Spatial variation in reproductive effort of a southern Australian seagrass

Smith, Timothy M.; York, Paul H.; Macreadie, Peter I.; Keough, Michael J.; Ross, D. J.; Sherman, Craig D. H.

doi:10.1016/j.marenvres.2016.08.010

Cited by 24 publications

(20 citation statements)

References 58 publications

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“…However, there is growing recognition that the long-term persistence of species depends to some extent on sexual reproduction, as even low rates of recruitment may provide evolutionary potential and increased resistance/resilience to environmental alterations (Reusch et al, 2005; Ehlers et al, 2008; Reynolds et al, 2012; Kendrick et al, 2016). Recruitment by seed also plays a role in colonizing new habitats or recolonizing following local extinction, and contributes to patch expansion in some species (Orth et al, 2006; van Dijk et al, 2009; Kendrick et al, 2012; McMahon et al, 2014; Furman et al, 2015; Sherman et al, 2016; Smith et al, 2016). Some authors argue that the protection of areas that are sources of sexual propagules or that receive high seed inputs, or both, should be a conservation priority (Kenworthy et al, 2006; Orth et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Recruitment and Patch Establishment by Seed in the Seagrass Posidonia oceanica: Importance and Conservation Implications

2017

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Seagrasses are declining globally, and deeper understanding is needed on the recruitment potential and distribution of new populations for many threatened species to support conservation planning in the face of climate change. Recruitment of Posidonia oceanica, a threatened seagrass endemic to the Mediterranean, has long been considered rare due to infrequent flowering, but mounting evidence demonstrates that the species is responding to a changing climate through greater reproductive effort. Due to the fragmentary information on recruit occurrence and distribution, little is known about reproductive success in the species and its contribution to persistence. We assembled P. oceanica recruitment data from published and unpublished sources, including our own, to examine the frequency and extent of recruitment events (establishment of seedlings in a site), seedling growth potential and habitat characteristics at recruitment sites. Results show that at least one recruitment event has occurred about every 3 years, and 18 localities were colonized at least one time since the first seedling record in 1986. Notably, consistently high seedling inputs were observed in four localities of the Western Mediterranean. Seedlings established mainly on unoccupied substrate areas along the coasts of islands, in sheltered sites and at shallower depths (<3 m) than the upper limit of adjacent P. oceanica meadows. Seedling establishment occurred more frequently on rocky than on sandy substrate, and rarely on dead “matte” or meadows of the seagrass Cymodocea nodosa. The chance of colonization success on rock was two times higher than on sand. Our 11 years of observations have allowed for the first time the documentation of the formation and development of patches by P. oceanica seed. These findings contradict the historical assumption that sexual recruitment is rare and usually unsuccessful for P. oceanica, and highlight the potential importance of recruitment for the long-term persistence and adaptation of the species to sea level rise predicted in the next century in the Mediterranean. Unfortunately, management actions have mainly focused on established meadows, ignoring the presence of recruits in outside areas. Therefore, it will be useful to identify and consider regeneration sites in designing future management strategies to improve seagrass conservation effectiveness.

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Section: Introductionmentioning

confidence: 99%

Recruitment and Patch Establishment by Seed in the Seagrass Posidonia oceanica: Importance and Conservation Implications

2017

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“…Temperature and salinity values used in this study were chosen to reflect the range within Port Phillip Bay. Peak flowering in Z. nigricaulis occurs during October and November each year (Smith et al, 2016b), which coincides with mean seawater temperatures between 13 °C and 17 °C. Once germinated, seedling growth may be rapid at this time of the year as temperatures and daylight increase moving into the Austral summer.…”

Section: Discussionmentioning

confidence: 91%

“…Like many plant species seagrasses invest large amounts of energy into the production of seeds often producing vast quantities that enter the seed bank (e.g., Smith et al, 2016b). Seed banks are important for recovery and maintenance in many ecosystems that are susceptible to local habitat loss.…”

Section: Discussionmentioning

confidence: 99%

“…Zostera nigricaulis flowering shoots with mature spadices were collected in December 2012, during the period of maximum seed production (Smith et al, 2016b), from Blairgowrie (38°21′47″S, 144°47′28″E) in Port Phillip Bay, Victoria, Australia (Fig. S1).…”

Section: Methodsmentioning

confidence: 99%

“…Recent studies have described Z. nigricaulis life history and the role seeds play in meadow maintenance (Smith et al, 2016a; Smith et al, 2016b; Thomson et al, 2015). The aim of this study was to add to this knowledge base by determining optimal germination conditions for Z. nigricaulis under controlled laboratory conditions by quantifying time to germination and maximum germination of seeds across a range of temperature, salinity, burial depths and sediment conditions.…”

Section: Introductionmentioning

confidence: 99%

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Seed germination in a southern Australian temperate seagrass

Cumming

Jarvis

Sherman

et al. 2017

PeerJ

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In a series of experiments, seeds from a temperate seagrass species, Zostera nigricaulis collected in Port Phillip Bay, Victoria, Australia were exposed to a range of salinities (20 PSU pulse/no pulse, 25 PSU, 30 PSU, 35 PSU), temperatures (13 °C, 17 °C, 22 °C), burial depths (0 cm, 1 cm, 2 cm) and site specific sediment characteristics (fine, medium, coarse) to quantify their impacts on germination rate and maximum overall germination. In southern Australia the seagrass Z. nigricaulis is a common subtidal species; however, little is known about the factors that affect seed germination which is a potential limiting factor in meadow resilience to natural and anthropogenic disturbances. Overall seed germination was low (<20%) with germination decreasing to <10% when seeds were placed in the sediment. When germination of Z. nigricaulis seeds was observed, it was enhanced (greater overall germination and shorter time to germination) when seeds were exposed to a 20 PSU pulse for 24 h, maintained at salinity of 25 PSU, temperatures <13 °C, in sediments with fine or medium grain sand and buried at a depth of <1 cm. These results indicate that germination of Z. nigricaulis seeds under in situ conditions may be seasonally limited by temperatures in southern Australia. Seed germination may be further restricted by salinity as freshwater pulses reaching 20 PSU are typically only observed in Port Phillip Bay following large scale rainfall events. As a result, these populations may be particularly susceptible to disturbance with only a seasonally limited capacity for recovery.

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Environmental drivers of flowering in the genus Zostera and spatio‐temporal variability of Zostera muelleri flowering in Australasia

Lekammudiyanse,

Saunders,

Flint

et al. 2024

Aquatic Conservation

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Seed‐based seagrass restoration strategies demand precise understanding of the environmental drivers influencing flowering. Flowering varies across diverse spatial and temporal scales, yet environmental drivers' effects on these dynamics have received less attention. Lack of knowledge regarding this life‐history stage limits the advancement of seed‐based restoration efforts, especially the establishment of shore‐based seagrass nurseries to enhance seed production. A systematic literature review on the flowering of the genus Zostera was conducted to develop a conceptual model that links influential environmental drivers with flowering. Additionally, a case study using existing survey data supplemented by additional field surveys was designed to explore the spatio‐temporal variability of flowering along the latitudinal gradient in Australasia for the species Zostera muelleri. Predictive models for flowering times were developed using regional climatic variables, following hypotheses generated from long‐term mesocosm observations. The review identified the direct and/or indirect effects of temperature, light, tidal variation, nutrients, salinity and grazing pressure on flowering dynamics. Four categories of flowering variables were identified based on their implications on restoration, namely, timing, abundance, the ratio between reproductive and vegetative growth and morphological characteristics. The spathe densities varied significantly among sites along the latitudinal gradient. While first (r2 = 0.71) and peak (r2 = 0.68) flowering times showed significant correlation with latitude, first flowering was equally predicted by mean winter air temperature and mean winter solar radiation (r2 = 0.73), whereas peak flowering time was best predicted by mean winter air temperature (r2 = 0.60). Accurate predictions of flowering times can improve conservation outcomes by enabling restoration practitioners to forecast flowering times and subsequent wild seed harvesting. The strong correlation between flowering times and climatic variables suggests future shifts in flowering times under climate change are likely, which is crucial knowledge for maintaining the contribution of restoration projects to seagrass conservation.

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Spatial variation in reproductive effort of a southern Australian seagrass

Cited by 24 publications

References 58 publications

Recruitment and Patch Establishment by Seed in the Seagrass Posidonia oceanica: Importance and Conservation Implications

Recruitment and Patch Establishment by Seed in the Seagrass Posidonia oceanica: Importance and Conservation Implications

Seed germination in a southern Australian temperate seagrass

Environmental drivers of flowering in the genus Zostera and spatio‐temporal variability of Zostera muelleri flowering in Australasia

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