No abstract

To determine the optimal food concentrations for the mass culture of the tropical copepod Pseudodiaptomus annandalei at relevant temperatures, we conducted three functional response experiments. In these experiments, we quantified the grazing rate via the faecal pellet production of adult males and females. They were fed for 6 hr on one of three commonly used microalgal species in aquaculture: Chaetoceros muelleri, Isochrysis galbana and Tetraselmis chui at concentrations of 12.5–3,200 μg C L−1 and three temperatures 25, 30 and 35°C. The number of pellets (PP) and the total volume of pellets (SPP) of both sexes increased rapidly with the increase in the microalgal concentrations until maximal pellet production (PPmax or SPPmax) was obtained, where females showed a consistently higher SPP than males. This pattern was similar for all three microalgal species. Males showed inconsistent PP and SPP in response to algae and temperatures. For females, they showed two clear patterns: a higher PP and SPP with increasing temperature from 25 to 30°C, then a lower PP and SPP at 35°C. Our study provides fundamental knowledge of pellet production to determine the food requirements of P. annandalei under different temperatures that are essential for designing the technical protocol for biomass culture.

Shallow, tropical marine ecosystems provide essential ecosystem goods and services, but it is unknown how these ecosystems will respond to the increased exposure to the temperature extremes that are likely to become more common as climate change progresses. To address this issue, we tracked the fitness and productivity of a key zooplankton species, the copepod Pseudodiaptomus annandalei, acclimated at two temperatures (30 and 34 °C) over three generations. 30 °C is the mean temperature in the shallow water of the coastal regions in Southeast Asia, while 34 °C simulated a temperature extreme that occurs frequently during the summer period. For each generation, we measured the size at maturity and reproductive success of individuals. In all three generations, we found strong negative effects of warming on all measured fitness-related parameters, including prolonged development time, reduced size at maturity, smaller clutch sizes, lower hatching success, and reduced naupliar production. Our results suggest that P. annandalei are already exposed to temperatures that exceed their upper thermal optimum. Increased exposure to extreme temperatures may reduce the abundance of these tropical marine copepods, and thus reduce the availability of resources to higher trophic levels.

No abstract

The calanoid copepod Pseudodiaptomus annandalei is used as live feed in aquaculture because of its nutritional value and the ability to cope with environmental fluctuations in outdoor ponds. However, little knowledge exists on its ecology. Here we investigated the ecology of P. annandalei in an aquaculture pond in Vietnam. Temperature, salinity, chlorophyll a and biomass of protozoans and copepods were monitored every other day for 1 month. Experiments on protozoan growth and grazing by P. annandalei were also conducted. Copepod fecal pellet production and temperature-dependent egg hatching rates were likewise quantified. Despite very high phytoplankton biomass, biomass of P. annandalei was surprisingly low. Copepod production was estimated from three independent methods: clearance, weight-specific egg production rate (SEP) and specific fecal pellet production rate. SEP proved to be accurate to predict the in situ population growth in the pond. A simple model for production of P. annandalei based on SEP was developed. Our study extends our knowledge of how environmental conditions in the pond may affect the population dynamics and production of copepods. The results have important implications for pond managements ensuring stable copepod production and harvest.