Date of Award
2009
Degree Type
Thesis
Degree Name
Master of Science in Oceanography
Department
Oceanography
First Advisor
John King
Abstract
Identification of spatial and temporal patterns in ecosystem processes and habitats across various scales is at the core of ecological research. As human activities continue to place increasing pressure on marine and coastal ecosystems, ecosystem-based management that includes an understanding of such patterns and embraces complexity is needed. Habitat classification and mapping can be used to identify existing patterns, spatial and temporal scales of variability, and locations vulnerable to human-induced changes. To truly examine ecosystem dynamics, characterization of habitat response to stressors should be paired with conceptual and quantitative models of ecosystem and stressor dynamics.
Quonochontaug Pond, a coastal lagoon on Rhode Island’s south shore, was used as a study area for both habitat classification and examination of physical processes influencing episodic hypoxia. A habitat classification scheme developed as a modification of NOAA’s current Coastal and Marine Ecological Classification Standard (CMECS) draft was used as a framework within which to organize and present habitat data. Water column abiotic and benthic abiotic and biotic habitats were classified at several spatial and temporal scales and are presented in a variety of visual formats. Habitat classification was also used as a means to explore potential links between water column and benthic properties.
Fluctuations in dissolved oxygen concentrations have been shown to influence benthic biological communities and represent a water column variable potentially linked to benthic habitats. Responses of biota to episodic hypoxia in Quonochontaug Pond’s western basin were examined using a habitat classification and mapping approach. System dynamics and forcing mechanisms responsible for spatial variability in hypoxia occurrence and severity were investigated in detail using in situ records of water column properties and surveys of water column velocities.
Geomorphology and circulation patterns restrict hypoxia to the western basin of the pond and spring tides, precipitation events, and low northeast wind stress are all forcing mechanisms responsible for dissolved oxygen concentration dynamics. Results also show that tidal and diel mechanisms may push shallow coves toward hypoxia thresholds and, thus, increase their vulnerability to hypoxia during climatological (e.g., wind and rain) forcing events. Benthic infaunal communities in these coves also appear to exhibit responses to episodic hypoxia. In the far western end, these responses manifest as depressed levels of overall abundance and diversity and absence of tube-building amphipod populations. In Harmonic Cove, a cove in the western basin, declining populations of tube-building amphipods from spring to late fall may have been induced by episodic hypoxia.
In addition to a conceptual model of Quonochontaug Pond’s ecology, using a classification and mapping approach to habitat study resulted in generation of hypotheses, elucidation of scales at which habitat patterns emerge, and information of use to future monitoring and research efforts. This case study highlights the importance of including biological and water column data in habitat classification and mapping projects and of using a classification framework the structure of which permits analysis of multiple habitat components in a logical, ecologically sound manner. Results from this study also emphasize the need for flexibility at finer scales of resolution and the use of a bottom-up classification approach. Using such a framework can highlight complexity and spatial variability while providing a means by which important patterns can be assessed, communicated, and used to inform management actions. In these ways, the habitat classification and mapping approach demonstrated here can provide a foundation for ecosystem-based management by shaping the ways that marine and coastal habitats are viewed, discussed, and valued.
Recommended Citation
Guarinello, Marisa L., "Habitats in a Rhode Island Coastal Lagoon Experiencing Episodic Hypoxia" (2009). Open Access Master's Theses. Paper 2464.
https://digitalcommons.uri.edu/theses/2464