Environmental control of the dominant phytoplankton in Aras Reservoir (Iran): A multivariate approach

This study was undertaken to determine the phytoplankton structure and the environmental variables comprising the driving factors leading to cyanobacterial blooms in Aras Reservoir. Sampling was carried out seasonally at five sampling sites along the main body of the reservoir. Samples were collected for phytoplankton identification and enumeration, chemical analyses and chlorophyll‐a (Chl‐a) concentrations at each sampling site. Principal component analysis (PCA) and two‐way unweighted pair group method with arithmetic mean (UPGMA) were performed to determine the environmental variables affecting phytoplankton community dynamics. Seventy‐two species belonging to five divisions were determined during this study. Cyanobacteria contained the highest density (74%) during the study period, with Pseudanabaena limnetica being the most abundant species. The Shannon diversity index was low (0.44–1.87), indicating a high level of cyanobacteria dominance and eutrophic water status. Principal component analysis indicated that total phosphorus and temperature were significantly associated with cyanobacteria growth. Two‐way clustering by UPGMA indicated a close relationship among sampling sites during the same season from the perspective of the phytoplankton density. The findings of this study suggested Aras Reservoir could be highly affected by agricultural runoff and untreated sewage loadings. Thus, the proper use of fertilizers and sewage treatment should be taken into account in considering effective conservation and management plans.     

Potamoplankton of the Maumee River during 2018 and 2019: The relationship between cyanobacterial toxins and environmental factors

While algal blooms are common in eutrophic lakes, blooms can also occur in tributaries that load nutrients into the lake. We sampled six sites along a 122-km stretch of the Maumee River May through October 2018 and 2019 at weekly to biweekly intervals to determine if algal blooms occur, in particular toxic cyanobacteria, and to provide insights on potential environmental drivers of blooms. Samples were analyzed for concentrations of potamoplankton (=riverine phytoplankton), chlorophyll a, nutrients, cyanobacterial toxins, microcystins and saxitoxins, and cyanotoxin genes (mcyE and sxtA). Extreme precipitation in 2019 resulted in more high discharge events during 2019 than in 2018. Chlorophyll a ranged from 50 µg/L to 300 µg/L during periods of low discharge (<50 m³/s), and green algae and diatoms accounted for the majority of the chlorophyll a. In both years, cyanobacteria comprised a low proportion of all chlorophyll a, usually<20 %, but microcystins and saxitoxins were detectable in 38.7 % and 16.7 % samples, respectively, and mcyE and sxtA were detected in 36.2 % and 59.7 % samples, respectively. Therefore, cyanotoxins were present even when cyanobacteria were not at bloom densities. Chlorophyll a, cyanotoxin genes, and microcystins negatively correlated with discharge rate measured on the date of sample collection. Together our results suggest that cyanotoxins can occur in any portion of the Maumee River during low discharge conditions. Climate change is expected to reduce precipitation during the warm summer months in the Maumee River watershed and thus possibly increase the frequency of low discharge conditions that favor cyanobacteria.     

Re-eutrophication of Lake Erie: Correlations between tributary nutrient loads and phytoplankton biomass

Both abiotic and biotic explanations have been proposed to explain recent recurrent nuisance/harmful algal blooms in the western basin and central basin of Lake Erie. We used two long-term (> 10 years) datasets to test (1) whether Lake Erie total phytoplankton biomass and cyanobacterial biomass changed over time and (2) whether phytoplankton abundance was influenced by soluble reactive phosphorus or nitrate loading from agriculturally-dominated tributaries (Maumee and Sandusky rivers). We found that whereas total phytoplankton biomass decreased in Lake Erie's western basin from 1970 to 1987, it increased starting in the mid-1990s. Total phytoplankton and cyanobacterial seasonal (May–October) arithmetic mean wet-weight biomasses each significantly increased with increased water-year total soluble reactive phosphorus load from the Maumee River and the sum of soluble reactive phosphorus load from the Maumee and Sandusky rivers, but not for the Sandusky River alone during 1996–2006. During this same time period, neither total phytoplankton nor cyanobacterial biomass was correlated with nitrate load. Consequently, recently increased tributary soluble reactive phosphorus loads from the Maumee River likely contributed greatly to increased western basin and (central basin) cyanobacterial biomass and more frequent occurrence of harmful algal blooms. Managers thus must incorporate the form of and source location from which nutrients are delivered to lakes into their management plans, rather than solely considering total (both in terms of form and amount) nutrient load to the whole lake. Further, future studies need to address the relative contributions of not only external loads, but also sources of internal loading.     

Spatial and Temporal Dynamics of Suspended Particle Characteristics and Composition in Navigation Pool 19 of the Upper Mississippi River

Suspended particles are an essential component of large rivers influencing channel geomorphology, biogeochemical cycling of nutrients, and food web resources. The Upper Mississippi River is a large floodplain river that exhibits pronounced spatiotemporal variation in environmental conditions and biota, providing an ideal environment for investigating dynamics of suspended particles in large river ecosystems. Here we investigated two questions: (i) How do suspended particle characteristics (e.g. size and morphology) vary temporally and spatially? and (ii) What environmental variables have the strongest association with particle characteristics? Water sampling was conducted in June, August, and September of 2013 and 2014 in Navigation Pool 19 of the Upper Mississippi River. A FlowCAM® (Flow Cytometer and Microscope) particle imaging system was used to enumerate and measure particles 53–300 μm in diameter for size and shape characteristics (e.g. volume, elongation, and symmetry). Suspended particle characteristics varied considerably over space and time and were strongly associated with discharge and concentrations of nitrate + nitrite (NO₃^?) and soluble reactive phosphorus. Particle characteristics in backwaters were distinct from those in other habitats for most of the study period, likely due to reduced hydrologic connectivity and higher biotic production in backwaters. During low discharge, phytoplankton and zooplankton made up relatively greater proportions of the observed particles. Concurrently during low discharge, concentrations of chlorophyll, volatile suspended solids, and total phosphorus were higher. Our results suggest that there are complex interactions among space, time, discharge, and other environmental variables (e.g. water nutrients), which drive suspended particle dynamics in large rivers. Copyright © 2017 John Wiley & Sons, Ltd.     

Warming and eutrophication effects on the phytoplankton communities of two tropical water systems of different trophic states: An experimental approach

Both global warming and eutrophication are predicted to promote cyanobacterial blooms. At the same time, how tropical phytoplankton communities exhibiting different trophic state systems will respond to temperature variations is less clear. To investigate the effects of temperature changes and nutrient additions on phytoplankton communities, and gain insights regarding possible resistance to these effects, the present study focused on testing the hypothesis that temperature variations and nutrient additions will have a stronger effect on cyanobacteria dominance in eutrophic water system than in oligo‐mesotrophic water systems. Experiments were conducted with phytoplankton communities from two aquatic ecosystems exhibiting different trophic states. To this end, water samples from a eutrophic and oligo‐mesotrophic system were collected and incubated at 25 and 30ºC. Samples receiving additional surplus nitrogen (N) and phosphorus (P) inputs were included to serve as eutrophication treatments. The study results indicated that temperature variations alone did not promote cyanobacteria in water from either the oligo‐mesotrophic or eutrophic water system. However, nutrient enrichment of the water from the eutrophic system significantly boosted the cyanobacteria, with the biomass increasing by factor of 10 for both the 25°C and 30°C treatments. In contrast, eutrophication of the water from the oligo‐mesotrophic system did not change the relative contribution of phytoplankton groups, with the response ratios being much lower than those for the water from the eutrophic system. Although based on a simple experimental design, the results of the present study suggest that cyanobacteria dominance is favoured by further nutrient additions for eutrophic water systems, independently of any direct temperature effects, and that more pristine environments possess some resistance against eutrophication effects. Since global warming is assumed to indirectly intensify eutrophication symptoms, the results of the present study underscore the importance of nutrient control.     

洪泽湖浮游藻类变化动态及影响因素

针对2011年7月至2013年10月在洪泽湖11个采样点20次采样获得的湖水表层浮游藻类和水质理化指标数据,采用Shannon-Wiener指数H和优势度指数Y进行数据统计处理,分析洪泽湖浮游藻类时空分布动态及其影响要素。结果表明:洪泽湖浮游藻类共有7门60属144种,主要包括绿藻门66种、硅藻门36种、蓝藻门23种、裸藻门13种。浮游藻类群落具有明显的时空异质性,物种丰富度夏季最高,秋季中等,冬春季最低;西北部(成子湖区)和河流入湖口(溧河洼)高,湖心和河流出湖口(蒋坝)低;浮游藻类细胞密度全湖平均值变幅为157万~604万个/L,夏秋高,冬春--低;成子湖区等静水区高,入湖和出湖口低。浮游藻类组成和细胞密度的时间动态与温度、水位及营养盐(TN、TP等)的季节差异有关,而其空间动态与水动力因素和营养盐(NH3-N)的空间差异有关。建议限制洪泽湖营养盐陆地输入,合理调控洪泽湖水动力,以遏制洪泽湖蓝藻水华的发生。     

Advection,growth and nutrient status of phytoplankton populations in the lower River Murray,South Australia

To investigate the link between river flow, nutrient availability and development of algal blooms, growth rates of the major phytoplankton species were examined in situ in the lower River Murray, South Australia over the 1994/1995 summer. Eight sites were selected over a 54 km reach between Lock 1 and Nildottie and growth rates estimated by monitoring mean cell density in time‐aligned parcels of water as they travelled downstream. Discharge at Lock 1 during the period of study (3000–5000 ML day⁻¹) typified summer entitlement flows to South Australia. A large, shallow floodplain lake (lagoon), with an hydraulic connection to the river, supported a large population of cyanobacteria in summer, but inputs to the main channel did not substantially affect the abundance and composition of river phytoplankton. Mean net growth rates of Anabaena circinalis and A. flos‐aquae f. flos‐aquae were 0.132 and 0.176 day⁻¹, respectively, although individual rates varied from positive to negative. In contrast, the mean growth rate of the filamentous diatom Aulacoseira granulata was −0.15 day⁻¹, reflecting a decrease in population size with advection downstream. Mean cell densities of the three species did not exceed 5000 cells mL⁻¹ throughout the study. Growth bioassays conducted in the laboratory indicated that nitrogen was often the nutrient limiting algal growth, although it was not established whether nitrogen was limiting in situ. A conceptual model is presented, linking these findings with those of other work on the lower River Murray, to summarize the physical and chemical environmental factors governing the abundance of cyanobacteria in this reach of the river. Copyright © 2000 John Wiley & Sons, Ltd.     

An analysis of satellite-derived chlorophyll and algal bloom indices on Lake Winnipeg

Lake Winnipeg has experienced dramatic increases in nutrient loading and phytoplankton biomass over the last few decades, accompanied by a marked shift in community composition towards the dominance of cyanobacteria. Comprehensive lake-wide observations of algal blooms are critical to assessing the lake's health status, its response to nutrient management practices, and an improved understanding of the processes driving blooms. We present an analysis of the spatial and temporal variability of algal blooms on Lake Winnipeg using satellite-derived chlorophyll and indices for algal bloom intensity, spatial extent, severity, and duration over the period of ESA's MERIS mission (2002–2011). Imagery documented extensive blooms covering as much as 93% of the lake surface. Bloom conditions were analysed in the context of in-lake and watershed processes to gain further insight on the drivers of bloom events. Day to day bloom variability was driven primarily by intermittent wind mixing events, with quiescent periods leading to the formation of dense surface blooms. Seasonal bloom distribution was consistent with light limitation in the south basin and lake circulation transporting bloom material towards the north-east shore. Inter-annual variability in average bloom severity was related to both total phosphorus (TP) loadings and summer lake surface temperatures. Results provide a valuable historical time series of bloom conditions to which ongoing observations from Sentinel-3's OLCI sensor can be added for longer term monitoring and change detection.     

Estimating submarine groundwater discharge and associated nutrient inputs into Daya Bay during spring using radium isotopes

Daya Bay, a semi-enclosed bay in the South China Sea, is well known for its aquaculture, agriculture, and tourism. In recent years, many environmental problems have emerged, such as the frequent(almost yearly) occurrence of harmful algal blooms and red tides. Therefore,investigations of submarine groundwater discharge(SGD) and associated nutrient inputs to this bay have important theoretical and practical significance to the protection of the ecological system. Such a study was conducted using short-lived radium isotopes ~(223)Ra and ~(224)Ra. The estimated SGD fluxes were 2.89 × 10~7 m~3/d and 3.05 × 10~7 m~3/d based on ~(223)Ra and ~(224)Ra, respectively. The average SGD flux was about 35 times greater than that of all the local rivers. The SGD-associated dissolved inorganic nitrogen(DIN) and dissolved inorganic phosphorus(DIP)fluxes ranged from 1.95 × 10~6 to 2.06 × 10~6 mol/d and from 5.72 × 10~4 to 6.04 × 10~4 mol/d, respectively. The average ratio of DIN to DIP fluxes in SGD was 34, much higher than that in local rivers(about 6.46), and about twice as large as the Redfield ratio(16). Our results indicate that SGD is a significant source of nutrients to the bay and may cause frequent occurrence of harmful algal blooms. This study provides baseline data for evaluating potential environmental effects due to urbanization and economic growth in this region.     

福建省山仔水库富营养化特征

通过水质主要指标的时空变化以及气象、水文条件等因素,研究山仔水库富营养化特征。研究表明,山仔水库1997~2005年年平均质量浓度总氮为0.59~2.89mg/L,总磷为0.035~0.063mg/L,总氮、总磷从1997年开始呈现下降趋势,2001年后又有所回升,水库的进口、支流入口的总磷、总氮、COD、藻类数量相对较高。在1年内藻类种群冬、春季以硅藻为主,其余季节以蓝藻为主,水花微囊藻为优势种群持续的时间最长,每年的春末、秋初有2个藻类生长的高峰期。枯水年份水库水体滞留时间长,水力交换能力差,是导致2000~2004年水库水华频繁暴发的主要原因。     

Effects of temperature and nutrients on phytoplankton biomass during bloom seasons in Taihu Lake

Long-term variations of phytoplankton chlorophyll-a (Chl-a), nutrients,and suspended solids (SS) in Taihu Lake, a large shallow freshwater lake in China, during algal bloom seasons from May to August were analyzed using the monthly investigated data from 1999 to 2007. The effective accumulated water temperature (EAWT) in months from March to June was calculated with daily monitoring data from the Taihu Laboratory for Lake Ecosystem Research (TLLER).The concentrations of Chl-a and nutrients significantly decreased from Meiliang Bay to Central Lake. Annual averages of the total nitrogen (TN), total phosphorus (TP), and Chl-a concentrations, and EAWT generally increased in the nine years. In Meiliang Bay, the concentration of Chl-a was significantly correlated with EAWT, ammonia nitrogen (NH4+-N ), TN, the soluble reactive phosphorus (SRP),TP, and SS. In Central Lake, however, the concentration of Chl-a was only correlated with EAWT, TP, and SS. Multiple stepwise linear regression revealed that EAWT, dissolved total phosphorus (DTP), and TP explained 99.2% of the variation of Chl-a in Meiliang Bay, and that EAWT, NH4+-N, and TP explained 98.7% of the variation of Chl-a in Central Lake. Thus EAWT is an important factor influencing the annual change of phytoplankton biomass. Extreme climate change, such as extremely hot springs or cold springs, could cause very different bloom intensities in different years. It is also suggested that both nutrients and EAWT played important roles in the growth of phytoplankton in Taihu Lake. The climate factors and nutrients dually controlled the risk of harmful algal blooms in Taihu Lake. Cutting down phosphorus and nitrogen loadings from catchments should be a fundamental strategy to reduce the risk of blooms in Taihu Lake.     

基于SMDPSO算法的呼伦湖藻华遥感监测

水体富营养化所引起的藻华爆发现象是我国面临的重大环境问题之一。以内蒙古呼伦湖为研究区,采用基于离散粒子群优化的光谱匹配（SMDPSO）算法提取藻华,以浮游藻类指数（FAI）的分类结果作为验证数据进行精度检验。然后分析2009-2018年藻华的时空变化特征,并将此算法应用于黄海。结果表明：SMDPSO算法可以有效地识别呼伦湖藻华,与FAI分类结果之间的R²为0.97,RMSE为0.22 km²;呼伦湖藻华爆发于7-8月,且主要出现在湖泊边缘;SMDPSO算法既可以较好地识别以蓝藻为优势门的呼伦湖藻华,也可以提取黄海的浒苔（绿藻）;SMDPSO算法不仅保留了光谱指数法精度高的特点,而且它还具有成本低、参数少、无需人工干预的优势。该研究为藻华遥感监测提供了新的工具,有助于控制湖泊水体富营养化和改善水生态环境。     

Influence of extreme drawdown on water quality downstream of a large water storage reservoir

The Serial Discontinuity Concept (SDC) proposes that dams have the potential to affect the downstream ecological condition of rivers. While the SDC was developed principally around changes to physical habitat or temperature, reservoirs also have the potential to impact on downstream water quality, including algal community structure. In the current study we examined the impacts of an extreme drawdown event on nutrient loads and algal community structure downstream of a large water storage reservoir in south‐eastern Australia—Lake Hume. The lake was a net exporter of carbon, nitrogen, phosphorus and iron during the study period and was a net sink for manganese. Most of the carbon, nitrogen and phosphorus exported from the lake was in the form of algal biomass. Processes in the lake also influenced the downstream algal community structure. Upstream of the reservoir green algae were the most dominant species; within and downstream of the reservoir cyanobacteria dominated. Much of the algal biomass found at the downstream sites appeared to originate in Lake Hume and was physically transported downstream. Copyright © 2009 John Wiley & Sons, Ltd.     

Fish assemblages and biotic integrity of a highly modified floodplain river,the Upper Mississippi,and a large,relatively unimpacted tributary,the Lower Wisconsin

The Upper Mississippi River is a dynamic floodplain river that has been largely transformed by navigational levees and dams since the 1930s. The pools upstream of each dam are lake‐like and only about the upper third of each reach retains a riverine character. In contrast, the Wisconsin River is not managed for commercial navigation and today its lower 149 km represent one of the least‐degraded large river reaches in central North America. Riverine reaches in both the Mississippi and Wisconsin rivers have similar macro‐habitats including numerous islands, large side channels, and connected backwaters and floodplain lakes. In this study, shoreline electrofishing samples were collected during summer 2002 and 2003 to characterize resident fish assemblages. We compared fish species abundance, biomass, and biotic integrity along main and side channel borders between the Upper Mississippi River and the Lower Wisconsin River. We expected that, in the absence of environmental degradation, fish composition and structure would be similar between the Mississippi and Wisconsin rivers, and between channel types within each river. Nonmetric multidimensional scaling and redundancy analysis revealed that fish species in the Mississippi River, unlike in the Wisconsin River, were characteristic of non‐riverine habitats. We consider non‐riverine fish assemblages indicative of environmental impairment. The main and side channel sites in the Mississippi River had more variable fish assemblages than the Wisconsin River. Analyses of fish index of biotic integrity scores showed that environmental condition was excellent for both channel types in the Wisconsin River, whereas in the Mississippi River the side channel was rated good and the main channel only fair. We conclude that differences between the two rivers and between channel types of the Mississippi River are consistent with direct and indirect effects of navigation. This study demonstrates the utility of a fish index of biotic integrity, an inexpensive and rapid bioassessment tool, for detecting change in ecological health on one of the world's largest rivers. Copyright © 2006 John Wiley & Sons, Ltd.     

Assessment of physico‐chemical properties of water and phytoplankton bloom formation in a eutrophic pond using multivariate analysis

An investigation of the water chemistry and phytoplankton bloom formation characteristics of a seasonal earthen pond located in the Alappuzha District, Kerala (India) was carried out during November 2011 to May 2012. Twelve important physico‐chemical parameters (temperature, Secchi disc transparency, pH, electrical conductivity EC), dissolved oxygen (DO), biochemical oxygen demand (BOD), ammonia‐nitrogen, nitrite‐nitrogen, nitrate‐nitrogen, total phosphorus (TP), dissolved iron and chlorophyll a related to phytoplankton growth in the pond were the focus of the present study. Chlorophyll a was used as a measure of phytoplankton biomass. The pond developed subsurface phytoplankton blooms of Chlorella vulgaris, Aphanothece sp., Leptosira sp., Lepocinclis globulus and Lepocinclis fusiformis. Visible scums of Lepocinclis globulus and Euglena proxima was also observed during March 2012. Principal component analysis was performed to understand the biochemical processes in the pond ecosystem leading to the Euglena spp. bloom.     

Limnological characteristics and trophic state of Paso de las Piedras Reservoir: An inland reservoir in Argentina

The current trophic status of Paso de las Piedras Reservoir was evaluated by analysing different physicochemical, biological and environmental variables, in relation to its water quality, and application of two different classification criteria. Water quality sampling was conducted at four sampling sites from June 2004 to June 2005. During this study, 183 phytoplankton taxa were identified. The phytoplankton abundance exhibited a maximum of 368.037 × 10³ cells.mL^?1 in February 2005, and at least 1.133 × 10³ cells.mL^?1 in October 2004. An almost exclusive dominance of Cyanobacteria was observed between December 2004 and May 2005, the product of a large relative abundance of Anabaena circinalis and Microcystis natans which, together with other companions, were the reason for an algal bloom characterized by an average density of 133.05 × 10³ cells.mL^?1, and an average chlorophyll concentration of 28.7 mg.m^?3. These study results indicate that the seasonal variations of physical, chemical and biological parameters in the waters of this reservoir were essentially a consequence of environmental and hydrological conditions in the dam area. In contrast, the spatial variations inside the lake were the result of the characteristics of the water inflow provided by its two main tributaries. The N:P ratio suggests neither nutrient is a limiting factor for maximum algal biomass in the lake, indicating that variations in the phytoplankton community structure, and development of phytoplankton blooms, would be more constrained by environmental and hydrological conditions than nutrient competition. The high concentration of measured nutrients could be attributed to the concurrence of various non‐point sources. The phytoplankton species richness was high, exhibiting values even higher than those mentioned in previous studies. Considering the two trophic classification systems, and based on total phosphorus data, the reservoir is classified within the hypertrophic category. In contrast, considering only the chlorophyll and turbidity data, the lake would be classified within the eutrophic category.     

Summer phytoplankton nutrient limitation in Maumee Bay of Lake Erie during high-flow and low-flow years

Algal production in Maumee Bay in western Lake Erie is highly affected by inputs of nitrogen (N) and phosphorus (P) from the Maumee River, which drains predominantly agricultural lands, leading to the formation of cyanobacterial blooms. In a 3-year study, precipitation and discharge ranged from relatively low (2012) to relatively high (2011) with corresponding changes in the size of the cyanobacterial bloom. This study aimed to quantify the relation between river discharge and algal nutrient limitation in Maumee Bay. During the summer growing seasons, 20 nutrient enrichment bioassays were performed to determine which nutrient (P or N) might limit phytoplankton growth; and ambient N and P concentrations were monitored. The bioassays suggested that phytoplankton growth shifted from P-limited to N-limited during summer of the low and intermediate discharge years (2012 and 2010, respectively), whereas during the high discharge year (2011) phytoplankton were nutrient-replete before becoming N-limited. Phosphorus-replete growth during the high discharge year likely was due to high P loads from the river and dissolved P concentrations greater than 1 μmol/L. Symptoms of N-limited growth occurred during August and September in all three years and during July of 2012 when NO₃⁻ plus NH₄⁺ concentration was less than 7.29 μmol/L suggesting low or no correspondence between N-limitation and size of the cyanobacterial bloom. Occurrence of a relatively small cyanobacterial bloom in 2012 following the record-breaking bloom in 2011 suggests the possibility of fast-reversal of eutrophication in Maumee Bay if P loading from the watershed could be decreased.     

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.