Ratio-based trophic niche breadths of fish, the Sheldon spectrum, and the size-efficiency hypothesis

Abstract

Measurements were made of benthic microalgal biomass (chlorophyll mg m-2) and concentration (chlorophyll, pg g-' dry welght of sediment) from the Peel-Harvey estuarine system, Western Austral~a. Most chlorophyll was In the top 1 cm of s e d ~m e n t , and less than 10 % of chlorophyll a was non-functional as determined by hexane extraction. Highest biomass occurred at shallow sites and on coarse sandy sedlments. Biomass was hlgher In Harvey (202 mg m-2) than Peel ( l 0 7 nlg m r 2 ) in summer when there was a large population of macroalgae In Peel; biomass was s ~m i l a r in winter (Harvey 163 m g m-2. Peel 151 mg m-2). Biomass increased w ~t h the onset of riverine nutrient input and decreased when blooms occurred in the water column. Except during Nodularia blooms, the biomass (chlorophyll) of b e n t h ~c m~croalgae greatly exceeded ( e g 40 times) the biomass of chlorophyll In the water column above. In summer much of the chlorophyll of the water column was d u e to wlnd st~rrlng of benthic m~croalgae. The poss~ble importance of benthic mlcroalgae to the productlvlty of shallow systems is emphasized.