Date of Award

Summer 8-18-2023

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)


Marine Biology


Nishad Jayasundara

Second Committee Member

Paul Rawson

Third Committee Member

Huijie Xue

Additional Committee Members

Jeffery Runge

Zheng Wei


Ocean warming and pollution are two detrimental anthropogenic factors causing rapid marine ecosystem degradation recorded in the past decades. These factors alter the marine environment intolerable for many marine species, forcing them to either adapt or shift their contemporary habitat ranges to reduce the extinction risk embedded with environmental degradation. Estimating marine species’ habitat range shifts, and their potential for developing adaptive mechanisms are critical for ecosystem conservation and management, human health risk assessment, and climate change vulnerability assessments. Given that, for the first chapter of this thesis, we focused on developing a species distribution model (SDM) integrating marine species temperature-sensitive physiological factor, into a bioclimate model to better predict future habitat patterns with warming. We integrated two omics datasets for the second and third chapters to determine the potential transcriptomic and epigenomic mechanisms underlying marine species’ evolved resistance to extreme pollution.

We tested the new model to predict the future (the 2050s and 2080s) habitat ranges of the highly eurythermal intertidal minnow, Atlantic killifish (Fundulus heteroclitus), as a best-case scenario. Our SDM predicts complex and diverse habitat patterns for Atlantic killifish, including habitat fragmentation, migration between adjacent populations, and range contractions but no poleward range expansion. Our model predictions are quite unique compared to existing SDMs, mainly with the integration of thermal physiology into the model.

The molecular analysis in the second and third chapters posited the repeated desenstivity of the Aryl Hydrocarbon Receptor (AHR) pathway regulated through the downregulation of the ahr2 gene. ahr2 gene intron hypermethylation was also detected in a Polycyclic Aromatic Hydrocarbons (PAHs)-resistant killifish population, a potential novel molecular mechanism underlying killifish rapid adaptations to PAHs toxicity. Reduced lipid metabolism and mitochondrial respiration were also identified as other key molecular processes underlying the evolved PAHs resistance in Atlantic killifish.

Overall, the chapters of this thesis demonstrate the importance of integrating ectotherm physiology into SDMs to better predict their future habitat range shift patterns with ocean warming and the necessity of integrating different omics data to uncover the complex patterns of molecular mechanisms underlying marine organisms’ evolved resistance to ubiquitous aquatic pollution.