A Very Large Spawning Aggregation of a Deep-Sea Eel: Magnitude and Status

Multiple lines of evidence substantiate the existence of a very large aggregation of the basketwork eel, Diastobranchus capensis, on the small (3 km2) Patience Seamount off southeast Australia. The aggregation appears to be present year-round, but largest in the austral autumn when composed of spawning eels. Twenty eels caught in April 2015 (14 female, 6 male) were all in advanced stages of spawning condition. The eel’s abundance in the aggregation was very high as measured at seamount, local and regional scales. Hydroacoustic measurement of the spawning aggregation’s dimensions (~100 × 1000 m) and conservative counts of 100 s of eels along camera transects of ~1000–2000 m length indicate 10,000 s individual eels may have been present. The absence of other known spawning locations indicates the Patience Seamount is a regional-scale spatial anchor for spawning. The aggregation was protected in a marine park in 2007 following a decades-long impact from bottom trawling, indicating that the population can be expected to stabilise and recover. Monitoring the aggregation’s status, and validating seasonal spawning, provide important opportunities to examine conservation-led recovery in the deep sea as part of Australia’s new national strategy of Monitoring, Evaluation, Reporting and Improvement (MERI) for conservation values within marine parks.

Southern Hemisphere Continental Temperature Responses to Major Volcanic Eruptions Since 1883 in CMIP5 Models

Although global and Northern Hemisphere (NH) temperature responses to volcanic forcing have been extensively investigated, knowledge of such responses over Southern Hemisphere (SH) continental regions is still limited. Here we use an ensemble of CMIP5 models to explore SH temperature responses to four major volcanic eruptions: Krakatau (1883), Santa Maria (1902), Agung (1963) and Pinatubo (1991). Focus is on near-surface temperature responses over southern continental landmasses including southern South America (SSA), southern Africa (SAF) and Australia and their seasonal differences. Findings indicate that for all continents, temperature responses were strongest and lasted longest following the Krakatau eruption. Responses in Australia had the shortest lag time, strongest maximum seasonal response, as well as the most significant monthly anomalies. In contrast, SSA records the longest lag time, weakest maximum seasonal temperature response, and lowest number of monthly negative anomalies following these eruptions. In most cases, the strongest single-season response occurred in austral autumn or winter, and the weakest in summer or spring. We tentatively propose that cooler temperature responses are likely caused, at least in part, by the intensification of the westerlies and associated mid-latitude cyclones and anti-cyclones.

First High-Frequency Underway Observation of DMS Distribution in the Southern Ocean during Austral Autumn

We investigate the distribution of dimethyl sulfide (DMS) in the Southern Ocean’s (50° W to 170° W) surface water, including the Antarctic Peninsula and the marginal sea ice zone (MIZ) in the Ross and Amundsen Seas. This is the first high-frequency observation conducted in the austral autumn (in April) in the Southern Ocean. The mean DMS concentration was 2.7 ± 2.5 nM (1 σ) for the entire study area. Noticeably enhanced DMS (5 to 28 nM) concentrations were observed in the MIZ around the Ross and Amundsen Seas and the coastal regions in the Antarctic Peninsula; this could be attributed to biological production of local ice algae, which appears to be supplied with nutrients from glacial or sea ice melt water. These observed DMS inventories were significantly higher (an order of magnitude) than current climatological DMS inventories. The local DMS sources being transported outward from the polynyas, where strong bloom occurs during summer, could result in larger discrepancies between observed DMS and climatological DMS in the MIZ area (in the Amundsen Sea). Overall, this study is the first to highlight the significance of the underestimation of current DMS fluxes in the austral autumn, which consequently results in significant errors in the climate models.

Bathyptilones: Terpenoids from an Antarctic Sea Pen, Anthoptilum grandiflorum (Verrill, 1879)

An Antarctic coral belonging to the order Pennatulacea, collected during the 2013 austral autumn by trawl from 662 to 944 m depth, has yielded three new briarane diterpenes, bathyptilone A-C (1–3) along with a trinorditerpene, enbepeanone A (4), which bears a new carbon skeleton. Structure elucidation was facilitated by one- and two-dimensional NMR spectroscopy, mass spectrometry and confirmed by X-ray crystallography. The three compounds were screened in four cancer cell lines. Bathyptilone A displayed selective nanomolar cytotoxicity against the neurogenic mammalian cell line Ntera-2.

Remote sensing of upwelling off Australia's north-east coast

Cross-shelf processes drive the exchange of water between the continental shelf and western boundary currents, leading to the import and export of heat, freshwater, sediments, nutrients, plankton, fish larvae, and other properties. Upwelling is an important process which modulates those exchanges. It regulates primary productivity, which in turn promotes higher trophic levels and fisheries. In this paper, we investigate upwelling events in the East Australian Current (EAC) intensification zone off Southeast Queensland through the analysis of remotely-sensed Chlorophyll-a (Chl-a) and Sea Surface Temperature (SST) as well as wind and ocean reanalysis products. A particular focus is on identifying the likely mechanisms that drive upwelling events during the austral autumn to winter which are evident from cold SST and enhanced Chl-a concentrations. Four complementary Upwelling Indices (UIs) are derived. Chl-a (UIChla) and SST (UISST) based indices characterize the oceanic response to upwelling, while indices based on wind (UIw) and current (UIc) data capture the forcing of upwelling. The spatial and temporal variability of all UIs is examined over the continental shelf. It reveals distinct seasonal patterns. For the northern region, UIs identify the well-known Southeast Fraser Island Upwelling System. It prevails during the austral spring to early summer and is driven by current- and upwelling favourable wind. In contrast, upwelling is enhanced over the southern shelf during austral autumn to winter. About 70 % of all UISST and UIChla identified upwelling events occur during this period. A case study is presented that provides observational evidence for the existence of a shelf-break upwelling. Simultaneous downwelling favourable wind stress and upwelling favourable current-driven bottom stress establish a flow convergence in the bottom boundary layer (BBL). These convergent BBL flows force upwelling of cold and nutrient-rich slope waters as evident from negative SST anomaly and enhanced Chl-a in austral autumn to winter. It is evident from these results that the shelf region is characterised by two distinct seasonally reoccurring upwelling regimes.