Interpreting the results of two tests of randomness

I have a series of more than 1000 numbers which are not supposed to exhibit any particular trend, regularity or non randomness. The numbers are the results of tests for the presence of substances in various samples of liquid kept in various conditions. The numbers are known to form a Poisson distribution, as most samples and treatments give low test values. I have run Bartels Rank Test and Mann Kendall's Test on the data using R, and I have these results:

Bartels Ratio Test

data:  c(t[, 3], t[, 4])
statistic = -0.27283, n = 1314, p-value = 0.785
alternative hypothesis: nonrandomness

Mann-Kendall Rank Test

data:  c(t[, 3], t[, 4])
statistic = -5.9172, n = 1314, p-value = 3.275e-09
alternative hypothesis: trend

Am I right in believing that these test results have opposite meanings, Bartel's saying the series is random and Mann-Kendall saying it isn't? Can anyone cast light on what the results are trying to tell me?