Turtle herbivory in the seagrass ecosystems in the Lakshadweep atolls: concerns and need for conservation measures

Kaladharan, P; Saidkoya, K.P.; Kunhikoya, V A; Anasukoya, A.

doi:10.6024/jmbai.2013.55.1.01749-04

Cited by 11 publications

(12 citation statements)

References 16 publications

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“…The magnitude of decline of seagrass meadows in these lagoons can be viewed from the photographs taken in 2011 and 2015 (Figs. 2-6) The root: shoot ratio of seagrass plants sampled from the four Atolls as shown in Table 3 indicates higher biomass below the sediment than the shoot system comprising leaves, stem and bracts in Agatti, Chetlet and Kavaratti Atolls until 2013 which might be due to grazing by herbivores as reported by Kaladharan et al (2013). After 2013, even the root system consisting of roots and rhizomes also showed decline and showed low values of root: shoot ratio.…”

Section: Resultsmentioning

confidence: 76%

“…Primary productivity of seagrasses, their distribution and biology and decline due to herbivory in some Atolls of Lakshadweep Sea are understood extensively (Qasim and Bhattathiri, 1971;Kaladharan and David Raj, 1989;Nobi et al, 2011;Kaladharan et al, 2013). Growing coastal populations and increasing coastal developments threaten seagrass habitats globally and the loss in seagrass habitats is estimated to 29% (Duarte et al, 2010;Unsworth and Unsworth, 2013;Waycott et al, 2009).…”

Section: Shrinking Seagrass Meadowsobservations From Four Lagoons Of ...mentioning

confidence: 99%

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Shrinking seagrass meadowsobservations from four Lagoons of Lakshadweep Archipelago

Kaladharan¹,

Anasukoya²

2019

J. Mar. Biol. Ass. India

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Seagrass meadows worldwide are declining fast, taking with them many species which depend on these underwater prairies as their habitat and feeding as well as breeding grounds. Our results obtained on the biomass and density of seagrass vegetation in the reef and lagoons of Agatti, Chetlat, Kavaratti and Kiltan Islands of U.T. Lakshadweep, indicated gradual but steady shrinking of seagrass meadows. The percentage reduction in density of seagrass meadows since December 2011 to November 2015 was estimated at 88.5% in Agatti, 88.7% in Chetlat, 78.4% in Kavaratti and 81.3% in Kiltan. Wet biomass of parts below the sediment were always higher than the epigeal parts comprising leaves, stem and bracts. The possible reason behind this decline in seagrass biomass might be grazing, deterioration of water quality due to increased anthropogenic activities and climate change. This situation calls for urgent steps to monitor the ecology and physico-chemical parameters of water and sediment in the existing meadows and to undertake immediate habitat restoration programmes.

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Section: Resultsmentioning

confidence: 76%

Section: Shrinking Seagrass Meadowsobservations From Four Lagoons Of ...mentioning

confidence: 99%

Shrinking seagrass meadowsobservations from four Lagoons of Lakshadweep Archipelago

Kaladharan¹,

Anasukoya²

2019

J. Mar. Biol. Ass. India

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“…However new areas with seagrass presence are becoming evident, such as the recent report of H. beccarii from the coast of Kerala (Prabhakaran et al, 2020). However, due to increasing human-induced disturbances and coastal developments, the seagrass beds of India are under decline (Kaladharan et al, 2013;Mishra & Apte, 2020. In these scenarios, monitoring the current status of the various Indian seagrass beds is essential for the management and conservation of these ecosystems Ramesh et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Population structure of a newly recorded (Halodule uninervis) and native seagrass (Halophila ovalis) species from an intertidal creek ecosystem

et al. 2021

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The presence of the seagrass Halodule uninervis was documented for the first time outside the Chilika lagoon at Haripur creek, along with previously documented Halophila ovalis from the same region. The population structure (density; biomass; leaf growth rate; and morphometrics) and environmental parameters was assessed for both seagrass species. The pH levels of the water column above both seagrass meadows were lower than the standard oceanic pH of 8.2, likely attributable to upstream freshwater influences. Halophila ovalis grew on sandy and H. uninervis on silty substrates. High nutrient (nitrate and phosphate) concentrations in the water column of the creek influenced the growth of macroalgae (Ceramium sp. and Gracilaria verrucosa) on the leaves of H. uninervis. Leaf reddening was only observed in H. ovalis leaves. Under similar environmental conditions, the shoot density and biomass (above-and below-ground) of H. ovalis were 2-fold lower that for H. uninervis. The leaves of H. uninervis were 9-fold longer than H. ovalis, whereas H. ovalis had 5-fold wider leaves than H. uninervis. The leaf plastochrone interval of H. ovalis (2.3 days) and H. uninervis (9.6 days) was similar for the Indian Ocean region. Consequently, the H. ovalis leaf growth rate was 2-fold lower than that for H. uninervis. H. ovalis shoot internodes were 2.6-fold longer than for H. uninervis, whereas the root lengths of H. uninervis were longer than for H. ovalis.The shorter root length of H. ovalis resulted in a higher branching frequency than for H. uninervis. The total C and N content were higher in the H. ovalis leaves than those of H. uninervis. This study suggest seagrass responses to similar environmental conditions are species-specific. Regular assessment of the seagrass population structure and water quality monitoring of Haripur creek are essential for better management and conservation of these important seascapes.

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“…The drastic declines of large herbivores, like green turtles, manatees, and dugongs, caused by human overexploitation (Jackson 1997;Jackson 2001;Hughes et al 2004;Valentine & Duffy 2006) has contributed to the undervaluation of top-down controls in seagrass communities. In recent decades, conservation strategies have led to local increases in abundance of green turtles (Chelonia mydas), with noticeable impacts of turtle grazing on seagrass communities Kaladharan et al 2013;Kelkar et al 2013;Molina-Hernández & van Tussenbroek 2014). Herbivores, particularly large herbivores such as green turtles, can alter plant species composition and community structure (Lal et al 2010;Kelkar et al 2013;Molina-Hernández & van Tussenbroek 2014).…”

Section: Introductionmentioning

confidence: 99%

Peer Review #2 of "Nutrient availability induces community shifts in seagrass meadows grazed by turtles (v0.1)"

2019

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In the Caribbean, green turtles graze seagrass meadows dominated by Thalassia testudinum through rotational grazing, resulting in the creation of grazed and recovering (abandoned) patches surrounded by ungrazed seagrasses. We evaluated the seagrass community and its environment along a turtle grazing gradient; with the duration of (simulated) grazing as a proxy for the level of grazing pressure. The grazing levels consisted of Short-term (4 months clipping), Medium-term (8 months clipping), Long-term grazing (8 months of clipping in previously grazed areas), 8-months recovery of previously grazed patches, and ungrazed or unclipped patches as controls. We measured biomass and density of the seagrasses and rhizophytic algae, and changes in sediment parameters. Medium-and Long-term grazing promoted a shift in community species composition. At increasing grazing pressure, the total biomass of T. testudinum declined, whereas that of early-successional increased. Ammonium concentrations were highest in the patches of Medium-term (9.23 + 0.78 µM) and Long-term grazing levels (10.96 + 2.16 µM) and were lowest in the control areas (4.65 + 1.48 µM). T. testudinum is a late-successional species that maintains sediment nutrient concentrations at levels below the requirements of earlysuccessional species when dominant. When the abundance of this species declines due to grazing, these resources become available, likely driving a shift in community composition towards a higher abundance of early-successional species.

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Turtle herbivory in the seagrass ecosystems in the Lakshadweep atolls: concerns and need for conservation measures

Cited by 11 publications

References 16 publications

Shrinking seagrass meadowsobservations from four Lagoons of Lakshadweep Archipelago

Shrinking seagrass meadowsobservations from four Lagoons of Lakshadweep Archipelago

Population structure of a newly recorded (Halodule uninervis) and native seagrass (Halophila ovalis) species from an intertidal creek ecosystem

Peer Review #2 of "Nutrient availability induces community shifts in seagrass meadows grazed by turtles (v0.1)"

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