Phytoplankton Communities in Green Bay, Lake Michigan after Invasion by Dreissenid Mussels: Increased Dominance by Cyanobacteria

Abstract

Biological invasions of aquatic systems disrupt ecological communities, and cause major changes in diversity and ecosystem function. The Laurentian Great Lakes of North America have been dramatically altered by such invasions, especially zebra (Dreissena polymorpha) and quagga (D. rostriformis bugensis) mussels. Responses to mussel invasions have included increased water clarity, and decreased chlorophyll and phytoplankton abundance. Although not all systems have responded similarly, in general, mussels have changed nutrient dynamics and physical habitat conditions. Therefore examination of different impacts can help us further understand mechanisms that underlie ecosystem responses to biological invasions. To aid our understanding of ecosystem impacts, we sampled established locations along a well-studied trophic gradient in Green Bay, Lake Michigan, after the 1993 zebra mussel invasion. A strong trophic gradient remained during the period sampled after the mussel invasion (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012). However, mean summer chlorophyll increased and other measures of phytoplankton biomass (microscope and electronic cell counting) did not change significantly. Multivariate analyses of phytoplankton community structure demonstrate a significant community shift after the invasion. Cyanobacteria increased in dominance, with 682Microcystis becoming the major summer taxon in lower Green Bay. Diatom diversity and abundance also increased and Chlorophyta became rare. Phytoplankton responses along the trophic gradient of Green Bay to zebra mussel invasion highlight the importance of mussel effects on nutrient dynamics and phytoplankton diversity and function.

Lake Michigan's suitability for bigheaded carp: The importance of diet flexibility and subsurface habitat

“…Biophysical outputs reflected the spatial and temporal patterns of temperature and prey in Green Bay and Muskegon. FVCOM‐GEM simulated higher prey concentrations in Green Bay in comparison to the main lake as well as the characteristic trophic gradient within the lower bay that stems from the mouth of the Fox River (De Stasio et al., ) (Figures S3.2–S3.4). The distribution of simulated prey concentrations at Muskegon reflected the nearshore–offshore gradient and plankton phenology with high prey concentrations in May and June in the nearshore and the formation of the deep chlorophyll maxima (DCM) in the offshore during late stratification (Figure ; Table ).…”

“…This is relevant considering that >50% of Lake Michigan chlorophyll is comprised of pico‐ (<2 μm) and nanoplankton (2–20 μm) communities (Carrick et al., ; Cuhel & Aguilar, ), which historically have included more single‐celled organisms than the colonial organisms (Fahnenstiel & Carrick, ) that would be more susceptible to BHC filtration. An exception to this might be in eutrophic areas like Green Bay (see De Stasio et al., ) where the size‐selective grazing pressure of dreissenid mussels has promoted the dominance of colonial species (e.g. Microcystis ) that are not effectively filtered by dreissenids but could be easily consumed by BHC.…”

“…Observed chlorophyll‐a and zooplankton data came from De Stasio et al. () and Reed () for Green Bay. S. Pothoven (unpublished data) at National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL), and Pothoven and Fahnenstiel () provided data for Muskegon.…”

“…The filtering activity of the invasive dreissenid mussels has contributed to major changes in Lake Michigan's lower trophic levels (Fahnenstiel, Nalepa, Pothoven, Carrick, & Scavia, ). Some of the strongest effects include the disappearance of the spring phytoplankton bloom (Vanderploeg et al., ), the redirection of nutrients and the flow of energy to the nearshore (Hecky et al., ), and changes in size structure and species composition in zooplankton and phytoplankton communities (De Stasio, Schrimpf, & Cornwell, ; Vanderploeg et al., ). The dreissenid invasion also has altered energy dynamics in alewives ( Alosa pseudoharengus ) and contributed to the declining biomass of planktivorous prey fishes in Lake Michigan (Madenjian, Pothoven, Dettmers, & Holuszko, ; Madenjian et al., ).…”

Feeding, survival, and reproduction of two populations of Eurytemora (Copepoda) exposed to local toxic cyanobacteria

“…In Green Bay the dominant cyanobacteria species is now Microcystis aeruginosa, which can grow either as solitary cells or colonies. It is now common in many Great Lakes regions, producing microcystin, a hepatotoxin closely related to nodularin (Mur et al, 1999;De Stasio et al, 2014). Comparing the responses of Eurytemora to these local cyanobacteria and their toxins can help determine potential changes in food web interactions in the face of increasing eutrophication.…”