Life Sciences Commons^™

Effects Of Rapid Ph And Salinity Change On The Physiology Of A Local Estuarine Fish Species, Fundulus Heteroclitus, Shauna Tietze

GS4 Georgia Southern Student Scholars Symposium

Coastal Georgia offers a wide variety of unique aquatic environments, one of the most variable of these environments are salt marshes. Sapelo Island, Georgia, is a pristine environment that is home to many variable salt marshes. Throughout marshes, salinity ranges from freshwater to full strength sea water and acidity levels range from neutral (pH 7) to low pH (pH < 4.5). Fundulus heteroclitus (Atlantic killifish) is an example of an organism that has evolved coping strategies to withstand such a variable environment. Many laboratory studies have shown that F. heteroclitus exhibit a broad tolerance range of single stressors, however few have studied their ability to handle multiple stressors simultaneously. Our goal is to determine if exposure to low salinity and low pH combined is more stressful to F. heteroclitus than individual exposure to low salinity or low pH. To address this area of interest a laboratory experiment was designed. F. heteroclitus were captured from a site with neutral pH (6.8) and mid-range salinity (16 ppt) and held in the laboratory for one month at the same water conditions. The water conditions of the capture site represents similar conditions to where the fish were most commonly found on the island. Fish were then placed in tanks with four different water treatments; low salinity, low pH, low salinity and low pH combined, and a control and held at these conditions for one week. Six fish were sampled from each treatment group at 24 hours, 5 days, and 7 days post transfer. During sampling fish were euthanized, the gills were taken for gene expression analysis and the rest of the body was used for cortisol analysis. Changes in the mRNA expression levels of Cystic Fibrosis Transmembrane Conductance Regulator and Na /K -ATPase were compared between treatments using qRT-PCR analysis. These genes have been shown to play an important role in ion regulation in the gills by altering cell volume and ion movement in the sodium/potassium pump. Cortisol was also analyzed using an ELISA kit (Neogen) as a general stress response measure. I hypothesize that results from gene expression and cortisol analysis will show that F. heteroclitus challenged with low salinity and low pH combined experience a higher level of stress compared to fish challenged with only low salinity or low pH, exhibited by an increase in cortisol levels and increased expression of genes responsible for ion balance The information gained from this project will provide a better understanding of the stress this species exhibits due to rapid pH and salinity change. As well as, whether fish can rapidly adapt to changing conditions. Given the ubiquity of the common killifish and its importance in estuarine food webs, these data may provide insight into how we can manage and maintain diverse fish populations and support ecosystem functioning.