Coral Islands Research Articles

Temporal and Spatial Variabilities of Chemical and Physical Parameters on the Heron Island Coral Reef Platform

Temporal and Spatial Variabilities of Chemical and Physical Parameters on the Heron Island Coral Reef Platform

Influence of Land Reclamation on Fresh Groundwater Lenses in Oceanic Islands: Laboratory and Numerical Validation

AbstractFresh groundwater lenses in tropic oceanic islands are important freshwater resources for local inhabitants and ecosystems. These reef‐carbonate islands typically have a dual‐aquifer structure, with poorly consolidated Holocene sediments deposited unconformably on Pleistocene limestone reef deposits. Land reclamation has been carried out on the reef flats or shallow water areas in coral islands, a very common practice in the Indian Ocean and the South China Sea. However, there is a lack of comprehensive understanding of how the groundwater system will respond to land reclamation. In this study, the impact of land reclamation on the fresh groundwater lens in an island is investigated using multiple methods: sand‐tank experiments, sharp‐interface analytical solutions, and numerical modeling. This study demonstrates that land reclamation can increase the freshwater storage of the lens and shift the water divide toward the reclamation area. Furthermore, a lower permeability fill material especially with a greater scale or thickness leads to higher freshwater storage. However, the expansion of the lens will be truncated due to the high‐permeability of the lower layer. These observations and findings from the laboratory experiments and two‐dimensional numerical simulations are further ground‐truthed by the three‐dimensional modeling of Yongxing Island in the South China Sea. The findings of this study provide a comprehensive understanding of the impact of land reclamation on island groundwater system and the theoretical supports for Small Island Developing States to use the reclamation not only for urban development but also for extra aquifer to enhance the water resource sustainability under the climate change.

Which traits are necessary to quickly select suitable plant species for ecological restoration?

Abstract Traditionally, restoration ecologists and land managers have used the trial‐and‐error method to select candidate restoration species. This method, however, is time consuming (usually more than 3 years) and has a relatively low success rate. Recently, Wang et al. (2020) developed a trait‐based species selection framework which can quickly (within 1 month) and successfully select many appropriate species for ecological restoration. They used 28 traits that are associated with tolerance to harsh environmental conditions to select candidate restoration species for a tropical coral island in Hainan Province, China. However, it is likely that some of the 28 traits used in this study may not be very important for species selection, providing the potential use of fewer overall traits. This is important since in many situations land managers will have limited data and resources on species traits. In this study, we used Wang et al. (2020)’s trait data to test which traits are necessary to achieve a similar success rate when screening species for restoration applications. We performed principal component analysis (PCA) to compute each trait's relative contribution. Then, we used the backward stepwise approach where the trait that had the least contribution among all remaining traits was removed one at a time, and the screening model was then run again using the smaller set of traits. Species which are proven very appropriate for ecological restoration in Wang et al. (2020) were the standard to quantify how many and which traits should be used to acquire similar screening results. We also classified all 28 traits into four types of functional traits to test if a small set of traits can mimic Wang et al. (2020)’s selection results. Our results indicate that it is hard to simultaneously reduce trait numbers and maintain the right screening results; especially for tree species. Likewise, vine species and herbaceous species still required most of the original traits used by Wang et al. (2020). Our results also indicate that multiple trait types are required, rather than one single group of functional traits. Our results reject the possibility of using fewer and more targeted traits for species screening. Although investigations in other ecosystems are needed to test the generality of the conclusion, our results suggest that multiple functional traits are still required to be measured to select appropriate plant species for the restoration of tropical coral islands.

“I Wonder Which of You is Real”

Abstract In response to Judith Yaross Lee's introduction of a framework designed to probe the relationship between empire and American humor, this article analyzes John Kneubuhl's “The Night of the Two-Legged Buffalo,” a 1966 episode of The Wild Wild West (1965-69). Kneubuhl (1920-92) was a Samoan American playwright who wrote for theater, television, and film. Like Mark Twain, he demonstrated a lifelong interest in the trope of the confidence man. In “The Night of the Two-Legged Buffalo” he depicts protagonists and antagonists alike in the US borderlands as con artists contending for power. While agents Jim West and Artemus Gordon emerge as cultural impersonators who serve the ideology of Manifest Destiny, the Prince of the South Sea Coral Islands, a Polynesian aristocrat, deploys American hegemony in Oceania. Kneubuhl draws on conventions of the fale aitu, a Samoan theatrical genre, as well as his association with Sam Amalu, a Native Hawaiian humorist and con man known for his elaborate pranks and swindles. As a site of contest between what Lee terms “neocolonial hybridity” and “postcolonial discontinuity,” “The Night of the Two-Legged Buffalo” exemplifies Kneubuhl's unique trickster aesthetics.

Indigenous maize seed storage using buffalo dung ash practiced by smallholder farmers in Kisar Island

Kisar island is a small island located on the tip of Timor island. Corn is the main agricultural crop, and livestock husbandry also plays an important role in the livelihood of the farmers as a source of income, provide mainly manure for maintaining soil fertility. and in the local culture as a 'bride price' and for the exchange of goods. Considering periodical seasonal hazards, during eight months dry season people suffer from a serious shortage of water. Failure of the harvest is not an unusual phenomenon on the small, dry, eroded coral island. Seasonal pest invasion on maize cultivation threaten their seed security and food security. The objective of this review is to describe the validity of farmers’ indigenous knowledge (IK) of using buffalo dung as a preservative agent in maize storage and its relevancy in the contemporary living of farmers in the island. A phenomenological study was held in June to August 2018. The results showed that applying buffalo dung ash makes the maize dry faster, cleans and kills maize weevil and preserves the grain, It was concluded that the knowledge and practice is scientifically valid and benefited community in the past but has less relevancy to the contemporary living of the farmers in the island.

“I Wonder Which of You is Real”

Abstract In response to Judith Yaross Lee's introduction of a framework designed to probe the relationship between empire and American humor, this article analyzes John Kneubuhl's “The Night of the Two-Legged Buffalo,” a 1966 episode of The Wild Wild West (1965-69). Kneubuhl (1920-92) was a Samoan American playwright who wrote for theater, television, and film. Like Mark Twain, he demonstrated a lifelong interest in the trope of the confidence man. In “The Night of the Two-Legged Buffalo” he depicts protagonists and antagonists alike in the US borderlands as con artists contending for power. While agents Jim West and Artemus Gordon emerge as cultural impersonators who serve the ideology of Manifest Destiny, the Prince of the South Sea Coral Islands, a Polynesian aristocrat, deploys American hegemony in Oceania. Kneubuhl draws on conventions of the fale aitu, a Samoan theatrical genre, as well as his association with Sam Amalu, a Native Hawaiian humorist and con man known for his elaborate pranks and swindles. As a site of contest between what Lee terms “neocolonial hybridity” and “postcolonial discontinuity,” “The Night of the Two-Legged Buffalo” exemplifies Kneubuhl's unique trickster aesthetics.

An assessment of small islands coral cover and coral-reef fish diversity at Oba Sub-district, Halmahera Island

Study on the percentage of coral cover four small islands of Oba Sub-district, Halmahera Island of North Maluku Utara Province was carried out in April 2021.The four small islands of Oba Sub-district studied are Woda Island, Raja Island, Tamin Island, and Guratu Island. The study applied systematic sampling method that included collecting coral reef data using UPT (Underwater Photo Transect) method and coral fish data collection using visual census method. Study results showed that live coral coverage of reefs on the four small islands of Oba Sub-district had the highest value of 5.415% and the lowest value of 4.29%. There was positive relationship between coral growth form diversity and fish diversity. High diversity of coral growth forms was significantly related to high diversity of target reef fish.

Numerical simulations on seismic response of soil-pile-superstructure in coral sand

The structures on the coral islands are at risk of earthquakes. To study the particular seismic response of coral sand, the numerical model of the coral sand-pile-superstructure system was established using FLAC3D. The hysteresis damping is used to describe the constitutive, shear modulus attenuation and hysteresis of coral sand under cyclic stress. The results show that although the increasing pile length magnifies the soil dynamic response, the superstructure settlement decreases with the increasing pile length. Increasing the coral sand relative density reduces the development of the excess pore pressure ratio of the soil, but it amplifies the pile bending moment.

Shallow‐marine carbonate cementation in Holocene segments of the calcifying green alga Halimeda

AbstractEarly‐diagenetic cementation of tropical carbonates results from the combination of numerous physico‐chemical and biological processes. In the marine phreatic environment it represents an essential mechanism for the development and stabilization of carbonate platforms. However, diagenetic cements that developed early in the marine phreatic environment are likely to become obliterated during later stages of meteoric or burial diagenesis. When lithified sediment samples are studied, this complicates the recognition of processes involved in early cementation, and their geological implications. In this contribution, a petrographic microfacies analysis of Holocene Halimeda segments collected on a coral island in the Spermonde Archipelago, Indonesia, is presented. Through electron microscopical analyses of polished samples, this study shows that segments are characterized by intragranular cementation of fibrous aragonite, equant High‐Mg calcite (3.9 to 7.2 Mol% Mg), bladed Low‐Mg calcite (0.4 to 1.0 Mol% Mg) and mini‐micritic Low‐Mg calcite (3.2 to 3.3 Mol% Mg). The co‐existence and consecutive development of fibrous aragonite and equant High‐Mg calcite results initially from the flow of oversaturated seawater along the aragonite template of the Halimeda skeleton, followed by an adjustment of cement mineralogy towards High‐Mg calcite as a result of reduced permeability and fluid flow rates in the pores. Growth of bladed Low‐Mg calcite cements on top of etched substrates of equant High‐Mg calcite is explained by shifts in pore water pH and alkalinity through microbial sulphate reduction. Microbial activity appears to be the main trigger for the precipitation of mini‐micritic Low‐Mg calcite as well, based on the presumable detection of an extracellular polymeric matrix during an early stage of mini‐micrite Low‐Mg calcite cement precipitation. Radiocarbon analyses of five Halimeda segments furthermore indicate that virtually complete intragranular cementation in the marine phreatic environment with thermodynamically/kinetically controlled aragonite and High‐Mg calcite takes place in about 100 years. Collectively, this study shows that early‐diagenetic cements are highly diverse and provides new quantitative constraints on the rate of diagenetic cementation in tropical carbonate factories.

Grunts (Actinopterygii: Perciformes: Haemulidae) of Bangladesh with two new distributional records from the northern Bay of Bengal assessed by morphometric characters and DNA barcoding

Grunts (family Haemulidae) are among the most commercially important fish in Bangladesh. This paper provides brief diagnostic characters of five previously reported grunt species: Plectorhinchus pictus (Thunberg, 1792); Pomadasys andamanensis McKay et Satapoomin, 1994; Pomadasys argenteus (Forsskål, 1775); Pomadasys argyreus (Valenciennes, 1833); Pomadasys maculatus (Bloch, 1793) and two new distributional records: Pomadasys guoraca (Cuvier, 1829) and Plectorhinchus macrospilus Satapoomin et Randall, 2000. The fishes were collected from the Saint Martin’s Island coral reef-like ecosystem and the adjacent sea of the Sundarbans mangrove forest of Bangladesh. The examined specimens were identified and diagnosed based on their morphometric characters and DNA barcoding COI gene. The new records of Pomadasys guoraca and Plectorhinchus macrospilus from Bangladesh greatly extend their distributional range in the Bay of Bengal. An updated checklist of grunts of Bangladesh is provided.

Hydrogeochemistry and Acidic Property of Submarine Groundwater Discharge Around Two Coral Islands in the Northern South China Sea

Submarine groundwater discharge (SGD) is an important source of nutrients in many coastal regions, yet little information is available on its carbonate chemistry and controlling factors. This study examined the processes and factors controlling the hydrogeochemistry and acidic property of the groundwaters and SGD waters of two isolated coral islands, Liuqiu Island (13 km off southwestern Taiwan) and Dongsha Island (located in the northern South China Sea, 420 km away from Liuqiu Island). Our results showed that the total alkalinity and dissolved inorganic carbon (DIC) of the fresh SGD waters were controlled mainly by the chemical weathering of carbonate minerals. Part of the DIC came from the organic matter decomposition or soil CO2, reducing the pH and CO32− concentration. Distributions of the carbonate chemistry and nutrients of the SGD waters were controlled mainly by physical mixing between the groundwater and the ambient seawater under the seabed, the so-called subterranean estuary. The Ca2+ released through weathering significantly increased the saturation state of aragonite or calcite, reducing the corrosiveness of the SGD waters on the carbonate rocks. This study is likely the first to examine the effects of the acidic property of SGD waters on the biogenic carbonate spine of a sea urchin and a pteropod shell. The spring water with similar carbonate chemistry to that of the freshwater SGD endmember from Liuqiu Island with a saturation state of aragonite of 0.96 caused observable dissolution on the spine of a sea urchin and a pteropod shell, but the spine dissolved more readily. This was because the spine is made of high-Mg calcite, which has higher solubility than that of aragonite or calcite. Such a result implies that some marine organisms with carbonate skeletons or shells containing high Mg:Ca ratios may suffer the impact of ocean acidification earlier. Although the SGD may contribute less than 10% of freshwater discharge by rivers to the coastal area, its impact on coastal biogeochemical cycles and ecosystems due to its acidic property and continual effect on the coast all year round deserves further investigation.

Characterization and source analysis of heavy metals contamination in microplastics by Laser-Induced Breakdown Spectroscopy

The increasing presence of microplastics in marine environment is a critical issue and the plastic-metal contamination has received much attention. However, conventional methods for heavy metal determination are time-consuming, need sample pretreatments, require a strict operation environment, or have high limits of detection. In this study, heavy metals contaminated microplastics samples collected from a remote coral island were quantified and analyzed by using Laser-Induced Breakdown Spectroscopy (LIBS). The characters of the trace metals in microplastics were used to determine the sources of the contaminants, and the potential origins of the metals were demonstrated from the statistical analysis. LIBS is a facile and non-destructive trace analysis technique and the strategy led to rapid and multi-metals detection of individual samples. Heavy metals such as copper (Cu), lead (Pb), iron (Fe), cadmium (Cd), zinc (Zn), manganese (Mn), chromium (Cr) were detected and quantified in the individual microplastics samples. The findings showed that LIBS is a promising strategy for the characterization of microplastics and for the analysis of the source of heavy metals contaminants present in the microplastics particles.

Climate change and the increasing vulnerability of the poor in the Commonwealth

ABSTRACT Many millions of the most-deprived people of the Commonwealth live in highly vulnerable locations: the tropical countries affected by cyclones (hurricanes or typhoons). Tropical cyclone intensities have been increasing since the mid-1990s. Their tracks may be shifting poleward. The associated storm surges are growing in height and severity. From the Caribbean to eastern Africa, the islands of the Indian Ocean, South Asia, Australia and the Pacific communities face, increasing flooding, housing and workplace damage and loss of livelihoods. Among the most vulnerable are those living in low-lying coastal communities on coral islands, the deltas of great rivers, and coastal sand barriers. These communities are often dependent on small-scale fisheries and are at great risk. This vulnerability has been aggravated by the COVID-19 pandemic which has struck urban areas already suffering from outbreaks of infectious diseases such as dengue, cholera, and diarrhoea. When storm damage affects the public health infrastructure the ability to cope with these multiple hazards is likely to be overstretched. Investment in disaster preparation and relief for these worsening vulnerability situations. Action has to be taken at all levels, from the household and local community to municipal, regional and national governments. This article argues that international support is critical and governments should be increasing international aid.

Selection on genes associated with the evolution of divergent life histories: Gamete recognition or something else?

Gamete compatibility, and fertilization success, is mediated by gamete-recognition genes (GRGs) that are expected to show genetic evidence of a response to sexual selection associated with mating system traits. Changes in the strength of sexual selection can arise from the resolution of sperm competition among males, sexual conflicts of interest between males and females, or other mechanisms of sexual selection. To assess these expectations, we compared patterns of episodic diversifying selection among genes expressed in the gonads of Cryptasterina pentagona and C. hystera, which recently speciated and have evolved different mating systems (gonochoric or hermaphroditic), modes of fertilization (outcrossing or selfing), and dispersal (planktonic larvae or internal brooding). Cryptasterina spp. inhabit the upper intertidal of the coast of Queensland and coral islands of the Great Barrier Reef. We found some evidence for positive selection on a GRG in the outcrossing C. pentagona, and we found evidence of loss of gene function in a GRG of the self-fertilizing C. hystera. The modification or loss of gene functionality may be evidence of relaxed selection on some aspects of gamete interaction in C. hystera. In addition to these genes involved in gamete interactions, we also found genes under selection linked to abiotic stress, chromosomal regulation, polyspermy, and egg-laying. We interpret those results as possible evidence that Cryptasterina spp. with different mating systems may have been adapting in divergent ways to oxidative stress or other factors associated with reproduction in the physiologically challenging environment of the high intertidal. RESEARCH HIGHLIGHTS: Recent speciation between two sea stars was unlikely the result of selection on gamete-recognition genes annotated in this study. Instead, our results point to selection on genes linked to the intertidal environment and reproduction.

Global decline in capacity of coral reefs to provide ecosystem services

Global decline in capacity of coral reefs to provide ecosystem services

Development of the first microsatellite markers using high-throughput sequencing for a hexaploid coastal species, Tournefortia argentea L. f. (Boraginaceae).

Tournefortia argentea L. f. is a hexaploid shrub or tree species with ecological and evolutionary significances, which forms the fringe of vegetation closest to the sea on tropical coral islands. Previous studies have never addressed on genetic information, and thus genomic resources remain scarce. We used nine individuals from different islands to identify polymorphic microsatellites of T. argentea by Illumina high-throughput sequencing. Thirty-five polymorphic microsatellite markers were developed. Characteristics of each locus were tested using 48 individuals collected from three populations of T. argentea. A total of 320 alleles were found across the 35 microsatellite loci. The number of alleles per locus ranged from 5 to 15, with an average of 9.1. Observed and expected heterozygosities in each locus per population varied from 0.000 to 1.000 and from 0.000 to 0.893, respectively. In this study, we report the development of 35 polymorphic microsatellite markers based on Illumina high-throughput sequencing. These markers will facilitate the investigations of genetic diversity, population structures and evolutionary history of T. argentea.

Comment on Gazi et al. (2020): Detecting Coral Reef Degradation on St. Martin’s Island, Bangladesh?

St. Martin’s Island is a small sedimentary island situated at the southernmost part of Bangladesh (20°37.6′ N and 92°19.3′ E). The island is surrounded by rocky reefs composed of Neogene bedrock consisting of moderately hard and soft sandstones and conglomerates belonging to the Tipam Sandstone (Islam in Bangladesh J Univ Sheffield Geol Soc 7:269–275, 1980). The rocky reefs are covered by fields of conglomerate boulders and calcareous concretions that provide a suitable substrate for coral settlement and the establishment of coral communities. Before 1997 it was reported that St. Martin’s Island was a coral island surrounded by coral reefs (Ahmed in Bangladesh J Environ Sci 1:67–73, 1995; Anwar in National workshop on coastal area resource development and management, Part II. CARDMA, BRAC Printers Bangladesh, Dhaka, pp 36–66, 1988; UNEP/IUCN in Indian Ocean, Red Sea and Gulf. UNEP regional seas and bibliographies. IUCN, Gland, 1988). However, the first underwater survey conducted in 1997 did not find any evidence of coral reefs (Tomascik in Management plan for coral resources of Narikel Jinjira (St. Martin's Island). National Conservation Strategy Implementation Project-1, Ministry of Environment and Forest, Government of the People’s Republic of Bangladesh, p 125, 1997). The island has become an important tourism destination and concerns have been raised about the impact of local development on its coral resources (Tomascik 1997). Recently a paper was published on the degradation of coral reefs on St. Martin’s Island (Gazi et al. in Ocean Sci J 55(3):419–431, 2020) that makes many factually incorrect assertions. The rocky reefs that surround the island have been misclassified by Gazi et al. (2020) as “coral reefs”. Here, we discuss Gazi et al. (2020) and examine if the results and conclusions provide factual evidence of spatiotemporal coral reef degradation.

Assessment of habitat change on bird diversity and bird\u2013habitat network of a Coral Island, South China Sea

BackgroundUnderstanding how island ecosystems change across habitats is a major challenge in ecological conservation under the conditions of habitat degradation. According to a 2-year investigation on Dong Island of the Paracel Islands, South China Sea, we assessed the roles of different habitats at the species level and community level of birds using topological and network analysis.ResultsIn addition to the thousands of Sula sula (a large-sized arboreal seabird) inhabiting the forests, there were 56 other bird species were recorded, representing 23 families and 12 orders, ranging in habitats of wetlands, forests, shrublands, grasslands, and/or beaches. The bird–habitat network had high nestedness, and bird species showed obvious clustering distribution. Integrated topological and network analysis showed that wetlands had a high contribution to species diversity and network structure, and it was a cluster center of migrant birds. Forests and grasslands were species hub and connector respectively, and forests were also the key habitat for residents. Beaches and shrublands were peripherals. The loss of wetlands and forests will result in a sharp reduction of species richness, and even make the S. sula, and most of the resident birds, become locally extinct.ConclusionsThese results suggest that the wetland and forest habitats on the focal island are key important for migrant birds and resident birds respectively, and therefore much more attention should be paid to conservation of the focal island ecosystems.

Estimated carbon stock of various mangrove zonation in Marsegu Island, West Seram, Maluku

This study aimed to determine the amount of carbon storage of various mangrove zonation formed on Marsegu Island, West Seram, Maluku. Marsegu Island is a Raised Coral Island which has 46.75% mangrove vegetation (112.29 ha) with the area of each zonation is 32.12 ha (proximal zone), 39.00 ha (middle zone) and 41.17 ha (distal zone). The calculation of stored carbon stocks of various mangrove zonation in Marsegu island used SNI guidelines (Indonesian National Standard) 7724:2011. Field measurements for estimation of forest carbon stocks (ground-based forest carbon accounting). The estimations of above-ground carbon stored in the proximal zone, middle zone and distal zone are as follows: 52.11 t/ha, 70.50 t/ha and 140.13 t/ha. Meanwhile, the below-ground (root) carbon storage is 10.62 t/ha, 13.48 t/ha and 24.36 t/ha. The potential amount of carbon of above and below ground plus dead trees and dead-wood (necromass), with estimation soil carbon storage up to 20 cm depth, are 234.07 t/ha for the proximal zone, 317.47 t/ha for middle zone and 406.58 t/ha for the distal zone. The estimated total carbon stock in Mangrove Forest of Marsegu Island is 36,637.02 tonnes.

Performance of five typical warm‐season turfgrasses and their influence on soil bacterial community under a simulated tropical coral island environment

AbstractVegetation is a key to improving and protecting a new tropical coral island terrestrial ecosystem. Because of their superior ability in adapting poor soil structure and fertility, conserving soil and water and improving the living environment, warm‐season turfgrass are considered as important pioneer plants and frequently applied in vegetation construction on tropical coral islands. However, few studies had evaluated the growth of these turfgrass and how these turfgrass influence the soil microbial communities on tropical coral islands. In this study, we conducted a greenhouse experiment and assessed the performance, soil properties and rhizosphere bacterial communities of five typical warm‐season turfgrasses species (i.e., Paspalum vaginatium, Paspalum notatum, Cynodon dactylon, Zoysia tenuifolia, and Stenotaphrum helferi) grown on tropical coral sand. Results showed that C. dactylon was superior in the adaptability and turf performance among the studied species, with a turf establishment time of 34 days and a turf quality score of 6.83. Richness of bacterial species and nitrifying bacteria in its rhizosphere soil planted with C. dactylon were also much higher than with other species. The speed of turf establishment was positively correlated with rhizosphere soil bacterial species richness. Our findings indicated that C. dactylon could be a potentially suitable candidate species for vegetation restoration and soil bacterial community conservation on tropical coral islands.