Elemental composition and productivity of cyanobacterial mats in an arid zone estuary in north Western Australia

Extensive cyanobacterial mats are a feature of the high intertidal zone in the Exmouth Gulf, Western Australia. This study provides a description of the position of the mats within the intertidal zone and of the mats elemental composition and productivity. We found that the mats occupied 40 cm elevational range within the intertidal zone. They have a mean organic matter content of 1,600 g m(-2). Mean concentrations of nitrogen (N) were 1.82 g kg(-1) and phosphorus (P) 205 mg kg(-1). N:P ratio was 19.7 indicating P limitation, but N:P was variable. Rates of photosynthesis and biomass production were similar to those reported for mats in hypersaline conditions at other sites. When photosynthetic production was scaled-up for the region our data suggest that cyanobacterial mats are an important contributor to the carbon budget in the Exmouth Gulf, contributing between 5 and 15% of the total carbon fixed by primary producers. Additionally mats were observed to be a source of soluble carbohydrates in tidal waters indicating that fixed carbon from high intertidal cyanobacterial mats may enter near shore food webs through this pathway

Seagrasses, fish and fisheries

Seagrass meadows have extremely high primary and secondary productivity and support a great abundance and diversity of fish and invertebrates. A number of commercially and recreationally important species (including both fish and invertebrates) have been linked to seagrass at some stage of their life cycle, although few such species use seagrass throughout their life. Non-commercial species within seagrass may be an important food source for commercial species (forming trophic linkages). In addition, some species that do not inhabit seagrass may derive benefit from seagrass by way of exported seagrass detritus or resident/transient species that move out of seagrass (some of these topics are dealt with elsewhere in this volume: e.g. Heck and Orth, Chapter 22, Kenworthy et al., Chapter 25 and Bell et al., Chapter 26). © 2006/2007 Springer. All Rights Reserved.http://trove.nla.gov.au/work/1348907