ME146 Sea turtle nest site preferences and hatchling sex ratios
There are seven species of sea turtle in the world, all of which are either threatened or endangered. The beaches of Akumal (meaning “home of the turtles”) are the nesting ground for two of these species: the loggerhead turtle (Caretta caretta) and the green turtle (Chelonia mydas). One of the major aims of the ongoing turtle conservation project is to ensure that the turtles have access to suitable nesting sites on the beaches. In order to do so, it is necessary to understand the nesting site preferences of the green and loggerhead turtles and to ascertain the nest characteristics associated with successful incubation. Investigation of turtle nesting will record the number and location of green and loggerhead turtle nests, noting their distance from the shore, habitat characteristics, their depth, temperature inside the nest, number of eggs laid and number of successful hatchlings. As turtles are reptiles, the temperature inside the nest during the incubation period determines the sex ratio of hatchlings. Males are produced at lower temperatures than females and with beach temperatures on the rise due to climate change, there is major concern that sex ratios are highly female-skewed. It is not possible to determine the sex of hatchlings without dissection, but sex ratios can be inferred from mean nest temperature recorded on HOBO data loggers inserted into the nest during nesting. Variation in likely sex ratios can then be linked to nest site characteristics to determine areas of the beach that are able to produce males. In addition, the sheer number of turtles attempting to nest in the Akumal area results in turtles digging up existing nests on the beach due to a lack of space to make new nests. For this reason, it is necessary to relocate some of the nests into beach hatcheries and thus ensure careful management of the density of nests in the hatchery and the amount of shade they receive to maintain correct nest temperatures to produce balanced sex ratios of hatchlings.
ME147 Effect of tourism on immature green turtle behaviour in Akumal Bay
Year-round you can find immature green turtles (Chelonia mydas) feeding on the seagrasses in Akumal Bay. These turtles have become a popular tourist attraction and there is concern that both the number of tourists and the behaviour of tourists is affecting the behaviour and welfare of the turtles. Multiple studies of “swim with wild dolphin” based tourism has indicated that when the number of tourists gets too high, or the tourists attempt to touch them, the dolphins issue evasive responses to attempt to escape from the tourist and, if the tourism continues to maintain high numbers, the dolphins simply move their home range to areas inaccessible by tour boats. As the availability of healthy seagrasses in the Mexican Caribbean coastline is limited, the turtles in Akumal Bay may not have the option of leaving the area to avoid large numbers of tourists so the snorkel with turtle tours need to be strictly regulated. As Akumal Bay has just been declared a protected area, data is urgently required to determine the carrying capacity of snorkel based tourism. Research into green turtle behaviour will involve snorkelling with the turtles throughout the day to record their activity budgets and rates of evasive responses to tourists using focal animal sampling with continuous recording. Each turtle can be recognized individually and at the start of each focal sample the turtle will be photographed from various angles for subsequent identification from the turtle photo ID database. The number of tourists within a 5m radius of each turtle and the behaviour of these tourists (whether they abide by the rules and maintain a safe distance from the turtles or attempt to interact with them) will be recorded throughout each focal sample to determine the effect of tourism on turtle behaviour.
ME148 Immature green turtle foraging behaviour and seagrass abundance in Akumal Bay
There are three species of seagrass present in Akumal Bay: Thallassia testudinum, Siryngodium filiforme and Halodule wrightii. Ongoing monitoring of the foraging behaviour of the turtles has indicated a clear feeding preference for T. testudinum and unsurprisingly, ongoing monitoring of the seagrasses has indicated a decline in the abundance of T. testudinum. Immature green turtles naturally form large foraging groups and once a food patch has been depleted they move to a new area. However, limited availability of seagrasses in the Akumal area means that this may not be possible for the turtles in Akumal Bay and thus steps must be taken to sustainably manage the seagrasses. S. filiforme and H. wrightii seagrass remain abundant in Akumal Bay, but as turtle foraging on these grasses has been limited, the grasses lack digestible young shoots. Investigation into the state of the seagrasses and feeding behaviour of the turtles is therefore necessary to determine whether active management of the seagrasses (e.g. trimming the S. filiforme and H. wrightii to encourage new shoots to grow) is required to maintain a viable food supply for the turtles. Moreover, existing data shows that snorkel based tourism influences the movement patterns and foraging behaviour of the turtles resulting in heavy grazing of tourist-free areas and avoidance of seagrasses in areas where snorkel tours are prevalent. As Akumal Bay is now a protected area there is the option of re-zoning the bay to ensure that snorkel tours do not prevent turtles from accessing important areas of seagrasses, but data relating to seagrass coverage and turtle foraging behaviour is required to determine the specific location of tourist-free areas. Research into green turtle behaviour will involve snorkelling with the turtles throughout the day to record their foraging patterns. Seagrass quadrats surveys will be used to determine the availability of the various species of seagrasses, which can then be compared to turtle feeding preferences obtained from behavioural observations.
ME149 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. seagrass beds and coral reefs. Yet, as much as 1 – 2% of the global mangrove forests are lost per year. Mangroves draw down 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 seagrass and coral reef ecosystems. If the ecosystem services that mangroves 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.
ME150 Understanding the non-conventional cenotemangrove forest system
The Yucatan Peninsula is formed of limestone karst substrate that was once coral reef. As limestone is porous, rainwater seeps through the rock surface to form an extensive network of underground rivers accessed from the surface by sink holes, known locally as cenotes. Mangrove forests associated with cenotes in coastal regions are not new, but research of them is. This novel project aims to investigate the driving forces behind the structure and function of these unusual mangrove ecosystems and to investigate differences of animal community structure in comparison with coastal mangrove forests. The majority of mangrove animals exploit the available hard substrata within mangrove ecosystems. Areas such as mangrove prop roots and in particular large wood detritus (LWD) are favourable for most mangrove fauna, but nothing is known about the organisms that process the fixed carbon in cenote mangrove forests. Projects may highlight new and unreported information from forest structure and function, to mangrove fauna diversity and niche separation. Continuous belt transects and plots will be used to establish the tree structure, composition and basal areas with the cenote mangrove forests. Biodiversity assessments of the fauna upon mangrove roots, substratum and LWD will be made, and animal observations will be employed. Degradation processes of LWD will be recorded in the forests and compared with those from conventional mangrove forests.
ME151 The conservation of and improvement of Caribbean coral reefs: Reef restoration through plantation of Acropora cervicornis
Acropora is one of the most important Caribbean corals in terms of its contribution to reef growth and fishery habitat. Acroporid species are the Caribbean’s fastest growing reef-building corals. Since the 1970s, Caribbean acroporid populations have been decimated by disease outbreak. Their recovery has been impaired by the general poor health of Caribbean coastal ecosystems. In Akumal this decline is estimated at >90%, although it is unlikely that this truly represents the loss of coral due to the lack of reliable data. Coral restoration is increasingly considered to be a viable recovery plan. In Akumal preliminary research has been conducted to trial success rates of coral nurseries where Acropora cervicornis is grown, propagated and then transplanted onto the reef. The methods used are minimally invasive and require cheap materials. The trials have proved to be successful, with doubling of live tissue from dying rescued fragments within one year, combined with successful fusion and growth of transplanted colonies onto the reef. In order to measure the impact of coral restoration work, it is essential to develop baseline data from which to measure the successful colonies that have grown as a result of the restoration work. Using continuous belt transects on the reef, the mapping of acroporid colonies will be conducted to assess the distribution, abundance and surface area of the colonies. Coral frags will be out-planted at various distances from the mother colony to measure successful recruitment and growth at different sites from that of the mother colony. Reef fish assemblages, particularly juveniles, will be assessed on reefs with none or few acroporid colonies. Established acroporid frags will then be planted onto those reefs and re-assessed. These data will be compared to reefs with a high density of acroprids.