Viability of subitaneous eggs of the copepod, Acartia tonsa (Dana), following exposure to various cryoprotectants and hypersaline water

Subitaneous eggs were obtained from monocultures of the calanoid copepod Acartia tonsa (Dana), Gulf of Mexico strain. Eggs were exposed to methanol, ethylene glycol, propylene glycol, glycerine, and DMSO at 0.0, 0.1, 0.5, 1.0, 2.0, and 5.0 M and hypersaline water at 50, 75, 100, 150, and 200 g/L. Treatments were evaluated after 10 and 20 min of exposure and at 4 and 26 °C. Viability (percent hatched) was determined after 24 h of incubation in 35 g/L saltwater at 26 °C. Methanol, ethylene glycol, and glycerine had high viability up to 2M, and all experienced large decreases at 5M when the exposure temperature was 26 °C compared to 4 °C. Eggs exposed to propylene glycol had lower mean viability with greater variability at the lower concentrations although viability was greater than 81.4% at 2 M. Significant decreases in viability were observed at 5 M, and the decreases were much greater at an exposure temperature of 26 °C versus 4 °C. DMSO exposed at 26 °C produced high viability up to 1 M before significant decreases occurred, while an exposure temperature of 4 °C produced high viability up to 2 M. Viability of eggs exposed to hypersaline water of 50, 75, and 100 g/L were not significantly different from controls for all treatment combinations except the 26 °C temperature exposed for 20 min, which was significantly lower at 100 g/L. Concentrations of 150 and 200 g/L produced very few to no viable eggs. These results indicate further research is justified to investigate if viability of A. tonsa eggs can be protected by these cryoprotectants and hypersaline water after exposure to cryopreservation conditions

The High Nutrient Low Chlorophyll (HNLC) Phenomenon and the Iron Hypothesis

47 pagesWith rising CO2 levels in the atmosphere it becomes increasingly more important to understand the nature of the oceans as a sink for CO2 as well as the mechanisms that transport carbon from the atmosphere to the oceans. Regions of ocean in the subarctic Pacific, eastern equatorial Pacific and the southern Ocean have been recognized as being abnormally low in total biomass and yet they maintain high levels of available macronutrients. Due to the characteristic high nutrient low chlorophyll content of these regions, they have been dubbed HNLC. The 'biological pump' concept is a proposed mechanism serving as a carbon sink and was assumed to be limited by nitrogen. Early shipboard container experiments demonstrated that iron might be the limiting nutrient and not nitrogen. The data from the early experiments proved to be inconclusive due to imprecise methodology. In the late 1980' s there was renewed interest in HNLC areas championed by J.H. Martin. He maintained that HNLC regions exhibit Leibig limitation by iron, where, standing crops of phytoplankton are constrained by availability of iron: if iron were available, the standing crops of phytoplankton would increase and nitrate would be depleted despite grazing. Others argue that HNLC regions are a manifestation of active grazing in a steady state ecosystem. An intermediate camp claims that HNLC regions are a result of combined physical and biological processes that prevent the utilization of the surface macronutrients. The debate surrounding this issue prompted Martin and colleagues to perform the IronEx experiment: the in situ use of iron to enhance an HNLC patch in the Galapagos region of the Pacific. The ecosystem demonstrated an unequivocal response to iron; however, macronutrients were still relatively abundant after the experiment. Subsequent studies have revealed that iron impacts all cell size groups of phytoplankton and constrains new production in HNLC areas. What remains unclear is the effect of grazing within these ecosystems

Effects of Salinity on Reproduction and Survival of the Calanoid Copepod Pseudodiaptomus Pelagicus

Four experiments were conducted on the calanoid copepod, Pseudodiaptomus pelagicus, to determine the effects of salinity on survival, development time, reproductive output, and population growth in order to define the optimal salinity for culture. To determine the appropriate experimental salinity range we exposed nauplii and adults to abrupt salinity changes from 35 g/L to 5, 10, 15, 35, 42, and 48 g/L at 30 °C and determined survival after 24 hours. The second experiment stocked early stage nauplii into 1 L beakers after which they were cultured using standard procedures for 10 days at six salinities (10, 15, 20, 25, 30, 35 g/L); from this survival, sex ratio, time to maturation, and fecundity were measured. The third experiment evaluated the effects of salinity on brood size, brood interval, and nauplii production by stocking individual adult pairs and monitoring nauplii production daily for 10 days. The fourth experiment determined the effects of salinity on population growth and composition of the population produced by stocking 10 adult pairs and culturing them until five days after the first mature adults were observed. Results from the abrupt salinity change experiment showed nauplii survival decreased following abrupt changes in salinity from 35 g/L to \u3c 15 g/L and \u3e 35 g/L. Additionally, adults do not tolerate rapid changes in salinity from 35 g/L to \u3c 15 g/L but are rather tolerant of changes in salinity up to 48 g/L. Survival from early nauplii to adult was not significantly affected by salinity but survival declined at 35 g/L. Time to first maturation and maturation of the entire population was significantly influenced by salinity and took from 6.3 to 9.5 days. In the individual paired adults experiment, salinity significantly affected nauplii production by affecting brood interval and brood size. The percentage of ovigerous females peaked at 20 g/L and declined at salinities above and below this value. When developing production objectives, aquaculturists must consider salinity because of its numerous effects on the culture of P. pelagicus. The optimal salinity range to achieve high survival and the greatest nauplii production is 15–25 g/L

Effects of temperature on reproduction and survival of the calanoid copepod Pseudodiaptomus pelagicus

Four experiments were conducted on the calanoid copepod, Pseudodiaptomus pelagicus, to determine the effects of temperature (24, 26, 28, 30, 32, and 34 °C) on survival, development time, reproductive output, and population growth in order to define the optimal temperature for culture. The first experiment stocked early stage nauplii into 1 L beakers and cultured them using standard procedures until five days after the first mature adults were observed; from this survival, sex ratio, time to maturation, and fecundity were measured. The second and third experiments evaluated the effects of temperature on nauplii production by stocking individual pairs and 25 pairs of adults, respectively; in both experiments nauplii production was determined daily for 10 days. The fourth experiment determined the effects of temperature on population growth and composition of the population produced by stocking 10 adult pairs and culturing them for 10 days at six temperatures. Results indicate survival from early nauplii to adult was significantly affected by temperature and those cultured from 24–30 °C had the highest mean survival. Time to first maturation and maturation of the entire population was significantly influenced by temperature and took from 6.8 to 12.8 days. Temperature significantly affected nauplii production in both individual and groups of paired adults. Temperature affected the mean daily nauplii production by decreasing the brood interval but did not affect the mean brood size. The number of nauplii produced by 25 adult pairs was significantly influenced by temperature; the optimal temperature was 27.5 °C at which 1861 nauplii were produced. The distribution of developmental stages in the population was also affected by temperature; at lower temperatures the population consisted of a greater proportion of nauplii while at 32 °C the population was comprised of more advanced staged individuals. When developing production objectives, aquaculturists must consider temperature because it has multiple effects on the culture of P. pelagicus. The optimal temperature range to achieve high survival and the greatest nauplii production is 26–30 °C. To maintain long-term stock cultures the best temperature may be 24 °C to slow maturation and growth while 28–32 °C may be used to maximize nauplii production by decreasing time to maturation and decreasing brood intervals

Cyanophycin Production in a Phycoerythrin-Containing Marine Synechococcus Strain of Unusual Phylogenetic Affinity

Thirty-two strains of phycoerythrin-containing marine picocyanobacteria were screened for the capacity to produce cyanophycin, a nitrogen storage compound synthesized by some, but not all, cyanobacteria. We found that one of these strains, Synechococcus sp. strain G2.1 from the Arabian Sea, was able to synthesize cyanophycin. The cyanophycin extracted from the cells was composed of roughly equimolar amounts of arginine and aspartate (29 and 35 mol%, respectively), as well as a small amount of glutamate (15 mol%). Phylogenetic analysis, based on partial 16S ribosomal DNA (rDNA) sequence data, showed that Synechococcus sp. strain G2.1 formed a well-supported clade with several strains of filamentous cyanobacteria. It was not closely related to several other well-studied marine picocyanobacteria, including Synechococcus strains PCC7002, WH7805, and WH8018 and Prochlorococcus sp. strain MIT9312. This is the first report of cyanophycin production in a phycoerythrin-containing strain of marine or halotolerant Synechococcus, and its discovery highlights the diversity of this ecologically important functional group