RT Dissertation/Thesis T1 The effects of climate change on reproduction and recruitment success of the acorn barnacle Semibalanus balanoides at its southermost European distribution limit (Galicia, Spain) T2 Efectos del cambio climático en el éxito de la reproducción y el reclutamiento del cirrípedo Semibalanus balanoides en su límite sur de distribución Europea (Galicia, España) A1 Herrera Rodríguez, Mariana Andreina K1 2401.06 Ecología Animal K1 2502.9 Cambio climático AB The effects of climate change on terrestrial and marine ecosystems worldwide are already visible in the form of changes in species distribution and phenology. The intertidal zone is a model system for examining the effects of climate change both because of the rapidity of its response, and because the rich historical record. An intertidal rocky shore organism widely used for parameterization of mechanistic species distribution surveys is the acorn barnacle Semibalanus balanoides (Crustacea, Cirripedia). S. balanoides provides an excellent study organism for being a common, widely-distributed member of boreo-artic communities whose populations are easily manipulated in the field and for which there is a wide literature on historical distributions and physiology. S. balanoides is an obligate cross- fertilizing hermaphrodite. Copulation takes place from November to early December. After copulation the penis degenerates and grows again during summer ready for the following November. Penis and gonad development in the population is highly synchronous, and probably controlled by light and temperature. Fertilized embryos are incubated over winter and nauplii larvae are released from the barnacle in March. Settlement and subsequent recruitment is highly variable at different spatial scales and between years. Since the southernmost European distribution limit of S. balanoides is set in Galicia, there is a particular interest in understanding the mechanisms that govern its distribution in the area and the effect that climate change can produce on their populations, as a model to understand the effect of global change on population dynamics of intertidal communities. The overall aims of this PhD dissertation is to determine the effects of climate change on Semibalanus balanoides, as a model organism of rocky intertidal communities, and their biogeographic boundaries in the northwest of the Iberian Peninsula, as well as to investigate the mechanisms governing its response to climate, in order to forecast effects of climate change on rocky shore organisms. Temperature-dependent variations in reproduction has been shown to cause year to year fluctuations on geographic limits of the species so it is expected that temperature change would severely affect S. balanoides reproduction and recruitment success at its southernmost European distribution limit. According to this, the main working hypothesis is that reproductive success of S. balanoides will be higher in colder locations, in agreement with the winter cold limitation of reproduction hypothesis. Consequently, we expect the reproductive cycle, fertilization, embryo development and recruitment, to have a better performance in colder locations. In order to test the main working hypothesis, the main objectives of this thesis are as follows: 1) To study the S. balanoides reproductive success in relation to temperature, at its southernmost European distribution limit. 2) To investigate S. balanoides recruitment at its southernmost European distribution limit in relation to temperature. The study will be carried out in the Ría de Arousa, located on the west coast of Galicia (NW Iberian Peninsula). Two locations were selected for the study, Palmeira (warm station) and Cabo de Cruz (cold station). In order to prove the main hypothesis, a series of studies will be conducted to assess the key aspects of the reproductive success of the species: reproductive cycle, fertilization and embryo development. Since recruitment is one of the most important aspects governing the species distribution ranges, there is particular interest in understanding the mechanisms that rules this process. In order to test the main hypothesis, a series of experiments will be conducted: substrate selection for settlement, settlement and recruitment in the field and predation effect on settlement and recruitment. YR 2019 FD 2019-11-25 LK http://hdl.handle.net/11093/1370 UL http://hdl.handle.net/11093/1370 LA eng NO NASA grant NNX11AP77G and NSF grant 1129401 DS Investigo RD 17-feb-2025