Evolution and Biogeography of Seagrasses

Larkum, Anthony W. D.; Waycott, Michelle; Conran, John G.

doi:10.1007/978-3-319-71354-0_1

Cited by 33 publications

(27 citation statements)

References 97 publications

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“…Halophila stipulacea is a tropical and sub-tropical seagrass species widely distributed in the Indian Ocean and the Red Sea (Larkum and den Hartog 1989). However, it colonized the Eastern Mediterranean basin following the opening of the Suez Canal, and from there it spread into the Southern and Western Mediterranean (van der Velde and den Hartog 1992; Boudouresque and Verlaque 2002;Gambi et al 2009;Sghaier et al 2011).…”

mentioning

confidence: 99%

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

Cardini

Hoytema

Bednarz

et al. 2017

Limnology & Oceanography

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The tropical seagrass Halophila stipulacea exhibits a limited capacity to use nitrate, but has a high uptake capacity and efficiency for ammonium. Consequently, N 2 fixation by associated diazotrophic epiphytes may be important in providing ammonium needed for seagrass photosynthesis and growth. When exposed to seasonality, this association could provide a competitive advantage for H. stipulacea in relation to other seagrass species, but related knowledge is scarce. Here, we thus report measurements of net photosynthesis (O 2 fluxes) and N 2 fixation (acetylene reduction) associated with H. stipulacea from the Northern Red Sea over all four seasons of 2013. In parallel, we characterized the seagrass meadow areal extent, shoot and leaves density, and the leaf area index. Using this data, we quantified meadow net primary production and N 2 fixation and estimated the photo-metabolic N demand met by N 2 fixation at the community level. Results revealed a marked seasonality of meadow N 2 fixation, with rates ranging from 0.06 in winter to 4.60 mmol N m 22 d 21 in summer, i.e., an increase by two orders of magnitude. In summer, when nutrient concentrations in the water column were lowest and light intensity and temperature highest, there was a significant positive linear relationship between meadow net primary production and N 2 fixation, with the latter accounting for ca. 20% of the photo-metabolic N demand. These findings suggest that N 2 fixation by associated diazotrophic epiphytes can mitigate N limitation of H. stipulacea meadows under N scarcity. This trait may also favor the ongoing geographical expansion of H. stipulacea.

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mentioning

confidence: 99%

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

Cardini

Hoytema

Bednarz

et al. 2017

Limnology & Oceanography

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“…Actuellement, 68 espèces de phanérogames marines ont été décrites (Larkum et al, 2006). Toutefois, certaines font encore l'objet de recherches génétiques et morphométriques, et beaucoup sont considérées comme conspécifiques.…”

Section: Taxonomieunclassified

“…Cette classification est donc susceptible de subir des remaniements, tant dans la taxonomie que dans la nomenclature . Le tableau 1 présente l'ensemble des espèces décrites (Larkum et al, 2006) qui sont exclusivement marines : les trois espèces d'eau saumâtre (Ruppia tuberosa, Ruppia maritima et Lepilaena marina) ne sont pas prises en compte. Parmi l'ensemble des espèces de phanérogames exclusivement marines, 19 d'entre elles sont présentes en Outre-mer français, soit 8 genres et 4 familles.…”

Section: Taxonomieunclassified

“…Les organes floraux tout comme le mode de fertilisation sont variés, la dioécie et monoécie sont présentes selon les espèces, soutenant les hypothèses de plusieurs origines différentes pour les ancêtres des phanérogames actuelles (Larkum & den Hartog, 1989).…”

Section: Reproductionunclassified

“…Le métabolisme global des herbiers affecte la dynamique du carbone et des sels nutritifs dans les milieux côtiers, ainsi que les concentrations d'oxygène dans la colonne d'eau et les sédiments (Larkum et al, 2006 ;Borum et al, 2004). La structure de la canopée des feuilles d'herbiers ralentit les courants et atténue l'impact des vagues, augmentant ainsi la sédimentation des particules en suspension, et diminue leur remise en suspension.…”

Section: Grands Traits De L'habitat Herbierunclassified

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Drivers of change in the relative abundance of dugongs in New Caledonia

et al. 2017

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Context Sound understanding of temporal changes in the abundance of wildlife species is required for assessing their status and for effective conservation and management. In New Caledonia, a single baseline aerial survey of dugongs in 2003 estimated a population of 2026 (± 553 s.e.) individuals. A second, similar survey in 2008 produced a lower estimate of 606 (± 200 s.e.) individuals, leading to concerns that the dugong population was experiencing a decline. Aims This study used data collected from additional aerial surveys with the aim of updating information on the current size of the dugong population in New Caledonia and investigating the drivers of change in the estimates. Methods Four additional surveys were conducted: one in each of the cool (June) and warm (November) seasons of 2011 and 2012 around the main Island of New Caledonia. Dugong relative abundance and density were calculated and compared among survey years and survey regions. Drivers of change in the dugong population size were then investigated. Key results The abundance estimates obtained from our four surveys ranged from 649 (± 195 s.e.) to 1227 (± 296 s.e.) dugongs. These new results were not significantly different to the 2008 estimate but were significantly lower than the 2003 estimate. There was no significant variation in the proportion of calves throughout the entire time series of surveys. Conclusions The dugong population of New Caledonia was relatively stable between 2008 and 2012. We could not find sufficient evidence to show whether the discrepancy between 2003 and the remainder of the time series is due to a real decline in the population or the result of the confounding effects of variation in environmental conditions, animal behaviour and sampling biases. Implications The stability of the dugong population between 2008 and 2012 is a positive outcome for local conservation and management of dugongs. This study also highlights the advisability of replicating baseline surveys to enable robust interpretation of temporal variation in population size estimates, and in turn, to improve the management of wildlife species.

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Biogeography and Origins

2021

Tropical Marine Ecology

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Evolution and Biogeography of Seagrasses

Cited by 33 publications

References 97 publications

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

Drivers of change in the relative abundance of dugongs in New Caledonia

Biogeography and Origins

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Evolution and Biogeography of Seagrasses

Cited by 33 publications

References 97 publications

N2 fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

N2 fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

Drivers of change in the relative abundance of dugongs in New Caledonia

Biogeography and Origins

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N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

N₂ fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality