Burrowing Activity Research Articles

Burrow occupation rates and spatial distribution within habitat of the ghost crab Ocypode quadrata (Fabricius, 1787): Implications for impact assessments

The most conspicuous characteristic of ghost crabs (Crustacea: Ocypodidae) is the construction of semi-permanent burrows on the sand, widely used as tools for impact assessments. Thus, it is now critical to understand the factors driving burrowing activity and burrow occupation rates, including the effects of natural and anthropogenic disturbances. We tested three hypotheses in the present study with the ghost crab Ocypode quadrata: (i) overestimation of population size by traditional burrow counts depends on disturbance level at local scale; (ii) burrow occupation rate is density-dependent; and (iii) the predominant spatial distribution of burrows within the habitat is uniform. The last two predictions were assessed using a meta-analysis for a macro scale assessment. The comparison of distinct methods for burrow counting confirmed that ghost crab density is overestimated on non-urbanized beaches at local scale. A non-linear relationship between burrow occupation rates and burrow density was found at local and regional scales. When burrow density increases, the burrow occupation rate is also higher. However, from approximately 20 to 30 burrows/100 m2, the occupation rate reduces with increased density. Thus, the overestimation of the ghost crab density on non-urbanized beaches can be partially explained by a density-dependence in burrowing activity probably driven by a stronger intraspecific competition on non-urbanized areas. Finally, the distribution pattern of the ghost crab is predominantly uniform in most of its distribution range, despite of urbanization level and sampling design, hence suggesting intra-specific interactions as a driver of burrowing behaviour. In conclusion, burrow density, occupation rate and spatial distribution within the habitat evidenced at various spatial scales that burrowing activity of the ghost crab is density-dependent and this constitutes an issue never considered before in impact assessments inherent to coastal monitoring and management.

Using indirect methods to estimate population parameters of the Atlantic ghost crab from beaches in Northeastern Cuba

Sandy beaches are dynamic systems that harbor diverse macrofauna species, such as the ghost crab Ocypode quadrata, which has a wide distribution and it is considered useful in ecological evaluations. Population parameters of O. quadrata based on indirect methods were assessed at four tourist sandy beaches at northeastern Cuba from September 2010 to August 2011. Monthly samplings were carried out early in the morning. At each beach, five cross-shore transects were set at 50–60 m intervals, and consecutively 2x2 m quadrats were set from the upper swash level to the landward edge. Active burrows were counted and measured to the nearest millimeter using a caliper. Burrow density showed differences among beaches and a negative relation to the number of visitors. Burrow size showed differences among beaches as well as a positive relation to temperature, and non-significant relations to salinity and number of visitors. Burrow size frequency distribution showed a unimodal pattern skewed toward smaller sizes at the four beaches. Growth rates ranged from 0.57–1.4 year−1 and the growth performance was high (Φ′>3) at the four beaches. Growth performance was compared with other ocypodid populations (Uca spp., O. quadrata and Ucides spp.) inhabiting tropical coastal ecosystems using an auximetric plot. All ocypodid populations clustered forming one single ellipsoid in the auximetric plot supporting the use of borrows count and size as a reliable, non-invasive method to estimate population dynamics of this indicator species.

Using vermiwash to enhance performance of small-scale vermifiltration for swine farm wastewater.

Pollution caused by swine wastewater is a growing concern in many countries. In the developing countries, swine wastewater is not properly collected and treated, the wastewater from swine farm pollutes the ecosystem. Especially for small swine farms, they could not afford to have wastewater treatment system. Therefore, farmers need cheap, sustainable technology for future mixed farming. Vermifiltration by earthworm has been introduced to be an answer for enhancing wastewater treatment. Vermiwash is the liquid gathered from vermicomposting that has high microbial activities and nutrients. This study was carried out on a small pilot scale to investigate swine wastewater treatment efficiency of vermifiltration system with and without vermiwash and compared with the geofiltration system. Vermiwash was incubated in vermifiltration and geofiltration systems for 1week before the treatment. The result showed improved efficiency of vermifiltration incubated with vermiwash in swine wastewater treatment for biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) removal, which was highest followed by vermifiltration without incubated vermiwash, geofilter incubated with vermiwash and geofilter, respectively. Good performance of vermifiltration incubated with vermiwash compared with the geofilter treatment was demonstrated for removal of BOD (91.29 ± 9.89%, n = 10), COD (91.42 ± 6.34%, n = 10) and TSS (86.02 ± 10.45%, n = 10). Furthermore, the burrowing activity of the test earthworm (Eisenia fetida) promoted the aeration condition in vermifilter which led to more dissolved oxygen (DO) in effluent (61.28 ± 20.05%, n = 10). Moreover, the amount of copper (Cu) in effluent was decreased compared with influent by up to 88% in all treatment. After 10weeks of the experiment, the vermicompost that was incubated with vermiwash and produced from earthworm on the top layer was analyzed and showed that nutrients (nitrogen, phosphorus) and soil organic carbon were increased with vermifilter treatment (47.65, 81.61 and 31.79%, respectively) compared with geofilter treatment. In addition, bioavailability of Cu in soil in form of exchangeable Cu was decreased by increasing the bound to organic matter fraction. Transformation of Cu during vermifiltration happened and alleviated the mobility and availability of Cu. Copper in exchangeable form can change into non-toxic form. Therefore, vermifiltration process incubated with vermiwash could reduce the dispersion of copper in swine waste. In conclusion, vermiwash could enhance performance of vermifiltration for swine farm wastewater treatment. The available fraction of copper in vermicompost produced from vermifiltration decreased. Therefore, the farmer could produce vermicompost as the biofertilizer for agricultural production. Using vermifiltration for wastewater treatment in small swine farm could be the eco-solution for nutrient recovery, water resource recycles and minimize pollution.

Depth distribution of soil organic matter and burrowing activity of earthworms—mesocosm study using X-ray tomography and luminophores

Earthworms feed on organic matter present at the soil surface or within the soil. Thus, its distribution in the soil profile is likely to greatly influence earthworm behavior and, in turn, their burrow system. To test this idea, two anecic and two endogeic earthworm species were introduced into repacked soil cores (depth = 30 cm) upper half filled with a top soil containing 4% organic matter (0–15 cm) and lower half filled with a deep soil at 2% organic matter (15–30 cm). Earthworm behavior was studied using X-ray tomography combined with luminophores (colored particulate tracers of 63–125 μm size) placed at 0, 3, and 12 cm depth, a method widely used in sediment ecology. We observed that anecic and endogeic earthworms had contrasting reactions to the conditions with only endogeic species burrowing more intensively in the upper part. From a quantitative point of view, only a few percent of luminophores were displaced. However, luminophore displacements also provided qualitative information to complement the tomography: (i) endogeic species and especially Aporrectodea caliginosa bioturbated the most soil close to the surface (3 cm depth) and (ii) the two anecic species influenced the luminophore distribution differentially with Lumbricus terrestris displacing significantly more luminophores, whatever their initial depth, than Aporrectodea nocturna due to intense surface cast activity. Beyond methodological developments, our study found that endogeic earthworms burrow more in zones with higher organic matter contents and this explains why they are mainly found close to the soil surface in non-tilled soils.

Behavior and respiration responses of the earthworm Eisenia fetida to soil arsenite pollution

Soil arsenic (As) pollution from mining and industrial sources is a serious issue in China. Earthworms are considered ecosystem engineers and contribute to soil fertility development and maintenance of soil physico-chemical properties. In this study, earthworms were exposed to soils with different sodium arsenite concentrations (0, 5, 20, and 80 mg As kg-1) for 60 d to investigate the changes in soil properties and the responses of the earthworms (e.g., burrowing activity and respiration). Earthworm burrowing activity decreased with increasing arsenite concentrations, and earthworm respiration was significantly lower in soils with 20 and 80 mg As kg-1 compared to 0 mg As kg-1. Changes in soil properties were also observed after incubation of As-amended soil with earthworms. Specifically, soil pH decreased, while soil electrical conductivity and contents of soil NO3– -N, Olsen-P, and available K increased. Our results suggest that arsenite negatively impacts the metabolic activity of earthworms, leading to reduced burrowing activity, which in turn modifies the effects of earthworms on soil fertility and remediation.

EUROPEAN BADGER (MELES MELES LINNAEUS, 1758) PREFERENCES TO THE TERRAIN EXPOSURE FOR DIGGING DENS IN SOUTHEASTERN BULGARIA

A total of 47 active badger burrows in the Southeastern Bulgaria were described in order to find whether there are preferences to terrain exposure for its digging activity. The most of the dens were found on terrain with south exposure - 23.4%, followed by these on the east and west side -19.15% each. The dens faced to these three directions, together with these to intercardinal directions connected with south, represented 80.85% of the active badger dens found. A tendency in the preference of the European badger to the southern exposure of the terrain for its digging activity in the region of South-eastern Bulgaria was established.

Sediment selection: range-expanding fiddler crabs are better burrowers than their historic-range counterparts

Climate change plays a large role in driving species range shifts; however, the physical characteristics of an environment can also influence and alter species distributions. In New England salt marshes, the mud fiddler crab Minuca pugnax is expanding its range north of Cape Cod, MA, into the Gulf of Maine (GoM) due to warming waters. The burrowing lifestyle of M. pugnax means sediment compaction in salt marshes may influence the ability of crabs to dig, with more compact soils being resistant to burrowing. Previous studies indicate that salt marshes along the GoM have a higher sediment compaction relative to marshes south of Cape Cod. Physical characteristics of this habitat may be influencing the burrowing performance of M. pugnax and therefore the continuation of their northward range expansion into the GoM. We conducted a controlled laboratory experiment to determine if compaction affects the burrowing activity of M. pugnax in historical and range-expanded populations. We manipulated sediment compaction in standardized lab assays and measured crab burrowing performance with individuals collected from Nantucket (NAN, i.e. historical range) and the Plum Island Estuary (PIE, i.e. expanded range). We determined compaction negatively affected burrowing ability in crabs from both sites; however, crabs from PIE have a higher probability of burrowing in higher sediment compactions than NAN crabs. In addition, PIE crabs were more likely to burrow overall. We conclude that site level differences in compaction are likely altering burrowing behavior in the crab’s expanded-range territory by way of local adaptation or phenotypic plasticity.

Burrow use by bilbies in temperate South Australia

Remnant natural populations of greater bilbies (Macrotis lagotis) are confined to the Australian arid zone where bilbies construct and shelter in multiple burrows within their home range. We investigated burrow use behaviour of bilbies in a translocated population in temperate southern Australia to determine if behaviour differed in this climatic zone. Over a 12 month period, 43 adult bilbies at Venus Bay Conservation Park were spool-and-line tracked to 118 burrows. Active burrow density was 0.55 per ha, and bilbies at the site used multiple burrows (up to 13 for males and 8 for females) and regularly moved between diurnal burrows. Male bilbies had significantly larger burrow ranges (10.2 ± 5.8 ha, MCP100, mean ± s.d.) than females (2.6 ± 1.8 ha), and were similar in size to those recorded in an arid zone population. Males’ burrow ranges tended to overlap with the burrow range of multiple other males and females. The density of burrows in the current study suggests that bilby burrows were likely to have been a common landscape feature within the southern parts of the species range prior to their local extinction. Further research is needed to determine the impact of the loss of bilby burrows from southern Australia on other burrow commensal species.

Changes in coastal Gopher Tortoise (Gopherus polyphemus) burrow characteristics and density following hurricane events in Northeast Florida, USA: Implications for conservation planning

The Gopher Tortoise, Gopherus polyphemus is iconic, yet threatened throughout its range in the southeastern United States. It is a burrowing, herbivorous tortoise whose upland habitats have been greatly reduced by habitat destruction, fragmentation and/or reduction in quality due to anthropogenic changes in the disturbance regimes, such as fire, that are necessary to maintain quality habitat. Importantly, Gopher Tortoises are well documented keystone species supporting numerous conspecifics that are dependent upon or regularly use their burrows.While this species has been much studied in its inland habitats, it also thrives in coastal sand dune environments where little is known about its behavior, ecosystem role or conservation status. Coastal natural areas in the state of Florida, USA have been significantly reduced by human activity, and are now additionally threatened with accelerated sea level rise and more frequent and intense storms.We collected Gopher Tortoise burrow location, abundance, width and activity data in 2016 for a coastal population within northeast Florida, protected within the northern component of the Guana Tolomato Matanzas National Estuarine Research Reserve. Soon after our burrow survey was completed in 2016, Hurricane Matthew heavily impacted our study area that fall. In order to determine the degree to which this Gopher Tortoise population might have been impacted by the hurricane, we began re-surveying burrows in 2017 but were interrupted by another Hurricane, Irma, in 2017. We completed the post-hurricanes burrow surveys in 2018.When comparing pre-and post-hurricanes surveys, we found that habitat was lost and burrow density increased. The relative proportion of burrows categorized as “active” increased, while “inactive” and “abandoned” burrows decreased. Furthermore, burrow abundance decreased by 10% following these back-to-back hurricane events.We infer that individual Gopher Tortoises mostly abandoned low elevation burrows at risk of hurricane-related storm surge and relocated to higher elevation, unused (or “inactive” and “abandoned”) burrows. Such relocation, combined with significant loss of previously inhabited lower elevation habitat could explain the post-storm increase in burrow density and the proportional changes in burrow activity classification.However, as resilient as this population may be, it is running out of room due to sea level rise and habitat loss and fragmentation. Such implications for this and other species should be considered in conservation planning for coastal species of concern.

Chemical control of rodents and its impact on rodent infestations during subsequent cropping season

The control of rodent pests with novel rodenticides is an important strategy subsequently they are cost-effective in reduction of agriculture damage in the urban environment. The current field study was conducted to test the efficiency of newly formulated baits of zinc phosphide (2%) and brodifacoum (0.005%) in combination and alone mixed with additives for the control of field rats prevailing wheat-groundnut cropping system of the Pothwar region, Pakistan. Burrow baiting and bait stations were employed at the early flowering stages of the respective crops, and continued through three growth stages (germination, peg formation/flowering and maturity). Treatment efficacy of the trials was assessed through counts of active rodent burrows before and after treatments at the three growth stages of these crops. The results indicated variable degrees of reduction in burrow activities following the three bait applications. The reductions in rodent activity in wheat were 88.8% at germination, 92.0% at flowering/grain formation and 95.5% at maturity stage. In groundnut, the rodent activities were reduced by 91.8%, 93.5% and 95.8% at germination, peg formation, and maturity stages, respectively. The estimated mortality at all three growth stages of both wheat and groundnut ranged between 60 and 85%. A significant impact of three rodenticides treatments on the reduction of rodent burrow density in both wheat and groundnut crops (P < 0.05) was observed. Nonetheless, comparison of the mean values reveals that the number of burrows reduced at the maturity stages (P > 0.05). The results revealed that this combination of rodenticides have more potential in enhancing bait acceptance and could be benefit to the agricultural ecosystem and may reduce the impact of secondary poisoning and environmental risks.

REVIEW ON THE ROLE OF EARTHWORMS ON HILLSLOPE HYDROLOGY AND SOIL EROSION WITH SPECIAL REFERENCE TO DANUM VALLEY, SABAH, MALAYSIA

Hydrological routes exist through active burrowing of soil fauna, and in numbers improve soil drainage systems. Earthworms are of particular interest because their presence is known widely to increase infiltration and reduce erosion rates by creating macropores and stable casts. Ideally during non-extreme rainfall events on flatlands, earthworm macropores lengthens the time prior to soil surface saturation thus slowing down occasions of overland flow resulting in runoff. Hypothesizing similar effects on hillslopes with gradients can be misleading whereas laboratory experiments which try to recreate and simulate field consistency cannot match the natural soil architecture which is vital in the dissection of the many bio-geophysical processes involved in the rainfall-runoff process. This review paper aims to summarize past studies conducted around the world and highlighting possible gaps on earthworm’s studies related to hillslopes and erosion.

Analysis of Animal Well-Being When Supplementing Drinking Water with Tramadol or Metamizole during Chronic Pancreatitis.

Simple SummaryPain management during in vivo experiments can considerably improve the wellbeing of animals. However, often it is not clear, which drugs are best for the animals and how to apply these drugs without causing stress. In this study, we evaluated mice when metamizole or tramadol was provided via drinking water. Neither of these two drugs reduced the amount of consumed water or body weight in healthy mice or influenced their natural behavior, such as nest building or burrowing activity. Both analgesics were then given to mice suffering from chronic pancreatitis. Mice drinking tramadol supplemented water, at some time-points, experienced less loss in body weight and consumed more water than mice drinking metamizole. However, no major differences in other methods measuring wellbeing of mice was observed. In conclusion, both analgesics can be used during chronic pancreatitis, but tramadol seems to be moderately advantageous when compared to metamizole.Pain management during in vivo experiments is an animal welfare concern and is in many countries also legally required. In this study, we evaluated C57Bl/6J mice when 3 g/L metamizole or 1 g/L tramadol was provided via drinking water, before and during cerulein-induced chronic pancreatitis. Supplementation of drinking water with metamizole or tramadol did not significantly reduce the amount of consumed water. In order to evaluate the wellbeing of mice, a distress score, burrowing activity, nesting behavior, and body weight was assessed. Before induction of pancreatitis, neither tramadol nor metamizole influenced these readout parameters. Chronic pancreatitis caused a significantly increased distress score, decreased burrowing activity and a reduction in body weight. Mice drinking tramadol-supplemented water experienced less loss in body weight and consumed more water than mice drinking metamizole, at a few time-points during chronic pancreatitis. Pancreatic atrophy, a characteristic feature of chronic pancreatitis was not differentially influenced by either analgesic. In conclusion, both analgesics can be used during 33 days of chronic pancreatitis, but tramadol seems to be moderately advantageous when compared to metamizole.

Bioturbation by endogeic earthworms facilitates entomopathogenic nematode movement toward herbivore-damaged maize roots

Entomopathogenic nematodes (EPNs) have been extensively studied as potential biological control agents against root-feeding crop pests. Maize roots under rootworm attack have been shown to release volatile organic compounds, such as (E)-β-caryophyllene (Eβc) that guide EPNs toward the damaging larvae. As yet, it is unknown how belowground ecosystems engineers, such as earthworms, affect the biological control capacity of EPNs by altering the root Eβc-mediated tritrophic interactions. We here asked whether and how, the presence of endogeic earthworms affects the ability of EPNs to find root-feeding larvae of the beetle Diabrotica balteata. First, we performed a field mesocosm experiment with two diverse cropping systems, and revealed that the presence of earthworms increased the EPN infection potential of larvae near maize roots. Subsequently, using climate-controlled, olfactometer-based bioassays, we confirmed that EPNs response to Eβc alone (released from dispensers) was two-fold higher in earthworm-worked soil than in earthworm-free soil. Together our results indicate that endogeic earthworms, through burrowing and casting activities, not only change soil properties in a way that improves soil fertility but may also enhance the biocontrol potential of EPNs against root feeding pests. For an ecologically-sound pest reduction in crop fields, we advocate agricultural practices that favour earthworm community structure and diversity.

Evaluating the use of a low dose fipronil bait in reducing black-tailed prairie dog (Cynomys ludovicianus) fleas at reduced application rates.

Plague is a virulent zoonosis, vectored by fleas, posing danger to black-tailed prairie dogs (BTPDs) (Cynomys ludovicianus), black-footed ferrets (Mustela nigripes), and humans in North America. During prior research, a fipronil grain bait (0.005%) applied at rates of 1-½ cup/burrow, reduced flea abundance by > 95–100% when applied three times February–March in northern Colorado. The objective of the current study was to determine the efficacy of fipronil bait against fleas in northern Colorado at reduced application rates (½ cup/burrow) and frequencies (1–2 applications). The field study was conducted in Larimer county, Colorado USA between June-November 2018. Three test plots were selected: two treatment plots (1 vs. 2 fipronil bait applications) and one untreated control. Fipronil was applied at a rate of ½ cup (~95 g)/burrow. Fleas were collected from captured BTPDs and swabs of active burrows prior to bait application and up to 134-days post-treatment. A total of 203 BTPDs and 210 active burrows were sampled. Within the treatment plots, no fleas were collected from BTPDs up to 134-days post-treatment (100% efficacy). Five fleas were recovered from burrows within the one-application plot (<40-days post-application) with efficacy ranging from 97.1 to 100%. No fleas were recovered from burrows within the two-application plot. We caution that while fleas were present within the control plot throughout the study, abundances were low. The efficacy results are supported by those of prior field research conducted in South Dakota and suggest that fipronil bait may be applied at lower rates and frequencies than initially proposed, with potential to sustain flea removal >4-months.

Burrows of the common field-cricket Gryllus campestris Linnaeus, 1758 (Orthoptera: Gryllidae) from Dajti Mountain, Albania

Considerable studies of the univoltine, common field-cricket Gryllus campestris Linnaeus, 1758, known from sunny oligotrophic grasslands and heathlands of the western Palaearctic, were previously made, but none of them has shown the characteristics of its burrows. This paper presents a neoichnological study based on a group of G. campestris that lives in and around a pasture glade in Dajti Mountain, east of the Tirana District in Albania. It includes direct observations of the burrows in the field and their casts made by means of white Portland cement. Burrows of nymphs of G. campestris were observed to be tubular, sun-facing and have only one, funnel-like entrance, simple termination and no branches. This study is the first one showing morphological features of the burrows and the burrowing activity of the common field-cricket, being a contribution to ichnology of soils. Preservation of the burrows is possible by their filling, for instance by sand during flooding. The burrows do not fit to any existing ichnotaxa.

Sediment transport by the burrowing activity of snow vole (Chionomys nivalis) in subalpine prairies of the Parâng Mountains (Romania): Quantitative modelling and methodological perspectives

Over the last decades, animal activity has been explored and reported as a potential source of natural hazards, such as the destruction of a beaver dam potentially triggering a flash flood downriver. However, the sediment source or sediment budget related to animal activity has received very little attention from geoscientists to date. The main goal of this study is to quantify the biogenic activity of the European snow vole (Chionomys nivalis) as a sediment source in the subalpine prairies of the Parâng Mountains, Southern Carpathians. Only the direct action of this rodent was analyzed, namely the spatial distribution and frequency of burrowing, quantitative analysis of the mounds, and rate of sediment excavation and mass transfer caused by burrowing and tunnel digging. To do this, 838 burrows and mounds were mapped and measured in eleven plots, and excavated volumes of sediment and mass transfers were calculated following three approaches: 1) measuring the weight of excavated debris; 2) measuring the dimensions of excavated debris; and 3) measuring burrow dimensions. The fieldwork revealed three preferred aspects: south, southeast, and west. The amount of displaced soil was highly variable depending on the approach used, ranging from 3.41 m3/ha to 21.08 m3/ha. As such, snow vole biogenic activity, which is due to the long-term opening of the landscape for traditional transhumance and sheep farming, should be considered to be an important sediment source in the subalpine and alpine prairies of the Parâng Mountain.

Comparing distress of mouse models for liver damage

In order to foster animal welfare as well as high quality of research, many countries regulate by law that the severity of animal experiments must be evaluated and considered when performing biomedical research. It is well accepted that multiple parameters rather than a single readout parameter should be applied to describe animal distress or suffering. However, since the performance of readout parameters for animal distress is rarely defined and methods for multivariate analysis have only in rare cases been used, it is not known which methodology is most appropriate to define animal distress. This study used receiver operating characteristic curve analysis to quantify the performance of burrowing activity, body weight change and a distress score of mice after induction of liver damage by bile duct ligation or carbon tetrachloride. In addition, Support Vector Machine classification was used to compare the distress of these mouse models. This approach demonstrated that bile duct ligation causes much more distress than carbon tetrachloride-induced liver damage. This study, therefore, provides a prototype how to compare two animal models by considering several readout parameters. In the future these or similar methods for multivariate analysis will be necessary, when assessing and comparing the severity of animal models.

Earthworm Burrowing Activity and Its Effects on Soil Hydraulic Properties under Different Soil Moisture Conditions from the Loess Plateau, China

Earthworm activity has become more important in the Loess Plateau, where hydrological processes are crucial for ecosystem sustainability. In this study, we conducted a laboratory microcosm experiment to determine the various burrowing activities of Eisenia fetida and their impact on the soil hydraulic properties in response to different levels of soil moisture (50%, 70%, 90% of field capacity) in two common soil types (loessial and Lou soil) obtained from the Loess Plateau. Burrowing activity of E. fetida increased with higher soil moisture and was greater in loessial than in Lou soil. Most burrowing activities occurred within the top 5 cm and decreased with increasing soil depth. Macropores and burrow branching, which are highly related to the earthworm burrowing, were more prevalent in wetter soil. Earthworms significantly altered the formation of large soil aggregates (AGL, diameter &gt;2 mm) under different soil moistures and depths. Distinct earthworm burrowing activities, controlled by soil moisture, altered soil hydraulic properties. However, soil saturated hydraulic conductivity (Ks) showed little differences between different treatments due to the horizontal and high–branched burrows of E. fetida, although higher burrowing activities were found in wetter soil. Soil field capacity was highest in drier soil due to the less macropores and burrowing activities.

Contrasting Effects of Bioturbation Studied in Intact and Reconstructed Estuarine Sediments

Macrofauna can produce contrasting biogeochemical effects in intact and reconstructed sediments. We measured benthic fluxes of oxygen, inorganic carbon, and nitrogen and denitrification rates in intact sediments dominated by a filter and a deposit feeder and in reconstructed sediments added with increasing densities of the same organisms. Measurements in reconstructed sediments were carried out 5 days after macrofauna addition. The degree of stimulation of the measured fluxes in the intact and reconstructed sediments was then compared. Results confirmed that high densities of bioturbating macrofauna produce profound effects on sediment biogeochemistry, enhancing benthic respiration and ammonium recycling by up to a factor of ~3 and ~9, respectively, as compared to control sediments. The deposit feeder also increased total denitrification by a factor of ~2, whereas the filter feeder activity did not stimulate nitrogen removal. Moreover, the effects of deposit feeders on benthic fluxes were significantly higher (e.g., on respiration and ammonium recycling) or different (e.g., on denitrification) when measured in intact and reconstructed sediments. In intact sediments, deposit feeders enhanced the denitrification coupled to nitrification and had no effects on the denitrification of water column nitrate, whereas in reconstructed sediments, the opposite was true. This may reflect active burrowing in reconstructed sediments and the long time needed for slow growing nitrifiers to develop within burrows. Results suggest that, in bioturbation studies, oversimplified experimental approaches and insufficient preincubation time might lead to wrong interpretation of the role of macrofauna in sediment biogeochemistry, far from that occurring in nature.

Microclimate and distribution of mangrove soil carbon in mud lobster (Thalassina anomala Herbst 1804) mounds

Although the role of mud lobsters (Thalassina anomala Herbst 1804) in influencing mangrove succession, structure and soil chemistry has been given a great deal of attention, there are still large knowledge gaps. We are unable to incorporate mud lobsters into model of carbon dynamics. This study examines the variations of microclimate (temperature and light intensity) in mud lobster mounds. The effects of burrowing activity of mud lobster on carbon distributions were investigated by comparing the content of organic matter (SOM) and organic carbon (SOC) extracted from both mud lobster mound and surrounding mangrove soils in Sibuti Wildlife Sanctuary (Sarawak, Malaysia). Our study demonstrates that mud lobsters, with microclimate (light and temperature) variation, are spatially distributed along the seaward and landward intertidal zone of the Sibuti mangrove. The transport of soil from deeper in the soil profile to the soil surface by the mud lobster resulted in significantly higher SOM and total C in freshly excavated mud than in older mud in the mound of the mud lobster. The vertical distribution of SOM was not influenced by the behavior of mud lobsters and had a slight negative impact on total soil C. There was no substantial evidence that the activity of the mud lobsters in mangrove soils increased SOM and total C. Because mangrove soils are known to trap or store belowground C, the burrowing activities may be doing the opposite by releasing the stored C to the surface. While mud lobsters have not had a significant impact on C, other processes (e.g., regeneration, productivity, and subsidence) are highly affected and may therefore have indirect effects on soil carbon stocks. Information on the contribution of mud lobster mound activities to C distribution in mangrove environment would be critical for national carbon estimation.