Effects Of Temperature And Salinity On Oxygen-Consumption And Nitrogen-Excretion In Thais (Nucella) Lapillus (L)

The 2-wk TLm of stepwise-acclimated Thais lapillus (L.) (>20 mm long) was 14.2–16.2%. salinity (S) at 5, 10, 15, and 20°C. The same TLm occurred at 10 °C after direct transfer of snails to the final salinity but stepwise-acclimated small snails (<20 mm) tolerated a significantly lower salinity (12.7%. S). Oxygen consumption rates () fit the allometric equation . Salinity and temperature had a significant effect on , which was highest at 30%. S and depressed at 17.5%. S and at 5°C. Ammonia excretion rates fit the allometric equation . Both salinity and temperature affected . Ammonia excretion was significantly lower at 17.5 %. S than at higher salinities at 10, 15, and 20°C, but did not vary as a function of salinity at 5°C. Primary amines were lost from snails under all conditions without any obvious relationship with temperature or salinity. Primary-amine loss, expressed as a percentage of , was significantly higher at 17.5 %. S than at higher salinities. Oxygen : nitrogen ratios ranged from 4.2–15.6, indicating protein was the primary metabolic substrate, and were highest at 15 °C and lowest at 5 °C. Snails withstood 89 days starvation without mortality at 10°C. Oxygen consumption of snails declined by 28% during starvation due to a 37% decline in dry weight; consequently, weight-specific respiration rate increased by 17%. The intercept (a) for the allometric equations did not change during starvation. Ammonia excretion increased during starvation, and primary-amine loss increased until Day 21, then declined. Oxygen: nitrogen ratios declined from 14 to 8, indicating an increased catabolism of protein during starvation.

The interaction of polymer-coated magnetic nanoparticles with seawater

Laboratory studies were conducted to evaluate the interaction between bare and polymer-coated magnetic nanoparticles (MNPs) with various environmentally relevant carrying solutions including natural oceanic seawater with and without addition of algal exopolymeric substances (EPS). The MNPs were coated with three different stabilising agents, namely gum Arabic (GA-MNP), dextran (D-MNP) and carboxymethyl-dextran (CMD-MNP). The colloidal stability of the suspensions was evaluated over 48 h and we demonstrated that: (i) hydrodynamic diameters increased over time regardless of carrying solution for all MNPs except the GA-coated ones; however, the relative changes were carrying solution- and coat-dependent; (ii) polydispersity indexes of the freshly suspended MNPs are below 0.5 for all coated MNPs, unlike the much higher values obtained for the uncoated MNPs; (iii) freshly prepared MNP suspensions (both coated and uncoated) in Milli-Q (MQ) water show high colloidal stability as indicated by zeta-potential values below -30 mV, which however decrease in absolute value within 48 h for all MNPs regardless of carrying solution; (iv) EPS seems to "stabilise" the GA-coated and the CMD-coated MNPs, but not the uncoated or the D-coated MNPs, which form larger aggregates within 48 h; (v) despite this aggregation, iron (Fe)-leaching from MNPs is sustained over 48 h, but remained within the range of 3-9% of the total iron-content of the initially added MNPs regardless of suspension media and capping agent. The environmental implications of our findings and biotechnological applicability of MNPs are discussed.