Benthic Microalgal Community Structure, Primary Productivity, and Fiddler Crab (Leptuca pugilator) Grazing in an Estuarine Salt Panne

Salt pannes are marsh features in the supratidal zone that are devoid of macrophytic vegetation. Although these habitats appear barren, benthic microalgae (BMA) inhabit the sediments and are potentially important primary producers. In addition, salt pannes are habitats for dense accumulations of sand fiddler crabs (Leptuca pugilator; Bosc 1802). The purpose of this study was to determine the temporal changes in BMA biomass, community composition, and net primary productivity (NPP) for a supratidal salt panne and quantify sand fiddler crab grazing on BMA. The impact of crab grazing on BMA abundance in surface sediments was determined by measuring chl a concentrations in ungrazed and grazed sediments. BMA biomass peaked to a high of 16 mu g chl a g sediment(-1) in June and July, suggesting growth in the spring followed by a small decline in the warmer summer months. The BMA community was primarily composed of benthic diatoms, with lesser amounts of cyanobacteria. NPP increased to a median of 0.51 mmol O-2 m(-2) h(-1) (6.12 mg C m(-2) h(-1)) in July. In comparison with other BMA habitats in this estuary, NPP and biomass for salt pannes was lower than the other 5 habitat types (tall and short Spartina, intertidal mud and sandflats, phytoplankton, and submerged sediments). Sand fiddler crabs do not appear to consume significant amounts of BMA during grazing in salt pannes. This first ever study of BMA NPP demonstrates that estuarine salt pannes are likely a small contributor to ecosystem NPP.

Automated summary

The purpose of this study was to examine the temporal changes in biomass, community composition, and net primary productivity (NPP) of benthic microalgae (BMA) in a supratidal salt panne. The study found that BMA biomass peaked in June and July, primarily composed of benthic diatoms. NPP reached its peak in July, but was lower compared to other BMA habitats.