Below is the abstract from: Audrey Pleva and Joseph Luczkovich. 2013. Effects of salinity on submerged aquatic vegetation’s growth and abundance in North Carolina and assessment of a SONAR’s accuracy to measure vegetation. Unpublished report, Department of Biology, Institute for Coastal Science and Policy, East Carolina University, Greenville, NC 27858. Contact Dr. Luczkovich if you have questions or would like a copy of the report. Contact Navico to get updated (cheaper) pricing from what is cited in the report and to get you started assessing seagrass habitats with Lowrance/Simrad and BioBase!
Submerged aquatic vegetation (SAV) is one of the most important estuarine habitats supporting commercially and recreationally important fishes and invertebrates, providing species food and shelter from predation. Salinity levels, an important factor in SAV growth and survival, are rising in North Carolina due to sea level rise bringing salty water from the Atlantic Ocean into NC, posing a threat to freshwater species. SAV species adapted to a certain salinity level are stressed by long and short term changes in salinity, resulting in patchy or smaller beds. In this project, a recently developed survey technique based on a combined video and echosounder system was used to measure the SAV % cover at three sites, each with different long-term and short-term salinity levels. Our hypothesis was that large short-term changes in salinity would be a stressor for SAV, and that as the range in salinity and the average long-term salinity increased, SAV % cover would decrease. We measured changes in water quality including salinity, temperature, and dissolved oxygen, and SAV cover using boat-based SONAR techniques at Jarrett Bay (JBS), Blount’s Bay (BLB), and Currituck Sound (CTS) in North Carolina during the beginning of the growth season where salinity is a very important growth factor. SONAR data were collected along 30 transects at 10-m intervals across the study area at JBS and BLB, but 60 transects at 25-m intervals at CTS. The accuracy of the SONAR technique was assessed using underwater video at 100 randomly selected points along transects at each site. Accuracy was very high (87.8 %) and relatively equal between all three sites. The salinities and % cover were highly variable among sites, in both the short- and long-term measurements, allowing for an analysis of the relationship between SAV and salinity. Overall mean long-term salinity was negatively correlated (r = -0.7) with SAV percent cover. Short-term salinity increases may cause declines in SAV cover, as freshwater species are displaced by salinity-tolerant SAV species.
See an online pdf of a presentation recently given by Dr. Luczkovich describing some of these results.