Abstract This study examines the effects of temperature on the physiology and viability of a native catfish (Ictalurus punctatus), an introduced fish (Oreochromis niloticus, tilapia), and a native freshwater aquatic plant (Lemna spp, duckweed). The goal of this work is to relate how global climate change, largely raised temperatures, will affect living organisms and its distribution. As a result of increased temperatures, many drastic repercussions can and will occur. Living organisms that are conducive to warmer temperature will encroach the temperate zone and thus displacing the native species there in response to global climate change. Concomitantly, a rise in temperature will also cause elevated metabolic rates, which will translate to an increase in food consumption. At the same time, temperature increase may result in the demise of native temperate primary producers, as such threatening the food web. In this study, we test the effects of increase temperature on catfish and tilapia and measured their respiration rates as a surrogate for metabolism. In the plant experiment, we assessed the viability of duckweed that were exposed to ambient and a higher temperature slightly above their physiological range. Our results showed a higher scope change in respiration rates in the tilapia from 22oC to 34oC, while the change in the catfish was blunted. In the duckweed experiment, a two degrees increase from its physiological upper thermal limit result in increased mortality. We conclude that a small sliver of the effects, such as increased water temperatures, can elicit on a multitude of change in a community. Impact of Global Temperature Rise on Exotic Species Distribution Natalie Bentley, Madori Spiker, Christopher Peterson, and Christina Li Cluster 3: Living Oceans and Global Climate Change Oreochromis Niloticus (Tilapia) Lemnoideae (Duckweed) • • • • • • • Tilapia consume aquatic plants like duckweed. Optimal temperature range: 27.8-30°C Nile tilapia’s upper limit is 42°C. Range of Survival: 6-33°C Introduction Due to anthropogenic global climate change, rising temperatures are inevitable. Therefore, it is important to study the consequences of increasing water temperature on wildlife. Due to an increase in food demand, plants and animals that are deemed productive have been introduced by humans throughout the world. An excellent example of this is the tilapia (Oreochromis niloticus), a native fish from Africa and is now introduced to all continents except the Antarctica. Tilapias have in recent time become a staple fish product in the United States and are farmed extensively here with 2.5 million tons being projected in 2010. Therefore, the likelihood of encountering this exotic species in our waterways is not too far-fetch. In this study, we compared the respiratory physiology of tilapia and a native catfish at their upper thermal limit (Fig 1). In addition, we also examined the viability of a native aquatic plant over the same thermal range. The rationale of this work is to understand how global climate change can upset the ecology of a community. Figure 2 Results Duckweed: The mortalities were substantial when the plants were subjected to 35°C, albeit it is not significantly different from control. In the control group, only a few dead cells were found at 22 °C. The result shows that a change of 2°C in the upper thermal limit of the duckweeds greatly decrease viability, underscoring the sensitivity to temperature in primary production. Water temperature increase will not have an effect on catfish and tilapia respiration rates nor on duckweed mortality. Effects of Temperature on Duckweed Mortality Methods Duckweed: Three dishes of duckweed in water were placed at ambient temperature (control group, n=50 plants per dish) while another six were placed on a warming pad set to 35oC (experimental group, n=50 plants per dish). The plants were left at normal daynight cycle for five days before enumeration (Fig 2). Figure 1 Fish study: A large insulated thermal container was used to house the experimental fish (catfish, n=2 and tilapia, n=2), which were instrumented with a pressure transducer (Millar Instruments) in the buccal cavity for respiration rate measurements (Fig 1). Measurements were made at ambient temperature (22oC ) and subsequently raised by an aquarium heater to 34oC . An analogdigital convertor (DataQ, Ohio) was used for transforming the analog pressure signals from the Millar amplifier into digital bits onto a computer for post analysis. The most important finding of this study is that a small change in temperature fluctuation translates to large physiological change which can influence the composition of the community. In the case of the duckweed, a rise of 2 °C drastically affects the viability of the plants and thereby can cause a dramatic reduction in the food base. The fish study shows that a rise in temperature increases the ventilation rates – vis-à-vis increase metabolism - of tropical tilapia while temperate catfish stayed somewhat blunted. Global climate change will be conducive in extending the range of this exotic fish north of continental United States, which has seen its share of tropical invasive species. For example, the marine tropical lionfish are now common off Florida, Asian carps have invaded several of the major rivers, snakeheads are found in the astern seaboard, Asiatic swamp eels inhabit the Everglades. Tilapias which are grown by the millions can easily saturate our freshwater communities. Even if the native species can adapt to the temperature rise, they may not be able to compete with this artificially selected fish that were bred to feed and grow rapidly. Conclusion Fish: The increase in ventilation rate for the catfish was only 10 ventilations per minute from ambient to 34°C while in the tilapia the change was more than times as high (35 ventilations per minute). However, the catfish displayed a higher initial rate of ventilation than that of tilapia (78 ventilation/min vs 48 vent/min, respectively). , but the increase of ventilation in response to temperature rise was less than that of the tilapia otherwise. Overall, at the end of the experiment, before each of the species unfortunately died, the ventilation rate of the two species was about the same. Hypothesis Results are presented as mean+sem. Group differences for the duckweed experiments were analyzed by Student’s t-test while the fish experiments were determined by one-way ANOVA. The null hypothesis was rejected when p>0.05. Discussion Ictalurus Punctatus (Catfish) Optimal temperature range : 26°-29°C Catfish acclimated to 25°C has “upper lethal temperature” of 33.5°C Carnivorous but can consume aquatic plants as well Statistical Analysis Temperature plays a large role in defining the range and distribution of organisms. These three experiments showed that a rise in water temperature as in global climate change can have considerable impacts on plants and fish alike. Our data show that increases in temperature can have substantial effects on the overall success of fish and on the mortality rates of plants. If global warming continues to worsen, and anthropogenic activity continues to exacerbate our fragile environments we will most certainly see a threat in our food security. Bibliography http://tolweb.org/Ictalurus_punctatus http://aquafind.com/info/TilapiaLinks.php http://www.fao.org/fishery/culturedspecies/Ictalurus_punctatus/ en http://efotg.sc.egov.usda.gov/references/public/WY/Bio_No_303. pdf http://www.microponics.net.au/?p=181 http://www.news.com.au/features/environment/queensland-fishspecies-migrating-south-due-to-climate-change/story-e6frflp01225907524941 http://lemur.amu.edu.pl/share/php/mirnest/browse.php?databas es_selected=mirnest&species=Oreochromis_niloticus http://aqua.ucdavis.edu/DatabaseRoot/pdf/282FS.PDF http://www.fao.org/fishery/culturedspecies/Oreochromis_niloticu s/en Acknowledgments We’d like to thank Dr. Ngai Lai, Chase Hightower and members of Cluster 3 for assisting us with our experiments.