Structure-Forming Corals and Sponges and Their Use as Fish Habitat in Bering Sea Submarine Canyons

Robert J Miller,Dmitry V Fedorov,John Hocevar,Robert P Stone,John Murray Roberts

doi:10.1371/journal.pone.0033885

Abstract

Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide.

Highlights

Autogenic ecosystem engineers, such as trees or corals, modify habitats through their physical presence [1]
Comparison of species distribution patterns with respect to potential functionally equivalent habitats, e.g. corals versus rock outcrops, can provide a better indication of the importance of autogenic engineers to associated species compared with simple observations of high densities around corals [20]
Study sites Zhemchug and Pribilof Canyons are enormous submarine canyons cutting into the continental slope under the northeastern boundary of the Aleutian Basin, southeastern Bering Sea

Summary

Introduction

Autogenic ecosystem engineers, such as trees or corals, modify habitats through their physical presence [1]. Unlike shallow-water systems, where the processes connecting habitat with populations and communities of dependant organisms are relatively well understood, the role of habitat structure, including that of autogenic ecosystem engineers, in deep-water communities is still unclear due to lack of small-scale observational and experimental studies [14]. Biogenic structure can affect populations of associated animals through habitat selection at settlement, differential survival, and post-settlement migration [15,16,17]. The result of these processes is elevated abundances of benefited organisms associated with the habitat feature in question. Comparative approaches, no matter how well designed, will not shed much light on mechanisms of habitat effects on associated organisms; such approaches are crucial for informing managers and designing future experimental work

Methods

Results

Conclusion