Effects of the harmful algae, Alexandrium catenella and Dinophysis acuminata, on the survival, growth, and swimming activity of early life stages of forage fish.

The effects of co-occurring harmful algal blooms (HABs) on marine organisms is largely unknown. We assessed the individual and combined impacts of the toxin producing HABs, Alexandrium catenella and Dinophysis acuminata, and a non-toxin-producing HAB (Gymnodinium instriatum) on early life stages of two estuarine fish species (Menidia beryllina and Cyprinodon variegatus). Lethal (i.e. time to death) and sublethal (i.e. growth, grazing rate, and swimming activity) effects of cultured HABs were investigated for eleutheroembryo and larval life stages. Mixed algal treatments (i.e. A. catenella and D. acuminata mixtures) were often equally toxic as A. catenella monoculture treatments alone, although responses depended on the fish species and life stage. Fish exposed to toxin producing HABs died significantly sooner (i.e. <1-3 days) than controls. Significant differences in sublethal effects were also found between fed controls and toxic HAB treatments, although responses were often similar to G. instriatum or starved controls. Collectively, the results demonstrate that HABs may reduce fish productivity and fitness.