A Case Study in Maritime Heritage Ecology: Understanding How Structural Changes to the 1898 Shipwreck Portland Affect Biological Diversity and Colonization

Shipwrecks are irreplaceable cultural and historical resources, and they also serve as biological habitats. The physical structure of a shipwreck provides habitat for hard-bottom organisms, including sessile invertebrates (anemones, sponges) and protected areas for fish. The structure of a shipwreck is influenced by cultural and natural site formation processes over time. A key unanswered question is: How do site formation processes and changes in biological communities (ecological succession) influence one another? We studied the shipwreck Portland in Stellwagen Bank National Marine Sanctuary to answer this question, working within the interdisciplinary framework of Maritime Heritage Ecology. Analysis of sonar and video data from 2002 to 2010 and 2019–2021 revealed substantial structural changes to the bow, freight deck, and stern. Site formation on the bow and stern was clearly anthropogenic, as shown by entangled fishing ghost gear. The assemblage of sessile invertebrates in each of the three shipwreck areas also saw changes in community structure, including changes in the relative abundance of species. We also observed changes in the fish community, but these are more likely the result of regional climatic change. Overall, our study showed that ghost gear is a significant threat to Portland and other shipwrecks in Stellwagen, and that site formation drives changes in the biological community over time.