DOI: 10.14466/CefasDataHub.161

Description

Mesozooplankton abundance data gathered as part of an ongoing annual autumn pelagic survey in the English Channel, Celtic Sea and Bristol Channel, with data currently available from 2017-2021. Samples were obtained using twin ringnet deployments at set stations and subsequently processed back at the lab using ZooScan image analysis. Count abundances from semi-automatic image classifications on EcoTaxa are then converted into abundances per m3 using estimates of filtered volume from flowmeter readings. The current dataset comprises zooplankton results specifically from the PELTIC (Integrated Pelagic ecosystem survey in the Western Channel and Celtic Sea) survey series, which has expanded the collection of pelagic data from the core regions sampled in the POSEIDON survey series which ran between 2012-2016. Since autumn 2017, samples have continued to be collected with twin ringnet deployments and KC flowmeter attachments onboard the RV Cefas Endeavour, with image analysis conducted on those obtained using an 80µm ringnet of 0.5m diameter. Deployments are made at set station locations along transect lines which continue to span the area between the Bristol Channel to the south of Wales and eastern Celtic Sea to the western side of the English Channel. In addition to this, the surveys expanded their focus from purely UK territorial waters around the Cornish Peninsula to include French waters off the western English Channel. In 2020, this was extended further to include Cardigan Bay to the west of Wales. The transect lines stations have been located within have been designed with their spacing and orientation across the prevailing bathymetry of the area.

Preserved samples were sent back to the Plankton Lab at the Cefas Lowestoft Laboratory and thereafter split into fractions and prepped for image analysis using ZooScan. To obtain a representative subsample, a minimum threshold of 200 zooplankton specimens needed to be captured in the images where possible from each sample, with rescans conducted as necessary. Object images processed from the sample were subsequently imported into the project image library within the EcoTaxa web application.

Once uploaded into EcoTaxa, scanned objects from each sample were predicted into taxa categories with the provision of a learning set to aid automatic image sorting using Random Forest algorithms. These predicted classifications are validated afterward by an experienced zooplankton taxonomist and the metadata downloaded with the taxa counts. Filtered volume estimates were obtained based on calculations using flowmeter rotor revolution counts recorded for each station. Objects captured in images were separated into zooplankton taxa and detritus groups and abundances estimated in terms of per m3, using counts and filtered volume and raising factor calculations based on the sample fractions used. An agreed subset of the data may be selected for quality control checks by a second experienced taxonomist, ensuring quality control in the image classifications.

Contributors

Almeida, Nevena / Close, Hayden / Pettigrew, James / Cefas plankton team / Cefas PELTIC crew on R.V. Cefas Endeavour

Subject

Pelagic / Zooplankton

Start Date

25/09/2017

End Date

17/03/2023

Year Published

2025

Version

1

Citation

Almeida et al. (2025). Mesozooplankton abundance in the Bristol Channel, Celtic Sea and English Channel 2017-2023. Cefas, UK. V1. doi: https://doi.org/10.14466/CefasDataHub.161

Rights List

Open Government Licence

DOI

10.14466/CefasDataHub.161