Habitat requirements

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).

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