DOI: 10.5285/465b8a1a-53fb-4ebc-b389-57cd0fdbade9
title: Biometric and oocyte size measurements for the bivalves Astarte crenata and Bathyarca glacialis from the Western Barents Sea under ambient and near-future climate change conditions.

description: Quantification of interactive effects of ocean warming and ocean acidification based on near-future climate change projections on morphometrics and oocyte size of benthic invertebrates (the bivalves Astarte crenata and Bathyarca glacialis) from the Western Barents Sea. Supported by The Changing Arctic Ocean Seafloor (ChAOS) - how changing sea ice conditions impact biological communities, biogeochemical processes and ecosystems project (NE/N015894/1 and NE/P006426/1, 2017-2021), Natural Environment Research Council (NERC) in the UK.
description: Specimens were collected from each of 1 station in 2017 (B13) and 2 stations in 2018 (B16 and B17) during two consecutive cruises (RRS James Clark Ross: JR16006, 30th June to 8th August 2017; JR17007: 10th July to 5th August, 2018) following a transect along the 30°E meridian. At each station similar-sized specimens of the infaunal bivalves Astarte crenata and Bathyarca glacialis were obtained by Agassiz trawl. Surficial sediment &lt;10 cm deep was collected using SMBA box cores, sieved to remove macrofauna (500 µm mesh), and homogenised by stirring. Both infaunal bivalves and sediment were maintained under aerated seawater and returned to the Biodiversity and Ecosystem Futures Facility, University of Southampton at ambient temperature (1.5 + 1°C). Ten centimetres of homogenised sediment were transferred to transparent acrylic aquaria (internal dimensions, LWH: 20 x 20 x 34 cm) and overlain with ~8 L (20cm depth) surface seawater (salinity, ~34). Aquaria were maintained in the dark at ambient conditions (1-2 °C and ~400 ppm [CO2]), and randomly distributed between two insulated fibreglass seawater baths (LWH: 1.2 x 1.2 x 0.8m, Tanks Direct, UK). Three B. glacialis were introduced to each of twelve aquaria (n = 36; ambient 18, future 18) and six A.crenata were introduced to each of ten aquaria (n = 60; 30 ambient, 30 future). After a 30-day acclimation period to aquarium conditions, temperature and [CO2] were manually adjusted (1 °C and ~100 ppm CO2 week -1) to achieve near-future treatment conditions (3-5 °C and ~550 ppm [CO2]). We periodically measured pH, temperature and salinity and total alkalinity. The bivalves were fed ad libitum three time per week (100 ml cultured live Isochrysis sp., Tetraselmis sp., and Phaeodactylum sp.), and overlying water exchanged weekly. Experiments were run for 120 days (B. glacialis, 21//11/2017-20/03/2018) or 135 days (A. crenata, 08/10/2018-19/02/2019) after which animals were removed and fixed in 4 neutral buffered formaldehyde. Morphology: Biometric measurements (maximum shell height, shell length, shell width and weight) were determined using a digital calliper (± 0.01mm), and bivalves within a specific size range selected for histological analyses (A. crenata 25-30 mm shell length - n = 37 [19 ambient, 18 future]; B. glacialis 20-25 mm shell length - n = 24 [12 ambient, 12 future]). N.B., Biometric measurements for all A. crenata (n = 59, including those selected for histological analyses,) less one damaged individual are contained in the attached spreadsheet (Astarte_Morphology.CSV file). However, owed to several individuals being pooled in sample jars at the end of the experiment, only biometric measurements for specimens that could be individually identified (and selected for histological analyses) are contained in the attached spreadsheet (Bathyarca_Morphology.CSV file). Oocyte size: Soft tissue of each specimen was processed using standard protocols for wax histology and stained using haematoxylin Z and the counterstain eosin. The oocyte size distribution of 100 oocytes per female was measured, where the size of each oocyte was standardised to the diameter of a circle with an equal aggregate cross-sectional area to the two-dimensional section of the imaged oocyte (i.e., Equivalent Circular Diameter (ECD)). N.B. Oocyte size (ECD) was only measured for females where oocytes were complete and/or present in a sufficient number (100+) to ensure robust quantitative analysis. The number of pixels equivalent to each ECD measurement (i.e., 'Pixel_diameter') is also indicated in the attached spreadsheets (Astarte_Oocyte_Size.CSV file and Bathyarca_Oocyte_Size.CSV file). Variability in the quality of tissue preservation rendered the oocytes of some females not measurable. Full descriptions and additional information provided in Reed et al. 2021 Frontiers in Marine Science in main manuscript and supplementary information.
description: Resolution: Biometric measurements (i.e., shell length, shell height and tumidity (width) to two decimal places. Wet weight to four decimal places. Oocyte Equivalent Circular Diameter to two decimal places. Instrumentation: Mettler-Toledo InLab Expert Pro temperature-pH combination electrode Mettler-Toledo InLab 737 IP67 temperature-conductivity combination electrode Digital vernier calliper Balance (+/-0.000g) Rotary microtome Nikon D5000 digital SLR camera Olympus BHS (BH-2) stereomicroscope
description: Standard protocols were followed and data entry double checked by independent person.