Friday, February 7, 2014

Feature Focus Friday: Creating Aquatic Habitat in Southeastern Reservoirs

Happy Friday everyone and thank you for reading AERF’s Aquatic Update!  Once a month we will highlight outstanding graduate research in our “Feature Focus Friday”.  For our inaugural FFF, we will look at work being done by researchers at North Carolina State University.  Justin Nawrocki, a PhD Candidate in the Department of Crop Science under the direction of Dr. Rob Richardson, has been looking at the age old issue of establishing native aquatic vegetation in Piedmont reservoirs.




Why do you have to “establish” native vegetation in a reservoir you might ask? Well for those a little unfamiliar with what exactly constitutes a reservoir, let’s start with a simple definition.  A reservoir is most often a man-made water body for the purpose of producing hydroelectric power, supplying water to an ever growing human population, or another resource/purpose.  Focus on the words “man-made” here.  Prior to the damming of a river to create a reservoir, the parts of that reservoir that were not a part of the river system were actually land!  This means that a native aquatic plant seed bank is virtually non-existent.  This essentially results in a large, bare bottomed water body with little to no native plant life.  These types of systems are prone to non-native plant invasions due to a lack of competition from native plant communities. 

Aerial view of "Lake" Gaston at its dam
Photo Credit:  Steve Hoyle

Reservoirs are also often destinations for recreational fishing, including sport fish such as the Largemouth Bass.  Aquatic vegetation provides critical habitat, shelter, and food for aquatic organisms and its absence can spell trouble for these delicate ecosystems.  Native aquatic vegetation provides all of these benefits WITHOUT the adverse economic and environmental effects of invasive plant species.  Unfortunately in reservoirs, a bare bottom is inviting to such harmful invaders as hydrilla and milfoil when native species aren't already present to fill that niche.  Although this topic comes highly debated in recreational fishing and science, native vegetation proves to be the best choice for habitat restoration and improvement.   
Largemouth Bass, pictured above, are one of if not the most popular sport fish in the United States.
Photo Credit:  http://www.chesapeakebay.net/fieldguide

In June of 2012, supported by the US Fish and Wildlife Sport Fish Habitat Restoration Program, work began on B. Everett Jordan Reservoir and Lake Gaston (despite the misleading name, also a reservoir) in North Carolina to assess the viability of establishing native aquatic plants in those systems.  The team from NCSU isn't only looking at vegetation however.  These researchers are also interested in the resultant effects on macroinvertebrate (aquatic insects, etc) and sport fish, particularly the Largemouth Bass.  Aside from being reservoirs in the Piedmont of North Carolina, the two couldn't be more different.  Jordan is devoid of any submersed aquatic vegetation and has only a small amount of water willow, an emergent plant, present.  Jordan also sees moderate water level fluctuation which can impede native plant restoration efforts as plants get left “high and dry”.   Lake Gaston on the other hand, has fairly stable water levels and much greater aquatic plant diversity dominated by an invader known as hydrilla.  Because of this invader, the lake has been subject to an intensive management program including the use of herbicide and grass carp to reduce hydrilla coverage.

Hydrilla, without suppression, creates impenetrable mats which cause a number of environmental and economic impacts.  
Photo Credit:  NCSU Aquatics

Over the past two years, the team has assessed the plantings of three particular species: an emergent (water willow), rooted floating (watershield) and submersed (eel grass) native  plant species.  Percent cover of each species is currently being tracked and quantified annually.  Fish assemblages (both sport fish and non-sport fish) are being monitored as well through electroshocking, a common method for gaining fish community estimates.  Macroinvertebrate sampling has also been performed each fall and the use of each individual plant species, as well as the habitat as a whole, is being tracked extensively.
Eel Grass ready for planting. 
Photo Credit:  NCSU Aquatics

Before and After look over revegetation exclosures.  
Photo Credit:  NCSU Aquatics

Electrofishing around revegetation sites.  
Photo Credit:  NCSU Aquatics

In 2013 the team hit a snag as an unusually wet spring resulted in lake levels at Jordan 4’ above normal conditions, which in turn led to the death of all plants except the emergent water willow.  Herbivory was also noted on the eel grass in both reservoirs, further thwarting their efforts.  Despite these setbacks, the group was able to collect some valuable data showing higher diversity among Gaston macroinvertebrates and more pelagic (moderate to deep zone) species found in Jordan, such as white perch and gizzard shad.  Only about 3% of all fish caught in Jordan were Largemouth bass.  Lake Gaston was dominated by littoral (shallow zone) species like bluegill.  Largemouth bass accounted for a little more of the total catch in Gaston at roughly 8%.  This is likely being seen because of the absolute persistent lack of submersed vegetation in Jordan as compared to a more robust amount of vegetation in Lake Gaston. 

An unexpected catch, this extremely large grass carp specimen was caught during sampling of Lake Gaston. 
Photo Credit:  NCSU Aquatics


Although plagued by environmental conditions in 2013, the team of researchers is pushing on in 2014 completing more plantings of those native species.  Continued growth and spread of these native plants will hopefully show increased use by both macroinvertebrates and sport fish.  The group anticipates the project to continue through 2017.  The progress and completion of this study will be highlighted in future excerpts of the AERF’s Aquatic Update!  We will leave you for the weekend to investigate sport fish and vegetation interactions.  Feel free to leave us a comment or question below regarding this work or any other research done through the Aquatic Ecosystem Restoration Foundation.  Stay tuned next week for more of the latest in aquatic plant management, science, and innovation! 

Cover Photo Credit:  NCSU Aquatics

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