MacMillan Pier showing the docks, fishing vessels, and tour boats. View from the Pilgrim Monument looking south. On the east side (left), two floating dock complexes are closest to shore followed by two finger piers near the end of the main pier. On the west side (right), a long row of tour boats line the pier. The ferry terminal to Boston is located at the end of the pier on the west side (right).
During the 2015-2017 summer seasons, the docks were inspected for invasive species in the MIMIC program (Coast Watch 2011, Coast Watch 2012). The most abundant attached species were the colonial ascidians Botryllus, Botrylloides, Didemnum, and Diplosoma, and the solitary ascidian Styela. The one exception to the general abundance of ascidians was the rare ocurence of the solitary species Ascidiella aspersa, which has been periodically seen at low frequency in Provincetown (several years only 1 specimen), but not seen in 2017. Interestingly, the translucent solitary species Ciona intestinalis and Molgula manhattensis, cryptogenic species not included in the survey have also been observed at low frequency whereas the colonial species and the solitary Styela are common all over the marina. Perhaps these three translucent species are out-competed and crowded out by the colonial species which spread throughout the marina in the summer. Interestingly, Molgula manhattensis is abundant in Wellfleet marina, a location with very low species diversity and few colonial species of any kind.
The rock shrimp Paleomon is easiest seen in late summer when they have grown larger than Paleomonetes shrimp and the blue bands on their legs are prominently displayed. Unlike the other species in the program, Paleomon requires an active search for individuals by running a net along the sides of the floating docks where algae and hydroids are numerous and closely inspecting the shrimp for morphological features.
The Asian red alga Grateloupia has been a consistent member of the floating dock community albeit at relatively low frequency in comparison to other invasives. It is usually found on the same docks where Codium is located near the pilings that hold the docks in place. An analysis of of the MIMIC data presented on the MORIS website for the distribution of Grateloupia along the MA/NH/ME coast indicates that it has not yet been reported yet at MIMIC sites north of Boston and has remained in southern New England since it was first observed in the Gulf of Maine in 2007. Other MA sites where it has been observed include the east end of the Cape Cod Canal at Sandwich, Onset and New Bedford on Buzzards Bay, and Fall River on the upper Naragansett Bay.
Codium fragile on Floating Dock
Grateloupia turuturu on Floating Dock
During the last 2 years, the bryozoan Bugula neritina has remained a common species on the docks along with a newly identified invasive bryozoan Tricellaria inopinata. The bryozoan Tricellaria was first identified in Massachusetts in 2010 in Eel Pond, Woods Hole, lower Cape Cod (Johnson et al, 2012) and was reported in the Gulf of Maine during the 2013 Rapid Assessment Survey (RAS), where it was given the common name "unexpected bryozoan". I have seen Tricellaria since I started monitoring (unidentified beige bryozoan in my November 2012 Bugula neritina post (MIS Branching Bryozoan), but I only became aware that it was an invasive species in 2016. On the floating docks, Bugula and Tricellaria grow in the same niche and frequently cohabitate together. Last July, the colonies were typically only a few cm high and newly settled juveniles were common. Tricellaria has a distinctly different microscopic growth pattern from other native, beige Bugula species (zooids point toward the anterior whereas they are alternately opposed to each other in Bugula). This pattern could be discerned in the lab under a dissecting microscope and can be seen at the docks with a 20x or 30x magnifying lens. During the summer of 2017, Tricellaria was particularly abundant and overgrew other species like the green algae Ulva and Codium.
In contrast to the branching bryozoa, the encrusting bryozoan Membranipora membranacea has not been seen much in Provincetown despite the expectation that it might be seen on a floating dock. The rare times it has been seen has been on kelp growing on the dock or plastic dock trim that was submerged in the water. The marina does not seem conducive to other encrusting bryozoans either, since the native encrusting broyzoans Electra pilosa and Schizoporella unicornis, are also rarely seen.
Mathieson, AC, Dawes, CJ, Pederson, J, Gladych, RA, and Carlton, JT. The Asian red seaweed Grateloupia turuturu (Rhodophyta) invades the Gulf of Maine. Biol. Invasions 10: 985-988, 2008.
Johnson, CH, Winston, JE, and Woollacott, RM. Western Atlantic introduction and persistence of the marine byrozoan Tricellaria inopinata. Aquatic Invasions 7: 295-303, 2012.
MORIS: CZM's Online Mapping Tool.