showed a trendp = .095
The ‘high’ invasion front showed a trend towards higher velocity in 30 PSU (Welch's test, t 17.488 = 1.76, p = .095), significantly higher velocity in 25 PSU ( t 17.488 = 2.38, p = .029) and 20 PSU ( t 28.79 = 3.14, p = .004) and significantly lower velocity at 1 PSU ( t 31.557 = −2.34, p = .026), compared with the ‘low’ invasion front.