Among marine habitats, intertidal areas are extreme in their variability: tides create a suite of physical changes that alter not only the mean and variance of environmental conditions, but also the frequency of exposure to stress. For species that develop in these habitats, survival and growth depend on biochemical defenses mounted by embryos or on the selective timing or location of reproduction by adults. Fitness consequences of spawning vary in time and space, but adults have imperfect information about future conditions that embryos will face. While adult responses are well-characterized, we know relatively little about consequences of variability or stress for early stages, which are especially sensitive to physical conditions and often represent a life-history bottleneck. This project is an integrative research program in the physiological ecology of intertidal reproduction and development. Egg masses of the mollusc Melanochlamys diomedea are tethered in tide pools on the surface of sand flats, where they experience developmental conditions that are highly variable within and between tidal exchanges. This species provides a sensitive and tractable system to relate embryo physiology, growth and survival, in both the lab and field, to conditions of environmental variability and stress. In addition, the ability to track adult reproductive output relative to environmental conditions allows tests of whether reproductive patterns are plastic and adaptive. Specifically, (1) To resolve developmental and ecological conditions for embryonic stress protein expression. Temperature thresholds and the developmental onset of stress protein induction in embryos collected in different seasons and from thermally distinct habitats will be determined. (2) To measure effects of temperature variability and stress on developmental performance. Embryos will be exposed to controlled temperature profiles to distinguish the contributions to performance of temperature mean, variance, stress level, and rate of change. (3) To estimate the developmental consequences of temperature variability under field conditions. Short-term exposure of egg masses to field conditions and manipulation of UV will be used to model the developmental consequences of natural variation in temperature and UV. (4) To evaluate the contribution of adult reproductive timing to developmental success. Adult reproductive patterns in the field will be used to test the hypotheses that the timing of reproduction is non-random, correlated with environmental conditions, and beneficial to offspring. Intellectual merit. Intertidal habitats offer a unique arena for understanding the impact of ecological conditions on marine development and life-history evolution. Because early stages are sensitive to physical conditions, and often represent a bottleneck in marine population dynamics, populations that reproduce in intertidal areas may be especially vulnerable to environmental challenges. This project develops a unique approach to understanding the intersection of environmental variability, developmental physiology, and reproductive ecology in a highly relevant marine environment. It integrates information on mechanisms of stress protection, developmental performance, field conditions, and reproductive timing to understand responses to variability and stress at two distinct but functionally-linked phases of the life cycle. By modeling development as a function of variation in natural conditions, it makes and tests explicit predictions about the fitness consequences of adult reproductive decisions. Because temperature stability is the dominant paradigm in marine development, research on responses to natural variability will further our understanding of both basic developmental biology and the physiological ecology of marine early life histories. Broader impacts. The proposed research and educational goals create opportunities for students at several stages of education to participate in integrative research. Involvement with the FHL Blinks Mentorship program will allow regular participation of minority students in the PI's lab and in the department honors research program. Work with the K-12 education coordinator at FHL will provide an opportunity to develop experimental, inquiry-based and environmentally-focused primary school learning exercises. Finally, participation in the community of developmental biologists and marine ecologists at FHL will help the PI and graduate students to promote intellectual exchange, synthesis, and teaching about marine development in an ecological context.
Edited 6/3/04 - JRP
