Antarctic macrobenthic communities: A compilation of circumpolar information

Study Extent

Southern Ocean with emphasize on coastal shelf areas and some islands without specific temporal patterns of sampling.

Sampling

This project aggregates data from various expeditions with a full range of benthic sampling methods, such as grabs, corers, dredges, and trawls as well as non-invasive observations by scuba divers, stationary, towed, or ROV-based still and video-cameras. For detail descriptions see original publications in journals or data repositories (Table 1).

Quality Control

A first version of the classification of the macrobenthic communities had been published in a peer-reviewed journal (Gutt 2007). A modified version had been published in the Antarctic Climate Change and the Environment report (ACCE, Turner et al. 2009). The actual version is depicted in Fig. 1.

Method steps

1. Attribution of the information from the different sources (for references see Table 1) to the classified macrobenthic assemblages (Fig. 1) was done to the best of experts knowledge. The principal parameter, on which theses assumptions have been made was biomass or a proxy for biomass such as sea-floor coverage. Some information on benthic functioning is also included directly or indirectly, e.g. predation, competition, succession after ice-berg scouring, epi-biotic life-mode and oligotrophic conditions under ice shelves.

Macrobenthic communities have been uploaded in the category "vernacularNames", abbreviations in "taxonRemarks".

1. sessile suspension feeders with associated fauna
   common name: SSFA
2. sessile suspension feeders with associated fauna - predator driven
   common name: SSFA-PRED
3. sessile suspension feeders with associated fauna - dominated by sponges
   common name: SSFA-SPO
4. sessile suspension feeders with associated fauna - dominated by others than sponges
   common name: SSFA-OTH
5. mixed assemblage
   common name: MIX
6. very low biomass or absence of trophic guilds
   common name: VLB
7. "monospecific"
   common name: MONO
8. physically controlled
   common name: PHYCO
9. mobile deposit feeders, infauna and grazers
   common name: MOIN
10. mobile deposit feeders, infauna and grazers - infauna dominated
    common name: MOIN-INF
11. mobile deposit feeders, infauna and grazers - epifauna dominated
    common name: MOIN-EPI
12. vent
    common name: VENT
13. seep
    common name: SEEP

The area generally covers almost the entire Southern Ocean, including some ice-shelf covered sites. The vast majority of information is from shelf areas around the continent at water depth shallower than 800m. Non-ice shelf covered shelf areas can be up to 300km wide or the shelf-edge at 600 to 800m depth can "disappear" beneath the floating ice-shelf. Shallow areas (<50m) are rare because 86% of the coast-line is glaciated or consists of an ice-shelf egde. A non-glaciated coast mainly exists along the Antarctic Peninsula. The coastline is either extremely complex with bays, channels , peninsulas, islands etc or less structured, especially where it is formed by the ice-shelf. Overdeepenend basins (inner-shelf depressions) can reach >1200m water depth. Most islands exist west of the Antarctic Peninsula and along the Scotia Arc linking the Peninsula with the southern tip of South America. The coastal waters are mainly affected by the Antarctic Coastal Current (East Wind Drift), whilst the largest off-shore part of the Southern Ocean is dominated by the Antarctic Circumpolar Current (West Wind Drift) with gyres of different size. Sediments are predominantly poorly sorted but also cobble "fields", bedrock and pure soft sediments exist. The Antarctic marine ecosystem is shaped by a distinct seasonality of the sea-ice cover affecting a short and intensive primary production in austral summer, by predominantly stable low temperature to which most organisms are specifically adapted and almost missing terrestrial run-off. Most of the shelf-inhabiting macrobenthic species are endemic; some taxa reach above-average species richness (Clarke & Johnston 2003). Only few marine habitats are protected, most of which are small. Plans and proposals for large Marine Protected Areas (MPA's), e.g. in East Antarctica, in the Ross and Weddell Seas exist and demand good scientific knowledge and data.