Photosynthetic activity of an epiphytic diatom, gomphonema novo‐zelandicum, and its carpophyllum (phaeophyta) hosts

Abstract

Net photosynthetic activities of epiphytic Gomphonema novo‐zelandicum diatoms and Carpophyllum maschalocarpum and C. flexuosum hosts from the littoral fringe at sites from the Wai‐temata Harbour. Auckland, New Zealand, were determined using infra‐red gas analyser, Winkler and ¹⁴C bicarbonate techniques. Gomphonema displayed a mean assimilation number of 1.970 and volumetric activity of 16.714 mg Ccrrr'rr¹ while mean rates for host primary leaves freed of diatoms and corrected for the effects of emersion were 0.873 mg C (g DW)^‐1h ¹for C. maschalocarpum and 1.266 mg C(g DW)^‐1h^‐1 for C. flexuosum. These activities when considered together with seasonal primary “leaf” and vertical primary axis diatom population densities indicated a 6–8% contribution by Gomphonema to the total photosynthetic activity of the host‐epiphyte association. On a volumetric basis, however, the diatoms displayed an activity which was 67 and 45 times higher than that of the C. maschalocarpum and C. flexuosum host material respectively.

Keywords:

• photosynthetic activity
• epiphytic
• Gomphonema novo‐zelandicum
• Carpophyllum maschalocarpum
• C. flexuosum