Responses of the estuarine copepod Pseudodiaptomus annandalei to diatom polyunsaturated aldehydes: Reproduction, survival and postembryonic development

• The diatom PUA decadienal strongly impacted demographic traits of Pseudodiaptomus annandalei.
• Decadienal negatively affected survival, development and reproduction in a dose-dependent manner.
• Nauplii successfully molted to copepodites; however copepodites were not able to molt to the adult stage when exposed to decadienal.
• Negative effects on female survival were not recorded beyond 6 days of exposure to decadienal suggesting an evolutionary adaptive response to PUA with time.
• Progressive tolerance to decadienal suggest evolutionarily adaptive response to PUA with time.

The euryhaline calanoid copepod Pseudodiaptomus annandalei perennially occurs in tropical and subtropical brackish water ecosystems and harbors supporting harmful algal blooms. In the present paper we provide a quantitative assessment of the influence of the diatom-derived poly-unsaturated aldehyde (PUA), 2-trans-4-trans-decadienal on demographic traits of P. annandalei. The survival and reproduction of P. annandalei were recorded in life table experiments, using a cohort of adult males and females exposed to a range of concentrations (0.75, 1.5, 3 and 4.5 μM) of decadienal. Higher mortality of female cohorts and lower reproduction were recorded with increasing concentrations of decadienal (3 and 4.5 μM). The estimated survival time for cohort females (control: 9.7 days; 4.5 μM decadienal: 4.7 days) and developmental stages of copepods (control: 10.5 days; 4.5 μM decadienal: 1.0 days) in decadienal applied medium (Isochrysis galbana + decadienal) was significantly lower than those in control (only I. galbana). Detrimental effects further eroded recruitment by increasing naupliar mortality and impairing copepodite development to adulthood. Since P. annandalei is widely used in the aquaculture industry in Asia, the present results call for a limited use of PUA producing diatoms as algal food to avoid impairing copepod reproduction and development.