Transgenerational epigenetic effects of climate stressors on oysters
This is a draft research plan for a project I could execute starting winter 2016/2017.
Research Concept: a quick look
A rapidly broadening body of literature indicates that ocean acidification negatively affects many marine invertebrates, particuarly at fertilization and during larval stages of development. This research has informed oyster aquaculture, and as such many hatcheries treat their seawater to maintain a pH at historically ambient levels (approximlately 8.1). While an effective short-term solution for hatchery produced oysters, this feasible in the long-term as extreme low pH events increase in frequency, and other life stages ,such as juvenile seed and adult broodstock that are routinely reared in natural conditions, remain at risk. Additionally, wild oysters do not have the luxury of treated water. Buffering seawater buys us time, but could hatchery managers also select for OA-resilient oysters? Do oyster even have the mechanisms to rapidly adapt?
The oyster genome has been shown to be highly polymporchic, and Zang et al. (2012) found the C. gigas genome to contain “an extensive set of genes [that respond to] environmental stress.” Paired with the Sweepstakes Reproductive Success hypothesis (e.g. Hedgecock & Pudovkin, 2011), the oyster genome may contain the adaptive capacity for response, rapid natural selection, or both. Examining the epigenetic response of broodstock oysters to OA, and subsequent transgenerational epigenetic inheritence, could uncover the underlying mechanisms of oyster adaptability, and could inform hatchery breeding programs to select for OA-resilient oysters, or induce an immune-like response by exposing broodstock to future climate conditions. Similarly, understanding the adaptation capacity (or lack-thereof) of wild populations to low pH and/or high winter temperatures could inform resource managers and restoration groups’ long-term action plans.
Ocean acidificaiton is driven by increases in atmospheric CO2, and is tightly coupled with atmospheric and ocean warming. As such, temperature increase must also be considered in research that predicts species resiliency. Ostrea lurida, for example, is a protandrous sequential hermaphrodite and begins the spawning season once water temperature reaches approximately 14.5°C to 16°C. In order to accurately predict future community-level trends of oysters, further research must explore responses to simultaneous stresses of OA and high temperatures.
In response to these data gaps, this proposal seeks to elucidate the interactive effects of dissolved CO2 and elevated temperature on differential gene expression & transgenerational epigenetic inheritence in two oyster species, Crassostrea gigas an Ostrea lurida.
Experimental Plan Overview
- Broodstock conditioning in treatment conditions: ~4 months, December 2016-March 2017
- Spawning & larval care in treatment conditions: 2-4 weeks, April 2017
- Setting and rearing in hatchery: ~2-4 weeks May 2017
- Housing seed off dock: ~10 months June 2017-April 2018
- 650 mature F1 Ostrea lurida from same pooled ‘family’
- 650 mature Crassostrea gigas from same genetic line
Need 2 replicates of each of the below, with independent water source for the replicates
Exact larval rearing temperatures & are TBD
- Treatment #1: pH 8.1 (~400ppm) @ ~8°C
- Treatment #2: pH 8.1 (~400ppm) @ ~12°C
- Treatment #3: pH 7.7 (~1000pm) @ ~8°C
- Treatment #4: pH 7.7 (~1000pm) @ ~12°C
- Larval rearing O. lurida:
- Treatment #1: pH 8.1 (~400ppm) @ ~16°C
- Treatment #2: pH 8.1 (~400ppm) @ ~20°C
- Treatment #3: pH 7.7 (~1000pm) @ ~16°C
- Treatment #4: pH 7.7 (~1000pm) @ ~20°C
- Larval rearing C. gigas:
- Treatment #1: pH 8.1 (~400ppm) @ ~24°C
- Treatment #2: pH 8.1 (~400ppm) @ ~28°C
- Treatment #3: pH 7.7 (~1000pm) @ ~24°C
- Treatment #4: pH 7.7 (~1000pm) @ ~28°C