Week 15 Activity

End of Semester Review You are charged with understanding the population dynamics and conservation of the Kemp's Ridley sea turtle - an endangered sea turtle that was recently rediscovered on Louisiana’s Chandeleur islands. (Hear all about it on the Sea Change podcast - this episode gives additional context for the questions below, but is not required that you listen to it before addressing the questions.) Answer the following questions about population dynamics that you will likely have to address as part of your work: 1. Your first goal is to estimate the population size of the sea turtle population on this island. After a long trip searching across various islands in the Chandeleurs, you manage to find 5 adult sea turtles and mark each one with a tag. Four weeks later, you return to the islands with a big team of volunteers and together find 8 sea turtles, of which 2 bear your tag. a. What is your best estimate of the total population size of nesting sea turtles on the islands? Show all your calculations. (0.5 pt) The best estimate of the total population size is calculated by using the formula N total = (N marked * N captured )/(N captured,Marked ). The N total is the total estimated population based on the initial marked turtles, N marked , and the number of captured turtles that were marked after a period of time, N captured, marked . N total = (5*8)/2 = (40)/2 = 20. The estimated total population size of the sea turtles is 20. b. Let’s define 𝑥 as your population size estimate from part a. What is one reason why the actual population size of the sea turtles might be higher than 𝑥 ? What is one reason why the actual population size might be lower than 𝑥 ? (0.5 pt) The actual population size of the sea turtles may be higher than 𝑥 because the mark-recapture method does not account for turtles that may have migrated into the area or for turtles that may have given birth within that time as they are only capturing adult sea turtles. The population size may be lower than 𝑥 because the marks may have washed off individuals and some turtles may have migrated out of the area. Even though the mark-recapture method assumes this does not happen, they do happen in the environment. 2. From completing a thorough literature survey of sea turtles, you assemble the following life table transition diagram for sea turtle populations (note that “Y.A” stands for “young adult”, and “O.A.” for Old Adult):

a. Use the diagram above to write the life-transition matrix for this population. (0.5 pt) 0 0 30 80 4 0.05 0 0 0 0 0 0.25 0 0 0 0 0 0.5 0 0 0 0 0 0.05 0 b. You are tasked with assembling a crew of volunteers to help track and protect every single sea turtle egg laid on the Chandeleurs, such that each egg results in one hatchling making it back into the ocean. In the life table matrix above, which parameter(s) would your conservation efforts be affecting? Based on what we learned in class, what is an analysis technique you can use to evaluate whether this is a good use of your and your volunteers’ time? (0.5 pt) The main parameter that would be directly affected is the amount of young adults, but it is not clear if the adult and old adult parameters would be affected as it is not clear if the hatchlings make it past the young adult stage. The analysis technique that can be used to evaluate whether what stage to focus efforts on is by manipulating each stage and calculating what stage will increase the eigenvalue of the matrix the greatest. The stage that increases the eigenvalue the greatest is the stage that efforts should be focused on. 3. From observing the biodiversity dynamics on the island, you begin to suspect that large seabirds like Magnificent Frigatebirds are an important and dangerous predator of sea turtle hatchlings. (e.g. see this video ). You realize that the Lotka-Volterra consumer-resource dynamics model might be useful for understanding predator control of sea turtle hatchlings. a. What are the equations of the consumer-resource dynamics model? Please provide verbal explanations of each model parameter. The equations for the Lotka-Volterra consumer-resource dynamics are dN 1 /dT = r 1 N 1 (1-a 11 N 1 -a 12 N 2 ), dN 2 /dT = r 2 N 2 (1-a 21 N 1 -a 22 N 2 ), dR/dT = rR-aRC, and dC/dT = eaRC - mC. The first two equations deal with the interspecific competitive effects between species 1 and species 2. N is the density of species 1 or 2 corresponding to the subscript. The intrinsic growth rate is depicted by r. Lastly, these two equations display the intraspecific and interspecific competitive effects of species 1 on itself (a 11 ), species 2 on species 1 (a 12 ), species 2 on itself (a 22 ), and species 1 on species 2 (a 21 ). The resource species dynamics formula is dR/dT = rR-aRC, which calculates the resource species over a given time. R is the population of the resource species, r is the growth rate of the resource species, a is the rate at which the consumer depletes the resource, and C is the population of the consumer species. The consumer species dynamic is calculated using the formula dC/dT = eaRC - mC, which accounts for the population of the consumer species over a given period. C is the population of the consumer species, a is the rate that the consumers deplete the resource species, e is the efficiency at which the energy the consumer receives is used, R is the population of the resource species, and m is the maintenance cost or energy that was lost from the consumer species. b. As the population of sea turtles starts growing on the islands, what effect is this predicted to have on the consumer and resource isoclines? As the population of the sea turtles begins to increase, the effect it has on the consumer and resource isoclines depends on what relationship is looked at. If the turtles are the consumer

b. Your collaborators suggest that you should quantify patterns of temporal beta diversity in the Chandeleur system. What kind of data would you need to achieve this goal? The data that is needed to quantify the patterns of temporal beta diversity are the species that are found in different communities. Beta diversity is calculated by picking out what species are unique to one community and then adding those species up so the data on what species live in which communities is needed. 5. The very existence of the Chandeleur Islands is, like lots of other land in Louisiana, under threat due to sea levels that are rising because of perturbations to the global water cycle. a. Identify three major pools, and three major fluxes, from the global water cycle. Three major pools of the global water cycle are the oceans, lakes, and the atmosphere. Three major fluxes of the global water cycle are evaporation, precipitation, and transpiration. b. In class, we discussed an important feedback loop in the water cycle whereby the precipitation regime structures the plant community in the Amazon rainforest, which in turn affects the precipitation regime. Do you think such a feedback loop is relevant to precipitation dynamics in Louisiana? Why or why not? Yes I think there is a relevant feedback loop for the precipitation dynamics in Louisiana but it is not as severe as the one in the Amazon Rainforest. Throughout the year, Louisiana is humid and rain weather can happen at any time because we are in an area that needs moisture and rain to thrive. For example, this past summer when we did not receive much rain at all, all the vegetation began to die because our state is used to rain throughout the year at some point and not used to intense like we received.