River Food Chains Research Articles

Features of dynamics of the Southern Buh river aquatic environment parameters during the summer low-water period

Formulation of the problem. Global climate change causes transformation in the humidification regime and, as a result, makes adjustments to economic activities and features of water use. In the context of Ukraine, against the background of climate change, the runoff of most domestic rivers is declining, which especially in the limited period exacerbates the issue of balanced use of ecosystem services of aquatic ecosystems and prioritization of needs during resource allocation, control of rivers and establishment of their functioning. The purpose of the article. Recognizing the strategic importance of freshwater ecosystems in ensuring sustainable regional and national development, the study of the Southern Bug River was aimed at assessing its ecological status in order to identify sources of negative anthropogenic impact and identify general ecosystem distortions that may affect the functional integrity of the aquatic ecosystem. Methods. The research points on the Southern Bug River were determined by the method of randomization. The total length of the route was about 200 km. Also, the spatial location of settlements was taken into account, so that the investigated points were both upstream and downstream. Measurement of physicochemical parameters was performed by instruments: TDS-3, TDS/ЕС/Temp-meter HM COM-100, pH-meter Ezodo 6011A. The task of hydrobiological research was to find and identify species at the family level. The research was conducted at the end of July 2020, when the river entered to low flow phase. Results. On the basis of field research, the assessment of the ecological state of the Southern Bug River in the lower course (from the city of Pivdennoukrainsk) was carried out in the work. Regularities of pH dynamics and mineralization of the aquatic environment are established. The limits of the spatial influence of the Black Sea waters on the Southern Bug, the continental advance of which (upstream) almost 100 km up is due to the high level of regulation of basin runoff, have been specified. The same processes, as a consequence, affect not only biodiversity, but also the features of industrial and domestic water use. Using the stenobiontic approach, the level of ecological safety of the Southern Bug ecosystem in the lower course was assessed. Based on the obtained results of stenobioindication, the zoning of the studied area of the Southern Bug is proposed, which compares quite well with the results of pH and mineralization measurements. Only 1% of the route, which corresponds to the porous section of the river channel, was classified as a "healthy ecosystem". The closer to the mouth, the pH of the water gradually increases, which contributes to the intensification of the eutrophication process. Scientific novelty and practical significance. The obtained results are considered to be an integral part of future field research on the identification of sources of negative impact on the aquatic ecosystem of the Southern Bug. The novelty of the results obtained is a comprehensive assessment of the ecological state of the river ecosystem in the low flow period, which, in contrast to the concept of maximum permissible concentration, characterizes the state of the Southern Bug not point, but takes into account the cumulative and synergistic effects of anthropogenic impact. The latter are best manifested during the summer season, as a result of which the structure and biomass of the river's food chain change significantly. In addition, the analysis of the rational use of water resources of rivers allowed us to state that the modern system of environmental standards, which in particular regulate the quality of the aquatic environment, cannot ensure the preservation of river ecosystems.

River Food Chains Lead to Riparian Bats and Birds in Two Mid‐Order Rivers

River Food Chains Lead to Riparian Bats and Birds in Two Mid‐Order Rivers

River food chains lead to riparian bats and birds in two mid‐order rivers

AbstractRiver regulation can modify natural flow regimes with deleterious effects on aquatic communities. While the effects of flow manipulation on the physical environment and populations and assemblages of aquatic organisms have been described thoroughly, how and to what extent river regulation influences ecosystem processes like food web architecture is less studied. Emergent aquatic insect prey can provide an important food resource to riparian consumers like birds and bats with concomitant consequences for nutrient cycling through aquatic–terrestrial food webs, thus potentially increasing the spatial influence of river regulation into the riparian zone and beyond. We used naturally abundant stable isotopes of carbon and nitrogen to compare food web architecture (trophic position and reliance on an aquatic nutritional pathway) leading to birds and bats between a regulated river, the Tuolumne River downstream of Hetch Hetchy Reservoir, and an adjacent unregulated river, the Merced River, located in Yosemite National Park on the west slope of the Sierra Nevada, California, USA. We found that both birds and bats derived >50% of their nutrition from food webs originating in photosynthesis by algae. In addition, birds and bats occupied a similar trophic position to predatory fish in other systems. Both birds and bats seemed to rely more strongly on an aquatic nutritional pathway during the dryer year of our study period, underscoring the potential importance of emergent aquatic prey as a water subsidy in dry systems and in dry years. In the Tuolumne River, reservoir managers strive to simulate characteristics of the natural flow regime, including seasonal scouring flows and prolonged floodplain inundation. Although we found no conclusive evidence of an effect of river regulation on food web responses, our study suggests that nutrient cycling through aquatic–terrestrial food webs expands the potential influence of river regulation to organisms and ecosystems typically characterized as terrestrial.

Dynamics of Plankton Community in Banahao-Palhi River in Leyte, Philippines

Plankton consists of microscopic plants “phytoplankton” and animals “zooplankton“. They play a principal role in aquatic food web and zooplankton indicators of ecosystem change. Phytoplankton are the food source for zooplankton, and together, form the base of ocean and river food chains. In Leyte, few researches have been conducted in plankton specifically in river systems. The study was conducted to understand phytoplankton dynamics by first studying their occurrence, composition, and abundance. Three sampling sites were established along Banahao-Palhi river during dry and wet seasons. A total of 162 plankter samples were analyzed in the laboratory. Dry season sampling showed 99 pelagic algae belonging to 58 genera across sites. In all sites, the commonly occurring diatoms were Biddulphia, Meridion, and Synedra . For the green algae (Chlorophyceae) group, Groenbladia was the most common genus, while in the blue-greens (Cyanophyceae), Nostoc. In wet season, 165 pelagics in 68 genera were observed. Bacillariophyceae got the most number of pelagic algae in all sites for both seasons. For true zooplankton, eight families were recorded during the dry season with four, belonging to Rotifera, two under Copepoda and one, from Cladocera. Similar groups were found during wet season. Larvae of insects and benthics were found part of the zooplankton community. Insect groups include Orders Coleoptera, Diptera, Ephemeroptera, Megaloptera, Plecoptera and Trichoptera. Non-insect groups include Arachnida, Amphipoda, Gastropoda and fish larvae. The Rotifera is the commonly occurring holoplankton with six genera identified. However, the copepods were the most abundant in Brgy. Palhi while protozoans, in Brgy. Banahao.

CHARACTERIZING BENTHIC MACROINVERTEBRATE COMMUNITY RESPONSES TO NUTRIENT ADDITION USING NMDS AND BACI ANALYSES

Nonmetric multidimensional scaling (NMDS) is an ordination technique which is often used for information visualization and exploring similarities or dissimilarities in ecological data. In principle, NMDS maximizes rank-order correlation between distance measures and distance in the ordination space. Ordination points are adjusted in a manner that minimizes stress, where stress is defined as a measure of the discordance between the two kinds of distances. Before and After Control Impact (BACI) is a classical analysis of variance method for measuring the potential influence of an environmental disturbance. Such effects can be assessed by comparing conditions before and after a planned activity. In certain ecological applications, the extent of the impact is also expressed relative to conditions in a control area, after a particular anthropogenic activity has occurred. In this paper, two statistical techniques are employed to investigate the effects of stream nutrient addition on a riverine benthic macroinvertebrate community. The clustering of sampling units, based on multiple macroinvertebrate metrics across pre-determined river zones, is explored using NMDS. BACI is subsequently used to test for the potential impact of nutrient addition on the specified macroinvertebrate response metrics. The combination of the two approaches provides a powerful and sensitive tool for detecting complex second-order effects in river food chains. Statistical techniques are demonstrated using eight years of benthic macroinvertebrate survey data collected on an ultra-oligotrophic reach of the Kootenai River in Northern Idaho and Western Montana downstream from a hydro-electric dam.

River Food Chains

![Figure][1] CREDIT: PETE MCBRIDE Food chain length, or the number of organisms involved in any eat-or-be-eaten relationship, is a key property of aquatic habitats that regulates nutrient cycling, energy flow, and carbon exchange between aquatic ecosystems and the atmosphere. Investigating river food webs in North American watersheds, Sabo et al. (p. [965][2], published online 14 October) found discharge variation governed the link between ecosystem size (watershed area) and food chain length. River-drying truncated food chain length because intermittent streams have much higher discharge variation than perennial rivers. These results could be important for the management of rivers as drought and climate change may increase the frequency of river drying and discharge variability. [1]: pending:yes [2]: /lookup/doi/10.1126/science.1196005

Temporal trends in near-shore sediment contaminant concentrations in the St. Clair River and potential long-term implications for fish tissue concentrations

Near-shore surface sediment of the St. Clair River (Ontario) extending along 9km of waterfront downstream of local industries were contaminated with mercury (Hg), hexachlorobenzene, hexachlorobutadiene and octachlorostyrene based on data collected in 2006 and 2008. However, unlike Hg, concentrations of organic compounds were low at most stations suggesting improvements in sediment quality since 2001 (post sediment remediation projects). Concentrations of Hg were greater than Provincial Sediment Quality Guidelines and ranged as high as 41μg/g in the surficial 0–5cm sediment. Measured (2001–2004 data) and estimated (2006 data) concentrations of methyl Hg in invertebrates were greater than concentrations in invertebrates collected from upstream reference stations. Predicted methyl Hg concentrations in walleye using food chain multipliers, benthic invertebrate Hg tissue concentrations and current sediment concentrations exceeded human health consumption guidelines and were consistent with measured sport fish data supporting assumptions about Hg biomagnification. Historical data showed that for fish collected from the lower St. Clair River and Lake St. Clair, Hg concentrations have declined since 1978, but have remained stable since the mid 1980s, consistent with the sediment Hg data. The consistency in the sediment and fish datasets and the absence of a known significant local point source of Hg suggests that the sediment may be an important source of Hg to the St. Clair River food-chain.

The bioconcentration factor of perfluorooctane sulfonate is significantly larger than that of perfluorooctanoate in wild turtles ( Trachemys scripta elegans and Chinemys reevesii): An Ai river ecological study in Japan

Turtles rank high in the river food chain, and are suitable for predicting the bioconcentrations of chemicals through the food chain. Trachemys scripta elegans ( N = 46 ) and Chinemys reevesii ( N = 51 ) were captured in a river in Japan, from September to October 2003 and April to June 2004. Surface water samples were collected simultaneously from the same sites at which the turtles were caught. Serum perfluorooctane sulfonate (PFOS) ranged from 2.4 to 486 μg/L, while water PFOS levels ranged from 2.9 to 37 ng/L. The geometric mean (GM) (geometric standard deviation, GSD) of the bioconcentration factor (BCF) of PFOS was 10,964 (2.5). In contrast, the perfluorooctanoate (PFOA) level in water ranged from 16.7–87,100 ng/L, and serum PFOA ranged from <0.2 to 870 μg/L. The GM (GSD) of the BCF of PFOA was 3.2 (7.9). Furthermore, the BCF of PFOA decreased as the PFOA level in the surface water increased. PFOS could be preferentially bioconcentrated in biota, and PFOA, slightly bioconcentrated.

Polychlorinated -dibenzo-p-dioxins/furans and -dioxin-like biphenyls in eggs of common terns from lime island, St. Mary's river, Michigan, USA

Population collapse of common tern (Sterna hirundo) from Lime Island in the St. Mary's River, Michigan, USA were related to the 2,3,7,8-chlorine substituted dioxins, furans, dioxin-like PCBs, and other possible factors using unhatch egg target contaminant analysis. The most toxic congeners, 2,3,7,8-TCDD/DF was found in all samples at noticeable concentrations. Magnitude of sum 2,3,7,8-PCDD/DFs were within the range of 39–93 pg/g wet wt. Dioxin-like PCBs were within the range of 360–1230 ng/g wet wt. Great Toxic Equivalent Quantity (TEQ) contributions by 2,3,7,8-TCDF, 2,3,4,7,8-PeCDF, 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, and dioxin-like PCBs such as CB-77, CB-126 and CB-105 are considered greatly due to their influence of poor embryo development and consequent damage of embryos of common terns in egg injection studies. However, other organochlorines, heavy metals, and/or synergistic effects also taken in to account. On the whole, TEQs in the tern eggs were greater than the Lowest-Observable-Adverse Effect Level (LOAEL) for bald eagle (Haliaeetus leucocephalus) embryos observed in British Columbia, Canada. Concentrations of dioxin-like PCBs, dioxins, furans in the St. Mary's River food chain are at levels for concern for nesting colonial waterbirds. Eventually, the possible movements of analyzed chemicals downstream from a man-made flood event are discussed.

Flood disturbance, algal productivity, and interannual variation in food chain length

The length of a river food chain changed from year to year, shifting with the hydrologic regime. During drought years, grazers suppressed algae across a nutrient gradient, while predators were functionally unimportant. Following flood disturbance, predators suppressed grazers, releasing algae. These results suggest that hydrologic regime, rather than productivity, determines the functional length of this river food chain. Within years, algae and grazer biomass responded to an experimental productivity gradient in patterns predicted by simple trophic models that assume efficient energy transfer. Understanding differences among species within trophic levels, however, was crucial in delineating the controlling interactions.

Productivity, consumers, and the structure of a river food chain.

We tested models of food chain dynamics in experimentally manipulated channels within a natural river. As light levels increased, primary productivity and the biomass of algae and primary predators increased, but the biomass of grazers remained relatively constant. In the presence of a fourth trophic level, algae and primary predators decreased, but grazers increased. These results match predictions of food chain models based on classical predator-prey theory and suggest that simple models of multitrophic level interactions are sometimes sufficient to predict the responses of natural communities to changes in environmental productivity and predators.