An investigation of harmful jellyfish mitigation measures: From sting management to jellyfish forecasting

Abstract

Even though they provide many beneficial services to their ecosystem, jellyfish are infamous for their direct negative impact on human activities such as fishing, power generation, tourism and aquaculture. To address the impacts of jellyfish on public safety and aquaculture in Ireland, this thesis set out to address the following questions: 1) Can mass stranding events in Ireland be forecasted? 2) What should be done in the event of a jellyfish sting? 3) Which and how many nematocysts do jellyfish possess? and 4) What happens when jellyfish sting fish and how might this be mitigated? Two scyphozoans, lion’s mane jellyfish (Cyanea capillata) and mauve stinger (Pelagia noctiluca) and one hydrozoan, the Portuguese man of war (Physalia physalis) were chosen as the study organisms. The Portuguese man of war is notorious for its major outbreaks in European coastal waters where it negatively impacts tourism. In 2016, P. physalis stranded in large numbers along the Irish coastline. A Lagrangian particle-tracking model revealed their origin and drift trajectories throughout the European basin prior to stranding in Ireland. The model was validated by comparing offshore and coastal observations of P. physalis and may be useful for the forecasting of future stranding events. First aid management of jellyfish stings has always been a contentious issue. In this study, envenomation models were used to evaluate sting management protocols for C. capillata, P. noctiluca and P. physalis. It was revealed that rinsing with vinegar deactivated nematocysts and the use of a hot-pack treatment reduced venom activity, thus, these were the most effective treatments for all three species. Ineffective protocols may cause some nematocyst types to discharge. Some nematocyst types are potentially more toxic than others. Therefore, a greater understanding of their distribution is essential. An investigation of the nematocysts of C. capillata and P. noctiluca, the two most problematic species in Ireland, revealed that the abundance and size of most nematocyst types did not differ along the length of their tentacles but that all nematocyst types differed between the two species. In addition, when nematocysts were enumerated, it was revealed that C. capillata have three orders of magnitude more nematocysts than P. noctiluca. Not only do jellyfish sting humans but they also sting fish held in pens. Several mitigation measures have been proposed but none have proven sufficiently effective. Therefore, as a first preliminary step toward the development of a new treatment, the effects of C. capillata venom in Atlantic salmon (Salmo salar) were investigated. More specifically, whole blood from S. salar was exposed to C. capillata venom and the specific haemolytic effects were examined. As a result, venom immediately caused significant haemolysis. It is hoped that the research presented here has filled in some of the knowledge gaps in jellyfish research in Ireland and globally and aided the development of mitigation measures to reduce their future impact.