Description
This dataset contains sessile benthic coverage data derived from photographic quadrat samples collected in two time periods (2008–2009 and 2024) at two coastal sites in Northern Crete: Alykes (Heraklion) and Elounda Bay (Agios Nikolaos). Sampling was conducted along two transects per site at five depths (1 m, 5 m, 10 m, 15 m, and 20 m), using two quadrat sizes (25×25 cm and 100×100 cm) to capture replicate images. The data offer valuable insights into temporal shifts in sessile organism communities, highlighting changes potentially linked to climate change and the increasing presence of invasive herbivorous fish species, such as siganid fish and diademid sea urchins.
Data Records
The data in this sampling event resource has been published as a Darwin Core Archive (DwC-A), which is a standardized format for sharing biodiversity data as a set of one or more data tables. The core data table contains 587 records.
2 extension data tables also exist. An extension record supplies extra information about a core record. The number of records in each extension data table is illustrated below.
This IPT archives the data and thus serves as the data repository. The data and resource metadata are available for download in the downloads section. The versions table lists other versions of the resource that have been made publicly available and allows tracking changes made to the resource over time.
Versions
The table below shows only published versions of the resource that are publicly accessible.
How to cite
Researchers should cite this work as follows:
Rallis I, Chatzigeorgiou G, Skouradakis G, Vernadou E, Polychroni T, Pavlidis D, Papagiannopoulos G, Dailianis T (2025). Sessile Benthic Assemblages in Northern Crete assessed from Photographic Quadrats (2008–2024). Institute of Marine Biology, Biotechnology and Aquaculture - Hellenic Centre for Marine Research, Greece. Dataset.
Rights
Researchers should respect the following rights statement:
The publisher and rights holder of this work is Hellenic Center for Marine Research. This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.
GBIF Registration
This resource has not been registered with GBIF
Keywords
Sessile; Epibenthic; Benthos; Reefs; Samplingevent; Eastern Mediterranean; Aegean Sea; Biodiversity Shifts; Sublittoral; Hard Substrate
Contacts
- Custodian Steward
- Metadata Provider ●
- Point Of Contact
- Custodian Steward
- Custodian Steward
https://orcid.org/https://orcid.org/0000-0001-6775-530X
- Custodian Steward
Geographic Coverage
Two areas in Northern Crete, Alykes and Elounda
| Bounding Coordinates | South West [35.25, 24.97], North East [35.42, 25.76] |
|---|
Taxonomic Coverage
Functional Groups: Bivalvia, Erect Chlorophyta, Massive Sponge, Hexacorallia, Mobile Fauna, Mucilage-forming Microalga, Barnacles, Boring Sponges, Massive Chlorophyta, Massive Phaeophyceae, Canopy, Colonial Ascidian, Calcareous Erect Algae, Erect Rhodophyta, Encrusting Sponge, Solitary Ascidian, Encrusting Rhodophyta, Erect Bryozoa, Padina pavonica, Encrusting Chlorophyta, Encrusting Bryozoa, Encrusting Habitat-forming Rhodophyta, Tube-forming Polychaeta
| Phylum | Porifera (Sponges), Mollusca (Mollusks), Chlorophyta (Green algae), Rhodophyta (Red algae), Ochrophyta (Brown algae), Cnidaria |
|---|---|
| Class | Ascidiacea (Sea squirts), Polychaeta (Scale worms) |
| Subclass | Cirripedia (Barnacles) |
Temporal Coverage
| Start Date / End Date | 2008-06-01 / 2024-06-30 |
|---|
Project Data
MARine Biodiversity and Ecosystem Functioning leading to Ecosystem Services MARBEFES project has received funding from the European Union’s Horizon Europe research and innovation programme under Grant Agreement no 101060937
| Title | MARBEFES |
|---|---|
| Identifier | https://marbefes.eu/ |
| Funding | This Project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement no 101060937 |
| Study Area Description | The MARBEFES project is structured around the concept that biodiversity is a continuous and interconnected system across space and time, beyond traditional boundaries like ‘estuary,’ ‘coast,’ and ‘offshore.’ This approach helps to avoid compartmentalized thinking that might limit our understanding of marine ecosystems. MARBEFES explicitly considers the river-to-ocean gradient, utilizing 12 Broad Belt Transects (BBTs) across the four main marine regions of the EU – the Arctic, Baltic, Atlantic, and Mediterranean. These transects serve as the core of MARBEFES research, providing data to understand biodiversity trends and their impacts across Europe. |
Sampling Methods
Sampling was conducted through non-destructive underwater photographic surveys of fixed-area quadrats. Two permanent transects were established in each study area (Alykes and Elounda) and sampled at five depths (1, 5, 10, 15, and 20 meters) during spring seasons of 2008, 2009, and 2024. At each depth, five photographic quadrats (either 25×25 cm or 100×100 cm) were positioned along the transects on hard substrates. Each image was later analysed using a stratified point count method with 100 randomly distributed points per photo to estimate the percent cover of sessile macrobenthic taxa.
| Study Extent | The study was conducted in northern Crete, specifically in the coastal areas of Alykes and Elounda. Sampling took place during the spring seasons of 2008, 2009, and 2024, with two transects surveyed per site each year across five depth zones (1, 5, 10, 15, and 20 meters). The study focuses on hard substrate habitats and is representative of typical rocky reef environments in the eastern Mediterranean. |
|---|---|
| Quality Control | Quality control began with structuring the data into a tidy format and applying Darwin Core standards. Taxonomic names were validated via the WoRMS Taxon Match Tool, which uses exact and fuzzy matching to assign AphiaIDs, authorities, and classification metadata. Geographic coordinates were visually inspected using the OBIS Map Tool, generating WKT geometries and calculating centroids and uncertainty radii to confirm sampling locations in marine zones and identify outliers. The dataset then underwent comprehensive QC using the LifeWatch/EMODnet Biology Biocheck tool, which assesses schema compliance, taxonomy, spatial consistency, occurrence and measurement records against EMODnet standards. Finally, metadata were created and published via the MedOBIS IPT, facilitating dataset exposure to OBIS/GBIF and enabling harvesting by international repositories. |
Method step description:
- Photographic sampling was conducted during spring surveys in 2008, 2009, and 2024 at two coastal locations in northern Crete (Alykes and Elounda). At each site, two transects were established and surveyed at five fixed depths (1, 5, 10, 15, and 20 meters). Photoquadrats (25×25 cm or 100×100 cm) were positioned on hard substrates and photographed using underwater digital cameras equipped with scale frames. Images were later analysed using the stratified random point count method (100 points per quadrat), following established benthic assessment protocols. Data were digitised into a tidy format and standardised using Darwin Core terminology. Taxonomic names were matched to authoritative AphiaIDs using the WoRMS Taxon Match Tool. Coordinates were validated using the OBIS Maptool. Quality control was performed using the LifeWatch/EMODnet Biology RShiny tool, and final metadata were prepared and published via the MedOBIS IPT following OBIS data publishing standards.
Additional Metadata
| Alternative Identifiers | 10.25607/meaq9b |
|---|---|
| https://ipt.medobis.eu/resource?r=sessile-benthos-alykes-elounda-2008-2024 |