Southeast Asia has been affected by fluctuating sea-levels and reversing monsoon winds, which have contributed to the Holocene lagoon infill in the region. This has become a subject of scientific research, and a recent study published in Scientific Reports sheds light on the link between sea level changes, monsoon winds, and the sedimentation of lagoons in Southeast Asia. The research highlights the importance of understanding the geological history of the region and its impact on the environment, which has significant implications for coastal communities and wildlife in the area.
The formation and evolution of coral reef islands in the Maldives have been the focus of various studies that aim to understand the controls and processes that contribute to their development. A team of researchers led by C.T. Perry investigated the time scales and modes of reef lagoon infilling and identified the factors that determine the onset of reef island formation. Their findings, published in Geology in 2013, shed light on the complex interplay between sea level changes, sedimentation, and coral growth in the Maldives.
The study by Perry and colleagues drew on previous research in the region, including E.G. Purdy and E. Gischler’s work on the transient nature of the empty bucket model of reef sedimentation in 2005, and H. Yamano, H. Kayanne, F. Matsuda, and Y. Tsuji’s analysis of lagoonal facies, ages, and sedimentation in three atolls in the Pacific in 2002.
The researchers used radiocarbon dating and sediment analyses to assess the accumulation rates and composition of reef lagoon sediments in the Maldives over the last several thousand years. They found that infilling of reef lagoon spaces occurred in a cyclical pattern, with periods of rapid sedimentation alternating with intervals of low accumulation. They also observed that the onset of reef island formation was closely tied to the cessation of lagoon infilling and a shift to more aggradational processes.
In a related study, P.S. Kench, R.F. McLean, and S.L. Nichol proposed a new model of reef-island evolution in the Maldives in 2005. Their hypothesis centered on the idea that reef islands grow and evolve through three distinct stages: initial formation, steady state, and senescence. They argued that the timing and rate of island development depend on factors such as sea level changes, sediment supply, and coral growth patterns.
In another recent study, L. Klostermann and E. Gischler analyzed the Holocene sedimentary evolution of a mid-ocean atoll lagoon in the Maldives. Using sediment cores and radiocarbon dating, they reconstructed the changing depositional environments of the lagoon over the last 8,000 years. They found that the atoll lagoon underwent periods of high sedimentation and accretion, followed by episodes of lower accumulation rates and reworking of older sediments.
Meanwhile, D.L. Harris and colleagues challenged the classic “bucket fill” model of coral reef growth in 2015, which states that reef flat carbonate production continually fills up the lagoon space and creates a platform that allows for upward accretion of sediment. They argued that this model is too simplistic and ignores the critical role of sea level changes and other environmental factors in shaping reef growth and sedimentation patterns.
Similarly, M.J. O’Leary and C.T. Perry suggested an alternative model for reef accretion on the Rodrigues carbonate platform in 2010. They proposed that reef island formation was not solely driven by a “bucket fill” process, but rather by the interplay between sea level changes, coral growth, and sediment transport and erosion.
Recent studies have also explored the impact of sea level rise on reef island systems in the Maldives and other regions. E.K. East and colleagues modeled reef hydrodynamics and sediment mobility under sea level rise in atoll reef island systems in 2020. They found that changes in current flow patterns and sediment transport could significantly alter reef island morphology and stability.
Another study by A.E. Grady and colleagues examined the influence of sea level rise and changes in fringing reef morphology on gradients in alongshore sediment transport. They found that larger waves and increased currents caused by sea level rise could lead to greater sediment erosion and transport, potentially putting reef islands at risk.
In a recent publication, P.S. Kench and T. Mann provided insights into the reef island evolution and dynamics of the Spermonde archipelago and compared them with previous research findings from the Indian and Pacific oceans.
Researchers have also investigated the impact of human activities on coral reef ecosystems in the Maldives. A.B. Birawida and A. Faisal developed a water quality index of island wells in Makassar City in 2019, while M. Wijsmann-Best, H. Moll, and L.G. de Klerk assessed the present status of coral reefs in the Spermonde Archipelago in 1981.
Overall, the research on reef island formation and evolution in the Maldives has provided valuable insights into the complex processes that contribute to the development and stability of these island systems. By examining factors such as sea level changes, sedimentation rates, and coral growth patterns, researchers are gaining a better understanding of the interplay between natural and human-driven processes that shape these unique ecosystems.
