Harmful algal blooms, known to produce potent toxins that may affect the ecosystem, human activities and health, have increased in frequency and intensity worldwide in the past decades. Numerous processes involved in Global Change; are amplified in the Arctic, but little is known about species specific response of artic dinoflagellates. The aim of this work was to test the effect of temperature on growth, and production of Yessotoxins and lytic compounds by Protoceratium reticulatum isolated from Greenland. Six clonal isolates, the first isolates of P. reticulatum available from arctic waters, were characterised by morphology and sequencing and were shown to produce both yessotoxins (YTXs) and lytic compounds, which is the first report of lytic activity for P. reticulatum. Growth was strongly affected by temperature with a maximum growth rate at 15°C, with significant but slow growth at 1°C and cell death at 25°C. Generally, these results suggested an adaptation of P. reticulatum to temperate waters. Temperature had no major effect on YTXs cell quota or lytic activity. Nevertheless, both parameters were affected by the growth phase with a significant increase at stationary phase. A comparison of all six isolates at a fixed temperature of 10°C showed high variability between the isolates for all three physiological parameters tested. Growth rate varied from 0.06 to 0.19 days-1 and YTXs from 0.1 to 24.1 pg YTXs cell-1. The all six isolates performed lytic activity at stationary phase, however only four displayed measurable lytic activity at stationary phase.