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Mariculture (marine aquaculture) generates nutrient waste either through the excretion by the reared organisms, or through direct enrichment by, or remineralization of, externally applied feed inputs. Importantly, the waste from fish or shellfish cannot easily be managed, as most is in dissolved form and released directly to the aquatic environment. The release of dissolved and particulate nutrients by intensive mariculture results in increasing nutrient loads (finfish and crustaceans), and changes in nutrient stoichiometry (all mariculture types). Based on different scenarios, we project that nutrients from mariculture will increase up to six fold by 2050 with exceedance of the nutrient assimilative capacity in parts of the world where mariculture growth is already rapid. Increasing nutrient loads and altered nutrient forms (increased availability of reduced relative to oxidized forms of nitrogen) and/or stoichiometric proportions (altered nitrogen:phosphorus ratios) may promote an increase in harmful algal blooms (HABs) either directly or via stimulation of algae on which mixotrophic HABs may feed. HABs can kill or intoxicate the mariculture product with severe economic losses, and can increase risks to human health.

High-resolution seismic profiles along with physical and sedimentological properties of sediment cores from the Saguenay (Eastern Canada) and Reloncavi (Chile) Fjords allowed the identification of several decimeter to meter-thick turbidites. In both fjords, the turbidites were associated with large magnitude historic and prehistoric earthquakes including the 1663 AD (M > 7) earthquake in the Saguenay Fjord, and the 1960 (M 9.5), 1837 (M ~ 8) and 1575 AD major Chilean subduction earthquakes in the Reloncavi Fjord. In addition, a sand layer with exoscopic characteristics typical of a tsunami deposit was observed immediately above the turbidite associated with the 1575 AD earthquake in the Reloncavi Fjord and supports both the chronology and the large magnitude of that historic earthquake. In the Saguenay Fjord, the earthquake-triggered turbidites are sometimes underlying a hyperpycnite associated with the rapid breaching and draining of a natural dam formed by earthquake-triggered landslides. Similar hyperpycnal floods were also recorded in historical and continental geological archives for the 1960 and 1575 AD Chilean subduction earthquakes, highlighting the risk of such flood events several weeks or months after main earthquake. In both fjords, as well as in other recently recognized earthquake-triggered turbidites, the decimeter-to meter-thick normally-graded turbidites are characterized by a homogeneous, but slightly fining upward tail. Finally, this paper also emphasizes the sensitivity of fjords to record historic and prehistoric seismicity.

Profiles of particulate and dissolved 234 Th (t 1/2 = 24.1 days) in seawater and particulate 234 Th collected in drifting traps were analyzed in the Barents Sea at five stations during the ALV3 cruise (from June 28 to July 12, 1999) along a transect from 78j15VN-34j09VE to 73j49VN-31j43VE. 234 Th/ 238 U disequilibrium was observed at all locations. 234 Th data measured in suspended and trapped particles were used to calibrate the catchment efficiency of the sediment traps. Model-derived 234 Th fluxes were similar to 234 Th fluxes measured in sediment traps based on a steady-state 234 Th model. This suggests that the sediment traps were not subject to large trapping efficiency problems (collection efficiency ranges from 70% to 100% for four traps). The export flux of particulate organic carbon (POC) can be calculated from the model-derived export flux of 234 Th and the POC/ 234 Th ratio. POC/ 234 Th ratios measured in suspended and trapped particles were very different (52.0 F 9.9 and 5.3 F 2.2 Amol dpm À 1 , respectively). The agreement between calculated and measured POC fluxes when the POC/ 234 Th ratio of trapped particles was used confirms that the POC/ 234 Th ratio in trap particles is representative of sinking particles. Large discrepancies were observed between calculated and measured POC fluxes when the POC/ 234 Th ratio of suspended particles was used. In the Barents Sea, vertical POC fluxes are higher than POC fluxes estimated in the central Arctic Ocean and the Beaufort Sea and lower than those calculated in the Northeast Water Polynya and the Chukchi Sea. We suggest that the latter fluxes may have been strongly overestimated, because they were based on high POC/ 234 Th ratios measured on suspended particles. It seems that POC fluxes cannot be reliably derived from thorium budgets without measuring the POC/ 234 Th ratio of sediment trap material or of large filtered particles. D