Understanding the dynamics of an estuary is not easy but it’s infinitely fascinating. There’s constant shifts in the salinity of the water, the clarity of the water and the presence or absence of certain species, particularly algae. Algae comes in many forms; there are tiny, microscopic algae that float in the water, also called phytoplankton, and there are large, rooted and un-rooted seaweeds called macroalgae. The reason scientists want to study algae is that algae love nutrients. When there’s a lot algae in the water it most likely means there is a lot of nutrients in the water, particularly nitrogen. Algae also cope with decreased water quality better than aquatic plants do. Aquatic plants, like eelgrass, have a harder time surviving when water quality and clarity decreases, but algae can continue to survive and grow. Algae can also entangle and smother eelgrass and cause it to die off. Since a healthy balance of species is important in an estuary, this can create a problem.
|Ulva Lactuca AKA Sea Lettuce is a common macroalgae|
Macroalgae has been largely understudied in the Great Bay Estuary. Baseline studies were done by UNH researchers in 1972 and 1980 and then again in 2008-2010. It was discovered that in some locations there were increases of macroalgae cover of up to 90%. The 2013 State of Our Estuaries Report specifically noted that more data collection and study were needed to gain a greater understanding of the extent and causes of these increases. This summer and fall Dr. David Burdick from the UNH Jackson Estuarine Lab along with his graduate student Elisabeth Cianciola answered that call.
Between August 16th and September 13th researchers and volunteers visited 175 random locations. Thirty-eight of these sites were dominated by macroaglae, 24 were dominated by eelgrass beds, and 12 were dominated by saltmarshes. The remaining sites had no vegetation or could not be assessed at the time of the visit. The researchers and volunteers donned wader boots, paddled by kayaks or motored in a boat to these locations throughout the Great Bay Estuary and the tidal rivers that flow into it.
|This image shows the 175 random locations in the Great Bay Estuary that were sampled and the dominant ground cover type found.|
This research provides PREP and our partners with important data showing what’s really happening with macroalgae in our estuaries, and, more importantly it helps us to gain a better understanding of how macroaglae respond to increasing nutrients and how macroalgae may influence nutrient cycling. The random sampling survey was also timed to coincide with the collection of high-resolution aerial imagery for PREP’s eelgrass monitoring efforts. This on-the-ground effort can also help in the important ground truth effort for that research. Complete analysis of the data collected by Elisabeth and Dr. Burdick will be available in May 2014.
|Elisabeth uses a quadrat to measure macroalgae cover off Four Tree Island, Portsmouth, NH.|
Elisabeth and Dr. Burdick’s research was funded collaboratively by New Hampshire Sea Grant, UNH William R. Spaulding Marine Program Endowment, The Martha and Theodore Frizzell Scholarship Fund and PREP. The field work would not have been successful without the cooperation and help from many at UNH, the Coastal Research Volunteers, the Great Bay National Estuarine Research Reserve, the Great Bay Stewards and NH Dept. of Environmental Services.