Trends in Diporeia populations across the Laurentian Great Lakes, 1997–2009

Convergence of trophic state and the lower food web in Lakes Huron, Michigan and Superior

“…For example, Diporeia densities have tended to peak at depths just below the thermocline (Nalepa et al, 2000). This species has all but disappeared from these depths in Lake Huron and Lake Michigan in recent years (Barbiero et al, 2011b), while intermediate depths still support the highest Diporeia populations in Lake Superior (Auer et al, 2009, Barbiero et al, 2011b. So while profundal abundances of this species have been converging recently in the three lakes, abundances at shallower sites have in fact diverged.…”

The ecological history of Lake Ontario according to phytoplankton

“…Under the GLNPO monitoring surveillance of the profundal zone of Lake Ontario, Barbiero et al (2011) reported that between 2004 and 2009 no Diporeia were found at sites deeper than 90 m. They observed a Diporeia decline in Lake Huron even with much lower quagga mussel abundance, implying that dreissenids may not be directly involved in Diporeia reduction and that Diporeia at many sites have disappeared despite little direct contact with mussels (Nalepa et al, 2009;Watkins et al, 2007). Edlund and Jude (2011) analyzed Diporeia gut contents and fossil remains of diatoms from southern Lake Michigan onshore and offshore sediment cores between 1987 and 2009 to resolve historical relationships among food resources, changes in Diporeia diets, and diet selectivity during the pre-and post-dreissenid invasion.…”

Measuring the effects of food availability on Lake Superior Diporeia consumption rates using radiolabeled algae

“…The 5D trials included five treatments representing a range of food availability 6-1975 mg C/m/d per Diporeia within the microcosms. Animal densities for the 1D and 5D trials were equivalent to 689 and 1337 Diporeia · m 2 , respectively, conditions comparable lakewide to the observed abundance of Diporeia in Lake Superior (Barbiero et al, 2011;Auer et al, 2013). The results from 5D trials exhibited less sample variance than those of 1D trials reflecting less impact from non-feeding individuals.…”

“…For the range of carbon fluxes observed in Great Lakes waters (57-333 mg C/m 2 /d), the food supply-consumption relationship was well described by a linear function with a slope of 0.0011 m 2 /g DW and a zero intercept. A decline in available POC flux (food supply) following invasion by dreissenid mussels has been posited as a factor contributing to the precipitous decline in Diporeia in Lake Huron, Michigan, Erie and Ontario (Barbiero et al, 2011). The food availability-consumption relationship developed here may find application in a bioenergetic model testing the food limitation hypothesis.…”