| Habitat factor |
Range of conditions |
| Salinity |
Full The seapens Pennatula phosphora and Funiculina
quadrangularis, appear to require full or close-to full salinity. Where they occur in
enclosed waters, it is most likely that fresh-water influence is restricted to shallow
surface waters. Virgularia mirabilis however appears to be somewhat more tolerant
of occasional lowing of salinity. |
| Wave exposure |
Sheltered, Very sheltered, Extremely sheltered (CMU.SpMeg) |
| Tidal streams |
Weak, Very weak |
| Substratum |
Mud, Mud with some shell gravel (CMU.SpMeg) |
| Zone |
Circalittoral |
| Depth range |
10-200 m |
| Temperature |
Biotopes, which include the seapens Pennatula phosphora
and Funiculina quadrangularis appear to require thermally, stable conditions and
may thrive especially deeper than thermoclines. They most likely occur where annual
temperature variability is between 5 and 15 ° C. Biotopes with
Virgularia mirabilis only may be subject to higher temperatures as they occur in
shallower waters. |
| Water quality |
The seapen biotopes considered here typically occur in depths
below 15 m in wave-sheltered sealochs and much deeper in the open sea suggesting that
water movement is more important to their existence than light. However, species within
the biotopes are most likely very sensitive to light. The Norway lobster Nephrops
norvegicus is most active at night in shallow depths and during the day in deep water,
suggesting that a particular level of light is of critical importance. The red band fish Cepola
rubescens feeds at dawn and dusk (Atkinson & Pullin 1996). |
| Nutrients |
Seapen biotopes seem able to tolerate natural and enhanced
levels of nutrients. Both Virgularia mirabilis and Pennatula phosphora were
found to be abundant and the |
| |
sediment macrofauna apparently little affected, near to a
distillery outfall enriched |
| |
with organic compounds and where sediment organic carbon
content was <5% (Nickell & Anderson 1997). Along an organic enrichment gradient
associated with sewage sludge dumping, the burrowing decapods associated with seapen
communities were found to be abundant in areas of <4% organic carbon, and absent where
this exceeded 6% Smith (1988). However, where organic enrichment causes or contributes to
hypoxia, effects can be severe with burrowing species abandoning their burrows and
exposing themselves to predation (for instance, Stachowitsch 1984). |
