Honors College

Document Type

Honors Thesis


Marine Science


Paul Rawson

Committee Members

Timothy Bowden, Ian Bricknell, Samantha Jones, Sally Molloy

Graduation Year

May 2021

Publication Date

Spring 5-2022


Restoration projects on the oyster reefs in Great Bay, NH have been active since 2009 with the most recent involving the transfer of oysters from Maine oyster farms into the Bay. In an attempt to prevent the transfer of non-native species from oyster farms to the reefs, samples of oysters from each farm were inspected for shell-boring polychaete infestations. Polydora websteri, a common shell-boring species worldwide, was in high abundance in reference samples from oyster farms in Great Bay and in samples from the restoration grounds, themselves. A second shell-boring species, provisionally identified as P. onagawaensis, is present on oyster farms in Maine but has not been observed previously in Great Bay. I used microscopic analysis of morphological features and molecular analysis of the mitochondrial CO1 (mtCO1) gene to identify worms extracted from the oyster samples from Maine farms to species, when possible. When intact worms could not be extracted from the shells, I used the shape of their burrows, which is distinct for P. websteri and P. onagawaensis, to infer the presence of the latter. I found that the abundance of shell-boring polychaetes was variable along the coast of Maine, with farms in close geographical proximity having very different loads of burrows and worms. Both P. websteri and P. onagawaensis were identified by molecular analysis on some Maine farms while only P. websteri was found in the samples from New Hampshire farms and restoration sites.