Aquatic Ecology最新文献

Over 27 years in Great Salt Lake (GSL: Utah, USA), phytoplankton relative abundances of chlorophytes, diatoms and cyanobacteria varied dramatically (monthly < 10–90% for each). This observed variability within the lake was compared to laboratory experimental results with pure cultures (> > 90%) of several of the most common GSL phytoplankton (chlorophyte–Dunaliella viridis, diatom–Nitzschia epithemioides, cyanobacterium–Euhalothece sp.). Maximum abundances and growth rates were measured across ranges of temperature (10–30 °C), salinity (30–150 ppt) and nutrients (nitrogen: 0.0–0.64 mg/L, silica:17–51 mg/L) observed within GSL. Experimental results indicated the abundance and growth rate of D. viridis increased as salinity and nitrogen increased and decreased as temperature increased. The abundances and growth rates of N. epithemioides and Euhalothece decreased as salinity increased, and increased as temperature and nitrogen increased, and N. epithemioides increased as silica increased. Observed GSL phytoplankton relative abundances responded to environmental conditions as observed in the experiments, but correlations were weak except for chlorophytes, as diatoms and cyanobacteria relative abundances occasionally increased with unfavorable experimental conditions. The weak correlations between laboratory results and GSL observations could be due to the release of diatoms and cyanobacteria from microbialite biofilms in the lake’s benthos with cold stress and high winds, as a 5–10% release can produce diatom and cyanobacteria phytoplankton relative abundances of 24–48%. This suggests a novel potential link between GSL pelagic and benthic zones.

Freshwater rock pools formed due to erosion and weathering in outcrops are known to act as essential frog breeding habitats. In the northern part of the Western Ghats-Sri Lanka biodiversity hotspot, large freshwater rock pools are shown to be important for adult stage of three species of frogs: Jaladhara Skittering Frog (Euphlyctis jaladhara), Nilphamari Narrow-mouthed Frog (Microhyla nilphamariensis), and Common Indian Treefrog (Polypedates maculatus). Previous studies have thus recommended conservation of existing rock pools and restoration or creation of rock pools for amphibian conservation, in light of reduced rock pool availability due to rapid conversion of outcrops to orchards. To this end, knowledge of tadpole ecology in the rock pools is essential for further research and conservation actions. We assessed the influence of abiotic (pool size, monsoon progression) and biotic (predator abundances) factors on occurrence and abundance of tadpoles of the three species by periodically monitoring the ephemeral freshwater rock pools in lateritic plateaus of the northern Western Ghats. Tadpole occurrences and abundances were negatively associated with monsoon progression, and not associated with predator abundances for all species, while they were positively associated with rock pool size, species-specifically.

We detected the first occurrence of Nile tilapia (Oreochromis niloticus) in the brackish and marine ecosystems of Rio Grande do Sul, the southernmost state of Brazil, following the catastrophic floods that impacted the region in the fall of 2024. We conducted seven beach surveys from the Tramandaí Lagoon inlet, extending 80 km north and 50 km south. These surveys were carried out using a four-wheel-drive pickup truck traveling at speeds up to 40 km/h, with 2–4 observers scanning the entire beach from the wash zone to the base of the dunes. For every 10 km of beach surveyed, we performed transect walks of 1 km in length. A total of 188 specimens were found stranded up to 80 km north of the Tramandaí Lagoon inlet. Oreochromis niloticus can be managed under controlled conditions with restrictions, subject to specific regulations according to the official list of invasive exotic species in the State of Rio Grande do Sul. The escape of this species from aquaculture facilities and recent records (post-2019) in Tramandaí Lagoon underscore the need to establish a long-term monitoring program for invasive exotic species in the Tramandaí River Hydrographic Basin and to improve measures to prevent escapes.

This study examines how the invasion of Hydrilla verticillata affects native submerged macrophytes in the Rosana Reservoir, focusing on its impact at both species and family levels. The research analyzed data on the presence and absence of aquatic macrophytes in both invaded and non-invaded sites before and after the introduction of H. verticillata. Our findings indicate that H. verticillata alters the probability of occurrence of native species through both competitive suppression and facilitation. For the Hydrocharitaceae family and the species Egeria najas, the presence of H. verticillata decreased their probability of occurrence in invaded sites. In contrast, the probability of occurrence of the Characeae family, along with Nitella furcata and Chara guairensis, increased in post-invasion conditions within invaded sites. This suggests that non-native plants can have divergent impacts on native species, with some being negatively affected while others may benefit. These results highlight that invasive species can have divergent effects, influencing species and family-level interactions in aquatic ecosystems. Additionally, the influence of native species richness on the probability of occurrence of different species and families was found to be affected by the presence or absence of H. verticillata. Overall, the research underscores the importance of assessing the impact of non-native species not only at the species level but also in terms of their broader effects on native species families and ecosystems.

Macrophytes like Lemna minor and cyanobacteria species (for example, Microcystis aeruginosa and M. flos-aquae) co-exist naturally in water bodies, competing for nutrients, light and space, which influence their growth. The introduction of external factors such as herbicides into water bodies can influence the interaction between these aquatic organisms. This study examined the impact of paraquat, a widely used herbicide, on the interaction between L. minor and M. aeruginosa and M. flos-aquae. This was done by co-culturing L. minor (12 viable colonies) with M. aeruginosa and M. flos-aquae (both at 3.0 × 10⁵ cells mL⁻¹) separately, and with 10 µg L⁻¹ of paraquat in BG-11 medium for 5 days. Monocultures of L. minor, M. aeruginosa, and M. flos-aquae were exposed to different concentrations of paraquat (0, 0.01, 0.1, 1, 10, and 50 µg L⁻¹). An increase in paraquat concentration reduced the growth and biomass of L. minor, M. aeruginosa, and M. flos-aquae in single cultures, while decreasing total microcystin production in M. aeruginosa but increasing it in M. flos-aquae. When co-cultured with either M. aeruginosa or M. flos-aquae, the growth and biomass of L. minor decreased, and its POD activity increased. The presence of M. aeruginosa increased the MDA content and GST activity of L. minor, while the presence of M. flos-aque plus paraquat increased its proteins content and GST activity. On the other hand, the presence of L. minor plus paraquat decreased the growth and biomass of both cyanobacteria (M. aeruginosa and M. flos-aquae) and increased their microcystins production, H₂O₂ contents, POD and GST activities, and total proteins. These results demonstrate that the presence of paraquat amplifies the suppression of growth and increased stress of L. minor caused by both M. aeruginosa and M. flos-aquae, and vice-versa. This situation may exacerbate the competitive dynamics in aquatic environments by potentially altering community structures, a situation that could affect overall ecosystem health.

The escalating salinization of lakes and wetlands is reducing the ecological functions of these ecosystems and undermines the survival and diversity of aquatic macrophytes. Although the application of amendments has been shown to efficiently alleviate the salinization of terrestrial ecosystems, their improvement effects on saline aquatic ecosystems are yet to be fully understood. We conducted mesocosms experiment to investigate the effects of three soil amendment treatments—biochar, desulfurized gypsum, and zeolite powder—on saline sediment and the submerged macrophyte Myriophyllum spicatum. The results showed that all three amendments effectively reduced salinity and pH in both the sediment and water column, thereby alleviating salt stress on M. spicatum, decreased the levels of antioxidant enzymes and significantly enhanced the growth of M. spicatum. The biochar treatment showed the most pronounced improvements, with a 34% reduction in sediment salinity and a 46% increase in macrophyte root length. High-throughput sequencing results revealed that the rhizosphere microorganisms in the biochar-amended group had a higher OTU diversity compared to the other groups. LEfSe analysis further revealed that biochar increased the abundance of the key functional microbial groups responsible for organic matter decomposition and the nitrogen and phosphorus cycles, such as Microscillaceae, Promicromonospora, and Arthrobacter. Structural equation modeling analysis suggested that desulfurized gypsum and zeolite powder primarily improved sediment physical properties, while biochar had both a direct effect by promoting macrophyte growth and an indirect effect through water and sediment quality amelioration. Our study provides information on the effectiveness of various soil amendments for habitat improvement in brackish wetlands and offers valuable insights for macrophyte restoration in specific habitats.

Graphical abstract

Dilution experiments were conducted to estimate the microzooplankton (MZP) grazing rate and phytoplankton growth rate in Chilika Lagoon during the summer and winter seasons. The phytoplankton growth rate ranged between 0.71 ± 0.11–2.86 ± 0.10 day^–1 and 0.62 ± 0.01–1.45 ± 0.02 day^–1, whereas MZP grazing rates ranged from 1.59 ± 0.11–2.92 ± 0.12 day^–1 to 1.48 ± 0.05–2.15 ± 0.33 day^–1 during the summer and winter seasons respectively. Experimental results showed that the phytoplankton growth rate was lower than the MZP grazing rate in both seasons, indicating constant grazing pressure on the prey community. Also, MZP was capable of grazing more than 100% of daily primary production and 46–95% of daily phytoplankton standing stock. The Southern Sector of the lagoon was under high grazing pressure due to low phytoplankton biomass and high MZP abundance during the study period. Grazing pressure was higher in the Central Sector and Outer Channel during the winter and in the Northern Sector (NS) during the summer. The observed results highlight MZP as a potential consumer for phytoplankton primary production. The positive correlation between phytoplankton growth rate and grazing rate (R = 0.820, P < 0.05) represents MZP as a major control of phytoplankton growth in both summer and winter. The high growth rate of phytoplankton during the summer season was balanced by the MZP grazing. All the sectors exhibited seasonal variations in grazing pressure depending on phytoplankton abundance and salinity conditions. From our study, we can conclude the top-down control of phytoplankton biomass by MZP in the Chilika Lagoon due to the high grazing rate.

Coral reefs are among the most productive and diverse biological ecosystems in the world, hosting more than a quarter of all marine species. The coral reefs in the Persian Gulf, a sea surrounded by arid lands with high air temperatures, intense light, and high salinity of water, along with a remarkably large annual cycle of sea surface temperatures (SST), persist under challenging environmental conditions. The present study explored the changes in the symbiotic dinoflagellate and GFP-like proteins in a heat stress tolerant submassive Porites corals versus heat stress sensitive tabular Acropora corals across seasonal and depth gradients in Kish Island in the Persian Gulf. The results revealed that the symbiosis types was constant in both species, depth, and sampling seasons. However, an explicit change was observed in the quantity of symbiotic algae and Durusdinium trenchii as a heat-tolerant symbiodiniaceae dominating both coral species. Likewise, the level of GFP-like Protein mRNA expression, especially in P. harrisoni, significantly varied across seasonal and depth gradients. The GFP-like Protein mRNA was upregulated during summer in both species and decreased in P. harrisoni inhabiting the deep reef. Overall, the findings suggest that simultaneous changes in the symbiotic dinoflagellate and GFP-like proteins may be the key factors underlying the resistance of scleractinian corals during warm episodes in the Persian Gulf as the world’s warmest sea.

The identification of octopus species, particularly those in the genera Octopus and Pinnoctopus, has been challenging due to the species' morphological plasticity and the presence of cryptic species in the western Atlantic. The use of molecular tools like DNA barcoding is important for accurate taxonomic identification, especially in understudied regions like the Greater Caribbean. This study aimed to identify octopus species in the Mexican Caribbean and the southwestern Gulf of Mexico, and to evaluate the genetic structure of Octopus insularis using the mitochondrial COI gene. Here, the species Octopus insularis was recorded for the first time at Banco Chinchorro and Punta Herrero, Quintana Roo, Mexico. Similarly, both O. insularis and Pinnoctopus furvus were recorded for the first time in the Lobos-Tuxpan Reef System. Additionally, 93 new octopus DNA sequences were obtained for the study area. The genetic analysis revealed 31 haplotypes of O. insularis, with a haplotype diversity of 0.53, indicating moderate genetic diversity. Three genetically distinct populations were identified from Brazil to the Gulf of Mexico, with two populations in Brazil showing the highest pairwise Fst values, indicating significant genetic differentiation. Importantly, the study assessed the genetic structure of O. insularis in the Caribbean Sea and Gulf of Mexico for the first time, revealing that these sites form a population. This suggests that the octopus populations in the region, covering areas like Colombia, Panama, Mexican Caribbean (Quintana Roo), and the Gulf of Mexico (Veracruz Reef System and Lobos-Tuxpan Reef System), could be managed as a fishery stock, highlighting the need for a unified approach to the sustainable management of these fishery resources.

Research on non-marine ostracods in Yunnan Province, especially in desiccated and irrigation environments, is limited, restricting our understanding of their survival strategies, adaptation mechanisms, and biogeographical patterns within this region. The present study investigates ostracods across 43 sites in eastern Yunnan, including desiccated rice fields, ditches, rivers, ponds, vegetable fields, karstic cave, spring, and stream. A total of 483 living ostracod individuals were collected from 15 out of the 43 sampling sites, encompassing eleven species predominantly from the Cyprididae family, accompanied by species from the Candonidae, Cyclocyprididae and Ilyocyprididae families. Our results of culturing experiments with dried muds indicated survival of dormant ostracods, as an important strategy of recolonizing non-permanent water bodies after dry phases. Thus, recolonization is realized through an ‘ostracod bank’, not only an egg bank. Significant differences in species composition were observed across regions, reflecting the dynamic responses of ostracods to agricultural practices and environment. Furthermore, documented elevational distributions of some species could be extended based on our study areas in an elevation of 887‒2064 m asl. The study also documents three species new to Yunnan, increasing the number of known recent non-marine ostracod species in this province to 33. The newly recorded species are Stenocypris hirutai Smith and Kamiya (Hydrobiologia 559: 331–355, 2006), Stenocypris viridis Okubo, 1990 and Hemicypris ovata Sars, 1903. These findings provide insights into ostracod ecology, biogeography, and aquatic ecology, revealing adaptive and resilient mechanisms of ostracods in temporary, eutrophic habitats.