A comparison of the impact of ‘seagrass-friendly’ boat mooring systems on Posidonia australis

Demers, Marie‐Claire A.; Davis, Andrew R.; Knott, Nathan A.

doi:10.1016/j.marenvres.2012.10.010

Cited by 62 publications

(53 citation statements)

References 36 publications

(47 reference statements)

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“…Seagrass was mostly present within the area defined as containing a scar, although it was very low in density, with canopy height reduced. The average distance from a mooring that was scarred was 5.4 m. This radial scar of 5.4 m is lower than those recorded for Posidonia australis (e.g., 9 m) (Demers et al, 2013). This smaller scarred area may reflect the greater capacity of Z. marina to recover relative to the more climax species P. australis , alternatively it could also be the result of differences in tidal regimes.…”

Section: Discussionmentioning

confidence: 59%

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Rocking the Boat: Damage to Eelgrass by Swinging Boat Moorings

et al. 2017

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Seagrass meadows commonly reside in shallow sheltered embayments typical of the locations that provide an attractive option for mooring boats. Given the potential for boat moorings to result in disturbance to the seabed due to repeated physical impact, these moorings may present a significant threat to seagrass meadows. The seagrass Zostera marina (known as eelgrass) is extensive across the northern hemisphere, forming critical fisheries habitat and creating efficient long-term stores of carbon in sediments. Although boat moorings have been documented to impact seagrasses, studies to date have been conducted on the slow growing Posidonia species’ rather than the fast growing and rapidly reproducing Z. marina that may have a higher capacity to resist and recover from repeated disturbance. In the present study we examine swinging chain boat moorings in seagrass meadows across a range of sites in the United Kingdom to determine whether such moorings have a negative impact on the seagrass Zostera marina at the local and meadow scale. We provide conclusive evidence from multiple sites that Z. marina is damaged by swinging chain moorings leading to a loss of at least 6 ha of United Kingdom seagrass. Each swinging chain mooring was found to result in the loss of 122 m2 of seagrass. Loss is restricted to the area surrounding the mooring and the impact does not appear to translate to a meadow scale. This loss of United Kingdom seagrass from boat moorings is small but significant at a local scale. This is because it fragments existing meadows and ultimately reduces their resilience to other stressors. Boat moorings are prevalent in seagrass globally and it is likely this impairs their ecosystem functioning. Given the extensive ecosystem service value of seagrasses in terms of factors such as carbon storage and fish habitat such loss is of cause for concern. This indicates the need for the widespread use of seagrass friendly mooring systems in and around seagrass.

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Section: Discussionmentioning

confidence: 59%

“…A range of other studies have also documented the impact of moorings on Posidonia spp. (Walker et al, 1989; Hastings et al, 1995; Demers et al, 2013). …”

Section: Introductionmentioning

confidence: 99%

Rocking the Boat: Damage to Eelgrass by Swinging Boat Moorings

et al. 2017

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“…Therefore, we expect a negative feedback whereby the lateral vegetation is increasingly vulnerable through the reduction of wave attenuation capacity. This negative feedback may be exacerbated when mooring occurs in meadows with weak meadow compactness and low shoot density (Milazzo et al 2004, Demers et al 2013. Therefore canopies fragmented with large gaps will likely be more vulnerable (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Moorings using anchors (anchoring) and fixed weights moorings (mooring) are one of the main causes of anthropogenic disturbances within seagrass meadows (Walker et al 1989, Hastings et al 1995, Montefalcone et al 2008, Boudouresque et al 2012, Demers et al 2013, Giakoumi et al 2015. Gaps caused by trawling and the anchoring of large boats have been found along the Mediterranean coast (Francour et al 1999, Leriche et al 2006) and nearshore mooring scars can increase the loss of sedimentary organic carbon stores (Serrano et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Impact of anthropogenically created canopy gaps on wave attenuation in a Posidonia oceanica seagrass meadow

Colomer¹,

Soler²,

Serra³

et al. 2017

Mar. Ecol. Prog. Ser.

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Fixed weights moorings, once removed, can create longitudinal gaps in seagrass meadows of different sizes, running perpendicular to the coast. We quantified the interactions between these longitudinal gaps and the hydrodynamic environment of the nearshore environment to determine their potential impact on seagrass meadow ecology. Within the meadow at leaf length distances from the edge, wave attenuation by the lateral vegetation next to the gap was approximately the same as attenuation by fully vegetated areas, and the wave attenuating capacity of the lateral, near-gap vegetation was independent of gap width. Gaps with widths less than twice the leaf length exhibited 8% wave attenuation and 11% turbulent kinetic energy attenuation, confirming that vegetation shelters at least small gaps. Despite similar capacity for wave attenuation, the longitudinal gaps influenced the architectural characteristics of the adjacent (lateral) meadow; lateral shoot density, percent cover and leaf length adjacent to the largest gap were 12, 16, and 20% lower than the fully vegetated site, respectively. Significant differences in the temporal variation of the mean lateral, near-gap seagrass percent cover and the leaf length indicated a strong dependence of the state of the canopy on temporal hydrodynamic conditions, which in turn were impacted by the presence of the gap. Our results quantify the interactions between gaps and lateral meadow vegetation, highlight the structural impact of traditional moorings and support improved management and conservation of seagrass meadows.

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“…For example, a local council responsible for a sub-catchment may identify that moorings within seagrass habitats are a risk factor for their sustainability and should be replaced with less damaging types or removed (Demers et al, 2013). However, responsibility for moorings is a state government agency.…”

Section: Continuedmentioning

confidence: 99%

Linking risk factors to risk treatment in ecological risk assessment of marine biodiversity

Astles

2014

ICES Journal of Marine Science

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Implementing marine ecosystem-based management at regional and small spatial scales is challenging due to the complexity of ecosystems, human activities, their interactions and multilayered governance. Ecological risk assessments (ERAs) of marine biodiversity are often used to prioirtise issues but only give broad guidance of how issues might be addressed in the form of strategies. However, at small and regional spatial scales marine natural resource managers have to make decisions within these strategies about how to manage specific interactions between human uses and ecological components. By using the transition between risk characterization and risk treatment in ERA for marine biodiversity tractable ways through the complexity can be found. This paper will argue that specific management and research actions relevant to smaller spatial scales can be developed by using the linkage between risk factors and risk treatment in ERA. Many risk factors require risk treatments that extend beyond the boundary of local agencies or sector responsibilities. The risk factor-treatment platform provides a practical way that these boundaries can be opened up by providing a scientifically based and transparent process to engage all actors who need to be involved in addressing the issues raised by an ERA. First, the principles of the mechanism will be described. Second, how the mechanism is constructed will be introduced using examples from an urban estuary. Application of the mechanism reveals three different types of risk factors (stressor, ecological, and knowledge gap) that can be used to develop specific management and research actions to treat risks. The systematic approach enables the dual complexities of marine ecosystems and multiple human pressures to be unravelled to identify and target issues effectively. The risk factor treatment linkage provides a platform to negotiate and develop effective management and research actions across jurisdictional, disciplinary, community and stakeholder boundaries.

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A comparison of the impact of ‘seagrass-friendly’ boat mooring systems on Posidonia australis

Cited by 62 publications

References 36 publications

Rocking the Boat: Damage to Eelgrass by Swinging Boat Moorings

Rocking the Boat: Damage to Eelgrass by Swinging Boat Moorings

Impact of anthropogenically created canopy gaps on wave attenuation in a Posidonia oceanica seagrass meadow

Linking risk factors to risk treatment in ecological risk assessment of marine biodiversity

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