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The effects of zebra mussels (Dreissena polymorpha) presence on rock substrate benthic algal concentrations in inland lake systems.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Kowalski, Aubrey |
| Copyright Year | 2010 |
| Abstract | In this study, we observed rocks with different types of zebra mussel influence in a freshwater lake and lab setting to determine whether benthic algal concentrations are greater on rocks are with the presence of both live and dead zebra mussels compared to rocks without any zebra mussel influence, and whether live zebra mussels promote greater algal growth than dead shells. We set up experimental plots containing rocks with live zebra mussels, with no zebra mussels, and with dead zebra mussel shells in both the littoral zone of Douglas Lake and in a stream trough in Lakeside Lab at the University of Michigan Biological Station. After 11 days, chlorophyll a analysis was conducted to determine benthic algal concentrations. There was no significant difference between benthic algal concentrations on rocks with live or dead zebra mussels and rocks without zebra mussels in the lab, but these same values were significant in the field study. The mean amount of chlorophyll a on rocks with live or dead zebra mussels was 1.3 μg/square cm, while there were 0 μg/square cm of chlorophyll a on rocks without zebra mussels. There was no significant difference between benthic algal concentrations on rocks with live zebra mussels and rocks with dead zebra mussel shells in either the lab or field study. From the results of this study, we concluded that the presence of live or dead zebra mussel shells results in greater benthic algal growth than areas without zebra mussels. We also concluded that the presence of live zebra mussels does not promote more benthic algal growth than dead zebra mussel shells. I grant the Regents of the University of Michigan the non-exclusive right to retain, reproduce, and distribute my paper, titled in electronic formats and at no cost throughout the world. The University of Michigan may make and keep more than one copy of the Paper for purposes of security, backup, preservation and access, and may migrate the Paper to any medium or format for the purpose of preservation and access in the future. Signed, INTRODUCTION When two species interact very closely, over time strong selective pressures usually result in each species developing a response to the other, be it negative or positive. Therefore, it is very rare to find examples of interacting organisms in which one organism is affected by the interaction while the other remains completely unaffected. Interactions of this rare type are called commensalisms, and because these commensal relationships are rare, they can be very important finds in the scientific community, as any insight gained by studying known commensalisms can provide important answers about how and why organisms develop a response to each other, and also why they do not. The zebra mussel (Dreissena polymorpha), an invasive species initially brought to North America in ballast water from the Caspian Sea in the 1980s, has come to dominate freshwater ecosystems surrounding the Great Lakes due to its extremely high reproduction and filtering rates (Cecala et al. 2008). As a species invasive to the area, these mussels have been viewed as ecosystem engineers with largely negative effects on freshwater systems; as extremely efficient filter feeders, they remove an enormous amount of seston from the waters they inhabit, increasing the depth to which sunlight can penetrate, and this increase in sunlight penetration in turn leads to huge increases in benthic primary production, including benthic algal production (Cecala et al. 2008, Stewart et al. 1998). Zebra mussels have also been noted to excrete nutrients key to benthic algal production, including phosphorous and nitrogen (Ozersky et al. 2009); since phosphorous is a limiting resource in many inland lakes (Boegman et al. 2008), this zebra mussel phosphorous excretion further increases the benthic algae populations in invaded waters (Davies and Hecky 2005), which can lead to lake eutrophication (Cecala et al. 2008). Zebra mussels are also known to have negative effects on freshwater organisms in the ecosystems they inhabit; these invasive mussels out-compete native gastropod, chironomid, and caddisfly species for space on the limited amount of rocky substrate that is available (Stewart et al. 1998), reduce survival of native mussels by completely encrusting them and using them as substrate which reduces their mobility and subsequent ability to reach food (Ricciardi et al. 1998), and directly outcompete the native mussel species for food because they are much more efficient filterfeeders than are the natives (Ricciardi et al. 1998, Kurdziel 2009). Because zebra mussels are invaders, many studies have focused on the negative impacts of their introduced presence in the Great Lakes and other freshwater systems, but positive effects have been shown in many studies (Greenwood et al. 2001). A positive relationship was discovered between zebra mussels and snails (Lithasia obovata) in which the snails received nutrients from zebra mussel excretions while there was no effect observed on the zebra mussels (Greenwood et al. 2001). This is a possible example of a commensal relationship involving zebra mussels. Another study involving zebra mussels concluded that areas with zebra mussel populations had higher concentrations of organic matter than did areas without, suggesting that the invasive mussels could be benefiting some of the native species by increasing their population numbers (Stewart et al. 1998). However, this study did not conclude whether the higher concentrations of organic matter were correlated with the presence of actively filtering mussels, the presence of non-filtering dead zebra mussels shells, or both; the shells of the mussels themselves have been shown to provide a refuge for living organisms, making the true determination of the cause of increased organic matter important (Stewart et al. 1998). Furthermore, other studies have shown that areas with high densities of live zebra mussels have much higher rates of benthic algal production (Bierman et al. 2005, Davies and Hecky 2005). Altogether, these studies provide possible support for a commensal relationship existing between zebra mussels and benthic algae. The purpose of this study then was to determine whether or not a commensal relationship occurs between zebra mussels and benthic algal communities in an inland lake ecosystem. Because zebra mussel shells have been known to provide refuge for benthic organisms (Stewart et al. 1999), and because the presence of live zebra mussels has been associated with higher algal productivity (Bierman et al. 2005, Davies and Hecky 2005), we predict that areas containing rocks covered with live or dead zebra mussels will have higher benthic algal concentrations than areas which lack zebra mussels. Also, because phosphorous is a known limiting-resource in many inland lakes (Boegman et al. 2008) and live zebra mussel excretions contain substantial concentrations of phosphorous (Ozersky et al. 2009), we predict that benthic algal concentrations will be highest in areas that contain live zebra mussels. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://deepblue.lib.umich.edu/bitstream/handle/2027.42/78464/Kowalski_Aubrey_2010.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
