Impact of sea surface temperature anomalies on giant clam population dynamics in Lakshadweep reefs: Inferences from a fourteen years study

Apte, Deepak; Narayana, Sumantha; Dutta, Sutirtha

doi:10.1016/j.ecolind.2019.105604

Cited by 17 publications

(9 citation statements)

References 35 publications

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“…Also, the decline in giant clam abundances might be attributed to the global sea surface temperature anomalies that have led to global coral bleaching events (Eakin, Sweatman & Brainard, 2019). Bleaching of giant clams that coincided with these events have been reported elsewhere (Addessi, 2001;Tun et al, 2013;Van Wynsberge et al, 2018;Apte, Narayana & Dutta, 2019;Mies, 2019), and in some instances, the populations in some areas experienced high mortalities post-bleaching (e.g. Junchompoo et al, 2013;Andréfouët et al, 2018;Ramah et al, 2019).…”

Section: Status Of Giant Clams In the Pmpmentioning

confidence: 89%

“…Junchompoo et al, 2013; Andréfouët et al, 2018; Ramah et al, 2019). Globally, recovery of giant clam population sizes is already generally slow owing to exploitation, overfishing and habitat degradation (Teitelbaum & Friedman, 2008; Neo et al, 2017); frequent sea surface temperature anomalies are also expected to further compromise the viability of giant clam populations (Apte, Narayana & Dutta, 2019). Coral reef bleaching has been reported in PMP and other parts of Malaysian reefs (Tan & Heron, 2011; Guest et al, 2012; Tun et al, 2013); however, to our knowledge, no study has confirmed the impacts of such events on giant clam populations in Malaysia.…”

Section: Discussionmentioning

confidence: 99%

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Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

Lee

Neo

Lim

et al. 2022

Aquatic Conservation

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1. With the increasing demand for giant clams in the ornamental trade as well as habitat destruction of coral reefs, giant clam populations have been threatened across the Indo-Pacific. This study documents the population status and genetic diversity of giant clams in Perhentian Islands Marine Park (PMP), a Marine Protected Area (MPA) on the east coast of Peninsular Malaysia, plus Rhu Island, an adjacent island outside the MPA.2. Of the 13 reef sites surveyed across an area of 11,200 m 2 , two giant clam species were recorded: Tridacna squamosa and Tridacna maxima, with average densities of 1.5 ± 2.2 and 5.2 ± 6.0 ind. 100 m À2 , respectively. The size-class survey revealed a higher number of T. maxima recruits (88 recruits) as compared to T. squamosa (only three recruits), suggesting a disparity in recruitment in the area.3. The genetic diversity of T. squamosa (n = 83) and T. maxima (n = 104) was explored using the mitochondrial cytochrome c oxidase I (COI) and 16S rRNA gene markers. Interestingly, a higher genetic diversity was detected in COI than 16S for both species. No significant genetic differentiation was detected between the populations of PMP and Rhu Island, while a low but significant genetic structure was detected in both species across the sites of PMP (COI datasets, AMOVA, T. squamosa, F CT = 0.14, P < 0.05; T. maxima, F CT = 0.11, P < 0.05).4. In general, the results of this study revealed healthy giant clam populations in PMP, but the decline warrants urgent attention to integrating conservation strategies such as restoration programmes in conjunction with a sustainable giant clam fishery. Given the relatively high genetic diversity of T. maxima at Rhu Island, expansion of the current MPA is needed for better conservation coverage.

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Section: Status Of Giant Clams In the Pmpmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

Lee

Neo

Lim

et al. 2022

Aquatic Conservation

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“…Like corals, giant clams bleach in response to high temperatures and high light intensities ( Buck et al , 2002 ), with documented cases of bleaching in giant clams in the wild from high temperatures (e.g. Addessi, 2001 ; Andréfouët et al , 2018 ; Apte et al , 2019 ). Elevated seawater temperature also changes fatty acid composition in T .…”

Section: New Conservation Considerations In a Rapidly Changing Worldmentioning

confidence: 99%

Conserving threatened species during rapid environmental change: using biological responses to inform management strategies of giant clams

Watson

Neo

2021

Conservation Physiology

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Giant clams are threatened by overexploitation for human consumption, their valuable shells and the aquarium trade. Consequently, these iconic coral reef megafauna are extinct in some former areas of their range and are included in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and Convention on International Trade in Endangered Species of Wild Fauna and Flora. Now, giant clams are also threatened by rapid environmental change from both a suite of local and regional scale stressors and global change, including climate change, global warming, marine heatwaves and ocean acidification. The interplay between local- to regional-scale and global-scale drivers is likely to cause an array of lethal and sub-lethal effects on giant clams, potentially limiting their depth distribution on coral reefs and decreasing suitable habitat area within natural ranges of species. Global change stressors, pervasive both in unprotected and protected areas, threaten to diminish conservation efforts to date. International efforts urgently need to reduce carbon dioxide emissions to avoid lethal and sub-lethal effects of global change on giant clams. Meanwhile, knowledge of giant clam physiological and ecological responses to local–regional and global stressors could play a critical role in conservation strategies of these threatened species through rapid environmental change. Further work on how biological responses translate into habitat requirements as global change progresses, selective breeding for resilience, the capacity for rapid adaptive responses of the giant clam holobiont and valuing tourism potential, including recognizing giant clams as a flagship species for coral reefs, may help improve the prospects of these charismatic megafauna over the coming decades.

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“…Occasionally, however, the temperature in shallow waters can become very high, especially during the summer months, which can potentially cause bleaching (i.e., the expulsion of the symbiotic microalgae) by the clams (Addessi, 2001;Leggat et al, 2003). Additionally, high water temperatures have been previously shown to result in lower overall survival of Tridacninae larvae (Neo et al, 2013;Enricuso et al, 2018) and a general increase in mortality (Addessi, 2001;Junchompoo et al, 2013;Apte et al, 2019). Indeed, we also identified water temperature as a potential driver influencing the densities of Tridacna spp.…”

Section: Drivers For Abundances Of Tridacna Spp In the Red Seamentioning

confidence: 99%

“…The recently described, strong light-dependency of calcification in Red Sea giant clams (Rossbach et al, 2019), may therefore be among the main drivers which restrict the depth-distribution of Tridacninae within the reef. In addition to the availability of light, sea temperatures (Apte et al, 2019) and wave exposure are also important environmental factors for symbiotic benthic organisms (Williams et al, 2013), and are potentially impacting the overall abundances of Tridacninae. Other habitat parameters, for example the substrate and overall geomorphology of the reef could influence larval settlement success, as giant clam larvae have been reported to favor high substrate rugosity (e.g., on coral rubble) to settle (Alcazar and Solis, 1986;Neo et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Drivers of the Abundance of Tridacna spp. Giant Clams in the Red Sea

2021

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Giant clams (Subfamily Tridacninae), are important members of Indo-Pacific coral reefs, playing multiple roles in the framework of these communities. Although they are prominent species in Red Sea reefs, data on their distribution and densities in the region are scarce. The present study provides the first large-scale survey of Red Sea Tridacna spp. densities, where we examined a large proportion of the Saudi Arabian Red Sea coast (1,300 km; from 18° to 29°N). Overall, Tridacninae were found at densities of 0.19 ± 0.43 individuals m–2 (±SD). Out of the total 4,002 observed clams, the majority (89%) were Tridacna maxima, with 0.17 ± 0.37 individuals m–2, while only 11% were Tridacna squamosa clams with 0.02 ± 0.07 individuals m–2. We also report on a few (total 6) Tridacna squamosina specimens, found at a single reef. We identified different geographical parameters (i.e., latitude and distance to shore) and local environmental factors (i.e., depth and reef zone) as the main drivers for local Tridacna spp. densities. Our results show that the drivers influencing the densities of Red Sea giant clams are complex due to their co-occurrence and that this complexity might explain the high variation in Tridacninae abundances across the Indo-Pacific, but also within a given reef. We also estimate that giant clam calcification likely contributes to an average of 0.7%, but potentially up to 9%, of the overall mean calcium carbonate budget of Red Sea coral reef communities.

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Impact of sea surface temperature anomalies on giant clam population dynamics in Lakshadweep reefs: Inferences from a fourteen years study

Cited by 17 publications

References 35 publications

Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

Conserving threatened species during rapid environmental change: using biological responses to inform management strategies of giant clams

Drivers of the Abundance of Tridacna spp. Giant Clams in the Red Sea

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