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

To measure oxygen consumption, individual larvae were placed within chambers of a closed microplate reader system that uses optical fluorescence to measure oxygen concentration (PreSens, Germany). After a 5-minute acclimation period, the change in dissolved oxygen was measured every 30 seconds over 20 minutess. The microplate reader had 2 blocks of 24 wells.

In Experiment 1 (see Related Datasets), 20 fish larvae were measured per run. In Experiment 2, 40 fish were measured per run. For all chambers, the investigators ran a linear regression of oxygen concentration on time (n = 40 measurements). The respiration rate for each fish (VO2, expressed in milligrams of O2 per individual per hour (mg O2 ind-1 h-1)) was calculated as:

VO2 = V (S – B)

where S is the slope describing the change in O2 concentration for individual chambers with the fish,
B is the average slope for the four chambers with no fish (both in units of milligrams O2 per liter per hour (mg O2 L-1 h-1) and inferred to be per individual since each well held only one larvae), and
V is the volume of water in the chamber (1.500 × 10-3 liters (L)).

Note the displacement volume of grunion larvae in this study was <2.5 × 10-6 L and thus negligible in these calculations. Fish were assigned to each chamber at random, and larvae were used once in the respiration measurements and then humanely euthanized.

To describe the duration and magnitude of the Specific Dynamic Action (SDA) response, the investigators first calculated delta.VO2, the difference between the mean rates of oxygen consumption for the pair of fed and non-fed larvae.

These data were summarized by Siegfried and Johnson (2023) and plotted in figures 1, 3, and 5.

For all chambers, the investigators ran a linear regression of oxygen concentration on time to obtain the respiration rate of each fish. Respiration rates, referred to as VO2, were expressed in mg O2 ind-1 h-1. Average VO2 values were then calculated for groups of fed and non-fed larvae of the same age and average size, and experiencing the same seawater conditions. The difference in average VO2 values (referred to as delta VO2) provides a measure of the average energetic cost of digestion at a single time post feeding.

- Imported original files "Expt 2a summary file.xlsx" and "Expt 2b summary file.xlsx" into the BCO-DMO system.
- Concatenated the data from both files into a single dataset.
- Renamed fields to comply with BCO-DMO naming conventions.
- Marked "#VALUE!" as a missing data value (missing data are blank/empty in the final CSV file).
- Saved the final file as "924613_v1_sda_expts2.csv".

NSF Award Abstract:
Ongoing increases in atmospheric carbon dioxide have changed the acidity of the ocean, which could affect growth and survival of marine organisms. For fishes, the projected decreases in ocean pH could cause severe increases in mortality during the larval and juvenile stages. In turn, these effects may lead to major reductions in the numbers and size of adult fish, loss of fishery yields, and a loss of income for people whose livelihoods depend on the sea. However, if species can genetically adapt to become more tolerant of ocean acidification conditions, then evolutionary responses may play a role in the long-term dynamics of populations. This project examines how ocean acidification may alter patterns of natural selection for two species of fish in a set of breeding experiments that test tolerances to low pH of different genetic lineages. These experiments are determining the genetic capacity present in these populations to adapt to future conditions and offset the negative effects of changes in seawater chemistry. Broader impacts of this project include the training of two graduate students and at least nine undergraduates at an institution that is recognized as both a Hispanic Serving Institution and an Asian American, Native American, and Pacific Islander Serving Institution, and is one of the most culturally diverse universities in the world. Additional broader impacts include public outreach activities through local aquaria and regular meetings with local city and beach managers. Presentations focus on long-term population predictions of two fish species that are culturally and economically valuable.

The goal of the project is to understand how ocean acidification will affect both offspring survival and maternal fitness. The project combines quantitative genetic studies with laboratory experiments and population modeling to examine tradeoffs between fecundity and offspring survival under present and predicted ocean acidification conditions. Breeding experiments are assessing the natural genetic variance underlying larval traits. The experimental protocol includes testing for parental effects by exposing adult fishes to high-pCO2 seawater during gametogenesis and measuring the survival of offspring experiencing conditions of ocean acidification. The capacity for genetic change in response to changes in ocean carbonate chemistry is being investigated through mathematical models. Quantitative evaluation includes 1) how selection operates as seawater chemistry changes; 2) levels of genetic (co)variation underlying larval traits; 3) whether non-genetic inheritance may affect responses to ocean acidification; and 4) whether evolutionary changes are fast enough to affect the dynamics of populations over relevant timeframes (e.g., 10-100 years). The project is developing a genetic model for describing how changes in ocean chemistry are driving natural selection.

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.