Fig 1.
a-c) Map of the Swan River showing the 12 sites sampled in April and June 2014 and March 2015. Green indicates Didemnum perlucidum growing on seagrass and artificial substrates, blue indicates D. perlucidum growing only on artificial substrates and not seagrass, red indicates no presence of D. perlucidum. d-f) Percent cover plus standard error of D. perlucidum on seagrass at each site in April, June and March. Sites are along the horizontal axis and run from the lower estuary upstream towards Perth CBD. (Site name abbreviations: GR- Gilbert Fraser Reserve, ZR–Zephyr Café, CP–Chidley Point, MB–Mosman Bay, PW–Point Walter, FB–Freshwater Bay, CL–Claremont, PT–Point Resolution, M–Matilda Bay, HT–Heathcote Reserve)
Fig 2.
Didemnum perlucidum on seagrass, a navigation marker and bare substratum.
Table 1.
Analysis of Variance by Permutaion (PERMANOVA) testing for differences in percent cover of D. perlucidum among sites (random factor), times of the year (random factor) and transects (random factor nested in site).
The analyses were based on Euclidean Distances calculated from Log(x+1) transformed data.
Table 2.
a) DistLM marginal test of contribution of factors to D. perlucidum distribution and b) model selections (Biological data square root transformed, Bray Curtis similarity, predictor environmental variables normalised, AICc selection criteria, stepwise selection procedure).
Fig 3.
Dry weight biomass of Halophila ovalis with and without D. perlucidum.
Colonies sampled and pooled from 5 sites in April and June 2014 and March 2015.
Table 3.
Analysis of Variance by Permutation (PERMANOVA) testing for differences in H. ovalis biomass with and without D. perlucidum (fixed factor), times of the year (fixed factor) and sites (random, nested in season).
The analyses were based on Euclidean Distances calculated from Log(x+1) transformed data.
Fig 4.
a) Relative light curve of H. ovalis tissues with and without D. perlucidum. b) α and ETRmax of H. ovalis tissue. D = plant tissue which had been covered with D. perlucidum colony. ND = plant tissue not impacted by D. perlucidum
Fig 5.
Relative health index of H. ovalis leaves with and without D. perlucidum.
1 = alive (green), 2 = alive with necrotic patches (green with brown spots), 3 = dead (various shades of brown).
Fig 6.
Counts of Batillaria australis with and without D. perlucidum colonies sampled from 9mm sediment cores and pooled from 3 sites in April and June 2014 and March 2015.
(n = 9 with D. perlucidum per site and 9 without D. perlucidum per site).