Henry A Vanderploeg - Academia.edu (original) (raw)
Papers by Henry A Vanderploeg
We determined the clearance rates of the profunda morph of the quagga mussel (Dreissena bugensis)... more We determined the clearance rates of the profunda morph of the quagga mussel (Dreissena bugensis) using seston and Cryptomonas ozolini, a high-quality algal food, for the temperature range 1–7 °C,which is the full temperature range this morph is likely to experience during isothermal conditions or in the hypolimnion of deep lakes. Experiments at 3 °C with the shallow-water morph of the quagga and the zebra mussel provided very similar results. The clearance rates were combined with dreissenid abundance in 0–30 m, 30–50 m, 50–90 m, and \u3e90m depth zones of the southern basin of Lake Michigan to calculate a maximum (using Cryptomonas) and minimum (using seston) fraction of the water column cleared (FC) per day in the different depth zones at 3 °C to determine dreissenid impact on the spring phytoplankton bloom from 1994 to 2008. Starting in 2003 or 2004 with the replacement of zebra mussels by quagga mussels in shallow water and expansion of quagga mussel biomass in deep water, FC b...
Freshwater Biology
Changes in seasonal cycles (i.e., phenology), can cause mismatches throughout aquatic food webs a... more Changes in seasonal cycles (i.e., phenology), can cause mismatches throughout aquatic food webs and often are used as the primary indicator of zooplankton response to environmental changes. However, zooplankton phenology has been largely overlooked in Lake Michigan despite the altered phenology of phytoplankton, including the disappearance of the offshore spring phytoplankton bloom following Dreissena mussel invasions. Multiple measures of phenology were evaluated for the major zooplankton groups in offshore southeastern Lake Michigan both before the loss of the spring bloom (1983–2003), and after the spring bloom had disappeared (2007–2019). Water temperatures in spring did not differ between time periods. Standardised biomass declined between time periods for all zooplankton groups in spring and for total zooplankton and the cladoceran Daphnia in the summer. Changes in zooplankton phenology varied across groups and depended on the phenological measures used. Month of peak biomass ...
Environmental Biology of Fishes, 2017
In the original article lacks one institution of Daisuke Goto and incorrectly list the institutio... more In the original article lacks one institution of Daisuke Goto and incorrectly list the institution of Tomas O. Höök.
Determining the degree to which predation affects prey abundance in natural communities constitut... more Determining the degree to which predation affects prey abundance in natural communities constitutes a key goal of ecological research. Predators can affect prey through both consumptive effects (CEs) and nonconsumptive effects (NCEs), although the contributions of each mechanism to the density of prey populations remain largely hypothetical in most systems. 28 Common statistical methods applied to time series data cannot elucidate the mechanisms 29 responsible for hypothesized predator effects on prey density (e.g., differentiate CEs from 30 NCEs), nor provide parameters for predictive models. State space models (SSMs) applied to time 31 series data offer a way to meet these goals. Here, we employ SSMs to assess effects of an 32 invasive predatory zooplankter, Bythotrephes longimanus, on an important prey species, 33 Daphnia mendotae, in Lake Michigan. We fit mechanistic models in a SSM framework to 34 seasonal time series (1994-2012) using a recently developed, maximum likelihood-based 35 optimization method, iterated filtering, which can overcome challenges in ecological data (e.g. nonlinearities, measurement error, and irregular sampling intervals). Our results indicate that B. longimanus strongly influences D. mendotae dynamics, with mean annual peak densities of B. longimanus observed in Lake Michigan estimated to cause a 61% reduction in D. mendotae population growth rate and a 59% reduction in peak biomass density. Further, the observed B. longimanus effect is most consistent with an NCE via reduced birth rates. The SSM approach also provided estimates for key biological parameters (e.g., demographic rates) and the contribution of dynamic stochasticity and measurement error. Our study therefore provides evidence derived directly from survey data that the invasive zooplankter B. longimanus is affecting zooplankton demographics and offer parameter estimates needed to inform predictive models that explore the effect of B. longimanus under different scenarios such as climate change.
The concept of effective food concentration (EFC). a means of predicting food c( sumption from se... more The concept of effective food concentration (EFC). a means of predicting food c( sumption from selel.:livity and food con~ntratjon data. is explained. tested. and applied 10 und standing food consumption by the freshwater copepod Diaptomus sicilis on mixtures of algae different sizes and on Lake Michigan seston. Experiments on mixtures of different sized Chlomy£ monos spp. showed that selection (W ' ) was an invariant function of particle size when the algae WI counted microscopically. When the Coulter counter was used. a more variable pattern of selectivity similar to the peak tracking response reponed by some invest igators was obtained. This was due bias of zooplankton-produced particles. Size-selective selectivity coefficients (W') were u.~ed to wei@ Ihe food concentration in ea..:h size category and the weighted values summed 10 give EFC. Food cc ~umption in experiments with seston and with cultured algae was beller described by EFC than lotal food concenlration (TFC). ...
Journal of Great Lakes Research, 2020
Data on Secchi depth, chlorophyll a, total phosphorus (TP), and nutrient status of phytoplankton ... more Data on Secchi depth, chlorophyll a, total phosphorus (TP), and nutrient status of phytoplankton were collected at five nearshore sites (11-17 m deep) and two offshore sites (>100 m) between the Grand River and Muskegon River outflows during March-December 2014-2018 to describe seasonal patterns and to compare the two depth regions in southeastern Lake Michigan. In contrast to the offshore, where spring chlorophyll a and TP concentrations declined dramatically following the dreissenid mussel expansion, the nearshore region of southeastern Lake Michigan was still characterized by low Secchi depth and elevated chlorophyll a and TP in the spring. During May, median Secchi depth was 5 times higher in the offshore than the nearshore, whereas chlorophyll a and TP were over 9 and 3 times higher in the nearshore, respectively. Even though spring chlorophyll a and TP have declined substantially at some of the nearshore sites compared to 1996, particularly the sites closest to tributary outflows, the overall yield of chlorophyll a per unit TP did not change over time in the nearshore. There were indications of Pdeficiency in the nearshore in 2014-2018, but P-deficiency was even more severe in the offshore during the spring where yield of chlorophyll a per unit TP was also lower than in the nearshore. Although dreissenid mussels can be abundant in the nearshore, their populations are patchy and inputs from tributaries provide conditions that apparently dampen any potential filtering impacts of mussels in the nearshore compared to the offshore, especially during the spring.
SIL Proceedings, 1922-2010, 1993
Limnology and Oceanography, 2017
We applied a three-dimensional biophysical model to Lake Michigan for the years 2000, 2005, and 2... more We applied a three-dimensional biophysical model to Lake Michigan for the years 2000, 2005, and 2010 to consider the mechanisms controlling spatial and temporal patterns of phytoplankton abundance (chlorophyll a) and lake-wide productivity. Model skill was assessed by comparison to satellite-derived Chl a and field-measured water quality variables. We evaluated model sensitivity to scenarios of varying mussel filter feeding intensity, tributary phosphorus loads, and warm vs. cool winter-spring climate scenarios. During the winter-spring phytoplankton bloom, spatial patterns of Chl a were controlled by variables that influenced surface mixed layer depth: deep mixing reduced net phytoplankton growth through light limitation and by exposing the full water column to mussel filter feeding. Onset of summer and winter stratification promoted higher surface Chl a initially by increasing mean light exposure and by separating the euphotic zone from mussels. During the summer stratified period, areas of relatively high Chl a were associated with coastal plumes influenced by tributary-derived nutrients and coastal upwelling-downwelling. While mussels influenced spatial and temporal distribution of Chl a, lake-wide, annual mean primary production was more sensitive to phosphorus and warm/cool meteorology scenarios than to mussel filter feeding scenarios. Although Chl a and primary production declined over the quagga mussel invasion, our results suggest that increased nutrient loads would increase lake-wide productivity even in the presence of mussels; however, altered spatial and temporal patterns of productivity caused by mussel filter feeding would likely persist.
Ocean Dynamics, 2017
There were two phytoplankton blooms captured by remote sensing in Lake Michigan in 1998, one from... more There were two phytoplankton blooms captured by remote sensing in Lake Michigan in 1998, one from March to May, and one during June. In this paper, those phytoplankton blooms were simulated by a coupled physical-biological model, driven by observed meteorological forcing in 1998. The model reasonably reproduced the lake currents. The biological model results, with and without riverine nutrient loading, were compared with the remote sensing data. A 3-monthlong donut-like phytoplankton bloom that appeared in southern Lake Michigan was reasonably well simulated only when riverine input was included, indicating the importance of riverine nutrient input for supporting the growth of phytoplankton in Lake Michigan. The model with riverine input also captured a second event-driven phytoplankton bloom during June with weaker magnitude that occurred in mid-south Lake Michigan, which lasted for about 20 days. The major reason for the weaker bloom in June was that vertical mixing in the hydrodynamic model was too weak (leading to a mixed-layer depth of 20 m) to bring the bottom nutrient-rich water up to the epilimnion. High chlorophyll concentration that persisted in Green Bay for almost a year was simulated with less intensity. Keywords Phytoplankton bloom. Coupled physical-biological model. Lake Michigan. Great Lakes This article is part of the Topical Collection on the 8th International Workshop on Modeling the Ocean (IWMO),
Journal of Great Lakes Research, 2015
Offshore-onshore spatial distribution and abundance of Cercopagis pengoi, a small non-indigenous ... more Offshore-onshore spatial distribution and abundance of Cercopagis pengoi, a small non-indigenous predatory cercopagid, in Lake Michigan have been hypothesized to be regulated by the larger non-indigenous predatory cercopagid, Bythotrephes longimanus, through predation and/or competition. However, temperature and prey abundance are other factors that could be affecting Cercopagis. First, we examined all these factors on Cercopagis population abundance, life history traits and spatio-temporal distribution. In addition, we examined vertical spatial overlap between these species and determined predation rate of Bythotrephes on Cercopagis. Linear mixed effects analysis of spatial-temporal data showed that biomass of B. longimanus had the strongest effect, which was significantly negative on biomass, proportion of fecund females and mean clutch size of Cercopagis. Fecundity increased significantly with density of potential prey zooplankton, whereas Cercopagis total biomass increased significantly with the mean epilimnion temperature. Cercopagis and Bythotrephes overlapped vertically in the epi-and metalimnion, and neither of them showed any appreciable diel vertical migration. In predation experiments, Bythotrephes consumed Cercopagis at the same rate as Daphnia mendotae, a known preferred prey, when offered at equal concentrations. Overall, this observation, together with vertical overlap of Cercopagis with Bythotrephes implies that Bythotrephes predation has a strong influence on Cercopagis distribution; however, prey availability, temperature, and competition may be important secondary factors. These results imply that invasion success of Cercopagis may be limited by prior invasion by Bythotrephes.
Journal of Great Lakes Research, 2015
A plankton survey system, fisheries acoustics, and opening/closing nets were used to define fine-... more A plankton survey system, fisheries acoustics, and opening/closing nets were used to define fine-scale diel vertical spatial interactions among non-indigenous alewives and visually preying cercopagids (Bythotrephes longimanus and Cercopagis pengoi) and indigenous zooplankton in nearshore and offshore Lake Michigan during August 2004. Because of increased water clarity associated with dreissenid mussel expansion and radically different thermal structure between cruises, we were able to observe the effects of thermal structure on diel vertical migration under high light conditions favorable especially to visual predation by cercopagids. Vertical position and overlap between alewives, Bythotrephes, and Daphnia mendotae at a 60-m site were strongly driven by thermal structure. Daphnia showed the strongest diel vertical migration of zooplankton that included migration between the epilimnion at night and the metalimnion-hypolimnion boundary during the day, whereas its major predator, Bythotrephes, was confined at all times to the epilimnion-metalimnion. Some alewives migrated from the hypolimnion to the metalimnion and epilimnion at night. As a result, most spatial overlap of Daphnia, Bythotrephes, and alewives occurred at night. Simple bioenergetics models were used to contrast predatory interactions between alewives and cercopagids at nearshore and offshore sites. Bythotrephes was the preferred prey of alewives, and at the 10-m site, alewives were the major controller of zooplankton because of its elimination of Bythotrephes. In contrast, Bythotrephes offshore likely escaped predation because of low spatial overlap with a low concentration of alewives and was the major predator and shaper of zooplankton community structure.
Freshwater Biology, 2015
The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriform... more The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) on aquatic ecosystems, including Lake Michigan, are a topic of current interest to scientists and resource managers. We hypothesised that the winter-spring phytoplankton bloom in Lake Michigan is reduced at locations where the fraction of the water column cleared per day by Dreissena filter feeding approached the net growth rate of phytoplankton, when the water column was not stratified. To test this hypothesis, we compared the spatial distribution of Dreissena filter-feeding intensity (determined from geostatistical modelling) to the spatial distribution of chlorophyll (determined from satellite remote sensing). 2. To map the spatial distribution of Dreissena biomass and filter-feeding intensity, we developed a geostatistical model based on point observations of mussel biomass measured in Lake Michigan in 1994/1995, 2000, 2005 and 2010. The model provided fine-scale estimates of the spatial distribution of biomass for the survey years and provided estimates, with their uncertainty, of total biomass lakewide and within subregions. The approach outlined could be applied more generally to map the distribution of benthic biota in lakes from point observations. 3. Total biomass of Dreissena in Lake Michigan, estimated from the geostatistical model, increased significantly over each five-year period. The total biomass in units of 10 6 kg ash-free dry mass (AFDM) (with 90% confidence interval)
Reductions in nutrient loads and impacts from invasive species may lower recruitment potential of... more Reductions in nutrient loads and impacts from invasive species may lower recruitment potential of Great Lakes fishes. Filtration by invasive quagga mussels has reduced phytoplankton biomass, shifted energy flow from pelagic to benthic pathways, and restricted phosphorus transport from nearshore to offshore. Biomass of large cladocerans and adult planktivorous fishes has declined from impacts of quagga mussels and the predaceous cladoceran, Bythotrephes. These multiple stressors have altered zooplankton distributions and densities, and may lower larval fish growth and survival. Yet, in Lakes Michigan and Huron, some fish species still grow and recruit well in nearshore and offshore areas. To understand what drives fish recruitment, we sampled nutrients, fish larvae, and lower and upper food webs on nearshore-offshore transects from 2010-2013 in Lakes Huron and Michigan. A compensatory shift from large phytoplankton to the microbial food web—utilizable by both copepods and small clado...
Journal of Plankton Research, 1984
Journal of Great Lakes Research, 2010
The colonization of the zebra mussel (Dreissena polymorpha) in Saginaw Bay dramatically altered t... more The colonization of the zebra mussel (Dreissena polymorpha) in Saginaw Bay dramatically altered the phytoplankton community composition resulting in exclusion of light sensitive species and dominance of species with oligotrophic preferences and light resistance. In 1990, the NOAA Great Lakes Environmental Research Laboratory initiated a 7-year survey program to monitor changes in the lower food web of Saginaw Bay, where zebra mussels became established in the fall of 1991. To investigate shifts in the phytoplankton community composition over the 7-year period from 1990 to 1996 we searched for clusters of similar composition using multivariate principal component analysis (PCA) on proportions of 22 taxonomic groupings of the total phytoplankton density (cells per milliliter). We then used an agglomerative hierarchical clustering analysis of the PCA scores. We identified five characteristic phytoplankton communities in configurations that allowed recognizing four distinct periods in Saginaw Bay linked to the zebra mussel invasion. Significant changes were indicative of increased water clarity and eutrophic conditions being replaced by more oligotrophic conditions as clusters dominated by light sensitive species, such as the cyanobacteria Oscillatoria redekii, became immediately rare and clusters dominated by diatoms such as Cyclotella spp. became common. Microcystis spp., a light tolerant cyanobacteria not grazed by zebra mussel, dominated assemblages after 1994. The shifts in phytoplankton composition confirm that zebra mussels effects on phytoplankton communities are mediated by both direct (filtration) and indirect (nutrient cycling) mechanisms and also suggests that increased light penetration is an important mechanism behind some changes.
Journal of Great Lakes Research, 2003
The population characteristics of Bythotrephes were evaluated at seven nearshore (45 m) and eight... more The population characteristics of Bythotrephes were evaluated at seven nearshore (45 m) and eight offshore (80 to 150 m) stations in Lake Michigan during July and September 2000. Bythotrephes was generally most abundant at offshore stations, but mean density was patchy (4 to 1,326/m 2) among locations. During the year, there was a shift from reproduction by mainly instar III females to reproduction by instar II females. The shift generally reflected a change in the population structure of Bythotrephes at most sites during the same period. Bythotrephes populations in July were generally characterized by small body size at reproduction (instar II and III), large clutch size, and small neonates. Later in the season, body size at reproduction and neonates were larger and clutch size was smaller. Most growth (body length) of Bythotrephes occurred between instar I and II whereas little growth occurred between instar II and III. Spine length of Bythotrephes increased between July and September. The population characteristics and reproductive strategies of Bythotrephes appear to be adaptations to fish predation and food limitations.
Journal of Great Lakes Research, 2009
Colonization of the Laurentian Great Lakes by the invasive mussel Dreissena polymorpha was a sign... more Colonization of the Laurentian Great Lakes by the invasive mussel Dreissena polymorpha was a significant ecological disturbance. The invasion reached Saginaw Bay, Lake Huron, in 1991 and initially cleared the waters and lowered algal biomass. However, an unexpected result occurred 3 years after the initial invasion with the return of nuisance summer blooms of cyanobacteria, a problem that had been successfully addressed with the implementation of phosphorus controls in the late 1970s. A multi-class phytoplankton model was developed and tested against field observations and then used to explore the causes of these temporal changes. Model scenarios suggest that changes in the phytoplankton community can be linked to three zebra mussel-mediated effects: (1) removal of particles resulting in clearer water, (2) increased recycle of available phosphorus throughout the summer, and (3) selective rejection of certain Microcystis strains. Light inhibition of certain phytoplankton assemblages and the subsequent alteration of competitive dynamics is a novel result of this model. These results enhance our understanding of the significant role of zebra mussels in altering lower trophic level dynamics of Saginaw Bay and suggest that their physical reengineering of the aquatic environment was the major force driving changes in the phytoplankton community composition.
Journal of Great Lakes Research, 2010
During the spring isothermal mixing period, surface-mixed layer (SML) chlorophyll a and phytoplan... more During the spring isothermal mixing period, surface-mixed layer (SML) chlorophyll a and phytoplankton biomass (carbon) and water column primary productivity decreased substantially in 2007-2008 as compared to 1995-1998 (66%, 87%, and 70% decrease, respectively). Smaller or no decreases were noted between 1983-1987 and 1995-1998 (chlorophyll a 23% decrease, phytoplankton biomass 5% increase, and production 22% decrease). Phytoplankton composition also changed during the spring isothermal mixing period in 2007-2008 as compared to 1983-1987 and 1995-1998; all phytoplankton groups with the exception of cyanobacteria and chlorophytes exhibited dramatic reductions in 2007-2008. The pronounced changes in phytoplankton properties during spring mixing in 2007-2008 were attributed to the filtering activities of the quagga mussel (Dreissena rostriformis bugensis). During mid-and late thermal stratification periods, SML phytoplankton chlorophyll a and phytoplankton carbon and water column primary production exhibited only one significant change across all decades (midstratification production in 2007-2008 as compared to 1995-1998 and 1983-1987). Phytoplankton compositional changes in the SML also were limited during thermal stratification. The size of the deep chlorophyll layer (DCL) in
Journal of Geophysical Research, 2006
We determined the clearance rates of the profunda morph of the quagga mussel (Dreissena bugensis)... more We determined the clearance rates of the profunda morph of the quagga mussel (Dreissena bugensis) using seston and Cryptomonas ozolini, a high-quality algal food, for the temperature range 1–7 °C,which is the full temperature range this morph is likely to experience during isothermal conditions or in the hypolimnion of deep lakes. Experiments at 3 °C with the shallow-water morph of the quagga and the zebra mussel provided very similar results. The clearance rates were combined with dreissenid abundance in 0–30 m, 30–50 m, 50–90 m, and \u3e90m depth zones of the southern basin of Lake Michigan to calculate a maximum (using Cryptomonas) and minimum (using seston) fraction of the water column cleared (FC) per day in the different depth zones at 3 °C to determine dreissenid impact on the spring phytoplankton bloom from 1994 to 2008. Starting in 2003 or 2004 with the replacement of zebra mussels by quagga mussels in shallow water and expansion of quagga mussel biomass in deep water, FC b...
Freshwater Biology
Changes in seasonal cycles (i.e., phenology), can cause mismatches throughout aquatic food webs a... more Changes in seasonal cycles (i.e., phenology), can cause mismatches throughout aquatic food webs and often are used as the primary indicator of zooplankton response to environmental changes. However, zooplankton phenology has been largely overlooked in Lake Michigan despite the altered phenology of phytoplankton, including the disappearance of the offshore spring phytoplankton bloom following Dreissena mussel invasions. Multiple measures of phenology were evaluated for the major zooplankton groups in offshore southeastern Lake Michigan both before the loss of the spring bloom (1983–2003), and after the spring bloom had disappeared (2007–2019). Water temperatures in spring did not differ between time periods. Standardised biomass declined between time periods for all zooplankton groups in spring and for total zooplankton and the cladoceran Daphnia in the summer. Changes in zooplankton phenology varied across groups and depended on the phenological measures used. Month of peak biomass ...
Environmental Biology of Fishes, 2017
In the original article lacks one institution of Daisuke Goto and incorrectly list the institutio... more In the original article lacks one institution of Daisuke Goto and incorrectly list the institution of Tomas O. Höök.
Determining the degree to which predation affects prey abundance in natural communities constitut... more Determining the degree to which predation affects prey abundance in natural communities constitutes a key goal of ecological research. Predators can affect prey through both consumptive effects (CEs) and nonconsumptive effects (NCEs), although the contributions of each mechanism to the density of prey populations remain largely hypothetical in most systems. 28 Common statistical methods applied to time series data cannot elucidate the mechanisms 29 responsible for hypothesized predator effects on prey density (e.g., differentiate CEs from 30 NCEs), nor provide parameters for predictive models. State space models (SSMs) applied to time 31 series data offer a way to meet these goals. Here, we employ SSMs to assess effects of an 32 invasive predatory zooplankter, Bythotrephes longimanus, on an important prey species, 33 Daphnia mendotae, in Lake Michigan. We fit mechanistic models in a SSM framework to 34 seasonal time series (1994-2012) using a recently developed, maximum likelihood-based 35 optimization method, iterated filtering, which can overcome challenges in ecological data (e.g. nonlinearities, measurement error, and irregular sampling intervals). Our results indicate that B. longimanus strongly influences D. mendotae dynamics, with mean annual peak densities of B. longimanus observed in Lake Michigan estimated to cause a 61% reduction in D. mendotae population growth rate and a 59% reduction in peak biomass density. Further, the observed B. longimanus effect is most consistent with an NCE via reduced birth rates. The SSM approach also provided estimates for key biological parameters (e.g., demographic rates) and the contribution of dynamic stochasticity and measurement error. Our study therefore provides evidence derived directly from survey data that the invasive zooplankter B. longimanus is affecting zooplankton demographics and offer parameter estimates needed to inform predictive models that explore the effect of B. longimanus under different scenarios such as climate change.
The concept of effective food concentration (EFC). a means of predicting food c( sumption from se... more The concept of effective food concentration (EFC). a means of predicting food c( sumption from selel.:livity and food con~ntratjon data. is explained. tested. and applied 10 und standing food consumption by the freshwater copepod Diaptomus sicilis on mixtures of algae different sizes and on Lake Michigan seston. Experiments on mixtures of different sized Chlomy£ monos spp. showed that selection (W ' ) was an invariant function of particle size when the algae WI counted microscopically. When the Coulter counter was used. a more variable pattern of selectivity similar to the peak tracking response reponed by some invest igators was obtained. This was due bias of zooplankton-produced particles. Size-selective selectivity coefficients (W') were u.~ed to wei@ Ihe food concentration in ea..:h size category and the weighted values summed 10 give EFC. Food cc ~umption in experiments with seston and with cultured algae was beller described by EFC than lotal food concenlration (TFC). ...
Journal of Great Lakes Research, 2020
Data on Secchi depth, chlorophyll a, total phosphorus (TP), and nutrient status of phytoplankton ... more Data on Secchi depth, chlorophyll a, total phosphorus (TP), and nutrient status of phytoplankton were collected at five nearshore sites (11-17 m deep) and two offshore sites (>100 m) between the Grand River and Muskegon River outflows during March-December 2014-2018 to describe seasonal patterns and to compare the two depth regions in southeastern Lake Michigan. In contrast to the offshore, where spring chlorophyll a and TP concentrations declined dramatically following the dreissenid mussel expansion, the nearshore region of southeastern Lake Michigan was still characterized by low Secchi depth and elevated chlorophyll a and TP in the spring. During May, median Secchi depth was 5 times higher in the offshore than the nearshore, whereas chlorophyll a and TP were over 9 and 3 times higher in the nearshore, respectively. Even though spring chlorophyll a and TP have declined substantially at some of the nearshore sites compared to 1996, particularly the sites closest to tributary outflows, the overall yield of chlorophyll a per unit TP did not change over time in the nearshore. There were indications of Pdeficiency in the nearshore in 2014-2018, but P-deficiency was even more severe in the offshore during the spring where yield of chlorophyll a per unit TP was also lower than in the nearshore. Although dreissenid mussels can be abundant in the nearshore, their populations are patchy and inputs from tributaries provide conditions that apparently dampen any potential filtering impacts of mussels in the nearshore compared to the offshore, especially during the spring.
SIL Proceedings, 1922-2010, 1993
Limnology and Oceanography, 2017
We applied a three-dimensional biophysical model to Lake Michigan for the years 2000, 2005, and 2... more We applied a three-dimensional biophysical model to Lake Michigan for the years 2000, 2005, and 2010 to consider the mechanisms controlling spatial and temporal patterns of phytoplankton abundance (chlorophyll a) and lake-wide productivity. Model skill was assessed by comparison to satellite-derived Chl a and field-measured water quality variables. We evaluated model sensitivity to scenarios of varying mussel filter feeding intensity, tributary phosphorus loads, and warm vs. cool winter-spring climate scenarios. During the winter-spring phytoplankton bloom, spatial patterns of Chl a were controlled by variables that influenced surface mixed layer depth: deep mixing reduced net phytoplankton growth through light limitation and by exposing the full water column to mussel filter feeding. Onset of summer and winter stratification promoted higher surface Chl a initially by increasing mean light exposure and by separating the euphotic zone from mussels. During the summer stratified period, areas of relatively high Chl a were associated with coastal plumes influenced by tributary-derived nutrients and coastal upwelling-downwelling. While mussels influenced spatial and temporal distribution of Chl a, lake-wide, annual mean primary production was more sensitive to phosphorus and warm/cool meteorology scenarios than to mussel filter feeding scenarios. Although Chl a and primary production declined over the quagga mussel invasion, our results suggest that increased nutrient loads would increase lake-wide productivity even in the presence of mussels; however, altered spatial and temporal patterns of productivity caused by mussel filter feeding would likely persist.
Ocean Dynamics, 2017
There were two phytoplankton blooms captured by remote sensing in Lake Michigan in 1998, one from... more There were two phytoplankton blooms captured by remote sensing in Lake Michigan in 1998, one from March to May, and one during June. In this paper, those phytoplankton blooms were simulated by a coupled physical-biological model, driven by observed meteorological forcing in 1998. The model reasonably reproduced the lake currents. The biological model results, with and without riverine nutrient loading, were compared with the remote sensing data. A 3-monthlong donut-like phytoplankton bloom that appeared in southern Lake Michigan was reasonably well simulated only when riverine input was included, indicating the importance of riverine nutrient input for supporting the growth of phytoplankton in Lake Michigan. The model with riverine input also captured a second event-driven phytoplankton bloom during June with weaker magnitude that occurred in mid-south Lake Michigan, which lasted for about 20 days. The major reason for the weaker bloom in June was that vertical mixing in the hydrodynamic model was too weak (leading to a mixed-layer depth of 20 m) to bring the bottom nutrient-rich water up to the epilimnion. High chlorophyll concentration that persisted in Green Bay for almost a year was simulated with less intensity. Keywords Phytoplankton bloom. Coupled physical-biological model. Lake Michigan. Great Lakes This article is part of the Topical Collection on the 8th International Workshop on Modeling the Ocean (IWMO),
Journal of Great Lakes Research, 2015
Offshore-onshore spatial distribution and abundance of Cercopagis pengoi, a small non-indigenous ... more Offshore-onshore spatial distribution and abundance of Cercopagis pengoi, a small non-indigenous predatory cercopagid, in Lake Michigan have been hypothesized to be regulated by the larger non-indigenous predatory cercopagid, Bythotrephes longimanus, through predation and/or competition. However, temperature and prey abundance are other factors that could be affecting Cercopagis. First, we examined all these factors on Cercopagis population abundance, life history traits and spatio-temporal distribution. In addition, we examined vertical spatial overlap between these species and determined predation rate of Bythotrephes on Cercopagis. Linear mixed effects analysis of spatial-temporal data showed that biomass of B. longimanus had the strongest effect, which was significantly negative on biomass, proportion of fecund females and mean clutch size of Cercopagis. Fecundity increased significantly with density of potential prey zooplankton, whereas Cercopagis total biomass increased significantly with the mean epilimnion temperature. Cercopagis and Bythotrephes overlapped vertically in the epi-and metalimnion, and neither of them showed any appreciable diel vertical migration. In predation experiments, Bythotrephes consumed Cercopagis at the same rate as Daphnia mendotae, a known preferred prey, when offered at equal concentrations. Overall, this observation, together with vertical overlap of Cercopagis with Bythotrephes implies that Bythotrephes predation has a strong influence on Cercopagis distribution; however, prey availability, temperature, and competition may be important secondary factors. These results imply that invasion success of Cercopagis may be limited by prior invasion by Bythotrephes.
Journal of Great Lakes Research, 2015
A plankton survey system, fisheries acoustics, and opening/closing nets were used to define fine-... more A plankton survey system, fisheries acoustics, and opening/closing nets were used to define fine-scale diel vertical spatial interactions among non-indigenous alewives and visually preying cercopagids (Bythotrephes longimanus and Cercopagis pengoi) and indigenous zooplankton in nearshore and offshore Lake Michigan during August 2004. Because of increased water clarity associated with dreissenid mussel expansion and radically different thermal structure between cruises, we were able to observe the effects of thermal structure on diel vertical migration under high light conditions favorable especially to visual predation by cercopagids. Vertical position and overlap between alewives, Bythotrephes, and Daphnia mendotae at a 60-m site were strongly driven by thermal structure. Daphnia showed the strongest diel vertical migration of zooplankton that included migration between the epilimnion at night and the metalimnion-hypolimnion boundary during the day, whereas its major predator, Bythotrephes, was confined at all times to the epilimnion-metalimnion. Some alewives migrated from the hypolimnion to the metalimnion and epilimnion at night. As a result, most spatial overlap of Daphnia, Bythotrephes, and alewives occurred at night. Simple bioenergetics models were used to contrast predatory interactions between alewives and cercopagids at nearshore and offshore sites. Bythotrephes was the preferred prey of alewives, and at the 10-m site, alewives were the major controller of zooplankton because of its elimination of Bythotrephes. In contrast, Bythotrephes offshore likely escaped predation because of low spatial overlap with a low concentration of alewives and was the major predator and shaper of zooplankton community structure.
Freshwater Biology, 2015
The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriform... more The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) on aquatic ecosystems, including Lake Michigan, are a topic of current interest to scientists and resource managers. We hypothesised that the winter-spring phytoplankton bloom in Lake Michigan is reduced at locations where the fraction of the water column cleared per day by Dreissena filter feeding approached the net growth rate of phytoplankton, when the water column was not stratified. To test this hypothesis, we compared the spatial distribution of Dreissena filter-feeding intensity (determined from geostatistical modelling) to the spatial distribution of chlorophyll (determined from satellite remote sensing). 2. To map the spatial distribution of Dreissena biomass and filter-feeding intensity, we developed a geostatistical model based on point observations of mussel biomass measured in Lake Michigan in 1994/1995, 2000, 2005 and 2010. The model provided fine-scale estimates of the spatial distribution of biomass for the survey years and provided estimates, with their uncertainty, of total biomass lakewide and within subregions. The approach outlined could be applied more generally to map the distribution of benthic biota in lakes from point observations. 3. Total biomass of Dreissena in Lake Michigan, estimated from the geostatistical model, increased significantly over each five-year period. The total biomass in units of 10 6 kg ash-free dry mass (AFDM) (with 90% confidence interval)
Reductions in nutrient loads and impacts from invasive species may lower recruitment potential of... more Reductions in nutrient loads and impacts from invasive species may lower recruitment potential of Great Lakes fishes. Filtration by invasive quagga mussels has reduced phytoplankton biomass, shifted energy flow from pelagic to benthic pathways, and restricted phosphorus transport from nearshore to offshore. Biomass of large cladocerans and adult planktivorous fishes has declined from impacts of quagga mussels and the predaceous cladoceran, Bythotrephes. These multiple stressors have altered zooplankton distributions and densities, and may lower larval fish growth and survival. Yet, in Lakes Michigan and Huron, some fish species still grow and recruit well in nearshore and offshore areas. To understand what drives fish recruitment, we sampled nutrients, fish larvae, and lower and upper food webs on nearshore-offshore transects from 2010-2013 in Lakes Huron and Michigan. A compensatory shift from large phytoplankton to the microbial food web—utilizable by both copepods and small clado...
Journal of Plankton Research, 1984
Journal of Great Lakes Research, 2010
The colonization of the zebra mussel (Dreissena polymorpha) in Saginaw Bay dramatically altered t... more The colonization of the zebra mussel (Dreissena polymorpha) in Saginaw Bay dramatically altered the phytoplankton community composition resulting in exclusion of light sensitive species and dominance of species with oligotrophic preferences and light resistance. In 1990, the NOAA Great Lakes Environmental Research Laboratory initiated a 7-year survey program to monitor changes in the lower food web of Saginaw Bay, where zebra mussels became established in the fall of 1991. To investigate shifts in the phytoplankton community composition over the 7-year period from 1990 to 1996 we searched for clusters of similar composition using multivariate principal component analysis (PCA) on proportions of 22 taxonomic groupings of the total phytoplankton density (cells per milliliter). We then used an agglomerative hierarchical clustering analysis of the PCA scores. We identified five characteristic phytoplankton communities in configurations that allowed recognizing four distinct periods in Saginaw Bay linked to the zebra mussel invasion. Significant changes were indicative of increased water clarity and eutrophic conditions being replaced by more oligotrophic conditions as clusters dominated by light sensitive species, such as the cyanobacteria Oscillatoria redekii, became immediately rare and clusters dominated by diatoms such as Cyclotella spp. became common. Microcystis spp., a light tolerant cyanobacteria not grazed by zebra mussel, dominated assemblages after 1994. The shifts in phytoplankton composition confirm that zebra mussels effects on phytoplankton communities are mediated by both direct (filtration) and indirect (nutrient cycling) mechanisms and also suggests that increased light penetration is an important mechanism behind some changes.
Journal of Great Lakes Research, 2003
The population characteristics of Bythotrephes were evaluated at seven nearshore (45 m) and eight... more The population characteristics of Bythotrephes were evaluated at seven nearshore (45 m) and eight offshore (80 to 150 m) stations in Lake Michigan during July and September 2000. Bythotrephes was generally most abundant at offshore stations, but mean density was patchy (4 to 1,326/m 2) among locations. During the year, there was a shift from reproduction by mainly instar III females to reproduction by instar II females. The shift generally reflected a change in the population structure of Bythotrephes at most sites during the same period. Bythotrephes populations in July were generally characterized by small body size at reproduction (instar II and III), large clutch size, and small neonates. Later in the season, body size at reproduction and neonates were larger and clutch size was smaller. Most growth (body length) of Bythotrephes occurred between instar I and II whereas little growth occurred between instar II and III. Spine length of Bythotrephes increased between July and September. The population characteristics and reproductive strategies of Bythotrephes appear to be adaptations to fish predation and food limitations.
Journal of Great Lakes Research, 2009
Colonization of the Laurentian Great Lakes by the invasive mussel Dreissena polymorpha was a sign... more Colonization of the Laurentian Great Lakes by the invasive mussel Dreissena polymorpha was a significant ecological disturbance. The invasion reached Saginaw Bay, Lake Huron, in 1991 and initially cleared the waters and lowered algal biomass. However, an unexpected result occurred 3 years after the initial invasion with the return of nuisance summer blooms of cyanobacteria, a problem that had been successfully addressed with the implementation of phosphorus controls in the late 1970s. A multi-class phytoplankton model was developed and tested against field observations and then used to explore the causes of these temporal changes. Model scenarios suggest that changes in the phytoplankton community can be linked to three zebra mussel-mediated effects: (1) removal of particles resulting in clearer water, (2) increased recycle of available phosphorus throughout the summer, and (3) selective rejection of certain Microcystis strains. Light inhibition of certain phytoplankton assemblages and the subsequent alteration of competitive dynamics is a novel result of this model. These results enhance our understanding of the significant role of zebra mussels in altering lower trophic level dynamics of Saginaw Bay and suggest that their physical reengineering of the aquatic environment was the major force driving changes in the phytoplankton community composition.
Journal of Great Lakes Research, 2010
During the spring isothermal mixing period, surface-mixed layer (SML) chlorophyll a and phytoplan... more During the spring isothermal mixing period, surface-mixed layer (SML) chlorophyll a and phytoplankton biomass (carbon) and water column primary productivity decreased substantially in 2007-2008 as compared to 1995-1998 (66%, 87%, and 70% decrease, respectively). Smaller or no decreases were noted between 1983-1987 and 1995-1998 (chlorophyll a 23% decrease, phytoplankton biomass 5% increase, and production 22% decrease). Phytoplankton composition also changed during the spring isothermal mixing period in 2007-2008 as compared to 1983-1987 and 1995-1998; all phytoplankton groups with the exception of cyanobacteria and chlorophytes exhibited dramatic reductions in 2007-2008. The pronounced changes in phytoplankton properties during spring mixing in 2007-2008 were attributed to the filtering activities of the quagga mussel (Dreissena rostriformis bugensis). During mid-and late thermal stratification periods, SML phytoplankton chlorophyll a and phytoplankton carbon and water column primary production exhibited only one significant change across all decades (midstratification production in 2007-2008 as compared to 1995-1998 and 1983-1987). Phytoplankton compositional changes in the SML also were limited during thermal stratification. The size of the deep chlorophyll layer (DCL) in
Journal of Geophysical Research, 2006