Predicting Marine Teleost Responses to Ocean Warming and Pollution

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

The Status of the Coral Reefs of the Jaffna Peninsula (Northern Sri Lanka), with 36 Coral Species New to Sri Lanka Confirmed by DNA Bar-Coding

Sri Lanka, an island nation located off the southeast coast of the Indian sub-continent, has an unappreciated diversity of corals and other reef organisms. In particular, knowledge of the status of coral reefs in its northern region has been limited due to 30 years of civil war. From March 2017 to August 2018, we carried out baseline surveys at selected sites on the northern coastline of the Jaffna Peninsula and around the four largest islands in Palk Bay. The mean percentage cover of live coral was 49 ± 7.25% along the northern coast and 27 ± 5.3% on the islands. Bleaching events and intense fishing activities have most likely resulted in the occurrence of dead corals at most sites (coral mortality index > 0.33). However, all sites were characterised by high values of diversity (H’ ≥ 2.3) and evenness (E ≥ 0.8). The diversity index increased significantly with increasing coral cover on the northern coast but showed the opposite trend on the island sites. One hundred and thirteen species of scleractinian corals, representing 16 families and 39 genera, were recorded, as well as seven soft coral genera. Thirty-six of the scleractinian coral species were identified for the first time on the island of Sri Lanka. DNA barcoding using the mitochondrial cytochrome oxidase subunit I gene (COI) was employed to secure genetic confirmation of a few difficult-to-distinguish new records: Acropora aspera, Acropora digitifera, Acropora gemmifera, Montipora flabellata, and Echinopora gemmacea