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1. Lakeshore residential development as a driver of aquatic habitat and littoral fish communities: A cross‐system study

   https://doi.org/10.1002/eap.2896  

   Perales, K. Martin ; Vander Zanden, M. Jake ( June 2023 , Ecological Applications)

   Lakeshore riparian habitats have undergone intensive residential development in many parts of the world. Lakeshore residential development (LRD) is associated with aquatic habitat loss/alteration, including altered macrophyte communities and reduced coarse woody habitat. Yet habitat‐mediated and other generalized effects of LRD on lake biotic communities are not well understood. We used two approaches to examine the relationships among LRD, habitat, and fish community in a set of 57 northern Wisconsin lakes. First, we examined how LRD affected aquatic habitat using mixed linear effects models. Second, we evaluated how LRD affected fish abundance and community structure at both whole‐lake and site‐level spatial scales using generalized linear mixed‐effects models. We found that LRD did not have a significant relationship with the total abundance (all species combined) of fish at either scale. However, there were significant species‐specific responses to LRD at the whole‐lake scale. Species abundances varied across the LRD gradient, with bluegill (Lepomis macrochirus) and mimic shiners (Notropis volucellus) responding positively along the gradient and walleye (Sander vitreus) having the most negative response. We also quantified site‐level habitat associations for each fish species. We found that habitat associations did not inform a species' overall response to LRD, as illustrated by species with similar responses to LRD having vastly different habitat associations. Finally, even with the inclusion of littoral habitat information in models, LRD still had significant effects on species abundances, reflecting a role of LRD in shaping littoral fish communities independent of our measure of littoral habitat alteration. Our results indicated that LRD altered littoral fish communities at the whole‐lake scale through both habitat and non‐habitat‐mediated drivers.

    

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2. Landsat-derived bathymetry of lakes on the Arctic Coastal Plain of northern Alaska

   https://doi.org/10.5194/essd-13-1135-2021  

   Simpson, Claire E. ; Arp, Christopher D. ; Sheng, Yongwei ; Carroll, Mark L. ; Jones, Benjamin M. ; Smith, Laurence C. ( January 2021 , Earth System Science Data)

   null (Ed.)

   Abstract. The Pleistocene sand sea on the Arctic Coastal Plain (ACP) ofnorthern Alaska is underlain by an ancient sand dune field, a geologicalfeature that affects regional lake characteristics. Many of these lakes,which cover approximately 20 % of the Pleistocene sand sea, are relativelydeep (up to 25 m). In addition to the natural importance of ACP sand sealakes for water storage, energy balance, and ecological habitat, the needfor winter water for industrial development and exploration activities makeslakes in this region a valuable resource. However, ACP sand sea lakes havereceived little prior study. Here, we collect in situ bathymetric data totest 12 model variants for predicting sand sea lake depth based on analysisof Landsat-8 Operational Land Imager (OLI) images. Lake depth gradients weremeasured at 17 lakes in midsummer 2017 using a Humminbird 798ci HD SI Comboautomatic sonar system. The field-measured data points were compared tored–green–blue (RGB) bands of a Landsat-8 OLI image acquired on 8 August2016 to select and calibrate the most accurate spectral-depth model for eachstudy lake and map bathymetry. Exponential functions using a simple bandratio (with bands selected based on lake turbidity and bed substrate)yielded the most successful model variants. For each lake, the most accuratemodel explained 81.8 % of the variation in depth, on average. Modeled lakebathymetries were integrated with remotely sensed lake surface area toquantify lake water storage volumes, which ranged from 1.056×10-3 to 57.416×10-3 km3. Due to variations in depthmaxima, substrate, and turbidity between lakes, a regional model iscurrently infeasible, rendering necessary the acquisition of additional insitu data with which to develop a regional model solution. Estimating lakewater volumes using remote sensing will facilitate better management ofexpanding development activities and serve as a baseline by which toevaluate future responses to ongoing and rapid climate change in the Arctic.All sonar depth data and modeled lake bathymetry rasters can be freelyaccessed at https://doi.org/10.18739/A2SN01440 (Simpson and Arp, 2018) andhttps://doi.org/10.18739/A2HT2GC6G (Simpson, 2019), respectively. 

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3. Predicting anoxia in low‐nutrient temperate lakes

   https://doi.org/10.1002/eap.2361  

   Deeds, Jeremy ; Amirbahman, Aria ; Norton, Stephen A. ; Suitor, Douglas G. ; Bacon, Linda C. ( June 2021 , Ecological Applications)

   Absence of dissolved oxygen (anoxia) in the hypolimnion of lakes can eliminate habitat for sensitive species and may induce the release of sediment‐bound phosphorus. Lake anoxia generally results from decomposition of organic matter, which is exacerbated by high nutrient loads. Total phosphorus (TP) in lakes is regulated by static aspects of the lake’s watershed, but lake TP can be readily increased by human activities. In some low‐nutrient lakes, basin morphometry may induce naturally occurring anoxia. The occurrence of natural anoxia is especially important to consider in lake water quality assessments that compare observed conditions to expected reference conditions. To investigate the occurrence of natural vs. anthropogenically influenced anoxia, we constructed a logistic regression model to calculate the probability of low‐nutrient lakes (TP < 15 µg/L) developing aerial anoxic extent ≥10% by testing the predictive potential of variables related to basin morphometry, depths of lake thermal strata, epilimnetic TP, and dissolved organic carbon (DOC). Maximum lake depth and the proportion of lake area under the top of the metalimnion were the most important variables to predict the likelihood of hypolimnetic anoxia, which correctly predicted anoxic condition in 84% of lakes (Model 1). Adding TP as a third variable to Model 1 produced a significantly improved model (Model 2) but the prediction success rate was comparable (86%). We also present a model for lakes with limited bathymetric data, which predicts anoxia with 81% accuracy based on maximum lake depth and mean thermocline depth at peak stratification. DOC was relatively low (4.3 ± 1.5 mg/L [mean ± SD]) in the study lakes and its inclusion did not improve model performance. In Model 1, lakes with an anoxic extent ≥10% of lake area had significantly higher epilimnetic TP than lakes with oxic hypolimnia, regardless of prediction category or success. Our results indicate that including TP as a variable helps refine models based on morphometry alone, but lake morphometry and stratification dynamics are the most important factors in the development of anoxic extent in low‐nutrient temperate lakes. Our approach informs studies concerned with identifying key factors that influence regime shifts in a variety of ecosystems.

    

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4. Atmospheric stilling and warming air temperatures drive long‐term changes in lake stratification in a large oligotrophic lake

   https://doi.org/10.1002/lno.11654  

   Stetler, Jonathan T. ; Girdner, Scott ; Mack, Jeremy ; Winslow, Luke A. ; Leach, Taylor H. ; Rose, Kevin C. ( November 2020 , Limnology and Oceanography)

   Lake surface temperatures are warming in many regions and have the potential to alter seasonal thermal stratification. However, the effects of climate change on thermal stratification can be difficult to characterize because trends in thermal stratification can be regulated by changes in multiple climate variables and other characteristics, such as water clarity. Here, we use long‐term (1993–2017) data from near‐pristine Crater Lake (Oregon) to understand long‐term changes in the depth and strength of summer stratification, measured by the center of buoyancy and Schmidt Stability, respectively. The depth of stratification has shoaled significantly (2.4 m decade⁻¹), while stratification strength exhibited no long‐term trend. Empirical observations and modeling scenarios demonstrate that atmospheric stilling at Crater Lake is associated with the 25‐year shoaling trend as spring wind speeds declined over the observation period. While summer lake surface water and air temperatures warmed during the study period, spring air temperatures were variable and correlated with summer Schmidt Stability. Our results indicate that warmer spring air temperature resulted in earlier onset of stratification and stronger summer stratification. The observed shoaling of stratification depth at Crater Lake may have important ecological consequences, especially for non‐motile primary producers who can become constrained within a thinner epilimnion and exposed to higher solar radiation and reduced upwelling of nutrients. Driven by climate changes, many large lakes may be experiencing similar trends in seasonal stratification.

    

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5. Climate‐Driven Changes in Dissolved Organic Carbon and Water Clarity in Arctic Lakes of West Greenland

   https://doi.org/10.1029/2019JG005170  

   Fowler, Rachel A. ; Osburn, Christopher L. ; Saros, Jasmine E. ( February 2020 , Journal of Geophysical Research: Biogeosciences)

   To assess climate‐mediated terrestrial‐aquatic linkages in Arctic lakes and potential impacts on light attenuation and carbon cycling, we evaluated lake responses to climate drivers in two areas of west Greenland with differing climate patterns. We selected four lakes in a warmer, drier area to compare with four lakes from a cooler, wetter area proximal to the Greenland Ice Sheet. In June from 2013–2018, we measured epilimnetic water temperature, 1% depth of photosynthetically active radiation (PAR), dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA₂₅₄), DOC‐normalized absorbance at 380 nm (a*₃₈₀), and chlorophylla. Interannual coherence of 1% PAR and DOC was particularly high for lakes within the warmer, drier area. This coherence suggests forcing of Arctic lake features by a large‐scale driver, likely climate. Redundancy analysis showed that monthly average precipitation, winter North Atlantic Oscillation (NAO) index (NAO_W), spring average air temperature, and spring average precipitation influenced the lake variables (p= 0.003, adj.R²= 0.58). In particular, monthly average precipitation contributed to increases in soil‐derived DOC quality metrics and chlorophyllaand decreased 1% PAR. Interannual changes in lake responses to climate drivers were more apparent in the warmer, drier area than the cooler, wetter area. The interannual lake responses within and between areas, associated with climate trends, suggest that with ongoing rapid climate change in the Arctic, there could be widespread impacts on key lake responses important for light attenuation and carbon cycling.

    

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