Borrowing ecological principles: Influence of reef placement and habitat complexity on free-living and parasite diversity

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Nina Cecilia Woodard (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Environmental factors often shape and regulate the distribution of community assemblages throughout an ecosystem. For example, in the rocky intertidal zones, marine ecologists have identified abiotic forces and biotic forces that have shaped and regulated the distribution of species through careful observation and experimentation. The paradigm of the rocky intertidal is what sets the upper and lower distributions for many species, and as a result, it has the potential to serve as a model system for other ecosystems, including soft sediment intertidal systems where oysters serve as a key biogenic habitat for organismal recruitment and species assemblages. \n The environmental forces regulating community assembly in the rocky intertidal ecosystem could be examined within a biogenic habitat to ultimately serve as a guide for habitat restoration. Eastern oyster (Crassostrea virginica) populations have declined significantly in estuaries along the United States Atlantic coast due to coastal development, pollution, and sediment accumulation. Oysters are well known for their ecosystem services, creating three-dimensional reef structures that provide substantial coastal protection, attenuating wave energy and providing structural habitat for mobile and sessile organisms. Past studies have mostly explored how substrate composition and environmental factors affect oyster settlement and growth. Fewer studies have explored substrate placement may affect oyster development. Placement relative to the reef (landward/seaward) and reef relief (high/low) directly affects oyster development as well as biodiversity, altering hydrodynamics and sedimentation. \nAdditionally, placement and reef relief can affect habitat availability and structural complexity within a reef, subsequently affecting mobile and sessile diversity and survival. In addition, recent work has shown the importance of parasites as a part of, and sometimes in explaining, community biodiversity. Still, little is known about the role of parasites in oyster reef communities. With these gaps in knowledge, a more in-depth study was needed to determine the roles of placement and habitat complexity in the establishment and evolution of restored oyster reefs. I conducted field surveys and experiments to evaluate how reef placement and reef-relief affected free-living and parasite diversity. \nThis study took place in the Rachel Carson Reserve located in Beaufort, NC, United States. I had 12 study sites along the Taylor’s Creek marsh shoreline, four low-relief sites, four high-relief sites, and four control sites. At each site, two passive samplers were placed landward and seaward of the reef. Over a one-year sampling period, I collected ten host species (five fish species: naked goby, seaboard goby, crested blenny, feathered blenny, and oyster toadfish\; and five crab species: stone crab, common mud crab, white-fingered mud crab, black-fingered mud crab, and flatback mud crab) and recorded their abundance. The collected species were then dissected and checked for parasites under a microscope. In addition, abiotic measurements including water temperature (?C), dissolved oxygen (mg/L), and salinity (ppt) were collected. \nI predicted that the landward side of restored oyster reefs would support higher mobile fauna (both free-living and parasitic organisms) species abundance and richness and that the seaward side of restored oyster reefs would support higher sessile fauna abundance and richness. I also predicted that the high-relief reefs would ultimately support the highest biodiversity for both mobile and sessile fauna. For sessile fauna, this prediction was upheld, with the exception that reef-relief did not seem to have an overall effect on sessile species abundance, only placement. However, this prediction was not upheld for mobile free-living fauna. In fact, results from my statistical analyses showed that mobile fauna abundance was greatest seaward of control plots. This result could suggest that structure within a habitat is a driver of species diversity, where the control sites had two passive samplers placed landward and seaward, despite no physical reef being present. In addition, parasite prevalence in crab and fish host species was low, finding no differences between the two placements and three reef reliefs. Such low abundances could be a result of the young age of our restored reefs, 1 year. One year post reef restoration may be insufficient to see free-living and parasitic communities matching that of a natural reef. Altogether, this study provides important information on the importance of structure within a given community and time to allow biodiversity to match that of an older or natural reef. Future restoration projects should consider time as a predictor of restoration success.

Additional Information

Publication

Thesis

Language: English

Date: 2023

Subjects

Oysters;Reefs;Restoration;Parasites;Biodiversity;Biogenic;Rocky;Intertidal

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