A Novel Monitoring Framework to Assess Intertidal Biodiversity in Mixed Coarse Substrate Habitats across the Boston Harbor Islands

The Northeast U.S. coast is experiencing some of the fastest rates of sea level rise in the world. The Boston Harbor Islands National Recreation Area is particularly at risk from sea level rise and coastal storm impacts. Erosion and storm impacts have already led to the degradation of shoreline habitats and protective structures (e.g., sea walls), as well as direct impacts to historic landmarks on some islands. The need to establish reliable methods for inventory and monitoring of marine nearshore habitats has emerged out of an effort to use the Boston Harbor Islands as study sites to understand how experimental manipulation of the coastline (e.g., the installation of in-water reefs) might reduce wave energy and erosion and protect intertidal and upland resources.

The final design of any new adaptation or construction project on the Boston Harbor Islands must consider all possible impacts to coastal habitats and the broader socio-ecological system. Questions currently under consideration include: Can managers manipulate the coastline while maintaining biodiversity and minimizing risk to species of high conservation concern? Where are the optimal sites for testing installations? What species are threatened, keystone, and/or unique across the Boston Harbor Islands and should be tracked before and after experimental manipulations? Initial scoping work for proposed adaptation or construction projects has shown that a standard protocol for mixed coarse (sandy, cobble) substrates – the primary intertidal habitat surrounding sites of interest - does not currently exist, nor does a current inventory of marine biodiversity in the Boston Harbor Islands. Thus, new work needs to be conducted that can be implemented across the Boston Harbor Islands to assess baseline conditions and select sites for anticipated coastal adaptation actions.

In the first phase of work completed as part of the initial project “A Pilot Biodiversity Inventory and Monitoring Protocol in Support of Coastal Adaptation Projects in Tidal and Nearshore Subtidal Habitats of Boston Harbor Islands”,  this project 1) synthesized biodiversity records of species living in and using mixed coarse substrate habitats of the intertidal zone of the Boston Harbor Islands; 2) identified and compiled methods to develop a standard and repeatable monitoring protocol to track changes (natural or anthropogenic) in intertidal biodiversity over time and across locations; and 3) conducted preliminary site scoping of target islands to identify locations for collecting new baseline data.

The current second phase of work will: 1) test and calibrate existing protocols to quantify and track the unique biotic assemblages associated with mixed coarse substrate habitats, 2) collect current baselines of habitat classification and biodiversity data at key sites, and 3) develop a novel monitoring framework that can be implemented by the NPS and its partners moving forward.