Critical Information Gaps Impeding Understanding of the Role of Larval Connectivity Among Coral Reef Islands in an Era of Global Change

Abstract

Populations of marine organisms on coral reef islands (CRI) are connected in space and time by seawater that transports propagules of plants, animals, and algae. Yet, despite this reality, it is often assumed that routine replenishment of populations of marine organisms on CRI is supported by locally-sourced propagules (hereafter, larvae). Following large disturbances, however, distantly-sourced larvae from less disturbed CRI within a regional meta-population are likely to be important for local population recovery, but evaluating the roles of locally- vs. distantly-sourced larvae remains difficult. While larval sources are relatively well-known for some fishes, they remain virtually unknown for most taxa, particularly those associated with the benthos, as exemplified by scleractinian corals. This review focuses on reef recovery and larval connectivity. Using corals as examples, we argue that CRI can serve as natural laboratories in which studies of these issues can enhance understanding of coral reef community dynamics under future disturbance regimes. Rather than focusing on synthesizing empirical data, we focus on the capacity for CRI to realize their potential in this research area, concluding that progress is impeded by the limited breadth, detail, and spatio-temporal concordance of existing research. Using long-term observational programs of coral reefs in Mo’orea (French Polynesia), Okinawa (Japan), and St. John (US Virgin Islands) as examples of the data currently available, we make the case that new modes of multidisciplinary and collaborative research will be required to exploit the value of CRI in understanding the role of connectivity in mediating ecosystem resilience in a future affected by anthropogenic disturbances.