A comparison of pre-industrial and present-day changes in Bosmina and Daphnia size structure from soft-water Ontario lakes

2010 ◽  
Vol 67 (4) ◽  
pp. 754-762 ◽  
Author(s):  
Jennifer B. Korosi ◽  
Andrew M. Paterson ◽  
Anna M. DeSellas ◽  
John P. Smol
Keyword(s):  
Body Size ◽  
Size Structure ◽  
South Central ◽  
Zooplankton Size ◽  
Copepod Predation ◽  
Post Impact ◽  
North Temperate Lakes ◽  
Impact Data ◽  
Shield Lakes

Understanding the long-term controls on cladoceran size structure has important implications for aquatic ecosystems. Although there has been considerable interest in zooplankton size trends for Canadian Shield lakes, data are not available for zooplankton size structure prior to the period of anthropogenic disturbances. Here, we present pre- and post-impact size data for the common pelagic cladocerans Bosmina and Daphnia for 44 well-studied Shield lakes in south-central Ontario (Canada). We show that Daphnia were larger and that the length of Bosmina body appendages (mucrones and antennules) was longer in pre-industrial times than they are today. The reduction in Bosmina appendage length we observed may suggest a reduction in copepod predation pressure since pre-industrial times. Reduced maximum body size in Daphnia is a predicted response to a warming climate in north temperate lakes; however, we suggest that alternate explanations, specifically acidification and subsequent recovery following emission reductions, should also be explored as the primary drivers of Daphnia size changes in this lake set. Overall, our results highlight the importance of pre-impact data for understanding the long-term controls on cladoceran body size from pre-1850 to present.

Long-term declines in phosphorus export from forested catchments in south-central Ontario

2009 ◽  
Vol 66 (10) ◽  
pp. 1682-1692 ◽  
Author(s):  
M. Catherine Eimers ◽  
Shaun A. Watmough ◽  
Andrew M. Paterson ◽  
Peter J. Dillon ◽  
Huaxia Yao
Keyword(s):  
Stream Flow ◽  
Seasonal Patterns ◽  
Forested Catchments ◽  
Annual Average ◽  
Temporal And Spatial Patterns ◽  
South Central ◽  
Hydrologic Event ◽  
Temporal And Spatial ◽  
Shield Lakes

Total phosphorus (TP) levels in many Canadian Shield lakes in central Ontario have declined over recent decades, despite increases in human activity in most watersheds. To investigate the contribution of changes in catchment export to long-term declines in lake TP, we examined temporal and spatial patterns in TP concentrations and export (1980–1981 to 2001–2002) across 11 subcatchments that drain into three lakes in which average ice-free TP levels have declined by approximately 35%. Annual stream export of TP decreased significantly by 30%–89% in eight of the 11 subcatchments, and decreases in export were driven by declines in TP concentration, not changes in stream flow. Annual average TP concentrations varied fivefold among adjacent subcatchments, and temporal patterns in annual average TP concentrations were poorly correlated. Seasonal patterns of TP concentration were most similar among streams in the spring (March–April–May), and TP export in the spring declined significantly in 10 of the 11 subcatchments. Because spring melt is the principal hydrologic event in these seasonally snow-covered basins, decreases in TP export during the spring were primarily responsible for declines observed in annual export. The drivers of changes in TP over time are unclear at this point but are the focus of current research.

Evaluation of the responsiveness of the crustacean zooplankton community size spectrum to environmental change and an exotic invader in a sample of Canadian Shield lakes

2020 ◽  
Author(s):  
Lauren Emily Barth ◽  
Brian J. Shuter ◽  
W. Gary Sprules ◽  
Charles K. Minns ◽  
James A Rusak
Keyword(s):  
Time Series ◽  
Environmental Change ◽  
Canadian Shield ◽  
Ecosystem Change ◽  
Crustacean Zooplankton ◽  
Size Spectrum ◽  
Zooplankton Size ◽  
Shield Lakes ◽  
Change In Mean

We evaluated the crustacean zooplankton size spectrum as an indicator of lake characteristics and ecosystem change. First, we used time-series from seven Canadian Shield lakes to identify the factors associated with among-lake and among-year variability in the spectrum slope (relative abundance of small and large zooplankton) and centered height (total abundance). Second, we used time-series from an invaded and three control lakes to assess change in mean and variability in slope and height due to a Bythotrephes invasion. We found that the slope and the height reflected among-lake predictors related to morphometry. The slope was responsive to long-term declining lake phosphorus levels, whereas the height reflected both increases in dissolved organic carbon and decreases in ice duration. We detected a significant increase (i.e. flattening) in mean slope and substantial (up to 120%) increases in the CV of height after Bythotrephes invaded Harp Lake. Thus, the zooplankton size spectrum was responsive to long-term environmental change and a strong top-down perturbation can be detected through regular and frequent monitoring programs.

Interannual variability and species turnover of crustacean zooplankton in Shield lakes

1999 ◽  
Vol 56 (1) ◽  
pp. 162-172 ◽  
Author(s):  
Shelley E Arnott ◽  
Norman D Yan ◽  
John J Magnuson ◽  
Thomas M Frost
Keyword(s):  
Sampling Error ◽  
Species Turnover ◽  
Crustacean Zooplankton ◽  
Annual Data ◽  
Turnover Rates ◽  
High Turnover ◽  
South Central ◽  
Census Interval ◽  
Shield Lakes

We estimated apparent species turnover rates and richness of the zooplankton annually over a 12-year period in eight lakes in south-central Ontario. Although species richness varied little among years (CV = 13%), apparent species turnover rates averaged 16%/year. This apparent turnover varied among years and was influenced by census interval, the number of censuses, the occurrence of rare species, and lake pH. However, Monte Carlo simulations indicated that turnover attributable to sampling error was high. That is, despite high apparent turnover rates, we cannot be certain whether interannual changes in community composition result from immigration and extinction of species because sampling error could largely account for all apparent turnover. Regardless of the source of apparent turnover (sampling or immigrations and extinctions), high turnover rates imply that zooplankton biodiversity can be underestimated in short-term studies because we detect a different assemblage of species every year. Only one third of the total species pool for each lake was detected every year. Annual data underestimated long-term species pools by 33-50%.

scholarly journals Response of Zooplankton Size Structure to Multiple Stressors in Urban Lakes

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2305
Author(s):  
Reliana Lumban Toruan ◽  
Liah X. Coggins ◽  
Anas Ghadouani
Keyword(s):  
Body Size ◽  
Environmental Variables ◽  
Size Structure ◽  
Negative Slope ◽  
Total Biomass ◽  
Size Spectra ◽  
Urban Lakes ◽  
Chl A ◽  
Zooplankton Size ◽  
Density And Biomass

Urban lakes are important environmental assets that contribute significant ecosystem services in urbanised areas around the world. Consequently, urban lakes are more exposed to anthropogenic pressures. Zooplankton communities play a central role in lake processes and, as such, are very sensitive to the impacts of human activities both through in-lake and catchment processes. Understanding their ecological function in urban lakes and how they respond to urbanisation is essential for environmental sustainability. In this study, we investigated the reliability of zooplankton size structure as indicators of anthropogenic stressors in urban lakes. We examined the relationship between environmental variables and zooplankton community size spectra derived as mean body size, density, and biomass. Our study showed that the overall mean body size was within the small size group ranged from 416 to 735 µm equivalent spherical diameter (ESD). Despite no significant difference in total zooplankton density between lakes, there was variability in the total density of the five different size classes. Total biomass was characterised by a significant proportion of size >750 µm. As the specific parameter of normalised biomass size spectra (NBSS), the slopes of the NBSS varied from moderate (−0.83 to −1.04) for a community with higher biomass of the larger size zooplankton to steeper slopes (from −1.15 to −1.49) for a community with higher biomass of smaller size. The environmental variables, represented by total phosphorus (TP) and chlorophyll a (chl-a), had a strong effect on zooplankton biomass and NBSS, where TP and chl-a were significantly correlated with the increase of total biomass and corresponded well with a less negative slope. Our results indicated that the community metric was sensitive to nutrient input and that size-based metrics have the potential to serve as key indicators for the management of urban lakes.

Quantitative inferences of past hypolimnetic anoxia in south-central Ontario lakes using fossil midges (Diptera: Chironomidae)

1998 ◽  
Vol 55 (3) ◽  
pp. 587-596 ◽  
Author(s):  
Roberto Quinlan ◽  
John P Smol ◽  
Roland I Hall
Keyword(s):  
Weighted Averaging ◽  
Species Variation ◽  
Calibration Model ◽  
Forward Selection ◽  
Lake Ecosystems ◽  
South Central ◽  
Hypolimnetic Oxygen ◽  
Chironomid Assemblages ◽  
Shield Lakes

The ability to infer long-term changes in hypolimnetic oxygen levels is important for ecological studies of eutrophication and the impacts of climatic change on freshwater lakes. We examined the distributions of fossil midge (Diptera: Chironomidae) assemblages in the surface sediments of 54 south-central Ontario lakes and, using canonical correspondence analysis (CCA), determined if fossil chironomid assemblages could be used to reconstruct levels of hypolimnetic anoxia in thermally stratifying Laurentian Shield lakes. Anoxia was expressed as the anoxic factor (AF), which represents the days per season that a sediment area equal to a lake's surface area is overlain by anoxic water. Forward selection in CCA showed that AF, maximum depth, [SO4], [Na], and watershed area all explained significant portions of species variation. A weighted-averaging regression and calibration model of the chironomid-anoxia relationship was developed which suggests that it is possible to infer AF from fossil chironomid assemblages ( (r2appar ) = 0.70, bootstrapped RMSE = 6.5 days/summer). Quantitative reconstruction of past changes in anoxia using fossil Chironomidae should provide a new and useful tool for paleoecological assessments of lake ecosystems.

Long-term trends in hypolimnetic volumes and dissolved oxygen concentrations in Boreal Shield lakes of south-central Ontario, Canada

2019 ◽  
Vol 76 (12) ◽  
pp. 2315-2325 ◽  
Author(s):  
Clare Nelligan ◽  
Adam Jeziorski ◽  
Kathleen M. Rühland ◽  
Andrew M. Paterson ◽  
John P. Smol
Keyword(s):  
Dissolved Oxygen ◽  
Climatic Factors ◽  
Thermocline Depth ◽  
South Central ◽  
Air Temperatures ◽  
Hypolimnetic Oxygen ◽  
Long Term Trends ◽  
Shield Lakes ◽  
Carbon Concentrations

Temperature–oxygen profiles, collected biweekly to monthly for ∼40 years, were used to calculate end-of-summer volume-weighted hypolimnetic oxygen (VWHO) concentrations in six small lakes located in south-central Ontario, Canada. Coherent decreases in thermocline depth and increases in hypolimnetic volume, mean hypolimnetic dissolved oxygen (DO) concentration, and VWHO were observed in five of the six study lakes. All lakes underwent an abrupt increase in VWHO and mean hypolimnetic DO after 2010. In four of the six study lakes, the highest hypolimnetic DO concentrations were observed in years where chlorophyll a concentrations were low, whereas at five of the six study lakes the highest hypolimnetic volumes were observed when dissolved organic carbon concentrations were relatively high. Warmer spring or winter air temperatures were associated with higher hypolimnetic DO concentrations at two sites, and longer ice-free periods were associated with smaller hypolimnetic volumes at two sites. These results suggest that the recent VWHO increases in the studied south-central Ontario lakes may be a function of multiple drivers that include changes in primary production, lake water transparency, and regional climatic factors.

scholarly journals Individual differences determine the strength of ecological interactions

2020 ◽  
Vol 117 (29) ◽  
pp. 17068-17073 ◽  
Author(s):  
Jason I. Griffiths ◽  
Dylan Z. Childs ◽  
Ronald D. Bassar ◽  
Tim Coulson ◽  
David N. Reznick ◽  
...  
Keyword(s):  
Body Size ◽  
Evolutionary Dynamics ◽  
Size Structure ◽  
Empirical Studies ◽  
Biotic Interactions ◽  
Ecological Interactions ◽  
Intraspecific Interactions ◽  
Different Populations ◽  
The Impact

Biotic interactions are central to both ecological and evolutionary dynamics. In the vast majority of empirical studies, the strength of intraspecific interactions is estimated by using simple measures of population size. Biologists have long known that these are crude metrics, with experiments and theory suggesting that interactions between individuals should depend on traits, such as body size. Despite this, it has been difficult to estimate the impact of traits on competitive ability from ecological field data, and this explains why the strength of biotic interactions has empirically been treated in a simplistic manner. Using long-term observational data from four different populations, we show that large Trinidadian guppies impose a significantly larger competitive pressure on conspecifics than individuals that are smaller; in other words, competition is asymmetric. When we incorporate this asymmetry into integral projection models, the predicted size structure is much closer to what we see in the field compared with models where competition is independent of body size. This difference in size structure translates into a twofold difference in reproductive output. This demonstrates how the nature of ecological interactions drives the size structure, which, in turn, will have important implications for both the ecological and evolutionary dynamics.

Use of Zooplankton to Assess the Movement and Distribution of Alewife (Alosa pseudoharengus) in South-Central Lake Ontario in Spring

1991 ◽  
Vol 48 (11) ◽  
pp. 2250-2257 ◽  
Author(s):  
Robert O'Gorman ◽  
Edward L. Mills ◽  
Joe DeGisi
Keyword(s):  
Water Temperature ◽  
Size Structure ◽  
Lake Ontario ◽  
Crustacean Zooplankton ◽  
Alosa Pseudoharengus ◽  
Freshwater Lakes ◽  
South Central ◽  
Zooplankton Size ◽  
The Mean ◽  
Change In Mean

Data from assessments of fish and zooplankton conducted during April and May–June 1986–88 in south-central Lake Ontario were examined for evidence that zooplankton size structure can be used to follow the movement of alewife (Alosa pseudoharengus). The spring influx of alewife into nearshore waters was linked with water temperature and coincided with a decline in the mean length of crustacean zooplankton and the virtual disappearance of zooplankters [Formula: see text]. Alewife moving inshore to spawn fed heavily on the largest zooplankters, negating the possibility that changes in zooplankton size were wholly a response to seasonal recruitment as waters warm and the composition shifts to Bosmina. Offshore, there was usually no significant (P < 0.05) change in mean lengths of zooplankton in the upper water column between April and May–june, and zooplankters [Formula: see text] always remained abundant, suggesting that few alewife were there from April through mid-june. We conclude that in large freshwater lakes where a planktivore is abundant, yet spatially concentrated, changes in size of crustacean zooplankton can facilitate understanding of the fish's movement and distribution.

scholarly journals Cautions on using the Before-After-Control-Impact design in environmental effects monitoring programs

FACETS ◽  
2017 ◽  
Vol 2 (1) ◽  
pp. 212-232 ◽  
Author(s):  
K.E. Smokorowski ◽  
R.G. Randall
Keyword(s):  
Environmental Impact ◽  
Environmental Effects ◽  
Baci Design ◽  
Impact Monitoring ◽  
Monitoring Programs ◽  
Post Impact ◽  
Impact Data ◽  
The Impact ◽  
Environmental Effects Monitoring

Often the Before-After-Control-Impact (BACI) design is suggested as being a statistically powerful experimental design in environmental impact studies. If the timing and location of the impact are known and adequate pre-data are collected, the BACI design is considered optimal to help isolate the effect of the development from natural variability. This paper presents 9 years of results from a long-term BACI experiment tested using a range of statistical models and post-impact monitoring designs. To explore suboptimal designs that are often utilized in environmental effects monitoring, the same data were also explored assuming either no control system was available (Before-After only), or that no pre-impact data were available (Control-Impact only). The results of the BACI design were robust to the statistical model used, and the BACI design was able to detect effects from the impact that the two suboptimal designs failed to detect. However, the BACI design demonstrated different conclusions depending on the number and configuration of post-impact years included in the analysis. Our results reinforce the idea that caution should be employed when using, or interpreting results from, a BACI design in an environmental impact study, but demonstrate that a well-designed BACI remains one of the best models for environmental effects monitoring programs.

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

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