Ocean Acidification Impacts in Polar Ecosystems

We are currently examining the interacting and potentially synergistic influence of two oceanographic features –ocean acidification and the projected rise in mean surface seawater temperatures– on the performance of a dominant faunal group of the Antarctic ecosystem, fishes of the suborder Notothenioidei. In this collaborative project, we are combining approaches from the fields of organismal physiology, functional genomics, and evolutionary biology in order to assess the impacts of global climate change on a vulnerable ecosystem. Understanding the interacting impacts of these two features is a vital step in predicting the resiliency of coastal marine ecosystems. Using both field and laboratory-based approaches, my lab aims to examine the combined impacts temperature and low pH will have on the metabolic oxygen demand, acid/ base homeostasis, and the capacity to mount an effective cellular stress response of an important group of fishes that have displayed incredibly narrow physiological limits in previous single stressor studies.

The notothenioids comprise a diverse group of fishes that have repeatedly displayed a narrow window of physiological tolerances when subjected to abiotic stresses. Given the propensity for both adaptive and potentially mal-adaptive traits found among these organisms and their narrow physiological limits, this system provides a unique opportunity to examine physiological trade-offs associated with acclimation to a multi-stressor environment consistent with future atmospheric CO2projections. As an extension of the functional measurements, this study will use evolutionary genetics as a means to map variation in physiological responses onto the phylogeny of these fishes in order to gain insight into potential for adaptation for fishes inhabiting specific niches.

Regulation of the Cell Stress Response in Extreme Stenotherms

Extreme environments can at times heighten or even relax selective environmental pressures on physiological mechanisms employed to maintain cellular homeostasis. These events can lead to changes in the cis and trans regulatory mechanisms for highly conserved processes such as the cellular stress response. There is already some evidence that these highly conserved mechanisms have been altered in notothenioid fishes. We are currently looking into the effect evolution in extremely cold, stable ocean environments has had on the regulatory roles of trans acting regulatory proteins and the cis elements they interact with. 

Epigenetic controls of local adaptation

Epigenetic markers such as DNA methylation are known to affect phenotype in a variety of organisms. We have been characterizing the epigenome of the California mussel and assessing the role DNA methylation may play in establishing locally adapted traits in this species across short biogeographic scales. We are currently employing a variety of techniques, including reduced representation whole genome bisulfite sequencing and methylation specific PCR to the probe site specific methylation status of genes that show differential expression in M. californianus populations. 

Hypoxia Impacts in the California Current Large Marine Ecosystem

The marine intertidal zone is characterized by large variations in temperature, pH, dissolved oxygen and the supply of nutrients and food on both seasonal and daily time scales. These oceanic fluctuations are drivers of ecological processes such as recruitment, competition and consumer-prey interactions through mechanistic linkages that are largely physiological. In addition, these variable physiological capacities will likely vary over a species range, and this eventuality may drive local adaptation in a way that may influence our interpretations of how physiology changes over large spatial scales. Thus understanding of coastal ecosystem dynamics, and in particular, response of these systems to climate change, it is crucial to understand these linkages. In order to further examine the linkages of variation in performance across space and to begin to address the influence of GCC on marine ecosystems, we have teamed with the laboratory of Bruce Menge at Oregon State University to examine physiological variation in an ecologically dominant species, the mussel Mytilus californianus.

We are currently utilizing transcriptome analysis of the physiological response of M. californianus at different spatial scales to gain insight into these linkages. Theses approaches have recently highlighted two distinct gene expression signatures related to the cycling of metabolic activity and perturbations to cellular homeostasis that may be gated by oceanographic differences in food and stress environments between sites separated by as little as ~65 km. These new insights into environmental control of gene expression may allow understanding of important physiological drivers within and across populations. 

Biosensors of Emerging Contaminants

The Mussel Watch Program, initiated in 1986, provides the longest running continuous record of coastal contaminants, based on biannual sampling of mussels from 300 fixed sites around the nation’s coasts. However, the recent emergence of new chemicals of concern to coastal managers, including flame retardants, pharmaceuticals, and nanoparticles, taxes the ability of the existing Program to provide adequate monitoring to meet region-specific needs. In California, a pilot project was therefore initiated in 2010 to modify Mussel Watch sampling design to meet region-specific needs. Because the cost of contaminant analysis is high, the incorporation of a biosensor sensitive to contaminants and capable of discriminating contaminant classes would be valuable for directing expensive analytical costs to the most critical sites. 

Using next generation sequencing we are working to identify gene networks whose expression levels are sensitive to low level contaminants  in attempts to generate a bioarray for rapid detection analysis via multiplexed qPCR assays. This project will evaluate the suitability transcriptional responses that (1) report chemical contamination and (2) discriminate among contaminant classes in field deployed mussels from the Mytilus genus.