Temperature × light interaction and tolerance of high water temperature in the planktonic freshwater flagellates Cryptomonas (Cryptophyceae) and Dinobryon (Chrysophyceae)

Abstract

Using microcosm experiments, we investigated the interactive effects of temperature and light on specific growth rates of three species each of the phytoplanktonic genera Cryptomonas and Dinobryon . Several species of these genera play important roles in the food web of lakes and seem to be sensitive to high water temperature. We measured growth rates at three to four photon flux densities ranging from 10 to 240 μmol photon · m −2 · s −1 and at 4–5 temperatures ranging from 10°C to 28°C. The temperature × light interaction was generally strong, species specific, and also genus specific. Five of the six species studied tolerated 25°C when light availability was high; however, low light reduced tolerance of high temperatures. Growth rates of all six species were unaffected by temperature in the 10°C–15°C range at light levels ≤50 μmol photon · m −2 · s −1 . At high light, growth rates of Cryptomonas spp. increased with temperature until the temperature optimum was reached and then declined. The Dinobryon species were less sensitive than Cryptomonas spp. to photon flux densities of 40 μmol photon · m −2 · s −1 and 200 μmol photon · m −2 · s −1 over the entire temperature range but did not grow under a combination of very low light (10 μmol photon · m −2 · s −1 ) and high temperature (≥20°C). Among the three Cryptomonas species, cell volume declined with temperature and the maximum temperature tolerated was negatively related to cell size. Since Cryptomonas is important food for microzooplankton, these trends may affect the pelagic carbon flow if lake warming continues.

Combined Effects of Temperature, Irradiance, and pH on Teleaulax amphioxeia (Cryptophyceae) Physiology and Feeding Ratio For Its Predator Mesodinium rubrum (Ciliophora)1

“…Interestingly, a significant interaction between the two factors temperature and irradiance was also observed for the maximum growth rate. Generally, the interaction between these two factors results in lmax increasing with temperature under light saturation (Ojala 1993, Edwards et al 2016, Wirth et al 2019. However, our results showed that lmax was strongly affected at temperatures higher than the optimal one when irradiance was high.…”

“…, Wirth et al. ). However, our results showed that μmax was strongly affected at temperatures higher than the optimal one when irradiance was high.…”

Functional Ecology of Two Contrasting Freshwater Ciliated Protists in Relation to Temperature

“…This "thermal safety margin” should allow many species to cope with global warming (Krenek et al 2012). However, in the course of climate change, the UTTL of temperature‐sensitive protist species may constrain their distribution and lead to a shift in the species composition (Montagnes et al 2008; Wirth et al 2019).…”

Reporting of methods for automated devices: A systematic review and recommendation for studies using FlowCam for phytoplankton

“…Readers unfamiliar with the intricacies of the FlowCam are unlikely to understand from the methods presented that most papers do not make use of the widely advertised auto‐classification capabilities of the device. The statement that classifications were conducted “using VisualSpreadsheet software,” employed by many papers (Bergkemper and Weisse 2017; Fileman et al 2017; Wirth et al 2019), is insufficient given that this software can be used solely for processing samples through the FlowCam, for auto‐classifications of images produced by the FlowCam or simply as an image‐viewing interface for manual sorting of images. Furthermore, some papers have provided detailed explanation in their methods section of the creation of image libraries for the apparent purpose of auto‐classification, only to reveal later in the discussion section that the image library was not used or tested in the study (Park et al 2019 a ).…”