Coast Of Madagascar Research Articles

The Antalaotra People of Madagascar: Made and Unmade by the Sea

The territory of Madagascar emerged from the unification of formerly independent kingdoms. These kingdoms were geographically distinct, with one main inland kingdom and several coastal ones. The “Kingdom of Madagascar” emerged in the nineteenth century from political conquests made possible by the trade effervescence taking place along the nearby Mozambique Channel, creating an islandbased unity. The Antalaotra people, or “People from the Sea,” who lived in the Comoros archipelago and the northwest coast of Madagascar, acted as a bridge between the different territories. Over a period of five centuries, they laid a common cultural foundation for a Malagasy society. Their regional trading culture allowed them to penetrate the inland kingdom through economic and cultural exchange. However, their contribution to an emerging national heritage was quickly suppressed and by the nineteenth century the Antalaotra had disappeared in Madagascar as a community. Today, Madagascar’s national identity continues to emphasize the former inland Merina Kingdom, land of the Merina people, making national disparities significant in every aspect, especially culturally. Successive national governments have ignored the role of coastal heritage in the forging of national identity. This article dives into the past and inheritance of the Antalaotra people to argue for the inclusion and acknowledgment of their coastal heritage as part of the national identity.

Teniky: enigmatic architecture at an archaeological site in southern Madagascar

ABSTRACT Teniky is an isolated inland archaeological site in the Isalo massif of southern Madagascar, with enigmatic rock-cut architecture that is unique in all of Madagascar and the wider East African coast. In the first half of the twentieth century visitors described archaeogical structures within a fluvial cirque (i.e. an amphitheatre-shaped valley formed by fluvial erosion), which included man-made terraces, rock-cut niches in the steep cliffs and a rock shelter delimited by walls consisting of carved sandstone blocks. Our investigations at Teniky have led to the discovery of further archaeological structures beyond the cirque. These structures include further terraces, rock-cut niches, stone basins and carved sandstone walls on a hill 2.5 km to the west, as well as sandstone quarries and dry stone walls in the valley in between. AMS radiocarbon dating of charcoal found during excavations at the newly discovered rock-cut niches and carved sandstone walls indicates that they were constructed in the late first millennium/early second millennium c. tenth to twelfth century AD. Pottery sherds at Teniky include Chinese and Southeast Asian ceramics dating to broadly the eleventh to fourteenth centuries, concordant with the radiocarbon ages. The presence of imported ceramics indicates that those living at Teniky participated in Indian Ocean trade networks in medieval times, despite being over 200 km from the nearest coast. The closest stylistic parallels to the enigmatic rock-cut architecture at Teniky are found in present-day Iran, particularly in the Fars region, where rock-cut niches dating to the first millennium AD or earlier have been attributed to Zoroastrian communities. We tentatively interpret the rock-cut architecture at Teniky as part of a former necropolis made by settlers with Zoroastrian origins. More archaeological research is required to test this hypothesis and to address questions such as: where and when did these settlers first arrive on the coast of Madagascar; why and when did they move inland; how did they live and how did they interact with other populations on the island; and why and when was the site deserted?

A New Insight into the Genesis of Graphite Deposits in Madagascar Using U–Pb Zircon Dating and Electron Microprobe Analysis

Madagascar is globally recognized as an important producer of high-quality flaky graphite. However, current research on graphite deposits in Madagascar remains insufficient. Previous studies have linked the genesis of Madagascan graphite deposits to the metamorphism of sedimentary organic matter. Here, we provide a case study of graphite deposits in Madagascar, combining new data from the Ambahita graphite deposit (AMG) in southern Madagascar with data from the Antanisoa graphite deposit (ANG) in central Madagascar and the Vohitasara graphite deposit (VOG) on the east coast of Madagascar. We note that the mineral assemblages of graphite-bearing rocks in the AMG, ANG, and VOG are not typical of metamorphic mineral assemblages but rather the results of filling and metasomatism by mantle-derived fluids that occurred after peak metamorphism. Electron microprobe analysis indicates that the graphite of the AMG, VOG, and ANG is usually associated with phlogopite or Mg-biotite; the phlogopite shares a common genesis with other widespread phlogopite deposits across Madagascar. We reveal that the distribution of graphite deposits in Madagascar is primarily controlled by ductile shear zones between blocks. Ductile shear zones that extend deep into the mantle can provide an ideal migration channel and architecture for the emplacement of mantle-derived fluids. The graphite mineralization formed no earlier than the peak metamorphism (490 Ma) and no later than the intrusion of pegmatite veins (389 ± 5 Ma). The distribution of graphite deposits, graphite orebody morphologies, mineral associations, and geochemical data suggest that the genesis of graphite deposits in Madagascar is linked to mantle-derived fluid filling rather than the metamorphism of sediments, as previously suggested. These findings have important implications for similar deposits in Madagascar and potentially globally.

Characteristics of mesoscale eddies in the Mozambique Channel.

The mesoscale eddy characteristics of the Mozambique Warm Current were investigated by detecting and tracking satellite altimetry data from 2010 to 2019. A total of 1,086 eddies were identified in the Mozambique Channel, comprising 509 cyclonic eddies and 577 anticyclonic eddies. The results revealed that the bay area on the northwest coast of Madagascar was the main hotspot of eddy generation, and the mean amplitude and radius of the anticyclonic eddies in the Mozambique Channel were 24.23 cm and 82.7 km, respectively, which are larger than those of the cyclonic eddies. Local wind forcing had a significant impact on the formation of mesoscale eddies in the Mozambique Channel. In winter, the wind stress in the northern and southern areas of the Mozambique Channel exhibited a strong correlation with the distribution of eddy kinetic energy (EKE), where both monsoonal winds in the north and trade winds in the south could facilitate mesoscale anticyclonic eddy formation. In addition, the variability in the number of anticyclonic and cyclonic eddies in the Mozambique Channel may have exerted a significant influence on the seasonal anomalous fluctuations in local sea surface temperatures (SSTs). This study presented a novel analysis of the mesoscale eddy characteristics in the Mozambique Channel.

The agroforests of the east coast of Madagascar

This article explores the significance, challenges, and future prospects of Madagascar’s cash crops: vanilla, cloves, lychees, black pepper and cinnamon. Cultivated by small-scale farmers in biodiverse agroforestry plots, these cash crops have historical importance in Madagascar's export-oriented economy that has seen Madagascar become the world's leading producer of vanilla, the second largest exporter of cloves and essential clove oil, and the leading exporter of lychees to the European market. Despite contributing substantially to the country's exports, farmers remain vulnerable, as the markets for these products are controlled by global food industry giants and are subject to significant price fluctuations. Other factors that contribute towards farmer’s vulnerability include climate change, local security conditions, competition from other producing countries and the introduction of synthetic vanillin. Despite the volatilities, farmers’ income and food security remain tied to these cash crops. Diversification is recommended to ensure better resilience against volatile conditions, including diversification of crops, land management practices, and product uses. By adapting agroforests to integrate a variety of cash crops and food crops, farmers’ income and food security will be protected long-term. Further research on agro-biodiversity management is now needed to continue to mitigate market dynamics and environmental challenges.

A Cocktail of Plankton and Organochlorines for Whale Shark in the Foraging Areas of Nosy Be (Madagascar)

Seas and oceans are contaminated by persistent organic pollutants (POPs), which are released into the environment by human activities. The chemical-physical properties of POPs induce high persistence and toxicity in marine organisms from the lowest to the highest trophic levels. Phyto- and zooplankton are at the base of the food chain, and they can adsorb and accumulate these xenobiotic compounds. Therefore, all planktophagous species, including the whale shark (Rhincodon typus), are susceptible to ingesting these contaminants during feeding. From October to December, whale sharks migrate along the north-west coast of Madagascar in search of dense patches of plankton. During scientific expeditions to the whale sharks’ foraging areas in the waters of the island of Nosy Be (which is in the north-west of Madagascar), plankton samples were taken. In these samples, the presence and levels of some chlorinated xenobiotics (HCB, DDT and its metabolites, and PCBs) were evaluated in order to estimate the possible impact of whale shark diet on organochlorine (OC) accumulation. The fresh plankton biomass sampled from this region did not seem to be sufficient for the sustenance of the animals, which suggests that the daily contamination input of Rhincodon typus individuals, depending on their plankton diet, is minimal.

Do loggerhead sea turtle (Caretta caretta) gut contents reflect the types, colors and sources of plastic pollution in the Southwest Indian Ocean?

We analyzed plastic debris ingested by loggerheads from bycatch between 2007 and 2021 in the Southwest Indian Ocean (SWIO). We also analyzed plastic debris accumulated on beaches of the east coast of Madagascar as a proxy for ocean plastics to compare the characteristics of beached plastics and plastic ingested by turtles. We conducted a “brand audit” of the plastics to determine their country of origin. An oceanic circulation model was used to identify the most likely sources of plastics in the SWIO. In total, 202 of the 266 loggerheads analyzed had ingested plastics. Plastics categorized as “hard” and “white” were equally dominant in loggerheads and on beaches, suggesting no diet selectivity. Both the brand audit and circulation modeling demonstrated that Southeast Asia is the main source of plastic pollution in the region. This study demonstrates that loggerheads can be used as bioindicators of plastic pollution in the SWIO.

Seed Oil Extraction of Cucurbita maxima Duchesne Growing in Madagascar: Impact of Storage and Use of a Cineole–Rich Essential Oil as a Green Solvent

The performance of a cineole-rich essential oil as an extraction solvent for vegetable oil was studied. This essential oil was obtained from Melaleuca quinquenervia (Cav.) St Blake Myrtaceae, commonly called niaouli, an invasive plant on the eastern coast of Madagascar. The whole essential oil was used without preliminary isolation of terpenes. Experimentation was carried out with Cucurbita maxima Duchesne Cucurbitaceae seeds. The Soxhlet method was used for the oil extraction, and solvent recovery was performed by hydrodistillation. Niaouli essential oil allowed a better extraction yield of 39% compared to hexane, with 36%. The linoleic acid content of the oil was also higher: 37.19% against 7.25% for hexane. After 30 weeks of storage, the seed powder linoleic acid content increased to 44.99% for niaouli oil against 25.00% for hexane oil. With the screw press extraction method, the best yield of 13.00% was obtained with roasting pretreatment while heating at 60°C. However, the best oleic acid content of 45.36% was obtained at 50°C. It was demonstrated that the seed powder underwent biochemical changes during storage which were similar to intracellular catabolic reactions of fatty acids. The high expenses induced by the deterpenation process in terms of cost and energy limit the diffusion and the development of the use of terpenes as alternative solvents. The results of this research support the idea that it is possible to avoid this costly step by directly using the entire essential oil since this can provide a vegetable oil of good quality.

Spatial ecology of the invasive Asian common toad in Madagascar and its implications for invasion dynamics

Invasion dynamics are determined, among other aspects, by the spatial behaviour of invasive populations. The invasive toad Duttaphrynus melanostictus is spreading inland from the eastern coast of Madagascar, causing considerable ecological impacts. Understanding the basic factors determining the spread dynamics can inform management strategies and provide insights into spatial evolutionary processes. We radio-tracked 91 adult toads in three localities along the invasion gradient to determine whether spatial sorting of dispersive phenotypes is occurring, and investigate intrinsic and extrinsic determinants of spatial behaviour. Overall, toads in our study appeared as habitat generalists, and their sheltering behaviour was tied to water proximity, with toads changing shelter more frequently closer to waterbodies. Toads showed low displacement rates (mean = 4.12 m/day) and quite a philopatric behaviour but were able to perform daily movements of over 50 m. We did not detect any spatial sorting of dispersal-relevant traits nor sex- or size-biased dispersal. Our results suggest that toads are more likely to expand their range during the wet season, and that the range expansion is probably dominated by short-distance dispersal at this stage of the invasion, although a future increase in invasion speed is expected, due to the capacity for long-distance movements of this species.

Decreasing diarrhea cases through on-site sodium hypochlorite production in Madagascar

Abstract Schools from Sainte-Marie Island, off the east coast of Madagascar, participated in water, sanitation, and hygiene (WASH) programs. We report an association between the program, the sustainable access to water treatment (WT) in 20 schools, and the impact on diarrhea incidence in the region. We performed a quasi-experimental longitudinal study on the program's sustainability by accessing the continuation of point-of-use (POU) water chlorination, safe water storage (SWS), and handwashing practices on the diarrhea cases of children. Patient files from 10 health centers near the schools were consulted. Sodium hypochlorite was locally produced by the students for WT and the program's sustainability was accessed between 2016 and 2021. After the intervention, 40% of water sources were entirely replaced and 60% received improvements. A student's water club, guided by teachers, was responsible for all activities related to WT. The health centers around the schools participating in the program saw diarrhea cases drop by 58% between 2018 and 2021. There appears to be an association between a decrease in diarrhea cases and the program's implementation. The strategy used can be replicated. Nevertheless, the program's success is multifactorial, depending on community engagement, adapted technology, funding, and governmental support to ensure sustainability.

Revisiting Battistini: Pleistocene Coastal Evolution of Southwestern Madagascar

The study of paleo shorelines, particularly of those formed during the late Quaternary, provides robust insights into past climate variability. Advances in surveying techniques and chronological methodologies have dramatically improved the inter-comparability of regional and basin-wide paleo shoreline surveys. However, these advances have been applied unevenly across the globe. This is especially true in southwestern Madagascar, where, in the 1960s and 1970s, emerged Pleistocene beach and reef facies were first described in detail and dated to Marine Isotope Stage (MIS) 5a using U–Th alpha activity counting by french geologist René Battistini. Now, 50 years on, no further analysis of the coastal sequence has been made. In this study, we present an updated late Pleistocene coastal evolution model for the southwestern Madagascar coast. Utilizing a combination of Structure-from-Motion/Multi-View Stereo techniques and differential Global Navigation Satellite System surveys, we have created five high-resolution 3D outcrop reconstructions that have, in turn, been chronologically constrained using 10 U-series ages from both in situ and reworked coral samples. Our data suggest that the emerged reef was deposited during MIS 5e (∼125 ka), then was covered by intertidal and beach sediment (including redeposited coral clasts of MIS 5e age), and finally capped off by thick eolianites. This sequence would suggest that the local sea level must have remained stable throughout MIS 5e in order to allow for the progradation of both the beach and reef environments.

From shifting rice cultivation (tavy) to agroforestry systems: a century of changing land use on the East Coast of Madagascar

From shifting rice cultivation (tavy) to agroforestry systems: a century of changing land use on the East Coast of Madagascar

Ensemble Three-Dimensional Habitat Modeling of Indian Ocean Immature Albacore Tuna (Thunnus alalunga) Using Remote Sensing Data

This study evaluated the vertical distribution of immature albacore tuna (Thunnus alalunga) in the Indian Ocean as a function of various environmental parameters. Albacore tuna fishing data were gathered from the logbooks of large-sized Taiwanese longline vessels. Fishery and environmental data for the period from 1998 to 2016 were collected. In addition to the surface variable, the most influential vertical temperature, dissolved oxygen (OXY), chlorophyll, and salinity layers were found at various depths (i.e., 5, 26, and 53 m for SST; 200, 244, and 147 m for OXY; 508, 628, and 411 for SSCI; and 411, 508, and 773 m for SSS) among 20 vertical layers based on Akaike criterion information value of generalized linear model. Relative to the 20 vertical layers base models, these layers had the lowest Akaike information criteria. For the correlation between the standardized and predicted catch per unit effort (CPUE), the correlation values for the generalized linear model (GLM), generalized additive model (GAM), boosted regression tree (BRT), and random forest (RF) model were 0.798, 0.832, 0.841, and 0.856, respectively. The GAM-, BRT-, and RF-derived full models were selected, whereas the GLM-derived full model was excluded because its correlation value was the lowest among the four models. From March to September, a higher immature albacore standardized CPUE was mainly observed from 30°S to 40°S. A northward shift was observed after September, and the standardized CPUE was mainly concentrated at the south coast of Madagascar from November to January.

Finding food in the hunger season: A mixed methods approach to understanding wild plant foods in relation to food security and dietary diversity in southeastern Madagascar

In many rural farming societies, wild plant foods (WPFs) continue to play an important role in everyday diets as well as in coping with hunger during food shortages. However, WPF collection and consumption may pose challenges to biodiversity conservation efforts (e.g., in protected areas), and some “famine foods,” foods not typically eaten under normal conditions, may have deleterious health impacts. Using data from a cross-sectional survey of 328 smallholder farmers and fisherfolk living in 15 villages surrounding Manombo Special Reserve on the southeastern coast of Madagascar, we examine the relationship between food security, dietary diversity, and consumption of WPFs, specifically giant aquatic arrowhead or via (Typhonodorum lindleyanum) and Polynesian arrowroot or tavolo (Tacca leontopetaloides), during the region's main lean season. We complement survey findings with focus group interviews to document traditional ecological knowledge and perceptions of these WPFs, including how tavolo and via are rendered edible, as well as human health effects from collecting, preparing, and eating them. Using multilevel logistic regression modeling, we found that consumption of these WPFs were significantly associated with inadequate nutrition among farmers. Wealthier households were less likely to consume these WPFs as a coping strategy during food insecure periods, while larger and more food insecure households were more likely to consume them. These findings reaffirm the importance of access to natural areas and support the design of protected area conservation strategies that honor local foodways and consider WPFs that serve as food safety nets for more vulnerable populations.

Risk factors for intestinal parasite portage in an informal suburb on the West coast of Madagascar

The deprived area of the Metzinger Valley in the city of Mahajanga has many healthcare concerns due to repeated flooding during the rainy season. Improving this health situation requires a better knowledge of the pathogens present in this area and of the risk factors favoring their propagation. The aim of this study was to analyze the relationship between the household socioeconomic status and the presence of parasites in the faeces of children between 1 and 10 years of age in order to determine the risk factors for intestinal parasitosis. The study included 746 children, of whom 30% were infected with parasites. Entamoeba coli, a good indicator of environmental fecal contamination, was the most prevalent parasite with an observation frequency of 16.7% followed by Giardia lamblia with a prevalence of 10%. For helminths, Trichuris and Ascaris were the most prevalent respectively 5.4% and 1.8%. A large heterogeneity in the prevalence of parasites was observed from one neighborhood to another. However, multivariate analysis showed that these differences were not related to environmental factors or household structure, but rather to the economic level of the family, the education level of the mother as well as the age of the child. For example, the prevalence of Giardia decreased from 23.5% to 8% for children of mothers with little education to those with higher education, respectively. For E. coli, the prevalence is higher among poor households and school-aged children. In the frame of IRCOD project, mothers are being sensitized to hygiene and risk factors for transmission by intestinal parasites and the present study proposes a multidimensional approach as an assessment tool.

Analysis of the 10–20-Day Intraseasonal Oscillation in the Indian Ocean Using Surface Winds

The 10–20-day mode of surface wind is examined in the Indian Ocean, with special reference to the Arabian Sea, Bay of Bengal, equatorial, southern, and southeastern Indian Ocean during a strong (1994), weak (2002), and normal (1995) southwest monsoon season. Results indicate the 10–20-day mode of surface winds in the Bay of Bengal, southern Indian Ocean, and southeastern Indian Ocean is more energetic than in other regions. The strongest 10–20-day signal is found to be in the southeastern Indian Ocean, where 45% of surface wind variability can be explained by this mode during a strong monsoon year. Composite analysis based on a time series in this region revealed a positive surface wind anomaly that appears at 60°E, centered on 15°S, and propagates zonally eastward to 90°E before reflecting back to propagate westward and then disperse off the coast of Madagascar. It is proposed that this oscillating positive wind anomaly is a feature of the southernmost cell of the 10–20-day convective double-cell structure that has extended farther south into the southern Indian Ocean and that this mode connects the northern and southern Indian Ocean through surface winds and atmospheric convection through the motion of the linked double-cell structure.

Evaluation of the vulnerability of groundwater to nitrogen pollution in the commune of Mananara Avaratra by the SINTACS method

The urban commune of Mananara Avaratra, located on the east coast of Madagascar in the Analanjirofo region, is characterized by alluvial soils, mainly sandy and ferruginous, and a tropical climate. Groundwater is considered as the main source of drinking water for the local population although the presence of pollution by nitrogen compounds has been a serious environmental problem for more than a decade This study aimed at developing a groundwater vulnerability model for nitrate and ammonium as a protective measure. Based on the intrinsic vulnerability determined by the SINTACS model, the influence of anthropogenic parameters related to nitrogen sources and groundwater use on contamination was verified using GIS. Chemical analyses showed high concentrations of nitrate (136.987 mg.l-1) and ammonium (1.120 mg.l-1) in the samples. The high nitrate and ammonium concentrations were found in the northern subwatershed, probably due to the area impacted by urbanization by urbanization, where the groundwater vulnerability index is high (high index is 197 - 210 and for the very high ones 215 - 223). On the other hand, the concentrations in the southern subwatershed are lower, and the index is moderate (137 - 178). In order to prevent the contamination of groundwater by nitrogen, it is necessary to develop management policies on surface land use and groundwater, as well as to continuously monitor the latter.

Coming from elsewhere: the preponderance of introduced plant species in agroforestry systems on the east coast of Madagascar

Coming from elsewhere: the preponderance of introduced plant species in agroforestry systems on the east coast of Madagascar

Habitat use by the island lemurs of Nosy Be, Madagascar.

Madagascar's lemurs are threatened by forest loss, fragmentation, and degradation. Many species use flexible behaviors to survive in degraded habitat, but their ability to persist in very small areas may be limited. Insular lemurs, like those found on Nosy Be, an island off the northwestern coast of Madagascar, are at heightened risk of sudden population declines and extirpation. Nosy Be is home to two Critically Endangered species-the endemic Nosy Be sportive lemur (Lepilemur tymerlachsoni) and Claire's mouse lemur (Microcebus mamiratra)-as well as the Endangered black lemur (Eulemur macaco). Most of the remaining forest on Nosy Be is protected by the 862-ha Lokobe National Park. To document how Nosy Be lemurs use their restricted habitat, we conducted vegetation and reconnaissance surveys on 53 transects in and around Lokobe. We collected data on tree size, canopy cover, understory visibility, and elevation for 248 lemur sightings. We used a spatially explicit, multi-species occupancy model to investigate which forest-structure variables are important to lemurs. Our results represent some of the first data on habitat use by insular lemurs. Black lemurs preferred significantly larger trees and areas with less dense understory. They also occurred significantly less outside of Lokobe National Park, even when accounting for sampling effort and geography. The distributions of the sportive and mouse lemurs were not related to the forest structure variables we documented, but they did negatively predict each other-perhaps because their habitat requirements differ. These results also underscore the importance of the national park to protecting the black lemur population on Nosy Be and raise questions about what factors do influence the distribution of Nosy Be's smaller lemurs. Close monitoring is needed to prevent these populations and the ecosystem services they provide from disappearing, as have other island lemurs.

Reviews and syntheses: Physical and biogeochemical processes associated with upwelling in the Indian Ocean

Reviews and syntheses: Physical and biogeochemical processes associated with upwelling in the Indian Ocean