Assessing the impact of seismic surveys on invertebrate mechanosensory organs

Supervisory Team:

Primary supervisor: Ryan Day

Co-supervisor: Jayson Semmens

Brief project description:

Increasing human activity in the ocean has resulted in a corresponding increase in anthropogenic aquatic noise, which is gaining recognition for its potential to negatively affect marine organisms. Aquatic noise can be an unintentional by-product of human industry, such as vessel noise from shipping traffic, or produced with a purpose, such as seismic surveys that are used to investigate the geology below the seafloor. Among the various sources of aquatic noise, the impacts of signals from seismic air guns have received a relatively great deal of attention, primarily in regard to whales and fishes, due to the high intensity of the low-frequency signals and the repetitious nature of surveys, which systematically ensonify hundreds to thousands of square kilometres over the weeks to months surveys are conducted.

Compared to vertebrates, the effects of marine seismic surveys on marine invertebrates remain poorly understood, with only a limited number of field-based experiments performed to date. However, multiple incidences of mass stranding of giant squid (Architeuthis dux) reported following seismic surveys in the general region led to the finding that the statocyst, the mechanosensory organ responsible for detecting gravity, body positioning, and movement that is commonly found in aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans, showed extensive damage. In a field study, with a single air gun, southern rock lobsters (Jasus edwardsii) exposed to air gun signals showed damage to their statocyst. Similarly, in laboratory-based experiments simulating aquatic noise, squid and octopus have shown severe responses to exposure, with progressive degeneration of the statocyst sensory epithelia.

Based on the damage postulated to have occurred through exposure to seismic signals in the wild and noise exposure in a laboratory, understanding the impact of aquatic noise, and seismic signals in particular, on the statocysts of marine invertebrates is an important aspect of characterizing the effects of exposure and the development of approaches to limit impact. This project will use electron microscopy to examine the statocysts of both Octopus pallidus and J. edwardsii following exposure to a full commercial seismic survey at varying distances.

Skills students will develop during this research project:

Organisation; review and synthesis of literature; scientific writing; data analysis; scientific/critical thinking; electron microscopy.

Authorised by the Executive Director, Institute for Marine and Antarctic Studies
February 25, 2021