Robertson Rc Dar~iel ms). antl the total arinual flux of wood through the bay is therelore .... Bull. Amer. Ass. Petroleum. Geologists 69: 1230- 1240. Robertson.
Proceedings of the 6th International Coral Reef Symposium, Australia, 1988, Vol. 2 H O W M U C H M A N G R O V E DEI'RITUS ENTERS I ' H E G R E A T BARRIER REEF LAGOON? A.I. ROBERTSON, D.M. A L O N G I , P.A. D A N I E L A N D K.G. B 0 1 ' 0 Australian Institute o f Marine Science P M B No. 3. Townsville M C . . Qld. 4810. Australia
ABSTRACT I n Missionary Bay on Hinchinbrook Island i n tropical northeastern Australia, there is one o f the largest mangrove forests i n the region (50 km2). Annual input o f mangrove litter (leaves. stipules and reprotluctive parts) from these forests into the bay was estimated to be 12593 tonnes Carbon. Surveys of the quantity o f mangrove tletritus on the bottom of the bay showed a mean annual biomass o f 15.8 (95% C.L. 7.8-23.8) tonnes C o f litter ant1 12.4 (6.5-18.3) tonnes C o f wood detritus. Annual flux o f litter detritus through Missionary Bay was 70 tonnes C. By difference 12523 tonnes C. are exported out of the bay into the Great Barrier Reef (GBR) lagoon. We estimate that this detritus is deposited over an area o f 260 km2. ant1 there is thus an input o f -25.8 gC.m-2.y-1o f mangrove litter to the benthos of the lagoon. Together with a similar contribution from other nearby forests tliis repl-esents - 1 3 % o f the requirement for sediment bacterial production (-400 gC.m-2.y-1) ant1 47% of tlie benthic oxygen consumption (-1 10 gC.m-2.y-l) i n the lagoon. These estimates are likely to be near the upper limits for the influence o f "outwelled" marigrove detritus on adjacent systems in north-eastern Australia. Phytoplankton cell settlement and riverine inputs o f organic matter are probably the major sources of carbon for demersal footl chains i n the GBR lagoon. INTRODUCTION The Great Barrier Reef (GBR) lagoon (the body of water bortlered by the mainland o f Australia to the west antl the Great Barrier Reef to the east) supports highly productive clemersal fisheries. particularly for prawns. scallops ant1 slipper lobsters (Dredge 1988). Although the population dynamics and life history attribules o f many o f the harvested species have recently been investigated (see Dredge 1988) there has been no work on the food chains supporting these i~nportantresources. There are four likely sources o f primary protluction supporting benthic rood chains in the GBR lagoon. 111 sit11 production may be provitletl by seagrasses or I~enlliicalgal mats. However. i n tlie GBR lagoon seagrass meatlows are usually found in only shallow (< 10 m ) waters. ant1 even then have low standing stocks (
