Aquatic macroalgae are homes to a diverse assemblageof epifauna. These assemblages varyacross different macrolage and substrate. Non-native foundationmacroalgae species that invade habitats already occupied by native foundationspecies can alter the composition and assemblage of native epifauna. With the recent explosion of Starry Stonewortin the Great Lakes, it’s important to understand how this invasion can effectnative organisms that depend on the native foundation species. In this field observation, we will look intothe possibility of a cascading effect that the invasion of Starry stonewort mayhave in Lake Erie. With observations ofareas of varying levels on invasion, abundances of fish can be compared andanalyzed to determine if Starry stonewort has a negative effect on the fishpopulation.
The results will help tobetter understand what conservation efforts are needed to maintain healthylocal fish populations. Introduction The invasion of non-native species has had a negativeeffect on the biodiversity and abundance of the native species in a community(Gestoso 2010). The impact these specieshave on local communities may be detrimental to the health and structure of thenative flora and fauna as their impact can travel through trophic levels(Tilman, 1999) (Mack et al. 2000). Theintroduction of new species can become a threat due to their ability tooutcompete, consume, or infect native species in a community (Ruiz et al.
1997). The lasting impact of these canlead a community to decline in native species richness and diversity(Williamson 1996). Some species, such asfreshwater macroalgae, can have an extreme impact on local communities whileremaining difficult to detect and manage. These impacts can be seen as a direct result of their colonization orindirectly through the species they affect (Schmidt & Scheibling2006). Macroalgae are consideredecosystem engineers as they are responsible for adding spatial complexity tothe substrate, modulating resources, and effecting the assemblage of epibiota(Schmidt & Scheibling 2006). Withall of this responsibility, an invasive macroalgae can certainly have adetrimental effect to a community as it works its way through each trophiclevel. It can dominate certain areas andcreate a homogenization of florals by suppressing native plants (Kuhn and Klotz2006).
Nitellopsis obtusa, or Starry stonewort, is a speciesof macroalgae that can grow up to 2 meters in height and in depths of up to 10meters (Pullman & Crawford 2010). Theyform in dense algae beds that stretch across the landscape (Simons and Nat1996). Though it is beneficial and endangeredin its native location of Europe and Asia, it has thrived and become a nuisancesince its arrival in North America (Pullman & Crawford 2010). Starry Stonewort is thought to have first arrived inNorth America during 1978 where it made its way from the St. Lawrence River inNew York (Schloesser et al.
1985). It islikely to have arrived from ballast water on ships that enter the Great Lakes;Starry stonewort spreads when plant fragments break off and are dispersed byboats and trailers (Escobar et al. 2016). Due to their distinctive bulbils not appearing until late in the season,it can go unidentified for lengthy periods of time (Pullman & Crawford).
Otherwise, it resembles many other plants. Scientists have difficulty controlling thisspecies of macroalgae; Starry Stonewort lacks a vascular system which makes itdifficult to kill with an herbicide because the chemicals cannot be carriedthroughout the plant. These herbicidaltreatments often result in a “haircut effect” that simply trims off the top ofthe plant (Escobar et al.
2016). Invasive macrophyte algae may have adverse effects onnative fish abundances. The effect theseinvasive plants can have on a community include habitat alteration,competition, facilitate other exotic species, and provide inferior food quality(Manchester & Bullock 2000). Understanding the effects these invasives have on native populations canhelp to define how invasive algae can effect higher trophic levels and definethe ecosystem. Information on invasivemacrophytes can be used to better predict the effects of macrophyteinvasion. The effects of invasivemacrophytes on trophic dynamics are not as well-known and more research is neededto understand the system (Schultz & Dibble 2011). This is a large problem because scientists areconcerned about the harm to native plants, fish, and aquatic ecosystems. There is a lack of peer reviewed researchthat looks into the adverse effects of the invasive macroalgae (Schultz 2011).
Epifaunal assemblages arestrongly influenced by macroalgae due to its use as a refuge from stress,protection from predators, and as a source of food (Gestoso 1998). It is therefore, of the utmost importance tounderstand the effects that this highly invasive species can have on communitydynamics (Pullman & Crawford 2010). Due to dominating nature of Starry Stonewort in theGreat Lakes, I hypothesize that an increase in Starry stonewort coverage willdecrease fish abundance. To understand howStarry stonewort impacts fish abundance, observations will include locations ofvarying degrees of invasion (Gordon 1998) (Hedja et al. 2009).
Understanding the impact that Starrystonewort invasion may have on native fish populations can provide valuableinformation that can aid in the conservation efforts within local communities. MethodsExperimental Protocol-belt transectsThe study will be conducted in nearshore locations in LakeErie between 3-10 meters in depth. A 10meter transect will be placed along locations that contain aquatic vegetation. At five foot intervals along the transect, a 1m² quadrant will be used to estimate percent coverage of Starry Stonewort. At the end of the transect, the averagepercent coverage will be calculated for each location. Observations will be taken by two diversswimming along the transect while observing opposite sides.
The divers will count the number of fishfound within their field of vision as they move along the transect. These final numbers will be added togetherfor fish abundance along the transect. This method will be repeated for a total of 30 locations. AnalysisA regression analysis will be used compare the relationshipof fish abundance and percent Starry stonewort coverage.
