Bioluminescent plankton: Association with thin layers and marine snow in coastal oceans

The distribution of open-ocean bioluminescence (BL) has been well studied, but fine-scale coastal BL distributions remain poorly understood. This dissertation addresses two aspects of fine-scale coastal bioluminescence structure: BL thin layers and BL-enriched marine snow, as well as the development of new oceanographic tools for measuring fine-scale BL distributions. Because BL plankton can both deter grazing by small plankton and attract predators to those grazers, BL emissions may be a mechanism for recruitment to or dispersal of plankton from fine-scale structures, such as thin layers and marine snow. The existence of BL thin layers and BL-enriched marine snow now suggests that plankton have more available niches than previously imagined in coastal environments and argues for the importance of accurately detecting fine-scale structures. They are vitally important to understanding complex food webs and coastal carbon cycling.; To determine if BL was enriched on marine snow relative to ambient water, individual aggregates and surrounding water samples were collected by hand using SCUBA, and mechanically stimulable bioluminescence (BL) was measured. These are the first quantitative estimates of BL marine snow over the water column in a coastal environment. BL was enriched up to 180 times on aggregates as compared to an equal volume of surrounding seawater, and the contribution of BL associated with marine snow to total BL in the water column varied between <1–78%. The ecological significance of these “islands of light” to the pelagic zone is discussed.; The composition, persistence, and thickness of BL thin layers have been documented for the first time in a coastal environment. The association of BL thin layers with zooplankton, marine snow, and phytoplankton distributions were simultaneously investigated in East Sound, WA, a shallow fjord where thin layers episodically occur. Two new instruments measured BL potential and BL organism distributions within fine-scale structures. The BL thin layers, ranging from 1.2–1.5 m in thickness, were primarily composed of BL heterotrophic dinoflagellates. They did not spatially co-occur with thin layers composed of other constituents, but passively followed a single isopycnal located significantly below the other thin layers over the nighttime hours.