Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

Each row of the primary file of this dataset corresponds to incubation data collected while exposing an individual mussel to modified seawater.

Sampling collection details

We gathered naturally settled, adult California mussels (M. californianus between 30 and 80 mm in maximum shell length) by hand from the mid-intertidal zone of Carmet Beach, along the northern California coast. We cleaned mussels of all epibionts and external byssal threads, then transported them in buckets (< 0.5 hr transit time) to Bodega Marine Laboratory, where we acclimated individuals for seven days in flow-through seawater tables prior to subsequent experiments. 

Experiment details 

Incubations conducted according to published methods (Gazeau et al  2015). 

Seawater chemistry was controlled to target unique combinations of alkalinity (between 337 and 9584 µmol kg-1) and dissolved inorganic carbon (DIC, between 299 and 9322 µmol kg-1). Carbonate chemistry manipulations were accomplished by first acidifying seawater to an alkalinity of 0 and allowing DIC to offgas. Then alkalinity and DIC were replaced by adding a known amount of a DIC stock (sodium carbonate and sodium bicarbonate) to each incubation vessel and alkalinity adjusted with either HCl or NaOH. Additional incubations further modified salinity and calcium concentrations by the addition of known amounts of distilled water and calcium chloride.

Mussel response was quantified as the calcification rate measured with the alkalinity anomaly technique corrected for ammonia production (Gazeau et al  2015). Calcification rates are expressed as gross calcification where net calcification = gross calcification - dissolution. Dissolution rates were quantified separately and can be found in the dataset: Shell dissolution data for Mytilus californianus from March to July 2020 (OA decoupling project). A link to this dataset can be found within the Related Datasets section of this metadata page.

We calculated net calcification rates with the ammonia-corrected alkalinity anomaly technique (Gazeau et al  2015), divided by incubation duration and mussel dry tissue mass raised by a factor of 0.72 (see related dataset). The alkalinity anomaly technique builds on the observation that precipitation of CaCO3 results in an equivalent reduction in seawater [CO32-] (or reduction of [HCO3-] followed by an increase in [H+]) which contributes two equivalents of total alkalinity—simultaneous production of ammonia is the major metabolic process in mussels that can obscure this and its signal must be removed (Gazeau et al  2015).

Following the incubation, we dissected each mussel and dried it at 60 °C for at least 24 hours to obtain the dry tissue mass (excluding byssal threads) and dry shell mass of each individual mussel. We conducted additional incubations (n=87, between 3 and 9 per experiment day) without mussels throughout the trials as experimental blanks to determine background changes in alkalinity (Figure S7). We excluded from our analysis any experimental days where background alkalinity changes exceeded 5 µmol kg-1. The mean of the absolute values of alkalinity change during the incubations of these experimental blanks was 1.3 ± 1.2 µmol kg-1 (n = 72). 

We performed all computations with R statistical software, version 4.1.0. We performed carbonate system calculations using the package seacarb, using equilibrium constants from Lueker et al. We computed linear mixed models using the lmer function in in the lmertest package in R and focused on assessing likely candidate parameters as fixed factors, and mussel collection date as a random intercept to account for natural seasonal differences between cohorts. Conditional R2 was calculated with the package MuMIn. We determined parameters for non-linear fits employed to model dissolution rates by minimizing the sum of squares of model residuals using the optim function. Colors for plots were chosen from color palettes in the cmocean package in R.

- Removed special characters (e.g., periods) from column names and replaced with underscores
- Converted dates and datetimes from Excel format to %Y-%m-%d and %Y-%m-%dT%H:%M:%S, respectively
- Changed the presentation of species values from "mytilus_californianus" to "Mytilus californianus" and added AphiaID and LSID to the data file
- ph_total and ph_free columns rounded to 3 degrees of precision, and all other float numeric fields rounded to 2 degrees of precision

NSF Award Abstract:
This research is exploring the capacity of coastal organisms to cope with alterations in seawater chemistry driven by both freshwater inputs and absorption of carbon dioxide into the world's oceans (ocean acidification). The project focuses on calcification responses and behavioral impairments of shoreline animals under altered seawater chemistry, and forefronts a common mussel species (the California mussel), and a common snail (the black turban snail), each abundant on rocky shores along the west coast of North America. The target species operate as exemplar organisms for characterizing the responses of marine invertebrates more generally. Methods involve experimental decoupling of multiple components of the carbonate system of seawater to isolate drivers that are difficult to separate otherwise. Broader impacts include transfer of scientific information to policy-makers, including legislators, as well as training and skill-set development of future generations of scientists and citizens. One Ph.D. student is supported, as are UC Davis undergraduates conducting mentored research. The project also provides research internships for undergraduates from a local community college (Santa Rosa Junior College), many of whom are from underrepresented groups. The latter project component substantially bolsters an ongoing program at Bodega Marine Laboratory that includes efforts in diversity, equity, and inclusion. Data and interpretations from the project are feeding into an existing educational program that links to local K-12 schools and reaches ~10,000 members of the public each year.

Overall, the research of the project is dissecting drivers of calcification and behavioral disruption in key shoreline invertebrates, across present-day and future carbonate system conditions appropriate to coastal marine environments. Efforts are exploring the extent to which calcification depends on one versus multiple parameters of the seawater carbonate system. In particular, existing conceptual models emphasize the importance of calcium carbonate saturation state (Ω) and/or the ratio of bicarbonate to hydrogen ion concentrations ([HCO3-]/[H+]), and the project is examining these mechanisms as well as the possibility that more than one driver acts simultaneously. It is doing so both in bivalves and in gastropods to test for generality across mollusks. The project is additionally examining whether pH is the only carbonate system factor contributing to known patterns of behavioral impairment in marine invertebrates. Leading explanations for debilitating behaviors induced by ocean acidification involve altered ion channel function, but discussion in the literature continues, and studies that explicitly decouple the carbonate system are necessary.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.