The carbon dioxide in the atmosphere has risen by over 100 ppm since the industrial revolution due to anthropogenic input. The ocean has absorbed about one third of the anthropogenically derived CO2, lowering the calcium carbonate saturation state of seawater and reducing the average global surface ocean pH by 0.1 pH unit, a process termed ‘ocean acidification’ [1]. The combination of ocean acidification (OA) and global warming (GW) may trigger major shifts in marine ecosystems [2]. 

 

Regarding ecosystem functioning, OA and GW not only affect the behavior of single species, but also the structure and dynamics of communities [3]. Calcifying organisms are by far the most affected by climate change. By secreting calcareous skeletons, they create permanent, complex in physical architecture carbonate structures that increase biodiversity by providing nursery areas, shelter and substrate for colonization [4]. 

 

Previous studies showed that some calcifiers adjust their physiological status through phenotypic plasticity to the constantly changing environments around them in order to maintain optimal levels of energy production, growth and reproductive investments. However, phenotypic plasticity, which is evident in bryozoans [5,6,7] and in coralline algae [8,9] does have a cost. How do calcifying organisms cope with OA and GW? The capability of a given species for phenotypic buffering and physiological plasticity for adaptation should be investigated for the relatively long generation length of calcifiers, which is important for the evolutionary potential of a species [10].

 

One key function of vegetated coastal habitats - such as seagrass meadows - is their role as carbon sinks (blue carbon), and their production is used to support ecosystem functions (Duarte and Cebrián, 1996). Blue carbon sinks are strongly autotrophic, which means that these ecosystems fix CO2 as organic matter in excess of the CO2 respired back by biota (Duarte and Cebrián, 1996; Gattuso et al., 1998; Duarte et al., 2005a), thus removing CO2 from the water column, increasing pH. This process may thus attenuate the effects of OA on calcifiers.

 

The aim of the PhD project is to address if seagrass physiological processes (i.e. photosynthesis) act as buffer to OA on the epiphyte community. In particular, the focus will be on the epiphytic calcifiers, such as bryozoans, serpulid polychaetes and coralline algae, and their possible changes in the biomineralization processes (i.e. growth rate, morphology, mineralogy, element composition) by comparing individuals naturally adapted to live near CO2 vent area with individuals from non-effected areas.

 

In detail, the objectives are: 

 

Blue carbon system taken in consideration will be the seagrass Posidonia oceanica (L.) Delile meadow and the experiments will be carried out on calcifying epiphytes with the use of 'mimics' [11,12], artificial leaves and rhizomes mimicking natural features of P. oceanica shoots. Mimics will be transplanted along a pH gradient at the natural CO2 vent area of Ischia (Naples, Italy) and in the control area at the Marine Protected Area of Monterosso al Mare (La Spezia, Italy). Also, experiments will be performed under controlled conditions where the target organisms will be exposed to altered environmental conditions (temperature, pH, light). Physiological and mineralogical responses will be analysed in bryozoans and coralline algae with the overall aim to clarify the 'gaps' in biomineralization processes and understand their potential to adapt in the future oceans.

 

Candidate will get experience in laboratory and field work activities (underwater sampling). He/She will learn the following techniques: oxygen chambers, total alkalinity, inhibitors ( carbon acquisition mechanism), Scanning Electron Microscopy (morphology and taxonomy),Raman (mineralogical analyses), Microprobe (geochemical analyses), nanoCT (Structural integrity).

 

Being based at the Marine Environment and Sustainable Development Unit of Santa Teresa of La Spezia (ENEA - Italian national Agency for New Technologies, Energy and Sustainable Economic Development, Partner of the University of Pavia), candidate will have access and use the culturing facilities and perform the experiments under controlled conditions, plan, develop and realize the field work using boat and diving facilities at the ENEA, perform some of the analyses using instruments available at the laboratories Santa Teresa (ENEA) and Department of Earth and Environmental Sciences (University of Pavia). 

 

Because of the ongoing collaborations of Marine Environment and Sustainable Development Unit of Santa Teresa with some local Marine Protected Areas (Cinque Terre National Park La Spezia), the candidates will have the opportunity to work also in areas of marine biodiversity protection and conservation. During 6 months at the University of Algarve, the candidate will use the mesocosm facility of the Center of Marine Sciences, CCMAR, to test hypothesis generated by the field observations. Cultivation conditions that may be controlled in the mesocosms are pH, temperature, light and nutrients. 

 

The field work will be carried out at natural CO2 vents area of Ischia (Naples), in collaboration with Stazione Zoologica. There is a formal agreement between the ENEA and the SZN, as well as a former Mares PhD co-tutoring project. The facilities used are at the Villa Dohrn structure, located in the island of Ischia (4 km from the Castello vent’s area) where the benthic ecology team of the SZN and the group of Gambi M.C. is operating. Other facilities available for the project are running sea water system and aquaria, thermostatic rooms, stereo- and optical microscopes, chemical room, -20 °C and – 80°C freezers, oven and muffle, balances, deep-dryer, boat and some Scuba diving equipment for field work support.

 

Being part of an international context, ENEA, University of Pavia, University of Algarve and SZN regularly host scientists from all over the world, who collaborate in several projects and give seminars/lectures for scientists and students. Also congresses and meetings are often organized and promoted by these institutes. These scientific exchanges and activities offer opportunities to the candidate to meet expert in several fields, develop collaborations with scientists regularly or occasionally working and visiting the institutes and build the base for her/his future carrier. 

 

References