ALBERT

Description: The effects of climate change, including ocean acidification and ocean heatwaves, on biological communities in estuaries are often uncertain. Part of the uncertainty is due to the complex suite of environmental factors in addition to acidification and warming that influence the growth of shells and skeletons of many estuarine organisms. The goal of this study was to document spatial and temporal variation in water column properties and to measure the in situ effects on larval and recently settled stages of ecologically important Olympia oysters (Ostrea lurida) and commercially important Pacific oysters (Crassostrea gigas) in a low‐inflow estuary with a Mediterranean climate in Northern California. Our results reveal that seasonal inputs of upwelled or riverine water create important and predictable gradients of carbonate system parameters, temperature, salinity, dissolved oxygen (DO), and other variables that influence oyster performance, and that the influence of these gradients is contingent upon the location in the estuary as well as seasonal timing. During upwelling events (dry season), temperature, carbonate chemistry, and DO had the greatest impact on oyster performance. During runoff events (wet season), gradients in salinity, nutrient concentrations, and total alkalinity driven by river discharge were comparatively more important. These results suggest that the spatial importance of carbonate chemistry and temperature are seasonally variable and are two of several other factors that determine oyster performance. We use these results to discuss future impacts on oysters given projected regional changes in the frequency and magnitude of upwelling and precipitation‐driven runoff events.

Description: Under the ocean acidification (OA) conditions predicted for 2100, the larval stages of temperate sea urchins are smaller, with reduced and abnormal skeleton and changes in metabolic rate. Here, we measure the impact of near-future and long-term predictions of atmospheric pCO2 levels on the early development of the echinometrid sea urchin Evechinus chloroticus using single male:female crosses, effect sizes and a within-study meta-analysis. Using the developmental signpost of the 16-cell stage, we show a mean delay of 5.11 min at pH 7.7 and 11.85 min at pH 7.5, which may have flow-on effects to later embryo and larval stages. Echinopluteus larvae raised in OA conditions (pH 7.7, 7.5) were 5–10% smaller in body length and 10–12% smaller in arm length than controls. Metabolic rate was highly variable between single male:female crosses—increasing in some crosses, decreasing in others—with a non-significant effect size in the meta-analysis. Preliminary experiments suggest that metabolic rate changes may be impacted by loss of mitochondrial function at low pH. Single male:female crosses showed variable OA responses in all measurements, suggesting that when assessing the population-level impacts of OA on early development of sea urchins there is a need to include high levels of biological replication.