长荡湖、滆湖、竺山湾藻类功能群结构组成与环境因子的关系

为研究太湖流域上游长荡湖、滆湖、竺山湾三大典型浅水湖泊藻类功能群结构组成与环境因子的关系,基于2019年2月至2020年10月水文、水质及浮游植物数据,采用Q指数、香农-维纳多样性指数、TLI综合富营养化指数分析了3个湖泊的水质状况,采用非度量多维尺度变换(NMDS)分析了浮游植物群落结构组成特征,采用冗余分析探讨了浮游植物功能群与环境因子的关系。结果表明：长荡湖和滆湖水质整体属于轻度富营养化,竺山湾除冬季外,均属于中度富营养化;长荡湖、滆湖、竺山湾分别有浮游植物7门61属96种、8门75属129种和6门53属124种,分别划分为9、10和11个优势功能群;3个湖泊藻类功能群变化的共同环境因子是水温、高锰酸盐指数和总磷,而总氮和氮磷比对3个湖泊功能群结构变化的作用并不明显。     

Phytoplankton trends in the Great Lakes, 2001–2011

We describe recent trends in phytoplankton composition and abundance in the Laurentian Great Lakes using synoptic spring (April) and summer (August) sampling events from 2001 through 2011, a period of rapid shifts in pelagic food webs and water quality. Data analysis identified qualitative and quantitative changes in algal densities, biovolume, and taxonomic composition of assemblages. Since 2001, Lake Superior has changed subtly with an increase in small-celled blue-green algae in spring and a recent decline in summer centric diatoms, possibly a result of lake warming and changes in water quality. Spring phytoplankton declines mainly attributed to diatoms occurred in Lakes Huron and Michigan, a probable result of invasions by non-native dreissenids that have reduced pelagic nutrients and selectively consumed certain taxa. The decline in Lake Huron's spring phytoplankton biovolume was earlier and more severe than that in Lake Michigan, despite a faster and more abundant dreissenid invasion in Lake Michigan. Lake Erie's central basin had a notable increase in spring centric diatoms (largely Aulacoseira), while the whole of Lake Erie shows a summer increase in cyanobacteria, complementing that found in coastal regions. The composition of Lake Ontario's species assemblage shifted, but little overall change in algal abundance was observed with the exception of higher summer densities of cyanophytes. Additional mechanisms for shifts in the pelagic primary producers are described or hypothesized in the context of concurrent shifts in water quality and invertebrate populations. Tracking these trends and explaining driving factors will be critical to the management of lake conditions.     

Trends in Lake Erie zooplankton biomass and community structure during a 25-year period of rapid environmental change

Zooplankton play a key role in aquatic ecosystems, providing potential top-down control on phytoplankton and linking primary production to higher trophic levels. Thus, knowledge of zooplankton dynamics is fundamental to any assessment of the impacts of human driven rapid environmental change on lakes. Lake Erie has undergone eutrophication since the 1990s, resulting in summer harmful cyanobacterial blooms, dominated by Microcystis aeruginosa, since approximately 2003 in the western basin (WB) and 2008 in the central basin (CB). The effect of eutrophication on zooplankton in Lake Erie is unclear; few studies have characterized trends in zooplankton biomass and community structure during this period of rapid change. We used the Lake Erie Plankton Abundance Study (LEPAS) zooplankton dataset to analyze interannual trends in the dynamics of eight major zooplankton groups in the WB and CB during 1995–2020. In both basins, we found directional change in zooplankton biomass and community structure. These directional trends in zooplankton biomass overlaid approximate five-year cycles in nearly all taxa, potentially linked to the El Niño Southern Oscillation. Eutrophication was associated with an increase in the summer biomass of total zooplankton, calanoids, and large cladocerans but surprisingly, not cyclopoids, rotifers or small cladocerans. The surprisingly positive or neutral effect of eutrophication and M. aeruginosa on zooplankton biomass may be due to a combination of bottom-up (e.g. concurrent increases in more edible algae) and top-down (e.g. changes in planktivory) forces.     

The impact of phytoplankton community composition on optical properties and satellite observations of the 2017 western Lake Erie algal bloom

Since the early 2000s Lake Erie has seen a dramatic increase in phytoplankton biomass, manifested in particular by the rise in the severity of cyanobacteria blooms and the prevalence of potentially toxic taxa such as Microcystis. Satellite remote sensing has provided a unique capacity for the synoptic detection of these blooms, enabling spatial and temporal trends in their extent and severity to be documented. Algorithms for satellite detection of Lake Erie algal blooms often rely on a single consistent relationship between algal or cyanobacterial biomass and spectral indices such as the Maximum Chlorophyll Index (MCI) or Cyanobacteria Index (CI). Blooms, however, are known to vary significantly in community composition over space and time. A suite of phytoplankton and optical property measurements during the western Lake Erie algal bloom of 2017 showed highly diverse bloom composition with variable absorption and backscatter properties. Elevated backscattering coefficients were observed in the Maumee Bay, likely due to phytoplankton cell morphology and buoyancy regulating gas vacuoles, compared with typically Planktothrix dominated blooms in Sandusky Bay. MCI and CI calibrated to historical chlorophyll observations and applied to Sentinel 3's OLCI sensor accurately captured the 2017 bloom in Maumee Bay but underestimated the Sandusky Bay bloom by nearly 80%. The phycoerythrin-rich picocyanobacteria Aphanothece and Synechococcus were found in abundance throughout the western and central basins, resulting in substantial biomass underestimations using blue to green ratio-based algorithms. Potential misrepresentation of bloom severity resulting from phytoplankton optical properties should be considered in assessments of bloom conditions on Lake Erie.     

Effect of the Niagara River Chippawa Grass Island Pool on Water Levels of Lakes Erie,St. Clair,and Michigan-Huron

Because of renewed riparian interest stemming from the high Lake Erie water levels of the mid-1980s and mid-1990s, and the need for a concise summary of previous studies, a review and a new assessment of the impact of the Niagara River's Chippawa Grass Island Pool on Lake Erie water levels was undertaken. Numerous field and modeling studies dating from 1953 through 1988 provide different assessments of the impacts. The impacts reported by the studies range from “no measureable effect” to a 2 to 5 cm Lake Erie water level decrease. The different results are due to different methods and data, and the fact that the impacts are not directly measureable. A new Great Lakes routing model that more accurately reflects the upper Niagara River hydraulics by explicitly considering the management directive of the Chippawa Grass Island Pool is used to estimate the impacts of deviating from the present directive. The long-term impact of a 0.30 m increase or decrease from the current directive's long-term mean pool level on Lakes Erie, St. Clair, and Michigan-Huron levels is 5 cm, 4 cm, and 2 cm and −4 cm, −3 cm, and −2 cm, respectively. The lakes are minimally responsive to short-term changes in pool levels, with 50% of the Lake Erie impact achieved at about 6 months, and full impact achieved at about 2 years. The minimal lake response, the time lag to full impact, and the local problems resulting from directive deviations, make this a less favorable emergency response measure during periods of extreme lake levels than other alternatives.     

An ecosystem health assessment of the Detroit River and western Lake Erie

The Canada-U.S. State of the Strait Conference is a biennial forum with a 22-year history of assessing ecosystem status and providing advice to improve research, monitoring, and management of the Detroit River and western Lake Erie. The 2019 conference focused on assessing ecosystem health based on 61 indicators. Although there has been considerable improvement in the Detroit River since the 1960s, much additional cleanup is needed to restore ecosystem health. Western Lake Erie is now at risk of crossing several potential tipping points caused by the interactions of a variety of drivers and their stresses. This assessment identified eight environmental and natural resource challenges: climate change; population growth/transportation expansion/land use changes; chemicals of concern; human health/environmental justice; aquatic invasive species; habitat loss/degradation; nonpoint source pollution; and eutrophication/harmful algal blooms. Specific recommendations for addressing each challenge were also made. Climate change is the most pressing environmental challenge of our time and considered a “threat multiplier” whereby warmer, wetter, and more extreme climatic conditions amplify other threats such as poor air quality effects on vulnerable residents, species changes, and nonpoint source runoff and combined sewer overflow events that contribute to eutrophication and can manifest as harmful algal blooms. Our assessment found that investments in monitoring and evaluation are insufficient and that the region's intellectual and environmental capital is not being leveraged sufficiently to address current challenges. Continued investment in this transnational network is essential to support ecosystem-based management.     

Trends in Lake Erie phytoplankton biomass and community structure during a 20-year period of rapid environmental change

Since the 1990s, Lake Erie has experienced resurgent eutrophication due in part to climate change-driven increases in precipitation, which have combined with increasingly intensive agricultural practices in the region to produce excessive nutrient runoff into the lake. Harmful blooms of the cyanobacterium Microcystis aeruginosa (“Microcystis”) in Lake Erie’s western and central basins (WB and CB, respectively) have been a highly visible consequence of this eutrophication, however few studies have characterized intra- or interannual trends in less abundant, though likely more edible, phytoplankton taxa over the last 25 years. Here, we used the 20-year Lake Erie Plankton Abundance Study (LEPAS) dataset to quantify intra- and interannual trends in the dynamics of six major phytoplankton groups in the WB and CB during 1995–2015. Cyanobacteria biomass in the WB increased >1000-fold during this period, while biomass of all other major taxa groups increased between 10- and 100-fold. Early summer (June–July) and spring (May) communities saw more modest directional change in the biomass of both edible and less-edible taxa as well as community structure. Around 2008, the CB also began to experience Microcystis blooms concurrent with those in the WB, with similar, though less dramatic consequences for phytoplankton community structure and edible biomass. The biomass of several phytoplankton groups exhibited intra-annual oscillations with a ∼5-year period. The mechanisms underlying changes in the phytoplankton community structure and their consequences for higher trophic levels are not well understood, however increases in edible phytoplankton may be sustaining long-term upward trends in many zooplankton taxa.     

Hydrology influences generalist–specialist bird-based indices of biotic integrity in Great Lakes coastal wetlands

Marsh bird habitats are influenced by water levels which may pose challenges for interpreting bird-based indices of wetland health. We determined how much fluctuating water levels and associated changes in emergent vegetation influence the Index of Marsh Bird Community Integrity (IMBCI) using data collected in Great Lakes coastal wetlands by participants in Bird Studies Canada's Great Lakes Marsh Monitoring Program. IMBCI scores for 90 wetlands in Lake Erie and 131 wetlands in Lake Ontario decreased with decreasing water levels due to decreasing number of marsh-dependent species in Lake Erie and perhaps also in Lake Ontario. The average magnitude of the decrease in scores between extremely high and low water periods for wetlands with sufficient data was 15% in Lake Erie where water dropped 0.9 m on average (n = 11 wetlands) and 18% in Lake Ontario where water dropped 0.5 m (n = 7). Scores in Lake Erie increased with increasing Typha due to increasing numbers of marsh-dependent species and decreased with increasing Phragmites due to increasing numbers of generalist species. The opposite was observed in Lake Ontario, perhaps due to denser Typha and sparser Phragmites. Scores were explained by the naturally fluctuating water levels of Lake Erie, which favored Phragmites expansion and the regulated water levels of Lake Ontario which promoted Typha expansion. Scores were influenced by fluctuating water levels and associated changes in emergent vegetation. Inter-annual water level fluctuations should be considered when interpreting any indicator of wetland health that is based on marsh-dependent bird species.     

Evidence for a Trophic Cascade Effect on North-shore Western Lake Erie Phytoplankton Prior to the Zebra Mussel Invasion

Increasing summer total phosphorus (TP) concentrations measured in samples from a municipal water intake off the north shore of western Lake Erie during 1976 to 1983 were inconsistent with TP loads to the western basin of Lake Erie and with phytoplankton densities in the intake samples, both of which declined over the same time interval. The long-term (1976 to 1988) summer TP data were inversely correlated (r = −0.858) with summer average maximum daily wind velocities, suggesting that low wind velocities contributed to anoxia at the sediment-water interface and high sediment TP release rates in summer. While TP loading reductions in the late 1960s and early 1970s likely contributed to phytoplankton declines, continued phytoplankton declines during the late 1970s to early 1980s could not have been caused by continued reductions in TP loadings while TP concentrations increased. The phytoplankton declines of the 1980s are more likely attributable to changes in the trophic cascade associated with dramatic declines in some species of zooplanktivorous fish during the 1970s and 1980s as a result of a restored walleye population. Long term phytoplankton densities were fit (R² = 0.902) to a multiple regression model with western Lake Erie TP loads and an index of zooplanktivore density as independent variables; the zooplanktivore component of this model was the most significant contributor to the prediction of phytoplankton density. The implications of these findings for maintenance of good lake water quality include the need to maintain strong piscivore populations as well as reduced phosphorus loads.     

丹江口库湾浮游植物群落与环境因子关系研究

为掌握丹江口库湾富营养化状况,确保南水北调中线水源安全,于2017年分季节对丹江口库湾浮游植物群落结构和14项水文水环境因子进行了4次监测,并运用相关分析、冗余分析(RDA)等多元统计方法定量分析了浮游植物群落结构与环境因子的关系。监测发现,丹江口水库共鉴定出浮游植物7门57属,年均藻类密度4.89×10~6 cells/L,变幅2.73×10~6～6.87×10~6 cells/L。丹江口水库群落组成以硅藻、蓝藻和绿藻为主;结构变化规律为由春季的硅藻、蓝藻向夏季的绿藻、蓝藻和隐藻,以及秋、冬季的硅藻、隐藻和蓝藻转变。蓝藻门的束丝藻和隐藻门的隐藻为库湾四季的优势种。通过Shannon-Wiener指数、Margalef指数和Pielou指数分析认为,夏季藻类多样性高,绿藻优势度高,冬季藻类多样性相对较低,种群数量差异不显著。根据综合营养状态指数评价的结果可知,库湾富营养化程度处于中营养和富营养化水平,其中总氮贡献较大,总氮浓度范围在1.08～1.88 mg/L之间,均值为1.47 mg/L,磷为库湾富营养化的限制因子。RDA分析结果表明,除氮、磷营养盐外,温度、二氧化硅和电导率等也是影响库湾浮游植物群落分布的重要环境因子。     

Long-term dynamics of Lake Erie benthos: One lake,three distinct communities

Lake Erie has experienced multiple anthropogenic-driven changes in the past century, including cultural eutrophication, phosphorus abatement initiatives, and the introduction of invasive species. The benthos of Lake Erie has been studied infrequently over nine decades and can provide not only insights into the impact of environmental changes but can also be used to examine ecosystem recovery through time. We used multivariate analyses to examine temporal changes in community composition and to assess the major drivers of long-term changes in benthos. Eutrophication, water quality improvement, and dreissenid introduction were the major drivers of changes in benthos in the western basin, while hypoxia was a major factor in the central basin, and dreissenid introduction was most important in the eastern basin. Non-dreissenid community composition of the western basin has changed dramatically over 90 years from benthic species indicative of good water quality in the 1930s, with a diverse community dominated by Hexagenia, to one of low diversity dominated by oligochaetes and other pollution-tolerant species in the 1960s, followed by recovery in the early 2000s to a state similar to that reported in 1930. In contrast, the non-dreissenid benthic community of the central basin over 60 years was consistently dominated by low oxygen-tolerant taxa, signifying the persistence of hypoxia, the major community driver in this basin. The eastern basin community also changed dramatically, including the disappearance of Diporeia after the introduction of Dreissena in the 1990s and more recent declines in oligochaetes, amphipods, gastropods, sphaeriid clams, and leeches.     

Historical Changes in the Distribution of Threatened Channel Darter (Percina copelandi) in Lake Erie with General Observations on the Beach Fish Assemblage

Laurentian Great Lakes beach fish assemblages and the factors influencing their composition have been rarely investigated. In this study, we investigated whether north shore Lake Erie beach fish assemblages, and the distribution of the channel darter (Percina copelandi), a threatened species in Canada, have changed since the late 1940s. Over this time period, Lake Erie has been severely altered by the combined effects of eutrophication, overexploitation of fishery resources, habitat degradation, and invasive species. Seining data from 34 north shore beach sites indicate that a large decline in species richness has occurred, and that several introduced species are present. Three fishes of federal conservation concern and four species of recreational and commercial importance, previously captured from central and eastern Lake Erie basin beaches, were absent. This included the channel darter, which was collected from only one of six historical collection sites, indicating a substantial decline in its Lake Erie distribution. Potential causes of this decline include eutrophication-induced ecosystem changes, the effect of extensive shoreline modification on beaches, and the invasive round goby (Neogobius melanostomus). Nearshore bottom trawls of Long Point Bay indicate that, since the establishment of round goby, concurrent short-term declines in the abundance of two other native benthic fishes (johnny darter Etheostoma nigrum, and logperch P. caprodes) have occurred.     

Assessing and addressing the re-eutrophication of Lake Erie: Central basin hypoxia

Relieving phosphorus loading is a key management tool for controlling Lake Erie eutrophication. During the 1960s and 1970s, increased phosphorus inputs degraded water quality and reduced central basin hypolimnetic oxygen levels which, in turn, eliminated thermal habitat vital to cold-water organisms and contributed to the extirpation of important benthic macroinvertebrate prey species for fishes. In response to load reductions initiated in 1972, Lake Erie responded quickly with reduced water-column phosphorus concentrations, phytoplankton biomass, and bottom-water hypoxia (dissolved oxygen < 2 mg/l). Since the mid-1990s, cyanobacteria blooms increased and extensive hypoxia and benthic algae returned. We synthesize recent research leading to guidance for addressing this re-eutrophication, with particular emphasis on central basin hypoxia. We document recent trends in key eutrophication-related properties, assess their likely ecological impacts, and develop load response curves to guide revised hypoxia-based loading targets called for in the 2012 Great Lakes Water Quality Agreement. Reducing central basin hypoxic area to levels observed in the early 1990s (ca. 2000 km²) requires cutting total phosphorus loads by 46% from the 2003–2011 average or reducing dissolved reactive phosphorus loads by 78% from the 2005–2011 average. Reductions to these levels are also protective of fish habitat. We provide potential approaches for achieving those new loading targets, and suggest that recent load reduction recommendations focused on western basin cyanobacteria blooms may not be sufficient to reduce central basin hypoxia to 2000 km².     

Lake Erie's ecological history reconstructed from the sedimentary record

We evaluated the recent ecological history of Lake Erie from diatoms and geochemistry in sediment cores. Two major transition points in the ecology of the western basin (WB; 1985 and 2008) and central basin (CB; 1935 and 1982) were defined. Changes in abundance of diatom eutrophic indicators and geochemical markers were interpreted as a degradation in water quality after 1935 due to the effects of increased population, agriculture, and industrialization until abatement measures were enacted in the 1970s and 1980s. Diatom indicators suggested modest recovery from eutrophic conditions in Lake Erie, however diatom-inferred total phosphorus suggested that despite abatement efforts total phosphorus was not reduced below pre-impact levels. The effects on diatoms of increased temperature and dissolved silica also became apparent in the 1980s, and in the WB recent shifts were likely caused by increased pollution and recent climatic warming. Based on stratigraphic changes since 1985, the diatom trajectory suggests the phytoplankton of Lake Erie will likely remain in a state of flux for the near future due to a variety of countervailing impacts including unknown effects of mitigation efforts, legacy pollution, climate change, and changing upstream conditions.     

Nutrient management in Lake Erie: Evaluating stakeholder values,attitudes, and policy preferences

Harmful algal blooms (HABs) have impaired Lake Erie’s western basin water quality since the 1960s. Though scientists agree that eutrophication is a key driver of HABs in Lake Erie, the role of nitrogen is still the subject of debate. The problem is twofold: (1) uncertainty in the specific causes of HABs can lead to inappropriate management solutions, and (2) managing a cross-boundary watershed requires collaboration and agreement on apt solutions from multiple stakeholders as well as many U.S. states and Canadian provinces. In our study, we interviewed 29 stakeholders actively involved in western Lake Erie’s watershed. We analyzed the stakeholders’ values, attitudes, and policy preferences to understand their differences, similarities, and their effects on management decisions. We found that stakeholders agree on the urgency of the problem and the necessity for increased nutrient management in Lake Erie’s western basin. Furthermore, we found that stakeholders can be represented as distinct clusters based on their values, and these value-based clusters are associated with different policy preferences. The different opinions and preferences of these value clusters span across stakeholder sectors and may affect efforts toward policy change. Stakeholders often question the feasibility and effectiveness of existing policies and policy plans. The findings shed new light on the relationship between stakeholder type and environmental values, attitudes, and policy preferences. Collaboration on HABs in Lake Erie will require open lines of communication both to improve policy and to cultivate trust among the multiple parties in this diverse watershed.     

Changes in Lake Erie benthos over the last 50 years: Historical perspectives,current status,and main drivers

During the last 50 years the ecosystem of Lake Erie has experienced major environmental changes, from anthropogenic eutrophication in 1930–1960s, to nutrient and pollution abatement in the 1970s, and then the introduction of exotic dreissenids in the 1980s. We used multivariate statistical techniques to examine long-term changes in the zoobenthic community, comparing contemporary collections (2009, 2011–2012) and historical data (1963–1965, 1978–1979, 1993, and 1998). The Lake Erie benthic community underwent significant changes during each decade examined, showing signs of recovery following ecosystem restoration in the 1970s, but then experiencing major structural and functional changes after dreissenid (Dreissena polymorpha and D. r. bugensis) introductions. There was a significant temporal trend in community composition changes from 1963 to 2012, and the largest difference was found between pre- and post-dreissenid invasion communities. Currently the lake-wide benthic community is dominated by dreissenids both in density (41%) and total wet biomass (97%), followed by oligochaetes and chironomids. The largest benthic density was found in the central basin, and the greatest biomass in the eastern basin. The number of exotic species found in benthic surveys increased every decade, from 1 in 1963 to 10 in 2009–2012, and the majority of the invaders were molluscs. Whereas the role of benthic invaders in community diversity is still low, their impact has had enormous consequences for the whole ecosystem.     

Lake Erie Nutrient Loads, 1970–1980

The Buffalo District, Corps of Engineers’ Lake Erie Wastewater Management Study and Heidelberg College's Water Quality Laboratory supported a tributary water quality monitoring program from 1974 to 1980 of the major United States tributaries to Lake Erie. This program was designed to measure nutrient loads by monitoring concentration changes occurring in association with increased streamflow. Soluble orthophosphate loads, chloride loads, and silica loads decreased from 1970 to 1980. Nitrogen species were highly variable and increased over the period. Total phosphorus loads to Lake Erie have decreased during the period as a result of phosphorus removal at wastewater treatment plants. The effect of the phosphorus reductions can be seen in the lake concentrations and were predicted by a three-basin phosphorus budget model developed in the early 1970s. The results show that phosphorus removal programs are having the predicted effect on Lake Erie water quality.     

2008~2014年滇池水质时空变化特征分析

滇池位于昆明市南部,是该市重要的水源地,支持着昆明市现代工业、农业、旅游业等的发展,分析其水质的时空变化十分重要。利用2008~2014年水质监测数据,分析了滇池主要污染物、富营养化指数和浮游植物丰度的时空变化特征。结果发现：滇池总磷、总氮、氨氮、高锰酸盐指数年尺度上整体呈减小的趋势,不同监测点的变化趋势存在一定的差异;富营养化指数年尺度上表现为减小的趋势,年内变化差异较大,6~8月富营养化指数较高,其他月份富营养化指数较低;浮游植物丰度年尺度上呈下降趋势,年内变化表现为6~8月浮游植物丰度较大,其他月份丰度较小。滇池的草海及邻近区域主要污染物、富营养化指数和浮游植物丰度大于外海部分。得益于滇池治理力度的加强,近年来滇池水质得到较大改善。     

Quantification of the Lake Trophic Typologies of Naumann (Surface Quality) and Thienemann (Oxygen) with Special Reference to the Great Lakes

Separate trophic scales and indices are developed for two of the most significant symptoms of eutrophication: surface water quality and hypolimnetic dissolved oxygen depletion. The scales are made comparable by expressing them in dimensionless form with a lower bound of zero and a mesotrophic range from 5 to 10. In this way, the two symptoms can be compared and their relative importance judged. This is done for the Great Lakes with the result that for both scales Lakes Superior, Huron, and Michigan are classified as oligotrophic. However, while central and eastern Lake Erie and Lake Ontario are classified as mesotrophic in terms of surface water quality, they range from eutrophic (central Lake Erie) to oligotrophic (Lake Ontario) on the oxygen scale. This is because, although these lakes are similar in surface water quality, their hypolimnion thicknesses range from approximately 4 m for central Erie to 70 m for Lake Ontario. Because of its shallowness, western Lake Erie does not have a persistent oxygen problem. In terms of surface quality it is classified as eutrophic.We have attempted to relate the two scales by correlating surface primary production and areal depletion rate. The results indicate that for lakes of similar primary production, areal oxygen depletion is directly proportional to hypolimnion thickness.     

Detrended Correspondence Analysis of Phytoplankton Abundance and Distribution in Sandusky Bay and Lake Erie

The purpose of this study was to determine if phytoplankton communities in Sandusky Bay were distinct from those of Lake Erie. Samples were taken from 11 sites along a 50 km transect extending from the lower reaches of the Sandusky River, through Sandusky Bay and into the western basin of Lake Erie to identify factors correlated with identifiable patterns in distribution and abundance of summer phytoplankton. Detrended correspondence analysis (DCA), an ordination technique used to describe patterns in complex data sets, arranged the sample sites along an ordination axis that explained 76% of the variation in the phytoplankton abundance data matrix, and produced the following sequence of ordination axis scores: Sandusky Bay→ Lake Erie→ Sandusky River. DCA axis I scores strongly correlated with total phosphorus, soluble reactive phosphorus, algal phosphatase activity, dissolved oxygen, conductivity, turbidity, and alkalinity, but not chloride concentration, suggesting that phytoplankton abundance and distribution were related to phosphorus availability and not simply due to the passive movement of water along the transect. Bacterial abundance correlated with DCA axis I, suggesting that phytoplankton-bacterial interactions may be important in understanding distributional patterns of Sandusky Bay phytoplankton.