Tubificid Worms Research Articles

Antioxidant enzyme activity and pathophysiological consequences in the sludge worm Tubifex tubifex under acute and sub-lethal exposures to the fungicide Tilt ®

This study aimed to evaluate the effects of propiconazole on the tubificid segmented worm, Tubifex tubifex. The animals were exposed to various concentrations of propiconazole for 96 h to assess the acute effect of this fungicide and for subacute level animals were exposed for 14 days with 10% and 20% of the 96 h LC50 value (0.211 and 0.422 mg/l, respectively). The 96 h LC50 value was determined to be 2.110 mg/l, and sublethal propiconazole concentrations caused significant changes in the oxidative stress enzymes. When compared to control organisms, superoxide dismutase (SOD) and catalase (CAT) activity first decreases and then significantly increases on days 7 and 14. However, GST activity decreases and MDA concentration rises in a concentration- and time-dependent manner throughout the exposure period. In addition, the impacts of propiconazole on Tubifex tubifex were characterized and depicted using a correlation matrix and an integrated biomarker response (IBR) assessment. These findings suggest that exposure to this fungicide distorts the survivability and behavioral response in Tubifex tubifex at the acute level. In addition, it modulates changes in oxidative stress enzymes at the sublethal level. Furthermore, the species sensitivity distribution curve indicates that this tubificid worm has a high risk of survival in the presence of the fungicide propiconazole in aquatic ecosystems.

Distribution of the alien Tubificid worm Branchiura sowerbyi (Beddard, 1892) in Morocco

The tubificid worm Branchiura sowerbyi Beddard, 1892 is one of the most successful invasive freshwater oligochaetes worldwide. In the Maghreb region, this species was known only from two localities in Morocco and from one locality in Libya. This paper presents novel information about the current distribution and presence of this invasive species in Morocco, and provides guidance on further areas of research regarding invasive oligochaetes in North African.

Behavioral toxicity, histopathological alterations and oxidative stress in Tubifex tubifex exposed to aromatic carboxylic acids- acetic acid and benzoic acid: A comparative time-dependent toxicity assessment

This study evaluated Acetic acid (AA) and Benzoic acid's (BA) acute and sublethal toxicity by observing mortality, behavioral responses, and changes in the levels of oxidative stress enzymes in Tubifex tubifex. Exposure-induced changes in antioxidant activity (Catalase, Superoxide dismutase), oxidative stress (Malondialdehyde concentrations), and histopathological alterations in the tubificid worms were also noted across exposure intervals. The 96 h LC50 values of AA and BA to T. tubifex were 74.99 and 37.15 mg/l, respectively. Severity in behavioral alterations (including increased mucus production, wrinkling, and reduction in clumping) and autotomy showed concentration-dependent trends for both toxicants. Although histopathological effects also showed marked degeneration in the alimentary and integumentary systems in highest exposure groups (worms exposed to 14.99 mg/l for AA and 7.42 mg/l for BA) for both toxicants. Antioxidant enzymes (catalase and superoxide dismutase) also showed a marked increase of up to 8-fold and 10-fold for the highest exposure group of AA and BA respectively. While species sensitivity distribution analysis revealed T. tubifex as most sensitive to AA and BA compared to other freshwater vertebrates and invertebrates, General Unified Threshold model of Survival (GUTS) predicted individual tolerance effects (GUTS-IT), with slower potential for toxicodynamic recovery, as a more likely pathway for population mortality. Study findings demonstrate BA with greater potential for ecological effects compared to AA within 24 h of exposure. Furthermore, ecological risks to critical detritus feeders like T. tubifex may have severe implications for ecosystem services and nutrient availability within freshwater habitats.

Microplastics in Freshwater Sediments Impact the Role of a Main Bioturbator in Ecosystem Functioning.

While microplastic transport, fate, and effects have been a focus of studies globally, the consequences of their presence on ecosystem functioning have not received the same attention. With increasing evidence of the accumulation of microplastics at sediment-water interfaces there is a need to assess their impacts on ecosystem engineers, also known as bioturbators, which have direct and indirect effects on ecosystem health. This study investigated the impact of microplastics on the bioturbator Tubifex tubifex alongside any effects on the biogeochemical processes at the sediment-water interface. Bioturbators were exposed to four sediment microplastic concentrations: 0, 700, 7000, and 70000 particles kg-1 sediment dry weight. Though no mortality was present, a significant response to oxidative stress was detected in tubificid worms after exposure to medium microplastic concentration (7000 particles kg-1 sediment dry weight). This was accompanied by a reduction in worm bioturbation activities assessed by their ability to rework sediment and to stimulate exchange water fluxes at the sediment-water interface. Consequently, the contributions of tubificid worms on organic matter mineralization and nutrient fluxes were significantly reduced in the presence of microplastics. This study demonstrated that environmentally realistic microplastic concentrations had an impact on biogeochemical processes at the sediment-water interface by reducing the bioturbation activities of tubificid worms.

Nitrogen loading increases both algal and non-algal turbidity in subtropical shallow mesocosms: Implication for nutrient management

Excess nitrogen (N) loading in summer often boosts phytoplankton growth and increase algal turbidity. In eutrophic shallow lakes, the increased algal production may also augment the abundance of deposit-feeding tubificid worms and thereby sediment resuspension and non-algal turbidity. However, few studies have explored the effects of high N loading on this benthic process in eutrophic shallow lakes. Here, we conducted an outdoor mesocosm experiment in a summer-winter season (177 days) on the shore of subtropical Lake Taihu, China. Each mesocosm contained a 10 cm layer of lake sediment and 450 L of lake water. Nitrate was added weekly to three of the mesocosms, while another three functioned as controls. Our results showed that N addition significantly increased algal particles as water chlorophyll a (Chl-a) increased significantly following N addition. Moreover, significantly higher levels of inorganic suspended solids (ISS) were observed in the mesocosms with added N, indicating elevation of non-algal turbidity as well by the N addition. We attribute the latter to increased sediment resuspension as the abundance of tubificid worms was significantly higher in the N addition mesocosms. Accordingly, our study indicates that high N loading in subtropical shallow lakes may boost both algal and non-algal turbidity in part via benthic-pelagic coupling processes. Our results suggest that alleviation of eutrophication in shallow eutrophic lakes may require a strategic approach to adequately control both N and phosphorus.

Growth and breeding performance of broodfish and larval growth of Heteropneustes fossilis with feeds

A 63-day long indoor experiment was carried out to determine the effects of four different diets of: live tubificid worms (T1), live tubificid worms with formulated feed (T2), shrimp with formulated feed (T3) and formulated feed (T4) on brood development and larval growth of Heteropneustes fossilis. Broodfish were fed twice a day with experimental diets. Reproductive performance of H. fossilis was evaluated based on growth parameters and fry production of broodstock. The result showed that while the highest (16.37 ± 0.90g) and the lowest (7.03 ± 0.85g) weight gain was obtained in T2 and T4 respectively, however, there was no significant difference between treatments T1 and T3. The FCR of T2 was found to be the lowest followed by T3, T1 and T4, respectively. The highest fecundity was found in T2 (4245.48 ± 347.38) followed by T3 (3747.10 ± 317.99), T1 (3583.96 ± 327.27) and T4 (3191.95 ± 444.55). The rate of hatching and their survival was significantly higher in T2 followed by T3, whereas T1 and T4 showed significantly lower hatching and survival rate. After 28 days of rearing, larvae obtained from T2 treatment showed the highest growth performance compared to other treatments. The findings of the current research suggested that live feed (tubificid worms) supplemented with formulated feed may enhance the breeding performance and larval growth of H. fossilis and could be considered an affordable option for small-scale hatcheries. Ann. Bangladesh Agric. (2021) 25 (2) : 13-25

Interactions between microbial activity and bioturbation modes of benthic invertebrates determine nutrient releases from reservoir sediments

Abstract Bioturbating invertebrates play key roles in nutrient recycling from sediments to the water column in most lentic ecosystems. Nevertheless, the role of bioturbating fauna on nutrient cycling depends on complex interactions between their bioturbation modes and both the sedimentary conditions and the microbial activity occurring inside sediments. This study aims to evaluate the effect of different bioturbation modes by two invertebrate species (tubificid worm Tubifex tubifex and chironomid larvae of Chironomus plumosus), on the release of nutrients (NH4+, NO3−, and PO43−) from three different types of sediments characterised by distinct microbial activities and nutrient (N and P) contents. We expected that the influence of a bioturbation mode on nutrient fluxes was dependent on the microbial activity and organic matter processes occurring in sediments. Aquatic mesocosms were setup in the laboratory with three fauna treatments (i.e. without fauna, with tubificid worms, and with chironomid larvae) and three sediment types (collected in three reservoirs). The presence of bioturbating invertebrates increased PO43− concentrations into the water column (from 1.3‐ to 17‐fold higher concentrations) depending on the sediments tested. PO43− releases in the water column were positively linked to total P concentration and microbial activity in sediments. The influences of tubificid worms and chironomid larvae on PO43− releases into the water were not only due to their bioturbation modes but also depended on the interactions with P dynamics (e.g. adsorption of PO43− by iron oxides) at the water–sediment interface. The influence of fauna on the release of dissolved inorganic nitrogen (DIN) varied strongly among sediments due to the control of N cycling by microbial processes. In sediments characterised by the lowest microbial activity, DIN release from sediments to the water column was significantly stimulated by invertebrates (from 1.3‐ to 3.7‐fold higher). In contrast, no fauna effect was detected compared to controls in sediments characterised by the highest microbial activity. This study demonstrated that the influence of the bioturbation mode on nutrient (i.e. PO43− and DIN) dynamics at the water sediment interface was largely modulated by the intensity of microbial activity and biogeochemical processes occurring in sediments.

A Study of Some Aquatic Oligochaetes Community in Shatt Al-Hillah/ Middle of Iraq

The current study discusses the spatial distribution of Oligochaete communities on Shatt Al-Hillah. Monthly samples of Oligochaete worms were gathered from four locations along the Shatt Al-Hillah in the middle of Iraq, between September 2019 and May 2020. show the study for the existence of521Individual aquatic Oligochaeta belong to 7 species from the Naididae and Lumriculdae subfamilies, as well as the Pristinae subfamily, and in Site S3 had the largest number of worms, with 180 worms from 7 species being detected, while in Site S2 had the least number of worms, 107 from 5 species. The largest individual numbers were registered in February, while the lowest were recorded in April. The species, Prisma aequiseta, was first recorded, in the Shatt Al-Hillah rive. Show tubificid worms, Branchuira sowerbyi, and Limnodrilus hoffmeisteri were the most abundant species in the Shatt Al-Hillah.

Macrobenthic diversity and its bioindicator potential in urban reservoirs: A Sri Lanka case study

AbstractStudies addressing the macrobenthic diversity and their potential as bioindicators in water quality assessment programs are sparse for Sri Lanka. The present study investigated the macrobenthic diversity in relation to water quality parameters in some urban reservoirs in the Western Province of Sri Lanka, assessing their potential as bio‐indicators in water quality assessment programs. The six study reservoirs included the Ihalagama Tank, Peralanda Tank, Kesbewa Tank, Boralesgamuwa Tank, Bolgoda Lake and Beira Lake. The microbenthic fauna abundance at randomly selected locations (n = 9) in each reservoir and selected water quality parameters (temperature; pH; electrical conductivity; total dissolved solids; BOD5; dissolved nitrates; total dissolved phosphate and alkalinity of the overlying water at each location were measured between July 2020 and January 2021, using standard data collection methods). The species richness (SR), species heterogeneity (H′) and species evenness (J) of the macrobenthic fauna in each reservoir were calculated, and the abundance and water quality data analysed using ANOVA and PCA as appropriate. A total of 13 macrobenthic taxa (Glyphidrilus sp., Limnodrilus socialis, Dero sp., Stratiomyd larva, Chironomid larva, Bellamya sp., Melanoides tuberculata, Gyraulus sp., Lymnaea sp., Paludomus sp., Thiara sp., Ancylus sp. and Mesostoma sp.) were observed from the six study reservoirs. The oligochaete tubificid worm L. socialis dominated the sediment samples, accounting for more than 94.7% of the total macrobenthic abundance, with the highest relative abundance of this species observed in Beira Lake (99.3%). The species richness of the macrobenthic community was highest in the Ihalagama and Kesbewa tanks (SR = 5), while it was the lowest in the Peralanda Tank (SR = 2). Since the benthic community was mainly dominated by L. socialis, the lowest species heterogeneity and species evenness values were observed in Beira Lake (H′ = 0.05; J = 0.03). The values of the water quality parameters among the study reservoirs varied, with Beira Lake exhibiting significantly high BOD5, dissolved nitrate, and total dissolved phosphate values (p < .05) than the other reservoirs, indicating a higher degree of eutrophication. Furthermore, the SR, J and H′ values for the study reservoirs decreased with increasing BOD5, dissolved nitrate and total dissolved phosphate levels. Thus, it was concluded that the abundance and diversity of macrobenthic fauna are primarily governed by water quality parameters. Furthermore, L. socialis can be used as a potential bioindicator organism in water quality assessment programs in urban reservoirs.

A model for tubificid worm (Tubifex tubifex) production and its effect on growth of three selected ornamental fish

. The demand for sludge worms, Tubifex tubifex is increasing with the growth of aquaculture as low-cost live feed in hatcheries and ornamental fish nurseries. The study was conducted to determine the optimal culture medium for T. tubifex worm’s production and to find out the inclusion effects of worms as feed on ornamental fish rearing. Three media-based treatments (T-1: mustard oil cake 20%, wheat bran 10%, soybean meal 10%, rice bran 20%, cow-dung 20%, sand 10%, fish pond mud 10%; T-2: mustard oil cake 10%, wheat bran 10%, soybean meal 10%, rice bran 10%, straw 5%, fish scale, stomach and fin 25%, cow-dung 20%, fish pond mud 10% and T-3: cow-dung 75%, sand 15%, fish pond mud 10%) with three replications of each were used to culture the worms for 100 days in nine cemented culvert system (160×25×10 cm3). The growth performance of three popular ornamental fishes koi carp (Cyprinus carpio), comet goldfish (Carassius auratus auratu) and goldfish (Carassius auratus) were determined by replacing the commercial feed at different level with tubificid rearing in fiberglass aquarium (45×30×30 cm3) for 32 days duration. Maximum yield (959.23 44.34 mg·cm-2) of tubificid biomass was recorded in T-2 (mustard oil cake-10%, wheat bran-10%, soybean meal-10%, rice bran-10%, straw-5%, fish scale, intestine, stomach and fin-25%, cow-dung-20%, mud collected from fish pond-10%) with a peak at day 70th. The fish fed with 50% commercial feed + 50% T. tubifex in TF-2 showed significantly (p<0.05) higher growth and survival performance than other treatments. The mean value of water quality parameters (i.e. temperature, pH and dissolved oxygen) were statistically insignificant (p>0.05) among the three treatments. Approximately 1.83 kg media were needed to produce 1.0 kg tubificid worm in treatment T-2. T-2 media is recommended as suitable media for commercial tubificid worm production and the inclusion of 50 % tubificid worms in the feed can be suggested for the ornamental fish rearing.

Benthos of Green Bay, Lake Michigan revisited after 40 years: A temporal update and assessment of environmental associations

Benthos of southern Green Bay, Lake Michigan have not been comprehensively examined since 1978. Since then, invasive species appeared, urbanization intensified, and restoration efforts were implemented, which likely altered the benthic macroinvertebrate community. Further, current benthos are subjected to dynamic factors including eutrophication, sedimentation, and periodic hypoxia. Understanding community responses to these anthropogenic stressors and natural habitat gradients is imperative to preserving biological integrity within Green Bay. Therefore, the objectives of this project were to describe the current macroinvertebrate community, examine changes since 1978, and assess the roles of productivity, substrate type, water depth, and hypoxia in structuring macroinvertebrate communities. Benthos were sampled at 197 stations, including 97 also sampled in 1978 by Markert (1982) and 100 that were added to increase spatial resolution. We collected 93 macroinvertebrate taxa in southern Green Bay with the community dominated by Chironomus and immature tubificid worms. Nonmetric multidimensional scaling (NMDS) ordination distinguished present and historical communities. Although oligochaete worms and chironomids remained dominant over time, Chironomus abundance increased and characterized the present community, whereas benthos were historically more diverse. The magnitude of temporal change varied spatially among zones of Green Bay, with larger differences concentrated in the Middle Bay and the Inner Bay remaining comparable to 1978. Present-day assemblages were most associated with the trophic gradient driven by Green Bay’s southernmost tributary, the Fox River, but also differed with substrate type and had similar structures in areas subjected to frequent hypoxia. Routine monitoring should continue to track changes while accounting for spatial effects.

EXTRAORDINARY PREVALENCE AND INTENSITY OF A PARASITIC NEMATODE IN TROUT AND WHITEFISH FROM THE DESCHUTES RIVER

In the spring and summer of 2020, we found cysts of the nematode Eustrongylides spp. in Brown Trout (Salmo trutta), Rainbow Trout (Oncorhynchus mykiss), and Mountain Whitefish (Prosopium williamsoni) in the Deschutes River. The prevalence and maximum intensity of infection exceeded the range of published accounts for Eustrongylides spp. across a wide range of species. Because the 1st intermediate host is likely to be a tubificid worm, also known as a sludge worm or sewage worm, this exceptional prevalence of Eustrongylides spp. infection raises questions about conditions in the river that may be contributing to the high infection rate in fish.

Effects of bioturbation by tubificid worms on biogeochemical processes, bacterial community structure and diversity in heterotrophic wetland sediments

Bioturbation activity of tubificid worms has been recognized as a key process influencing organic matter processing and nutrient cycling in benthic aquatic ecosystems. This activity is expected to modify benthic microbial communities by affecting the physical and chemical environment in sediments. Nevertheless, quantifications of bacterial community changes associated with bioturbation in freshwater ecosystems are still lacking. The present study aimed at evaluating the impact of tubificid worms on bacterial community structure using NGS approach (16S metabarcoding) and long (6 months) laboratory experiments on four heterotrophic wetland sediments. Worm bioturbation activity significantly stimulated biogeochemical processes at the water-sediment interface but only had a marginally significant effect on bacterial community structures. Yet, bacterial diversity was consistently reduced in presence of worms. Such decrease could be associated with the stimulation of organic matter mineralization by worms, leading to a reduction of the diversity of trophic niches available for bacterial species. The slight changes in bacterial community structures induced by bioturbation did not appear to control biogeochemical processes. Thus, the stimulation of biogeochemical processes by worm bioturbation was more associated with a stimulation of the initial bacterial community than with a drastic change in bacterial communities induced by worms.

Effects of Macrofaunal Recolonization on Biogeochemical Processes and Microbiota—A Mesocosm Study

Macroinvertebrates are widespread in lake sediments and alter sedimentary properties through their activity (bioturbation). Understanding the interactions between bioturbation and sediment properties is important given that lakes are important sinks and sources of carbon and nutrients. We studied the biogeochemical impact of macrofauna on surface sediments in 3-month-long mesocosm experiments conducted using sediment cores from a hypoxic, macrofauna-free lake basin. Experimental units consisted of hypoxic controls, oxic treatments, and oxic treatments that were experimentally colonized with chironomid larvae or tubificid worms. Overall, the presence of O2 in bottom water had the strongest geochemical effect and led to oxidation of sediments down to 2 cm depth. Relative to macrofauna-free oxic treatments, chironomid larvae increased sediment pore water concentrations of nitrate and sulfate and lowered porewater concentrations of reduced metals (Fe2+, Mn2+), presumably by burrow ventilation, whereas tubificid worms increased the redox potential, possibly through sediment reworking. Microbial communities were very similar across oxic treatments; however, the fractions of α-, β-, and γ-Proteobacteria and Sphingobacteriia increased, whereas those of Actinobacteria, Planctomycetes, and Omnitrophica decreased compared to hypoxic controls. Sediment microbial communities were, moreover, distinct from those of macrofaunal tubes or feces. We suggest that, under the conditions studied, bottom water oxygenation has a stronger biogeochemical impact on lacustrine surface sediments than macrofaunal bioturbation.

Aquatic Oligochaeta (Annalida:Clitellata) as Bio Indication for Sediment Quality Assessment in Tigris River Within Baghdad City /Iraq

Aquatic Oligochaeta is an important group of Macroinvertebrates that has been very remarkable as bioindicators for assessing water pollution and determining its degree in water bodies. Hence, the idea of the current study aims at studying the impact of Baghdad effluents on the Tigris River by using oligochaetes community as bioindicators . For this purpose, four sites along the inside of Baghdad has been chosen. Site S1 has been located upstream, site S2 and S3 has been at midstream and site S4 at the downstream of the River.This investigation has used different types of biological indicators, including the percentage of oligochaeta within benthic invertebrates, which ranged from 49.2-51.28%. The highest percentage of the tubificid worms in the benthic samples has been 26.95% and recorded at S4, while the lowest percentage has been 14.45% recorded at S1. Pollution index D ranged between 0.34 and 0.52. The highest value of the ratio of oligochaeta to Chironomidae larvae has been 3.5 recorded at S4, while the lowest value has been 2.6 reported at S1. The percentage of L. hoffmeisteri within the oligochaetes community has been from 35-56%. The highest value of biological quality index Io has been 9.89 recorded at S1, and the lowest value has been (5.57) recorded in S4. A Composite index of Biological quality (Eo) index recorded as C5 in S1 and C4,D3 and E3 in the other sites. Oligochaeta index of sediment bioindication (IOBS) values ranged between 2.55 at S1 and 1.15 at S4. The tubicid index of sediment TUSP reported at d the highest value (52.57%) at S4 where as the lowest value has been 28.68% at S1. The highest species richness value has been 7.35 recorded at S1 and the lowest value has been 6.12 at S3. Shannon- Weiner diversity index (H) ranged from 0.06-0.049 Bit/ind. Species uniformity index (E) has been 0.018-0.016.It is clear from the results that most of the biological indices indicate that the Tigris River sediment has been slightly impacted by anthropogenic activity during its passage through the Capital Baghdad. S1 is considered as a reference site, as it has presented the first point of entry of the Tigris River to Baghdad and then the sediment gradually has become polluted to reach its highest degree in the last site S4 after passing through several slightly polluted sites.

Development of Induced Breeding Technique for Freshwater Fish Gobi, Glossogobius giuris (Hamilton, 1822) Using Pituitary Gland (PG) Extract

This study aimed to establish induced breeding technique of freshwater fish gobi (Glossogobius giuris), using the pituitary gland (PG) extract. Six experiments were conducted at the Department of Fisheries Biology and Genetics, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh. First breeding trial was conducted in June using 40, 45, and 50 mg PG kg-1 body weight of the female fish. None of the fish was ovulated in the 1st trial. Two more breeding trials were conducted in July and August, using 6 mg (T1), 8 mg (T2) and 10 mg (T3) PG kg-1 body weight of female, and 3 mg (T4), 4 mg (T5) and 5 mg (T6) PG kg-1 body weight of male fish. After treatment, the ovulation rates were recorded as 56.33±1.53, 82.67±2.52 and 75.33±1.53% in July and 58.00±2.65, 94.67±1.53 and 78.33±1.53% in August under the treatments T1, T2 and T3, respectively. Hatching rates of eggs were observed as 52.00±4.36, 81.67±3.21 and 72.33±6.03% in July, and 54.67±3.23, 91.67±3.06 and 73.67±5.13% in August under the T1, T2 and T3, respectively. Hatching time was ranged from 35 to 48 h and after the absorption of yolk sac (60-72 h), they were survived well when fed with tubificid worms and mixed zooplankton. The female treated with the dose of 8 mg PG kg-1 body weight in August showed the best performance so far as the ovulation, fertilization and hatching rates were concerned, while the single dose of 4 mg kg-1 body weight of PG was found to be effective for male fish in both months. The findings obtained from the present study reveals that induced breeding of G. giuris, using PG extract is successful for large scale production of quality seed in captive condition, which would further facilitate towards the aquaculture production and biodiversity conservation of this important fish species to a greater extent.

The Effect of Tubificid Bioturbation on Vertical Water Exchange across the Sediment–Water Interface

The bioturbation activity of macroinvertebrates can affect the level of water exchange across the sediment–water interface. The impact of tubificid worm with different densities on the vertical water exchange at the sediment–water interface was investigated based on laboratory flume experiments. Vertical water fluxes, as well as physiochemical parameters, were measured at seven-day intervals, and the maximum penetration depths were obtained by dye injection before and after the tubificid bioturbation experiment, respectively. The bioturbation effects can be summarized in two aspects: (1) when the density was less than (or equal to) 20 individual/10 cm2, the volume of vertical water exchange positively correlated with the tubificid bioturbation. Once the density exceeded (or equaled) 25 individual/10 cm2, the vertical water flux decreased with increasing tubificid bioturbation. After 14 to 21 days, a negative correlation was identified between the bioturbation and the vertical water flux under all biological densities. (2) The maximum depth that the surface water can penetrate the sediment increased with increasing tubificid density. These results revealed that the vertical water was closely related to the biological density. The study has certain reference significance to understanding the spatiotemporal heterogeneity of hyporheic water exchange on a local scale.

The influence of bioturbation and water column oxygenation on nutrient recycling in reservoir sediments

Sediments are sinks of nutrients in reservoirs, but may also act as temporary nutrient sources to the water column, leading to eutrophication during the warm season. Several abiotic and biotic factors at the water–sediment interface are known to influence the role of sediments as temporary nutrient sources. This study aimed at quantifying the effects of two factors (i.e., oxygenation and bioturbation) on fluxes of nutrients from the water–sediment interface of the reservoir. An experimental approach was developed in the laboratory to test three fauna conditions (no fauna, presence of tubificid worms, and chironomids larvae) and three conditions of water column oxygenation (aerobic, fluctuating, and anaerobic conditions). Chironomid larvae significantly increased concentrations of N (NH4+ + NO3−) and PO43− released from sediments by 3.7-fold and by 17-fold, whereas tubificid worms had a lesser effect (twofold for N and threefold for PO43−). Anaerobic conditions increased N by 56-fold and PO43− by 102-fold compared to the aerobic treatment. Thus, anaerobic conditions produced greater N and P fluxes than fauna. Nevertheless, fauna and anoxic conditions at the water–sediment interface should not be neglected when quantifying the role of sediments on nutrient dynamics in lakes and reservoirs.

Effects of Wetting Media Cattle Blood, Rice Gruel and Water on the Yield and Amino Acid Composition of Tubificid Worms

The effects of three wetting media (cattle blood, rice gruel and subsurface clean water) of the culture media ingredients (a mixture of mustard oil cake, soybean meal and mud) on the yield and amino acid composition of tubificid worms cultured on a pilot scale in a fish farm for 42 days were evaluated. The worm yields were in the order: cattle blood wetted media (683.68 ± 3.86 mg/cm2), rice gruel (615.63 ± 3.66 mg/cm2), water (584. 38 ± 1.41 mg/cm2). Lysine, arginine and leucine were the most prevalent of the eight essential amino acids in worms cultured in the media wetted in cattle blood medium. The results suggested that a mixture of 40% mustard oil cake, 30% soybean meal and 30% mud can be used for the commercial culture of tubificid worms as live fish food. The tubificid worms showed high level of amino acids suitable for fish that require a high content of dietary amino acids.
 Asiat. Soc. Bangladesh, Sci. 45(2): 229-239, December 2019

A Test in a High Altitude Lake of a Multi-Parametric Rapid Methodology for Assessing Life in Liquid Environments on Planetary Bodies: A Potential New Freshwater Polychaete Tubeworm Community

On our planet, aqueous environments such as deep sea or high-altitude aphotic lakes, subject to present or past volcanic activity and active deglaciation, may provide analogues to the aqueous environments found on such planetary bodies as Europa, Titan or Enceladus. We report here methodologies and technologies tested in Laguna Negra, a high altitude lake in the Central Andes, Chile, for exploring and assessing the presence of life within planetary lakes or interior oceans. We adopted a multi-parametric Rapid Ecological Assessment (REA) approach centered around collecting video imagery (by an Underwater Imaging System) and sampling benthic sediments (for sedimentological, biological and geochemical analysis) to depths of 272 m, to complement physico-chemical sampling of the water column and collection of shallow sediments for microbiological analysis (reported in separate publications). This enabled us to classify and assess the apparent status of benthic habitats, based on substrata and environmental characteristics, together with floral and faunal community characteristics and bioturbation artifacts. Videos imagery showed that the lower water column was characterized by a variably intense sestonic flux of particles and debris among which were planktonic organisms such as ostracods, copepods and possibly cladocerans. Sediment analysis revealed at all depths abundant diatom frustules, mainly of an acidophile pennade diatom Pinnularia acidicola, amid vegetal debris likely originating from littoral macrophytes. Video imagery showed that the lakebed was partly covered by microbial mats and depositional matter and harboured an unexpectedly rich assortment of macrofauna, including sponges, tubificid worms, flatworms, bivalves and crustaceans. Various forms of bioturbation were also encountered, some with the animals in the tracks. Most notably, at the deepest site, a previously undescribed faunal feature was evident, apparently formed by a mat-like community of several layers of what appeared to be polychaete tubeworms, possibly of the family Siboglinidae. It is hypothesized that the hydrothermal activity observed in the region may supply the compounds able to support the deep-water microrganisms from which such tubeworms typically gain sustenance. Such processes could be present on other deep and aphotic liquid-water-bearing planetary bodies.