Nearshore Processes Influencing Larval Distributions and Coastal Population Dynamics Along an Upwelling Coast
- ISBN-10
- 0438930126
- ISBN-13
- 9780438930124
- Language
- English
- Published
- 2018
- Author
- Erin Vera Satterthwaite
Description
An enhanced understanding of the processes that influence coastal populations is central to our understanding of life in the sea and effective marine management. Since many benthic marine species have a dispersing, larval phase, processes affecting both the larval and benthic, adult phases are important in structuring populations. Thus, elucidating key processes affecting population dynamics requires a comprehensive understanding of nearshore, coastal, and benthic processes. In addition, along coasts influenced by upwelling, populations are often considered to be recruitment-limited, thus processes acting on the larval phase are essential in influencing nearshore population dynamics. Consequently, understanding the sources of variability in reproductive output, larval transport, supply and recruitment are integral to the dynamics, structure and effective management of marine populations and communities. In this dissertation, I investigated the effect of nearshore processes on invertebrate larval distributions, reproduction, and recruitment along the California coast, which is characterized by upwelling and relaxation dynamics during the spring and summer. Seasonal variation in upwelling and relaxation dynamics influence dispersal and recruitment. In Chapter 1, I investigated the effects of seasonal variation in nearshore physical oceanography on invertebrate larval distributions in the upwelling-dominated region of northern Monterey Bay, California. I characterized the physical oceanographic factors in summer and fall and related these to the invertebrate larval assemblage. I found that water types differed seasonally in temperature, salinity, stratification, and chlorophyll-a fluorescence with a corresponding shift in the composition and abundance of invertebrate larvae in the meroplankton assemblage. This suggests that relationships between larval taxa, life history characteristics, and water types could provide insights into water mass history, circulation, and larval recruitment, in highly dynamic upwelling regions. Physical oceanography coupled with sites of larval release and depth regulation by larvae influence larval distribution patterns. In Chapter 2, I explored the cross-shore and depth distribution patterns of larvae in northern Monterey Bay. Larvae of nearshore species predominately occurred near the bottom and in the inner bay, and larvae of offshore taxa occurred near the bottom and offshore, often associated with offshore water masses. In addition, taxa with similar adult habitat and depth distributions co-occurred in larval samples. Thus, aspects of the entire life history, such as adult habitat distribution, must be considered when attempting to elucidate drivers of larval transport, larval supply and population dynamics of benthic marine organisms. Since larval dispersal can lead to the spatial decoupling of reproduction and recruitment, elucidating the key factors affecting the relationship between reproduction and recruitment, known as the stock-recruitment relationship, is key for predicting recruitment to coastal populations. In Chapter 3, I measured reproductive output and recruitment in a model intertidal crab, Petrolisthes cinctipes, metapopulation along the California coast and compared reproduction and recruitment to wave exposure, habitat quality (grain size), and habitat sizes of each site. I found that wave exposed sites had more habitat and lower densities of recruits. Wave exposure did not influence the quality of habitat, which influenced the density of reproductive females. Thus, metapopulation dynamics were affected by both wave exposure, through its effect on habitat size and recruitment, and habitat quality, through its effect on reproduction. Consequently, the relationship between nearshore hydrodynamics that create and maintain quality coastal habitat patches and deliver larvae to shore is a key question in source-sink dynamics of marine metapopulations and stock-recruitment relationships. These results help to advance our understanding of how nearshore oceanographic processes, habitat characteristics, and life history affect variation in demographic rates of marine populations in upwelling systems. A comprehensive understanding of the processes regulating populations, both in the plankton and benthos, has implications for advancing fundamental ecological and evolutionary questions pertaining to marine populations and communities, along with improving marine resource conservation and management.
