Hydrobiologia

Hata, Hiroki; Ogasawara, Kota; Yamashita, Naoki

doi: 10.1007/s10750-022-04852-6pmid: N/A

Environmental DNA (eDNA) is useful to detect the presence of aquatic organisms from water samples, especially for rare and cryptic species. Two freshwater unionid mussels¸ Pronodularia japanensis and Nodularia douglasiae, have rapidly declined over the last three decades and are now threatened with extinction on the Matsuyama Plain, south-western Japan. We designed a species-specific eDNA marker targeting the COI region of P. japanensis. The distribution of this species in the Kunichi River system on the Matsuyama Plain was investigated using both quantitative PCR with this eDNA marker and conventional surveying. We show that the distribution area of P. japanensis did not change between 2013–2014 and 2020–2021, but its density decreased by 99%. eDNA of P. japanensis was detected, with 100% success, from sites where this species was collected by hand. Furthermore, eDNA was detected at nine sites where P. japanensis was not collected but was expected to occur. This study has established a species-specific eDNA marker targeting the COI region of P. japanensis, and this eDNA marker has been validated as effective for surveying the distribution of this species. Using this eDNA marker, extensive investigation of remaining populations and the monitoring of them should improve conservation practices.

Krztoń, Wojciech; Kosiba, Joanna; Wilk-Woźniak, Elżbieta

doi: 10.1007/s10750-022-04863-3pmid: N/A

Freshwater phytoplankton and zooplankton are complex and diverse communities which greatly contribute to the functioning of freshwater ecosystems, constituting a path of nutrient cycling. The relationships of these communities are often driven by species’ functional traits, such as defensive features and grazing adaptations. The aim of the present work was to study if the functional traits of phytoplankton (primary producers) promote specific traits of zooplankton (consumers). We calculated community weighted mean (CWM) of a trait of phytoplankton and zooplankton communities and constructed decision trees to study the relationships between the functional traits of both communities. We found that specific functional traits of zooplankton were most significantly promoted by size and shape of algal particles, followed by potential toxicity and spines possession, which had limited, however still important effects. Armor possession and motility of algae were found not to be promoting any functional traits of zooplankton. Easy-to-handle algal particles promoted greater variability of zooplankton’s functional traits, while large, hard to manage algal particles (often characteristic for cyanobacteria) promoted zooplankton taxa bearing more specialized functional traits. Our study shows that phytoplankton functional traits can be considered as a biotic filter, leading to the selection of advantageous functional traits among zooplankton community.

Kelso, Julia E.; Baker, Michelle A.

doi: 10.1007/s10750-022-04884-ypmid: N/A

As human-dominated landscapes have expanded, the diversity of organic matter (OM) sources to rivers has increased, and knowledge of the composition and quality of these sources is lacking. It is important to characterize novel forms of OM that can affect retention, transport, and transformation of OM within watersheds. We collected fine particulate OM (FPOM) and dissolved OM (DOM) in four watersheds of Northeast Utah with a mixture of urban, forest, and agricultural land cover. We used the natural abundance of 13C, 15N, and 2H isotopes in mixing models to quantify the proportion of terrestrial, autochthonous, and anthropogenic OM. We also used spectroscopic properties of DOM to characterize OM composition. Percent land cover within a watershed did not account for the anthropogenic influence of wastewater treatment plants (WWTP) or grazing and recreation activities. OM was primarily derived from terrestrial sources, except at sites influenced by wastewater, and autochthonous sources at sites influenced by grazing and recreation activities. Sites influenced by WWTPs had more homogenous DOM that was consistently composed of 35% protein-like DOM, while all other sites had greater variability in DOM composition. Further study is needed to understand landscape drivers of DOM composition in watersheds with WWTPs, and such studies should incorporate samples directly from of WWTP effluent.

Sweeney, Kathryn; Rollwagen-Bollens, Gretchen; Hampton, Stephanie E.

doi: 10.1007/s10750-022-04885-xpmid: N/A

Grazing by microzooplankton has been shown to significantly impact freshwater cyanobacteria blooms; however, the contribution of rotifers to the overall effect of microzooplankton grazing is not well understood. We conducted monthly microzooplankton community grazing (dilution) experiments June–October 2019, concurrent with incubations of field-collected rotifers feeding upon the natural assemblage of microplankton prey < 75 µm in Vancouver Lake (Washington State, USA), a lake annually affected by cyanobacteria blooms. Our results showed that just days after a large bloom, the microzooplankton community grazing impact on phytoplankton biomass was exceptionally high (> 1000% d−1), yet the impact by rotifers was low (< 1% d−1). As the bloom diminished in September and October, the grazing impact of rotifers increased dramatically, specifically consuming substantial dinoflagellate (≤ 574%) and ciliate (≤ 382%) biomass daily. Analysis of rotifers in Vancouver Lake during these months showed the presence of large, carnivorous Asplanchna spp., which indicates multi-trophic grazing dynamics within the rotifer assemblage. We conclude that non-rotifer micro-grazers (i.e., ciliates) were likely responsible for the initial dissipation of cyanobacteria just after the bloom peak, while rotifers primarily removed micro-grazers later in autumn. This study highlights the trophic roles of micro-grazers in controlling harmful cyanobacteria blooms and quantifies the specific grazing contributions of rotifers.

Edlund, Mark B.; Ramstack Hobbs, Joy M.; Heathcote, Adam J.; Engstrom, Daniel R.; Saros, Jasmine E.; Strock, Kristin E.; Hobbs, William O.; Andresen, Norman A.; VanderMeulen, David D.

doi: 10.1007/s10750-022-04887-9pmid: N/A

Evidence suggests that boreal-lake ecosystems are changing rapidly, but with variable ecological responses, due to climate warming. Paleolimnological analysis of 27 undeveloped northern forested lakes showed significant and potentially climate-mediated shifts in diatom communities and increased carbon and biogenic silica burial. We hypothesize the sensitivity of northern forested lakes to climate change will vary along two physical gradients: one reflecting direct, in-lake climate effects (propensity to thermally stratify), the other reflecting indirect watershed effects (watershed to lake-surface area ratio). We focus on the historical response of algal communities to test our two-dimensional sensitivity framework. Historical algal response was summarized by measures of diatom community turnover, changes in species and diagnostic species groups, and measures of siliceous algal and overall primary production (biogenic silica, carbon burial). Measures of algal production increased across all lake types, with carbon burial proportionately higher in polymictic lakes. Greater diatom community change occurred in deep, stratified lakes with smaller watersheds, whereas diatom species groups showed variable responses along our two-dimensional sensitivity framework. Physical characteristics of lakes and watersheds could serve as predictors of sensitivity to climate change based on paleo-indicators that are mechanistically linked to direct and indirect limnological effects of climate change.

Manzi, Florent; Agha, Ramsy; Mühlenhaupt, Max; Wolinska, Justyna

doi: 10.1007/s10750-022-04889-7pmid: N/A

Cyanobacteria periodically dominate phytoplankton composition in lakes, and produce a wide array of toxic secondary metabolites. Blooms of cyanobacteria often coincide with infections of zooplankton by microparasites (such as Metschnikowia bicuspidata, a parasitic yeast of Daphnia), and prior research has shown that cyanobacteria-based diets could mitigate fungal infections of the host. Here, we tested whether cyanotoxins could exert detrimental effects against free-living parasite stages: we inoculated two genotypes of the host Daphnia galeata × longispina with fungal spores, which were previously exposed to cyanobacterial extracts or to a placebo solution. Additionally, to test for interactive effects of cyanotoxins through environmental exposure and host consumption, Daphnia from each treatment were fed using either green algae or the same cyanobacterium. Exposing spores to cyanobacterial extracts did not reduce their infectivity; instead, parasite infectivity was increased, but only on one host genotype. The effect of host diet on parasite growth was also host-genotype dependent, with only one Daphnia genotype showing impaired spore production under a toxic diet. Our results suggest that dissolved cyanobacterial compounds released during blooms may not exert any detrimental effect on fungal spore banks, but likely influence transmission of the parasite when incorporated as part of the host’s diet.

Terlecki, Giulia; dos Santos Rodrigues, Lucas; Kikuchi, Eidi; Abbatepaulo, Felippe Veneziani; Bosenbecker, Camila; de Araújo Freire, Marcio; da Silva Cortinhas, Maria Cristina; Proietti, Maíra Carneiro; Cardoso, Luis Gustavo

doi: 10.1007/s10750-022-04898-6

Ruka, Adam T.; Johansen, Jeffrey R.; Leps, Jan; Loken, Zachary J.; Schuler, Matt; Mattes, Brian; Yates, Erika; Relyea, Rick A.

doi: 10.1007/s10750-022-04892-ypmid: N/A

Lake George is a highly monitored, oligotrophic lake that experiences widespread tourism in the summer months. The southern basin has more shoreline development than the northern basin, resulting in a south to north gradient of anthropogenic impairment. This study aimed to assess differences in nearshore diatom communities regarding gradients of water chemistry and watershed development throughout the lake. Using redundancy analyses, water chemistry explained more variation within diatom assemblages than watershed variables. Seasonal comparisons of watershed types, based on development, revealed SPC values to be significantly higher in the southern basin in all three seasons (spring, summer, and autumn). Among the three seasons, summer demonstrated the best potential for further monitoring of diatom communities with the north and south basins demonstrating differences in Shannon–Weiner (H′) diversity index values and proportions of Asterionella formosa, Fragilaria crotonensis, and Lindavia lemanensis. Dominant diatoms from previous studies in the lake were compared to present populations and showed a concomitant reduction in Stephanodicus spp. and Melosira spp. while smaller centric species continue to increase. Given the differences between the two basins, climate change is likely to manifest differently in the southern, more productive basin than the northern basin.

Greszkiewicz, Martyna; Fey, Dariusz P.; Lejk, Adam M.; Zimak, Michał

doi: 10.1007/s10750-022-04893-xpmid: N/A

Over the past few decades, the number of available spawning grounds for anadromous pikes, Esox lucius, on the Baltic Sea coast has been significantly reduced resulting in a drastic pike population decline in those areas. It is therefore a question if saline Baltic waters may support the spawning of anadromous pike. In the present experimental study, salinity had a harmful impact on the development of eggs from pikes of freshwater origin. The hatching success rates were 0% at 7PSU and only 16.7% at 4PSU, while hatching success at 0PSU was 89.7%. However, when the eggs were fertilized in fresh water and transferred to the tested salinities after 1 h, salinity had a positive effect on egg development and hatching success (0PSU: 80%; 4PSU: 83.3%; and 7PSU: 93.7%). We concluded that the spawning of the freshwater pike population in the saline water of the Baltic Sea is most likely not successful. Simultaneously, inflows of coastal marine waters into near-shore spawning grounds do not have a harmful effect on egg development if the eggs are already fertilized. The main management measures that can be suggested are to rebuild the anadromous population by spawning ground reconstruction. Sea-spawning population introduction can also be considered.

Shukla, Rohitashva; Bhat, Anuradha

doi: 10.1007/s10750-022-04894-wpmid: N/A

Over the past few decades, freshwater ecologists have been keen to understand the factors driving patterns of species co-occurrences in stream metacommunities where local communities are linked by dispersal. However, there is a lack of explanations for how and why some species co-occur more often than others and what species-specific ecological traits mediate such co-occurrence patterns in stream systems. Here, we studied monsoonal tropical stream fish communities of central India and examined species co-occurrence patterns using a network approach. We assessed the potential role of species-level properties (specifically, regional occupancy, local abundance and persistence, body size, and habitat and food preferences) in explaining fish metacommunity structure. We first constructed an abundance-based correlation network using only positive associations and performed modularity analysis to identify highly linked species sub-groups (modules). We then examined the relationship of species properties with module identity of species. We found that the co-occurrence network formed highly linked modular structures with a total of 6 modules. Predictive models suggested that species with similar ecological traits show higher possibility of co-occurring across the local communities. Food and habitat preferences, mean local persistence and body size were the single best predictors for module 0, 1 and 2 respectively. Food and habitat preference, and regional occupancy predicted species presence in module 5. We did not find statistically significant variables as predictors for the other two modules. This study signifies that the tropical fish metacommunity forms non-random co-occurrence network patterns with species modules and species-specific traits probably drive these modularity patterns.