Tropical Oceanic Islands Research Articles

Gradual change and mosaic pattern of macrofaunal assemblages along depth and sediment gradients in a tropical oceanic island

Gradual change and mosaic pattern of macrofaunal assemblages along depth and sediment gradients in a tropical oceanic island

Environmental DNA metabarcoding reveals the effect of river slope on diadromous fish communities in island rivers

Understanding the natural factors that influence diadromous fish communities in river ecosystems is crucial for effective biodiversity management. However, this remains an unexplored and challenging task. Here, the relationship between river morphology and diadromous fish communities within rivers was explored. We focused on river slope and estuary size, as these may constrain their upstream migration and affect the availability of important nursery grounds for some species. Using environmental DNA metabarcoding, we investigated the diadromous fish communities within 12 rivers of subtropical Yakushima Island, southern Japan, and compared the community differences among rivers with different river slopes and estuary sizes. Fewer diadromous fish species were detected in rivers with steeper slopes and smaller estuaries. Additionally, the community similarity was greater among rivers with analogous gradients and estuary sizes. These results indicate that river slopes exert a species-selective effect on diadromous fish communities by affecting their upstream migration and estuarine habitat availability, thereby playing a crucial role in shaping the composition of these communities within rivers. Conserving gentle-gradient rivers with large estuaries would be crucial for preserving the diversity of diadromous fish species, which play a crucial role in shaping biodiversity especially in rivers of subtropical and tropical oceanic islands.

Conservation management of an abandoned copra plantation at Palmyra Atoll, Northern Line Islands, Pacific Ocean

Coconut palms (Cocos nucifera) cultivated for copra are agricultural resources on many of the world’s low-lying tropical oceanic islands where they provide sustenance and economic value to human communities. However, coconut palms, when dominant in island plant communities, can outcompete native plants for above- and below-ground resources. Furthermore, when coconut palms displace native plant species preferred by seabirds as roosting and nesting habitats, they may disrupt beneficial nutrient pathways in both marine and terrestrial ecosystems. At Palmyra Atoll, located in the Northern Line Islands, Pacific Ocean, evaluation of three methods for controlling coconut palm seedlings (foliar herbicide application, cut-stem, and cut-stem combined with herbicide) showed that mortality was highest with the cut-stem combined with herbicide application. A comparison of herbicide volumes injected directly into stems of mature palms showed that mortality increased with herbicide volume; an injection of 10 ml of undiluted Roundup CustomTM herbicide (53.8% glyphosate) achieved 100% mortality within 8 months.

Multiple island effects shape oceanographic processes and zooplankton size spectra off an oceanic archipelago in the Tropical Atlantic

Pelagic ecosystems around tropical oceanic islands are considered oases of high plankton biomass in the middle of oligotrophic “blue deserts”. To understand the dynamics of such a pelagic ecosystem, we used CTD and ADCP data and zooplankton samples taken from the waters off the remote Fernando de Noronha Archipelago (FNA), Tropical Atlantic. We analyzed how the flow and island topography interactions influence the spatial variability of chlorophyll-a fluorescence and zooplankton abundance, biovolume, and normalized biovolume size spectra (NBSS). We used a 500-μm mesh bongo net to obtain plankton samples in July and August 2010 in areas upstream and downstream of FNA. Zooplankton samples were analyzed with a ZooScan device. Chlorophyll-a peaks and a rise in thermocline indicated a topographic uplift and turbulence downstream of the island, i.e., the “Island Mass Effect”. The NBSS presented a mean slope of −1.19 ± 0.28, and a mean intercept of 3.98 ± 0.87. There were no significant differences in NBSS slopes and intercepts between upstream and downstream areas. Nevertheless, zooplankton and decapod community structures were significantly different between areas: meroplanktonic communities showed higher abundances and biovolumes downstream (p < 0.05). Zoeae of stenopodid cleaner shrimps, anomuran and brachyuran crabs, and fish eggs were significantly more abundant downstream, indicating a “Larval Island Effect”. Distinct peaks in size spectra due to teleost eggs and decapod larvae, downstream of FNA, also indicated a Larval Island Effect. Upstream of the island, there was a higher abundance of gelatinous organisms, holoplanktonic decapods, and advanced stages of brachyuran crabs (“Upstream Island Effect”). Also, copepods, gelatinous organisms, large-sized “other crustaceans” (e.g., euphausiids, amphipods, stomatopod larvae, mysids, etc.), teleost eggs, and stenopodids caused abundance peaks in the size spectra upstream. Our study highlights the need for careful management and conservation of parental spawning stocks of fishes and macroinvertebrates surrounding tropical oceanic islands.

False killer whales (Pseudorca crassidens Cetacea: Delphinidae) along the Pacific coast of Central America and Mexico: Long-term movements, association patterns and assessment of fishery interactions

Introduction: Worldwide, false killer whales (Pseudorca crassidens) are infrequently encountered, yet long-term studies have shown strong site fidelity as well as long-term associations among individuals in several locations. Detailed studies of this species have primarily been conducted around tropical oceanic islands or in the subtropical southern hemisphere.&#x0D; Objectives: We assess movements and association patterns among false killer whales along the Pacific coasts of the USA, Mexico, Guatemala, Nicaragua, Costa Rica including Isla del Coco, and Panama, representing one of the longest-running (albeit non-continuous) studies of this species. We also examine photos for evidence of interactions with fisheries, a known source of mortality to false killer whales.&#x0D; Methods: From Central America, we selected 212 individuals (50 encounter groups) out of 244 individuals (56 encounters) for inclusion in analyses based on photo quality and distinctiveness. Photos were collected on dedicated surveys from 1991-1994 and dedicated and opportunistic surveys from 1998-2022. Other than the effort off the oceanic Isla del Coco (1993-1994), surveys were undertaken in continental shelf waters. Additionally, we selected by photo quality and distinctiveness 124 (33 encounter groups) out of 189 individuals from southern California and Mexico for inclusion in these analyses. Association patterns were analyzed in SOCPROG and movements were analyzed in R.&#x0D; Results: Of the 328 total individuals, 158 (48.2 %) were encountered more than once, and 114 (34.8 %) were re-sighted after a year or more. The longest individual sighting history spanned 26.2 years with six re-sightings over that period between southern Costa Rica and Panama. Association and movement analyses revealed that individuals identified off southern Costa Rica and Panama linked into a single social network, with extensive movements between the two countries. Three individuals encountered off northern Costa Rica were re-sighted off northern Nicaragua, and individuals encountered off Nicaragua were encountered off Guatemala and central mainland Mexico. Nine matches were found among false killer whales between central mainland Mexico and Central America. There were no matches between the mainland coastal waters and the 33 individuals encountered around Isla del Coco. Dorsal fin disfigurements consistent with interactions with line fisheries ranged from 0 to 21 % for individuals within social clusters identified by community division.&#x0D; Conclusions: The infrequency of sightings combined with a high re-sighting rate of individuals and groups from the same area, suggests multiple small populations with large home ranges that include coastal waters. Small populations are sensitive to environmental changes, and as the human population grows, so do the demands on fisheries and ecotourism, which could directly impact the different populations. Additional effort in offshore areas is needed to determine the population status of false killer whales in pelagic waters, how often false killer whales using coastal waters move into pelagic waters, and the relationship between whales in the two habitats.

Checklist of the bees (Hymenoptera, Apoidea) of New Caledonia.

In a world where insects and notably bees are declining, assessing their distribution over time and space is crucial to evaluate species status and highlight conservation priorities. However, this can be a daunting task, especially in areas such as tropical oceanic islands where exhaustive samplings over time have been lacking. This is the case in New Caledonia, an archipelago located in the southwest Pacific. Historical records of bee species are piecemeal and, although contemporary samplings have significantly advanced our knowledge of the bee fauna of New Caledonia, the status of several species remains to be elucidated. Here, we provide an updated checklist of the 51 bee species recorded for New Caledonia using previous publications and personal samplings. We documented their distribution, origin (i.e. endemic, native or alien) and the year and location of their occurrences. Based on the year of their first capture and the year of their last capture, we determined an occurrence status for each species. Thus, 10 years after the last checklist of the New Caledonian bee fauna, the literature review and recent samplings allowed us to add six new species to the list. Half of them are recently introduced species including one firstly mentioned in this paper (i.e. Hylaeusalbonitens). We consider here that 30 species are effectively present on the territory and the presence of 21 species could not be determined due to a lack of data, which highlights the need to increase sampling efforts across New Caledonia. Given the difficulty of exhaustively sampling the entire archipelago, we would recommend taking, as a starting point, altitude environments and areas where data-deficient species were captured. In a broader perspective, biomolecular analyses are crucial to confirm species identifications. This is also needed to make comparisons between archipelagoes and thus clarify the distribution and status of species at the scale of the southwest Pacific.

Unveiling Fernando de Noronha Island's photovoltaic potential with unmanned aerial survey and irradiation modeling

The universalization of electricity still presents significant obstacles to achieving the United Nations Sustainable Development Goals. There are still many remote areas, such as oceanic islands and isolated communities disconnected from the grid, that depend on fossil fuels to make it viable. Fernando de Noronha, a tropical oceanic island in Brazil, is a typical case where replacing the diesel-based power plant for renewable energy is imperative, therefore, it served as a testbed for this investigation. This paper presents the implementation and results of a low-cost framework for assessing the photovoltaic potential of rooftops. Using a real case study, the objective is to explore how effective rooftop photovoltaic systems could be on Fernando de Noronha Island by applying low-cost aerophotogrammetry, geospatial analysis and scenario creation. The first approach was mapping buildings, open spaces and solar obstacles using unmanned aerial photogrammetric survey that delivered high-quality digital elevation surface. The 3D rooftop surfaces fed the solar irradiation models and enabled to compute the photovoltaic potential of suitable rooftops. Findings show that 83.3% of the total building rooftop area was deemed economically viable for photovoltaic installations. Furthermore, 80.0% and 60.0% of the rooftops receive annual irradiation levels >1600 kWh/m2 and 2000 kWh/m2, respectively, indicating high potential for exploiting solar resources on decentralized, highly irradiated rooftops. The scenario with the highest photovoltaic potential is three times higher than the lowest. The results indicate that the suitability of rooftops for various photovoltaic system sizes offers the possibility of deploying a combination of smaller and larger urban photovoltaic installations. Furthermore, the decentralized photovoltaic rooftops can compensate for between 66 and 199% of the estimated annual consumption of 31 GWh in 2031. The method is highly transferrable and limited solely by the availability of sources of geospatial data and coordination with stakeholders. The investigation meets the needs of the Brazilian Ministry of Mines and Energy, therefore meeting the environmental needs of the energy sector by promoting renewable energy for the island which is a UNESCO Natural World Heritage Site and Brazilian National Marine Park and Environmental Protected Area. The investigation demonstrated that creating photovoltaic potential scenarios that nurture informed decision-making processes is a crucial initial step in urban renewable energy planning. The pioneering 2000-ha unmanned aerial photogrammetric survey proved to be a cost-efficient method for producing accurate data for modeling the irradiation and photovoltaic potential in urban areas. The investigation fills the literature gap on modeling photovoltaic potential for remote islands by blending unmanned aerial vehicles and geospatial tools.

A trait‐based approach to marine island biogeography

AbstractAimThe Island Biogeography Theory (IBT) and its multiple extensions explain species diversity patterns in insular systems. However, how these theories can predict the functional diversity patterns in island systems remains challenging. Here, we evaluated the predictions of the IBT, the General Dynamic Theory of Oceanic Island Biogeography (GDM) and the Glacial‐sensitive model of Island Biogeography (GSM) considering the functional diversity of reef fishes on islands.LocationTropical oceanic islands.TaxonActinopterygii.MethodWe combined literature data and online repositories to gather occurrence data and traits of reef fish species for 72 tropical oceanic islands. We then calculated five functional diversity indices (functional richness ‘FRic’, functional evenness ‘FEve’, functional divergence ‘FDiv’, functional over‐redundancy ‘FOR’ and functional vulnerability ‘FVul’). We used generalized additive mixed models to explore relationships among species richness and functional indices. Furthermore, we built Bayesian models to evaluate relationships between the functional diversity indices and several island features (isolation from the nearest reef, past and present reef area, and geological age) and two metrics that reflect the potential influence of Quaternary climatic changes (isolation from Quaternary refugia) and historical contingency (isolation from biodiversity centres).ResultsWe observed higher levels of FRic, FDiv and FOR on the Indo‐Pacific islands, whereas FEve and FVul showed higher values on the Atlantic and Eastern Pacific islands. We identified positive relationships between FRic, FDiv and FOR with species richness but negative relationships with FEve and FVul. We found that past and present reef areas best explained the variation in functional diversity among islands.Main ConclusionsThe functional diversity of reef fishes on oceanic islands showed a longitudinal gradient, which can be explained by differences in the evolutionary history among marine regions. Furthermore, past and present reef areas were found to be the best predictors of reef fish functional diversity on oceanic islands, extending the IBT, GDM and GSM for marine organisms within a trait‐based framework.

Isotopic niche partitioning of co-occurring large marine vertebrates around an Indian ocean tropical oceanic island

Tropical oceans host a high diversity of species, including large marine consumers. In these oligotrophic ecosystems, oceanic islands often favour the aggregation of species and biomass as they provide feeding opportunities related to the mechanisms of island mass effect. As such, the waters surrounding La Reunion (Southwest Indian Ocean) host seabirds, large pelagic teleosts, elasmobranchs, delphinids and sea turtles. Isotopic niche partitioning and comparison of trophic levels among these species (n = 21) were investigated using stable carbon (δ13C) and nitrogen (δ15N) isotope analysis. Overall, δ13C values were highly variable among taxa, indicating that the species exploit multiple foraging habitats along a coast-open ocean gradient. Overlap in δ15N values was limited, except for teleost species, the two species of sea turtles and two species of delphinids, the Indo-pacific bottlenose dolphin (Tursiops aduncus) and the Spinner dolphin (Stellena longirostris). Stable isotope analyses of samples collected over a 9-years period on different tissues with different integration times provide a consistent picture of the structure of the community of large marine vertebrates species around La Reunion and highlight the underlying mechanisms to limit the competition between species. The wide range of isotopic values confirms that large marine vertebrates have different trophic roles in coastal marine food webs around this oceanic island, which limits their potential of competitive interactions for resources.

Utopian and insular spaces in Chinese literature: An island approach

In response to the relative lack of scholarly attention paid to the relationship between island utopia and Chinese literature, this paper studies the imagination of both island and insular geographies in Chinese ‘utopian’ literature using an island-sensitive approach. Employing an expanded and constructive conception of the island, the paper examines the heterogeneity of Chinese island and insular imaginaries in literary works from diverse historical periods, especially in relation to the dominant western model of the remote tropical oceanic island. Based on the finding that the alterity of Chinese island and insular imagination lies as much in its depiction of spatial ambiguities as in its mixing of diverse figures, I reflect further on the benefits and perils of adopting a west-inflected island approach in examining the imaginary landscapes of utopianism and insularity in Chinese literature. It is argued that Chinese island literature is more a reading effect enabled by an imported theoretical approach than any inherent tradition in itself. In the end, two paths for innovating island aesthetics and epistemologies in cross-cultural contexts are proposed.

Tree recruitment after native frugivore extinction? A field experiment to test the impact of fruit flesh persistence in a tropical oceanic island

AbstractThe loss of large frugivores leads to seed dispersal loss and regeneration failure of numerous large-seeded trees near mother trees. Although Janzen–Connell effects are considered as the primary underlying cause, other factors remain understudied. Here, we used a field experiment to test the impact of flesh persistence on the recruitment of two large-seeded Sapotaceae species that lost their dispersers. In the rainforest of Mare Longue (Réunion), we sowed 3840 seeds in a four-factor design: seed treatment (seed cleaning; flesh persistence), canopy closure (understory; gap), year of sowing (01/2018; 11/2019) and species (Labourdonnaisia calophylloides, Mimusops balata). We also used camera traps to evaluate the impact of extant vertebrates. Seed treatment was by far the most influential factor: flesh persistence led to seedling recruitment divided by 3,2 on average, mainly due to failure of germination or seedling emergence. There were also significant variations in recruitment between species, years and canopy closure levels, notably due to the behaviour of the invasive fauna, especially giant snails that could unexpectedly restore recruitment by feeding on fruit flesh. Together, our results demonstrate strongly depleted recruitment due to flesh persistence and the importance of field experiments to understand the processes at work in complex ecosystems with novel plant–animal interactions.

PREDATION OF Velella velella BY THE SOOTY TERN Onychoprion fuscatus IN A POPULATION FROM TRINDADE ISLAND, BRAZIL

The species Onychoprion fuscatus or Sooty Tern, as it is popularly known, é is considered a marine Bird of pelagic habits, once its breeding areas are restricted to tropical oceanic islands and, according to the scientific literature, the species’ diet is mainly composed by fish and cephalopods. In general, studies reporting the ingestion of cnidarians by seabirds are relatively scarce in the literature, especially regarding reports with determination at the species level. Therefore, here we report the ingestion and regurgitation of Velella velella by O. fuscatus in a breeding colony from Trindade Island, Brazil. Field activities were carried out in October 2017. Apparently, the last report in the literature concerning the predation of V. velella by O. fuscatus was in 1983, by Harrison et al., and corroborates that V. velella contributes to the species’ diet, whilst for Trindade Island ours seems to be the first record.

Conservation paleobiology on Minami-Daito Island, Okinawa, Japan: anthropogenic extinction of cave-dwelling bats on a tropical oceanic island.

BackgroundWith strong environmental and geographic filtration, vertebrates incapable of flying and swimming are often extirpated from island ecosystems. Minami-Daito Island is an oceanic island in Okinawa, Japan that harbors the Daito flying fox (Pteropus dasymallus daitoensis), a subspecies of the fruit bat and the only extant mammal endemic to the island. However, the skeleton of a cave-dwelling bat Rhinolophus sp. and fossil guano were briefly reported in a previous study.MethodsHere, we present evidence for the anthropogenic extirpation of two species of cave-dwelling bats (Miniopterus sp. & Rhinolophus sp.) from Minami-Daito Island. Our goal is to reliably constrain the ages of the extirpated bat species by a multiproxy approach. Because skeletal materials did not preserve sufficient bone collagen for direct radiocarbon dating, we alternatively examined guano-like deposits based on SEM observation and Fourier-transform infrared spectroscopy (FTIR) along with stable carbon and nitrogen isotope analyses for possible indirect dating. We also examined stable carbon isotopes in bone apatite, assuming that an isotopic signal of C4 plants on the bat bones links to sugarcane plantation on the island based on the historical knowledge that early human settlers quickly replaced the island’s native C3 forests with sugarcane (C4 perennial grass) plantation from 1900 onward.ResultsOur cave survey documents the remains of Miniopterus sp. from the island for the first time. Based on the unique taphonomic conditions (unpermineralized bones, disarticulated skeletons closely scattered without sediment cover, various degrees of calcite crystal growth around bones) and a radiocarbon age of a humic sample, we suggest that the maximum age constraint of Miniopterus sp. and Rhinolophus sp. is 4,640 calBP. Based on a series of analyses, we conclude that the guano-like deposits are composed not of bat guano but mainly of humic substances; however, a hydroxyapatite crust associated with bat-lying stalagmites may be derived from bat feces. Stable carbon isotope analysis of bone apatite revealed C4 signals in various degrees, confirming that small populations of cave-dwelling bats persisted on Minami-Daito Island after 1900.ConclusionsThe results of this study indicate that these populations remained rather small and did not leave many generations and that the estimated ages can be bracketed from 4,640 calBP to the post-1900 (perhaps, until the 1950s). They likely faced a continuously high mortality risk due to severe anthropogenic stresses on the island, where most of the forests were turned into sugarcane plantations within a few decades in the early 20th century. A result of hearing surveys to local residents suggests the latest remnants most likely disappeared on the island concurrently with the introduction of chemical pesticides after World War II.

Indonesian coral reef habitats reveal exceptionally high species richness and biodiversity of diatom assemblages

We present the results of the first ever research on biodiversity and biogeography of marine benthic diatoms from coral reefs of the tropical islands of Indonesia, including West Borneo, East Java, South Celebes, Komodo, Rinca and Flores. The sampled islands offer a broad range of coral reef microhabitats and host diatom assemblages from seaweeds, sea grass, dead corals, scrapes from other biological surfaces, sand, rocks and other solid surfaces. The results of this study are based on the light (LM) and scanning electron microscopy (SEM) identification of diatoms only. Our taxonomic analysis revealed the presence of 911 diatom taxa representing 188 genera. Biodiversity indices such as Shannon, Simpson and Evenness as well as species richness and diatom relative abundance were calculated for each sample examined. We find that these indices were higher for Indonesia than those published for tropical oceanic islands or regions from both hemispheres, e.g. Galapagos and Martinique, but comparable to Madagascar. The non-metric multidimensional analysis showed that the type of habitat from which a particular sample was taken was of greater significance in the taxonomic composition than the geographical aspect. In terms of biogeography, cosmopolitan taxa were dominant in terms of relative abundance, but species richness was higher within tropical zonal and local forms. Many taxa were identified only at the genus level, and may turn out to be new to science.

Differing severity of frugivore loss contrasts the fate of native forests on the land of the Dodo (Mascarene archipelago)

Frugivore loss has the potential to alter the regeneration of tropical hyperdiverse forests. However, no study has investigated tree diversity maintenance within old-growth protected forests on tropical oceanic islands where conservation stakes are considerable. In the Mascarenes, the largest frugivores including the Dodo went extinct after human colonization in the 17th century. Mauritius, today devoid of almost all its native habitats, retains an important population of flying foxes, while Réunion, largely covered by native habitats, has lost all but one of its native frugivores, a bulbul. Using census data of 130 woody species from 3-ha permanent plots from Mauritius (MAU-BF) and Réunion (REU-ML), we show that most fleshy-fruited species regenerate well at MAU-BF, in contrast to REU-ML, although large-seeded fleshy-fruited species regenerate poorly at both sites. The difference in recruitment is all the more striking because local woody plant diversity at MAU-BF is double that at REU-ML. Changes observed in the understory will probably lead to a strongly impoverished canopy at REU-ML, and to canopy shift composition at MAU-BF. Hence, the protected but highly fragmented forests on Mauritius are likely more resilient than those on Réunion usually considered best preserved within the ecoregion. Although processes other than seed dispersal might also be at work, flying foxes probably ensure effective dispersal of numerous native fleshy-fruited plants on Mauritius, contrary to only bulbuls on Réunion. To efficiently protect tropical rainforests on islands and continents alike, there is an urgent need to protect extant frugivores populations and reinstate seed dispersal function wherever necessary.

Effectiveness and outcomes of invasive species removal in Hawaiian streams

Despite aquatic invasive species (AIS) being a widely recognized threat to native biodiversity in streams on subtropical and tropical oceanic islands across the Pacific, AIS management has been constrained by concerns that methods of removal could result in more harm than good. In this study, we assessed the effectiveness and outcomes of combining hand-netting and streamside sequestration of native species with AIS removal via three-pass electrofishing tailored for Hawaiian Island watersheds. Removals were conducted in 13 watersheds on the island of O‘ahu following a before-after, control-impact design to assess how AIS removal and post-removal community reassembly varied by surface flow and target species of interest. We found that removals resulted in a sharp reduction in AIS densities without altering native species densities. Removal efficacy was greatest in streams with intermediate mean discharge irrespective of target group or pre-removal AIS densities. Long-term monitoring demonstrated that removals led to persistent shifts in community composition reflecting sustained reductions in AIS densities. These findings indicate that electrofishing can be a valuable tool for AIS management in Hawaiian and other subtropical Pacific island streams, so long as steps are taken to minimize potential harm to at-risk and culturally important native species.

New records of the mollusk Firoloida desmarestia Lesueur, 1817 (Gastropoda: Pterotracheidae) off Fernando de Noronha Archipelago and Northeastern Brazilian continental slope, Tropical Atlantic

Biogeographic and taxonomic knowledge on planktonic mollusks, specifically on Pterotracheoidea (also known as heteropods or sea elephants) in tropical oceans, is still incomplete. In this paper we report the first record of the heteropod Firoloida desmarestia Lesueur (1817) on waters off the Northeast Brazilian continental slope and Fernando de Noronha Archipelago and extend its geographic distribution in the tropical Atlantic. We provide new detailed digital image and descriptions of this highly fragile and transparent gelatinous species. Samples were taken in the context of the ‘ABRACOS’ (Acoustic along the Brazilian Coast) project using bongo nets. Out of 96 samples analyzed, six specimens were recorded in five samples, three at Fernando de Noronha, and three off the Northeast Brazilian coast. The present study extends the range of distribution of F. desmarestia to 3°S-9°Sin the western the Tropical Atlantic and highlights the importance of detailed studies on large-sized gelatinous plankton biodiversity in tropical oceans. Keywords: Tropical oceanic islands, Continental slope, zooplankton, heteropods, Pterotracheidae.

Temporal and spatial variability of shallow soil moisture across four planar hillslopes on a tropical ocean island, San Cristóbal, Galápagos

Study regionThis paper provides a summary of findings from temporal and spatial studies of soil water content on planar hillslopes across the equatorial island of San Cristóbal, Galápagos (Ecuador). Study focusSoil water content (SWC) was measured to generate temporal and spatial records to determine seasonal variation and to investigate how the behavior of surface and near-surface root-zone soil water may support island-wide hydrogeology models. SWC probes were installed at four weather stations in a climosequence to generate a temporal record, and spatial surveys of shallow SWC across the selected sites were completed during wet and dry seasons. Temporal differences in SWC were driven by seasonal variations in rainfall and evapotranspiration, while spatial variability remained high during both wet and dry seasons. Unsaturated hydraulic conductivity determined by mini-disk infiltrometers was highly variable across the slopes, as were other hydrologic variables. New hydrological insights for the regionThe high heterogeneity of soil water and hydrologic characteristics provides a means to explain why little runoff is observed at the study sites: soils do not saturate uniformly across hillslopes, allowing for runoff generated in one part of the hillslope to be conducted into the soil in adjacent parts of the hillslope. The lack of connected surface runoff helps explain how water enters the groundwater system of the island.

Trends in recreational fisheries and reef fish community structure indicate decline in target species population in an isolated tropical oceanic island

Marine recreational fisheries and fish communities have been mostly studied separately, severely hampering the detection of possible interactions. Here we monitored recreational fishery landings (angling and spearfishing) and assessed the reef fish community through underwater visual censuses in Trindade, an isolated oceanic island in the southwestern Atlantic Ocean. The study was conducted in zones of high and low fishing effort, along three different years spread over a seven-year period. We found high catch per unit effort (CPUE; kg*fisher−1*hour−1) associated with high fishing intensity. However, the biomass of the targeted species in the natural environment decreased by 58% over time, while fishing effort increased about 270%, and CPUE decreased by 40%. Inverse relationships between effort and CPUE, and effort and biomass in the environment, were stronger in zones of high fishing effort. We conclude that the recreational fishery activity quickly responded to overfishing, creating a harvesting process that negatively impacted reef fish communities in this isolated oceanic island. Thus, conservation strategies should incorporate long-term recreational catch and fish community monitoring programs. Here we discuss options for the sustainability of the recreational fisheries and reinforce the importance of dialogue among scientists, managers and users for the achievement of conservation goals.

Axiidean ghost shrimps (Decapoda: Axiidae, Callianassidae, Callichiridae, Micheleidae) of the Trindade and Martin Vaz Archipelago, Vitória-Trindade Seamounts Chain and Abrolhos, off southeastern Brazil.

The Trindade and Martin Vaz (TMV) volcanic archipelago is highly isolated, being located some 1200 km off the Brazilian coast and about 4200 km away from the nearest African coast. The only axiidean known from the archipelago is Coralaxius nodulosus (Meinert, 1877), a species extensively reported in the western Atlantic. From 2012 to 2018, 263 SCUBA diving and intertidal samplings were conducted at TMV and yielded 46 axiidean specimens in three species, one of which is a new species: Corallianassa longiventris (A. Milne-Edwards, 1870), Neocallichirus grandimana (Gibbes, 1850), and Fragillianassa joeli sp. nov., a species closely related to F. fragilis (Biffar, 1970). Hitherto unreported specimens from along the Vitória-Trindade Seamounts Chain (VTSC) and the Abrolhos Bank were also included in this report, namely C. nodulosus and Michelea vandoverae (Gore, 1987). The occurrence of M. vandoverae at the Abrolhos Bank extends its range into the southwestern Atlantic. Coralaxius abelei Kensley Gore, 1981 is herein considered a junior synonym of Coralaxius nodulosus (Meinert, 1877). Meinertaxius Sakai, 2011, therefore becomes a subjective synonym of Coralaxius Kensley Gore, 1981. Axiideans from the tropical southern-central Atlantic oceanic islands (Ascension, Fernando de Noronha, Rocas Atoll, Saint Helena, Trindade and Martin Vaz) are listed with their gross distribution in the Atlantic Ocean revealing a strongly depauperate axiidean insular fauna, totaling six species. Except for Axiopsis serratifrons (A. Milne-Edwards, 1873), a pantropical species, the insular southwestern-central Atlantic axiideans are entirely of western Atlantic affinities, with F. joeli sp. nov. being the only endemic so far.