Carryover effects of temperature and pCO₂ across multiple Olympia oyster populations

Abstract

6Predicting how populations will respond to ocean change across generations is critical to 7 effective conservation of marine species. One emerging factor is the influence of parental 8 exposures on offspring phenotype, known as intergenerational carryover effects. Parental 9 exposure may deliver beneficial or detrimental characteristics to offspring that can influence 10 larval recruitment patterns, thus shaping how populations and community structure respond to 11 ocean change. Impacts of adult exposure to elevated winter temperature and pCO2 on 12 reproduction and offspring viability were examined in the Olympia oyster (Ostrea lurida) using 13 three populations of adult, hatchery-reared O. lurida, plus an additional cohort spawned from one 14 of the populations. Oysters were sequentially exposed to elevated temperature (+4°C, at 10°C), 15 followed by elevated pCO2 (+2204 µatm, at 3045 µatm) during winter months. Male gametes 16 were more developed after elevated temperature exposure and less developed after high pCO2 17 exposure, but there was no impact on female gametes or sex ratios. Oysters previously exposed 18 to elevated winter temperature released larvae earlier, regardless of pCO2 exposure. Those 19 exposed to elevated winter temperature as a sole treatment released more larvae on a daily basis, 20 but when also exposed to high pCO2 there was no effect. These combined results indicate that 21 elevated winter temperature accelerates O. lurida spermatogenesis, resulting in earlier larval 22 release and increased production, with elevated pCO2 exposure negating effects of elevated 23 temperature. Altered recruitment patterns may therefore follow warmer winters due to 24 precocious spawning, but these effects may be masked by coincidental high pCO2. Offspring 25 were reared in common conditions for one year, then deployed for three months in four estuarine 26 bays with distinct environmental conditions. Offspring of parents exposed to elevated pCO2 had 27 Spencer et al. preprint September 2019 3 higher survival rates in two of the four bays. This carryover effect demonstrates that parental 28 conditions can have substantial ecologically relevant impacts that should be considered when 29 predicting impacts of environmental change. Furthermore, Olympia oysters may be more 30 resilient in certain environments when progenitors are pre-conditioned in stressful conditions. 31Combined with other recent studies, our work suggests that the Olympia may be more equipped 32 than other oysters for the challenge of a changing ocean. 33

Latent effects of winter warming on Olympia oyster reproduction and larval viability

“…4.1 Effects of overwintering temperature and algal density 4.1.1 Larval production Larval production was unaffected by winter temperature and algal density, regardless of exposure time (7 or 12 weeks). The results are in contrast with a complementary study, Spencer et al (2020), in which elevated temperature exposure prior to spawning resulted in more larvae. The present study specifically expands Spencer et al (2020), to use a new O. lurida population collected from the wild rather than oysters that were bred in captivity.…”

“…The results are in contrast with a complementary study, Spencer et al (2020), in which elevated temperature exposure prior to spawning resulted in more larvae. The present study specifically expands Spencer et al (2020), to use a new O. lurida population collected from the wild rather than oysters that were bred in captivity. The response of O. lurida reproduction to elevated winter temperature may be conditional upon gonad stage prior to treatment, and population-specific reproductive traits (Barber, Ford, and Wargo 1991;Silliman, Bowyer, and Roberts 2018) .…”

“…For instance, in this study the percentage of female broodstock was unusually high upon collection (63%), and many already contained late-stage oocytes (55% of females). In comparison, only 28% of all oysters sampled in Spencer et al (2020) were female, 33% of which contained late-stage oocytes. Oysters that enter the winter with late-stage oocytes may be less influenced by winter conditions, and may require less time and energy for maturation in the spring.…”

“…Here, we find evidence for gonad activity at low temperatures based on gradual changes in gonad stage and sex throughout the winter (Figure 2). Spencer et al ( 2020 )…”

Carryover effects of temperature and pCO2 across multiple Olympia oyster populations

“…Departures from da Silva's stage 0, stage 4 (partially spawned), and stage 5 (fully spawned/resorbing) were as follows: stage 0 in this study represents empty follicles, or no presence of male or female gonad tissue; stage 4 represents both spawned and resorbing gonad; this method did not include a separate stage 5, due to the very high frequency of residual gametes, and no distinct partially spawned oysters (for gonad images, see ; Spencer et al. ).…”