Damselfish territories: zones of high productivity on coral reefs

Abstract

ABSTRACT: Temtories of 4 species of herbivorous damselfish from coral reefs of the central Great Barrier Reef and Motupore Island, Papua New Guinea were shown to be zones of high algal biomass and primary productivity relative to surrounding epilithic algal communities. Productivity was rnea- sured in the field from die1 patterns in oxygen flux, employing in situ data-logging respirometers. Algal communities inside territories were 1.6 to 3.4 times more productive per surface area than surrounding algal substrata. Algal communities of damselfish territories maintain a rate of productivity per unit biomass 1.5 to 3.4 times hgher than that of algae growing outside the territories. Differences in primary productivity for the 2 different types of algal community are due to the higher photosynthetic efficiency (0.37 to 0.94 pg O2 PE-') and potential maximum rate of photosynthesis (57 to 249 pg Oz cm-2 h-') of algae from territories compared with algae of non-territory areas (0.20 to 0.35 pg O2 and 24 to 78 pg O2 cm-2 h-', respectively). Photosynthetic compensation and saturation irradiance were similar for the 2 algal communities and ranged from 52 to 100 and 337 to 735 PE m-' S-', respectively. These temtories are shown to be important to reef net productivity since they cover a high proportion of the reef flat zones examined (up to 77 % of substratum). Several hypotheses are proposed to account for the significantly higher rates of primary productivity inside coral reef damselfish territories compared with adjacent substrata.