An early occurrence of Sarcophilus laniarius harrisii (Marsupialia, Dasyuridae) from the early Pleistocene of Nelson Bay, Victoria

The isolated lower molar series of a dasyurid from early Pleistocene sediments at Nelson Bay, near Portland, is referred herein to Sarcophilus laniarius harrisii (Boitard, 1842). Dental measurements and morphological comparisons taken from this tooth series compare closely with those of the extant subspecies. The genus Sarcophilus is known from the early Pleistocene by the species S. moornaensis Crabb 1982. Fossil material assigned to S. laniarius harrisii is now also known from Early Pleistocene sediments. The new specimens from Nelson Bay extend the origin of S. laniarius harrisii to the early Pleistocene.

Paleoreconstruction of estuarine sediments reveal human-induced weakening of coastal carbon sinks

Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO 2. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney - the site of European settlement of Australia - to look for human-induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (~6000 years) according to 210Pb profiles and radiocarbon ( 14C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 30-50 years were considerably higher than during the rest of the Holocene. C : N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of 12C/ 13C showed that the relative contribution of seagrass and C 3 terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (~1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication. Given the lower carbon burial efficiencies of microalgae (~0.1%) relative to seagrasses and C 3 terrestrial plants (up to 10%), such changes represent a substantial weakening of the carbon sink potential of Botany Bay - this occurrence is likely to be common to human-impacted estuaries, and has consequences for the role these systems play in helping to mitigate climate change. © 2011 Blackwell Publishing Ltd.

Denitrification measurements of sediments using cores and chambers

Denitrification is commonly measured using in situ benthic chambers or laboratory incubations of sediment cores. These techniques are similar in principle but differ considerably in cost and practicality. Despite widespread use of both techniques, it is uncertain whether they give comparable results. We compared cores and chambers for measuring fluxes (dissolved oxygen [DO], N 2, NH4+, NO3- and NO 2-) and denitrification efficiency at 2 sites in Port Phillip Bay, Victoria, Australia. Overall, denitrification efficiency was not significantly different between cores and chambers, but fluxes of DO, NO 3- and NO2- differed. Chambers demonstrated higher levels of oxygen consumption and net fluxes of NO 3- and NO2- out of the sediment, suggesting that denitrification and nitrification were closely coupled. In contrast, there was a greater relative importance for uncoupled denitrification in cores as indicated by reduced oxygen consumption and net fluxes of NO 3- into the sediment. We conclude that cores and chambers give different flux results and therefore are not comparable techniques for measuring denitrification. To ascertain the cause of this, we tested the hypothesis that cores failed to adequately incorporate the impacts of macrofauna on fluxes, due to the small size of cores relative to chambers. However, densities of macrofauna were not significantly different in cores and chambers. We then hypothesised that disturbance during core collection, transportation, and handling may account for differences, but cores deployed in situ and in the laboratory gave similar results. We suggest that compression of sediment during insertion of core cylinders into the sediment may account for differences between core and chamber fluxes.