David M. Klarer

First Records of a European Cladoceran, Bythotrephes Cederstroemi, in Lakes Erie and Huron

Adult forms of the cladoceran Bythotrephes cederstroemi Schoedler (Cercopagidae), a widespread European freshwater zooplankter, occurred in the stomachs of four common species of Lake Erie fish (yellow perch, Perca flavescens; white perch, Morone americana; white bass, M. chrysops; and walleye, Stizostedion vitreum vitreum) collected in early October 1985. The fish were collected at several stations in the nearshore open waters of the central basin between Ashtabula and Huron, Ohio. Other investigators have seen this species in other locations in Lake Erie and also in Lake Huron. The report of B. cederstroemi in Lake Huron in December 1984 appears to be the first record of this species in North America.

Late-summer phytoplankton in western Lake Erie (Laurentian Great Lakes): bloom distributions, toxicity, and environmental influences

Phytoplankton abundance and composition and the cyanotoxin, microcystin, were examined relative to environmental parameters in western Lake Erie during late-summer (2003–2005). Spatially explicit distributions of phytoplankton occurred on an annual basis, with the greatest chlorophyll (Chl) a concentrations occurring in waters impacted by Maumee River inflows and in Sandusky Bay. Chlorophytes, bacillariophytes, and cyanobacteria contributed the majority of phylogenetic-group Chl a basin-wide in 2003, 2004, and 2005, respectively. Water clarity, pH, and specific conductance delineated patterns of group Chl a, signifying that water mass movements and mixing were primary determinants of phytoplankton accumulations and distributions. Water temperature, irradiance, and phosphorus availability delineated patterns of cyanobacterial biovolumes, suggesting that biotic processes (most likely, resource-based competition) controlled cyanobacterial abundance and composition. Intracellular microcystin concentrations corresponded to Microcystis abundance and environmental parameters indicative of conditions coincident with biomass accumulations. It appears that environmental parameters regulate microcystin indirectly, via control of cyanobacterial abundance and distribution.

Effects of Hydrological Flow Regime on Sediment-water Interface and Water Column Nitrogen Dynamics in a Great Lakes Coastal Wetland (Old Woman Creek, Lake Erie)

ABSTRACT Sediment-water interface nitrogen (N) transformations and water column ammonium cycling rates were measured along a stream to lake gradient at three sites within Old Woman Creek (OWC) and one near-shore Lake Erie site during two hydrological regimes: one with open flow to the lake after a rain event (July 2003), and another with a sand barrier blocking flow (July 2004). Net N2 effluxes in OWC at all times and at the near-shore Lake Erie site in July 2003 suggest that sediments are a N sink via denitrification. Observed dissimilatory nitrate reduction to ammonium (DNRA) may counteract some of this N removal, particularly when the creek mouth is closed. Upstream, a closed creek mouth led to higher sediment oxygen demand, net N2 flux, potential DNRA, and potential denitrification rates. The lake site exhibited lower rates of these processes with the creek mouth closed except denitrification potential, which was unchanged. Denitrification in OWC appeared to drive N limitation in the lower wet-land when the sand barrier was blocking flow to the lake. Higher potential versus in situ denitrification estimates imply that water column NO3− limits and drives denitrification in OWC. Water column to sediment regeneration ratios suggest that sediment recycling may drive primary production in the OWC interior when the creek mouth is closed and new N inputs from runoff are absent, but more data are needed to confirm these apparent trends. Overall, hydrological regime in OWC appeared to have a greater impact on sediment N processes than on water column cycling.

The Invasion and Spread of Phragmites australis during a Period of Low Water in a Lake Erie Coastal Wetland

Abstract Numerous studies have documented the invasion of wetland plants, yet few have tracked the invasion process from its early stages to subsequent large-scale, plant-community changes. The invasion of Phragmites australis (common reed) into the Great Lakes region is a recent phenomenon, facilitated by a decline in water lake levels. The spread of P. australis was tracked in the Old Woman Creek National Estuarine Research Reserve, a 60-ha Lake Erie coastal wetland, using a combination of low-altitude aerial photography and ground surveys during the period from 1993 to 2005. Since the late 1990s, the Old Woman Creek wetland has shifted from a predominantly open-water system to a shallow, water-emergent system. This shift has coincided with a decline in Lake Erie water levels, which are now closer to the long-term mean water level. Aerial photographs for the period 1993–2005 show a transition from the floating leaf Nelumbo lutea (American lotus), to a mixed-emergent community, to increasingly large monotypic beds of P. australis. This wetland perennial grass currently occupies about 22% of the lower wetland and is also a significant component of the emergent community that covers approximately 30% of the lower wetland. The emergent community and P. australis comprised less than 1% of the wetland area in 1993.

Aquatic Macrophytes and Algae at Old Woman Creek Estuary and Other Great Lakes Coastal Wetlands

Abstract Studies on aquatic macrophyte and algal floras of Old Woman Creek estuary (OWC) are examined in light of work conducted in other Great Lakes coastal wetlands. Since the last detailed inventory of aquatic macrophytes at OWC in 1973, many emergent and floating leaved species have become very restricted in their distribution, or have disappeared altogether. Possible causes for this vegetation shift are discussed. The algal flora of OWC is distinct from that in adjacent Lake Erie. Storm events are proposed to be a major factor in regulating phytoplankton species composition and dynamics in OWC. Primary productivity in OWC appears to be dominated by the algal communities rather than by macrophytes. The botanical research on Great Lakes coastal wetlands conducted to date has provided only cursory insights into these complex and dynamic communities. Knowledge of factors regulating these communities along with the roles these communities play in coastal wetland dynamics is needed. The impact of changing watershed use patterns on these wetland communities has not yet been determined. Finally, symbiotic and competitive interactions between the macrophyte and algal communities need to be elucidated.

Regulation of phytoplankton dynamics in a Laurentian Great Lakes estuary

The composition and dynamics of phytoplankton populations were examined in Old Woman Creek estuary, Lake Erie (USA). The centric bacillariophytes,Cyclotella atomus Hust.,Cyclotella meneghiniana Kütz., andAulacoseira alpigena (Grun.) Krammer, and the cryptophytes,Cryptomonas erosa Ehren. andRhodomonas minuta var. nannoplanctonica Skuja, dominated the phytoplankton most of the year. Chlorophytes, euglenophytes, and cyanophytes were observed less frequently. Estuarine and Lake Erie phytoplankton were considered distinct populations; lake taxa were largely confined to the estuary mouth and present only in low biomass. Maxima and minima of estuarine phytoplankton coincided with meteorological and hydrological forcing in the form of rainfall and subsequent storm-water inflows, respectively. Distinct population dynamics between the upper and lower estuary following storm events were attributed to the presence/absence of refugia serving as a source for repopulation by opportunistic taxa, fluctuating light conditions in the water column resulting from influx of particulate matter and resuspension of bottom sediments, and nutrient inputs associated with surface runoff and sub-surface interflow. Additionally, agricultural herbicides introduced by storm-water inflows potentially may affect and/or control the growth and physiological responses of individual taxa.

Prey Selection for the Exotic Cladoceran Bythotrephes Cederstroemi by Selected Lake Erie Fishes

The importance of zooplankton in the diet of yellow perch (Perca flavescens), white perch (Morone americana), walleyes (Stizostedion vitreum vitreum), and white bass (M. chry-sops)was assessed in the central basin of Lake Erie in 1985–1988. Zooplankton were collected by vertical hauls in 1987–1988 and fish with a rock-hopper trawl. Although copepods (calanoid and cyciopoid) were the major zooplankton in the plankton samples, they were not well represented in the fish diet. From 1985 through 1988, Cladocera became an increasingly important food – particularly a recent invader from Europe, Bythotrephes cederstroemi. It was a major component in the diet of yellow perch from June to October in both 1987 and 1988. The zooplankton consumption by white perch was more diverse until September, when B. cederstroemi became the major food item.

Microcystin concentrations and cell quotas in Saginaw Bay, Lake Huron

Distribution of the toxin microcystin was studied in Saginaw Bay, Lake Huron during two summer (August) cruises in 2003–2004. Intracellular microcystin concentrations averaged 1.1 μ g l− 1 (range 0.01–3.5 μ g l− 1), and extracellular concentrations averaged only 0.09 μ g l− 1 (range 0.01–0.18 μ g l− 1). Highest microcystin concentrations were found in the nearshore regions of the bay, which were shallow and had high total phosphorus concentrations. Microcystin concentrations were strongly correlated with Microcystis aeruginosa abundance (r = 0.8). M. aeruginosa abundance was strongly correlated with total phosphorus, and growth rates were negatively correlated with C:P ratio. Particulate nutrient ratios suggested that Saginaw Bay algae were severely phosphorus deficient. Microcystin cell quotas for M. aeruginosa averaged 140 fg cell− 1, and were not correlated with any environmental factor or growth rates. In Saginaw Bay, phosphorus availability primarily influences microcystin concentrations through direct control of M. aeruginosa abundance and growth rates, and not through direct control of cellular microcystin synthesis.

Zooplankton Dynamics in a Great Lakes Coastal Marsh

Abstract The zooplankton ecology of coastal marshes of the Laurentian Great Lakes is virtually unknown, although these systems are believed to perform important functions in the overall Great Lakes ecosystem. Thus, the composition and seasonal dynamics of the crustacean zooplankton communities of a riverine coastal marsh and the adjoining wave zone of Lake Erie were compared over 13 months. The open waters of the marsh upstream possessed a zooplankton community distinctly different from that in the wave zone, in terms of both the species composition and the population dynamics of some shared species. The downstream end of the marsh possessed a transitional zooplankton community which shared species with both the upstream marsh and wave zone communities and which had intermediate abundances of most species common to both habitats. A small summer storm runoff event briefly disrupted the development of several zooplankton populations in the marsh. Further studies are needed to identify the important factors which influence the marsh zooplankton ecology. Preliminary evidence indicates that the factors probably include planktivory by fishes and Chaoborus , aquatic macrophyte beds, a chemical and chlorophyll gradient from upstream to the lake, persistent high suspended sediments, and the flushing action of storm runoff events.

Benthic community structure in stands of Typha angustifolia And herbicide–treated and untreated Phragmites australis

We compared benthic community structure among stands of Typha angustifolia (narrow-leaf cattail) and herbicide-treated (Glypro) and untreated Phragmites australis (common reed) over two summers in a Lake Erie coastal wetland (i.e., drowned river mouth). Both macrophytes are invasives, but only Phragmites is currently controlled by herbicides because of its reputed “undesirable” effects on wetland community structure and function. Macroinvertebrate diversity was similar among stand types and relatively high (Shannon-Weaver indices ∼2.6–4.2), probably because of high system primary productivity and a mix of lentic and riverine species. Proportions of macroinvertebrate functional feeding groups were also similar, but Jaccard’s similarity indices were relatively low (29%–57%), suggesting macroinvertebrate compositional differences among stand types. Coleopterans particularly affected species presence/absence patterns, but their presence was associated with low water level rather than hydrophyte type per se. Moreover, total macroinvertebrate densities were greater in both Phragmites treatments than in Typha; a pattern generated mostly by gastropods (≥ 95% Gyraulus deflectus and Physella gyrina) and chironomids. Microalgal food supply likely plays a part in explaining these density differences, given diatom-dominated epiphyton was denser on submerged shoots of Phragmites than on Typha. Common diatom assemblages were similar among stand types, but species richness was significantly greater on untreated -Phragmites than on herbicide-treated, early senescent Phragmites and untreated-Typha. However, advanced senescence from herbicide application (∼3 months) did not apparently affect macroscale habitat suitability and structure above and below the waterline, given counts of ovipositing odonates (mostly Ischnura and Enallagma) and captures of juvenile fishes (> 90% Lepomis spp.) were similar among stand types. Overall, our results suggest that benthic community structure is comparable between similarly-aged stands (∼4 yrs old) of invading reed and cattail and is not directly or indirectly affected by Glypro application.