Effects of Phytoplankton Growth Phase on Settling Properties of Marine Aggregates

Marine snow aggregates often dominate carbon export from the surface layer to the deep ocean. Therefore, understanding the formation and properties of aggregates is essential to the study of the biological pump. Previous studies have observed a relationship between phytoplankton growth phase and the production of transparent exopolymer particles (TEP), the sticky particles secreted by phytoplankton that act as the glue during aggregate formation. In this experimental study, we aim to determine the effect of phytoplankton growth phase on properties related to aggregate settling. Cultures of the diatom Thalassiosira weissflogii were grown to four different growth phases and incubated in rotating cylindrical tanks to form aggregates. Aggregate excess density and delayed settling time through a sharp density gradient were quantified for the aggregates that were formed, and relative TEP concentration was measured for cultures before aggregate formation. Compared to the first growth phase, later phytoplankton growth phases were found to have higher relative TEP concentration and aggregates with lower excess densities and longer delayed settling times. These findings may suggest that, although particle concentrations are higher at later stages of phytoplankton blooms, aggregates may be less dense and sink slower, thus affecting carbon export.

Fortress with Sticky Moats: the Functional Role of Small Particles around Tetragonisca angustula Latreille (Apidae: Hymenoptera) Nest Entrance

Many bee species are able to defend themselves against pollen or honey thievery. We herein report the functional role of small sticky particles deposited by Tetragonisca angustula Latreille in its nest entrance external side. This strategy was very effective to prevent ants from invading the bees’ nest. We reported many dead ants attached to the nest entrance and different ant species easily immobilized after being moved onto the entrance tube containing sticky particles. This is the first description of the functional role played by the nest entrance sticky particles under natural conditions..

The Relationship of Flowability, Hygroscopicity and Compressibility Properties between Microcrystalline Cellulose, Sarcandrae Extract Powder, and the Mixture of the Two Materials

Microcrystalline Cellulose and Sarcandrae extract powder were used to study the relationships of pharmaceutical properties of powders before and after mixing operation. The theoretical values of the physical quantities of the binary mixture were calculated based on the random mixing theory. The measured values of angle of repose, hygroscopicity of binary mixture were larger than that of theoretical calculations. The effective Kawakita a and b for the MCC had changed by mixing operation. The parameters of blend powder reduced compared with MCC except D-1. The results suggested that the mixing behavior was not a complete random or simple superposition operation for the rough and sticky particles. The mixing process would create novel particles and the physical quantities of novel particles would changes regularly.