A nuanced quantile random forest approach for fast prediction of a stochastic marine flooding simulator applied to a macrotidal coastal site

Integrating full-process high resolution hydrodynamic simulations within early warning system (EWS) for marine flooding is hindered by the large computation time cost of such numerical models. This...     

Past and future evolution in the Thames Estuary

In order to manage estuaries effectively, it is important to be able to predict how they are likely to change in the future, both to natural and anthropogenic forcing. This paper looks at historical morphological development of the Thames Estuary, taking into account the effect of human intervention, and uses the ASMITA morphological model to predict the long-term evolution of the estuary into the future, assuming either historic rates of sea-level rise or accelerated sea-level rise. The historical sediment budget for the Thames Estuary was examined and source and sink terms, including fluvial sediment supply and historical dredging rates, were included in the ASMITA model. ASMITA predictions showed good overall agreement with the historical data, highlighting the benefits of detailed historical review and the inclusion of anthropogenic effects in the model. Future ASMITA predictions for the period 2000 to 2100 suggest that, under both historical and accelerated sea-level rise scenarios, the estuary will experience accretion, but, for the accelerated sea-level rise scenario, accretion will be at a slower rate than sea level rise. With accelerated sea-level rise, intertidal profiles were predicted to be up to 0.5 m lower with respect to high water.     

数值模式不同分辨率和地形对东亚降水模拟影响的试验

为探讨东亚地区降水数值模拟中水平分辨率和地形的作用,使用RegCM2区域气候模式,采用不同的模式分辨率和地形,对东亚降水进行对比模拟试验.结果表明,东亚地区降水的模拟效果取决于模式的水平分辨率,模式分辨率越高,模拟的效果越好.使用实际地形的模拟效果好于使用平滑地形的.但同时,使用较高分辨率的平滑地形的模拟,效果好于使用次高分辨率的实际地形的模拟.这表明在东亚地区降水模拟中,分辨率与地形相比,起着至少同样重要的作用.结果指出,对东亚地区降水的模拟而言,使用60 km及以上分辨率可能是必需的.     

Shelf spawning habitat of Emmelichthys nitidus in south-eastern Australia – Implications and suitability for egg-based biomass estimation

The spawning habitat of Emmelichthys nitidus (Emmelichthyidae) in south-eastern Australia is described from vertical ichthyoplankton samples collected along the shelf region off eastern through to south-western Tasmania during peak spawning in October 2005–06. Surveys covered eastern waters in 2005 (38.8–43.5°S), and both eastern and southern waters in 2006 (40.5°S around to 43.5°S off the south-west). Eggs (n = 10,393) and larvae (n = 378) occurred along eastern Tasmania in both years but were rare along southern waters south and westwards of 43.5°S in 2006. Peak egg abundances (1950–2640 per m⁻²) were obtained off north-eastern Tasmania (40.5–41.5°S) between the shelf break and 2.5 nm inshore from the break. Eggs were up to 5-days old, while nearly 95% of larvae were at the early preflexion stage, i.e. close to newly emerged. Average abundances of aged eggs pooled across each survey declined steadily from day-1 to day-5 eggs both in 2005 (97-18) and 2006 (175-34). Moreover, day-1 egg abundances were significantly greater 2.5 nm at either side of the break, including at the break, than in waters ≥5 nm both inshore and offshore from the break. These results, complemented with egg and larval data obtained in shelf waters off New South Wales (NSW; 35.0–37.7°S) in October 2002–03, indicate that the main spawning area of E. nitidus in south-eastern Australia lies between 35.5°S off southern NSW and 43.5°S off south-eastern Tasmania, and that spawning activity declines abruptly south and westwards of 43.5°S around to the south-west coast. In addition, quotient analyses of day-1 egg abundances point to a preferred spawning habitat contained predominantly within a 5 nm corridor along the shelf break, where waters are 125–325 m deep and median temperatures 13.5–14.0 °C. Spawning off eastern Tasmania is timed with the productivity outburst typical of the region during the austral spring, and the temperature increase from the mixing between the southwards advancing, warm East Australian Current and cooler subantarctic water over the shelf. Overall, ichthyoplankton data, coupled with reproductive information from adults trawled off Tasmania, indicate that E. nitidus constitutes a suitable species for the application of the daily egg production method (DEPM) to estimate spawning biomass. This finding, together with evidence in support of a discrete eastern spawning stock extending from southern NSW to southern Tasmania, strengthens the need for DEPM-based biomass estimates of E. nitidus prior to further fishery expansion.     

High-sediment tolerance in the reef coral Turbinaria mesenterina from the inner Great Barrier Reef lagoon (Australia)

Sedimentation is an important stressor on coral reefs subjected to run-off, dredging and resuspension events. Reefs with a history of high-sediment loads tend to be dominated by a few tolerant coral species. A key question is whether such species live close to their tolerance thresholds or near their niche optima. Here, we analyse experimentally the sediment tolerance of a spatially dominant coral, Turbinaria mesenterina (Dendrophylliidae), at nearshore reefs in the central Great Barrier Reef lagoon. Testing was conducted in a 5-week tank experiment under manipulated sediment loading and flow conditions. Physiological stress was assessed based on the behaviour of three key response variables: skeletal growth rate, energy reserves (lipid content) and photosynthetic performance. Because sediment effects are likely to vary between flow regimes, sediment and flow responses were tested using a full factorial design. Sediment loads greater than 110 mg cm⁻² had no effect on any of the physiological variables, regardless of flow (0.7–24 cm s⁻¹). Turbinaria mesenterina is thus tolerant to sediment loads an order of magnitude higher than most severe sediment conditions in situ. Likely mechanisms for such tolerance are that: (1) colonies covered in sediment (60–120 μm) in low-flow were able to clear themselves rapidly (within 4–5 h); and (2) sediment provides a source of food. These results suggest that intensified sediment regimes on coastal reefs may shift coral communities towards dominance by a few well-adapted species.