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dc.contributor.author Malm, Preston Dana
dc.date.accessioned 2017-06-05T19:30:43Z
dc.date.available 2017-06-05T19:30:43Z
dc.date.issued 2016
dc.identifier.citation Malm, Preston Dana. 2016. The Influence of Sand Grain Size and Macrophyte Wrack on Habitat Selection and Behavior of Talitrid Amphipods on Northern California Beaches. Department of Biology, Sonoma State University. en_US
dc.identifier.uri http://hdl.handle.net/10211.3/192512
dc.description.abstract Although forming the majority of the Earth's ice-free coastlines, surprisingly little research has been conducted on sandy beach ecosystems in general and in northern California in particular. Sandy beach ecosystems overlap considerably with human activities and have high ecological connectivity to several other ecosystems. They are characterized by low levels of in situ primary productivity, and can be heavily subsidized by adjacent ecosystems. Macrophyte wrack from adjacent marine ecosystems provides major inputs of organic matter to sandy beaches that a variety of consumers rely on. Talitrid amphipods1 Megalorchestia spp., are major consumers of wrack on beaches in California, that play a key role in intertidal food webs and ·ecosystem function. They are highly mobile nocturnal animals that occupy temporary burrows in intertidal sand during the day. We hypothesized that macrophyte wrack abundance and composition, as well as beach sediment characteristics would influence the structure of talitrid amphipod assemblages on beaches along the north central California coast. Five species of talitrid amphipod were observed at our study sites, and total amphipod abundances across sites ranged from O ind m·1 to 12,691 ind m·1 of shoreline. Non-metric Multidimensional Scaling analyses (NMS) of amphipod assemblages showed strong links between total amphipod abundance, physical characteristics of site including grain diameter and beach slope, and the abundance of less palatable eelgrass wrack. We experimentally investigated the role of sediment grain size on burrowing behavior and feeding rates of one of the five amphipod species found in the region, Megalorchestia californiana. We hypothesized that amphipod bun-owing behavior would be affected by sand grain size, and that these behavioral differences might lead to different feeding rates. In addition we hypothesized that feeding rates and grain size preferences influence observed differences in abundance among beaches. Offered a range of five grain sizes in a laboratory experiment, amphipods preferred to burrow in sand of finer grain size. Amphipods burrowed to greater depth and remained under the surface for longer periods in fine sand. Wrack consumption increased with increased grain size. Our results indicate that sediment grain size and macrophyte wrack composition may interact to affect behavior and likely the energy budgets of talitrid amphipods. This could influence the species distribution and abundance of talitrid amphipod populations among beaches. Our results have implications for understanding how congeneric talitrid amphipods may coexist and for beach management including common activities such as sand nourishment or movement and grooming to remove macrophyte wrack as such activities may have a profound effect on talitrid amphipod populations, and their influence on the functioning of sandy beach ecosystems. en_US
dc.description.sponsorship I thank my advisors Karina Nielsen and Dan Crocker and committee members Jenifer Dugan and Nathan Rank for their guidance, wisdom, and most importantly their patience. It has been a long road. I thank Karina Nielsen and Jenifer Dugan, in particular, for their help in editing this manuscript. I thank all those who lent a hand with data collection including Trevor Manger, Colin Donlevy, Thomas Nguyen, Katie Azcarraga and everyone else that helped collect and identify hundreds of amphipods. I thank fellow graduate students Jill Stokes, and James and Emily Hovis for support and friendship. I thank the following agencies and organizations for funding and financial support: California Sea Grant, California Ocean Protection Council, California Department of Fish and Wildlife, Marine Protected Areas Monitoring Enterprise, California Ocean Science Trust contributed support for my thesis research through a grant to my advisor, Karina Nielsen; and the California State University Council on Ocean Affairs, Science, and Technology for a Graduate Research and Graduate Travel award to me. Thank you to my family, especially to my mom, who pushed me onward and supported me unconditionally throughout my entire academic career. I would not have made it through graduate school if you were not around to talk when I was struggling through some very hard times. Thank you to my wife Carly for your understanding and motivation but most of all your love. I would not have completed this thesis if not for you. en_US
dc.language.iso en_US en_US
dc.publisher Department of Biology, Sonoma State University. en_US
dc.title The Influence of Sand Grain Size and Macrophyte Wrack on Habitat Selection and Behavior of Talitrid Amphipods on Northern California Beaches en_US
dc.type Thesis en_US
dc.contributor.sonomaauthor Malm, Preston Dana
dc.contributor.committeeMember Nielsen, Karina J.
dc.contributor.committeeMember Crocker, Daniel
dc.contributor.committeeMember Rank, Nathan
dc.contributor.committeeMember Dugan, Jenifer


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