| Popis: |
‘Tufnol’ panels were immersed in Langstone Harbour to investigate seasonal settlement, growth and competition amongst the epibenthos and the structure and development of the epibenthic community. The panels were suspended parallel to, and 0.5 m above, the flat, muddy sea-bed in a minimum depth of 4.0 m and current speeds of 1.7 to 4.6 km/hr. Algal settlement was largely prevented by turbidity but 151 animal species have so far been identified. The majority of sessilespecies settled over a broad period (spring-autumn), some exhibiting more than one settlement peak, but panels initially colonised by winter settlers subsequently attracted little summer settlement and vice versa. Upper surface colonisation was dominated by species which tolerated silt deposition by displacing or outgrowing it (barnacles, erect bryozoans, hydroids), or forming temporary tubes within it (amphipods, polychaetes). The lower surfaces, however, although similarly colonised by barnacles and encrusting bryozoans initially, were soon characterised by compound ascidians which overgrew the early settlers and were in turn replaced by large solitary ascidians. After 4-8 months the lower surfaces were generally occupied by densely packed, pendulous ascidians supporting a prolific epifauna. These were major contributors to the total biomass of most well fouled panels and highest biomass values coincided with maximum development of the ascidian fauna. Encrusting sponges became significant only on panels immersed > 2 years, when peak abundance of the ascidians was passed. |
