Ana Alexandra Aranda
da Silva (Xana)

I decided I wanted to become a marine biologist at the age of 15. I completed my first degree in Marine Biology and Ecology at the University of Plymouth in 1998, and my honours project title was "Spatial variation of meiofauna on a tropical sandy beach, Mozambique". I decided then that meiofaunal invertebrates were what I wanted to work with. So, I went on to do an MSc in Coastal Zone Management at Bournemouth University, as a way of broadening my view on the marine environment. During my masters degree I had the opportunity of working for the NGO Plan International, for 3 months in the Philippines, as part of a project combining the protection of the environment and the reduction of poverty. My project tile was "Community-based fisheries management within the Northern Sierra Madre Natural Park, Isabela, Philippines" (Aranda da Silva, 2002). After this, I decided to go back to meiofaunal invertebrate research.

I have just started a postdoc in Portugal on “Benthic protozoan community attributes in relation to past and present environmental gradients of the Portuguese canyon systems”. I am based at INETI (National Institute of Engineering, Technology and Innovation, I.P) in Lisbon and the Department of Biology of the University of Aveiro, and will conduct some of the work at the Molecular Systematics Group at the University of Genève, Switzerland and continue a very close collaboration with the DEEPSEAS Group.

Current Research Interests

• Benthic protozoan community attributes in relation to past and present environmental gradients of the Portuguese canyon systems

Foraminifera are protists that often dominate modern deep-sea benthic communities. Hard-shelled species have an outstanding fossil record and are widely used to reconstruct ancient environments using ecological inferences based on living species. However, there have been few studies of foraminifera in submarine canyons because these topographically complex areas are difficult to access. The EU 6th Framework Integrated Project HERMES (Hotspot Ecosystem Research on the Margins of the European Seas) recognised the importance of the major canyon systems (Nazaré and Setúbal) off Portugal. I will conduct a 3-year project, embedded within HERMES, to study foraminiferal distributions on this margin using a mixture of morphological approaches and modern molecular methods. The hypotheses addressed are that: 1) the abundance, species diversity and composition of foraminiferal assemblages on the Portuguese margin are influenced by submarine canyons and by a biogeographic boundary recognised in other faunal groups, and 2) fossil assemblages in core samples from the canyons reflect climatic and oceanographic changes during the Quaternary.

• The global distribution of Gromia – to study Gromia from Antarctic and other localities around the globe to compare to deep-sea gromiids from the Arabian Sea.

Other Research Interests

• Benthic protists from the Arabian Sea (Aranda da Silva, 2005)

"Live” (stained) and dead macrofaunal (>300 µm fraction) foraminifera in multicorer samples (0-1 cm and 0-5 cm layers) were analysed at six stations along a transect (100-3400 m water depth) across the Oman margin (Arabian Sea) oxygen minimum zone (OMZ). Very high abundances (2858 per 25.5 cm2), dominated by Uvigerina ex. gr. semiornata, were found in the upper 100 m. The 850 m site also had elevated abundances. These peaks probably represented upper and lower OMZ boundary edge effects, respectively. A total of 199 live species was recognized. Diversity was depressed between 100 m and 850 m and relatively higher at the 1250 m and 3400 m sites. Vertical distribution in the sediment reflected responses found across the horizontal gradient, with species concentrated in the top sediment where bottom-water oxygen concentration was low and distributed more evenly through the sediment where concentration was higher. In general foraminifera and metazoan responded similarly to oxygen and food availability, except that the lower boundary of edge effect was located at a shallower depth (700 m) for the metazoans. Live:dead ratios of foraminifera increased with water depth.

Some of the “live” foraminifera species found across the Arabian Sea OMZ. (Top left) Bulimina aculeata (500 µm), (Top centre) Chilostomella oolina (866 µm), (Top right) Rectuvigerina cylindrica (920 µm, (Middle left) Lenticulina sp.1 (466 µm), (Middle right) Globobulimina auriculata (300 µm), (Bottom left) Globobulimina pyrula (566 µm), (Bottom right) Globobulimina turgida (433 µm). Photographs taken by A. Hendersen using Palaeovision system in the Natural History Museum.

Gromia is a large marine protist with filose pseudopodia and an organic test that is abundant in the bathyal Arabian Sea. Deep-water Gromia-like morphospecies were discovered in the 1990’s but their relation to shallow-water species was not established. Little is known about gromiid diversity, reflecting the fact that these relatively featureless protists have few characters useful for species identification. Consequently, ultrastructural and molecular techniques were used to examine gromiid diversity on the Oman and Pakistan margins of the Arabian Sea (water depths 1000-2000 m). In total, 27 deep-sea gromiid sequences of the SSU rDNA gene and 6 sequences of the ITS rDNA region were obtained (Aranda da Silva, 2006). The data confirmed that Gromia-like protists from the bathyal deep sea are related to shallow-water gromiids. Among Arabian Sea Gromia, seven lineages were identified based on molecular evidence. Five of them form a monophyletic group branching as a sister group to shallow-water species. Four lineages can be defined morphologically, while grape-like morphotypes include 3 lineages that cannot be distinguished morphologically. Each lineage probably represents a separate species, implying that deep-sea gromiid diversity is higher than indicated by their simple morphology. Morphological analysis adds 2 more species, giving a total of 9 deep-sea gromiid species, adding considerably to the number of known marine gromiids, only three of which are currently described.

Light photographs of extracted specimens for phylogenetic analysis.

• ICZM (Integrated Coastal Zone Management)
  
• Meiofauna distribution from Sandy beaches
  (Aranda da Silva, 1998 BSc thesis)
  
• Curriculum vitae