The influence of flow velocity and food concentration on Lophelia pertusa (Scleractinia) zooplankton capture rates

Lophelia pertusa is the most significant framework building scleractinian coral in European seas, yet the reproductive strategy, longevity, growth and food capture rates for the species remain poorly understood. In this study an experimental investigation into the ability of L. pertusa to capture zooplankton from suspension was conducted. By direct ROV sampling approximately 350 L. pertusa polyps were collected from the Tisler reef, Norway and maintained under temperature controlled conditions in recirculating flumes. These polyps were subdivided into three replicate groups of ~ 120 polyps and maintained in waters with flow velocities of 2.5 cm s− 1 or 5.0 cm s− 1. Suspended Artemia salina nauplii food concentrations of between 345 and 1035 A. salina l− 1 were introduced. L. pertusa net capture rates were assessed by monitoring the reduction in suspended A. salina concentration in each flume over 24 h. Maximum net capture rates were higher in flumes with a 2.5 cm s− 1 flow regime, at 73.3 ± 2.0 A. salina polyp− 1 h− 1 (mean ± SD) than those with 5 cm s− 1 flow (19.8 ± 11.8 A. salina polyp− 1 h− 1). Maximum net capture rates were lower in flumes with A. salina densities of < 690 A. salina l− 1 than in flumes with higher food densities under comparable flow velocities. The maximum net capture rates observed represent maximum carbon capture rates of 66.4 ± 2.0 μg C polyp− 1 h− 1 and 17.9 ± 10.7 μg C polyp− 1 h− 1 under 2.5 and 5 cm− 1 s− 1 flow speeds respectively. The results of this study indicate that L. pertusa captures zooplankton more efficiently under slower flow velocities.