BENTHIC COMMUNITY-DEVELOPMENT IN ANTARCTICA - RECRUITMENT AND GROWTH ON SETTLEMENT PANELS AT SIGNY ISLAND

Identity, quantity and seasonal variation in recruiting invertebrate l arvae were investigated at Signy Island, Antarctica. Nine settlement p anels were deployed at each of three sites at depths ranging between f ive and 25 m over a two year experimental period. Longer-term communit y development was followed using three panels continuously immersed fo r up to 21 months at each site, with monthly photographs taken in situ . Shorter-term variations in recruitment were studied by regular repla cement of triplicate panels, which enabled the measurement of seasonal ity of recruitment onto artificial substrata in Antarctica, for the fi rst time. Cyclostomatid and cheilostomatid bryozoans, and spirorbinid polychaetes were the dominant colonising taxa both in terms of numbers and area covered. Very low rates of colonisation were observed: < 2% of the panels at 5 m, and < 6% of the panel areas at 25 m, were covere d after 15 months. Whilst little seasonality of recruitment was observ ed in spirorbinids, that of cheilostomatid bryozoans showed a signific ant peak between June and February. Successful recuitment levels of co lonising taxa suggested seasonal and interannual variation, although n ot conclusively. Measurement of growth of individual bryozoan colonies was assessed by image analysis of the in situ monthly photographs. Me an growth ranging between 1.7 mm(2) (Lacerna eatoni) and 7.1 mm(2) (Ar achnopusia inchoata) per month were recorded. There was considerable i nter- and intra-specific variation of growth of the encrusting cheilos tomatid species investigated and this is the first report of such meas urements having been made in Antarctica. (C) 1997 Elsevier Science B.V .