Aquatic macroalgae are homes to a diverse assemblage
of epifauna. These assemblages vary
across different macrolage and substrate.
macroalgae species that invade habitats already occupied by native foundation
species can alter the composition and assemblage of native epifauna. With the recent explosion of Starry Stonewort
in the Great Lakes, it’s important to understand how this invasion can effect
native organisms that depend on the native foundation species. In this field observation, we will look into
the possibility of a cascading effect that the invasion of Starry stonewort may
have in Lake Erie. With observations of
areas of varying levels on invasion, abundances of fish can be compared and
analyzed to determine if Starry stonewort has a negative effect on the fish
population. The results will help to
better understand what conservation efforts are needed to maintain healthy
local fish populations.
The invasion of non-native species has had a negative
effect on the biodiversity and abundance of the native species in a community
(Gestoso 2010). The impact these species
have on local communities may be detrimental to the health and structure of the
native flora and fauna as their impact can travel through trophic levels
(Tilman, 1999) (Mack et al. 2000). The
introduction of new species can become a threat due to their ability to
outcompete, consume, or infect native species in a community (Ruiz et al.
1997). The lasting impact of these can
lead a community to decline in native species richness and diversity
Some species, such as
freshwater macroalgae, can have an extreme impact on local communities while
remaining difficult to detect and manage.
These impacts can be seen as a direct result of their colonization or
indirectly through the species they affect (Schmidt & Scheibling
2006). Macroalgae are considered
ecosystem engineers as they are responsible for adding spatial complexity to
the substrate, modulating resources, and effecting the assemblage of epibiota
(Schmidt & Scheibling 2006). With
all of this responsibility, an invasive macroalgae can certainly have a
detrimental effect to a community as it works its way through each trophic
level. It can dominate certain areas and
create a homogenization of florals by suppressing native plants (Kuhn and Klotz
Nitellopsis obtusa, or Starry stonewort, is a species
of macroalgae that can grow up to 2 meters in height and in depths of up to 10
meters (Pullman & Crawford 2010). They
form in dense algae beds that stretch across the landscape (Simons and Nat
1996). Though it is beneficial and endangered
in its native location of Europe and Asia, it has thrived and become a nuisance
since its arrival in North America (Pullman & Crawford 2010).
Starry Stonewort is thought to have first arrived in
North America during 1978 where it made its way from the St. Lawrence River in
New York (Schloesser et al. 1985). It is
likely to have arrived from ballast water on ships that enter the Great Lakes;
Starry stonewort spreads when plant fragments break off and are dispersed by
boats 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 this
species of macroalgae; Starry Stonewort lacks a vascular system which makes it
difficult to kill with an herbicide because the chemicals cannot be carried
throughout the plant. These herbicidal
treatments often result in a “haircut effect” that simply trims off the top of
the plant (Escobar et al. 2016).
Invasive macrophyte algae may have adverse effects on
native fish abundances. The effect these
invasive 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 can
help to define how invasive algae can effect higher trophic levels and define
the ecosystem. Information on invasive
macrophytes can be used to better predict the effects of macrophyte
invasion. The effects of invasive
macrophytes on trophic dynamics are not as well-known and more research is needed
to understand the system (Schultz & Dibble 2011).
This is a large problem because scientists are
concerned about the harm to native plants, fish, and aquatic ecosystems. There is a lack of peer reviewed research
that looks into the adverse effects of the invasive macroalgae (Schultz &
Dibble 2011). Epifaunal assemblages are
strongly 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 to
understand the effects that this highly invasive species can have on community
dynamics (Pullman & Crawford 2010).
Due to dominating nature of Starry Stonewort in the
Great Lakes, I hypothesize that an increase in Starry stonewort coverage will
decrease fish abundance. To understand how
Starry stonewort impacts fish abundance, observations will include locations of
varying degrees of invasion (Gordon 1998) (Hedja et al. 2009). Understanding the impact that Starry
stonewort invasion may have on native fish populations can provide valuable
information that can aid in the conservation efforts within local communities.
Experimental Protocol-belt transects
The study will be conducted in nearshore locations in Lake
Erie between 3-10 meters in depth. A 10
meter transect will be placed along locations that contain aquatic vegetation. At five foot intervals along the transect, a 1
m² quadrant will be used to estimate percent coverage of Starry Stonewort. At the end of the transect, the average
percent coverage will be calculated for each location. Observations will be taken by two divers
swimming along the transect while observing opposite sides. The divers will count the number of fish
found within their field of vision as they move along the transect. These final numbers will be added together
for fish abundance along the transect.
This method will be repeated for a total of 30 locations.
A regression analysis will be used compare the relationship
of fish abundance and percent Starry stonewort coverage.