the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Apr 2025
Long-term plankton and environmental monitoring dataset from the Marine Protected Area of the Iroise Marine Natural Park (2010–2023) in the Iroise Sea, North Atlantic
Abstract. This data paper presents a long-term monitoring dataset of phytoplankton (2010–2022) and zooplankton (2010–2023) communities, as well as associated environmental parameters (2010–2023), from the Iroise Marine Natural Park, Iroise Sea, North Atlantic, France's first Marine Protected Area. The dataset combines traditional microscopy-based phytoplankton counts with zooplankton data (abundances) obtained from digitized images using the ZooScan imaging system, along with surface and bottom temperature and salinity measurements. Sampling was conducted seasonally along two main transects and three coastal stations, capturing both spatial and temporal dynamics of plankton communities. Phytoplankton was identified at the species level by the same taxonomist during all the time-series (573 taxa in total). From their individual images, zooplankton was automatically sorted into 103 taxonomic and morphological groups, validated by an expert, and compiled into a data table allowing both community and individual approaches using abundances and biovolumes at both individual and community levels. Individual zooplankton images have also been made available for further morphometric analyses. This 14-year long, spatially and temporally resolved zooplankton imaging dataset is part of an ongoing effort to enhance the availability of zooplankton imaging data, locally and globally. This, as a whole dataset, can be used to study the influence of coastal-offshore environmental gradients on marine plankton biodiversity patterns, especially in protected waters at the intersection of the English Channel and the Atlantic Ocean, in a region characterized by the presence of the Ushant front.
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RC1: 'Comment on essd-2025-207', Anonymous Referee #1, 26 May 2025
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ESSD-2025-207
Long-term plankton and environmental monitoring dataset from the Marine Protected Area of the Iroise
Laetitia Drago et al.
GENERAL COMMENTS
This manuscript presents a valuable long-term dataset of phytoplankton (2010–2022) and zooplankton (2010–2023) collected across 15 stations in the Iroise Marine Natural Park, France’s first marine protected area, located off the coast of Brittany. The biological data are complemented by temperature and salinity measurements.
While this long-term dataset is highly valuable, its full potential is underutilized in the manuscript presentation due to the coarse taxonomic resolution applied (Table 3). The zooplankton classifications- limited to phylum (e.g., Cnidaria, Chaetognatha), class (e.g., Copepoda, Appendicularia), or occasionally order (e.g., Decapoda) - represent a significant reduction compared to the original EcoTaxa classifications. I would like to read -in the manuscript- some comments about this aspect. As a side note, I believe ZooScan/Ecotaxa have greater potential for taxonomic identification than what is reflected in the available dataset (Drago et al., 2025), especially when trained by an expert taxonomist.
In summary, I find the article suitable for supporting publication of the associated dataset, provided the suggested revisions are implemented. The dataset itself is valuable, demonstrating good quality and utility. My detailed review of the zooplankton component confirms its completeness, though the current organization should be improved to enhance reusability (as noted in my comments on Section 7). While the study is well-designed and generally clearly presented, several issues require attention to strengthen the manuscript for publication in ESSD.
SPECIFIC COMMENTS
- Introduction
This section provides a clear and well-structured background. I have suggested minor technical revisions in the corresponding section ("Technical Corrections").
A specific concern regards the imaging approach (Line 51). The claim that imaging methods allow for rapid processing of "large sample volumes" should be rephrased. A more accurate description would be that they enable "faster processing of more samples", which is distinct from handling larger individual volumes.
- Study site
I find no issues with this section. Both the content and presentation are clear and well-structured.
- Material and Methods
Some methodological clarifications are necessary. Please specify: (1) the criteria used for selecting sampling stations, and (2) the time required to complete all station sampling during each cruise.
The methodology for temperature measurements is unclear and contradictory. Lines 120–121 state that temperature was measured in water samples collected with Niskin bottles, stored in flasks, and analyzed on land—an unusual approach, as temperature is typically measured immediately onboard to prevent changes. However, Section 3.1.1 (line 127) mentions that temperature was measured using a WTW probe, with CTD sensors added in 2017 (line 129). This inconsistency is critical and requires thorough clarification.
The phytoplankton sampling method is not described. Additionally, it is unclear whether the shift to sampling at 15 m depth in 2016 (lines 131–132) replaced: only the near-bottom sampling, or both the sub-surface and near-bottom sampling. This ambiguity needs resolution.
There are inconsistencies regarding picoplankton analysis. The text states that "the employed methodology precluded identification and measurement of picophytoplankton" (line 166), yet Cyanobacteria (a picophytoplankton group) are later mentioned (lines 316, 320) and their abundances appear in Figures 4 and 5. This contradiction requires clarification (were Cyanobacteria quantified via a different method?).
For zooplankton collection, two key methodological details are missing: 1) was the deployed cable angle accounted for to accurately determine the sampled water layer height? 2) was the net thoroughly rinsed after retrieval to ensure all organisms were collected and none remained trapped in the mesh? These procedural details are essential for reproducibility and data reliability.
In zooplankton digitalization and identification, some details are missing:
-How many analysts processed the zooplankton samples? Were inter-calibration exercises conducted to ensure consistency, given potential operator bias during the sample fractionation and handling?
-Approximately how many organisms were analyzed per scanned sample?
-How were overlapping structures (e.g., copepod antennules) resolved during digitization?
I have a general concern regarding taxonomic resolution: why are large, distinct copepods (e.g., the Pontellidae female in Fig. 3A) only identified to the order Calanoida? Higher resolution seems feasible, since Pontellidae (as well as other calanoid families) are reported in the zooplankton dataset (Drago et al., 2025).
The review/validation of classified images was only applied to samples from 2018 onwards (lines 200–204, 256–259). What quality assurance measures were in place for pre-2018 data? This gap risks inconsistencies in the long-term dataset.
Figure 1 would benefit from an accurate revision. The map should be enhanced by 1) clear delineation of the boundaries of the Iroise MPA, 2) improved visibility of isobaths to better relate station positions to bathymetry, 3) inclusion of station B7 (mentioned in line 101 and figure caption), 4) accurate representation that transect B extends further north than transect D (line 102). Moreover, the background of temperature data should be removed as it represents results rather than methods, and the two 2016 snapshots are not representative for a long-term study.
- Database structure and analysis
In this section (lines 265-294), the phytoplankton dataset should be presented as the first one, before zooplankton (second dataset), like it is presented in the methodological section and in sections 5.2 and 5.3.
For phytoplankton, the unit should be “cells/L”, not “individuals/L” (line 289 and somewhere else).
Phytoplankton cell concentration was considered for the surface and bottom abundance (lines 289, 290). What about the samples collected only at 15 m depth since 2016 (see line 132)?
- Concluding remarks
It should be explained which were the “conditions” that were recorded to decrease in small pelagic fish (line 360).
Are there planktonic data in the Iroise Sea outside the MPA or in other Atlantic European MPAs that can be compared with the present dataset?
These datasets provide valuable opportunities for large-scale comparative studies and investigations of plankton dynamics in other MPAs, although the broad taxonomic classification may restrict some functional trait-based analyses (e.g., to size and biovolume structure).
- Data availability (Plankton datasets)
The plankton abundance data are reported with inconsistent decimal precision (1–6 decimal places for zooplankton –file .csv; 0-3 decimal places for phytoplankton – file .csv). Consistency would improve clarity.
The taxon listing in the zooplankton dataset seems disorganized without a clear logical structure. For better usability, the taxa should be organized taxonomically (from Ctenophora to Tunicata), presenting species/genera/families in alphabetical order within their respective group (e.g., within copepods, or cladocera, or tunicates, etc….).
TECHNICAL CORRECTIONS
- Introduction
The assertion in the first sentence is a well-documented and widely accepted knowledge in biological oceanography, so it does not need citation support. Moreover, the reference ‘Grigoratou’ (cited as ‘in press’ on line 33) is missing from the References section and thus inaccessible to readers.
L 35- Suggested change: ….this carbon passively through the sinking of molts, carcasses and fecal pellets, and actively through diel vertical migration…..
L36- Suggested change: At the base of aquatic…
L37- Suggested change: ….(e.g., Chavez…..
L43- Suggested change: …into plankton dynamics across…
L52,53- Remove repetition: “traditional taxonomic identification and novel trait-based analyses (Irisson et al., 2022; Orenstein et al., 2022).” is already said on line 48.
- Material and Methods
L106- The three coastal stations should be named here and Fig 1 should be cited.
L109- It should be clarified what does it mean that two stations (Douarnenez and D1) were “treater together”.
L124, 125- “is” must be replaced by “was”.
L125- it must be clarified which depth is considered “subsurface”.
L127-129, 207- Temperature should be always mentioned before salinity for coherence.
L131- Suggested change: At the transect stations….
L132- Suggested change: At costal stations…
L133- Clarification: specify if the glass of the flask was dark.
L133-135- Suggested change: The present dataset comprises 785 phytoplankton samples in total (Fig. 2). Their number varied annually………………..conditions. The sampling effort increased notably from 2010 until a peak of 97 samples in 2017 and then gradually decreased to about 50 samples in 2022.
L149- Suggested change: ….57 cm mouth diameter…
L150- Suggested change:…was deployed vertically to a maximum depth……
L154- The “1:3 sample-to-formaldehyde ratio” here reported is wrong. It should be the opposite, i.e., 1:3 formaldehyde-to-sample ratio.
L154- a verb is missing: The annual number of zooplankton samples ranged from …
L155- It should be explained what exactly means “reflecting variations in sampling strategy”.
L159- Remove “then”
L166- “measurements” should be replaced by “counts”.
L173- Suggested change: sieving the samples through a 1000 μm mesh….
L179, 180- This info is already given on line 168. Repetitions should be removed.
L196- Remove: (J) Centropagidae
L197- Instead of “Podon”, this category should be better named Podonidae, because both Podon and Pleopis may occur in coastal zooplankton samples and their images are not easily distinguishable.
- Data quality control
This section compiles information that has already been discussed in previous sections.
For example, on lines 252-254 (already on lines 159-161) and on lines 256-259 (already on lines 200-204). Repetitions should be removed.
- Database structure and analysis
L296, 297- Suggested change: Figure 4 shows the mean annual phytoplankton abundances across the sampling area, highlighting the remarkable temporal and spatial variability throughout the study period. .
L298- Suggested change: ….and 2022 in transect B, with ….
L299- Suggested change: In transect D, remarkable abundance…..
L312, 313- Suggested change: In surface waters, the phytoplankton composition showed interannual and spatial variations along both transects.
L318- Suggested change:…coast-offshore gradient.
L344- Suggested change: …at offshore stations…
- Concluding remarks
L365- Suggested change: …health in the Iroise Marine Natural Park. Beyond its ecological significance, this MPA and the Iroise Sea hold particular…..
Figure 2- In my opinion the last sentence is not appropriate in a figure caption, and it should be moved to the concluding section.
Figure 4- “Transect B” and “Transect D” should be indicated on the upper and lower panels, respectively
Figure 5- L324-326 (Each stacked bar….at that station) provide a redundant info with respect to line 324.
Table 3- Commas for decimals in the “%” column should be replaced by points.
Why some “annotation categories” are not considered in the “groups” column”? It seems that “nauplii<Crustacea”, “megalopa<Brachiura, “Ostracoda”, “Cirirpedia” - just to mention some categories as example- have not been included in the groups considered for the present dataset. If this is not the case, the names should be repeated in the “groups” column.
It should be said in the caption that the groups are listed in decreasing number of images
References
The following references seem incomplete. In some cases, the link should be provided.
Berthou et al, 2010
Chamberlain and Vanhoorne 2023
Duhamel et al., 2011
Picheral et al 2017
The key figure is well-designed, but station B7 (referenced in the text and included in Supplementary Table 1) is missing. Additionally, I recommend centering the inset map of France more effectively by shifting it slightly to the right, ensuring the full study area boundary is visible.
Supplementary Table 1
The legend for the orange and green colors used to highlight rows requires clarification. The term “classification” is ambiguous—does it refer to “taxonomic identification”? If so, this should be explicitly stated, as it is critical for dataset quality and reusability. Additionally, the specific inconsistency in classification (e.g., whether species were grouped at genus level, genera at family level, etc.) during some years should be clearly explained. For example, does orange indicate years where identifications were resolved only to higher taxonomic levels?
If the same color scheme applies to the “coastal station sampling plan”, the legend should also be included in the second sheet of the file.
Lastly, in the table caption, “Colored colors” should be corrected to “Colored cells”.
Supplementary Table 2
The profiles of turbidity, oxygen, fluorescence reported in this table are not mentioned in the text.
Supplementary Table 3
The Ecotaxa ID and the names of the projects would be more useful if accompanied by links that give access to the projects.
Citation: https://doi.org/10.5194/essd-2025-207-RC1
Data sets
Plankton and environmental monitoring dataset from the Iroise Marine Natural Park (NE Atlantic, 2010-2023) Laetitia Drago et al. https://doi.org/10.17882/105465
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