Research

In recent decades, work has sought to identify and assess the geomorphological and environmental changes undergone by the Mediterranean. Acoustic (geophysical) remote sensing has mapped part of the seafloor relief, bedforms and subsurface geology, but coverage remains small. Extensive areas, especially shallower than 300–400 m, are still unexplored and many scientific questions remain open.

The study of palaeoclimatic and geomorphological change in the South Aegean and connected marine physiographic units is a scientific priority, because these changes largely shaped the palaeoenvironmental conditions of the Eastern Mediterranean. Sea-level response to palaeoclimate caused emergence or submergence of the shelf and thereby provided land bridges for prehistoric people and other organisms.

Another essential issue for the sustainable management of marine ecosystems is knowledge of the type, quality, quantity and spatial distribution of present-day marine habitats.

These questions fall within the South Aegean Region’s priorities for Environment and Sustainable Development. The necessary primary data will be collected during the research cruises of R/V Alkyon.

WP 3 also secures the operation of the Station’s laboratories and of R/V Alkyon’s operational capacity through regular inspection/maintenance and the upgrade/completion of laboratory, scientific, technical, nautical and electromechanical equipment.

It further provides full training of new scientific staff of HSR / HCMR in the use and maintenance of Alkyon’s existing scientific equipment (multibeam echosounder / MBES, sub-bottom profiler / SBP, CTD, ADCP and others) and of equipment purchased under the project (ROV, gravity corer and others). The ROV is used across research (sampling, filming), education and HCMR rescue operations (wreck documentation, recovery).

ROV training is in-house with HCMR’s ROV team or at a specialised centre abroad (ROV Pilot/Technician Grade II, in line with IMCA C 005).

Equipment and maintenance

Beyond research, recruitment and training, WP 3 includes:

– completing Alkyon’s scientific equipment with a gravity corer;

– completing navigation equipment of Alkyon and of launch Kirki with instruments such as AIS;

– computers, peripherals and accessories for HSR and Alkyon;

– regular inspection/maintenance of electromechanical equipment of Alkyon and Kirki (inboard engines, winches, Alkyon’s A-frame and Kirki’s outboard) in the first and second project years;

– regular inspection/maintenance of the SBE19 Seacat Profiler and SBE33 deck unit of the CTD system;

– regular inspection/maintenance, for two years (1+1), of the IMU subsystem of the multibeam echosounder;

– nautical equipment (ropes, floats and others) and electromechanical spare parts;

– maintenance tools and electronic, electrotechnical and electrical devices and materials.

Past sea-level change and geoarchaeological potential

Past climate change raised and lowered sea level: in cold (glacial) periods it stood 110–130 m below today’s position and in warm (interglacial) periods 5–10 m above it. During glacial phases most shelves were land; during interglacials the sea flooded them.

Alkyon’s equipment allows detailed bathymetric and geomorphological mapping of the South Aegean coastal and submarine space and the identification of sedimentary and erosional traces of long-term sea-level movement. Case studies will be carried out in island groups (e.g. Kos–Kalymnos–Pserimos, Naxos–Paros–Mykonos–Delos–Rineia). Palaeogeographic connections will be reconstructed in successive time steps and geoarchaeological potential assessed, highlighting underwater cultural heritage.

Present habitats and geological substrate

Habitat maps have become essential for environmental monitoring, spatial planning and the assessment of marine resources. Less than 5–10% of the sea area has been mapped at a resolution comparable to terrestrial habitats.

Mapping of substrate types around Rhodes under INTERREG GR-CY 2007–2013 “AKTI” produced derived seafloor parameters and contributed to habitat mapping. Existing information will serve as a reference and will be compared with new data from the same area and method, to identify change over the last 7–8 years. WP 3 information will be combined with WPs 5–7 to produce marine-habitat distribution maps.

The coastal zone of the South Aegean islands is a complex, sensitive system under continuous geomorphological and environmental change from natural and human processes. Studying the morphodynamic evolution of beaches and understanding, assessing and operationally forecasting the behaviour of coasts on selected, highly touristic islands (e.g. Rhodes, Kos, Santorini) is a priority for their integrated management.

Scientific approach

A) Collection of existing data: meteorological parameters, onshore and submarine topography, hydrology and hydrogeology, geology and tectonics, land cover and use, protected areas, soils and sediments, socio-economic parameters.

B) Long-term (multi-decadal) shoreline change from historic air photos and satellite images, georeferenced to the Hellenic Cadastre orthophoto mosaic, digitised in ArcGIS and quantified with the Digital Shoreline Analysis System (DSAS).

C) Topographic and bathymetric survey, collection and analysis of coastal sediments with existing and new HSR and Alkyon equipment, and unified digital elevation models.

D) Boussinesq-type numerical wave models (shoaling, refraction, diffraction, reflection/transmission, bottom friction, breaking, run-up, frequency and directional spreading, non-linear interaction) and sediment-transport simulation with MIKE 21 and open-source software, under ordinary and extreme conditions of the next 50 and 100 years.

E) Coastal vulnerability to sea-level rise from geomorphology, shoreline-change rate, slope, wave height, tide and relative sea-level rise. Three IPCC scenarios (baseline, optimistic, pessimistic) will be examined.

F) Management actions: risk assessment, warning-system design, impact factors, and warning evaluation and transmission.

G) A dynamic, multi-dimensional strategy for Integrated Coastal Zone Management (ICZM).

Ecological quality of benthic communities

The principle of water “ecological quality” was developed by the European Union as a policy framework; its innovation is the use of biological indicators. Implementation of the Water Framework Directive (2000/60/EC) in Greece began in 2012 with HCMR as implementing body and the national surface-water monitoring network. 121 stations are monitored (85 coastal, 36 transitional). The three core biological quality elements are phytoplankton, phytobenthos and zoobenthos.

Benthic communities of the South Aegean have been studied only opportunistically, except around Rhodes. Off the Station aquarium there is a surveillance station whose ecological status, based on zoobenthos, is assessed as high.

WP 5 investigates the ecological status of coastal areas of Rhodes, Kos, Naxos, Koufonisia and Santorini using the BENTIX index (Simboura & Zenetos, 2002). Results will be combined with the other research WPs to map habitats and pressures. Basic equipment will also be completed for the aquarium science – benthic ecology – biopathology laboratory created under WP 1.

Recording alien species

Biological invasions have produced an environmental crisis through climate change and human activity. More than 1,000 alien species (including cryptogenic; Zenetos et al., 2022) have been reported in the Mediterranean, driven by the Suez Canal, international trade, aquaculture and the aquarium trade.

Public participation can be an important source of data on distribution, abundance, behaviour and impacts. Recording South Aegean alien species through citizen science is an equally important WP 5 aim. Collection is via a platform on the Station website, with information on species already recorded or expected, and a photography guide.

Human impacts and diving routes

Plastic pollution has become a major threat to biodiversity. East of Rhodes, off Lindos, lies the Mediterranean’s second-deepest point (4,433 m) and a key cetacean habitat. Rhodes’ coastline remains one of the few remaining nesting areas for Caretta caretta and Chelonia mydas. Recent strandings have shown deaths mainly from ingested plastics.

WP 1 laboratories and WP 5 equipment can support stomach-content studies of stranded cetaceans and turtles. The Station will organise information actions on plastics, recycling, beach clean-ups and workshops on cetaceans and turtles.

Underwater caves are priority habitats (Habitats Directive, code 8330). More than 600 marine caves have been recorded in the Aegean, most in the south. Caves and their species will be located, recorded and mapped, and diving routes designed.

WP 6 is an interdisciplinary study of human and climate pressures on South Aegean seagrass meadows. Its main aim is to assess meadow health and key ecosystem services, understand responses to multiple pressures, and set a basis for future monitoring.

Seagrass meadows are among the most valuable coastal ecosystems (biodiversity, coastal protection, carbon storage) but are declining globally by about 1.5% a year. The Mediterranean is warming two to three times faster than the global ocean. Endemic Posidonia oceanica forms extensive meadows, protected as a priority habitat (1120*). Ecological models have projected functional extinction by 2049 — most of the data coming from the western Mediterranean.

Warming favours the spread of alien macrophytes such as Halophila stipulacea. Posidonia meadows are outstanding blue-carbon stores, but estimates for the eastern Mediterranean are lacking. WP 6 will produce primary information on population dynamics, demographic profiles and blue-carbon potential of South Aegean P. oceanica, contributing to European protection strategies (Habitats, Water Framework, Marine Strategy, Biodiversity) and sustainable growth (Blue Growth).

Methodology

The study focuses on P. oceanica meadows in South Aegean areas with different environmental and biogeochemical conditions and human pressures.

Assessment of resilience and vulnerability under different climate and human pressure. Mapping of the extent and volume of P. oceanica reefs with high-resolution seismo-acoustic methods (side-scan sonar, multibeam, sub-bottom profiler). Reconstruction of shoot-growth history from leaf and flower scars on the long-lived rhizome.

Sedimentation and blue-carbon storage from sediment cores (~1 m): organic and inorganic carbon, δ13C of tissues and sediments, and 210Pb profiles for accumulation rates. Investigation of tipping-point theory for a possible shift of meadows from carbon sinks to sources.

For the management of human activities, the Marine Strategy Framework Directive (2008/56/EC) follows the ecosystem approach so that cumulative pressure remains compatible with Good Environmental Status (Law 3983/2011).

WP 7 assesses the current ecological status and ranks pressures and threats on marine habitat types of the South Aegean coastal zone, in selected areas of the Cyclades and Dodecanese, with emphasis on the Natura 2000 network.

Structural and functional elements of reefs and Posidonia oceanica meadows — habitats of Community interest 1170 and 1120 (Directive 92/43/EEC) — will be studied. These hold the highest biomass in coastal Mediterranean ecosystems and support a wide range of ecosystem services. Indicators will take account of benthic-community and fish-population composition.

Many marine animals perceive their environment through sound, which travels far better than light and is used in communication, navigation, orientation, feeding and predator detection. Anthropogenic noise can reduce communication ranges (masking), disrupt reproduction, affect energy budgets, exclude animals from habitats, cause chronic stress, hearing loss, injury and, in extreme cases, death.

The Marine Strategy Framework Directive (2008/56/EC) includes underwater noise under Descriptor 11. For continuous noise it requires assessment of the spatial distribution, temporal extent and levels of continuous low-frequency sound, focusing on bands around 63 and 125 Hz, where shipping noise dominates.

South Aegean waters host at least seven marine mammal species: Risso’s dolphin, bottlenose dolphin, striped dolphin (IUCN Vulnerable), common dolphin (Endangered), Cuvier’s beaked whale, sperm whale (Endangered) and the critically endangered Mediterranean monk seal, as well as many fishes and invertebrates.

Assessment will use mathematical modelling, in cooperation with the National MSFD Monitoring Programme. Steps include collecting environmental data (bathymetry, seasonal T/S, seabed type), choosing parameters and a propagation model, describing the source from AIS (and possibly VMS) data, computing the contribution of all sources, and mapping noise levels.