Dataset: Lab incubations of mussels (Mytilus californianus) examining the influence of periostracum cover and pH on external shell dissolution at Marshall Gulch Beach, CA from August 2021 to March 2022

ValidatedFinal no updates expectedDOI: 10.26008/1912/bco-dmo.935476.1Version 1 (2024-12-28)Dataset Type:experimentalDataset Type:Other Field Results

Principal Investigator: Brian Gaylord (University of California - Davis: Bodega Marine Laboratory)

Student: Alisha Saley (University of California - Davis: Bodega Marine Laboratory)

BCO-DMO Data Manager: Lynne M. Merchant (Woods Hole Oceanographic Institution)


Project: Invertebrate calcification and behavior in seawater of decoupled carbonate chemistry (OA decoupling)


Abstract

Reductions to seawater pH challenge the shell integrity of marine calcifiers. Many molluscs have an external organic layer (the periostracum) that limits exposure of underlying shell to the external environment, which could potentially help combat shell dissolution under corrosive seawater conditions. We tested this possibility in adult California mussels, Mytilus californianus. We quantified shell dissolution rates as a function of periostracum cover across three levels of reduced pH (7.7, 7.5,...

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Overview: Trials examining rates of shell dissolution were conducted in seawater of differing carbonate system conditions, using dead shells of sacrificed adult California M. californianus mussel individuals. The relationship between percent surface cover of periostracum and shell dissolution rate under contemporary but chemically stressful seawater conditions was examined. For the current study, adult mussels (42 - 64 mm in length) were collected from Marshall Gulch, California (38.369738 °N, -123.073921 °W) between August 2021 and March 2022 and transported immediately to the University of California Davis’ Bodega Marine Laboratory (< 30 min distance), in Bodega Bay, California. Mussels were held in filtered, flow-through seawater and fed ad libitum until used in experiments.

 

Shell preparation and periostracum cover measurements: The extent of intact periostracum coverage was determined for one of two valves of each M. californianus mussel. We photographed individual valves with a 12.2-megapixel digital camera (Google Pixel 4a) and then quantified the area of valve covered by periostracum and total valve surface area using ImageJ (software version 1.52a) calibrated to a scale bar. Because we were interested in the effects of the periostracum in protecting the exterior surface of the shell, we sealed the inner, nacre layer of the shell with silicone (Loctite marine silicone sealant) to prevent its contact with seawater.

 

Seawater manipulation: We used two techniques to establish the different pH treatments employed in our experiments. In the dissolution incubations conducted at pH = 7.5 (n = 49), we modified seawater chemistry using a standard mass-flow control system, bubbling gas of a fixed partial pressure of CO2 directly into filtered seawater via flow-through sumps. In dissolution trials involving pH = 7.7 (n = 9) and 7.4 (n = 16), we employed an alternative, but equivalent, approach to manipulating seawater pH where we used direct chemical modification to the seawater carbonate system via equimolar additions of 1 M sodium bicarbonate (NaHCO3) and 1 M hydrochloric acid (HCl). Both methods of seawater manipulation result in an increase of dissolved inorganic carbon (DIC) and reduction of seawater pH without changing total alkalinity (TA).

 

Dissolution Incubations and Analysis: Following determination of percent cover of periostracum, we incubated each mussel valve in a sealed 250 mL Nalgene bottle filled with modified seawater for 48 hours in a temperature-controlled room, recording seawater properties in each bottle before and at the end of each incubation, including temperature, salinity, and pH (Yellow Springs Instruments Professional Plus Sonde). YSI sonde pH values were calibrated to the total scale based on pH spectrophotometric measurements of m-cresol dye absorbance at the incubation temperature. Incubation bottles were agitated gently once every 8 hours over the course of the incubations to reduce the establishment of strong chemical gradients of their fluid contents. We took discrete seawater samples at the onset and end of each incubation for determination of total alkalinity concentration (TA); these “before-after” measurements of TA enabled quantification of the increase in alkalinity within each bottle over the duration of the incubation, and thereby the rate of dissolution of calcium carbonate (CaCO3) shell material for individual valves of known periostracum cover. Shell dissolution rates were quantified using standard alkalinity anomaly techniques (analyzing seawater samples in triplicate and selecting median TA for dissolution quantification), which relate calcium carbonate shell loss to an increase in the total alkalinity (TA) of surrounding seawater, per unit time. Across the dissolution trials, control incubations (15% of daily sample size) of modified seawater were conducted to verify minimal background changes in TA.


Related Datasets

IsRelatedTo

Dataset: Field measurements of periostracum cover from focal population
Relationship Description: Mussels from the same population as Dataset 1 & Dataset 2 with field measurements of periostracum cover of mussels
Saley, A., Gaylord, B. (2024) Field measurements of periostracum cover of mussels (Mytilus californianus) from focal population at Marshall Gulch Beach, CA in July and August 2022. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2024-12-26 doi:10.26008/1912/bco-dmo.935484.1
IsRelatedTo

Dataset: Mussel lab incubations: simulated periostracum abrasion (effect on shell dissolution)
Relationship Description: Mussels from the same population as Dataset 1 & Dataset 3 examining the influence of simulated abrasion of periostracum on external shell dissolution
Saley, A., Gaylord, B. (2024) Lab incubations of mussels (Mytilus californianus) examining the influence of simulated abrasion of periostracum on external shell dissolution at Marshall Gulch Beach, CA from August 2021 to March 2022. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2024-12-28 doi:10.26008/1912/bco-dmo.935480.1

Related Publications

Software

R Core Team (2023). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/
Software

Schneider, C. A., Rasband, W. S., & Eliceiri, K. W. (2012). NIH Image to ImageJ: 25 years of image analysis. Nature Methods, 9(7), 671–675. https://doi.org/10.1038/nmeth.2089