Our ocean is stratified; warm water floats above denser cold water. This seems basic, but it is a pre-condition for some fundamental environmental processes. The layered water column allows for the propagation of internal waves in the boundary between the warm and cold water layers that shoal and break just like surface waves, though may be up to 100m tall. Internal waves are critical for transporting nutrients from deep water into the kelp forest, but are also oxygen depleted (and low pH). My research seeks to understand the fate of these hypoxic internal waves inside the kelp forest/rocky reef system and the responses of the community therein. In a complex rocky reef, a process very similar to the formation of tide-pools, may also occur subtidally, forming an “internal tide pool”. If this is true, then spatial variability (patchiness) in the dissolved oxygen (DO) field likely changes dramatically with internal wave conditions. Moreover, in patchy oxygen, sensitive mobile organisms likely shift their distributions measurably to avoid pooled low oxygen areas.Using arrays of moored sensors, I measure the DO and temperature field under differing oceanographic conditions. These sensors opportunistically target areas where “internal tide pools” are likely to form. In addition, I map the DO/temperature field and fish distributions adaptively, providing high-resolution snapshots throughout an event. Using real time oceanographic data from the Kelp Forest Array, I can conduct surveys under opportunistic conditions with the Divining RO2D (the 2 is silent), a mobile oxygen/temperature/pressure sensor and stereo-video fish survey device of my own design. These methods allow me to correlate DO/temperature variability with short-term species distributions. To demonstrate a mechanistic link between DO variability and fish distributions, I’m conducting a series of behavioral experiments in the laboratory, testing avoidance thresholds and changes in startle responses. These measure oxygen level preference and influence on swimming ability, respectively. This combination of field observation and laboratory allows me to explain not only where fish move under varying oxygen conditions, but why they move.
Port, J. A., O'Donnell, J. L., Romero-Maraccini, O. C., Leary, P. R., Litvin, S. Y., Nickols, K. J., … Kelly, R. P. (2016). Assessing vertebrate biodiversity in a kelp forest ecosystem using environmental DNA. Molecular Ecology, 25(2), 527–541.
Walter, R. K., Woodson, C. B., Leary, P. R., & Monismith, S. G. (2014). Connecting wind-driven upwelling and offshore stratification to nearshore internal bores and oxygen variability. JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 119(6), 3517–3534.