Response of freshwater microcosm communities to nutrients, fish, and elevated temperature during winter and summer

Abstract

Under conditions of stress, shallow freshwater ecosystems can undergo a state change characterized by the rapid loss of macrophytes and subsequent dominance of phytoplankton. Elevated water temperature may promote such change. Here we report the impact of two warming regimes (continuous 3ЊC above ambient and 3ЊC above ambient during summer only), with two nutrient loadings and the presence or absence of fish, on 48 microcosm ecosystems created to mimic shallow pond environments. We found that warming did not significantly encourage phytoplankton blooms, even in combination with increased nutrients and fish. Instead, macrophyte communities remained dominant. Macrophyte-associated invertebrates (gastropods and ostracods) increased in numbers in the warmed microcosms, potentially helping to stabilize the macrophyte communities. Nevertheless, warming produced trends in water chemistry that could be problematic. It increased phosphorus concentrations, total alkalinity, and conductivity. It decreased pH and oxygen saturation and increased the frequency of severe deoxygenation. These trends were largely independent of the other experimental treatments and support the suggestion that moderate warming has the potential to exacerbate existing eutrophication problems.

Effects of warming on Potamogeton crispus growth and tissue stoichiometry in the growing season

“…Previous studies also found that warming will advance the growth of aquatic plants (Haag and Gorham, 1977;Rooney and Kalff, 2000). Although some studies demonstrated that warming may increase total aquatic plant biomass (Barko and Smart, 1981;Rooney and Kalff, 2000;Feuchtmayr et al, 2009), others found no effect (Mckee et al, 2002;McKee et al, 2003) or a decreasing total plant biomass (Barko and Smart, 1981). Our results are in line with the studies that did not observe a difference in total plant biomass in response to warming.…”

Climate change and freshwater ecosystems: impacts across multiple levels of organization

“…Some of these experimental manipulations are still running several years after their inception: 24 ponds in Silkeborg (Denmark) have been warmed continuously since 2003 (Liboriussen et al 2005), another set of 20 ambient/warmed ponds at the FBA River Lab in Dorset (UK) have been running since 2006 (Yvon-Durocher et al 2010) and 48 similar-sized ponds have also been subjected to a comparable level of warming in Ness Gardens at the University of Liverpool (UK) since 1998, albeit intermittently (e.g. McKee et al 2003). The former have been used to assess shifts in community structure and ecosystem properties, both of which responded to elevated temperatures, as the ponds tended towards more turbid, planktondominated systems at higher temperatures (Meerhoff et al 2007), and the FBA set-up has revealed that warming pushes the systems towards increased heterotrophy and reduced CO 2 sequestration (Yvon-Durocher et al 2010).…”

Population dynamics and life cycle of Pisidium amnicum (Müller) (Bivalvia : Sphaeriidae) and Valvata piscinalis (Müller) (Gastropoda : Prosobranchia) in the Saône river, a nine-year study

“…However, only a few field experiments have been carried out to test the ecological consequences of climatic warming on freshwater macroinvertebrates (Hogg et al 1995, Hogg & Williams 1996, McKee et al 2003) and the latter is alone in taking gastropods into account. The results in this study show that the total density of 6 species (not including V. piscinalis) introduced in the microcosm increased significantly with a continuous 3°C above ambient and (9) Araujo et al 1997-2002Hinz (1976) et al (1997) (1981 (McKee et al 2003). In three Polish reservoirs heated by power plants, the abundance of two non-native species Physella acuta (Draparnaud) and Potamopyrgus antipodarum (Gray) increased during the period 1971-1991.…”