The Future of Eelgrass (Zostera marina) in the Salish Sea
Nudging resilience– A look at wasting disease in our changing climate
Maria Catanzaro
Keywords: eelgrass, Salish Sea, restoration, climate change, wasting disease
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Summary
Eelgrass (Z. marina) meadows once flourished in the Salish Sea, providing cultural value and playing critical ecological roles. Eelgrass supports marine food webs, provides habitat for migrating salmonids and spawning ground for Pacific herring (Clupea pallasii). Eelgrass meadows increase water quality, sequester carbon, and stabilize shorelines by attenuating waves and reducing erosion. These ecosystems are increasingly being degraded by anthropogenic influences, including watershed stressors like increased sedimentation which smothers eelgrass, contamination and shading from log storage, and altering shorelines with hard armouring. Natural processes are impeded, causing increased stress on eelgrass ecosystems. As population grows and coastal development pressures continue, eelgrass in the Salish Sea will continue to face ongoing anthropogenic threats and will be compounded by future climate regimes, including warming sea temperatures, sea level rise and increased salinity. These cumulative stressors make Z. marina more susceptible to a marine pathogen, Labyrinthula zosterae, which can lead to eelgrass wasting disease. Wasting disease has caused large-scale declines in the past and eelgrass restoration in the Salish Sea is currently being faced with this challenge. The future of eelgrass in the Salish Sea depends on whether we can stem the rising tide of wasting disease. Novel strategies can start to be included in restoration plans that may help create more resilient transplants. Some examples include: prioritizing sites through data on disease metrics and strain diversity, strategic selection of donor material whilst increasing genetic diversity of transplanted beds and through incorporating biological interactions.
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Genealogy
Traversing inland marine waters throughout British Columbia and Washington State, the Salish Sea makes up approximately 18, 000 km2, comprising diverse passages, fjords, sounds, straits and hundreds of islands (Mullan 2010). The Salish Sea includes the Strait of Georgia, Strait of the Juan de Fuca and Puget Sound and spans 7, 500 km of coastline (Dethier et al. 2016; Mullan 2010). The Salish Sea was known for its high biodiversity and abundant resources. One important part of the Salish Sea were the eelgrass (Zostera marina) meadows that dotted and hugged the coastlines, while also found playing critical ecological roles along temperate coasts worldwide (Rasmussen 1977). These lush green meadows of flowering marine plants supported a wide range of biota, including providing food for resident and migrating birds, serving as vital habitat for Pacific herring (Clupea pallasii) spawning grounds, and providing salmonid species shelter and refuge as they navigated their ways to the open sea and back to their homes for spawning (Milman and Hurst 2005; Gibsons n.d.; Phillips 1984). Eelgrass meadows kept the marine food web intact and these nutrient-rich intertidal areas included an abundance of clams, mussels, dungeness crabs, and oysters (Taylor and Meyer 2005). Stevenson and Harrington (2005) included a quote in Islands in the Salish Sea, a community atlas, from Dave Elliot Sr., Tsartlip band, W̱SÁNEĆ, stating, “We had so much of everything. It would be impossible to starve.”
Eelgrass (Zostera marina) meadows were tended by First Nations groups in British Columbia, Canada, who gathered the rhizomes and young shoots with techniques that allowed for sustainable use (Cullis-Suzuki et al. 2015). For example, Z. marina was cultivated and selectively harvested by the Kwakwaka’wakw from British Columbia in the springtime, sometimes associated with the timing of clam harvesting (Cullis-Suzuki et al. 2015). First Nations groups would use various techniques to gather this plant, such as by hand, using a long pole and lingcod spears (Cullis-Suzuki et al. 2015). As settlers began colonizing this region, there was a shift to resource extraction. Land-use was changing and alteration of shorelines with concrete structures began. Industrialization, agriculture and forestry was ever-more present, causing sedimentation and releasing contaminated runoff. Additionally, building of commercial ports and urbanization all contributed to the alteration of natural processes along the coasts. These alterations of the land changed these pristine, biodiverse and culturally important coastlines that was once the cornerstone supporting traditional ways of life.
Short and Wyllie-Echeverria (1996) stated that there has been a documented loss of 90 000 ha of Z. marina over the last century. Attention started to be paid to these ecologically important systems, initially for the reason that the declines impacted fisheries. Eelgrass meadows experienced additional threats that wiped out large areas completely. For example, some methods of oyster culturing led to the decline in Z. marina in the Pacific Northwest, USA, as a result of sediment erosion (ibid). Natural disturbances like winter freeze in the Pacific Northwest, United States, caused large die-offs, too (ibid).
Research started appearing that showed how natural disturbances like disease, were piggybacking on human-induced disturbances. Z. marina is not known to experience chronic fouling under healthy circumstances, but when under stress and pressure from additional sources, these marine angiosperms have a greater likelihood of being infected (Papazian et al. 2019). While Z. marina plants were stressed from human-induced influences, in combination with the occurrence of atypical warming events, a wasting disease started infecting them and began threatening their survival. The slime mold, Labyrinthula zosterae, caused a wasting disease in Z. marina in the 1930’s and led to a 90% decline in populations in North America and Europe, specifically along the Atlantic coasts but evidence also showed occurrence in Pacific populations on more local and medium-scales (Olsen et al. 2015; Muehlstein, Porter and Short 1991; Short and Wyllie-Echeverria 1996). Cases were documented between Nanaimo, British Columbia and San Diego, California (Graham et al. 2016). Labyrinthula zosterae presented itself as black-dark brown lesions (spots, patches and streaks) on the plant’s leaves and reduced the plant’s ability to photosynthesize by preventing proper nutrient transport and oxygen (Muehlstein, Porter and Short 1991; Ralph and Short 2002; Olsen et al. 2015). Even areas of healthy-looking green leaves up to 5mm away from a lesion experienced these effects, impacting the ability to handle additional stresses, such as temperature changes and turbidity, leading to reduced health and potential die-off (Sullivan et al. 2018; Ralph and Short 2002). The 1980’s showed another spike in the occurrence of the disease in the United States, such as in the San Juan Islands, Washington, which continues to be documented, and on a smaller scale in Europe (Short and Wyllie-Echeverria 1996; Graham et al. 2016).
Eelgrass (Zostera marina) meadows were tended by First Nations groups in British Columbia, Canada, who gathered the rhizomes and young shoots with techniques that allowed for sustainable use (Cullis-Suzuki et al. 2015). For example, Z. marina was cultivated and selectively harvested by the Kwakwaka’wakw from British Columbia in the springtime, sometimes associated with the timing of clam harvesting (Cullis-Suzuki et al. 2015). First Nations groups would use various techniques to gather this plant, such as by hand, using a long pole and lingcod spears (Cullis-Suzuki et al. 2015). As settlers began colonizing this region, there was a shift to resource extraction. Land-use was changing and alteration of shorelines with concrete structures began. Industrialization, agriculture and forestry was ever-more present, causing sedimentation and releasing contaminated runoff. Additionally, building of commercial ports and urbanization all contributed to the alteration of natural processes along the coasts. These alterations of the land changed these pristine, biodiverse and culturally important coastlines that was once the cornerstone supporting traditional ways of life.
Short and Wyllie-Echeverria (1996) stated that there has been a documented loss of 90 000 ha of Z. marina over the last century. Attention started to be paid to these ecologically important systems, initially for the reason that the declines impacted fisheries. Eelgrass meadows experienced additional threats that wiped out large areas completely. For example, some methods of oyster culturing led to the decline in Z. marina in the Pacific Northwest, USA, as a result of sediment erosion (ibid). Natural disturbances like winter freeze in the Pacific Northwest, United States, caused large die-offs, too (ibid).
Research started appearing that showed how natural disturbances like disease, were piggybacking on human-induced disturbances. Z. marina is not known to experience chronic fouling under healthy circumstances, but when under stress and pressure from additional sources, these marine angiosperms have a greater likelihood of being infected (Papazian et al. 2019). While Z. marina plants were stressed from human-induced influences, in combination with the occurrence of atypical warming events, a wasting disease started infecting them and began threatening their survival. The slime mold, Labyrinthula zosterae, caused a wasting disease in Z. marina in the 1930’s and led to a 90% decline in populations in North America and Europe, specifically along the Atlantic coasts but evidence also showed occurrence in Pacific populations on more local and medium-scales (Olsen et al. 2015; Muehlstein, Porter and Short 1991; Short and Wyllie-Echeverria 1996). Cases were documented between Nanaimo, British Columbia and San Diego, California (Graham et al. 2016). Labyrinthula zosterae presented itself as black-dark brown lesions (spots, patches and streaks) on the plant’s leaves and reduced the plant’s ability to photosynthesize by preventing proper nutrient transport and oxygen (Muehlstein, Porter and Short 1991; Ralph and Short 2002; Olsen et al. 2015). Even areas of healthy-looking green leaves up to 5mm away from a lesion experienced these effects, impacting the ability to handle additional stresses, such as temperature changes and turbidity, leading to reduced health and potential die-off (Sullivan et al. 2018; Ralph and Short 2002). The 1980’s showed another spike in the occurrence of the disease in the United States, such as in the San Juan Islands, Washington, which continues to be documented, and on a smaller scale in Europe (Short and Wyllie-Echeverria 1996; Graham et al. 2016).
present tense
Today, we continue to see the anthropogenic impacts on these coastal ecosystems, exacerbating the reoccurrence of wasting disease in Z. marina populations. The decline in eelgrass beds have weakened natural processes and ecosystem functions they once provided, such as supporting the marine food web, increasing water quality, carbon sequestration, shoreline stabilization, and providing a structured habitat for nurseries and as shelter (Lee Long and Thom 2001; Phillips 1984; McDevitt-Irwin et al. 2016).
The Strait of Georgia within the Salish Sea has experienced the most modification of all Pacific Canada regions and the longest exposure to human activities (Okey et al. 2014). Nahirnick (2018) acknowledges that coastal use, such as in the Gulf Islands of British Columbia, is showing a decline in overall environmental health in the Salish Sea, thus contributing to the deterioration of eelgrass meadows. Natural estuarine and shoreline marine habitats are constantly experiencing the impacts from activities on land, such as modification for coastal development and the abundance of log-booms that overtake the coast, resulting in the deterioration of these intertidal areas (Wright, Boyer & Erikson 2012; Dunster 2005). As population continues to increase, the manipulation of our environments to serve human needs and economic gain carries on. Compensatory projects are now faced with dredging, filling and recontouring sites in a plea to re-establish conditions suitable for eelgrass to exist. An example of this the Tsawwassen Ferry Terminal in Roberts Bank, Vancouver, at the eastern shore in the Strait of Georgia that is heavily altered and novel techniques are being planned to compensate for the destruction of the meadows (Atkins et al. 2016). This is resulting in a loss in biodiversity, the loss of essential ecosystem services and rendering a system that can no longer support organisms that had once called it home.
To make matters worse, our changing climate is adding extra pressure to these important nearshore environments, for example, through increased storm intensity, sea level rise and warming waters. An abundance of literature is claiming the critical role that warmer sea temperatures are playing in the outbreaks of wasting disease (Figure 1). Olsen et al. (2015) suggests that either environmental drivers increase the severity of the pathogen or that seagrass defenses are suppressed as a result of negative environmental factors, thus increasing the ability of wasting disease to infect the plants. Labyrinthula zosterae is opportunistic and capitalize on the stressed Z. marina shoots and cause greater declines as a result. Eelgrass restoration sites in the Salish Sea are currently being faced with this challenge, with some transplanted shoots currently being infected with L. Zosterae.
To rock the boat a bit more, governance of nearshore environments and their legal and ownership frameworks influence the health of these nearshore environments. Government on both sides of the border provide licenses for activity along the coast, such as marinas, log storage, aquaculture and docks with compensatory activities required to offset damages to the environment (Green Shores 2009). Additionally, owners of waterfront property have rights to create protective structures if they are concerned with erosion and flooding (Green Shores 2009). The go-to method is hard armouring and these structures alter hydrological regimes and can negatively impact eelgrass beds. Furthermore, the varying levels of governance within the nearshore environments can impede the protection of these ecosystems.
On the bright side, the Nuu-Chah-Nulth/West Coast Vancouver Island Regional Aquatic Management Board, People for Puget Sound’s Habitat Project, Salish Sea Nearshore Habitat Recovery Team, the Salish Sea Council and restoration organization SeaChange are examples of groups that work to address and contribute to the protection and rehabilitation of these nearshore environments (Wright 2002). Research efforts on both sides of the border are currently underway, including extensive mapping of eelgrass beds, experimental transplantations and wasting disease research (Figure 1).
The Strait of Georgia within the Salish Sea has experienced the most modification of all Pacific Canada regions and the longest exposure to human activities (Okey et al. 2014). Nahirnick (2018) acknowledges that coastal use, such as in the Gulf Islands of British Columbia, is showing a decline in overall environmental health in the Salish Sea, thus contributing to the deterioration of eelgrass meadows. Natural estuarine and shoreline marine habitats are constantly experiencing the impacts from activities on land, such as modification for coastal development and the abundance of log-booms that overtake the coast, resulting in the deterioration of these intertidal areas (Wright, Boyer & Erikson 2012; Dunster 2005). As population continues to increase, the manipulation of our environments to serve human needs and economic gain carries on. Compensatory projects are now faced with dredging, filling and recontouring sites in a plea to re-establish conditions suitable for eelgrass to exist. An example of this the Tsawwassen Ferry Terminal in Roberts Bank, Vancouver, at the eastern shore in the Strait of Georgia that is heavily altered and novel techniques are being planned to compensate for the destruction of the meadows (Atkins et al. 2016). This is resulting in a loss in biodiversity, the loss of essential ecosystem services and rendering a system that can no longer support organisms that had once called it home.
To make matters worse, our changing climate is adding extra pressure to these important nearshore environments, for example, through increased storm intensity, sea level rise and warming waters. An abundance of literature is claiming the critical role that warmer sea temperatures are playing in the outbreaks of wasting disease (Figure 1). Olsen et al. (2015) suggests that either environmental drivers increase the severity of the pathogen or that seagrass defenses are suppressed as a result of negative environmental factors, thus increasing the ability of wasting disease to infect the plants. Labyrinthula zosterae is opportunistic and capitalize on the stressed Z. marina shoots and cause greater declines as a result. Eelgrass restoration sites in the Salish Sea are currently being faced with this challenge, with some transplanted shoots currently being infected with L. Zosterae.
To rock the boat a bit more, governance of nearshore environments and their legal and ownership frameworks influence the health of these nearshore environments. Government on both sides of the border provide licenses for activity along the coast, such as marinas, log storage, aquaculture and docks with compensatory activities required to offset damages to the environment (Green Shores 2009). Additionally, owners of waterfront property have rights to create protective structures if they are concerned with erosion and flooding (Green Shores 2009). The go-to method is hard armouring and these structures alter hydrological regimes and can negatively impact eelgrass beds. Furthermore, the varying levels of governance within the nearshore environments can impede the protection of these ecosystems.
On the bright side, the Nuu-Chah-Nulth/West Coast Vancouver Island Regional Aquatic Management Board, People for Puget Sound’s Habitat Project, Salish Sea Nearshore Habitat Recovery Team, the Salish Sea Council and restoration organization SeaChange are examples of groups that work to address and contribute to the protection and rehabilitation of these nearshore environments (Wright 2002). Research efforts on both sides of the border are currently underway, including extensive mapping of eelgrass beds, experimental transplantations and wasting disease research (Figure 1).
Future Trajectory
As population grows and coastal development pressures continue, eelgrass in the Salish Sea will continue to face ongoing anthropogenic threats and will be compounded by future climate regimes. Being a sensitive bioregion based on its geomorphology, oceanography and anthropogenic stressors, the Strait of Georgia, for example, is expected to experience warmer waters, including increased warmer freshwater inputs, with a potential projection of up to 1°C between 2015-2025 and 1-2°C for 2045-2055 (Okey et al. 2014). Unsustainable farming practices propelling eutrophication, shoreline armouring and industry waste are examples of influences that will continue to impact nearshore ecosystems. In these scenarios, anthropogenic stressors are compounded by warmer waters and eelgrass resiliency is reduced, resulting in more frequent disease outbreaks (Sullivan et al. 2018). The health of eelgrass meadows will depend on whether we can create ways to increase resiliency and reduce the amount of stressors they face.
Shoreline and eelgrass restoration initiatives are critical and novel ways to combat physiological stress and increasing resilience are necessary. For example, techniques are being attempted in Australia to reduce stress inflicted on transplanted eelgrass from increased wave energy and storm intensity by incorporating bagged recycled oyster shells to help protect, stabilize and encourage the anchoring and establishment of shoots (Figure 2) (Estuary Care Foundation 2018). Additionally, Green Shores, a Victoria, British Columbia based organization, helps restore shorelines by reintroducing natural physical processes and filtering of runoff, which can help decrease the amount of stressors on eelgrass giving them a better chance at fending off pathogens, such as L. zosterae (Figure 3). To specifically address wasting disease in restoration initiatives, groups can start to include some additional strategies to their restoration toolkit. Based on research conducted on L. zosterae, novel techniques and strategic steps can be incorporated into plans. One idea is strategically prioritizing sites based on correlations between salinity and depth and disease susceptibility. Guided by the precautionary principle, selection of favorable donor stock can be encouraged, whilst increasing genetic diversity to increase resilience. Keeping up with research on sediment microbiomes, disease metrics and strain diversity would aid in this process as well. Another strategy is incorporating biological interactions which may contribute to the strengthening of new transplants against wasting disease. For example, one suggestion has been the partnership of Z. marina with oysters (Crassostrea gigas) which has shown to have potential for a symbiotic relationship: oysters helping decrease pathogens like Labyrinthula zosterae affecting the eelgrass whilst providing a lower pH environment for the oysters (Groner et al. 2016). Taking strategic approaches to nudge eelgrass towards resilience may bring us one step closer to increasing the survival of eelgrass beds in current and future climatic regimes. In line with what John Elliot of W̱SÁNEĆ Coast Salish Nation said, just as our earth takes care of us by providing us food, shelter, and a safe place, we must provide the same respect back (Stevenson and Harrington 2005). |
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Acknowledgements
I appreciate the generosity, insights and time from the
following lovely humans: Eric Higgs, Nikki Wright, Cynthia Durance, Hilary Harrop-Archibald,
Bart Christiaen and Jeffrey Gaeckle.
References
Atkins, R.J., Tidd, M., and Ruffo, G., 2016. Sturgeon Bank, Fraser River Delta, BC, Canada: 150 Years of Influence on Salt Marsh Sedimentation. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research Issue, No. 75, pp. 790-794. Coconut Creek (Florida).
Cullis-Suzuki, S., S. Wyllie-Echeverria, K. A. Dick, M. D. Sewid-Smith, O. K. Recalma-Clutesi, and N. J. Turner. 2015. Tending the meadows of the sea: A disturbance experiment based on traditional indigenous harvesting of Zostera marina L. (Zosteraceae) the southern region of Canada’s west coast. Aquatic Botany 127:26–34.
Dethier, M. N., W. W. Raymond, A. N. McBride, J. D. Toft, J. R. Cordell, A. S. Ogston, S. M. Heerhartz, and H. D. Berry. 2016. Multiscale impacts of armoring on Salish Sea shorelines: Evidence for cumulative and threshold effects. Estuarine, Coastal and Shelf Science 175:106–117.
Government of Canada, Transport Canada, Environmental Protection (AMSEE). 2005. Pollution Prevention Guidelines for the Operation of Cruise Ships under Canadian Jurisdiction. TP 14202 E. Marine Safety 531748v4.
www.tc.gc.ca/media/documents/marinesafety/tp14202e.pdf
Graham, O., M. Eisenlord, and D. Harvell. 2016. Plant demographics and environment influence on seagrass wasting disease in Zostera marina. False Bay Seagrass Report- Part 1. https://www.sanjuanco.com/DocumentCenter/View/13729/PSJ000-17-0003-EXHIBIT-38
Green Shores Technical Working Group. 2009. Coastal Shore Jurisdiction in British Columbia. Issue Sheet October 2009. https://www.salishsea.ca/resources/Riparianrights/Greenshores%20JurisdictionIssueSheet_finalVer4.pdf
Groner, M. L., C. A. Burge, R. Cox, N. D. Rivlin, M. Turner, K. L. Van Alstyne, S. Wyllie-Echeverria, J. Bucci, P. Staudigel, and C. S. Friedman. 2018. Oysters and eelgrass: potential partners in a high pCO 2 ocean. Ecology 99:1802–1814.
Lee Long, W. J., and R. M. Thom. 2001. Improving seagrass habitat quality. Pages 407-423 in F. Short and R. Coles, editors. Global Seagrass Research Methods. Elsevier Science Press. Amsterdam, NL.
McDevitt-Irwin, J. M., J. C. Iacarella and J. K. Baum. 2016. Reassessing the nursery role of seagrass habitats from temperate to tropical regions: a meta-analysis. Marine Ecology Progress Series. 557:133-143.
Milman, L. A., and Hurst, E. J. 2005. In Stevenson, J., and Harrington, S. Islands in the Salish Sea: a community atlas. Touchwood Editions.
Muehlstein, L. K., D. Porter, and F. T. Short. 1991. Labyrinthula zosterae sp. nov., the Causative Agent of Wasting Disease of Eelgrass, Zostera marina. Mycologia 83:180–191.
Mullan, S. 2010. Tidal sedimentology and geomorphology in the central Salish Sea straits, British Columbia and Washington State. Dissertation. University of Victoria, British Columbia.
Nahirnick, N. K. 2018. Long-term Spatial-temporal Eelgrass (Zostera marina) Habitat Change (1932-2016) in the Salish Sea using Historic Aerial Photography and Unmanned Aerial Vehicle. Dissertation. University of Victoria, British Columbia.
Okey, T. A., H. M. Alidina, V. Lo, and S. Jessen. 2014. Effects of climate change on Canada’s Pacific marine ecosystems: a summary of scientific knowledge. Reviews in Fish Biology and Fisheries 24:519–559.
Olsen, Y. S., M. Potouroglou, N. Garcias-Bonet, and C. M. Duarte. 2015. Warming Reduces Pathogen Pressure on a Climate-Vulnerable Seagrass Species. Estuaries and Coasts 38:659–667.
Papazian, S., D. Parrot, B. Burýšková, F. Weinberger, and D. Tasdemir. 2019. Surface chemical defence of the eelgrass Zostera marina against microbial foulers. Scientific Reports 9:3323.
Phillips, R. C. 1984. The ecology of eelgrass meadows in the Pacific Northwest: a community profile. U.S. Fish and Wildlife Service United States. National Coastal Ecosystems Team. Washington, DC.
Port River and Barker Inlet Estuary: Monitoring and Restoring Seagrass. 2018. Estuary Care Foundation, University of Adelaide.
https://estuary.org.au/wp-content/uploads/2018/12/Monitoring-and-Restoring-Seagrass_Port-River-Barker-Inlet-Estuary.pdf
Ralph, P., and F. Short. 2002. Impact of the wasting disease pathogen, Labyrinthula zosterae, on the photobiology of eelgrass Zostera marina. Marine Ecology Progress Series 226:265–271.
Rasmussen, E. 1977. The wasting disease of eelgrass (Zostera marina) and its effects on environmental factors and fauna. Pages 1-51 in C. P. McRoy and C. Helfferich, editors. Seagrass Ecosystems: A Scientific Perspective. M. Dekker Inc. New York, USA.
Short, F. T., & S. Wyllie-Echeverria. 1996. Natural and human-induced disturbance of seagrasses. Environmental Conservation, 23(1), 17–27.
Sullivan, B. K., S. M. Trevathan-Tackett, S. Neuhauser, and L. L. Govers. 2018. Review: Host-pathogen dynamics of seagrass diseases under future global change. Marine Pollution Bulletin 134:75–88.
Taylor, D., and Meyer, M. 2005. In Stevenson, J., and Harrington, S. Islands in the Salish Sea: a community atlas. Touchwood Editions.
Town of Gibsons. n.d. Eelgrass Fact Sheet. Online: (http://gibsons.ca/wp-content/uploads/2017/12/eelgrassfacts.pdf). Accessed 8 February 2019.
Washington State Department of Natural Resources, Aquatic Resources Division. 2015. Puget Sound Eelgrass (Zostera marina) Recovery Strategy. www.dnr.wa.gov/publications/aqr_nrsh_eelgrass_strategy_final.pdf
Wright, N. 2002. Eelgrass Conservation for the B. C. Coast. A Discussion Paper.
Wright, N., Boyer, L., & Erikson, K. (2012). Final Report. Nearshore Eelgrass Inventory. Gulf Islands, British Columbia.
http://www.islandstrust.bc.ca/media/232133/eelgrass%20inventory%20report.pdf
Cullis-Suzuki, S., S. Wyllie-Echeverria, K. A. Dick, M. D. Sewid-Smith, O. K. Recalma-Clutesi, and N. J. Turner. 2015. Tending the meadows of the sea: A disturbance experiment based on traditional indigenous harvesting of Zostera marina L. (Zosteraceae) the southern region of Canada’s west coast. Aquatic Botany 127:26–34.
Dethier, M. N., W. W. Raymond, A. N. McBride, J. D. Toft, J. R. Cordell, A. S. Ogston, S. M. Heerhartz, and H. D. Berry. 2016. Multiscale impacts of armoring on Salish Sea shorelines: Evidence for cumulative and threshold effects. Estuarine, Coastal and Shelf Science 175:106–117.
Government of Canada, Transport Canada, Environmental Protection (AMSEE). 2005. Pollution Prevention Guidelines for the Operation of Cruise Ships under Canadian Jurisdiction. TP 14202 E. Marine Safety 531748v4.
www.tc.gc.ca/media/documents/marinesafety/tp14202e.pdf
Graham, O., M. Eisenlord, and D. Harvell. 2016. Plant demographics and environment influence on seagrass wasting disease in Zostera marina. False Bay Seagrass Report- Part 1. https://www.sanjuanco.com/DocumentCenter/View/13729/PSJ000-17-0003-EXHIBIT-38
Green Shores Technical Working Group. 2009. Coastal Shore Jurisdiction in British Columbia. Issue Sheet October 2009. https://www.salishsea.ca/resources/Riparianrights/Greenshores%20JurisdictionIssueSheet_finalVer4.pdf
Groner, M. L., C. A. Burge, R. Cox, N. D. Rivlin, M. Turner, K. L. Van Alstyne, S. Wyllie-Echeverria, J. Bucci, P. Staudigel, and C. S. Friedman. 2018. Oysters and eelgrass: potential partners in a high pCO 2 ocean. Ecology 99:1802–1814.
Lee Long, W. J., and R. M. Thom. 2001. Improving seagrass habitat quality. Pages 407-423 in F. Short and R. Coles, editors. Global Seagrass Research Methods. Elsevier Science Press. Amsterdam, NL.
McDevitt-Irwin, J. M., J. C. Iacarella and J. K. Baum. 2016. Reassessing the nursery role of seagrass habitats from temperate to tropical regions: a meta-analysis. Marine Ecology Progress Series. 557:133-143.
Milman, L. A., and Hurst, E. J. 2005. In Stevenson, J., and Harrington, S. Islands in the Salish Sea: a community atlas. Touchwood Editions.
Muehlstein, L. K., D. Porter, and F. T. Short. 1991. Labyrinthula zosterae sp. nov., the Causative Agent of Wasting Disease of Eelgrass, Zostera marina. Mycologia 83:180–191.
Mullan, S. 2010. Tidal sedimentology and geomorphology in the central Salish Sea straits, British Columbia and Washington State. Dissertation. University of Victoria, British Columbia.
Nahirnick, N. K. 2018. Long-term Spatial-temporal Eelgrass (Zostera marina) Habitat Change (1932-2016) in the Salish Sea using Historic Aerial Photography and Unmanned Aerial Vehicle. Dissertation. University of Victoria, British Columbia.
Okey, T. A., H. M. Alidina, V. Lo, and S. Jessen. 2014. Effects of climate change on Canada’s Pacific marine ecosystems: a summary of scientific knowledge. Reviews in Fish Biology and Fisheries 24:519–559.
Olsen, Y. S., M. Potouroglou, N. Garcias-Bonet, and C. M. Duarte. 2015. Warming Reduces Pathogen Pressure on a Climate-Vulnerable Seagrass Species. Estuaries and Coasts 38:659–667.
Papazian, S., D. Parrot, B. Burýšková, F. Weinberger, and D. Tasdemir. 2019. Surface chemical defence of the eelgrass Zostera marina against microbial foulers. Scientific Reports 9:3323.
Phillips, R. C. 1984. The ecology of eelgrass meadows in the Pacific Northwest: a community profile. U.S. Fish and Wildlife Service United States. National Coastal Ecosystems Team. Washington, DC.
Port River and Barker Inlet Estuary: Monitoring and Restoring Seagrass. 2018. Estuary Care Foundation, University of Adelaide.
https://estuary.org.au/wp-content/uploads/2018/12/Monitoring-and-Restoring-Seagrass_Port-River-Barker-Inlet-Estuary.pdf
Ralph, P., and F. Short. 2002. Impact of the wasting disease pathogen, Labyrinthula zosterae, on the photobiology of eelgrass Zostera marina. Marine Ecology Progress Series 226:265–271.
Rasmussen, E. 1977. The wasting disease of eelgrass (Zostera marina) and its effects on environmental factors and fauna. Pages 1-51 in C. P. McRoy and C. Helfferich, editors. Seagrass Ecosystems: A Scientific Perspective. M. Dekker Inc. New York, USA.
Short, F. T., & S. Wyllie-Echeverria. 1996. Natural and human-induced disturbance of seagrasses. Environmental Conservation, 23(1), 17–27.
Sullivan, B. K., S. M. Trevathan-Tackett, S. Neuhauser, and L. L. Govers. 2018. Review: Host-pathogen dynamics of seagrass diseases under future global change. Marine Pollution Bulletin 134:75–88.
Taylor, D., and Meyer, M. 2005. In Stevenson, J., and Harrington, S. Islands in the Salish Sea: a community atlas. Touchwood Editions.
Town of Gibsons. n.d. Eelgrass Fact Sheet. Online: (http://gibsons.ca/wp-content/uploads/2017/12/eelgrassfacts.pdf). Accessed 8 February 2019.
Washington State Department of Natural Resources, Aquatic Resources Division. 2015. Puget Sound Eelgrass (Zostera marina) Recovery Strategy. www.dnr.wa.gov/publications/aqr_nrsh_eelgrass_strategy_final.pdf
Wright, N. 2002. Eelgrass Conservation for the B. C. Coast. A Discussion Paper.
Wright, N., Boyer, L., & Erikson, K. (2012). Final Report. Nearshore Eelgrass Inventory. Gulf Islands, British Columbia.
http://www.islandstrust.bc.ca/media/232133/eelgrass%20inventory%20report.pdf