Northern Coastal Basin (NCB) Intercoastal Oysters (SJRWMD)

Published: 3 October 2017| Version 1 | DOI: 10.17632/vz26hhjff7.1
Contributor:
Stephanie Garvis

Description

The eastern oyster, Crassostrea virginica, has been classified as an ecosystem engineer as well as a keystone species because of the important benefits that oysters and oyster reefs provide. Due to their three-dimensional structure, oyster reefs are able to maintain high levels of biodiversity. Many economically and ecologically important species can be found using the oyster reefs, including shrimp, stone crabs, blue crabs, and spotted sea trout. Certain fish species also use oyster reefs as nesting areas. Oyster coverage has decreased for several reasons: habitat destruction, disease, overharvesting and reduced water quality. The severe loss of the eastern oyster, Crassostrea virginica, has encouraged different types of conservation, mapping, monitoring and restoration efforts throughout its native range, including within the Northern Coastal Basin (NCB) region. The purpose of this project is assess the current area of natural and dead oyster reefs within the NCB area using a suite of aerial photographs and supplemental imagery information provided by Saint Johns River Water Management District using ArcGIS software. UCF developed a photointerpretation key that contains examples of all oyster habitat classification types delineated for the study and includes both textural descriptions of the classification types along with aerial photo clips that are clearly delineated to show users the different oyster signatures. All oyster habitats were mapped to the level of detection (no minimum mapping unit). Oyster reefs were identified based on the following criteria (i.e. "signature"): globular or irregular in shape, dark margins with a slightly lighter middle area, and with a smooth texture. Most reefs were located near mangrove islands at a shallow bathymetry, due to the fact that oysters are intertidal throughout the NCB area. Narrow, fringing oyster reefs that were obscured by vegetation may not have been detected in our study. Scattered live clusters were included if they were detectable on the aerial imagery, and were assigned the subclass of 'aggregate' within the 'live' class. Only dense clusters of live oysters were included in the 'live' class and the 'continuous' subclass. Dead reefs were identified based on the following criteria: bright white reflection due to bleached disarticulated shells that are continuously exposed, even at high tide. Dead reefs are found either adjacent to existing oyster reefs or standing alone, typically located on main boating channels. The results of this project create a baseline for oyster habitat within the region, which can serve to study potential negative impacts to reef area coverage over time. An accuracy assessment was performed and found the oyster reef habitat classification to be 96% accurate. The original mapping effort by UCF will continue to be edited and refined as more resources become available. Updates will be described in the maintenance section of the metadata.

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