My #ExeterMarine PhD: Marine Turtles of the Bijagós, Guinea-Bissau

Author: Dr Rita Patricio. Rita is now a postdoc jointly between MARE – Marine and Environmental Science Centre – ISPA, Portugal and the University of Exeter, in the project ‘Consolidation of Marine Turtle Conservation in Guinea-Bissau’, funded by the MAVA foundation.

 

 

For my PhD in Exeter I conducted fieldwork at the Bijagós Archipelago, Guinea-Bissau, where I had the chance to study one of the most impressive sea turtle populations in the world under the supervision of Prof Annette Broderick, Prof Brendan Godley and Dr Paulo Catry  from MARE – ISPA, Portugal. I finished my PhD at the University in 2017, and I continue to work in this amazing site as post-doctoral fellow. My work in Guinea-Bissau is very rewarding because it is rooted in participation with local communities, and in strong collaboration with the national authorities for biodiversity conservation (Institute for Biodiversity and Protected Areas – IBAP). Our co-developed scientific outputs inform the management of marine turtles and their habitats.

Our team

The Bijagós Archipelago and Poilão Island

The Bijagós Archipelago, and Poilão Island (encircled)

Located offshore Guinea-Bissau (West Africa), the Bijagós Archipelago is a sanctuary for iconic fauna, such as marine turtles, manatees, hippopotamus, and several species of migratory sea birds and waders. This biodiversity led to the designation of the Bolama-Bijagós UNESCO Biosphere Reserve in 1996.

The beaches of the archipelago are used by four species of sea turtles for nesting: the green turtle Chelonia mydas, the olive ridley Lepidochelys olivacea, the hawksbill Eretmochelys imbricata and the leatherback Dermochelys coriacea, and important foraging grounds for green turtle juveniles have also been identified in the area.

 

Poilão: home of Africa’s largest green turtle rookery

A small island in the southernmost end of the Bijagós, Poilão Island (10°52’N, 15°43’W), with a beach extending for only 2 km, hosts the third largest green turtle rookery in the Atlantic, the largest in Africa, with an average of 27000 clutches laid per year (2013 – 2017).

 

 

 

Our findings

Green turtle hatchling begining its first large-scale migration.

Through my PhD research, we have learnt a great deal about the major green turtle rookery in Poilão and hopefully contributed towards raising awareness as to its importance.

Using genetic analysis, we estimated that the connectivity of Poilão goes well beyond the African continent, with some juveniles dispersing across the Atlantic, reaching South American foraging grounds. This is a major undertaking for the small turtles and underlines the regional importance of this population.

Fieldwork was conducted with local community collaborators

During the nesting season I used temperature dataloggers to record the incubation conditions at the nesting beach, as this defines the sex of the hatchlings. If temperatures are above a certain limit only females are ‘born’, and extreme temperatures can cause embryo mass mortality; worrying attributes with the undergoing climate change. We found that the native forest at Poilão is key to keeping ‘healthy’ hatchling sex ratios and predicted that this rookery is likely the largest source of male green turtle hatchlings in the Southern Atlantic.

We also realized that there were different preferences in nesting habitats among nesting females in Poilão, but that they are very faithful to their nesting site, typically returning to the same habitat (i.e. either the exposed beach or the forested sand) and within less than 50 metres of their first nest! This is a really fine-scale philopatry, and turtles seem to maintain this fidelity across nesting seasons.

Female green turtle coming ashore to nest at Poilão

Another potential threat associated with climate change is sea-level-rise leading to increase flooding of the nesting beach. Using a drone coupled with a digital camera we collected aerial photos at Poilão and with photogrammetry analysis we created digital elevation models of the nesting beach, to estimate impacts of projected sea level rise. Taking current IPCC scenarios, as much as 33.4 to 43.0% of the current nesting habitat could be underwater by 2100.

Miguel Varela, PhD student at the University of Exeter, flying the drone at Poilão

Under future climate change scenarios, females nesting in the upper shaded areas of the beach should have higher fitness, because their nests will be more protected from the impacts of both extreme temperatures and sea-level-rise. Individual consistency in nesting microhabitat should provide opportunity for natural selection to occur.

Future research
For my post-doc I will be looking into the post-breeding migratory paths of nesting green turtles from Poilão, using satellite tracking devices. We will deploy these in August 2018, so soon we will have more information that will help us to assess the connectivity of this major population and the potential threats outside the nesting beach. I will also be monitoring a feeding ground for juvenile green turtles located in the most offshore islands of the Bijagós, Unhocomo and Unhocomozinho, and engaging the local communities in our research work.

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!

My #ExeterMarine PhD: Connectivity Between Marine Protected Areas

Author: Tom Jenkins (PhD Student) – Biosciences, Streatham Campus

 

Natural England Case Partner

I started my PhD study under the supervision of Dr Jamie Stevens at the University of Exeter in October 2014 on a NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP) studentship.  This programme was appealing to me because it encouraged collaborations among academic and non-academic partners to achieve mutual research objectives in environmental science. Natural England, the UK government’s advisor for protecting the natural environment in England, is the official non-academic partner linked with my PhD.  In our research group, the Molecular Ecology and Evolution Group (MEEG), we use a variety of molecular techniques to examine variations in the DNA of various aquatic and terrestrial species in an effort to answer questions about the population biology and ecology of these animals. Of particular interest to me is the application of such data to inform and address matters of marine conservation and management.

 

Marine connectivity

Study species: Pink sea fan

Connectivity is generally defined as the degree to which individuals/larvae/eggs are exchanged between populations, the study of which allows us to estimate dispersal distances and explore patterns of immigration between populations of a species. For some marine species, high connectivity can be extremely important for the persistence of isolated populations or for (re)colonising habitats that become available.  One of the aims of marine conservation is therefore to establish Marine Protected Areas (MPAs) of adequate size and spacing to help maintain natural connectivity by reducing human disturbance in key or vulnerable areas.

Study species: European lobster

My research

My PhD centres on assessing the connectivity of two bottom-dwelling marine invertebrates around UK and western European coasts, the pink sea fan (Eunicella verrucosa) and the European lobster (Homarus gammarus). To do this, I am using molecular markers to study patterns of population genetic structure across both species’ geographical ranges.  These data allow us to detect genetic similarities or differences between populations, which we can use as a proxy for indirectly estimating the amount of connectivity between discrete populations (i.e. ↑ similarity = ↑connectivity – but evolutionary processes other than connectivity can also influence the genetic structure of populations which can complicate interpretations of the data!).

Pink sea fan

The pink sea fan (Eunicella verrucosa) is a cold-water soft coral that is protected in the coastal waters of England and Wales by the UK government, and it is listed as Vulnerable on the IUCN Red List.  Because of its rarity across the UK, several Marine Conservation Zones (MCZs) have been specifically designated around southwest Britain with the protection of pink sea fan colonies in mind (e.g. The Manacles MCZ).  Our published research found that at distances of >500 km, pink sea fan colonies are likely to follow a stepping-stone model of connectivity, such that colonies which are closer together are more connected than those further apart.  In contrast, at distances <500 km, we found that populations were genetically quite similar, suggesting high connectivity between areas at this spatial scale.  For the colonies sampled across southwest Britain, high connectivity was apparent which suggests that the network of MPAs in southwest England and Wales appears to be sufficient for maintaining connectivity in this species! We think that this could be useful evidence to support the existing MCZs designated around southwest England and Wales.

Pink sea fan population genetic structure (Holland et al. 2017).  Strong genetic differences between populations from Portugal, Ireland and France/Britain suggests low connectivity at this spatial scale; low genetic differences within countries (i.e. within southwest Britain) suggests high connectivity between populations at this scale.

European lobster

European lobster fishing pot (image from the National Lobster Hatchery)

The European lobster (Homarus gammarus) is a crustacean typically found hiding in crevices on rocky substrates at depths from the low tide mark to 50-150 metres.  Their high market value means they are targeted by fishermen and therefore it is important that these fisheries are managed sustainably.

 

 

 

Sampling lobster pleopods at Looe Harbour, Cornwall

 

For this lobster study, I have been fortunate enough to collaborate with the National Lobster Hatchery (Padstow, Cornwall) and members of the public (e.g. local fishermen/shellfish merchants) which has massively helped me to collect tissue samples for genetic analysis across most of the range of European lobster (from the Mediterranean to the British Isles and Scandinavia).

European lobster sampling locations

 

 

 

 

 

 

 

At this stage, I have isolated variations in DNA sequences known as single nucleotide polymorphisms (SNPs) from across the genome – this panel of SNPs was recently published and will hopefully be a useful resource for future genetic studies of European lobster.  My ongoing work is using this SNP panel to explore the population genetic structure of European lobster across our sampling sites.  For me, it will be very interesting to find out what patterns of connectivity are present across these geographical areas and, moreover, the results may help the National Lobster Hatchery decide where they can release their Cornwall-bred juvenile lobsters without impacting the natural genetic make-up of the lobster population being restocked.

This blog accompanies a new paper in Marine Policy, read here.

 

Hatchery-reared juvenile lobster (image from the National Lobster Hatchery)

#ExeterMarine is a interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!

 

My #ExeterMarine PhD: Marine Turtles of Brazil

Author – Lili Colman (PhD Student) – Centre for Ecology and Conservation, Penryn Campus

From the moment I arrived at the University of Exeter to undertake my MSc in Conservation and Biodiversity, I quickly fell in love with the University, the Campus and Cornwall. Discovering all the cutting-edge research being carried out across the University of Exeter has been a definite highlight for me. The opportunity to participate in the Africa field course was one of the most amazing experiences of my life and one I will always cherish, having helped me build a practical understanding of large-scale conservation issues. My MSc research project centred on analysing 30 years of mark-and-recapture data from juvenile green turtles on an isolated tropical archipelago in Brazil, under the supervision of Prof Brendan GodleyThis published work contributes important insights regarding demographic parameters and population trends for this species.

Lili_Kenya
Meeting the Maasai in Kenya

 

Upon my return to Brazil, and whilst working as an environmental consultant there, I applied for a PhD at Exeter to work with TAMAR (the Brazilian Sea Turtle Conservation Programme). This on-going conservation project illustrates a powerful example of how marine turtles and coastal communities can co-exist in an ever-changing world. Despite a history of over-exploitation, the five different species of marine turtles that nest in Brazil are now fully protected by law. And as a result, recent years have shown very promising signs of population recovery. Perhaps most notably, a major part of this success can be attributed to the active involvement of the surrounding coastal communities in the conservation work. What once started in the direct employment of former egg poachers, now involves a wide range of activities to encourage environmental awareness in the area. This includes environmental campaigns, alongside the support of alternative, sustainable economic opportunities for the communities living near the nesting beaches.

Tamar

Local kids talking turtle in Bahia, Brazil (Banco de imagens Projeto TAMAR)

My PhD research focuses on the highly migratory leatherback sea turtle (Dermochelys coriacea). This species has its major nesting site deep in the southwestern Atlantic ocean in eastern Brazil, on the northern coast of Espirito Santo. Projeto TAMAR has been monitoring the area since 1983 and there are promising signs of population recovery for the species. However, with a small population size and restricted geographical distribution, alongside the emergence of new threats – coastal development, fisheries bycatch, climate change, marine and light pollution – the population continues to be of conservation concern.

(Henrique Filgueiras)
Lili records leatherback sea turtle nesting (Henrique Filgueiras)

As part of the Marine Turtle Research Group (MTRG) at the University of Exeter, we are using a variety of techniques to investigate this population’s ecology, trends and the main impacts they are facing. This research is being done in collaboration with TAMAR in Brazil and Ciência Sem Fronteiras , a scholarship programme from the Brazilian Government. The knowledge obtained in this study will be used to design better and more effective conservation strategies for this species. I was delighted that my PhD project was chosen to feature in one of the films to celebrate TAMAR’s 35th anniversary:

#ExeterMarine is a interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!