Description: Strong correlations between particulate organic carbon (POC) and ballast minerals have been observed in the deep ocean. This has led to the postulation that ballast minerals can enhance POC flux by increasing the density and sinking velocity of ballasted aggregates and/or that ballast minerals protect the aggregated organic matter from degradation. Here we experimentally tested the influence of the ballast mineral smectite on the formation, size, dry weight, size-specific sinking velocity, carbon-specific respiration rate, and total POC flux of marine snow aggregates formed in roller tanks from a natural plankton community isolated from the North Sea. This study shows that the inclusion of smectite offers no protection against degradation of organic matter in freshly produced or aged marine snow aggregates. The main effect of ballasting with smectite was an increase in the density of the aggregates and, therefore 2- to 3-fold higher size-specific sinking velocities. Mineral ballasting had no influence on the total volume of aggregates or the total aggregated amount of POC. Nevertheless, the effect of increased sinking velocities in the ballasted treatment resulted in 2.7 ± 1.6 times larger potential POC fluxes compared to the non-ballasted aggregates. This implies that the incorporation of ballast minerals into sinking organic aggregates can increase the efficiency of the biological pump.

Description: For most fish species raised in marine aquaculture, the use of live feeds cannot be replaced by formulated diets. Artemia nauplii and rotifers are still the most commonly used live feeds. A good alternative lies in the use of copepods which could lead to the cultivation of new fish species. Cold stored subitaneous eggs from the continuously cultured calanoid copepod Acartia tonsa were used to investigate the effect of storage upon the viability of the eggs, the development of the copepod community originating from the cold stored eggs. Finally a 3 days snapshot of the egg production of the first generation of females was followed. This was done in order to develop a database usable within copepod dependent hatcheries. The viability of cold stored A. tonsa eggs remained high (〉 70% hatching rate) for 11 months of storage. Generally, the period of storage was observed to decrease the viability (hatching rate) of the eggs and no hatching was observed after twenty months of cold storage. Hatched populations of copepods experienced increased mortality rate with longer storage of the eggs from which they originated. This mortality ranged from 0.035 to 0.13 d− 1 for non-stored (fresh) and 12 months stored eggs, respectively. However, all copepod communities originating from fresh to 12 months stored eggs reached adulthood. Additionally, the egg production from the stored generation was apparently normal and the viability of their eggs was not statistically different when compared to productions from non-stored communities. Contents of total fatty acids decreased during the storage period. Contents of free amino acids were not statistically different for eggs cold stored up to 12 months, but had decreased severely by 20 months. In conclusion, we consider it safe to store the eggs for up to one year at 2–3 °C during which the eggs retain their viability and biochemical composition. Cold storage of calanoid copepod eggs is relevant for aquaculture as inoculum for culturing live food.