benthos

Abstract Nineteen species of the rare polychaete genus Heterospio are reported, 15 of which are new to science. The status of H. longissima Ehlers, 1874, the type-species, is reviewed. The specimens examined are from several locations in the North Atlantic Ocean, Gulf of Mexico, Caribbean Sea, off Br azil, the Indian Ocean, the Pacific Ocean off California, New Zealand, Australia, and the South China Sea. Deep-water samples from the western North Atlantic Ocean collected by the late Drs. H.L. Sanders and R.R. Hessler that were reported by Hartman as H. longissima were re-examined and referred to two new species, H. hartmanae n. sp. (abyssal depths, New England to Bermuda transect) and H. guiana n. sp. (bathyal depths off Suriname). Other materials from the Sanders/Hessler North Atlantic collections were also examined and referred to two additional species, H. canariensis n. sp. (deep water off Canary Islands) and H. southwardorum n. sp. (Bay of Biscay) as well as H. cf. reducta from off SW Ireland in bathyal depths. New collections from the North Atlantic region include additional materials of H. hartmanae n. sp. (deep water off the Mid-Atlantic and SE USA), H. aruba n. sp. (Caribbean Sea), H. bathyala n. sp. (deep water off SE USA), and H. dibranchiata n. sp. (deep water, Gulf of Mexico). Heterospio paulolanai n. sp. is from shelf depths off southeastern Brazil. Heterospio knoxi n. sp. is from the North Island of New Zealand, H. ehlersi n. sp. is from the Gulf of Thailand, in the South China Sea, H. bidentata n. sp. is described from deep water in the Coral Sea off eastern Australia, and H. alata n. sp. and H. brunei n. sp. are described from deep water off the Island of Borneo in the South China Sea. Heterospio africana n. sp. and H. antonbruunae n. sp. are described from off east Africa in the Mozambique Channel. New records and descriptions of H. catalinensis, H. indica, and H. peruana are presented. The 15 new species reported here nearly triple the number of previously known species of Heterospio, with 23 species now recognized. All known species are tabulated and compared

Over the past decades, numerous studies have reported declines in stony corals and, in many cases, phase shifts to fleshy macroalgae. However, long-term studies documenting changes in other benthic reef organisms are scarce. Here, we studied changes in cover of corals, algal turfs, benthic cyanobacterial mats, macroalgae, sponges and crustose coralline algae at four reef sites of the Caribbean islands of Curaçao and Bonaire over a time span of 40 years. Permanent 9 m2 quadrats at 10, 20, 30 and 40 m depth were photographed at 3 to 6-year intervals from 1973 to 2013. The temporal and spatial dynamics in the six dominant benthic groups were assessed based on image point-analysis. Our results show consistent patterns of benthic community change with a decrease in the cover of calcifying organisms across all sites and depths from 32.6% (1973) to 9.2% (2013) for corals and from 6.4% to 1% for crustose coralline algae. Initially, coral cover was replaced by algal turfs increasing from 24.5% (1973) to 38% around the early 1990s. Fleshy macroalgae, still absent in 1973, also proliferated covering 12% of the substratum approximately 20 years later. However, these new dominants largely declined in abundance from 2002 to 2013 (11% and 2%, respectively), marking the rise of benthic cyanobacterial mats. Cyanobacterial mats became the most dominant benthic component increasing from a mere 7.1% (2002) to 22.2% (2013). The observed increase was paralleled by a small but significant increase in sponge cover (0.5% to 2.3%). Strikingly, this pattern of degradation and phase change occurred over the reef slope down to upper-mesophotic depths of 40 m. These findings suggest that reefs dominated by algae may be less stable than previously thought and that the next phase may be the dominance of slimy cyanobacterial mats with some sponges.

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