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Climate change is directly impacting the services humans derive from the sea at an accelerated rate. Ocean warming and acidification (i.e., a decrease in ocean pH) are leading to modifications in population sizes and ecosystem functioning. The observed shifts in these higher order processes are a direct result of individuals’ responses (i.e., physiology, including metabolism, growth, calcification, and survival) occurring within communities. Natural variation in past environmental exposure experienced by individuals may lead to greater population resilience, or it may push individuals past physiological thresholds leading to increased sensitivity and vulnerability to climate change. Thus, we need to determine how individual-level physiological responses to climate change scale up to influence marine ecosystems. Rocky intertidal habitats are an ideal study system for evaluating the relationships between individual physiological responses, ecosystem functioning, and climate change. Tide pools possess unique thermal and pH environments and can be monitored under natural conditions or manipulated with field-experiments over daily and seasonal time scales, creating natural “experimental mesocosms”. In addition, many species within rocky intertidal habitats are exposed to environmental conditions close to their tolerance limits, increasing their potential vulnerability to climate change. In Chapter 1, by utilizing the unique thermal environments of tide pools, I showed that across small spatial scales (pools), thermal history influences thermal sensitivity of marine invertebrates for short-term time intervals (1-week and 1-day) and that this relationship differs seasonally and between species with differing traits, including mobility. This suggests that variability in thermal responses among individuals may allow for a natural buffer at a population level in response to climate change. Multiple stressors may affect individuals independently or interactively, amplifying or mitigating effects. Thus, to determine the impacts of climate change, in Chapter 2, I used a 6-month long field manipulation of ocean warming and acidification in tide pools. I examined the combined effects of warming and acidification on the shell structure (shell thickness and corrosion) and functional properties (shell strength) of the ecologically critical species, the Pacific blue mussel (Mytilus trossulus). Acidification led to thinner, weaker, and more corroded shells whereas combined warming and acidification resulted in an increase in shell strength. My results suggest that to some degree, warming may mitigate the negative impacts of acidification on this mollusk species. Lastly, in Chapter 3, I characterize how warming and acidification, individually and interactively, impact net ecosystem calcification and the individual and population-level mechanisms driving impacts on net ecosystem calcification. Net ecosystem calcification tended to increase during the day and decrease at night; however, addition of CO2 during the hottest months led to decreased net ecosystem calcification and increased dissolution during both day and night. I found that individual mussel metabolic rates increased significantly in the presence of elevated CO2 and increased daily maximum of pool temperatures. Through this individual-level pathway, pH and temperature had a strong impact on the metabolic rates of individuals ultimately resulting in changes in net ecosystem calcification. On the other hand, greater mussel abundance was associated with increased net ecosystem calcification. Yet, with the addition of CO2, calcification decreased even in pools with the highest abundance of mussels, indicating that there are other pathways by which changes in pH can drive alterations in net ecosystem calcification. My dissertation reveals how species’ traits and natural thermal variation from short-term to seasonal time scales influence metabolic sensitivity to future warming among individuals (Ch. 1), independent climate stressors can negatively impact shellfish in situ, whereas the combined interactive effects between multiple stressors can lead to mitigation of the negative impacts of a single stressor alone (Ch. 2), and that ecosystem-level consequences of climate change are mediated by the abundance of dominant calcifiers and that this effect is dependent on the magnitude of acidification and warming (Ch. 3).

As climate change continues, anticipating species’ responses to rising temperatures, requires an understanding of the relationship between metabolic rate and thermal sensitivity, which itself may vary over space and time. We measured metabolic rates of three representative marine invertebrate species (hermit crabs Pagurus hirsutiusculus, periwinkle snails Littorina sitkana, and mussels Mytilus trossulus) and evaluated the relationship between thermal sensitivity (Q10) and thermal history. We tested the hypothesis that thermal history drives thermal sensitivity and quantified how this relationship differs over time (short-term to seasonal time scales) and between species. Organisms were collected from tide pools in Sitka, Alaska where we also recorded temperatures to characterize thermal history prior to metabolic rate assays. Using respirometry, we estimated mass-specific oxygen consumption (MO2) at ambient and increased temperatures for one individual per species per tide pool across three seasons. We evaluated relationships between thermal sensitivity and pool temperatures for time periods ranging from 1 day to 3 months prior to collection. For all species, thermal sensitivity was related to thermal history for the shorter time periods (1 day to 1 week). However, the direction of the relationships and most important thermal parameters (i.e., maximum, mean, or range) differed between species and seasons. We found that on average, P. hirsutiusculus and L. sitkana were more thermally sensitive than M. trossulus. These findings show that variability in thermal history over small spatial scales influences individuals’ metabolic response to warming and may be indicative of these species’ ability to acclimate to future climate change.

Variation in water temperature can have important effects on the energetics underlying metabolism, growth, and reproduction of many organisms. In order to anticipate how a species' allocation of energy may change in a warming ocean, we need to know the degree to which processes such as metabolic rate change with temperature (i.e., the thermal sensitivity of metabolism, Q10 ). In the context of long-term climate change, it will also be helpful to know whether local populations that experience different thermal regimes exhibit differences in thermal sensitivity. If so, it would indicate that thermal sensitivities of populations may adjust via acclimation or adaptation. We measured metabolic rates of Woolly Sculpin collected from two distant populations (Santa Cruz (SC) and Los Angeles (LA) counties, California, USA) and housed in a common environment. Using respirometry, we estimated resting mass-specific oxygen consumption ( MO2) and calculated metabolic rates (MR) at temperatures of 12 °C, 16 °C, and 20 °C for 59 fish. The Q10 value across this range of temperatures was 2.92. Populations did not differ with respect to overall MO2, nor did they vary in their degree of thermal sensitivity. However, the LA population had greater variation in MO2 among individuals when compared to the SC population. Larger variation in overall MO2 among individuals within specific populations may reflect greater genetic diversity , and this may buffer some populations against the effect of future increases in water temperature.

As climate continues to change, many marine species will experience both an increase in average temperature and more extreme diel and seasonal fluctuations. Understanding how these variations in ocean temperature affect processes such as metabolism and energy consumption is important for many species, and may be particularly important for sedentary species that cannot make large-scale movements in response to changes in environmental conditions. We examined how metabolic rates and energetic demands responded to temperature in a temperate reef fish, the bluebanded goby ( Lythrypnus dalli ). Using respirometry, we estimated resting oxygen consumption (VO2) for 42 L. dalli individuals of varying sizes and calculated metabolic rates (MR) at three different temperatures (13 °C, 16 °C, and 20 °C). As predicted, VO2 and MR increased significantly with temperature and mass, but the rate of temperature-dependent increase in metabolism indicated a very high degree of thermal sensitivity for L. dalli (Q10 value for VO2 was 5.21 across the range of experimental temperatures). The mass-scaling exponent (b ) was estimated to be 0.95 and aligned closely with other benthic species. Our results suggest that changes in temperature – especially those that occur over weeks and seasons – likely play a significant role in the ecology of these gobies. Long-term increases in seawater temperature will either necessitate an increase in foraging and consumption, or drive costly trade-offs between metabolism and processes such as growth and reproduction.

In this article we report relevant data that shed light on the topic of hope and patients' expectations in the use of DBS, for standard, approved, and established indications, based on a broader qualitative study on the ethical and social challenges that healthcare providers face in the field of DBS.