The effects of Salinity, Depth, and Turbidity on Submerged Aquatic Vegetation (SAV) abundance in Eastern North Carolina

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

Noah Scott Gwynn (Creator)

Institution

East Carolina University (ECU )

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

Abstract: The state of North Carolina is concerned about the loss of submerged aquatic vegetation (SAV), which is critical fish and wildlife habitat in low-salinity estuaries. Sentinel sites have been established by the East Carolina University/Albemarle Pamlico National Estuarine Partnership (APNEP) SAV monitoring team at locations where SAV has been observed in historical surveys. Using monitoring data collected from low-salinity sentinel site locations in the Neuse River Estuary (NRE), Pamlico River Estuary (PRE), and Albemarle Sound (AS) from 2015 to 2019, I evaluated the effects of turbidity (measured by Secchi depth), salinity and water depth on SAV abundance (odds of occurrence, percent cover, percent frequency, and dry biomass). The maximum colonization depth of SAV was also analyzed. My goal was to understand what physical factors impact low-salinity SAV survival and growth in North Carolina estuaries by focusing on the three dominant species found (Ruppia maritima, Vallisneria americana, and Zannichellia palustris). Data came from inshore quadrat diver surveys that measured percent cover using 1 m2 quadrats at depths of 0.25, 0.5, 0.75, and 1 m. Dry biomass abundance was determined by taking core samples along sampling transects. An ensemble data set from North Carolina Department of Environmental Quality (NCDEQ), Modmon, and North Carolina Department of Marine Fisheries (NCDMF) data bases) was used to create inverse distance weighted prediction models of Secchi depth and salinity for use in analysis of maximum colonization depth of SAV. SONAR methods included the use of Lowrance single beam 200khz echosounder to measure maximum colonization depth of SAV along 40 transects per sentinel site. Some sentinel sites were omitted from the analyses because they contained no SAV during the monitoring period. I observed that water transparency also called turbidity in this thesis (measured by Secchi depth), salinity, and water depth had significant effects on dominant SAV species with the direction of the association being species dependent. Ruppia maritima odds of occurrence increased with salinity, water depth, and turbidity. Vallisneria americana odds of occurrence showed a negative association with turbidity and salinity but a positive correlation with water depth out to 1 m. Zannichellia palustris odds of occurrence showed no significant effect with turbidity and salinity but was significantly associated with increased water depth. Differences in SAV species salinity and water transparency responses suggest these two factors contribute significantly to the distribution of dominant SAV species. Maximum colonization depth of SAV is greater in sentinel sites with higher Secchi depths, especially when a long-term average Secchi depth is used (ensemble data set). Ruppia maritima has been predicted by my logistic regression model and field observations to be favored in the competition among North Carolina SAV species.

Additional Information

Publication

Thesis

Language: English

Date: 2023

Subjects

SAV

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