Award: OCE-1416877

A major goal of this project was to learn how variation in ocean conditions due to upwelling of deep waters along the California coast affects animal populations today and how this might change in the future. Winds along the California coast cause "coastal upwelling", a process that upwells deep waters toward the surface. These upwelled waters are rich in nutrients that fertilize surface waters promoting growth of phytoplankton, the base of the food change for the very rich coastal ecosystem along California. However, these deep waters are also colder, lower in oxygen, and somewhat more acidic than surface waters. Exposure to these upwelled waters may be stressful for a variety of nearshore animals. Climate warming is affecting coastal upwelling, causing the deeper waters that are the source of upwelling to becoming warmer, but also lower in dissolved oxygen and more acidic. Will these changes have important impacts for coastal species? For our studies, we focused on red and pink abalone as "model" species that have similar life cycles to many invertebrate populations along this coast. Thus, we hope that results of studies of abalone will be relevant for many coastal species. We performed a variety of measurements and modeling (from oceanographic measurements to laboratory assays and computer models of abalone population changes) to determine how the combined effects of ocean changes may affect the life cycle and population success of abalone along this coast. Three major research efforts were brought together to make progress in understanding how changing ocean conditions will affect abalone and similar species. First, we used oceanographic sensors to measure variation in ocean conditions over time in several locations along the coastline, so that we have an understanding of the range in temperature, dissolved oxygen and pH (ocean acidity) experienced by abalone and other coastal species. We found that temperature, oxygen, and pH levels are highly variable on time scales as short as 1 hour; it is interesting that this high variation in ocean conditions is invisible to anyone walking along the shore, but is a strong signal in our sensors nearly every day. Second, we performed laboratory experiments using sophisticated aquarium systems that can mimic the type of ocean changes that occur daily off the coast. We were able to set a schedule for changes in oxygen, temperature, and acidity that was very similar to present-day conditions, as well as progressively more extreme conditions, as are expected to occur in the future. We examined the effects temperature (warm or cold), oxygen (low to high), and pH (normal to toward more acidic) for different life history stages of abalone – different stages of invertebrate life off this coast may be more or less sensitive to environmental change. For example, we found that fertilization of abalone eggs (obviously essential for population success) is not affected by changes in oxygen, but is impaired by ocean acidity lower than currently found along the coast – future waters may cause a problem for abalone. However, warming seemed to offset the negative influence of more acidic waters. Larval development, another key phase of abalone life cycles, was not impaired by the existing range of variation in ocean conditions. However, as exposure to deeper water increases from a few hours to over half or more of the day, survival of larvae declined. More importantly, when exposed to more intense conditions expected in the future (i.e., lower oxygen, increased acidity, and warmer), survival declined. Growth rates and shell development (calcification) were also reduced under future conditions. Our third theme has been to develop population models that take into account all of the oceanographic and biological data to predict how abalone popuations will fare in the future under increasingly different oceanographic conditions. These models incorporate the oceanography (e.g., variation in temperature, oxygen, pH, and currents) as well as key rates from biological studies (e.g., fertilization rates, the number of eggs for various sizes of female abalone, growth, and other factors) to predict whether the population will thrive or not. In addition, the models help identify key factors that have a disproportionate influence on population success – for example, it turns out that the survival and growth of early juvenile abalone is more important for the success of the population than how successful fertilization may be. Overall, we advanced the level of understanding of the range and scales of variation in ocean conditions associated with coastal upwelling, the sensitivity of key parts of abalone life cycles to the combined effects of changes in oxygen, temperature, and ocean acidity, and how these changes may lead to shifts in the successful growth and maintenance of abalone populations along this coast. Last Modified: 09/29/2018 Submitted by: James P Barry