Antarctic macrobenthic communities : A compilation of circumpolar information 1 Antarctic macrobenthic communities : A compilation of circumpolar information

Comprehensive information on Antarctic macrobenthic community structure has been publicly available since the 1960s. It stems from trawl, dredge, grab, and corer samples as well as from direct and camera observations (Table 1–2). The quality of this information varies considerably; it consists of pure descriptions, figures for presence (absence) and abundance of some key taxa or proxies for such parameters, e.g. sea-floor cover. Some data sets even cover a defined and complete proportion of the macrobenthos with further analyses on diversity and zoogeography. As a consequence the acquisition of data from approximately 90 different campaigns assembled here was not standardised. Nevertheless, it was possible to classify this broad variety of known macrobenthic assemblages to the best of expert knowledge (Gutt 2007; Fig. 1). This overview does not replace statistically sound community and diversity analyses. However, it shows from where which kind of information is available and it acts as an example of the feasibility and power of such data collections. The data set provides unique georeferenced biological basic information for the planning of future coordinated research activities, e.g. under the umbrella of the biology program “Antarctic Thresholds Ecosystem Resilience and Adaptation” (AnT-ERA) of the Scientific Committee on Antarctic Research (SCAR) and especially for actual conservation issues, e.g. the planning of Marine Protected Areas (MPAs) by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).


General description
Additional information: Additional files uploaded: list of references (Table 1-2) and classification of macrobenthic communities (Fig. 1).

project details
Project title: Antarctic macrobenthic communities: A compilation of circumpolar information.

Taxonomic coverage
General taxonomic coverage description (for detailed information see references in Table 1): Macrobenthic communities have been uploaded in the category "vernacu-larNames", abbreviations in "taxonRemarks". "Sessile suspension feeders and associated fauna" can be dominated by both demosponges, e.g., Cinachyra or Mycale and hexactinellid (glass) sponges. The most common genus is Rossella. The sponges include fast growing genera, such as Homaxinella or those that grow slowly, at least during the adult life stage, such as the also common hexactinellid genus Anoxycalix. The associated fauna comprises specialised predators, such as nudibranches, asteroids (especially Acodontaster conspicuous and Perknaster fuscus, which control fast growing Mycale acerata populations) and gastropods. Other fauna groups are symbionts, amphipods and other macroorganisms that prefer an epibiotic life-mode (mainly from the echinoderms, such as sedentary holothurians, ophiuroids and crinoids). If space is not monopolised by sponges, then, cnidarians (such as gorgonians, pennatularians, alconarians or hydrocorals), solitary and compound ascidians, and a variety of bryozoans can be most abundant. A recently described population of lithodid crabs is speculated to grow fast due to oceanic warming and was associated with the "mobile deposit feeders, infauna and grazers". Other mobile epifauna assemblages can be dominated in shallow areas by the asteroid Acodontaster validus, by two species of the grazing echinoid Sterechinus, a variety of deposit feeding and scavenging ophiuroids and mobile holothurians. The infauna is comparably rare; however, polychaetes and the clams Yoldia as well as Laternula can reach high densities, especially in shallow muddy sediments. A general depth gradient exists for biomass and abundances. In addition, very low biomass and abundances are found in shallow habitats that are physically and permanently disturbed by sea-scour, in intermediately deep shelf areas that are scoured by icebergs and in extremely oligotrophic situations under or close to the ice-shelves. Intensively disturbed assemblages can be dominated by very few species, appearing to be almost "monospecific", during recolonisation by pioneers such as the ascidian Mogula pedunculata, bryozonas like Cellarinella and Cellaria or the gorgonian Primnoisis antarctica or in physically disturbed areas, where only opportunistic mobile species survive. Locally clams of the species Adamussium colbecki can live in several layers on top of each other simply due to suitable environmental conditions and low competition. Species can also become very abundant when they are better local competitors for space, such as the demosponge Cinachyra barbata, s.l. Recently, fauna-rich vent sites and far poorer seeps have been discovered.

Spatial coverage
General spatial coverage: The study area generally covers almost the entire Southern Ocean, including single ice-shelf covered sites (Fig. 2). 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 edge. 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. Overdeepened 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 thought to be specifically adapted to, and very little terrestrial run-off. Most of the shelf-inhabiting macrobenthic species are endemic; some taxa reach above-average species richness (Clarke and 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 but require good scientific knowledge and data to be meaningful.

Method step description:
Attribution of the information from the different sources (for references see Table 1, for hyperlinks see Table 2) to the classified macrobenthic assemblages ( Fig. 1) was done to the best of expert knowledge. This was done for the entire data set simultaneously and the results were made publically available for the first time via the database "Antarctic Biodiversity Facility" (ANTABIF). 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 iceberg scouring, epi-biotic life-mode and oligotrophic conditions under ice shelves. The source publications listed (Table 1) comprise descriptions of catches, other observations, and data on fauna and were mainly from historical and modern peer-reviewed articles. Other information sources were sea-bed videos and still images together with associated meta-data (Table 2). All the latter source material has an associated DOI and is available at the database PANGAEA (www.pangaea.de). Study extent description: Southern Ocean with emphasize on coastal shelf areas and some islands without specific temporal patterns of sampling.
Sampling description: 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 (Table 1) or data repositories (Table 2).
Quality control description: 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. Data presented here is available at ANTABIF/SCAR-MarBIN and will contribute to the biogeographic atlas project of SCAR and the Census of Marine Life (De Broyer et al. in prep.), http://atlas.biodiversity.aq/).