Demography, Ecology, and Management of Sea Star Populations: Introduction to a Special Issue in The Biological Bulletin.

Sea stars (Echinodermata: Asteroidea) are one of the most recognizable and iconic organisms in the marine environment. With nearly 1900 extant species from 370 genera, grouped into 36 families, sea stars are considered one of the most diverse groups of extant echinoderms (Mah and Blake, 2012. PLoS One 7: e35644; O’Hara and Byrne, 2017. Echinoderms: Biology, Ecology and Evolution). This special issue focuses on ecologically important keystone species, including the crown-of-thorns sea star (Acanthaster sp.), which is present in tropical and subtropical waters; the temperate species the northern Pacific sea star (Asterias amurensis), the ochre sea star (Pisaster ochraceus), and the sunflower sea star (Pycnopodia helianthoides) from the north Pacific; and the spiny sea star (Marthasterias glacialis) from the north Atlantic. Seminal work by Professor Robert Paine demonstrated that the removal of a top predator, Pisaster ochraceus, can alter the diversity, abundance, and distribution of other organisms within an ecosystem—giving rise to the concept of “keystone species” (Paine, 1966. Am. Nat. 100: 65–75). Subsequent studies have further revealed the role of sea stars as important predators in intertidal and subtidal ecosystems, as well as the influence of demographic and environmental factors on predator-prey interactions (reviewed by Menge and Sanford, 2013. Ecological role of sea stars from populations to meta-ecosystems. Pp. 67–80 in Starfish: Biology and Ecology of the Asteroidea). The ecological and economic ramifications of irruptions of, or the collapse of, sea star populations have been well documented. For example, outbreaks of the corallivore Acanthaster sp. have led to widespread mortality of reef corals in the Indo-Pacific (Chesher, 1969. Science 165: 280–283; De’ath