The Baltic Exchange's main sea freight index, which tracks rates for ships carrying dry bulk commodities, slipped on Wednesday.
The index, which factors in the average daily earnings of capesize, panamax, supramax and handysize dry bulk transport vessels, fell 3 points, or 0.53 percent, to 565 points.
The Baltic's capesize index fell 26 points, or 5.69 percent, to 431 points.
"A cyclone outside Australia is threatening to close the Dampier port and as a consequence miners are withdrawing from booking vessels as their schedules are unclear," RS Platou Markets analyst Frode Morkedal said in a note on Wednesday.
Average daily earnings for capesizes, which typically transport 150,000-tonne cargoes such as iron ore and coal, fell $242 to $4,357.
The panamax index slipped 3 points, or 0.51 percent, to 588 points
Average daily earnings for panamaxes, which usually carry 60,000- to 70,000-tonne cargoes of coal or grains, slipped $22 to $4,710.
(Reporting by Anupam Chatterjee in Bengaluru; Editing by Mark Potter)