Changes in zooplankton community structure associated with the disappearance of invasive alewife in Saginaw Bay, Lake Huron

Abstract

We evaluated the response of the zooplankton community Saginaw Bay, Lake Huron to the disappearance of the planktivore alewife Alosa pseudoharengus using data collected in 1991-1996 (pre alewife decline) and 2009-2010 (post alewife decline). Bosmina longirostris, Diaptomidae, Cyclops, and Daphnia galeata contributed greatly to the separation of the two time periods with Diaptomidae and D. galeata increasing and Cyclops and B. longirostris decreasing, although B. longirostris remained the dominant species. Peak densities of zooplankton occurred in early summer (June) in the 1990s and in early fall (October) in 2009-2010. For the analysis of environmental variables on a bay-wide, annual basis, abundance of alewife, age-0 yellow perch Perca flavescens and Bythotrephes captured much of the variation in annual zooplankton community structure. Abundances of Bythotrephes and age-0 yellow perch were both higher in Some changes such as increasing proportions of calanoid copepods reflect a more oligotrophic community and are potentially indicative of resourcedriven changes rather than direct or indirect impacts of the alewife disappearance.

Lake Ontario zooplankton in 2003 and 2008: Community changes and vertical redistribution

“…MDS is insensitive to deviations from normality and has been used for Great Lakes zooplankton data by Barbiero et al (2012) and Pothoven et al (2013). The BrayCurtis similarity matrix was based on un-transformed biomass data; a square-root transformation did not decrease the stress in the ordination.…”

Thermal environment and maternal effects shape egg size in a freshwater fish

“…Annual variation in emigration rates could expose Tittabawassee River walleye to very different conditions between Saginaw Bay and the main basin of Lake Huron (Pothoven et al. ) and potentially influence egg provisioning and size.…”

Non-stationary recruitment dynamics of rainbow smelt: The influence of environmental variables and variation in size structure and length-at-maturation

“…Both rainbow smelt and alewife are planktivorous and may compete for similar resources depending on the extent of their spatial overlap (Frie and Spangler, 1985;Pothoven et al, 2009;Stewart et al, 1981;Urban and Brandt, 1993). Even in the absence of direct competition, declines in alewife populations have been shown to cause shifts in zooplankton assemblages (Pothoven et al, 2013) which could have allowed YOY rainbow smelt to maintain their growth rates even as overall lake productivity has decreased. The subsequent declines in piscivore abundance in Lake Huron may also have reduced predation pressure on adult rainbow smelt, resulting in more large individuals surviving.…”

“…More recently, lake levels have declined to record-low levels, which may be influencing habitat availability along shorelines, within tributaries, and affecting lake hydrological dynamics (Gronewold and Stow, 2013). The myriad physical, chemical, and biotic changes to Great Lakes ecosystems have resulted in benthification of energy pathways and altered zooplankton and macroinvertebrate species composition and abundance Fahnenstiel et al, 2010;Nalepa et al, 2009;Pothoven et al, 2013;Vanderploeg et al, 2012).…”