Persistent differences between coastal and offshore kelp forest communities in a warming Gulf of Maine
Fig 5
Temporal variation in average S. latissima density at Ammen Rock Site 1 during four sampling periods from 1987 to 2015.
A significant 36.2% reduction of average kelp density occurred between 1987 and 2015 (S4 Table). The low kelp densities in 2012 occurred during anomalously warm sea surface temperatures (Fig 2, S1 and S2 Figs) when the kelp plants were extensively covered by the invasive bryozoan Membranipora membranacea (Fig 6E, S5 Table). The boxplots display the median value of the data as a horizontal bar, the first and third quartiles of the data (25th and 75th percentiles) as a shaded box around the mean, 1.5x the interquartile range (IQR) as a vertical line, and all outliers beyond +/- 1.5 IQR as individual dots. The diamond symbol represents the mean value.