Rodrigues Island Research Articles

A speleothem record of hydroclimate variability in northwestern Madagascar during the mid-late Holocene

We present a continuous high-resolution precisely dated multiproxy record of hydroclimate variability at Anjohibe cave in northwestern Madagascar using speleothem AB13. The record spans from ~4484 y BP to ~2863 y BP. Stalagmite δ18O, δ13C and Sr/Ca ratios show very similar changes in hydroclimate. The mechanism controlling Sr/Ca changes, however, from prior calcite precipitation to degree of dolomite dissolution at about 4 ky BP. Our record is also in good agreement with previously published speleothem records from the same area. This agreement and multiproxy consensus indicate that AB13 provides a robust record of hydroclimate variability, including a continuous record of hydroclimate variability across the 4.2 ka event. This 4.2 ka event in Madagascar is marked by two distinct periods of drying between ~3900 y BP to 4300 y BP. A dry 4.2 ka event at this Southern Hemisphere site helps limit possible mechanisms for the event, indicating that a meridional shift to the south in the ITCZ is not responsible for the 4.2 ka event. In addition, the 4.2 ka event does not stand out as a unique dry period in our record. The longest and driest period of the record lasted ~300 years with peak dryness at ~3000 y BP. Our record differs significantly from a speleothem record from Rodrigues Island, located ~1800 km to the east of our study area in Madagascar suggesting different climatological controls on northwest Madagascar and more oceanic sites to the east.

First Report of Diseases and Compromised Health Conditions on Hard Corals around Rodrigues Island, Southwest Indian Ocean

Coral diseases represent a prominent menace to coral reefs and to the associated ecological services they provide to the surrounding coastal communities. Studies on diseases and compromised health conditions (CHCs) on hard corals in the Southwest Indian Ocean (SWIO) are scarce, and their consequences are often overlooked. This study aimed to establish the baseline prevalence of diseases and CHC of hard corals around Rodrigues Island. Coral disease and CHC prevalence were visually assessed using 2 m × 50 m belt transects at eight sites around the island. This is the first report of four coral diseases, namely White Plague (WP), White Syndrome (WS), Black Band (BB), and Growth Anomalies (GA), and two CHCs, two forms of Pink Pigmentation Responses (PPR)—Pink Patches (PP) and Pink Line Syndrome (PLS)—observed on six genera of hard corals from the island of Rodrigues. PP on Fungia (15.92 ± 5.65%), followed by the WS on Montipora (4.67 ± 3.72%) and GA on Gardineroseris (4.16 ± 4.16%), so far unreported from the SWIO, were the most prevalent around the island. The least prevalent disease was BB on Montipora (0.13 ± 0.13%). Although the overall disease and CHC prevalence for Rodrigues Island (0.98 ± 0.30%) were much lower than the surrounding islands in the SWIO, the observations of these diseases and CHCs on hard corals and relevant environmental parameters warrant further in-depth characterization to better inform coral reefs management and conservation actions.

Diversity, density and photo-physiology of micro-phytoplankton from degraded and non-degraded reefs around Rodrigues Island, Western Indian Ocean

Abstract. Soondur M, Kaullysing K, Ramah S, Bhagooli R. 2023. Diversity, density and photo-physiology of micro-phytoplankton from degraded and non-degraded reefs around Rodrigues Island, Western Indian Ocean. Indo Pac J Ocean Life 7: 108-121. This study aimed at investigating the variations in micro-phytoplankton diversity, density and photo-physiology between a degraded, Anse Aux Anglais (AAA) in the north, and a non-degraded, Port Sud-Est (PSE) in the southeast, reefs around Rodrigues Island, Republic of Mauritius. Sampling was carried out in summer and winter seasons from 2016 to 2019 at the two sites, PSE and AAA. Micro-phytoplankton samples were collected using a plankton net of 5µm and conserved with Lugol’s solution. Physico-chemical parameters namely temperature, dissolved oxygen, salinity, and ph were recorded in situ. Seawater samples were collected for nutrient and chlorophyll-a concentration analyses. The Total Micro-Phytoplankton Densities (TMPD) did not differ seasonally for the whole period from 2016 until 2019 but there was a significant difference station-wise (P < 0.01), with higher TMPD recorded at the non-degraded reef of PSE. PSE exhibited the higher species diversity. Diatoms and dinoflagellates were more abundant at PSE while the cyanobacteria showed higher densities at AAA. Genera like Licmorphora, Gonyaulax, Polykrikos, Trichodesmium, and Lygnbya, reported worldwide to possibly cause mortality and/or changing community structure of corals, were recorded at both PSE and AAA though not at blooming densities. Photo-physiological assessment of micro-phytoplankton, using a Diving Pulse-Amplitude-Modulated (D-PAM) fluorometer, varied significantly both seasonally and spatially. These findings indicated that the non-degraded reef site had higher micro-phytoplankton density, diversity and photo-physiological performance than the degraded one, implying that degraded reefs may not only be characterized by the benthic cover and/or their health status but also the biological parameters from the water column.

New insights into the diversity of cryptobenthic Cirripectes blennies in the Mascarene Archipelago sampled using Autonomous Reef Monitoring Structures (ARMS).

Autonomous Reef Monitoring Structures (ARMS) are artificial mini-reefs designed for standardized sampling of sessile and small motile cryptobenthic organisms. ARMS are also effective for collecting small cryptobenthic fishes, such as the combtooth blennies of the genus Cirripectes. Recent studies discovered several Cirripectes species endemic to islands or archipelagos, in spite of the generally broad distributions of tropical and subtropical blennies. Thus, to evaluate the diversity and distribution of Cirripectes species in the Mascarene Archipelago, a little-studied region but an important biodiversity hotspot, complete mitochondrial genomes, and nuclear rhodopsin genes were sequenced for 39 specimens collected with ARMS deployed on outer reef slopes at Reunion and Rodrigues islands. Mitochondrial COI sequences were analyzed to integrate these specimens within the largest dataset of publicly available sequences. Three species were found in the Mascarene Archipelago, Cirripectes castaneus, Cirripectes randalli, and Cirripectes stigmaticus. C.castaneus and C.stigmaticus both have an Indo-Pacific distribution with several haplotypes shared among distant localities. In agreement with the literature, C.randalli shows a small-range endemism restricted to the Mascarenes. We confirmed the presence of C.castaneus, C.randalli, and C.stigmaticus in Rodrigues, and the presence of C.stigmaticus in Reunion. This study contributes to filling the gaps in taxonomic and molecular knowledge of the reef cryptobiome in the South-West Indian Ocean, and provides the first complete mitogenomes for the genus, a crucial step for future molecular-based inventories (e.g., eDNA).

Differential photo-physiological responses of two giant clam species to elevated temperature stress from Rodrigues Island, Western Indian Ocean

Abstract. Ramah S, Kaullysing D, Soondur M, Taleb-Hossenkhan N, Bhagooli R. 2023. Differential photo-physiological responses of two giant clam species to elevated temperature stress from Rodrigues Island, Western Indian Ocean. Indo Pac J Ocean Life 7: 64-70. Bleaching events leading to mass mortality of coral reef and its associated symbiotic organisms have become an alarming issue worldwide. However, as compared to corals, little has been documented regarding giant clams’ (Tridacnines) thermal photo-physiological susceptibility. Triplicate specimens of the small giant clam Tridacna maxima and the fluted giant clam T. squamosa collected from the lagoon of Rodrigues Island, Western Indian Ocean were exposed at two temperatures, 29°C and 32°C, under a constant low light intensity of approximately 200 µmol quanta m-2 s-1 over a 12-hour duration. The photo-physiological parameters namely, effective quantum yield of photosystem II (?PSII), relative maximum Electron Transport Rate (rETRmax) and maximum Non-Photochemical Quenching (NPQmax) were determined using a Diving Pulse-Amplitude-Modulated (D-PAM) fluorometer prior to and after 3 and 12 hours of exposures. At 29°C the photo-physiological parameters did not vary significantly for both species. At 32°C, T. squamosa and T. maxima exhibited significant declines in ?PSII as at 3 and 12 hours, respectively. The rETRmax of T. squamosa showed a significant decrease at 3 hours while both species showed a significant reduction in their NPQmax functioning as from 3 hours. The experiment also recorded the disintegration of the mantle tissue in T. squamosa after 12 hours. These findings indicate that T. squamosa is thermally more susceptible than T. maxima. Further in-depth investigations on symbionts genetic types and antioxidant responses of both the Tridacna host and symbionts are required to thoroughly understand giant clams’ variable heat stress responses in the era of ocean warming.

Optimizing on utility-scale solar for conservation of pristine landscapes and ecosystems: the case of Rodrigues Island

Optimizing on utility-scale solar for conservation of pristine landscapes and ecosystems: the case of Rodrigues Island

Spatial distribution of surface chlorophyll a and micro-phytoplankton density and diversity around two islands and at two banks of the Mascarene region

The present study validated the use of AquaMODIS sea surface chlorophyll a (Chla) concentrations and investigated the spatial variation in density and diversity of micro-phytoplankton around two islands and two fishing banks of the Mascarene region. The study included areas around Mauritius (MRU) and Rodrigues (ROD) Islands, at Nazareth (NZ) Bank, and in the Joint Management Area (JMA) between the Republic of Mauritius and the Republic of Seychelles, more specifically at the Saya de Malha (SM) Bank. The AquaMODIS data were based on 67 match-up data points of in-situ against satellite Chla concentrations. The micro-phytoplankton community structure was investigated by determining the density variation and using the Shannon Wiener (H’) and Evenness (Evar) diversity indices. The satellite and in-situ Chla data were significantly and positively correlated when pooled for the four sites studied (R2 = 0.441; r = 0.642, P < 0.01), and when analysed separately for islands (R2 = 0.480; r = 0.694), and banks (R2 = 0.233; r = 0.483). However, the Chla satellite values tended to be lower than the in-situ Chla data. The highest densities of micro-phytoplankton were observed in the eastern and northern regions for MRU and ROD, respectively. The most dominant genera of micro-phytoplankton were Coscinodiscus, Navicula, Chaetoceros and Ceratium. The Shannon-Wiener diversity index values for diatoms were all above 2.5 with waters around the islands having higher diversity compared to the banks. Overall, the different micro-phytoplankton around the islands, except for the group of cyanobacteria at ROD Island, were more evenly distributed (Evar > 0.6) compared to the banks. This study indicated that AquaMODIS Chla satellite data is valid and may be potentially used as a proxy for in-situ Chla concentration on the Mascarene Plateau. The results of this study also provide detailed insight into the spatial variation in micro-phytoplankton density and diversity on the Mascarene Plateau in the Western Indian Ocean. Further long-term studies are warranted to thoroughly understand the temporal (including seasonal and inter-annual) variations in Chla and micro-phytoplankton distribution for adequate and appropriate management of these ocean territories.

Rodriguez Island

This is a datasheet on Rodriguez Island.

New Phytoseiidae (Acari: Mesostigmata) of Mascareignes and Comoros Archipelagos (Indian Ocean): one new record, three new species groups and description of six new species and of six unknown males

Faunas of Phytoseiidae of the Mascareignes Archipalago (Réunion, Mauritius and Rodrigues Islands) and of the Comoros Archipelago (Mayotte, Anjouan, Mohéli and Grande Comore Isands) were recently investigated by authors of this paper and results were published in seven already published papers. We described in this eighth paper six species new to science and six unknown males collected during these surveys.

Review of the cardinalfishes of the genus Cercamia (Percomorpha: Apogonidae) of the Red Sea and Indian Ocean with descriptions of three new species.

The representatives of Cercamia from the Indian Ocean including Red Sea are reviewed and three new species are described: Cercamia spio n. sp., formerly known as C. eremia (Allen, 1987), is described from 14 specimens, 1733 mm SL, collected in 1015 meters from northern (Duba) to central (Jeddah) Saudi Arabia and from Jezirat Faraun, Egypt. It also has been photographed from the Gulf of Aqaba (Dahab, Egypt) and El Quseir (Mangrove Bay, Egypt). The new species is distinguished from other Indian Ocean Cercamia in having fewer developed gill rakers on lower limb (usually 11 versus usually 1213) and fewer anal-fin rays (11 versus usually 1213). Another new species, Cercamia laamu, n. sp., is described only from the Maldives and Chagos Archipelago based on five specimens 16.030.5 mm SL. It differs from all Indian Ocean Cercamia in having more greater number of the second dorsal-fin rays (10 versus usually 9), and a translucent body devoid of reddish marks versus small reddish dots and crisscross lines. The third new species, Cercamia mascarene, n. sp., is described from 40 specimens 1936 mm SL, from Rodrigues Island, Mauritius. It differs from Cercamia eremia in having a greater number of developed gill rakers on the lower limb of the first gill arch (usually 13 versus usually 12). Free neuromasts and cephalic pores are illustrated for Cercamia mascarene and free neuromasts on the body and caudal fin are illustrated for Japanese specimens of C. cf. eremia. New diagnoses are provided for Cercamia cladara, the type species of the genus, and C. eremia. A map of collection locations for species of Cercamia is presented to show the breath of known occurrences in the Red Sea and Indian Ocean. A new morphologic diagnosis is provided for Cercamia. A phylogenetic analysis of the barcoding portion of the mitochondrial COI gene, including all available sequences from members of the genus Cercamia, displays a much higher species diversity than expected, with high levels of divergence among recognized and undescribed species. A key to the described Indian Ocean species is provided.

An assessment of soft coral community (Octocorallia; Alcyonacea) around Mauritius and Rodrigues Islands — New records of soft corals

This study aims to assess the soft corals community around Mauritius and Rodrigues Island due to the limited research on the abundance and diversity of soft corals in the area. Seven soft corals species are newly reported from Mauritian waters. Triplicates of 5-metreline transect were used to survey soft corals at twelve different monitoring sites. Of the sites monitored for soft coral occurrence, the highest Margalef richness index and Shannon index (H’) values were obtained at Port Mathurin for Rodrigues Island and at Les Salines for Mauritius. Identification was carried out using both morphological characters and a DNA-based marker. The morphological identification process was based on the external form and colouration, type of colony growth; the type of polyps and colonies and sclerites analysis. 41 different species showed dissimilar characteristics, and results grouped the colonies to three different families; 32 colonies of Alcyoniidae, 3 of Nephtheidae and 6 of Xeniidae were obtained. To ascertain morphological classification, the longest non-coding region of the mitochondrial COI-COII intergenic spacer (IGS) (consisting of 122 nucleotides) was used to construct a molecular phylogeny that included 21 species of octocorals. The COI-COII IGS phylogeny recovered 5 well supported clades, which did not tally with the cladogram based on morphological characters. Three dendrograms based on morphological characters were constructed where the first one involved mapping of all the morphological characters onto the tree, the second one was based mainly on the type of sclerites present and the third one based on the collection depth of the samples. The dendrogram based on morphological markers clustered all the soft corals from the Alcyoniidae family aside from the other families. The second dendrogram clustered all the soft corals from the genus Sinularia, Lobophytum, Sarcophyton as well as Cladiella kashmani together, away from the soft corals with distinct sclerite form. Furthermore, the third dendrogram clustered the soft corals into 2 major clades, one clade clustering the soft corals which are ubiquitous and a larger clade including all soft corals collected from a depth of 0 m to above 20 m. As documented by other studies on octocorals, construction of the phylogenetic tree has led to an appreciation of the importance of genetic work which has been overlooked while using traditional morphological characters.

A survey of Calliphoridae and Mesembrinellidae (Diptera) in semideciduous seasonal forest, Paraná, Brazil

Calliphoridae and Mesembrinellidae include Diptera species that are good indicators of changes in forest environments. The present work aimed to inventory the Calliphoridae and Mesembrinellidae in Ilha Grande National Park and correlate the abundance of these organisms with environmental variables. Adult dipterans were collected during two expeditions in 2019 using two sampling methods, a Malaise trap and baited traps, distributed on two islands in the park. During the study, 1,007 individuals of 12 species of Calliphoridae and four species of Mesembrinellidae were collected. Family Calliphoridae was more abundant (97.12%). The abundance of native species showed a strong negative correlation with the abundance of the genus Chrysomya. Rodrigues Island (Island I) had higher diversity levels and no species of Chrysomya were recorded in this area, which may indicate a greater degree of environmental preservation. The results indicate that human action in natural environments can negatively impact species diversity, as found in Ilha Grande National Park that, historically, was partially occupied and is still in the process of regeneration.

Persistent organic pollutants in sea bird eggs from the Indian Ocean's Mascarene Basin

We report the concentrations of persistent organic pollutants (POPs) in seabird eggs from St. Brandon's Atoll, a tropical island system in the western Indian Ocean. Ten eggs each of sooty terns (Onychoprion fuscatus), fairy terns (Gygis alba), and common noddies (Anous stolidus) were collected from the atoll. For a terrestrial reference, we analysed three feral chicken (Gallus gallus domesticus) eggs from the same location. Sooty tern eggs contained the highest mean concentrations of three chemical classes: ƩCHL3 (0.21 ng/g wm; wet mass), ƩPCB10 (1.5 ng/g wm), and ƩPBDE6 (1.1 ng/g wm). Fairy tern eggs contained the highest mean concentrations of HCB (0.68 ng/g wm) and ƩCHB5 (0.83 ng/g wm). The chicken eggs contained the highest mean concentrations of ƩDDT3 (2.6 ng/g wm), while common noddy eggs contained the highest mean concentrations of ƩHCH2 (0.5 ng/g wm). We surmise that the differences in chemical composition between species reflect different pollutant compositions in prey from the bird's different foraging ranges. The sooty terns foraging offshore contained higher POPs concentrations than the nearshore-foraging common noddies. Fairy tern eggs contained intermediate concentrations, commensurate with their intermediate foraging. Inter-island differences in contaminant concentrations were seen between eggs of the common noddies from St. Brandon's Atoll and Rodrigues Island, 520 km to the south-east. Concentrations of contaminants found in this study were lower than values quantified by other studies, making St. Brandon's Atoll an ideal reference site to monitor background concentrations of POPs in the tropical Indian Ocean.

Predicting seasonal movements and distribution of the sperm whale using machine learning algorithms.

Implementation of effective conservation planning relies on a robust understanding of the spatiotemporal distribution of the target species. In the marine realm, this is even more challenging for species rarely seen at the sea surface due to their extreme diving behavior like the sperm whales. Our study aims at (a) investigating the seasonal movements, (b) predicting the potential distribution, and (c) assessing the diel vertical behavior of this species in the Mascarene Archipelago in the south‐west Indian Ocean. Using 21 satellite tracks of sperm whales and eight environmental predictors, 14 supervised machine learning algorithms were tested and compared to predict the whales' potential distribution during the wet and dry season, separately. Fourteen of the whales remained in close proximity to Mauritius, while a migratory pattern was evidenced with a synchronized departure for eight females that headed towards Rodrigues Island. The best performing algorithm was the random forest, showing a strong affinity of the whales for sea surface height during the wet season and for bottom temperature during the dry season. A more dispersed distribution was predicted during the wet season, whereas a more restricted distribution to Mauritius and Reunion waters was found during the dry season, probably related to the breeding period. A diel pattern was observed in the diving behavior, likely following the vertical migration of squids. The results of our study fill a knowledge gap regarding seasonal movements and habitat affinities of this vulnerable species, for which a regional IUCN assessment is still missing in the Indian Ocean. Our findings also confirm the great potential of machine learning algorithms in conservation planning and provide highly reproductible tools to support dynamic ocean management.

Seismic gaps and intraplate seismicity around Rodrigues Ridge (Indian Ocean) from time domain array analysis

Abstract. Rodrigues Ridge connects the Réunion hotspot track with the Central Indian Ridge (CIR) and has been suggested to represent the surface expression of a sub-lithospheric flow channel. From global earthquake catalogues, the seismicity in the region has been associated mainly with events related to the fracture zones at the CIR. However, some segments of the CIR appear void of seismic events. Here, we report on the seismicity recorded at a temporary array of 10 seismic stations operating on Rodrigues Island from September 2014 to June 2016. The array analysis was performed in the time domain by time shifting and stacking the complete waveforms. Event distances were estimated based on a 1-D velocity model and the travel time differences between S and P wave arrivals. We detected and located 63 new events that were not reported by the global networks. Most of the events (51) are located off the CIR and can be classified as intraplate earthquakes. Local magnitudes varied between 1.6 and 3.7. Four seismic clusters were observed that occurred to the west of the spreading segment of the CIR. The Rodrigues Ridge appeared to be aseismic during the period of operation. The lack of seismic activity along both Rodrigues Ridge and the sections of the CIR to the east of Rodrigues may be explained by partially molten upper-mantle material, possibly in relation to the proposed material flow between the Réunion plume and the CIR.

(2772) Proposal to conserve the name Pandanus ornatus Kurz (Benstonea ornata) against P. ornatus W. Bull with a conserved type (Pandanaceae)

(2772) Proposal to conserve the name <i>Pandanus ornatus</i> Kurz (<i>Benstonea ornata</i>) against <scp><i>P. ornatus</i></scp> W. Bull with a conserved type (<i>Pandanaceae</i>)

Maritime Cargo Prioritisation during a Prolonged Pandemic Lockdown Using an Integrated TOPSIS-Knapsack Technique: A Case Study on Small Island Developing States—The Rodrigues Island

Many remote areas, such as island states, are highly dependent on the transportation of cargo, and any disruptions similar to the 2020 pandemic lockdowns can negatively affect their respective supply chains. These disruptions could lead to a severe humanitarian crisis. It is therefore imperative to develop a cargo prioritisation process to ensure that essential commodities are transported. We propose a decision-aid tool that integrates two methods: (a) the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and (b) the knapsack problem. Containers are prioritised based on attributes such as their importance and their economic value. TOPSIS is used to calculate a score for each container and the knapsack problem determines the containers to be imported respecting the transportation capacity constraints. The practical applicability of the model is demonstrated by a case study on a Small Island Developing State. The proposed decision-aid tool could also be extended to be used in disaster relief situations.

Cranial evolution in the extinct Rodrigues Island owl Otus murivorus (Strigidae), associated with unexpected ecological adaptations

Island birds that were victims of anthropic extinctions were often more specialist species, having evolved their most distinctive features in isolation, making the study of fossil insular birds most interesting. Here we studied a fossil cranium of the ‘giant’ extinct scops owl Otus murivorus from Rodrigues Island (Mascarene Islands, southwestern Indian Ocean), to determine any potential unique characters. The fossil and extant strigids were imaged through X-ray microtomography, providing 3D views of external and internal (endocast, inner ear) cranial structures. Geometric morphometrics and analyses of traditional measurements yielded new information about the Rodrigues owl’s evolution and ecology. Otus murivorus exhibits a 2-tier “lag behind” phenomenon for cranium and brain evolution, both being proportionately small relative to increased body size. It also had a much more developed olfactory bulb than congeners, indicating an unexpectedly developed olfactory sense, suggesting a partial food scavenging habit. In addition, O. murivorus had the eyes placed more laterally than O. sunia, the species from which it was derived, probably a side effect of a small brain; rather terrestrial habits; probably relatively fearless behavior; and a less vertical posture (head less upright) than other owls (this in part an allometric effect of size increase). These evolutionary features, added to gigantism and wing reduction, make the extinct Rodrigues owl’s evolution remarkable, and with multiple causes.

Phytoseiid mites of Rodrigues Island (Acari: Mesostigmata)

Rodrigues is one of the three main islands constituting Mascareignes Archipelago, with La Réunion and Mauritius. It belongs to the state of Mauritius. So far, no mite species of the family Phytoseiidae have been reported from this Island. We report in this paper the results of a survey conducted in November 2018 on Rodrigues Island, during which 18 species have been recorded.

A new Lophoturus species (Diplopoda, Polyxenida, Lophoproctidae) from Rodrigues Island, the Republic of Mauritius: morphological and molecular evidence

A new penicillate millipede Lophoturus porchi sp. n. (Lophoproctidae) is described from Caverne de la Vierge, François Leguat Giant Tortoise and Cave Reserve, Rodrigues Island, Mauritius. A comparison of the body length, number of sensilla on the gnathochilarial palp, number of linguiform processes and structure of the labral surface as well as genetics based on the 18S and COI genes indicate that this is a new Lophoturus species.