Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Project Information
• Funding

Data collected from a laboratory water column experiment to investigate the behavioral effects of ocean acidification on sand dollar larvae (Dendraster excentricus).

Spawning and fertilization:

We collected adult sand dollars (D. excentricus) from Semiahmoo Bay, WA, on July 7, 2017, and maintained them in 14°C continuous flowing seawater at the Shannon Point Marine Center. On July 12, 2017, we induced twelve individuals to spawn by injecting 1-mL of 0.5-M KCl into the coelom following methods outlined by Strathmann (1987).  We then collected and mixed concentrated gametes of four males and four females for fertilization. We added five drops of sperm to 500-mL of filtered seawater and 5-mL of eggs. We placed the fertilized eggs in 12°C incubator and bubbled them with ambient pCO2 condition for 12-hrs before dividing the embryos into pCO2 treatment conditions before gastrulation.

Larval Rearing

We reared D. excentricus larvae (2 individuals mL-1) at 12°C in eight 3-L jars that were individually bubbled with CO2 to achieve four replicates of ambient (400ppm) and acidic (1500ppm) pCO2 conditions. Each jar of larvae received a water change with pre-equilibrated 0.35-m filtered ambient and acidic seawater and fed the larvae D. tertiolecta (6,000 cells ml-1) daily. Pre-equilibrated ambient and acidic water was held in tanks within the same 12°C incubator as the rearing jars.

Experimental Design

We conducted two behavioral experiments; one when the larvae were 4-arm pleutei and one when the larvae were 6-armed pleutei.

To measure the effect of pH conditions on the vertical distribution of larvae we established three experimental pycnocline treatments within clear plexiglass water columns (2.5cm x 2.5cm x 30cm): (1) ambient water (400ppm) in the top layer and acidic water in the bottom layer (1500ppm), (2) ambient water (400ppm) in both top and bottom layers, and (3) acidic water (1500ppm) in the top layer and ambient water (400ppm) in the bottom layer. Each water layer was 60-mL of water and filled the column 10-cm high, so when each experimental treatment was established it filled the column to 20-cm. We established the experimental treatments by increasing the density of seawater in the bottom layer by 0.003-0.005 g ml-1 using PercollTM GE Healthcare (Podolsky & Emlet 1993). Experimental treatment water was kept at 12°C and pre-equilibrated to the desired pCO2 level and density. We also included blue food coloring (1 drop per 100-mL) to the dense bottom layer to more easily visualize the density layers while establishing experimental treatments. We set-up four replicate columns for each experimental treatment making twelve columns total per experiment.

Columns were positioned in a randomized order along the table of a walk-in incubator set to 12°C. Once columns were in position and treatments were established, we carefully injected 150 larvae by syringe into the bottom 2-cm of each column with no more than 2-mL of their culture water. Larvae were given 10 minutes in darkness to acclimate before we performed the first count of vertical positions of larvae in each water column. At 30 minutes of acclimation, we performed a second count of vertical positions of larvae in each column. For each larval count, we used a small hand-held flashlight and counted by eye the number of larvae occupying each centimeter of the water column beginning at the bottom and moving up to the top. We did these counts in the dark, so only one column received direct light from our small flashlight at a time to reduce the influence of light on the larvae’s behavior.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- reformatted date from m/d/yy to yyyy-mm-dd

In the face of climate change, future distribution of animals will depend not only on whether they adjust to new conditions in their current habitat, but also on whether a species can spread to suitable locations in a changing habitat landscape. In the ocean, where most species have tiny drifting larval stages, dispersal between habitats is impacted by more than just ocean currents alone; the swimming behavior of larvae, the flow environment the larvae encounter, and the length of time the larvae spend in the water column all interact to impact the distance and direction of larval dispersal. The effects of climate change, especially ocean acidification, are already evident in shellfish species along the Pacific coast, where hatchery managers have noticed shellfish cultures with 'lazy larvae syndrome.' Under conditions of increased acidification, these 'lazy larvae' simply stop swimming; yet, larval swimming behavior is rarely incorporated into studies of ocean acidification. Furthermore, how ocean warming interacts with the effects of acidification on larvae and their swimming behaviors remains unexplored; indeed, warming could reverse 'lazy larvae syndrome.' This project uses a combination of manipulative laboratory experiments, computer modeling, and a real case study to examine whether the impacts of ocean warming and acidification on individual larvae may affect the distribution and restoration of populations of native oysters in the Salish Sea. The project will tightly couple research with undergraduate education at Western Washington University, a primarily undergraduate university, by employing student researchers, incorporating materials into undergraduate courses, and pairing marine science student interns with art student interns to develop art projects aimed at communicating the effects of climate change to public audiences

As studies of the effects of climate stress in the marine environment progress, impacts on individual-level performance must be placed in a larger ecological context. While future climate-induced circulation changes certainly will affect larval dispersal, the effects of climate-change stressors on individual larval traits alone may have equally important impacts, significantly altering larval transport and, ultimately, species distribution. This study will experimentally examine the relationship between combined climate stressors (warming and acidification) on planktonic larval duration, morphology, and swimming behavior; create models to generate testable hypotheses about the effects of these factors on larval dispersal that can be applied across systems; and, finally, use a bio-physically coupled larval transport model to examine whether climate-impacted larvae may affect the distribution and restoration of populations of native oysters in the Salish Sea.