nMDS plot displaying differences between community composition in the 1994–2000 survey, the 2011 survey, and the 2019–2020 survey. The sites used for comparison, and their corresponding abbreviations, are consistent with the 1994–2000 survey. The sites and abbreviations are the same as in Fig. 2. Red represents the 1994–2000 sites, green the 2011 sites, and blue represents the 2019–2020 survey sites. The clusters of sites for 2019–2020 occur in between two clusters of 2011 survey sites. There are two visual clusters, one of the 1994–2000 data, and the other consisting of both the 2011 and 2019–2020 data.