Evaluating the Effects of Habitat Characteristics on Initial Oyster Settlement and Post-settlement Survival Across Multiple Spatial Scales

Abstract

The connection between spatial scales and ecological processes is a fundamental concept in ecology. The distribution and abundance of organisms rely on various habitat characteristics that vary across spatial scales. In marine systems, where habitat connectivity is high, considering both small and larger spatial scales can offer a more comprehensive view of both species population dynamics and community relationships. The Eastern oyster (Crassostrea virginica) is a foundational species that has a broad distribution across temperate estuaries and exists in heterogenous landscapes, co-existing closely with marshes, sandflats, and seagrass meadows. Since oyster reef populations have declined drastically over the past century and provide essential ecological services, considerable efforts have been allocated to ensure they continue to persist along our coastlines. Although restoration efforts are widespread, their success has been variable and often limited. Because post-settlement survival is fundamental to the persistence of oyster reefs, understanding potential ways these processes can be enhanced are critical to improve restoration efforts. Recent restoration approaches have capitalized on positive species interactions to enhance success. Since oysters and seagrass are both structurally complex habitats that inhabit the same tidal elevation zone, they are likely to exhibit strong ecological interactions with one another. While previous studies have examined their interactions, the relationship remains complex and requires further investigation to understand underlying mechanisms that may be leveraged in restoration.

In this study, I investigated the impact of habitat characteristics on post-settlement survival of Crassostrea virginica across multiple spatial scales in North Carolina. Through field experimentation and geospatial analysis, I investigated trends at the regional, local, and seagrass bed scales. I found that: 1) at the regional scale, there were large differences in post-settlement survival between sites; 2) at the local (within site) scale, proximity to adjacent marsh and oyster habitats significantly influenced post-settlement survival patterns; 3) at the seagrass bed scale, elevation drove patterns, while fine-scale seagrass characteristics had minimal impact on post-settlement survival. These findings have important implications for restoration strategies in North Carolina, further supporting work that shows enhancing post-settlement survival should be a priority as larval supply does not appear to be limiting in the region.