Small Tropical Islands Research Articles

Geochemical processes, evidence and thermodynamic behavior of dissolved and precipitated carbonate minerals in a modern seawater/freshwater mixing zone of a small tropical island

The geochemical processes and thermodynamic behavior of dissolved and precipitated carbonate minerals controlling the hydrochemistry of an aquifer in the seawater/freshwater mixing zone of a small island are identified. Field and laboratory analyses, geochemical modeling (PHREEQC) and multivariate statistical analysis (MSA) provide a quantitative interpretation for the geochemistry of the carbonate-dominated aquifer. Geochemical analyses and modeling results show that dissolution and re-precipitation of CaCO3 are the prevalent processes governing geochemical reactions in the mixing zone. Furthermore, this was confirmed by coherent statistical output that incorporates Principle Component Analysis (PCA) and k-means Cluster Analysis (k-CA). Generally, the composition of the lowland sandy soil was rather homogeneous and was primarily composed of quartz, aragonite, calcite and Mg-calcite. Thermodynamic model calculations indicate that the carbonate minerals calcite, aragonite and dolomite are supersaturated in the mixing zone. Nevertheless, Powder X-ray Diffraction (PXRD) and Scanning Electron Microscope (SEM) examination verified the occurrence of low-Mg-calcite (LMC) and the absence of dolomite, attributed to thermodynamic/kinetic hindrance, cation disorder and the presence of dolomite crystal growth rate inhibitors (such as SO4). The results suggest that dissolution of aragonite and precipitation of LMC drives the solid phase geochemistry in the small tropical island aquifer.

Impact of native forest restoration on endemic crickets and katydids density in Rodrigues island

Native species of oceanic islands are often unique and of conservation concern. Native habitat restoration schemes are now conducted on many oceanic islands, and are often characterized by both the small sizes of the restored areas, and the high degradation level prior to restoration. Whereas arthropods are often neglected in restoration schemes, on small tropical islands they may represent the largest proportion of extant native terrestrial animals surviving habitat degradation. The island of Rodrigues, in the South Western Indian Ocean, is typical of such cases. The only patches of forest and bushes remaining on Rodrigues in 1996 were dominated by non-native invasive species. Since 1996, restoration schemes were conducted in Grande Montagne Nature Reserve. Benefits of these 15 years of native forest restoration were assessed on endemic Orthoptera density and diversity using acoustic monitoring and insect density measurements. Unrestored exotic plant-dominated areas were a low-density reservoir for endemic Orthoptera, many of which were new to science. Habitat restoration increased by four to seven times the density of these endemic Orthoptera, depending on the restoration scheme. The presence of managed areas did not significantly increase the density of endemic Orthoptera on the neighboring unrestored exotic plant-dominated areas.

Tracing sewage water by 15N in a mangrove ecosystem to test its bioremediation ability

Mangrove forests could be a simple and effective alternative to conventional sewage treatment, particularly for island communities given its low cost and low maintenance. Due to their high adaptation capacity, these plants are able to tolerate and bioremediate the high levels of nutrients and pollutants found in sewage water. This solution could be applied to small tropical islands with high population density such as Mayotte in the Indian Ocean. This paper reports on a trial by stable isotopic (15)N tracing of such a bioremediation process on pre-treated wastewater near the village of Malamani, in the middle of the large coastal mangrove in the bay near Chirongui. The first results show a boost in the mangrove growth, but a longer period of observation is needed to confirm the beneficial effects, and also to clarify the role of the local crab population, whose engineering activities play an important part in the ecosystem. The exact denitrification process is not yet understood, and the mass balance equation also reveals loss of nitrogen-containing compounds, which needs to be analyzed more closely.

Impact of a Medical Waste Incinerator on Mercury Levels in Lagoon Fish from a Small Tropical Island in the Western Pacific

In 2004–2005, several species of marine fish were collected for mercury (Hg) analysis from Saipan Lagoon, Saipan, Commonwealth of the Northern Mariana Islands. Relatively high concentrations were found in representatives from the Hafa Adai Beach area located some distance from known sources of Hg contamination. A follow-up investigation aimed at identifying additional land-based sources of Hg in the area was launched in early 2007. The study identified a medical waste incinerator as the primary source of Hg enrichment. The incinerator was operational for about 20 years before it was closed down by the U.S. Environmental Protection Agency (EPA) in January 2006, for multiple violations of the Clean Air Act. Stormwater runoff from this facility entered a drainage network that discharged into the ocean at the southern end of Hafa Adai Beach, about 1 km away. At the time of this investigation storm drain sediments at the coast were only marginally enriched with mercury although values some 50x above background were detected in drainage deposits a few meters down-gradient of the incinerator site. Mercury concentrations in fish from the Hafa Adai Beach area were also significantly lower than those determined in similar species 3 yr earlier. The implications of the data are briefly discussed.

Understanding of groundwater salinity using statistical modeling in a small tropical island, East Malaysia

This paper presents an understanding of groundwater salinity by identification of effective factors using chemometric methods (cluster analysis and multiple linear regressions) in Manukan Island, Sabah. Local groundwater and environmental properties were used to explore the effective factors of groundwater salinity. Cluster analysis showed salinity and chloride illustrated the highest similarities. Electrical conductivity and total dissolved solids were also grouped in the same cluster. Seawater is the only chloride source in groundwater of Manukan Island demonstrated an indication of seawater mixing in freshwater. It is an effect of upward movement of the seawater by pumping activities. Precipitation and evapotranspiration (environmental condition) with hydraulic heads were clustered together to show that they also influence salinity concentration in groundwater. Multiple linear regressions showed descending order of the factors from chloride (the largest contribution) to evapotranspiration (the smallest contribution) and illustrated the contribution to groundwater salinity in Manukan Island. The integrated results using chemometric methods have provided a way to identify the effective factors on groundwater salinity. This similar approach and resulting equation can be applied in other small tropical islands with alike hydrogeological condition and limited information available for a better understanding of its groundwater salinity.

Rain on small tropical islands

[1] A high-resolution rainfall climatology based on observations from the Tropical Rainfall Measuring Mission's Precipitation Radar (PR) instrument is used to evaluate the influence of small tropical islands on climatological rainfall. Islands with areas between one hundred and several thousand km2 are considered in both the Indo-Pacific Maritime Continent and Caribbean regions. Annual mean climatological (1997–2007) rainfall over each island is compared with that over the surrounding ocean region, and the difference is expressed as a percentage. In addition to total rainfall, rain frequency and intensity are also analyzed. Results are stratified into two 12 h halves of the diurnal cycle as well as eight 3 h periods, and also by a measure of each island's topographic relief. In both regions, there is a clear difference between larger islands (areas of a few hundred km2 or greater) and smaller ones. Both rain frequency and total rainfall are significantly enhanced over larger islands compared to the surrounding ocean. For smaller islands the enhancement is either negligibly small, statistically insignificant, or, in the case of Caribbean rain frequency, negative. The enhancement in total rainfall over larger islands is partly attributable to greater frequency and partly to greater intensity. A diurnal cycle in island enhancement is evident in frequency but not intensity, except over small Caribbean islands where the converse is true. For the larger islands, higher orography is associated with greater rainfall enhancements. The orographic effect is larger (percentagewise) in the Caribbean than in the Maritime Continent. Orographic precipitation enhancement manifests more strongly as increased frequency of precipitation rather than increased intensity and is present at night as well as during the day. The lack of a clear diurnal cycle in orographic enhancement suggests that much of the orographic rainfall enhancement is attributable to mechanically forced upslope flow rather than elevated surface heating.

Statistical approaches and hydrochemical modelling of groundwater system in a small tropical island

The aquifer of Manukan Island of Borneo, Malaysia had been found to be affected by seawater intrusion associated with excessive groundwater exploitation. This research attempted to characterize the chemistry of an impacted zone in the island using factor analysis (FA), cluster analysis (CA) and a hydrochemical model package (PHREEQC). The factor scores were used to plot the spatial map and to group the relationships among the monitoring wells using CA. The results of FA analysis revealed that the three main processes associated with the seawater intrusion event are aquifer salinization, cation exchange process and redox sequences. Output from the PHREEQC simulation was used to support the findings from the multivariate analysis.

Comparison of dissolved inorganic and organic carbon yields and fluxes in the watersheds of tropical volcanic islands, examples from Guadeloupe (French West Indies)

Organic matter is an important factor that cannot be neglected when considering global carbon cycle. New data including organic matter geochemistry at the small watershed scale are needed to elaborate more constrained carbon cycle and climatic models. The objectives are to estimate the DOC and DIC yields exported from small tropical watersheds and to give strong constraints on the carbon hydrodynamic of these systems. To answer these questions, we have studied the geochemistry of eleven small watersheds around Basse-Terre volcanic Island in the French West Indies during different hydrological regimes from 2006 to 2008 (i.e. low water level versus floods). We propose a complete set of carbon measurements, including DOC and DIC concentrations, δ 13C data, and less commonly, some spectroscopic indicators of the nature of organic matter. The DOC/DIC ratio varies between 0.07 and 0.30 in low water level and between 0.25 and 1.97 during floods, indicating that organic matter is mainly exported during flood events. On the light of the isotopic composition of DOC, ranging from − 32.8 to − 26.2‰ during low water level and from − 30.1 to − 27.2‰ during floods, we demonstrate that export of organic carbon is mainly controlled by perennial saprolite groundwaters, except for flood events during which rivers are also strongly influenced by soil erosion. The mean annual yields ranged from 2.5 to 5.7 t km − 2 year − 1 for the DOC and from 4.8 to 19.6 t km − 2 year − 1 for the DIC and exhibit a non-linear relationship with slopes of watersheds. The flash floods explain around 60% of the annual DOC flux and between 25 and 45% of the DIC flux, highlighting the important role of these extreme meteorological events on global carbon export in small tropical volcanic islands. From a carbon mass balance point of view the exports of dissolved carbon from small volcanic islands are important and should be included in global organic carbon budgets.

How island size and isolation affect bee and wasp ensembles on small tropical islands: a case study from Kepulauan Seribu, Indonesia

Aim To study the effects of isolation and size of small tropical islands on species assemblages of bees (superfamily Apoidea) and wasps (superfamily Vespoidea). Location Twenty islands in the Kepulauan Seribu Archipelago off the coast of west Java, Indonesia. The size of surveyed islands ranges between 0.75 and 41.32 ha; their distance from the coast of Java varies between 3 and 62 km. Methods Field work was conducted from February to May 2005. Bees and wasps were caught with a sweep net during sampling units of 15 min, continuing until four consecutive samples revealed no new species. Total species richness was quantified by the estimators Chao 2, first-order jackknife and Michaelis–Menten. The software binmatnest was used to test for nestedness of species assemblages. Similarities of species composition between islands were quantified by Sørensen’s similarity index. Results Eighty-two species were recorded on the 20 surveyed islands. Species richness declined with increasing isolation of islands from the source area, Java. Although the size of the largest island exceeded that of the smallest island by a factor of almost 60, island size only very weakly affected species richness of bees; no effect of island size was found for wasps. Mean body size of species decreased with increasing island isolation. Nestedness of island faunas was only weakly developed. Species composition of both superfamilies was affected by island isolation, but not by island size. Main conclusions While the species–isolation relationship on the very small islands of Kepulauan Seribu followed the prediction of MacArthur and Wilson’s equilibrium theory, the absence of a species–area relationship indicated a weak ‘small-island effect’, at least in wasps. The combination of an only weakly developed pattern of nested species subsets, the shift in species compositions and the decline of mean body size with increasing island isolation from the source area indicates that biotic interactions and different species traits contribute to the shaping of communities of bees and wasps within the archipelago. The potential of biotic interactions for generating distribution patterns of species within the archipelago is also emphasized by the observed restriction of some species with apparently high dispersal abilities to outer islands.

Saturation states of carbonate minerals in a freshwater-seawater mixing zone of small tropical island’s aquifer

Groundwater is a crucial resource on the Manukan Island as it is the only source of freshwater available on the island. The aquifer has deteriorated to a high degree, during the last decade. Nine domestic wells were sampled from March 2006 to January 2007 to probe the hydrochemical components that influence the water quality. Geochemical data on dissolved major constituents in groundwater samples from the Manukan Island revealed the main processes responsible for their geochemical evolution. The results using statistical analyses, graphical method and numerical model output (PHREEQC) showed that the groundwater was chemically highly enriched in Na and Cl, indicative of seawater intrusion into the aquifer as also supported from the Na-Cl signature on the Piper diagram. From the PHREEQC simulation model, calcite, dolomite and aragonite solubility showed positive values of the saturation indices (SI), indicating supersaturation which led to mineral precipitation condition of water by these minerals.

Ant communities on small tropical islands: effects of island size and isolation are obscured by habitat disturbance and ‘tramp’ ant species

AbstractAim Comparisons among islands offer an opportunity to study the effects of biotic and abiotic factors on small, replicated biological communities. Smaller population sizes on islands accelerate some ecological processes, which may decrease the time needed for perturbations to affect community composition. We surveyed ants on 18 small tropical islands to determine the effects of island size, isolation from the mainland, and habitat disturbance on ant community composition.Location Thousand Islands Archipelago (Indonesian name: Kepulauan Seribu) off Jakarta, West Java, Indonesia.Methods Ants were sampled from the soil surface, leaf litter and vegetation in all habitat types on each island. Island size, isolation from the mainland, and land‐use patterns were quantified using GIS software. The presence of settlements and of boat docks were used as indicators of anthropogenic disturbance. The richness of ant communities and non‐tramp ant species on each island were analysed in relation to the islands’ physical characteristics and indicators of human disturbance.Results Forty‐eight ant species from 5 subfamilies and 28 genera were recorded from the archipelago, and approximately 20% of the ant species were well‐known human‐commensal ‘tramp’ species. Islands with boat docks or human settlements had significantly more tramp species than did islands lacking these indicators of anthropogenic disturbance, and the diversity of non‐tramp species decreased with habitat disturbance.Main conclusions Human disturbance on islands in the Thousand Islands Archipelago promotes the introduction and/or establishment of tramp species. Tramp species affect the composition of insular ant communities, and expected biogeographical patterns of ant richness are masked. The island with the greatest estimated species richness and the greatest number of unique ant species, Rambut Island, is a forested bird sanctuary, highlighting the importance of protected areas in preserving the diversity of species‐rich invertebrate faunas.

Kleptothermy: an additional category of thermoregulation, and a possible example in sea kraits ( Laticauda laticaudata , Serpentes)

Lacking the capacity for thermogenesis, most ectotherms inhabiting thermally heterogeneous environments rely instead upon exploiting that ambient heterogeneity. In many cases they maintain body temperatures within a narrow range despite massive spatial and temporal variation in ambient conditions. Reliance on diverse thermal opportunities is reflected in specific terms for organisms that bask in sunlight to regulate their temperature (heliotherms), or that press their bodies against warm substrates to facilitate heat flow (thigmotherms), or that rely on large body mass to maintain thermal constancy (gigantothermy). We propose an additional category of thermoregulators: kleptotherms, which regulate their own temperature by 'stealing' heat from other organisms. This concept involves two major conditions: the thermal heterogeneity created by the presence of a warm organism in a cool environment and the selective use of that heterogeneity by another animal to maintain body temperatures at higher (and more stable) levels than would be possible elsewhere in the local area. Kleptothermy occurs in endotherms also, but is usually reciprocal (rather than unilateral as in ectotherms). Thermal monitoring on a small tropical island documents a possible example of kleptothermy, based on high stable temperatures of a sea snake (Laticauda laticaudata) inside a burrow occupied by seabirds.

Visitation Patterns and Perceptions of National Park Users – Case Study of Dominica, West Indies

Cette étude, conduite dans deux parcs nationaux de l'île de Dominique, est divisée en deux phases. Notre objectif principal est d'explorer le rapport entre les caractéristiques des participants (par exemple genre, âge et nationalité) et leur perception concernant les conditions des ressources naturelles dans les parcs. Notre deuxième objectif est de contribuer à la base de données sur le tourisme vert et les ressources naturelles dans le contexte de cette petite île tropicale. Par le biais de questionnaires, nous avons examiné le patron d'utilisation de l'espace par les usagers; de même, pour avoir des données plus amples, nous avons recueilli des informations sur les ressources écologiques présentes sur des sentiers d'un mètre de large. Aussi, avons-nous constaté un rapport homogène entre les perceptions des usagers des parcs sur les conditions des ressources naturelles. Toutefois, ces perceptions divergeaint en ce qui concernait certains aspects: le test du khi carré ( Chi-square test ), par exemple, a révélé qu'il existe un rapport significatif entre l'evaluation faite par les usagers et leur genre. En outre, nous avons identifié des liens significatifs entre les perceptions des usagers par rapport à l'état des ressources, et leur âge et nationalité, mais uniquement après avoir regroupé toutes les données. D'après les resultats de notre étude, nous avons conclu que les responsables des ressources naturelles devraient privilégier un ensemble d'approches —au lieu d'une approche unique— pour évaluer et surveiller les changements écologiques de ces ressources et pour prendre des décisions informées.

Surface fair-weather potential gradient measurements from a small tropical island station Suva, Fiji

Abstract Systematic analysis of the surface fair-weather potential gradient (PG) measured for 13 months (July 2005–July 2006) at 10 s resolution over a small tropical island station Suva (18.08°S, 178.45°E), Fiji is presented. Based on the solar radiation (>800 W m−2) and surface wind speed (<4.5 m s−1) conditions, 63 fair-weather days were selected. After sorting the data into a range of 0–1000 V m−1, the average PG was ∼139 V m−1. The measured fair-weather PG had a semi-diurnal structure, with a more pronounced peak at 0730 LT (1930 UT) and a reduced peak at 2200 LT (1000 UT). The time of occurrence of the morning peak and the noontime minima agreed well with the Carnegie curve. However, the variation about the global mean in the measured PG was 150% whereas for the Carnegie curve it was only 35%. The effects of the local meteorological parameters on the PG measurements were found to be small. On average, the PG during the dry season (May–October) was always greater than in the wet season (November–April). In contrast, analysis of regional (0–60°S and 100°E–160°W) lightning activity on fair-weather days showed a peak at ∼2000 LT and higher lightning activity during the wet season. These results indicate that the regional thunderstorm activity has no direct connection with the local fair-weather PG at the site.

Tourism planning in small tropical islands: methodological considerations and development issues in Samoa

This chapter seeks to contribute to a greater understanding of tourism on small tropical islands and to tourism planning in this context by outlining aspects of the methodology used in the preparation of the Samoa Tourism Development Plan 2002-2006 and by discussing some of the issues that arose from this process. In particular, the chapter presents a ‘question-asking’ approach that involves wide-ranging stakeholder consultation to identify and then address key issues, namely: - How much tourism does Samoa want and at what rate should it be developed over the next five years? - What will the growth of tourism in Samoa over the period 2002-2006 depend on? - What forms of tourism should be developed and where? - What are the most appropriate processes of tourism development for Samoa? The strategies formulated in the plan are then outlined. The paper concludes that local participation, while invaluable, is by itself insufficient for the preparation of an effective tourism development plan.

Preliminary findings of surface fair-weather electric field trends over small tropical island station, Suva, Fiji

The South Pacific Journal of Natural Science (SPJNS) is published online by CSIRO PUBLISHING on behalf of the Faculty of Science and Technology, The University of the South Pacific, Fiji. The normal focus of the journal is to disseminate scientific research work carried out in the Pacific.

Total rain accumulation and rain‐rate analysis for small tropical Pacific islands: a case study of Suva, Fiji

AbstractRain‐rate analyses using hourly data from 1990 to 2002 predict rain occurrence for ∼15% of the year while minute data for the period Apr '02–Mar '03 resolve rain‐rate more accurately and show rain occurrence of ∼2% of the year. It is estimated that <1% of the rain at the site is mainly convective. Rainfall analysis confirms its dependence on El Niño Southern Oscillation and convergence zones. Copyright © 2006 Royal Meteorological Society

Urban heat islands developing in coastal tropical cities

Beautiful and breezy cities on small tropical islands, it turns out, may not be exempt from the same local climate change effects and urban heat island effects seen in large continental cities such as Los Angeles or Mexico City. A surprising, recent discovery indicates that this is the case for San Juan, Puerto Rico, a relatively affluent coastal tropical city of about two million inhabitants that is spreading rapidly into the once‐rural areas around it.A recent climatological analysis of the surface temperature of the city has revealed that the local temperature has been increasing over the neighboring vegetated areas at a rate of 0.06°C per year for the past 30 years. This is a trend that may be comparable to climate changes induced by global warming.

Introduction: That most remarkable of outside men - Harold Brookfield's intellectual legacy

: Harold Brookfield's academic career spans more than half a century, traversing small tropical and subtropical islands and mountainous uplands, focusing on people–environment relations and linking to a diversity of institutions and disciplines. His unwavering commitment to fieldwork at the local level and to comparative study is paralleled by a healthy scepticism with respect to academic trends and orthodoxy of any kind, whether intellectual or physical. It is the farmers of the developing world who are the source of much of his inspiration. His theoretical contributions are based essentially on his observations of their practices and his learning from their experiences. His academic insights into the processes of change in rural areas of Melanesia, East and South-East Asia, Africa and South America, where small-scale ecological studies are linked to global forces, are of lasting significance.

Dispersal and germination of seeds of Pisonia grandis, an Indo-Pacific tropical tree associated with insular seabird colonies

The distribution of the forest tree Pisonia grandis (Nyctaginaceae) coincides with seabird colonies on small tropical islands. Its seeds are enclosed in a calyx exuding extremely sticky resin which adheres strongly to feathers. Birds are obviously seed-dispersal vectors, but the multi-seeded infructescences frequently entangle birds, often fatally. On Cousin Island, Seychelles, I investigated the production, germination, survival, and tolerance to seawater of Pisonia seeds, and the occurrence of entanglement with birds. Fresh seeds had high germination success (62–87% in experimental trays), but seedling survival in Cousin's forests was low (0.1% of 6020 seeds survived as seedlings after 2–8 mo). Some seeds tolerated 30 min daily immersions in seawater (8–15% germination after 14–28 d treatment), but not continuous immersion in seawater (reduced germination after 5 d and none after 12 d). Inter-island dispersal is likely via living unencumbered seabirds carrying a few seeds, but not on floating carcasses. Seeds attached to carcasses did not have improved germination or survival. Intra-island propagation is almost entirely vegetative, with negligible local seed dispersal. Pisonia plants therefore do not benefit from fatal entanglements. The extreme stickiness of the seeds evidently evolved to resist removal by seabirds and so facilitate long-distance dispersal. The mortality of some potential vectors is an unfortunate consequence, but has little impact on the large populations of tree- and ground-nesting seabirds which nest in or under these trees.