Phytoplankton communities in temporary ponds under different climate scenarios

Longer days, larger grays: carryover effects of photoperiod and temperature in gray treefrogs, Hyla versicolor

Environmental conditions like temperature and photoperiod can strongly shape organisms' growth and development. For many ectotherms with complex life cycles, global change will cause their offspring to experience warmer conditions and earlier-season photoperiods, two variables that can induce conflicting responses. We experimentally manipulated photoperiod and temperature during gray treefrog (Hyla versicolor) larval development to examine effects at metamorphosis and during short (10-day) and long (56-day) periods post-metamorphosis. Both early- and late-season photoperiods (April and August) decreased age and size at metamorphosis relative to the average-season (June) photoperiod, while warmer temperatures decreased age but increased size at metamorphosis. Warmer larval temperatures reduced short-term juvenile growth but had no long-term effect. Conversely, photoperiod had no short-term carryover effect, but juveniles from early- and late-season larval photoperiods had lower long-term growth rates than juveniles from the average-season photoperiod. Similar responses to early- and late-season photoperiods may be due to reduced total daylight compared with average-season photoperiods. However, juveniles from late-season photoperiods selected cooler temperatures than early-season juveniles, suggesting that not all effects of photoperiod were due to total light exposure. Our results indicate that despite both temperature and photoperiod affecting metamorphosis, the long-term effects of photoperiod may be much stronger than those of temperature.

How long can tardigrades survive in the anhydrobiotic state? A search for tardigrade anhydrobiosis patterns

Anhydrobiosis is a desiccation tolerance that denotes the ability to survive almost complete dehydration without sustaining damage. The knowledge on the survival capacity of various tardigrade species in anhydrobiosis is still very limited. Our research compares anhydrobiotic capacities of four tardigrade species from different genera, i.e. Echiniscus testudo, Paramacrobiotus experimentalis, Pseudohexapodibius degenerans and Macrobiotus pseudohufelandi, whose feeding behavior and occupied habitats are different. Additionally, in the case of Ech. testudo, we analyzed two populations: one urban and one from a natural habitat. The observed tardigrade species displayed clear differences in their anhydrobiotic capacity, which appear to be determined by the habitat rather than nutritional behavior of species sharing the same habitat type. The results also indicate that the longer the state of anhydrobiosis lasts, the more time the animals need to return to activity.

Phytoplankton community composition, carbon sequestration, and associated regulatory mechanisms in a floodplain lake system

Phytoplankton contribute approximately 50% to the global photosynthetic carbon (C) fixation. However, our understanding of the corresponding C sequestration capacity and driving mechanisms associated with each individual phytoplankton taxonomic group is limited. Particularly in the hydrologically dynamic system with highly complex surface hydrological processes (floodplain lake systems). Through investigating seasonal monitoring data in a typical floodplain lake system and estimation of primary productivity of each phytoplankton taxonomic group individually using novel equations, this study proposed a phytoplankton C fixation model. Results showed that dominant phytoplankton communities had a higher gross carbon sequestration potential (CSP) (9.50 ± 5.06 Gg C each stage) and gross primary productivity (GPP) (65.46 ± 25.32 mg C m^-2 d^-1), but a lower net CSP (-1.04 ± 0.79 Gg C each stage) and net primary productivity (NPP) (-5.62 ± 4.93 mg C m^-3 d^-1) than rare phytoplankton communities in a floodplain lake system. Phytoplanktonic GPP was high (317.94 ± 73.28 mg C m^-2 d^-1) during the rainy season and low (63.02 ± 9.65 mg C m^-2 d^-1) during the dry season. However, their NPP reached the highest during the rising-water stage and the lowest during the receding-water stage. Findings also revealed that during the rainy season, high water levels (p = 0.56**) and temperatures (p = 0.37*) as well as strong solar radiation (p = 0.36*) will increase photosynthesis and accelerate metabolism and respiration of dominant phytoplankton communities, then affect primary productivity and CSP. Additionally, water level fluctuations drive changes in nutrients (p = -0.57*) and metals (p = -0.68*) concentrations, resulting in excessive nutrients and metals slowing down phytoplankton growth and reducing GPP. Compared with the static water lake system, the floodplain lake system with a lower net CSP became a heterotrophic C source.

Chlorophytes response to habitat complexity and human disturbance in the catchment of small and shallow aquatic systems

Human-originated transformation in the catchment area may be reflected in the water quality and ecological state of the aquatic environment. Chlorophytes, the most common and diverse group of microalgae, may be a valuable tool for studies of small water bodies, ecosystems poorly recognized but extremely sensitive to the climate changes. Here we investigated the response of the chlorophytes to abiotic and biotic factors in different habitats and ponds' catchments. Chlorophytes demonstrated a prevalence towards a specific type of catchment area. Field ponds supported chlorophytes typical for nutrient-rich/high-organic and shallow well-mixed waters. Forest ponds supported high chlorophyte diversity. A high importance of desmids, tolerant to light deficiency, confirms their preferences towards lower pH and lower trophic state in the forest ponds. Habitat type strongly impacted the distribution of chlorophytes. Great abundance and fertile-water species were associated with the open water, whereas aquatic plants hosted relatively low chlorophyte abundance which is a derivate of the filtrators grazing as well as the nutrient uptake and shadowing by macrophytes. Macrophyte-dominated zones created favorable conditions for some periphytic desmids and filamentous chlorophytes, species preferring lower trophic state and co-occurring with zooplankton. We assume that cosmopolitan chlorophytes can be adapted for determination of the ecological value of small water bodies, including the level of habitat heterogeneity. But chlorophytes clearly react to the level of human impact in the ponds' catchment, both specific species and functional groups. Thus, we recommend them, particularly desmids, for water quality state assessment in ponds.