Port disturbance of the meiofauna and sediment biogeochemistry at the mouth of the Brisbane River, eastern Australia

Abstract

The Port of Brisbane disturbance of the sedimentary environment at the mouth of the Brisbane River was assessed at the inner and outer river and in two periods following disturbance: 2 weeks (March) and 8 months (November) after dredging. Sediments in the inner river were dominated by silt, while in the outer river sediment were sandier. Total and organic carbon (TC and Corg) and total Kjeldahl nitrogen (TKN) were higher in the inner river, which could be an indication of higher organic loads. Ammonia (NH 4-N) and nitrate (NO 3-N) sediment profiles indicated suboxic conditions and denitrification in the inner river, as well as oxic conditions and nitrification at the outer river. Total meiofauna abundance and taxa composition was similar in both, the inner and outer river locations. For some individual taxa however, the suboxic sedimentary conditions in the inner river were adverse. Copepods, polychaetes and sipunculids abundance were lower in the inner river, and negatively correlated with fine sediments and high organic loads, and positively correlated with oxic conditions. Furthermore, the port strategic dredging operations had negative effects on the meiofauna of both locations. The abundance of most of the taxa in both the inner and outer river locations during March was lower at sites inside the dredged navigational channel than at the sites outside the channel. The meiofauna rapidly re-colonise the disturbed sediments as by November the abundances inside the channel considerably increased. The composition of the meiofaunal and nematode assemblage from different sites and months showed significant differences. The nematode assemblage at the mouth of the Brisbane River dominated by Sabatieria and Metalinhomoeus was characteristic of disturbed sediments.