Biomass In Rivers Research Articles

Dynamics of catches and state of stocks the European perch Perca fluviatilis in rivers in the middle Ob basin (in the Tomsk region)

European perch Perca fluviatilis Linnaeus, 1758 — is a mediumsized representative of the Percidae. It distributed in lowland rivers, lakes and artificial reservoirs, as well as in desalinated coastal areas of the seas of Northern Eurasia, with the exception of the Far East and the coast of the Arctic Ocean. This species is numerous almost everywhere. It is one of the main objects of industrial and amateur fishing. In the Middle Ob basin, a significant part of the life cycle of perch is associated with the floodplain system. There is, during the spring flood, its spawning and subsequent feeding of juveniles and producers take place. Therefore, the regulation of the Ob’s flow by the Novosibirsk hydroelectric power station dam served as one of the important factors that had a negative impact on the state of its reserves. Thus, within the Tomsk region, commercial catches of perch before the regulation of the Ob flow (1946–1961) averaged 354 tons per year, and after regulation (during the period of stable fishing pressure, in 1960–1985) — 157 tons. In recent years (2018–2022), the catch of perch has increased slightly and, according to official fisheries statistics, amounts to 211 tons per year, providing 5.9% of the total fish production in the region. Currently, the reserves of perch are in a relatively stable state, the estimated indicators of its biomass in rivers within the Tomsk region in recent years range from 1190.9 to 2277.5 tons, with an average number of 10.6 million pieces. The development of the perch’ reserves is satisfactory, averaging 94.2% of the recommended catch. Amateur fishermen do not have a significant impact on the state of perch stocks.

Contribution of invasive carp (Cyprinus carpio) to fish biomass in rivers of the Murray–Darling Basin, Australia

Following the introduction of the ‘Boolarra’ strain to Australia in the mid 1960’s, Common carp (Cyprinus carpio) rapidly spread in waterways across the Murray–Darling Basin (MDB) in southern-eastern Australia. A previous study of the population expansion based upon data up to the early 2000s suggested the carp population may have reached, and was fluctuating around, the ecosystem carrying capacity. It has been widely stated in the scientific literature and media that carp comprise up to 90% of fish biomass in MDB rivers; however, this figure is largely based on sparse data collected in the 1990s and the accuracy of this estimate is uncertain. Here, we analyse three decades (1994–2023) of electrofishing data to estimate the median proportion of total fish biomass contributed by carp across > 1,400 sites in lowland rivers (< 700 m elevation) of the New South Wales (NSW) portion of the MDB. The proportion of sites with fish biomass dominated (> 90%) by carp has declined from ≈ 33% of sites in the mid-1990s to ≈ 20% of sites. The proportion of biomass comprised by carp varied depending on the scale of analysis. Across the NSW MDB, carp accounted for a median of 57% (95% CI: 42.5–70.4) of fish biomass at the site level. At the river catchment scale estimates ranged from ≈ 45–66%. In contrast, the median proportion of carp within key rivers ranged from ≈ 46–80%, suggesting that carp can dominate total fish biomass in some rivers for short time-periods. The proportion of biomass contributed by carp at the NSW MDB scale was remarkably stable across decades, suggesting that the carrying capacity of carp may have been reached. Our revised estimates of the contribution of carp to overall fish biomass can facilitate informed debate around the dominance of carp in MDB rivers and provide important information for carp management in the future.

Long-Term Variations in Zoobenthos Characteristics in Watercourses on the the Khektsir Ridge

The results of long-term studies are used to present, for the first time, the structural organization of zoobenthos communities and the dynamics of their density and biomass in rivers and brooks of the the Khektsir Ridge, including the boundaries of the Bol’shekhekhtsirskii Reserve, Khektsirskii Wildlife Reserve (the southern part of the Russian Far East). The benthic organisms were found to contain 23 groups (22 groups in the spring and summer, 19 groups in the autumn, and 8 groups in the winter). Leading in the occurrence frequency (90%) were chironomids, mayflies, and oligochaetes. The chironomids and amphipods accounted for 37.0 and 19.1% of the total benthos density, and mollusks and amphipods, for 32.1 and 29.7% of the total biomass, respectively. Dominants in terms of density and biomass were amphipods; chironomids dominated in terms of density, and mollusks, in terms of biomass. The mean density of benthic organisms was 637 ± 21 spec./m2, and the mean biomass was 1.8 ± 0.2 g/m2. The benthic communities of rift segments in the rithral zone were found to be most productive. It is shown that the seasonal and long-term dynamics of zoobenthos communities is pronounced and can be traced in the group composition, structure, and quantitative characteristics.

Relationship between dissolved organic matter and phytoplankton community dynamics in a human-impacted subtropical river

Abstract Dissolved organic matter (DOM) is closely related to phytoplankton blooms, one of the most concerning environmental problems globally. DOM originates from phytoplankton production and metabolic activity and, in turn, can influence phytoplankton biomass and community structure. Therefore, clarifying the relationship between phytoplankton community dynamics and DOM has implications for bloom prevention and control as well as for aquatic ecosystem management. To understand this relationship further, we investigated phytoplankton communities at 110 sites in the dry and rainy seasons within the Dongjiang River basin, China, which is known for high rates of urbanization, industrialization, and agricultural intensification. The interaction between DOM (two humic-like DOM [C1 and C2] and two protein-like DOM [C3 and C4]) and phytoplankton community dynamics was investigated. Phytoplankton biomass and taxonomic composition were significantly related to C2, C3, and C4. The effect of C3 and C4 on phytoplankton taxonomic composition was prominent. C2 originating from agricultural wastewater increased phytoplankton biomass and changed phytoplankton taxonomic composition, whereas C1, originating from terrestrial soils and plants, did not stimulate phytoplankton biomass in rivers. There were clear change points, where phytoplankton abundance rapidly increased or decreased with changes in the concentrations of DOM components. Results suggested that DOM controls phytoplankton community dynamics and their relationship changes with variations in DOM chemical composition. DOM generated by anthropogenic activities may act as a potential warning of phytoplankton blooms.

Nitrogen stimulation of periphyton biomass in rivers: Differential effects of ammonium-N and nitrate-N

The ecological effects of wastewater treatment plant (WWTP) discharges into rivers typically include elevated periphyton biomass resulting from enrichment by dissolved reactive phosphorus (DRP), dissolved inorganic nitrogen (DIN), or both. WWTP discharges may transfer DIN to receiving water as ammonium-N (NH4-N) and, following nitrification steps, nitrate-N (NO3-N). The potential for NH4-N to exacerbate nuisance periphyton biomass compared to NO3-N is not well understood. Theoretically, NH4-N is the more energy-efficient source of N for algae, but its effect on algal growth rates depends on concentration, interaction with NO3-N, and environmental conditions, such as temperature. We investigated the relative importance of NH4-N and NO3-N in WWTP discharges by tracking periphyton biomass and algal assemblage composition in streamside channels for 27 d under 500 µg DIN/L comprising different proportions of NH4-N: 0.5% (low-NH4, ambient levels of NH4-N, 2.2 µg/L), 30% (medium-NH4, 160 µg/L), and 77% NH4-N (high-NH4, 389 µg/L). The DIN treatments had replete DRP (25 µg/L) and were compared to controls with no enrichment (control) and DRP enrichment only (P-control). Biomass was measured as chlorophyll a (Chl a) and ash-free dry mass (AFDM), which showed contrasting responses to different proportions of NH4-N enrichment. Chl a was higher under high-NH4 than under low-NH4 (p < 0.01, 50% higher at maximum Chl a on d 20). Under medium-NH4 and low-NH4, Chl a was not different from the controls and P-controls (p > 0.15). AFDM did not differ among the 3 DIN treatments (p > 0.11) but was higher in all DIN treatments than in the controls (p < 0.05). Algal assemblage composition discriminated the controls from all other treatments and the low-NH4 from high-NH4 treatments. The assemblage analyses indicated that high-NH4 favored enhanced cell division rates in small diatoms, especially Encyonema minutum. Higher Chl a/unit volume of small taxa than larger taxa likely explained elevated Chl a under high-NH4. The results illustrated that, with replete DRP, elevating DIN through enrichment with NH4-N may cause additional increases in periphyton biomass as Chl a compared to elevating DIN through NO3-N enrichment. Consequently, enhanced management to specifically reduce NH4-N outputs in WWTP discharges may assist in the control of nuisance periphyton downstream.

Origin of Fish Biomass in a Diverse Subtropical River: An Allochthonic-Supported Biomass Increase Following Flood Pulses

The origin of resources supporting metazoan biomass in rivers has long been a subject of debate. The river wave concept (RWC) postulates that the energetic basis of food webs varies along its spatial–temporal location with respect to flow pulses. According to the RWC, river flow determines carbon assimilation in food webs, but this may also depend on river geomorphology. However, studies testing this theory are scarce, particularly those from large subtropical rivers. To analyse the origin of fish biomass in areas of differing geomorphology, we combined stable isotope analysis with standardised measurements of biomass of a diverse fish assemblage along the lower Uruguay River. Furthermore, using 14 years of monitoring data, we tested for relationships between the biomass of species dominantly fuelled by allochthonic resources and the river flow. Fish biomass was dominantly allochthonous-derived along most of the studied sites. At all trophic levels, autochthonous-derived fish biomass was the highest in an upstream anabranch functional process zone (FPZ) (fuelling 54% of the total biomass), while allochthonous-derived biomass prevailed downstream, in the widest sections of an unconstrained lowland FPZ (fuelling 64–72% of the total biomass). Moreover, the dominant species that derived most of its biomass from allochthonous resources (Prochilodus lineatus) increased its biomass following flood pulses. This study supports the RWC statements that, at a spatial scale, local river geomorphology affects fuelling sources for food webs (probably by determining contrasting resource availability scenarios) and, at a temporal scale, increases in the allochthonous fraction of biomass are driven by flood pulses.

Application of a spectrofluorimetric tool (bbe BenthoTorch) for monitoring potentially toxic benthic cyanobacteria in rivers

Over the last decade reports of animal poisoning following accidental consumption of neurotoxin-producing benthic cyanobacteria (mainly Phormidium spp.) have increased. There is a need for rapid and cost-effective tools to survey benthic cyanobacteria. In this study we assessed the performance of the BenthoTorch, a fluorometric probe that provides in situ estimations of cyanobacteria, diatoms and green algae biomass in biofilms. Biofilms (n = 288) were analysed from two rivers in France and eight in New Zealand. Correlations between chlorophyll-a measured using the BenthoTorch and spectrophotometry were higher for thin (<2 mm) compared to thick (>2 mm) biofilms (r2 = 0.58 and 0.27 respectively; p < 0.001). When cyanobacteria represented less than 50% of the total biomass (based on biovolumes), microscopic and BenthoTorch compositional estimations were significantly correlated (r2 = 0.53, p < 0.001). Conversely, there was no correlation when cyanobacteria exceeded 50% of the total biomass. Under this scenario diatoms were overestimated. Our results suggest that the observed biases occur because the BenthoTorch only measures the upper biofilm layer and it underestimates the biomass of phycoerythrin-containing cyanobacteria. To improve the performance of this sensor and render it a useful tool for a rapid evaluation of benthic cyanobacterial biomass in rivers, we propose that: (i) the algorithms based on the LEDs responses currently available on this tool need revision, (ii) new excitation wavelengths should be included that allow the fingerprints of phycoerythrin-containing cyanobacteria to be discriminated, and (iii) a sensor that penetrates the biofilms is needed to obtain more accurate estimates of cyanobacterial biomass.

The non‐indigenous diatom Didymosphenia geminata alters benthic communities in New Zealand rivers

Summary1. Blooms of the benthic, stalked diatom Didymosphenia geminata were first observed in New Zealand in 2004. Since then, D. geminata has spread to numerous catchments in the South Island and is also spreading in its native range. The species is a rare example of an invasive alga in lotic systems.2. Ecosystem effects may be expected as D. geminata attains unusually high biomass in rivers. We examined data from three independent studies in three South Island, New Zealand, rivers for evidence of effects on periphyton biomass and benthic invertebrate communities.3. The combined results confirmed that the presence of D. geminata was associated with greatly increased periphyton biomass and, in most cases, increased invertebrate densities. We also recorded shifts in community composition, dominated by increased densities of Oligochaeta. Chironomidae, Cladocera and Nematoda also generally increased in density with D. geminata. Significant increases or declines in other invertebrate taxa were inconsistent among rivers.4. In all three studies, increased spatial invertebrate community homogeneity was associated with high D. geminata biomass at the within‐river scale. However, no declines in taxon richness or diversity were detected.5. Although ecosystem effects of D. geminata on existing periphyton biomass and invertebrate communities are measurable, no inferences can be made from the present data about effects on higher trophic levels (fish).

Macrophyte biomass and water quality in Ontario rivers

An empirical survey of macrophyte biomass collected from 38 stations along 28 rivers in southwestern Ontario was conducted in 1999 and 2000 to quantify the relationship between biomass and instream nutrients and dissolved ions. Multiple regression models showed that mean and maximum biomass were weakly but significantly related to the nutrients N and P; these variables explained ∼27% of the variability in biomass across stations. Models developed with 1999 data were improved with the addition of measurements of total residue, which is correlated to ionic concentrations and turbidity, providing a rough indication of instream light availability. However, validation of the models with an independent data set, collected in 2000, showed that the nutrient-only models were the most robust across data sets. We detected a significant lack of fit in all of the models developed, indicating the independent variables used were not best at explaining variability in macrophyte biomass. Although our study yielded only weak predictions of biomass in rivers, the robustness of the models based on nutrients among data sets suggests that nutrient-abatement programs, focussed primarily on N, may be successful in reducing nuisance macrophyte biomass.

The estimate of fish density and biomass in rivers on the basis of relationships between specimen size and efficiency of electrofishing

It is shown that the catch-effort electrofifhing methods, which are those most often employed for estimates of riverine fish density and biomass, are often not precise. These multiple sampling procedures are time- and manpower-consuming, and can change the habitat and fish community structure. The results, collected in rivers of different size and character, show curvilinear relationships between the average specimen size and the percentage, number and biomass of fish caught by one electrofishing. Using such relationships minimizes the alteration of fish community structure by the sampling procedure. Conditions which must be fulfilled for proper use of the proposed relationships are discussed.