Biodiversity Data Journal :
Data Paper (Biosciences)
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Corresponding author: Lea Katz (leasavinakatz@gmail.com)
Academic editor: Anne Thessen
Received: 04 May 2021 | Accepted: 20 Jul 2021 | Published: 23 Aug 2021
© 2021 Lea Katz, Damien Sirjacobs, Sylvie Gobert, Pierre Lejeune, Bruno Danis
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Katz L, Sirjacobs D, Gobert S, Lejeune P, Danis B (2021) Distribution of macroalgae in the area of Calvi (Corsica). Biodiversity Data Journal 9: e68249. https://doi.org/10.3897/BDJ.9.e68249
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Macroalgae play a structuring role in benthic ecosystems, which makes it very important to monitor their cover rates and study their community structures and changes in time. Such studies are usually led by autonomous divers and often do not generate sufficient data to provide enough material for strategically-sound conservation plans. This paper describes the dataset generated in the framework of the evaluation of the potential of a complementary data acquisition method: annotating videos transects obtained using an underwater Remotely Operated Vehicle (ROV).
The focus was on Cystoseira brachycarpa, together with the abundance of several other macroalgae species, which could be identified using the ROV images after validation through specimen identification. Furthermore, in order to allow future uses, such as monitoring the status of colonisation of the invasive algae Caulerpa cylindracea, the ROV was sent to some deeper transects on sedimentary habitats (40 m) below the Posidonia meadows lower limits.
The project, while providing some interesting insights on using a ROV as a tool to study marine biodiversity, generated a dataset for the distribution of 19 macroalgae on both standardised and new transects in the Bay of Calvi (
The videos also showed that the invasive algae Caulerpa cylindracea has spread between 2016 and 2019 and that more focused studies should be held in the Bay to assess the actual reach and possible impacts of this invasion.
Finally, our ROV video transects have also underlined the significant presence of particular benthic macroalgae communities over habitat zones described as "soft-bottom" on benthic habitat maps. Although the biomass per unit area of these communities is probably lower than for most coastal rocky bottoms, this widely-spread habitat type holds a contribution to primary production to be considered in coastal ecosystem models.
macroalgae, ROV, Calvi, Cystoseira, Caulerpa, benthic habitat
As macroalgae play an essential role in benthic ecosystems, it can be very important to monitor their cover rates and study their community structures. A good knowledge on algae distributions of an area can tell us a lot about the dynamics of the ecosystem, its resilience and the pollution in the area. For example, the analysis of the cover rates of different macroalgae, often used as bioindicators of environmental disturbance, in particular the genus Cystoseira, allows us to assess the impacts and pressures of environmental changes in the Bay of Calvi. Such approaches already exist for Cystoseira in the Mediterranean (
There are several approaches to studying macroalgae distributions. The most common method is by autonomous divers. Diver-based surveys are relatively simple to carry out and generate data with a high level of precision. However, this method has some caveats: there is a need for highly experienced autonomous divers, it can be destructive and is limited in time and depth and, thus, can only be used for small scale studies. Using a Remotely Operated Vehicle, equipped with cameras filming the bottom, can address many of these problems. It not only optimises the sampling design, but also generates much more data in less time.
In this project, the distribution of 19 macroalgae were recorded, but the focus was put on the species Cystoseira brachycarpa and Caulerpa cylindracea. The Cystoseira “forests” represent the largest biomass in the rocky bottoms of the Mediterranean and give the seascape a tri-dimensional structure, which makes them key species for the ecosystem because they serve as a habitat for many benthic organisms (
Caulerpa cylindracea is an invasive algae originating from southwest Australia. Along with Caulerpa taxifolia, another invasive species of the same genus, it has invaded many of the coastal habitats of the Mediterranean Sea (
Located in the northwest of Corsica (Fig.
In the Mediterranean, the most diverse benthic communities are found in the coastal areas, but these areas are also amongst the most exposed to fishing, as well as disturbances arising from urbanisation and industrialisation of the coast as corollary expansions of infrastructure for expanding tourism activities. Calvi, the city located in the centre of our area of interest, sees its population increasing 60-fold every summer (more than 360,000 inhabitants,
Two Natura 2000 areas from the "Habitats Directive" network are present in the Bay of Calvi (Fig.
The dataset describes the recent state of macroalgae distributions in the area of Calvi and suggests a new sampling method that could benefit ongoing monitoring actions. The sampling campaigns were designed to follow-up on previous algae surveys in the area and were carried out on the same standardised transects. Therefore, the data we provide can be used to study the evolution of macroalgae distributions on a 40 year-span (since 1979,
Evaluation of ROV imagery for the study of macroalgae communities in the Bay of Calvi, Corsica. Masters Thesis
This project was driven by Lea Katz's Masters Thesis, co-supervised by Damien Sirjacobs, Sylvie Gobert (Université de Liège) and Bruno Danis (Université Libre de Bruxelles). NB: First sampling campaign in 2016 was led by Antonio Aguera Garcia (Université Libre de Bruxelles) and Damien Sirjacobs.
The area of interest was the near-shore area of the Bay of Calvi (Fig.
This Masters Thesis was organised and funded by the Marine Biology Lab of the Université Libre de Bruxelles. The project received logistics support from the STARESO station, Université de Liège (Pierre Lejeune). The project was also part of the STARE-CAPMED framework (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts), which aims to "improve the understanding of how different coastal marine ecosystems function in the Mediterranean and describe the influence of local and global pressures on the processes that govern its functioning" (
The project included two sampling campaigns. Both campaigns covered the same geographic area (see "geographic coverage"). The underwater ROV was guided over several standardised transects to film the bottom (Fig.
In both campaigns (2016 and 2019), an underwater Remotely Operated Vehicle (ROV) was deployed in the Bay and navigated along straight transects perpendicular to the coastline. To choose the location of our transects, we considered previously-studied transects in older studies that focused on the same macroalgae communities (
In the 2016 campaign, a mini-ROV VideoRay Pro 3 (Fig.
Videos were visualised and annotated using the software "COVER" (
One transect was replicated by a team of divers who carried out independent identifications. This proved that our ROV/video survey method was robust and provided similar results for main taxon levels (cfr. "Taxonomic coverage").
The area of interest is the Bay of Calvi (Corsica, Mediterranean Sea). Total coverage of the dataset is the extent of 17 ROV transects (12 carried out in 2016, five in 2019), perpendicular to the coastline. Transects are distributed in the whole Bay of Calvi, Corsica (Mediterranean Sea). More specifically, the area between Punta Revellata and Punta Spano was the focus of our study (Fig.
42.553 and 42.617 Latitude; 8.709 and 8.83 Longitude.
Rank | Scientific Name |
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species | Acetabularia acetabulum |
species | Amphiroa rigida |
species | Caulerpa prolifera |
species | Caulerpa cylindracea |
species | Codium bursa |
species | Colpomenia sinuosa |
species | Cystoseira brachycarpa |
species | Cystoseira crinita |
species | Cystoseira spinosa |
species | Cystoseira zosteroides |
species | Flabellia petiolata |
species | Halopteris scoparia |
species | Osmundaria volubilis |
species | Padina pavonica |
species | Peyssonnelia squamaria |
genus | Dictyota sp. |
genus | Halopteris sp. |
genus | Jania sp. |
order | Corallinales |
Two sampling campaigns were held, one in July 2016 and one in June 2019.
This is the dataset associated with the datapaper. Each transect that was studied is referenced geographically. The dataset represents the presence of the algae species on the transects.
Column label | Column description |
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occurrenceID | ID label of the occurrence |
eventID | ID label of the event (transect) |
basisOfRecord | What the record is based on. Only "HumanObservation" in this case. |
type | Type of observation. Only "MovingImage" in this case, since the observations were made from videos. |
recordedBy | Name of the observer. Here : Lea Katz |
kingdom | Kingdom of the observed specimen |
scientificName | Scientific name of the observed specimen |
taxonRank | Taxon rank of the observed specimen |
eventID | ID label of the event (transect) |
InstitutionCode | Code name of the institution. Here : ULB (Université Libre de Bruxelles) |
eventDate | Date of the event |
year | Year of the event |
month | Month of the event |
day | Day of the event |
decimalLongitude | Longitude coordinate of the mid-point of the transect |
decimalLatitude | Latitude coordinate of the mid-point of the transect |
footprintWKT | Well-known text representation of the geometry of the sampling event. Here : "LINESTRING" because the transects are linear. |
maximumDepthInMetres | Maximum depth of the transect in metres |
waterBody | Water body where the sampling took place. Here: Mediterranean Sea |
higherGeography | Geographic region where the sampling occurred |
island | Island around which the sampling occured. Here: Corsica |
countryCode | Code of the country where the sampling occurred. Here: "FR" (France) |
GeodeticDatum | Spatial reference system upon which the geographic coordinates given in decimalLatitude and decimalLongitude are based. Here: WGS84 (World Geodetic Datum 1984) |
CoordinateUncertaintyInMetres | Uncertainty of the GPS coordinates. In metres. |
SampleSizeValue | Length of the transect |
SampleSizeUnit | Unit of the "SampleSizeValue". Here: "metres" |
samplingProtocol | Protocol used for the sampling event. Here: "Remotely Operated Vehicle" |