Environmental science topics

Country codes: HO (Honduras), IN (Indonesia), MA (Madagascar), ME (Mexico), PE (Peru), SA (South Africa)

HO08 Prevalence of chytrid in amphibian populations within Cusuco

The effective conservation of Cusuco National Park is imperative for many endemic species, none more so than cloud forest amphibians. The spread of chytrid fungus has caused severe declines in many amphibian populations and is a major concern for global amphibian conservation. Chytrid is known to have been present within the amphibian populations of Cusuco for at least 15 years, but its prevalence within specific areas of the forest and the extent to which different species are affected are not well known. Amphibian species will be encountered during diurnal and nocturnal transects and swabbed for chytrid. Swabs will be taken back to the lab at base camp and tested for the presence of chytrid using polymerase chain reaction (PCR) and visualised using agarose gel electrophoresis. Individuals will also be assessed for visual signs of infection. Prevalence of chytrid will be mapped in the park using multiple years’ data to assess whether the disease is continuing to spread to previously uninfected areas to contribute to the investigation into the underlying mechanism of infectivity.

Extended Project Summary

HO10 Factors affecting bird communities in the cloud forests of Cusuco

Birds are excellent indicators of forest ecosystem health as their abundance and diversity are closely related to habitat disturbance and they make ideal models because they are relatively easy to monitor and study. This topic takes advantage of the existing fixed point count survey work being undertaken for birds at over 130 survey sites across Cusuco, as well as the recently started mark-release-recapture mist netting survey data. By examining species distributions and species richness across varying habitats, projects could: compare bird communities in different administrative divisions of the park (e.g. the buffer/core zones that differ in degrees of wildlife preservation and human activity); study the impact of differing disturbance levels on bird communities; investigate the impact of habitat type on bird community composition; or look at the effect of altitude on bird composition. By using covariates such as temperature, habitat structure and forest type, threshold limits for the different species could be elucidated which may have interesting implications for the impact of habitat alteration (e.g. by deforestation) in the future.

Extended Project Summary

HO11 Variation in cloud forest small mammal populations and their microhabitats, Honduras

A total of 19 small mammal species have been recorded in Cusuco National Park comprising a complex community. However, three focal species are of interest and dominate the community: 1) Desmarest’s spiny pocket mouse (Heteromys desmarestianus) which occurs on the forest floor >150m from the nearest river (terrestrial environment), 2) the Mexican deer mouse (Peromyscus mexicanus) which occurs along river corridors <3m from the water’s edge (riparian environment), and 3) a currently unidentified Rheomys spp. watermouse which is entirely aquatic and forages by diving within upland rocky streams (riverine environment). Therefore, three traplines are set at each of seven camps throughout the park, each consisting of 12 traps placed approx. 10m apart. These traplines are set up in each microhabitat targeting each of the three small mammal species for comparative and individual study. How these species share the forest and the individual specialism of each species remains largely unknown. Small mammal abundance and species composition can be related to habitat data collected from permanent plots along the transect network (for example forest structure, tree density, % fruiting, leaf litter depth etc.). Additionally, abundance and special distribution patterns may be related to predator abundance and distribution (mainly large snake species including Wilson’s pit viper, Cerrophidion wilsoni), building up a picture of the trophic relationships in the region.

Extended Project Summary

HO14 Tracking the recovery of a keystone urchin species and its role in reef restoration

Under natural conditions, the sea urchin (Diadema antillarum) is the most important herbivore on Caribbean coral reefs, and is therefore considered a keystone species. However, a disease in the 1980s caused the death of an estimated 98% of individuals throughout the region. This mass mortality event had a devastating effect on reef health, driving subsequent phase shifts to algal dominated benthic communities. Recovery has been extremely limited, with populations on most reefs still severely depleted, and Utila Island is a classic example of this. Remarkably, the Banco Capiro reef system in Tela Bay has a population density of D. antillarum at astonishingly high levels. It also boasts extremely high benthic reef health, despite historical overfishing leading to a complete collapse of the fishery. Since its recent discovery, Operation Wallacea scientists began detailed population studies in 2013 and this project will continue to build on this. The primary objective is to quantify changes in the abundance, biomass and population structure of D. antillarum on the reefs of Utila and Banco Capiro. Further data will assess the potential roles of competition, predation and environmental factors in driving the recovery on Banco Capiro.

Extended Project Summary

HO15 Managing the Caribbean lionfish invasion

Lionfish are an invasive species in the Caribbean and are having a devastating impact on local fish communities throughout the region. Introduced in the 1980s, believed to be by accident, lionfish have spread extremely quickly and are now found as far as New York City and Brazil. Their success is down to a number of factors, including their high reproductive rate, generalism in terms of both diet and habitat, and a lack of natural predators. They are now considered to be one of the greatest threats to the future of Caribbean coral reefs and their fish communities. Management approaches to dealing with the lionfish invasion are limited, with one of the most common being direct removal via spear fishing. This relies on regular visitation to individual reef sites, as studies have shown full recovery of lionfish populations only five months after complete removal. Baseline data will be collected on population densities of lionfish at sites of varying intensities of culling. Lionfish will subsequently be removed and morphometric measurements taken along with dissections for physiological and gut content assessments, which can link fish assessments to gauge prey availability. In addition, lionfish behavioural responses to divers, such as Flight Initiation Distance (FID) and Alert Distance (AD) can be assessed, which could also be expanded to include commercially valuable fish such as grouper.

Extended Project Summary

IN31 Evaluating potential effects of rising environmental temperatures on thermal ecology of fiddler crabs, Uca spp.

Often exhibiting high levels of biodiversity and endemism, mangrove forests demonstrate a remarkable interdependence between local flora and fauna such that a loss of diversity or density in one group has marked adverse effects on the other. Declines in burrowing crustacean populations, for example, have been shown to result in reduced organic turnover, decreased nutrient and energy cycling, and diminished primary productivity in mangrove species. Fiddler crabs (Uca species) are one of several semi-terrestrial, burrowing, mangrove decapods making up a keystone group commonly referred to as engineers. Indonesia boasts the highest diversity of fiddler crab species of any country in the world with 14 total species, seven of which can be found within an area of 4-square meters within the Ambeua Mangrove near Hoga Island. Previous research at the Hoga Marine Laboratory has shown that local fiddler crab populations are relatively tolerant of high temperatures; however, with environmental temperatures across the Malay Archipelago expected to increase by up to 4°C in coming decades, it is unclear how fiddler crab populations and ultimately mangrove ecosystems, may be affected. Potential dissertation projects could evaluate differences in thermal adaptations of Uca spp. occupying different intertidal regions, or may look at acclimation responses of a single Uca species. All studies would include a field observation component, though most of the empirical work would take place in the Hoga Island Research Laboratory. Students are strongly encouraged to contact their project field supervisor early in the proposal development process.

Extended Project Summary

IN34 Role of mangroves in marine ecosystems

The mangroves and associated seagrass beds around the island of Kaledupa and Hoga provide an excellent laboratory to study some of the effects of mangroves on the marine environment. Some of the mangroves suffer from harvesting and one project could look at the effects of this harvesting on the mangrove biota (both infauna diversity – species that bore) and epiphytes in mangroves with different levels of exploitation. Another project could compare the effectiveness of mangroves that have been partially damaged from harvesting with more pristine areas in depositing sediment from the water column. Note this study could be extended to the adjacent seagrass areas and coral to assess their impact on sediment settlement. Another project could look at the processes which affect carbon release from mangroves. Different guilds of biodegrading organisms (e.g. bracket fungi, beetle larvae, termites and shipworms) process wood but their relative contribution to this process varies according to the length of time the woody detritus is submerged on a tidal cycle and the salinity levels. This could be examined by studying the biodegrading organisms on mangrove wood detritus at different distances form the strandline.

ME54 A comparison of pristine and degraded mangroves in Akumal and the impact of mangrove degradation on adjacent seagrasses and coral reefs

Mangrove forests are highly productive marine ecosystems that are essential for the health of adjacent ecosystems e.g. sea grass beds and coral reefs. Yet, as much as 1-2% of the global mangrove forests are lost per year. Mangroves drawdown atmospheric CO², sequester and trap fine sediments, facilitate vital biodiversity mechanisms (e.g. fish nurseries) and improve fishery productivity. Despite the obvious importance of mangroves, mangrove forests in the Yucatan Peninsula have been under considerable anthropogenic impact from harvesting, causing a reduction in important habitat and biodiversity, carbon sequestration, and the productivity of adjacent sea grass and coral reef ecosystems. If the ecosystem services that mangrove provide can be quantified, then there is scope to develop a mangrove equivalent of the REDD programme in which fishing communities could receive economic investment in exchange for continued protection of the mangroves. Projects could therefore focus on a comparison of the structure, function, and faunal diversity of pristine and degraded mangroves, or an investigation of wood degradation processes across mangroves of differing quality. In addition, projects could investigate health and diversity of seagrasses and coral reefs in relation to the level of degradation of adjacent mangroves. Belt transects and permanent plots will be used to record tree composition, basal areas and tree densities. Biodiversity assessments will be conducted by investigation of the available mangrove substrata. Snorkel and dive based transect and quadrat surveys may be used to assess diversity and coverage of seagrasses, hard corals and algae.

Extended Project Summary

PE58 Tropical butterfly diversity and environmental gradients

The forest of the Pacaya-Samiria Reserve is awash with a diversity of bright and colourful butterflies and moths (Lepidoptera), notably including species of the beautiful blue morpho. Lepidoptera make excellent indicators of environmental change due to their variety of life-history strategies and their rapid life cycles. The Lepidoptera of the Pacaya-Samiria are monitored using baited catch-and release traps containing fermenting fruit, sugar water or salt water, each attracting a different suite of species. This allows a number of research questions to be examined. Projects could investigate the niche-partitioning of butterflies and moths according to food source and food availability within forest types; alternatively the diversity and community composition changes along the natural environmental gradients from forest edge to centre could be studied; temporal niche-partitioning between butterflies and moths and whether the response to forest edges differs between day and night is also of interest; additionally, there is an opportunity to study the vertical stratification of the Lepidoptera community between the understorey and the mid-canopy. Permission is not granted to collect specimens, but as a diverse and abundant study group, the Lepidoptera project can be tailored to address any number of environmental questions, whilst also contributing to the long-term climate change data set.

Extended Project Summary