Predicted Marine Climate Change: Influence of Elevated Temperature and lowered pH on Feeding preference and Egg production of Cyclopoid Copepod Oithona rigida

In aquatic ecosystems, copepods are an important link between primary producers and secondary consumers. In the present investigation, ingestion, egg production and carbon of Oithon rigida under mono and mixed prey species was investigated under the isolated and combined stressors of ocean warming and acidification. When experiments performed under mono culture, the temperature had a positive effect on ingestion rate at 31^oC in all micro algae species with maximum consumption on Dunaliella sp with 19.34 ± 0.5 ng C cop.^-1 hr.^-1. The pH also had significant impact on ingestion rate of all algal species. However the combination of pH and temperature showed uneven ingestion rate, though, the consumption was high than isolated stress. Whereas, under mixed prey species, there was a clear shift in ingestion; from Chlorella sp (0.162 ± 0.06) at 28^oC to Dunaliella sp (0.343 ± 0.04) at all temperature under 7.9 and 7.7 treatments. The temperature also had significant effect on egg carbon and production at 30^oC with 8.62 ± 0.83; 8.5 ± 0.52; and 10.5 ± 2.3 eggs female^-1 under algal species Dunaliella sp, Isochrysis sp , Pavlova sp. The pH also had significant effect on egg production, where egg production decreased with lower pH. Whereas, combined stressors had no significant impact on egg production. Egg production and carbon under mixed prey species was significantly high at 30^oC at pH 8.1. The results of the study reveals that combining pH and temperature had increased ingestion rate and decreased egg production and carbon. At stress conditions the O.rigida preferred large species ( Dunaliella sp) to compensate energy (carbon) requirement for metabolism. The ingestion rate and reproductive output under interactive effect, shown a subtle changes.