American Research Journal of Earth Science

Geena S. Kye, Mrs. Clare Kennedy

Coral reefs are ecosystems that provide shelter to a variety of marine life, but they are deteriorating at an unprecedented rate. While factors like pollution and climate change have long been recognized as stressors to coral, the effects of ocean deoxygenation on coral have not been as deeply studied. Many commercially important fish, such as grouper and snapper, are dependent on the coral reef. Reef-related fisheries in the United States are valued at more than $100 million. The purpose of this study was to examine the effects of deoxygenation on the coral species Pachyclavularia violacea. As an indicator of coral health, tentacle extension was monitored using mobile timelapse-photography recordings taken over a period of 5 hours. Marine water from the tank was deoxygenated using the GastTM DOA-P704-AA High-Capacity Vacuum Pump. Two hundred (200) milliliters of water was added to the tank in which the coral was stationed; the control group receiving oxygenated water and the experimental group receiving deoxygenated water. It was anticipated that there would be some tentacle retraction due to the disturbance of the water column, unrelated to the oxygen saturation. The control group had a 32.5% reduction in tentacle extension compared to the experimental group at 59% reduction immediately following addition of the water. The average recovery was 20.9 minutes for the control group and 53.1 minutes for the experimental group. Based on these results, the conclusion that can be drawn is that coral fragments (P. violacea) are impacted by deoxygenation of immediate surrounding water. Future research will focus on completing additional trials to minimize confidence intervals and determine the hypoxia threshold for the recovery of P. violacea fragments. Long-range growth studies of corals grown in deoxygenated water should be a follow-up study.  

Yuntong Chu1, Dr. Andrew John Conith2

Introduction: Cichlids are a large group of freshwater fish. They are deep-bodied and have one nostril on each side of the head and rounded tails. The lateral line is discontinuous, and there are three or more anal spines. They usually do not grow longer than ~30 cm (12 inches). In many species, the rear edges of the dorsal and anal fins are pointed and the pelvic fins are elongated. Most cichlids are found in sub-tropical America, South America, mainland Africa, Madagascar, and southern Asia. Scientists estimate that there are at least 1,350 species worldwide, and possibly hundreds more new species yet to be described. Cichlids occupy a wide range of aquatic habitats, and where water temperatures are greater than about 68℉ (20℃). Cichlids exhibit a great diversity of feeding adaptations and consume numerous food types: phytoplankton, zooplankton, soft bottom deposits, benthic algae, higher plants, insects, molluscs, fish scales and fins, fish eggs and larvae, among others. Specialization of the jaws and dentition have allowed cichlid species to occupy a wide range of habitats and feed on a diversity of food types. The diversity of cichlids may be the result of a phenomenon called adaptive radiation. In order to adapt to their surroundings and quickly prey on new food sources, their body and head of cichlids exhibit extremely diverse morphologies, which allow them to achieve great success in specific diets in specific habitats. Objective: Because the cichlid’s varied head shape is related to a number of factors, I chose one of the possible factors – diet. Based on the cichlid’s diet, my goal was to work out how the length, width, and depth of the cichlid head associate with diet? Methods: In order to achieve the goal, I first placed eighteen landmarks on different types of cichlids’ CT scans by using MeshLab. Then I used numerous statistical analyses to assess differences between and among groups and to examine possible associations between diet and head shape and extract linear measurements from the landmarks(i.e., a t-test, analysis of variance (ANOVA) and a Tukey honest significant difference (HSD) test, and a linear regression). I used a t-test to understand if the means of two populations are different. I combined ANOVA and Tukey HSD to understand if there is a difference in means among multiple groups. And regression is used to examine correlations between two continuous (i.e., number) variables. All of these steps can be shown on the R programming language. Results: I observed differences between cichlid groups in their head lengths. The Utaka sand dwelling group typically exhibited longer heads relative to the Mbuna rock dwellers. The ANOVA revealed differences in head width between cichlids based on their diets (P = 0.0125), and a Tukey HSD test later revealed these differences were driven by the insect dietary group, in which cichlids exhibited much wider heads than both the plant and zooplankton groupings (P = 0.018 and P = 0.043 respectively). There was a strong correlation (r2 = 0.85) between the height of the skull crest (where feeding muscles attach) and the height of the skull bar (which resists feeding forces), P <0.001. Typically, cichlids that eat insects exhibit larger crests and bars compared to cichlids that eat plants and zooplankton. The figures below enhance the results.