Amanda Kahn is a postdoctoral fellow, working with Jim Barry. Amanda received a M.S. in Marine Science at Moss Landing Marine Labs, and then a PhD in Ecology from the University of Alberta, Canada, Department of Biological Sciences
Curriculum Vitae (pdf)
Google Scholar Profile
Stressors, energetics, and distribution of sessile benthic fauna in the deep sea
Sur Ridge is an underwater ridge off the coast of Big Sur, California with a stunning array of benthic animals, including hotspots with dense stands of sponges and corals. My research goals as a postdoctoral fellow at MBARI are to study patterns of natural distributions and ecophysiology of the fauna living at Sur Ridge. Working with Jim Barry, we’ll study the benthic animals at Sur Ridge to understand (1) their distribution on the seafloor, (2) the energetics of different animals using respirometry measurements, (3) the activity of sessile animals over time, (4) identify and document the dominant sponge species in the area and their diversity, and (5) the effects of stressors on the physiology and cell cycle of deep sea animals.
Objective 1: Distribution of animals in relation to the benthic boundary layer
For animals living on the seafloor, water conditions vary at a scale of centimeters to meters, which may result in fine-scale patterns in species’ distributions through the benthic boundary layer (BBL) – the area where water flow is affected and often slowed by the adjacent seafloor. Suspension feeders such as corals and sponges need water to flow past their particle capture mechanisms in order to feed, which is inhibited by the slow fluid flows of a boundary layer. To study this, we will characterize the water flow conditions in the BBL using current meters and the distributions of fauna present using new and existing video surveys from Sur Ridge.
Objective 2: Feeding ecology and energetics of deep-sea animals
The distribution of most animals is dependent on where their most energetically favorable circumstances exist; the deep sea is no exception. The amount of energy spent by an animal must be balanced by the amount of food energy eaten. Catching food gains food energy but there is a cost associated with it. Traditionally, predation has been credited as one of the most energetically costly modes of feeding whereas suspension feeding has been thought to be energetically efficient. Interestingly, one of the most common feeding guilds in the deep sea is deposit feeding, perhaps tied to the importance of marine snow as a food source in deep habitats. I am working to characterize the energetics of deposit feeders and suspension feeders, with the aim to ultimately compare the relative energetic cost of these two modes of feeding. This involves measuring feeding and respiration of sessile suspension feeders such as sponges, tunicates, bivalves, and polychaetes using oxygen sensors and water sample collectors deployed in situ with a remotely operated vehicle. Feeding and respiration of deposit feeders such as polychaetes, crinoids, and holothuroids will be measured using the Benthic Respiration System (BRS) developed by the Barry lab.
Objective 3: Activity of sessile deep-sea animals
What do sessile animals do when conditions change but they are stuck to the seafloor? Time-lapse imagery from Ken Smith’s group’s abyssal time-series research at Station M gives a dynamic view of the activity on the seafloor. I am studying the sessile animals (those attached to the seafloor) over those time-lapse deployments to see if there are detectable changes in them over time, and if so, whether we can correlate those changes to any other known ocean conditions such as carbon supply, pressure, temperature, or current speed or direction. We also plan to look at the animals at Sur Ridge with similar long-term observations and time-lapse.
Objective 4: Taxonomic identification of common deep sponges from the deep California coast
MBARI has an extensive archive of samples collected during cruises since its inception. Taxonomic experts routinely help with identifying fauna. I am working on identifying some of the sponges most commonly observed at Sur Ridge, and carnivorous sponges found along the California coast.
Objective 5: Detecting sub-lethal physiological effects of stressors at the cellular level
Cell proliferation and cell cycle lengths are sensitive to changes in the environment such as season, life history stage, and body region. Changes in cell proliferation may therefore be an innovative indicator of sublethal effects on fauna. Here at MBARI I aim to study the effect of stressors on cellular level processes of deep-sea benthic fauna.If cell proliferation rates change depending on a stressor, then even sublethal stressors would have a detectable and quantifiable effect on the ecosystem functions. In deep-sea fauna and elsewhere, this could serve as an excellent indicator of organism health in the face of looming changes in temperature, pH, and oxygen levels in the ocean.