Biology subjects

Botrel, M.

Publications and source records attributed to Botrel, M..

3 recordsLinked to original sources

bioRxiv2025

Interannual surface water CO2 and O2 dynamics during fall in a small headwater lake

Lake metabolism is often quantified using continuous measures of dissolved oxygen (O2), where a 1: -1 stoichiometry with carbon dioxide (CO2) is assumed because of their roles in photosynthesis and respiration, respectively. However, many other physical, chemical, and biological processes decouple dissolved O2 and CO2 concentrations in lakes. Tracking departures from 1:-1 stoichiometry may provide insights into larger scale ecosystem functioning, particularly during fall when temperatures change and destratification occurs. Using continuous measures of both dissolved O2 and CO2 in a small temperate headwater lake, we looked at the interannual gas departure signals during fall over seven years. The beginning of fall, defined here as the start of leaf colour change, differed among years but coincided well with the onset of lake destratification and a shift in surface gas concentrations. Fall surface CO2 accumulation rates varied considerably, whereas O2 depletion rates were rather similar among years. Departure signals were broadly related to interannual differences in climate: more CO2 accumulated in the surface during the hottest-wettest fall compared to the coldest-driest one (0.81 and 0.37 {micro}mol L-1 d-1, respectively), presumably from more catchment than hypolimnetic inputs. Lower CO2 accumulation occurred during years with prolonged hypolimnetic hypoxia potentially through enhanced CO2 consumption by methanogenesis. Other internal biological phenomena influenced fall departure signals, including a large metalimnetic oxygen peak, and higher fall surface primary production. We suggest gas departures during fall provide an integrative metabolic fingerprint for temperate stratified lakes, as well as insights into winter-priming conditions. HighlightsO_LIAnnual fall surface water CO2 accumulation rates vary more than O2 depletion rates. C_LIO_LIExternal fall inputs and internal processes influence gas departures differently. C_LIO_LIFall gas departures may act as an integrative metabolic signal in temperate lakes. C_LI

ecology↗

bioRxiv2023

A social-ecological geography of southern Canadian Lakes

Anthropogenic pressures, including urban and agricultural expansion, can negatively influence a lakes capacity to provide aquatic ecosystem services (ES). However, identifying lakes most at risk of losing their ES requires integrating information on lake ecological state, global change threats, and ES demand. Here, we provide a social-ecological framework that combines these features within a regional context based on an ecological evaluation of the state of 659 lakes across Canada. From deviation of impacted lakes to reference ones, we identified much higher concentrations of total nitrogen and chloride as the main indicators of altered lake ecological state in all regions identified. Lake ecological state was mapped using an additive colour model along with regional scores of threat levels and recreational ES demand. Population density and agriculture were linked to high lake vulnerability. Lakes in Southern Ontario were most concerning, being highly altered, under threat, and heavily used. Lakes near urban centers along coasts were altered and used, but less threatened, whereas those in the Prairies were altered and threatened, but less used. Our novel framework provides the first social-ecological geography of Canadian lakes, and, is a promising tool to assess lake state and vulnerability at scales relevant for management. Plan language summaryPlain language title: Assessing overall lake health across Canada to identify sites for restoration and conservation Canadians love to swim, fish, and navigate in and on the countless lakes across the country. But Canadian lakes are under a considerable amount of pressure from human activities in their watershed. The expansion of cities, intensive farming, wetland loss, and industrial development all results in the transfer of pollutants to aquatic habitats, threatening the health of lakes and the ecosystem services they provide. Where are lakes being used across Canada? What condition are they in and is their use under threat from different pressures? To answer these questions, we combined information from many different sources, including a national scale lake assessment, through the NSERC Strategic Network Cluster Lake Pulse to create the first social-ecological geography of southern Canadian lakes. Regionally specific baseline conditions were established from lakes considered healthy due to limited human activities in their watershed. When lakes with impacted watershed were compared to healthy ones within their specific region, two early warning signals of human pressure, pollution from nitrogen found in fertilizers and sewage, and chloride found in road salt, determined whether a lake was altered. We combined these two health indicators, with information on future potential lake threats and use by the population for recreational purposes. Using a colour-coded mapping technique, we were able to identify regions where lakes were altered, threatened, and used. These regions occurred primarily around dense urban areas, of southern Ontario and Quebec, and major cities on the east and west coast. Lakes were altered and threatened, but seemingly less used in the Prairie Provinces. The novel approach is very adaptable, easy to understand, and can be used at more regional levels for management to determine priority sites for conservation and restoration, as well as in science communication to describe overall lake health.

ecology↗

bioRxiv2022

Combining quadrat, rake and echosounding to estimate submerged aquatic vegetation biomass at the ecosystem scale

Measuring freshwater submerged aquatic (SAV) biomass at large spatial scales is challenging and no single technique can cost effectively accomplish this while maintaining accuracy. We propose to combine and intercalibrate accurate quadrat-scuba diver technique, fast rake sampling and large scale echosounding. We found that the relationship between quadrat and rake biomass is moderately strong (R2 = 0.62, RMSECV = 2.19 g/m2) and varies with substrate type and SAV growth form. Rake biomass was also successfully estimated from biovolume10 and its error (R2 = 0.53, RMSECV = 5.95 g/m2), a biomass proxy derived from echosounding, at a resolution of 10 m radius from rake sampling point. However, the relationship was affected by SAV growth form, depth, acoustic data quality and wind conditions. Sequential application of calibrations yielded predictions in agreement with quadrat observations, but echosounding predictions underestimated biomass in shallow areas (< 1.5 m) while outperforming point estimation in deep areas (> 3 m). Whole-system biomass was more accurately estimated by calibrated echosounding than rake point surveys, owing to the large sample size and better representation of spatial heterogeneity of echosounding. We recommend developing as a one-time event a series of quadrat and rake calibration equations for each growth form and substrate type. Because the relationship between biovolume and biomass depends on SAV growth form, rake and echosounding calibration needs to be conducted frequently. With the two calibrations, rake can thus be used as a rapid ground truthing or in shallow areas where echosounding is inadequate.

ecology↗