Table of Contents

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

Forty Strongylocentrotus purpuratus were collected from kelp forests between 2.2 – 8.8 meters from Carpinteria Reef in the Santa Barbara Channel, California in June 2022. Before spawning, individuals were held at 13°C for 4 weeks at UC Davis Bodega Marine Laboratory and were fed 20 grams of Urchinomics Inc. kelp-based pelleted food every other day.

A homogeneous pool of fertilized embryos were assigned to temperature treatments. Spawning was induced by injecting 1–2 mL of 0.5 M KCl. Female urchins were placed upside down over 250 mL beakers filled with filtered to 0.1 µm seawater (FSW) at ambient temperature. Eggs were allowed to collect at the bottom of beakers. Sperm was collected dry from the aboral surface and placed on ice in 2.0 mL microcentrifuge tubes until use. Gamete quality was visually inspected with eggs assessed for shape, color, and uniform size and sperm for motility. Eggs from four females were pooled and rinsed before being fertilized by sperm from four males. Approximately equal proportions of gametes from each individual within each sex were represented. Successful fertilization was determined by 95% of eggs having a fertilization envelope with no polyspermy. Fertilized eggs were rinsed three times with FSW to remove excess sperm to prevent polyspermy. Approximately 2800 embryos (concentration of ~5.5 embryos mL^-1) were placed in each 500 mL glass bottles filled with FSW and placed on roller tables to suspend larvae (Karelitz et al. 2020).

Roller agitation tables were constructed to provide water movement for larval sea urchin cultures. Rollers on free moving axles kept larval culture bottles rotating to prevent larvae from settling to the bottom. Bottles were partially submerged in water baths heated or chilled using Heater/Chillers (TECO US Inc. TK-500) to maintain target temperatures. Embryos were initially stocked in bottles with ambient temperature (16°C) FSW to minimize temperature shock but immediately placed into water baths to allow embryos to acclimate to target temperatures. Each of the 24 temperature x food treatments had four replicate bottles for a total of 96 bottles. Larvae were fed daily starting at 4 days post-fertilization (when larvae were observed to be competent to feed) and water changes and feeding were conducted every 2 days.

Larval samples were collected 4, 9, and 15 days post-fertilization and fixed in 10% PBS buffered formalin for morphometric analyses. Samples were collected before feeding to minimize influence of algae on stomach measurements. Fixed larvae were then photographed using an Olympus BX41 compound microscope with a Nikon 3400 DSLR camera at 4X magnification and postoral arm length, body length, stomach length/height were measured in 20 randomly selected larvae from each sample using ImageJ, version 1.53t (Schneider et al. 2012). Metamorphic competency was determined when >50% of larvae exhibited tube feet and adhered to the bottle.

- Imported "larvae_measurements_scaled.csv" into the BCO-DMO system
- Exported file as "963425_v1_larval_morphometrics_warming_food.csv"

NSF Award Abstract:
Rapid and extreme warming events such as El Niño and marine heatwaves have had ecological and economic impacts on nearshore marine ecosystems. These impacts include reductions in biomass and collapses in commercial fisheries. For many species, population booms and busts are controlled by shifts in reproduction and juvenile dispersal related to warmer temperatures and ocean circulation. However, how population fluctuations are shaped by interacting processes that control adult reproduction and larval survival remains unclear. Marine heatwaves often accompany major disruptions in ocean circulation, which can affect survival and the distribution of species that produce free-floating, planktonic larvae. As a result, species can be impacted directly by temperature effects on organismal reproduction and survival, and indirectly by shifts in ocean circulation that affect larval success. This project is examining how the joint effects of temperature and ocean circulation are controlling populations of purple sea urchins (Strongylocentrotus purpuratus). To address project objectives, the team is developing oceanographic models to predict dispersal of planktonic larvae in combination with controlled experiments on adult reproductive success. This project is advancing the understanding of how ecologically important species respond to ocean temperature and circulation, which are forecast to shift under future climate change scenarios. Broader impacts of the project include training of students and post-docs in STEM and educational outreach. Curriculum development and implementation is occurring in collaboration with existing K-12 outreach programs that focus on underserved communities and under-represented groups. The goal is to empower the next generation of scientists to use integrative approaches to predict ecological consequences of climate change.

Purple sea urchins are an ideal species for studying the coupled impacts of warming and ocean circulation on recruitment and survival given a wealth of ecological and organismal data. The species has a mapped genome, can be transported large distances as larvae by ocean currents, and larval abundances in California exhibit orders of magnitude variation with heatwaves and El Niño fluctuations. To quantify the processes that shape spatial and temporal variability in larval supply, researchers are applying a novel combination of biophysical modeling, experiments and statistical modeling of long-term, high-resolution data on larval settlement across the Southern California Bight (SCB). Research module 1 is quantifying spatial and temporal patterns of larval transport using a 3D-biophysical model of the SCB. The model is testing how interactions among historical changes in ocean circulation and temperature, larval life history, and larval behavioral traits affect variation in larval supply in space and time. Research module 2 is focused on how temperature could affect spatial and temporal variation in egg production. Experiments are characterizing reproductive thermal performance curves and quantifying how these vary among populations and organismal history. A novel assay is assessing epigenetic regulation of gene expression associated with performance curves. Finally, Module 3 will integrate mechanistic models from Modules 1 and 2 to statistically assess their ability to explain spatial and temporal trends in a nearly three-decade dataset of larval settlement from six sites in the SCB. This is one of the first studies that integrates models of larval transport, reproductive performance and settlement data to empirically test how physical and biological processes affect local recruitment patterns in complex marine meta-populations.

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.