Sex analysis in marine biological systems: insights and opportunities

The ocean is facing unprecedented challenges with the escalating impacts of climate change and other pressures threating ecosystems and the many benefits they provide. Effective strategies for reversing the loss of biodiversity and ecosystem services rely on knowledge of how marine organisms, populations, and communities respond to environmental change. A fundamental, but often overlooked biological characteristic of organisms is biological sex – which is distinct from sociocultural gender. Here, we address: a) how sex influences the physiology, behavior and ecology of marine organisms, populations, and communities; b) how this knowledge is generated in current marine biology research; and c) how sex analysis may be more broadly applied in future research. Through review of sex analysis applications in marine biological research we find that sex broadly affects the morphology, physiology, behavior, and distribution of organisms and population across taxa, with evidence of sex-specific differences in survival to thermal stress, timing of biological mechanisms, and energetics. Sex analysis reveals pervasive effects of sex on a suite of biological processes and scales of biological organizations. We found that sex analysis is most commonly applied to studies of organisms’ life history traits and population dynamics, but possible effects on communities are rarely addressed. Existing evidence of sex-based differences across taxa and biological levels of organization highlights that including sex as a biological variable in research is essential to understanding marine systems and their responses to environmental change. To facilitate future integration of sex into marine biological research, we synthesize current approaches, propose solutions to methodological and logistical challenges, and lay out guidelines for future research.