distribution of camera stations.
the New Brunswick-Maine border (Fisheries and Oceans Canada, 2019; Fisheries and Oceans Canada, 2018) suggesting that integrated management across multiple industries is needed to ensure their protection (Buzeta, 2014; Barnett et al., 2016). Studies have shown that coastal marine debris is numerous and problematic in the area from competing stakeholders (Barnett et al., 2016; Goodman et al., 2019), suggesting that benthic debris and areas of accumulation are likely (Martens and Huntington, 2012). To assess the extent and magnitude of the problem caused by benthic marine debris in the region and to develop mitigation strategies, baseline information is required on the type, quantity and distribution of debris accumulating on the seabed. This baseline study quantitatively and qualitatively assessed benthic marine debris in the BoF using seafloor video footage, categorizing observed items into broad types (i.e., plastic, fishing and other debris), and evaluated patterns of distribution against bathymetry, substrate, bottom current and fishing effort. Fishing debris items comprised traps, bait bags, rope and gloves, other debris includes cables, metal and tires. This study offers the first evaluation of the type and quantity of benthic debris in the region, providing an insight into the magnitude of the problem in Eastern Canadian waters. Underwater video surveys using a passive drop camera system were conducted in the BoF as part of a wider seafloor habitat mapping study. Video stations were selected based on existing multibeam echosounder data (bathymetry and backscatter) to validate seafloor habitat characteristics within the region. The drop camera system comprised a protective drop-frame onto which were mounted four high-powered LED lights and a 4 k Panasonic GH4 ultra-high definition (UHD) camera housed in a subsea pressure housing with two scaling lasers 10 cm apart. The frame was lowered from the stern of the FV Brittany and Madison VI, a fishing vessel charted for the surveys, to approximately 1–2 m above the seafloor. The vessel was then allowed to drift for 5–15 min. (mean duration of each transect was 8 min.) as the camera
system recorded footage of the seafloor. High definition (1080p) video was transmitted through a subsea cable to the surface for real-time viewing to allow camera elevation above the seafloor to be adjusted, and to assess image quality. UHD footage was recoded directly on the camera for detailed evaluation of seafloor characteristics and identification of debris following the surveys. GPS position of the camera was recorded based on vessel position during each camera deployment. Horizontal positional accuracy was estimated at ± 16 m and was calculated by matching discrete boundaries of substrate changes on both the video and multibeam echosounder backscatter data (at 5 m resolution) and measuring the distance between the two points. Drift transects were taken at 281 different locations in the BoF (Fig. 1). A total of 146 camera stations were observed in 2017 completed over 14 days throughout April, June, October and December. An additional 120 stations were observed in 2018 over 10 days throughout July and August, and 15 stations over 2 days in July 2019. The combined data from these stations totaled 33 h of 4 k seafloor video footage. Seafloor footage was reviewed manually, and observed debris was categorized as fishing gear (e.g., rope, traps and bait bags), plastic (e.g., bags) and other (e.g., metal and tires). GPS location of each identified item of debris was determined by matching the time stamp of the video with the GPS data. Seafloor substrate for each transect was also described based on the Wentworth grain size classification (Wentworth, 1922). To assess impacts of the marine debris on the surrounding environment, additional information was recorded on visible impact to benthos, biofouling attached to the debris (as an indicator of length of time in situ), and visible evidence of ghost fishing. Locations of observed debris were compared in ArcGIS Pro with other geospatial information, including bathymetry, backscatter as an indication of seafloor surficial geology (Brown et al., 2019) extracted from available multibeam sonar data, fishing intensity (Fisheries and Oceans Canada, 2018; Koen-Alonso et al., 2018), and seafloor current strength (mean shear velocity) (Li et al., 2015) (Fig. 2). To determine 2
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Fig. 2. Seafloor variables overlaid with debris observations: A indicates bathymetry; B indicates backscatter; C indicates fishing effort (information from Fisheries and Oceans Canada, 2018); and D indicates bottom current from wave sheer velocity (Li et al., 2015).
the area of seafloor observed by the camera system, 10 images were extracted from each transect with a distance of 10 m between each image. Extracted frames were scaled using the lasers (10 cm apart) and the width of each frame was measured in Image J - Fiji (Schindelin et al., 2012) to obtain a maximum, minimum and mean field of view (dependent on height of the camera frame above the seafloor). Using the combined length of all transects and average estimated field of view, a swept area of observed seafloor was estimated using ArcGIS Pro. From the swept area, 47 items of debris were observed from 26 stations (Fig. 3). If upscaled to cover the entire BoF (13,453 km2), then there is potentially 1.8 million pieces of litter in existence on the BoF seafloor (i.e., 137 items km−2) (Table 1). Plastic comprised 51% of the litter, fishing gear 28% and 21% other man-made materials (Table 2).
Debris composition are comparable with other studies, which noted plastic and fishing gear as dominant debris sources (Watters et al., 2010; Angiolillo et al., 2015; Maes et al., 2018; Gerigny et al., 2019). In NW Europe, plastic bags are a significant source of seafloor debris (Maes et al., 2018), which aligns with observations in this study as the most numerous items. Mean debris density in the BoF was comparable to the Celtic Sea (24.2 items km−2 inshore and 21.9 items km−2 offshore) and the Greater North Sea (49.1 items km−2 inshore and 40.5 items km−2 offshore) in NW Europe (Maes et al., 2018), and to the continental shelves and canyons in French Mediterranean waters with densities range from 49.63 to 289.01 items km−2 (Gerigny et al., 2019). In comparison to the NW Mediterranean Sea (0.12 items m−2 or roughly 3
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Fig. 3. Observed debris from the Bay of Fundy seafloor video footage. Images show: A - blue lobster band; B - tire with barnacle growth; C - partially buried blue plastic bag, D - lobster trap rope bait bag; and E - blue fishing rope. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Table 1 Debris density per km−2 estimated from total swept area.
Maximum Mean Minimum
Video field of view (m)
Estimated area of seafloor viewed from all camera stations (km2)
Estimated density of debris (km−2)
2.50 1.55 1.06
0.549 0.342 0.235
86 137 200
Table 2 Benthic debris occurrence categorized by fishing gear (28%), plastic (51%) or other (21%). Debris Type Fishing Gear⁎
Plastic Other Total ⁎
Rope Lobster Traps Bait Bags Gloves Other Bags Other Cables Metal Tires
Table 3 Benthic debris occurrence and proportion on observed Bay of Fundy substrate types.
Occurrence
Substrate Type
Occurrence
Proportion (%)
4 3 1 3 2 17 7 5 4 1 47
Mud Cobble and Mud Fine Sand Fine Sand and Gravel Sand Sand and Gravel Sand, Gravel and Shell Gravel Cobble and Gravel Boulders and Fine Sand Total
1 1 5 2 19 9 2 1 6 1 47
2.1 2.1 10.6 4.3 40.4 19.1 4.3 2.1 12.9 2.1 100.0
Note: Fishing gear also comprises various plastic categories.
and gives relative abundances for each transect. That study does not use total swept area across all transects, therefore making comparisons to the overall abundance in the BoF challenging. To illustrate that the BoF is several magnitudes lower, the hotspot identified at station 413 had 13 items per 1000 m2, making 0.013 items m−2, a value comparable to the 0.12 items m−2 from the NW Mediterranean. On average, most debris items were observed within 9 km from
120,000 items km−2, Angiolillo et al., 2015) the abundance in the BoF is several orders of magnitude lower. The discrepancy between the BoF and the NW Mediterranean Sea could presumably be due to huge differences in population density and differences in tidal flushing between the two regions. However, the relative abundance in the NW Mediterranean (Angiolillo et al., 2015) was only recorded for single stations 4
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Fig. 4. Derelict lobster trap found in the Bay of Fundy at station 17, with a moon snail (Euspira heros) shell located underneath a bent portion of the trap.
shore. The mid-bay debris observations on the periphery of fishing areas were exclusively fishing related debris. Although, there were no strong patterns in the spatial distribution relative to fishing pressure, the distribution may be due to strong bottom currents, generally > 0.5 cm s−1, in the BoF (Li et al., 2015). Additionally, there were two areas with multiple debris observations (Digby ferry terminal area and off Gardner Creek) which can be considered hot spots (Gerigny et al., 2019). One station had 12 garbage bags which were partially buried in sand (Gardner Creek) and the other was mixed debris, which may indicate dumping grounds. The area around the Digby ferry tract - informally called ‘the Dump’ between Digby Neck and Victoria Beach, was identified by fishers as a dumping hot spot (Goodman et al., 2019). Hot spots have also been identified in the French Mediterranean (Gerigny et al., 2019) and areas with higher than average debris densities in NW Europe (Maes et al., 2018). Debris was detected on sand (40.4%), mixed cobble and gravel (12.8%), fine sand (10.6%) and mixed sand and gravel (19.1%) (Table 3). This contrasts to results from the literature which suggest that harder/coarser benthic environments serve as dominant substrates for debris accumulation (Watters et al., 2010; Melli et al., 2017). This variation may be attributed to the unique benthic environment, sediment transportation and bottom currents in the BoF region, and because fewer stations were sampled on harder/coarser vs. softer/finer sediment bottoms (Li et al., 2015; Fig. 2). High turbidity from sedimentation, high current speeds (e.g., 3 kts), and surface wave action (> 1 m) may have contributed to underestimates of debris items and subsequent characterization using seafloor video collected by the drop camera system. For example, items < 10 cm could be detected from transects where survey conditions were optimal (i.e., slack current, low turbidity and a consistent 1 m height off the seafloor). For transects with higher drift speeds, lower visibility and high wave action, items < 10 cm may have gone undetected. However, we did not evaluate stations by tidal flow. Colour of debris and seafloor may have also posed detection limitations. Shell fragments and debris may have been indistinguishable from each other if litter was white, and non-uniformly colored substrata, such as rocks, may camouflage debris better than uniformly colored substrata such as sand, alluding to better detectability over sandy substrate types. However, some debris may become buried by sediment if settled on the seafloor for extended periods, reducing detectability. There were no observed incidences of ghost fishing, although one derelict lobster trap had shown seafloor abrasion and contained a moon
snail (Euspira heros) shell (Fig. 4). All other debris were either laying on or fixed to the seafloor with no visible impact to the benthic environment. This contrasts from the literature which shows direct links between debris and benthic habitat destruction (Angiolillo et al., 2015; Melli et al., 2017). There was limited biofouling on some debris (57%), while others (22%) showed moderate fouling with barnacles and light algal growth. Based on these findings, seafloor debris in the BoF is numerous and widespread, regardless of parameters used for comparisons. Quantities of debris stranded on the seafloor in the BoF and elsewhere remain problematic, because plastic debris continues to fragment into secondary microplastics, where long-term exposure at environmentally relevant concentration levels can negatively impact benthic biota (Bour et al., 2018; Karbalaei et al., 2018). Although, seafloor marine debris often goes unnoticed as it is out of sight, it is important to limit sources of marine debris pollution (Pettipas et al., 2016). In terms of future solutions, marine debris retrieval efforts in the BoF are unrealistic due to the highly dynamic nature of the marine environment. Implementation and enforcement of policies to eliminate single-use plastic items (e.g., Xanthos and Walker, 2017; Schnurr et al., 2018; Prata et al., 2019) and to improve education among fishers to reduce illegal dumping of fishing gear and related waste (Goodman et al., 2019) is recommended. This research highlights point source pollution from the fishing industry, providing empirical data to better monitor and manage waste associated with the industry. Some fishers' have mixed perceptions and understandings of their environmental impact on the marine environment. This creates barriers to limiting illegal disposal atsea, which needs to be addressed in the future by improving education to limit illegal disposal at-sea (Goodman et al., 2019). Given that Canada recently signed on to the Ocean Plastics Charter and to the Global Ghost Gear Initiative, both in 2018 (G7, 2018; Global Affairs Canada, 2018; Karbalaei et al., 2018), there is a growing sense of urgency to move forward with these commitments to improve land and oceanbased waste management. Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Acknowledgments
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This study was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), Grant/Award Number: RGPIN2018-04119 to Tony R. Walker, and the NSERC Industrial Research Chair for Colleges grant CIRC 472115-14, NSERC Engage grant 50220016 in partnership with the Full Bay Scallop Association and Fisheries and Oceans Canada grants MECTS-#3674626 and MECTS-#3802469 to Craig J. Brown. Special thanks to Larissa Pattison from the Applied Oceans Research Group at NSCC for analysis support. References Ambrose, K.K., Box, C., Boxall, J., Brooks, A., Eriksen, M., Fabres, J., Fylakis, G., Walker, T.R., 2019. Spatial trends and drivers of marine debris accumulation on shorelines in South Eleuthera, the Bahamas using citizen science. Mar. Pollut. Bull. 142, 145–154. Angiolillo, M., Lorenzo, B.D., Farcomeni, A., Bo, M., Bavestrello, G., Santangelo, G., … Canese, S. 2015. Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy). Mar. Pollut. Bull., 92(1–2), 149–159. doi: https:// doi.org/10.1016/j.marpolbul.2014.12.044. Avery-Gomm, S., Walker, T.R., Mallory, M.L., Provencher, J.F., 2019. There is nothing convenient about plastic pollution. Rejoinder to Stafford and Jones “Viewpoint–Ocean plastic pollution: a convenient but distracting truth?”. Mar. Policy 106, 103552. Barnett, A.J., Wiber, M.G., Rooney, M.P., Maillet, D.G., 2016. The role of public participation GIS (PPGIS) and fishermens perceptions of risk in marine debris mitigation in the Bay of Fundy, Canada. Ocean Coast. Manag. 133, 85–94. https://doi.org/10. 1016/j.ocecoaman.2016.09.002. Barnette, M.C., 2001. Effects of litter from fishing gear. In: Commercial Fishing: The Wider Ecological Impacts, NMFS-SEFSC-449, pp. 28–29. Bour, A., Haarr, A., Keiter, S., Hylland, K., 2018. Environmentally relevant microplastic exposure affects sediment-dwelling bivalves. Environ. Pollut. 236, 652–660. https:// doi.org/10.1016/j.envpol.2018.02.006. Brown, C.J., Beaudoin, J., Brissette, M., Gazzola, V., 2019. Multispectral multibeam echo sounder backscatter as a tool for improved seafloor characterization. Geosci. Can. 9 (3), 126. https://doi.org/10.3390/geosciences9030126. Buzeta, M.I., 2014. Identification and review of ecologically and biologically significant areas in the Bay of Fundy. DFO Can. Sci. Advis. Sec. Res. Doc 2013/065. vi + 59 p. Chiba, S., Saito, H., Fletcher, R., Yogi, T., Kayo, M., Miyagi, S., ... Fujikura, K., 2018. Human footprint in the abyss: 30 year records of deep-sea plastic debris. Mar. Policy 96, 204–212. https://doi.org/10.1016/j.marpol.2018.03.022. Fisheries and Oceans Canada, 2018. Fishing effort within Significant Benthic Areas in Canada's Atlantic and Eastern Arctic marine waters. Record ID: 273df20a-47ae-42c0bc58-01e451d4897a. [dataset]. Retrieved from. https://open.canada.ca/data/en/ dataset/273df20a-47ae-42c0-bc58-01e451d4897a. Fisheries and Oceans Canada, 2019. Canada's fisheries fast facts. Retrieved from. http:// www.dfo-mpo.gc.ca/stats/facts-Info-17-eng.htm 2018. G7, 2019. Ocean Plastics Charter. pp. 2–4. Retreived from. http://publications.gc.ca/ collections/collection_2018/amc-gac/FR5-144-2018-32-eng.pdf 2018. Galgani, F., Leaute, J., Moguedet, P., Souplet, A., Verin, Y., Carpentier, A., … Nerisson, P. 2000. Litter on the sea floor along European coasts. Mar. Pollut. Bull., 40(6), 516–527. doi: https://doi.org/10.1016/s0025-326x(99)00234-9. Galgani, F., Hanke, G., Maes, T., 2015. Global distribution, composition and abundance of marine litter. Mar. Anthro. Lit. 29–56. https://doi.org/10.1007/978-3-319-165103_2. Gerigny, O., Brun, M., Fabri, M., Tomasino, C., Moigne, M.L., Jadaud, A., Galgani, F., 2019. Seafloor litter from the continental shelf and canyons in French Mediterranean water: distribution, typologies and trends. Mar. Pollut. Bull. 146, 653–666. https:// doi.org/10.1016/j.marpolbul.2019.07.030. Global Affairs Canada, 2018. Environment, oceans and energy ministers ready to take action on our oceans and seas; conclude G7 joint meeting on healthy oceans, seas and resilient coastal communities. Retrieved from. https://www.canada.ca/en/globalaffairs/news/2018/09/environment-oceans-and-energy-ministers-ready-to-takeaction-on-our-oceans-and-seas-conclude-g7-joint-meeting-on-healthy-oceans-seasand-resilient-.html. Goodman, A.J., Brillant, S., Walker, T.R., Bailey, M., Callaghan, C., 2019. A ghostly issue: managing abandoned, lost and discarded lobster fishing gear in the Bay of Fundy in
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