Port of Thursday Island Long Term Seagrass Monitoring March 2004.

Ross Thomas and Michael Rasheed, Queensland Department of Primary Industries and Fisheries.

QDPI&F Information Series Q104082.

Seagrass habitats are valuable fisheries resources that show measurable responses to
changes in water quality. These attributes make seagrass meadows ideal candidates for monitoring the long-term health of marine environments. Successful long-term seagrass monitoring programs are currently conducted at various port locations throughout Queensland. Results from these monitoring programs have enabled port managers to make informed decisions regarding planning and development of port infrastructure. This has allowed continued expansion and growth of port facilities with minimal impact on the marine environment.

A baseline survey of seagrass habitat was conducted at the Port of Thursday Island in
March 2002. That survey identified some of the best examples of intertidal and subtidal
seagrass habitat that have been found in Queensland port environments. From that baseline survey nine seagrass meadows were selected for long-term monitoring. The meadows selected were representative of the range of seagrass communities identified in the baseline survey and were also located in areas likely to be vulnerable to impacts from port operations and developments. This current survey represents the first of planned annual long-term seagrass monitoring surveys of these selected meadows for the port of Thursday Island. In this survey, seagrass above ground biomass, individual meadow area and species composition (community types) were measured for comparison with the baseline survey.

Results from this survey indicated that seagrass communities at the Port of Thursday Island were healthy. Significant increases in seagrass biomass were recorded for four of the nine monitoring meadows since the March 2002 baseline survey. Seagrass areas of the nine monitoring meadows were all within the ranges previously recorded in March 2002. Minor changes in community type and species composition of several monitoring meadows were identified but these were likely a reflection of greater sampling intensity during the current survey rather than these species being absent from the meadows in 2002. Results from this survey were consistent with favourable regional climatic conditions for seagrass growth since the baseline survey. There were no apparent anthropogenic impacts from port operations or developments that influenced seagrass growth at Thursday Island since March 2002.

For a full copy of this report contact QDPI&F on 07 4035 0112 or michael.rasheed@dpi.qld.gov.au