Status of the Lake Ontario Food Web in a Changing Ecosystem: the 2003 Lake Ontario Lower Aquatic Food Web Assessment (LOLA)

Understanding stressor impacts on ecological processes in Lake Ontario over the last three decades has resulted from a commitment to long-term binational studies by environmental agencies and their dedicated scientists and support staffs in both Canada and the United States. LOLA was initiated at the request of the United States and Canada Lake Ontario Lakewide Management Plan (LaMP) and the Great Lakes Fishery Commission’s Lake Ontario Committee with the following two goals: 1) assess the status of and 2) develop recommendations for the long-term comprehensive assessment of the Lake Ontario lower aquatic food web. The 2003 LOLA project incorporated seasonal sampling at a large spatial scale, providing the most comprehensive assessment of the status of Lake Ontario’s lower food web since the Lake Ontario Trophic Transfer Program in 1995. Partners from seven government agencies and six universities and colleges participated in the LOLA project. A workshop attended by LaMP representatives, government agencies, and academics was held at Cornell University on November 16-17, 2005. Discussions based on significant findings that were presented at the workshop resulted in seven recommendations for future assessment of the Lake Ontario lower aquatic food web

Maturation Schedules of Walleye Populations in the Great Lakes Region: Comparison of Maturation Indices and Evaluation of Samplingâ Induced Biases

Maturation schedules, key determinants of fish stocks’ harvest potential and population dynamics, are influenced by both plastic and adaptive processes. Various indices are used to describe maturation schedules, and these have differential advantages for discriminating between plastic and adaptive processes. However, potential samplingâ related biases associated with different maturation indices have not been fully evaluated. We analyzed three maturation indices for walleyes Sander vitreus in Lake Erie; Saginaw Bay, Lake Huron; and Oneida Lake, New York: age and length at 50% maturity, midpoint of ageâ specific maturity ogives (ageâ specific length at which probability of maturity = 0.50), and midpoints of probabilistic maturation reaction norms (PMRNs; ageâ specific length at which probability of maturing in the following year = 0.50). We then compared estimated maturation indices to evaluate sensitivity of different maturation indices to samplingâ induced biases and to assess the relative importance of plastic versus adaptive processes in structuring interstock and temporal variation in maturation schedules. Our findings suggest that although small changes in sampling month, gear, and agencyâ related effects can bias estimates of age and length at 50% maturity and midpoints of maturity ogives, PMRN estimates appear to be robust to these biases. Furthermore, PMRN estimates are suggestive of potential adaptive variation in maturation schedules among walleye stocks and over time. For instance, Oneida Lake walleyes (which had relatively slow growth and low mortality rates) matured at a smaller size for a given age (smaller midpoints of PMRNs) than the other stocks. Temporally, walleyes in the western basin of Lake Erie matured at a larger size in recent years, as evidenced by increasing midpoints of PMRNs (1978â 1989 versus 1990â 2006 for Ohio Department of Natural Resources data and 1990â 1996 versus 1997â 2006 for Ontario Ministry of Natural Resources data). Our study highlights the necessity of monitoring maturation schedules via multiple maturation indices and the need to account for samplingâ induced biases when comparing maturation schedules.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141201/1/nafm1540.pd

The golden apple snail Pomacea canaliculata shifts primary production from benthic to pelagic habitats in simulated shallow lake systems

Biological invasions are among the most serious threats to ecosystems. The golden apple snail Pomacea canaliculata (Lamarck, 1822) is considered one of the top 100 worst invasive alien species in the world. These snails consume benthic primary producers, including submerged macrophytes, which may lead to an increase in nutrient concentration in the water, enhance growth of phytoplankton, and decrease growth of macrophytes, thereby shifting the primary production from benthic to pelagic habitats in shallow systems. To test this hypothesis, we conducted a short-term experiment with and without the invasive P. canaliculata in mesocosms with high abundance of the native submerged macrophyte Vallisneria natans (Lour.) Hara. Compared with snail-free control, the snail increased the concentrations of total nitrogen (TN), nitrate nitrogen (NO3-N), total and organic suspended solids (TSS and OSS), decreased the concentrations of soluble reactive phosphorous (SRP), but had no effect on total phosphorus (TP) and the TN:TP ratio. In addition, the snails decreased the biomass, leaf length and tiller number of V. natans, and decreased light intensity. Although snail presence did not change the biomasses of nanophytoplankton and picophytoplankton, it did increase the biomass of microphytoplankton leading to an increase in total phytoplankton biomass. Our study shows that P. canaliculata shifted primary production from benthic to pelagic habitats, altered the phytoplankton community size structure, and decreased water quality. The results add further evidence of negative ecosystem impacts of this invasive apple snail and call for its control in invaded shallow lake ecosystems

Effects of common carp (Cyprinus carpio) on water quality in aquatic ecosystems dominated by submerged plants: a mesocosm study

Common carp (Cyprinus carpio) have been introduced into aquatic systems across the world, where their benthivorous feeding behavior has resulted in serious water quality problems. A 12-week mesocosm experiment was set up to test the hypotheses that common carp increase water column nutrient levels and decrease water clarity in aquatic ecosystems dominated by submerged plants. Further, we tested whether the effect of common carp on macrophytes depended on the species of plants. Relative to the controls, the presence of carp decreased water clarity by increasing total suspended solids (TSS) and light attenuation. However, levels of total nitrogen (TN) and total phosphorus (TP) in the water column were reduced. No significant change in phytoplankton biomass (measured as chlorophyll a) and the biomass of Hydrilla verticillata was observed between common carp treatment mesocosms and controls, but the common carp did reduce the biomass of the submerged macrophyte Vallisneria denseserrulata. We conclude that removal of common carp is likely to improve water clarity in aquatic ecosystems dominated by submerged plants primarily by decreasing TSS and that the effect of common carp on macrophytes is stronger for the meadow forming Vallisneria than for the canopy forming Hydrilla

2010 Status of the Lake Ontario Lower Trophic Levels

This report presents data on the status of lower trophic level components of the Lake Ontario ecosystem (zooplankton, phytoplankton, nutrients) in 2010 and compares the 2010 data with available time series. Lower trophic levels are indicators of ecosystem health [as identified by the Lake Ontario Pelagic Community Health Indicator Committee (EPA 1993) and presented in the biennial State of the Lake Ecosystem Conference (SOLEC) reports] and determine the lake’s ability to support the prey fish upon which both wild and stocked salmonids depend. Understanding the production potential of lower trophic levels is also integral to ecosystem-based management. Continued evaluation of lower trophic levels is particularly important for fisheries management, as the observed declines in alewife and Chinook salmon in Lake Huron in 2003 may have been partly the result of changes in lower trophic levels (Barbiero et al. 2009)

Density data for Lake Ontario benthic invertebrate assemblages from 1964 to 2018

Benthic invertebrates are important trophic links in aquatic food webs and serve as useful bioindicators of environmental conditions because their responses integrate the effects of both water and sediment qualities. However, long-term data sets for benthic invertebrate assemblages across broad geographic areas are rare and, even if collected, historic data sets are often not readily accessible. This data set provides densities of benthic macroinvertebrates for all taxa collected during lake-wide surveys in Lake Ontario, a Laurentian Great Lake, from 1964 to 2018. This information resulted from surveys funded by the governments of the United States and Canada to investigate the status and changes of Lake Ontario benthic community. Of the 13 lake-wide benthic surveys conducted in Lake Ontario over the course of 54 yr, we were able to acquire taxonomic data to the species level for 11 of the surveys and data to the group level for the other two surveys. Density data are provided for taxa representing the Annelida, Arthropoda, Mollusca, Cnidaria, Nemertea, and Platyhelminthes phyla. Univariate and multivariate analyses revealed that the compositional structure of Lake Ontario invertebrate assemblages differed markedly by depth and were also significantly altered by the Dreissena spp. invasion in early 1990s. The introduction of invasive dreissenids has changed the community historically dominated by Diporeia, Oligochaeta, and Sphaeriidae, to a community dominated by quagga mussels and Oligochaeta. Considering the rarity of long-term benthic data of high taxonomic resolution in lake ecosystems, this data set could be useful to explore broader aspects of ecological theory, including effects of different environmental factors and invasive species on community organization, functional and phylogenetic diversity, and spatial scale of variation in community structure. The data set could also be useful for studies on individual species including abundance and distribution, species co-occurrence, and how the patterns of dominance and rarity change over space and time. Use of this data set for academic or educational purposes is encouraged as long as the data source is properly cited using the title of this Data Paper, the names of the authors, the year of publication, the journal name, and the article number

The extent and variability of storm-induced temperature changes in lakes measured with long-term and high-frequency data

The intensity and frequency of storms are projected to increase in many regions of the world because of climate change. Storms can alter environmental conditions in many ecosystems. In lakes and reservoirs, storms can reduce epilimnetic temperatures from wind-induced mixing with colder hypolimnetic waters, direct precipitation to the lake's surface, and watershed runoff. We analyzed 18 long-term and high-frequency lake datasets from 11 countries to assess the magnitude of wind- vs. rainstorm-induced changes in epilimnetic temperature. We found small day-to-day epilimnetic temperature decreases in response to strong wind and heavy rain during stratified conditions. Day-to-day epilimnetic temperature decreased, on average, by 0.28 degrees C during the strongest windstorms (storm mean daily wind speed among lakes: 6.7 +/- 2.7 m s(-1), 1 SD) and by 0.15 degrees C after the heaviest rainstorms (storm mean daily rainfall: 21.3 +/- 9.0 mm). The largest decreases in epilimnetic temperature were observed >= 2 d after sustained strong wind or heavy rain (top 5(th) percentile of wind and rain events for each lake) in shallow and medium-depth lakes. The smallest decreases occurred in deep lakes. Epilimnetic temperature change from windstorms, but not rainstorms, was negatively correlated with maximum lake depth. However, even the largest storm-induced mean epilimnetic temperature decreases were typicallyPeer reviewe

Scientists’ Warning to Humanity: Rapid degradation of the world\u27s large lakes

Large lakes of the world are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. They are also sentinels of global and local change, and recent studies in limnology and paleolimnology have demonstrated disturbing evidence of their collective degradation in terms of depletion of resources (water and food), rapid warming and loss of ice, destruction of habitats and ecosystems, loss of species, and accelerating pollution. Large lakes are particularly exposed to anthropogenic and climatic stressors. The Second Warning to Humanity provides a framework to assess the dangers now threatening the world\u27s large lake ecosystems and to evaluate pathways of sustainable development that are more respectful of their ongoing provision of services. Here we review current and emerging threats to the large lakes of the world, including iconic examples of lake management failures and successes, from which we identify priorities and approaches for future conservation efforts. The review underscores the extent of lake resource degradation, which is a result of cumulative perturbation through time by long-term human impacts combined with other emerging stressors. Decades of degradation of large lakes have resulted in major challenges for restoration and management and a legacy of ecological and economic costs for future generations. Large lakes will require more intense conservation efforts in a warmer, increasingly populated world to achieve sustainable, high-quality waters. This Warning to Humanity is also an opportunity to highlight the value of a long-term lake observatory network to monitor and report on environmental changes in large lake ecosystems

Storm impacts on phytoplankton community dynamics in lakes

In many regions across the globe, extreme weather events, such as storms, have increased in frequency, intensity and duration. Ecological theory predicts that such extreme events should have large impacts on ecosystem structure and function. For lake ecosystems, high winds and rainfall associated with storms are linked by short term runoff events from catchments and physical mixing of the water column. Although we have a well-developed understanding of how such wind and precipitation events alter lake physical processes, our mechanistic understanding of how these short-term disturbances 48 translate from physical forcing to changes in phytoplankton communities is poor. Here, we provide a conceptual model that identifies how key storm features (i.e., the frequency, intensity, and duration of wind and precipitation) interact with attributes of lakes and their watersheds to generate changes in a lake’s physical and chemical environment and subsequently phytoplankton community structure and dynamics. We summarize the current understanding of storm-phytoplankton dynamics, identify knowledge gaps with a systematic review of the literature, and suggest future research directions by generating testable hypotheses across a global gradient of lake types and environmental conditions.Fil: Stockwell, Jason D.. University of Vermont; Estados UnidosFil: Adrian, Rita. Leibniz Institute of Freshwater Ecology and Inland Fisheries; AlemaniaFil: Andersen, Mikkel. Dundalk Institute of Technology; IrlandaFil: Anneville, Orlane. Institut National de la Recherche Agronomique; FranciaFil: Bhattacharya, Ruchi. University of Missouri; Estados UnidosFil: Burns, Wilton G.. University of Vermont; Estados UnidosFil: Carey, Cayelan C.. Virginia Tech University; Estados UnidosFil: Carvalho, Laurence. Freshwater Restoration & Sustainability Group; Reino UnidoFil: Chang, ChunWei. National Taiwan University; República de ChinaFil: De Senerpont Domis, Lisette N.. Netherlands Institute of Ecology; Países BajosFil: Doubek, Jonathan P.. University of Vermont; Estados UnidosFil: Dur, Gaël. Shizuoka University; JapónFil: Frassl, Marieke A.. Griffith University; AustraliaFil: Gessner, Mark O.. Leibniz Institute of Freshwater Ecology and Inland Fisheries; AlemaniaFil: Hejzlar, Josef. Biology Centre of the Czech Academy of Sciences; República ChecaFil: Ibelings, Bas W.. University of Geneva; SuizaFil: Janatian, Nasim. Estonian University of Life Sciences; EstoniaFil: Kpodonu, Alfred T. N. K.. City University of New York; Estados UnidosFil: Lajeunesse, Marc J.. University of South Florida; Estados UnidosFil: Lewandowska, Aleksandra M.. Tvarminne Zoological Station; FinlandiaFil: Llames, Maria Eugenia del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Matsuzaki, Shin-ichiro S.. National Institute for Environmental Studies; JapónFil: Nodine, Emily R.. Rollins College; Estados UnidosFil: Nõges, Peeter. Estonian University of Life Sciences; EstoniaFil: Park, Ho-Dong. Shinshu University; JapónFil: Patil, Vijay P.. US Geological Survey; Estados UnidosFil: Pomati, Francesco. Swiss Federal Institute of Water Science and Technology; SuizaFil: Rimmer, Alon. Kinneret Limnological Laboratory; IsraelFil: Rinke, Karsten. Helmholtz-Centre for Environmental Research; AlemaniaFil: Rudstam, Lars G.. Cornell University; Estados UnidosFil: Rusak, James A.. Ontario Ministry of the Environment and Climate Change; CanadáFil: Salmaso, Nico. Research and Innovation Centre - Fondazione Mach; ItaliaFil: Schmitt, François. Laboratoire d’Océanologie et de Géosciences; FranciaFil: Seltmann, Christian T.. Dundalk Institute of Technology; IrlandaFil: Souissi, Sami. Universite Lille; FranciaFil: Straile, Dietmar. University of Konstanz; AlemaniaFil: Thackeray, Stephen J.. Lancaster Environment Centre; Reino UnidoFil: Thiery, Wim. Vrije Unviversiteit Brussel; Bélgica. Institute for Atmospheric and Climate Science; SuizaFil: Urrutia Cordero, Pablo. Uppsala University; SueciaFil: Venail, Patrick. Universidad de Ginebra; SuizaFil: Verburg, Piet. 8National Institute of Water and Atmospheric Research; Nueva ZelandaFil: Williamson, Tanner J.. Miami University; Estados UnidosFil: Wilson, Harriet L.. Dundalk Institute of Technology; IrlandaFil: Zohary, Tamar. Israel Oceanographic & Limnological Research; IsraelGLEON 20: All Hands' MeetingRottnest IslandAustraliaUniversity of Western AustraliaUniversity of AdelaideGlobal Lake Ecological Observatory Networ

Storm impacts on phytoplankton community dynamics in lakes

In many regions across the globe, extreme weather events such as storms have increased in frequency, intensity, and duration due to climate change. Ecological theory predicts that such extreme events should have large impacts on ecosystem structure and function. High winds and precipitation associated with storms can affect lakes via short-term runoff events from watersheds and physical mixing of the water column. In addition, lakes connected to rivers and streams will also experience flushing due to high flow rates. Although we have a well-developed understanding of how wind and precipitation events can alter lake physical processes and some aspects of biogeochemical cycling, our mechanistic understanding of the emergent responses of phytoplankton communities is poor. Here we provide a comprehensive synthesis that identifies how storms interact with lake and watershed attributes and their antecedent conditions to generate changes in lake physical and chemical environments. Such changes can restructure phytoplankton communities and their dynamics, as well as result in altered ecological function (e.g., carbon, nutrient and energy cycling) in the short- and long-term. We summarize the current understanding of storm-induced phytoplankton dynamics, identify knowledge gaps with a systematic review of the literature, and suggest future research directions across a gradient of lake types and environmental conditions.Peer reviewe