Mud Substrate Research Articles

Habitat Partitioning among Three Sympatric Species of Map Turtles, Genus Graptemys

Three species of map turtles, genus Graptemys, were trapped in rivers, streams, and lakes of southeastern and south-central Kansas, and 32 environmental variables were measured at each trap site to compare overlap in habitat use among species. Graptemys ouachitensis and G. pseudogeographica were collected in rivers with abundant basking sites. However, G. geographica was found exclusively in shady streams over rock and gravel substrata. The three species had high habitat overlap index values, but discriminant analysis based on environmental variables separated them into distinct groups. Variables most useful in distinguishing among groups were, in order of decreasing discriminating power, percentage rock substratum, percentage bare shoreline, dissolved carbon dioxide, percentage mud substratum, per- centage shade, dissolved oxygen, pH, and stream width. Graptemys pseudogeographica was commonly found together with G. ouachitensis, but sites of co-occurrence were distinguishable from sites where only one of these species occurred.

Contributions of Abiotic and Biotic Factors to Settlement in Summer Flounder, Paralichthys dentatus

by both juvenile and metamorphic summer flounder for sand over mud substrate. Metamorphic individuals do not appear to be capable of burial in the substrate when they enter the estuary. Complete burial was only observed in late-metamorphic and juvenile stages. A diel pattern of burying behavior was observed and was dependent upon several environmental variables, including substrate, water temperature, tide, and the presence and type of predator, all of which may effect growth and survival during metamorphosis.

Silurian calymenid trilobite Alcymene n. gen., with new species from the Ludlow of Gotland, Sweden

Alcymene n. gen. comprises a monophyletic group of calymenids known from the Ludlow Series of Sweden and the British Isles. The sister species Alcymene alveus and A. lindstroemi n. gen. and spp. (Hemse Beds, Gotland, Sweden) are most closely related to the type species A. neointermedia (Richter and Richter), which occurs in overlying and underlying strata at nearby localities. Structural modification of A. alveus and A. lindstroemi, especially the development of a greatly broadened and troughed librigenal border, can be interpreted as “snowshoe” adaptations for increased stability on an offshore mud substrate.

Flute-Like Marks and Associated Structures from the Carboniferous Port Hood Formation of Eastern Canada: Evidence of Secondary Origin in Association with Sediment Intrusion

ABSTRACT Flutes have been described and interpreted for many years as sole marks, preserved in positive relief on the bases of sandstone beds, and formed on underlying firm mud substrates mainly by corrasion at the sediment/water interface by fluvial, tidal, or turbidity currents. Structures resembling flutes (herein termed flute-like marks, or FLMs) from fluvial sandstone of the Port Hood Formation (mid-Carboniferous) of western Cape Breton Island are present not only on the undersides, but also on the vertical, inclined, stepped, and top surfaces of sandstone beds in contact with mudstone bodies. These occurrences are difficult to reconcile with primary sedimentary processes, even allowing for complex and fortuitous preservation, e.g., by erosion of slumped mudstone bodies or as scoured and verturned mudstone boulders. The presence of associated soft-sediment deformation structures, such as convolute bedding, mudstone diapirs, and mud-injection structures, some of which also have flute-like marks on their surfaces, suggests that these structures are explained more readily by sediment intrusion (rheoplasis) than by current scour and infill. Since flute-like marks have been recognized as positive-relief structures on both upper and inclined mudstone-sandstone interfaces in modern tidal-flat environments and on experimental injection structures, we reemphasize that they should not be regarded as excellent criteria for indicating way-up and paleocurrent direction.

Spawning and Rearing Habitat Use by White Sturgeons in the Columbia River Downstream from McNary Dam

Spawning and rearing habitats used by white sturgeons Acipenser transmontanus were described from water temperature, depth, and velocity measurements and substrate types present at sites where eggs, larvae, young-of-the-year, and juveniles (ages 1–7) were collected. Spawning and egg incubation occurred in the swiftest water available (mean water column velocity, 0.8–2.8 m/s), which was within 8 km downstream from each of the four main-stem Columbia River dams in our study area. Substrates where spawning occurred were mainly cobble, boulder, and bedrock. Yolk-sac larvae were transported by the river currents from spawning areas into deeper areas with lower water velocities and finer substrates. Young-of-the-year white sturgeons were found at depths of 9–57 m, at mean water column velocities of 0.6 m/s and less, and over substrates of hard clay, mud and silt, sand, gravel, and cobble. Juvenile fish were found at depths of 2–58 m, at mean water column velocities of 1.2 m/s and less, and over substrates of hard clay, mud and silt, sand, gravel, cobble, boulder, and bedrock.

Distribution, density and specific composition of water mites (Acari) in the sublittoral of Lake Banyoles (Spain)

The seasonal and bathymetric occurrence of water mites in the sublittoral and profundal zones of lake Banyoles were studied in 1986-1987. Four species were found in the mud substrate : Neumania deltoides (Piersig, 1894), Neumania imitata Koenike, 1908, Unionicola crassipes (Muller, 1776) and Arrenurus sinuator (Muller, 1776). The maximum depth that water mites reached was 12 m, but they were more frequent and abundant at 5 m depth, mainly in the March-May period (41 individuals per m2 ). This group represents only 0.08-0.39 % of the total macrobenthic fauna in the sublittoral of lake Banyoles. N. deltoides is the most abundant and widely distributed species. For N. imitata this is the first record in the Iberian peninsula.

On bipedalism in skates and rays

The anterior crurae of the pelvic fins in rajids are limb-like; this paper shows that these rays use the crurae for bipedal locomotion on the bottom at speeds around one-third of a disc length per second. It is suggested that this ‘walking’ pattern is employed to feed on prey within the substrate; sting rays (which feed in a different manner) do not possess such crurae. ‘Walking’ on a mud substrate leaves a characteristic track pattern as the crural tips dig in to propel the ray forwards; such tracks should be recognizeable in the fossil record.

シオマネキのメガロパの飼育下における変態条件

The settling condition and metamorphosis of megalops of the mud fiddler crab Uca arcuata were studied on the basis of a series of laboratory experiments. All the megalops on the emerged substrate succeeded in the metamorphose, but those on the submerged substrate showed less than 20% metamorphosing success. When the mud and sand substrates were provided in the emerged condition, megalops settled to make their own burrows and metamorphosed only on mud. Five types of substrates with different grain size compositions were provided to test burrow making and metamorphosing success. The survival rate of megalops was not different over the whole substrate, but metamorphosing success was significantly higher in the muddier sediment, while no metamorphosis occured in the sandy sediment. When the chance to meet an adequate substrate was manipulated, the megalops extended their pelagic phase and kept their metamorphosing ability for 20 days after molting.

Occurrence and fruit and seed biology of Halophila tricostata Greenway (Hydrocharitaceae)

Halophila tricostata Greenway appears to be endemic to eastern Queensland, Australia, and occurs between 14�11'S and 23�45's. It was found at depths from 1.4 to 30 m in well sheltered habitats, including in shallow coastal sites near mangrove-lined estuaries, on the lee side of continental and coral- reef islands, and on some commercial prawn-trawling grounds within the Great Barrier Reef lagoon. It grows on predominantly fine mud substratum in small monospecific meadows or mixed with other tropical seagrasses, mostly other Halophila species. Field observations indicate that H. tricostata is an annual angiosperm and produces an estimated 70 000 seeds m-2 year-1. Halophila tricostata is dioecious. The plant has a horizontal rhizome bearing an erect shoot with eight to twelve nodes and a root at each rhizome node. Except at the first two or three nodes, the mature plants produce a reproductive organ at each node of their rarely branched erect shoot. The reproductive organs and fruits develop and mature acropetally along the erect shoot. There are 24-60 seeds, with a mean of 41 seeds, per fruit. The seed has a coiled embryo protected by a cotyledon, and an enlarged hypocotyl. The hypocotyl acts as a nutrient store and contains starch, protein and lipid. The seed covering consists of pericarp remains and two thin cuticular layers of seed coat. The surface of the seed covering has numerous fine protrusions. The seed covering becomes loose and is discarded during germination, exposing the hypocotyl. The surface of the hypocotyl develops hair-like unicellular structures during seedling development. The majority of the seeds begin to germinate at 26-28�C after two weeks of culturing, but germination is not synchronized. The culturing of H. tricostata seedlings beyond the three-leaf stage was not successful.

Rubbing behaviour of belugas, Delphinapterus leucas, in a high Arctic estuary

From about mid-July to mid-August belugas (Delphinapterus leucas) over five seasons spent from 27 to 38 days at Cunningham Inlet (74°05′N, 93°45′W), where maximum numbers in each of eight seasons varied from 762 to 1741. While in the estuary, whales actively rub all their skin surface on the mud, pebble, and sharp limestone substrate near shore. Rubbing behaviour is more frequent early in the period of estuarine occupation and is exhibited by all age-classes with the exception of neonates and their dams. Remains of skin found in the area are proof that the epidermal surface is cut and shed from the whales in the shallow areas of the inlet. Active abrasion of skin surfaces softened by exposure to warm fresh water is thought to accelerate the moult, which is linked to a seasonal endocrine cycle and synchronized to meet the energetic demands imposed by their environment.

The Effects of Food Availability and Foraging Constraint on the Life History of a Predatory Leech, Nephelopsis obscura

Two groups of Nephelopsis obscura, fed ad libitum on Tubifex tubifex, were compared : one was maintained in an environment with a mud substratum (MS leeches) allowing prey anti-predator responses, the other without a substratum (NS leeches) providing prey directy available to the leech. NS leeches showed a 4.7 times higher feeding rate and 3.7 times higher growth rate than MS leeches resulting in NS leeches attaining maturity at a mean size of 750 mg after 85 days compared to a mean size at maturity of 270 mg after 109 days for MS leeches

Contemporary sedimentary processes in the Monterey Canyon-fan system

A study of the Monterey Canyon and fan was conducted to investigate contemporary sedimentary activity using a camera sled, Alvin dives and Sea-Beam bathymetry. Physical characteristics and plan view morphology of the walls, terraces, thalweg floor and levees of the Monterey Canyon and fan, as well as the gullied and non-gullied regions of the adjacent continental slope have been studied. The canyon floor and fan valley thalweg channel from 2900 to 3500 m exhibited properties indicative of moderate to low energy conditions (weak currents, smoothed sea-bed, deposits of disintegrated kelp, bioturbated mud substrate, fecal pellets, absence of scour). Chemosynthetic communities consisting of clams and a pogonophoran, were found in the fan valley from 3000 to 3600 m. Local areas of rockfalls and slumps from the canyon and fan valley walls were not fresh (sedimented, abundantly colonized by benthic biota). Terraces and levee crests were mud-draped and bedrock exposures on canyon walls were encrusted by benthic organisms. Freshest disturbances were found in gullies on the adjacent continental slope where bedrock was scoured clean of sediment and loose debris. A major submarine slide detached from escarpments on the lower slope, and extends across the fan. The slide surface was mud-draped, hummocky, and contained bedforms with wavelengths up to 150 m and up to 10 m relief. The survey was conducted shortly before the Loma Prieta earthquake (October 17, 1989) that caused substantial ground motion in on-shore regions of Monterey Bay. Any substantial sub-sea disturbances generated by the ensuing earthquake should be discernable from the pre-earthquake state by comparison with the deep-sea photographs and observations.

The influence of substratum and water velocity on growth of Ranunculus aquatilis L. (Ranunculaceae)

This study investigated the combined influence of three different flow velocities (high, 22.6 cm s −1; medium, 11.0 cm s −1; low, below 2 cm s −1) and substrata (mud, sand and gravel) on the growth of Ranunculus aquatilis L. (measured as the ratio between the final and initial wet weight of plant shoots kept in wood boxes in the stream for 21 days). The results showed highest levels of growth in mud substrate at all velocities (1.5–3.9 times higher than in sand and gravel). Highest growth for plants in sand and gravel was observed at medium velocity. In sand, this was about 1.6–2.8 times higher than growth at low or high flows. In gravel, growth was about 1.2 times and 1.6 times higher than at low and high velocities, respectively. The experiment indicates that the substratum and water velocity have a combined influence on the growth of R. aquatilis, and that the relative importance of each depends on the interactions of the particular substrata and velocities. The specific mechanisms involved in this influence have not been determined, but it is suggested that both the nutrient content and the texture of the substratum play important roles.

The technical feasibility of pond liners for rearing Pacific white shrimp ( Penaeus vannamei) in terms of survival, growth, water exchange rate and effluent water quality

Three trials were conducted to investigate the technical feasibility of pond liners. The trials compared the survival and growth of the Pacific white shrimp, Penaeus vannamei, on plastic, sand and clay/mud substrates. The first 8-week trial, at the Texas Agricultural Experiment Station, showed no significant difference in survival among substrate treatments. There were, however, significant differences among final mean shrimp weights, at two salinities, in bare fiberglass tanks and tanks with sand or clay substrates. The final mean weights at 27 g kg −1 were 15·1 g, 14·2 g and 13·3 g, respectively. At 45 g kg −1 the final mean weights were 13·2 g, 11·9 g and 11·6 g, respectively. Subsequently, two 6-week rearing trials at The Oceanic Institute, Hawaii, compared shrimp survival and growth, water turnover rate and effluent water quality in liner, mud and sand substrate treatments. There were no significant differences in survival but, in both trials, mean harvest weights were significantly lower with the mud substrate than with the sand or liner substrates. Substrate type affected effluent water quality. Where Secchi disk depth was controlled, trials # 2 and # 3, water turnover was affected by substrate type in the following pattern: mud > sand > liner. Significant differences were detected among substrate types in effluent concentrations of inorganic nutrients and total nutrients. The effluent stream sink accounted for 63% of total nitrogen and 65% of total phosphorus in the mud substrate treatment, and 70% of the total nitrogen and 97% of total phosphorus in the liner substrate treatment. Neither effluent pigment nor suspended material concentrations showed significant differences among treatments. These trials clearly demonstrated that pond liners are technically feasible in the culture of P. vannamei in the 1–16 g range and at densities from 15 to 50/m 2.

Benthic biology of the western Canadian continental shelf

Quantitative benthic studies on the British Columbian continental shelf are virtually non-existent. This paper attempts to review the inadequate data available. Sand and mud substrata on the western Canadian continental shelf of British Columbia off Barkley Sound support equally diverse benthic infaunal associations. Of the 282 taxa found in grab samples 142 were unique to this study, 42 were also present at other deep water sites, and 32 were ubiquitous. Organic carbon and nitrogen values were lower in sandy substrata than in mud. Reduced oxygen values in deep water resulting from a barotropic eddy present during the summer appear to be responsible for significant differences in the faunal associations between cruises in contrast to the community stability observed in other locations.

Prey behaviour and size‐selective predation by fish

SUMMARY 1. We investigate the role of differential activity of chiro‐nomids as an explanation for the size selection of small larvae by fish.2. In the laboratory, pumpkinseed sunfish (Lepomis gibbosus L.) selectively consumed large larvae of Chironomus tentans Fab. when no tube‐building materials were available. Small larvae were selectively consumed when a mud substrate was provided but there was no difference in predation rates on large and small larvae in sand.3. Small larvae spent more time out of their tubes than large larvae in the presence of fish, which may explain the selection for small larvae in mud. Large larvae apparently compensated for decreased foraging activity in the presence of fish by increasing activity when fish were absent. Visibility of large larvae inside tubes may account for their increased mortality in sand.4. Our results suggest that differential activity is important in explaining the size‐selective mortality observed in the field.

The ecology of the Corixidae (Hemiptera: Heteroptera) in the Corrib catchment, Ireland

Two surveys were carried out in the Corrib catchment (Ireland) to determine the physical and chemical factors that govern the distribution of Corixidae. Of the twenty one species recorded, five species, Sigara scotti (Fieber), S. distincta (Fieber), S. fossarum (Leach), S. fallenoidea (Hungerford) and Cymatia bonsdorffii (Sahlberg) comprised 82% of the numerical total. Although individual species occurred in chemically diverse sites species assemblages and changes in the relative abundance of the majority of species and in species richness and diversity were evident in the progression from hard to soft water. High altitude soft water sites had a much lower number of species compared with chemically similar low altitude sites. In Lough Corrib, the main body of water in the catchment, most species were abundant only in sheltered areas with mud substrates and high percentage vegetation cover. Species diversity was high in these areas and either C. bonsdorffii, S. fossarum, S. fallenoidea or Callicorixa praeusta (Fieber) dominated numerically. However, S. scotti, S. dorsalis (Leach) and Arctocorisa germari (Fieber) were more abundant in exposed areas with sand, gravel or mearl substrates. In temporary ponds and in lotic water species diversity was also high but species composition (mainly C. praeusta, Sigara nigrolineata (Fieber), Corixa punctata (Illiger), C. panzeri (Fieber), C. bonsdorffii) was different to that of temporally stable lentic habitats.

The effects of different oxygen regimes on the feeding and vertical distribution of Nephelopsis obscura (Hirudinoidea)

The feeding rates and vertical distribution of the freshwater leech Nephelopsis obscura, fed on different densities of third instar Chironomus riparius, were determined in the laboratory at three different constant dissolved oxygen regimes (10%, 100%, 300% saturation) at 15 °C. The rate of feeding increased linearly with prey density up to maximal field prey densities, with no satiation response. Analysis of covariance showed that the rate (slope) at which prey were consumed was not significantly different among oxygen regimes but the amount eaten at any given prey density was higher in higher dissolved oxygen saturations. Analysis of the vertical distribution of N. obscura at different oxygen saturations and prey densities showed a higher proportion of N. obscura on or in the mud substrate compared to the water column at 100% and 300%. No correlation was found between prey density and the vertical distribution of N. obscura, but the numbers of prey eaten were correlated with the proportion of N. obscura on the mud substrate. These results indicate that higher percentage dissolved oxygen regimes increase the feeding of N. obscura and are of potential importance in explaining the seasonal depth distribution and microdistribution patterns recorded for N. obscura.

Marine debris flows: Late precambrian “tillites” of the Avalonian-Cadomian orogenic belt

Correlative Late Precambrian strata of the Avalonian-Cadomian orogenic cycle, deposited after 670 and before 550 Ma are now widely dispersed around the margins of the North Atlantic. These contain several prominent diamictite horizons, long interpreted as “tillites”, within thick turbidite successions associated with volcanic horizons. The Granville Formation of the Armorican Massif in Normandy, France contains many pebby mud (diamicite) beds up to 20 m thick that have been interpreted as glaciogenic. Regionally, the Granville Formation occurs within the lowest part of the Upper Brioverian Supergroup which consists of several kilometres of turbidites and volcanogenic rocks. At Granville, diamictites can be traced along striked into deformed and intermixed graded conglomerates and mudstones. Diamictites are identified as debris flows generated on a submarine slope by the emplacement of gravel turbidites on a mud substrate and their mixing during downslope slumping. A glacial influence cannot be identified. In North America, the Conception Group of the Avalon Peninsula, Newfoundland, Canada, contains nearly 4 km of turbidites with a conformable sequence of diamictites (the Gaskiers Formation) near its base Massive and crudely-stratified diamicite beds (< 25 m thick) have a tabular geometry and are interbedded with thin-bedded, fine-grained turbidites. Glacially-striated and faceted clasts identify a previous phase of glacial transport but clasts and matrix are dominantly of volcanic origin; air-fall bombs are present. Diamictites were deposited as marine debris flows; associated “disrupted” diamicite sequences are identified as slump deposits. The diamictites record downslope remobilization of large volumes of unstable volcanic and glacial debris; restricted glaciation of volcanic cones along a complex island-arc is suggested. The diamictite successions of the Granville and Gaskiers formations provide significant data regarding facies types, associations and the geometry of resedimented diamictite sequences in deep marine basins along active plate margins. Similar deposits at the same tectonic-stratigraphic horizon occur in New England and Africa. This paper emphasizes the difficulty of identifying a direct glacial influence on diamictite sedimentation in such settings and the need for a sedimentological reappraisal of other supposed late Precambrian “tillites” preserved in orogenic belts. This is a necessary first step prior to modelling late Precambrian paleoclimates.

Habitat Characteristics, Population Size, and Home Range of the Bog Turtle, Clemmys muhlenbergii, in Maryland

Twenty bog turtle, Clemmys muhlenbergii, colonies were studied in Carroll, Baltimore, and Harford counties, Maryland, to determine habitat characteristics, population size, and movements and home range. Thirty-six habitat variables at each colony site were used in statistical analyses to examine the relationship between indexes of population size and habitat characteristics. Based on principal com- ponents analysis, the greater the index of population size, the more likely the colony was located in a circular basin with (1) spring-fed pockets of shallow water, (2) a bottom substrate of soft mud and rock, (3) dominant vegetation of low grasses and sedges, and (4) interspersed wet and dry pockets. Of the nine sites where populations could be estimated, we found from 7 to 213 turtles/ha of wetland habitat. Bog turtles were active for six months in Maryland. Home ranges were larger in males (0.176 ha) than in females (0.066 ha) and overlapped considerably among individuals of both sexes. Home ranges rarely extended far beyond the transitional edge of the wetland. Although turtles had small activity areas, they moved ex- tensively within those areas. Winter retreats were shallow, just below the upper surface of frozen mud and/or ice. Four of eight turtles monitored moved in and out of winter retreats from November through March. Conservation efforts should focus on protection of a wetland network that allows movement and gene flow among populations to minimize the effects of local extinctions.