Effective Opportunistic Citizen Science 'managed crowd-sourcing' of an Australia-wide network of scientists with taxonomic expertise is used to verify every photographic observation. This unique system is supported by efficient workflows that ensures the rigor of data submitted. Moreover, ease of involvement for participants and prompt personal feedback has contributed to generating and maintaining ongoing interest. The design of Redmap Australia allows co-creation of knowledge with the community-without participants requiring formal training-providing an opportunity to engage sectors of the community that may not necessarily be willing to undergo training or otherwise be formally involved or engaged in citizen science. Given that capturing changes in our natural environment requires many observations spread over time and space, identifying factors and processes that support large-scale citizen science monitoring projects is increasingly critical.

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We present findings of the first mesoscale study linking larval fish assemblages and water masses along shelf waters off south-eastern Australia (southern Queensland-New South Wales), based on vertical, non-depth discriminate data from surveys in October 2002 and 2003 (spring) and July 2004 (winter). Clustering and ordination were employed to discriminate between larval assemblages and, for the first time, to define water masses from water column temperature frequencies. Surveys yielded 18 128 larval fishes comprising 143 taxa from 96 identifiable families, with small pelagics accounting for 53% of the total. Three major recurrent larval assemblages were identified during the study, each of which matched one of three water masses, namely East Australian Current to the north (EAC; 20.5-23.4°C), Tasman Sea to the south (TAS; 14.8-17.5°C), and mixed EAC-TAS water in between (MIX; 18.3-19.9°C). All three assemblages were present in spring, whereas only EAC and MIX occurred in the more northerly constrained winter survey. Furthermore, boundaries between the EAC, MIX and TAS assemblages were found to be dynamic, with locations shifting temporally and spatially depending on EAC extent. Assemblage composition differed significantly between water masses across surveys, with EAC-TAS being most dissimilar. Such contrast was due to the presence of tropical ⁄ temperate taxa in EAC, primarily temperate-associated taxa in TAS, and a combination of EAC-TAS taxa within MIX consistent with the convergence of both waters. Results highlight the strength of employing larval assemblages as indicators of water masses, particularly in view of the potential effect of climate change on spawning habitats of shelf fishes.

The effects of sediment hypoxia, resulting from increased carbon loads or decreased dissolved oxygen (DO), on nitrogen cycling in estuarine environments is poorly understood. The important role played by bacterial and archaeal ammonia oxidizers in the eventual removal of nitrogen from estuarine environments is likely to be strongly affected by hypoxic events. In this study, an analysis of the effects of different levels of sediment hypoxia (5%, 20% and 75% DO) was performed in a microcosm experiment. Changes in the nutrient fluxes related to nitrification at 5% DO were observed after 4 h. Quantification of the key nitrification gene ammonium monooxygenase (amoA) in both DNA and RNA extracts suggests that bacterial amoA transcription was reduced at both of the lower DO concentrations, while changes in DO had no significant effect on archaeal amoA transcription. There was no change in the diversity of expressed archaeal amoA, but significant change in bacterial amoA transcriptional diversity, indicative of low- and high-DO phylotypes. This study suggests that groups of ammonia oxidizers demonstrate differential responses to changes in sediment DO, which may be a significant factor in niche partitioning of different ammonia oxidizer groups.

We describe findings of three ichthyoplankton surveys undertaken along south-eastern Australia during spring (October 2002(October , 2003 and winter (July 2004) to examine spawning habitat and dynamics of blue mackerel (Scomber australasicus). Surveys covered 860 nautical miles between southern Queensland (Qld; 24.6°S) and southern New South Wales (NSW; 41.7°S), and were mainly centred on the outer shelf including the shelf break. Egg identifications were verified applying mtDNA barcoding techniques. Eggs (n = 2971) and larvae (n = 727; 94% preflexion) occurred both in spring and winter, and were confined to 25.0-34.6°S. Greatest abundances (numbers per 10 m 2 ) of eggs (1214-7390) and larvae (437-1172) occurred within 10 nm shoreward from the break in northern NSW. Quotient analyses on egg abundances revealed that spawning is closely linked to a combination of bathymetric and hydrographic factors, with the outer shelf as preferred spawning area, in waters 100-125 m deep with mean temperatures of 19-20°C. Eggs and larvae in spring occurred in waters of the East Australian Current (EAC; 20.6-22.3°C) and mixed (MIX; 18.5-19.8°C) waters, with none occurring further south in the Tasman Sea (TAS; 16.0-17.0°C). Results indicate that at least some of the south-eastern Australian blue mackerel stock spawns during winterspring between southern Qld and northern NSW, and that no spawning takes place south of 34.6°S due to low temperatures (<17°C). Spawning is linked to the EAC intrusion, which also facilitates the southward transport of eggs and larvae. Since spring peak egg abundances came from where the EAC deflects offshore, eggs and larvae are possibly being advected eastwards along this deflection front. This proposition is discussed based on recent data on blue mackerel larvae found apparently entrained along the Tasman Front.