Marine invertebrates experience a substantial amount of mortality during the early benthic phase which can influence a population’s future abundance and distribution as well as exert selective pressure, driving its evolution. Some causative agents of intertidal juvenile marine invertebrate mortality have already been elucidated, such as predation and desiccation stress, but the influence of bacterial infection on early benthic phase mortality is not known. The purpose of this study is to evaluate the role of infectious agents in generating the high mortality rates observed amongst wild populations of juvenile invertebrates living in the intertidal zone.
In this study, five antibiotics were administered to juvenile Mytilus trossulus (mussels) and Nucella ostrina (snails): oxytetracycline (OTC), chloramphenicol (CM), kanamycin sulfate (KS), and trimethoprim and sulfamethoxazole (TxS). The juveniles were placed in small cages and were constantly submerged off of the Bamfield Marine Sciences Centre docks. M. trossulus and N. ostrina were soaked in a mixture of the antibiotics for a half hour three times per day for five days. After five days the mortality in the treatment and control groups was compared.
Mortality was low in the control treatment for both species, ranging from 0 - 3.7% (M. trossulus) and 0.5 - 4.0% (N. ostrina), indicating that infectious stress is not a major cause of mortality of juvenile marine invertebrates. Further, no significant difference in mortality was observed between the antibiotic treatment and control treatment for either M. trossulus or N. ostrina (Friedman block test P>0.99 S<0.01 (M. trossulus); Friedman block test P=0.564 S=0.33 (N. ostrina)), indicating that bacterial infection is not causing mortality of juvenile marine invertebrates.
