Oceanic rumblings : midtrophic responses to oceanographic variability observed through acoustic and diet analyses
Abstract/Contents
- Abstract
- Open ocean ecosystems are the largest on the planet, containing an enormous diversity of organisms boasting incredible adaptations to life in a mostly dark, seemingly featureless habitat. Despite the heavy reliance on marine resources by countries across the globe, there remains a large gap in our basic understanding of marine ecosystems, particularly with respect to the organisms at the center of open ocean food webs: micronekton. These small, swimming animals are notoriously difficult to quantify, commonly avoiding conventional sampling methods and occurring across large areas that are costly to sample. In this dissertation I collaborated with existing monitoring programs to generate timeseries that capture variability in the composition, abundance, and distribution of micronekton communities with respect to environmental variability. I examined changes in diet composition and prey availability for Humboldt squid, Dosidicus gigas, in the Gulf of California (GOC), Mexico between 1996 and 2017. Humboldt squid in this oceanographically-variable region have exhibited a large range in mature size (15-85 cm mantle length) associated with the El Niño Southern Oscillation (ENSO), but it is unclear how their role in the ecosystem changes with respect to body size or how their prey respond to ENSO. I demonstrated that Humboldt squid diet in the GOC is more different between squid collected in different environmental conditions than between individuals of different sizes. Prey responses to environmental variability were directly assessed with nighttime acoustic observations in the same region. In conjunction with strong El Niño events, I observed significant reductions in forage biomass, which remained depressed for 2-3 years following the event regardless of subsequent environmental conditions. I also described variability in the diet of longnose lancetfish, Alepisaurus ferox, across the central North Pacific Ocean using specimens collected by federal fisheries observers in the Hawaii-based deep-set longline fishery, and demonstrated that continued monitoring of lancetfish diet could be used to quantify environmental responses of their diverse micronektonic prey. My work provides unique insights into large-scale spatiotemporal variability in two open ocean forage communities and contributes to our understanding of the role micronektonic organisms will play in mitigating or exacerbating the effects of ocean warming on marine resources.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2019; ©2019 |
| Publication date | 2019; 2019 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Portner, Elan Joseph |
|---|---|
| Degree supervisor | Gilly, William |
| Thesis advisor | Gilly, William |
| Thesis advisor | Hazen, Elliott Lee |
| Thesis advisor | Micheli, Fiorenza |
| Thesis advisor | Somero, George N |
| Thesis advisor | Benoit-Bird, Kelly |
| Degree committee member | Hazen, Elliott Lee |
| Degree committee member | Micheli, Fiorenza |
| Degree committee member | Somero, George N |
| Degree committee member | Benoit-Bird, Kelly |
| Associated with | Stanford University, Department of Biology. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Elan Joseph Portner. |
|---|---|
| Note | Submitted to the Department of Biology. |
| Thesis | Thesis Ph.D. Stanford University 2019. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2019 by Elan Joseph Portner
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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