Variety Of Aquatic Habitats Research Articles

Aquatic Habitats of Canaan Valley, West Virginia: Diversity and Environmental Threats

We conducted surveys of aquatic habitats during the spring and summer of 1995 in Canaan Valley, WV, to describe the diversity of aquatic habitats in the valley and identify issues that may threaten the viability of aquatic species. We assessed physical habitat and water chemistry of 126 ponds and 82 stream sites, and related habitat characteristics to landscape variables such as geology and terrain. Based on our analyses, we found two issues likely to affect the viability of aquatic populations in the valley. The first issue was acid rain and the extent to which it potentially limits the distribution of aquatic and semi-aquatic species, particularly in headwater portions of the watershed. We estimate that nearly 46%, or 56 kilometers of stream, had pH levels that would not support survival and reproduction of Salvelinuw fontinalis (brook trout), one of the most acid-tolerant fishes in the eastern US. The second issue was the influence of Castor canadensis (beaver) activity. In the Canaan Valley State Park portion of the valley, beaver have transformed 4.7 kilometers of stream (approximately 17% of the total) to pond habitat through their dam building. This has resulted in an increase in pond habitat, a decrease in stream habitat, and a fragmented stream network (i.e., beaver ponds dispersed among stream reaches). In addition, beaver have eliminated an undetermined amount of forested riparian area through their foraging activities. Depending on the perspective, beaver-mediated changes can be viewed as positive or negative. Increases in pond habitat may increase habitat heterogeneity with consequent increases in biological diversity. In contrast, flooding associated with beaver activity may eliminate lowland wetlands and associated species, create barriers to fish dispersal, and possibly contribute to low dissolved oxygen levels in the Blackwater River. We recommend that future management strategies for the wildlife refuge be viewed in the context of these two issues, and that the responses of multiple assemblages be incorporated in the design of refuge management plans.

Bat Activity in a Forest Landscape of Central Massachusetts

Nine species of bat are known to occur across the six New England states, but most aspects of their natural history, such as foraging habitat use, are poorly understood. Recent published research has documented the importance of still-water habitats as foci of bat flight activity. To better understand and document habitat use in southern New England, we used the AnaBat II acoustical monitoring system to assess species composition and relative levels of summer flight activity. Active acoustic surveys were conducted in six habitat types on the Quabbin Reservation in central Massachusetts in 2003 and 2004. Bat flight activity, as measured by numbers of echolocation call sequences, was high, with an average of 24 search-phase and 4 feeding-buzz calls per 20-minute survey period. Myotis lucifugus (little brown bat) was the most commonly recorded species. Bat flight activity was high over all still-water habitats, but greatest over large ponds. Large-bodied bats, such as Eptesicus fuscus (big brown bat), were recorded more often in open, structurally uncluttered habitats. Of the small-bodied bats, little brown bats were ubiquitous, whereas Myotis septentrionalis (northern myotis) was most common in structurally cluttered habitats of seasonal forest (vernal) pools and along forest streams. Generalized habitat associations among the bat species we recorded are similar to those reported for other New England forest sites. The Quabbin Reservation is an excellent site to continue examining bat-habitat relationships because of the abundance and diversity of aquatic habitats, in both cluttered closed-canopy and uncluttered open-canopy settings.

Efectos antrópicos sobre las praderas sumergidas de carófitos en una laguna cárstica

Charophytes are submerged macrophyte algae often found in diverse aquatic habitats. Chara-dominated lakes are typically hard water, calcium-rich and low in phosphate. La Colgada is a 18 m deep, 103 ha small lake located in a tourist area, which has partly resulted in nutrient increases in recent years. Chara hispida var. major (Hartm.) R.D. Wood and Chara hispida f. polyacantha (A. Braun) R.D. Wood meadows are extensive in this ecosystem, but their distribution are influenced by human activities. Negligible densities of C. hispida, always covered by epiphytes, were recorded in the shores adjacent to tourist areas. Horizontal cover and biomass distributions were heterogeneous throughout the lake (0,95 ± 0,55 kg DW•m -2 ), with minimum values nearby the tourist area (0,68 ± 0,32 kg DW•m -2 ). Charophyte biomass was inversely related to depth in areas not influenced by anthropogenic impacts. However, that relationship did not occur in anthropized areas. The biomass range of Charophytes in La Colgada lake, 0,22-2,27 kg DW•m -2 , was much higher than that recorded in other world lakes and wetlands.

Nitrification in the Upper Mississippi River: patterns, controls, and contribution to the NO3−budget

We measured nitrification rates in sediment samples collected from a variety of aquatic habitats in Navigation Pool 8 of the Upper Mississippi River (UMR) 7 times between May 2000 and October 2001. We also conducted nutrient-enrichment experiments and analyzed vertical profiles of sediment to determine factors regulating nitrification. Nitrification rates were relatively high compared to other ecosystems (ranging from 0–8.25 μg N cm−2 h−1) and exhibited significant temporal and spatial patterns. Nitrification rates were greatest during the summer and spring compared to autumn and winter (ANOVA, p < 0.05) and were greater in contiguous backwater and impounded habitats compared to main and side-channel habitats (p < 0.05). Regression analysis indicated that nitrification rates were weakly (r2 = 0.18, p < 0.0001) related to temperature and exchangeable NH4+ of the sediment. However, nutrient-enrichment experiments showed that NH4+ availability did not limit nitrification in 3 sediment types with variable organic matter. Vertical profiles of sediment cores demonstrated that oxygen concentration and nitrification had similar patterns suggesting that nitrification may be limited by oxygen penetration into sediments. We conclude that temperature and sediment NH4+ can be useful for predicting broad-scale temporal and spatial nitrification patterns, respectively, but oxygen penetration into the sediments likely regulates nitrification rates in much of the UMR. Overall, we estimated that nitrification produces 6982 mt N/y of NO3− or 7% of the total annual NO3− budget.

Are River Styles ecologically meaningful? A test of the ecological significance of a geomorphic river characterization scheme

Abstract Classification is a useful tool for researchers and managers wishing to group functionally similar sites or to identify unique or threatened habitats. A process‐based river classification scheme that successfully integrates physical and biological aspects of lotic form and function would enhance conservation and restoration efforts by allowing more meaningful comparisons among sites, and improving functional understanding of lotic ecosystems. The River Styles framework provides a geomorphological river characterization scheme in which assemblages of geomorphic units vary for differing River Styles, presenting differing arrays of aquatic habitat diversity for each style. The ecological significance of the River Styles framework is tested by comparing the macroinvertebrate assemblages and habitat characteristics of pool and run geomorphic units for three different River Styles on the north coast of New South Wales, Australia. Multivariate ordinations and analysis of similarity (ANOSIM) revealed that macroinvertebrate community structure differed between Bedrock‐Controlled Discontinuous Floodplain rivers and Gorge rivers, and between Bedrock‐Controlled Discontinuous Floodplain and Meandering Gravel Bed rivers, especially in pools. Differences between Gorge and Meandering Gravel Bed rivers were less apparent, largely due to variations within the Meandering Gravel Bed rivers group. The variability in macroinvertebrate assemblage structure among geomorphic units was most strongly related to variability in substrate and hydraulic variables. Substrate composition differed significantly among all River Styles and geomorphic units, but other habitat variables showed few consistent differences among River Style groups. These results suggest that the ecological similarity of macroinvertebrate communities within River Styles may presently be limited because some important large‐scale drivers of local habitat conditions are not included in River Styles designations. Integrating River Styles classification with other large‐scale variables reflecting stream size, temperature and hydrological regime may produce a process‐based physical classification capable of identifying river reaches with similar ecological structure and function. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Plankton biodiversity in a landscape of shallow water bodies (Mediterranean coast, Spain)

A large spatial heterogeneity was detected in La Safor, a coastal area with different kinds of small and shallow water bodies. The area exhibits a sharp gradient in eutrophication (0.004–20 mgP l−1; 0.6–457 μg Chl a l−1) and varied water body features (morphology: size, depth; hydrology; vegetation, etc.). These factors result in a high diversity of aquatic habitats within the area. One hundred and twenty eight species of microalgae were identified in the 32 sampling stations studied (in the wet and dry periods). The phytoplankton richness varied between 1 and 21 species, the Shannon-Wiener index range was 0–3 bits, the index of floral originality (IFO) range was 0.1 – 0.6. A total number of 126 species of zooplankton were identified. The zooplankton specific richness ranged from 4 to 26 species, the diversity index and IFO were 0.9–3.7 and 0.1–0.6, respectively. A PCA allowed the ordination of different water body types as a function of total phosphorus, flux of water, water transparency, presence of macrophytes and oxygen. Plankton richness, diversity index, equitability and IFO showed weak relationships to the trophic gradient. The global planktonic biodiversity was higher than expected for such an anthropogenically affected ecosystem. The different, above mentioned conditions contributed to the limitation of biodiversity loss often observed in eutrophic conditions.

Status of freshwater fish habitat science in Great Britain

Abstract The general understanding of how habitats influence populations of freshwater fishes in Great Britain is reviewed briefly as a component of a Europe-wide comparison. Great Britain, an island of temperate climate in the north west of Europe comprising the countries England, Scotland and Wales, has diverse aquatic habitats but a relatively impoverished freshwater fish fauna. Recreational rod-and-line fisheries for certain salmonids and non-salmonids termed coarse fish are valuable components of the economies of the countries comprising Great Britain. In some cases, distribution and abundance of fish species and their population sizes are constrained by habitat degradation. There is a growing awareness of the multidimensional importance of habitat management to develop and maintain high quality fisheries. Current knowledge of fish habitat requirements is patchy; progress has been made on salmonids and some coarse fish species. Fish habitat science has an important role in integrated river catchment management, which is reflected in recent national and international legislation.

Patterns of Instream Wood Recruitment and Transport at the Watershed Scale

A wood budget was constructed for the Game Creek basin (132 km2) in southeast Alaska to identify spatial and temporal controls on the abundance and distribution of large woody debris (LWD). Field measurements of wood storage, size, and age were used to estimate volumetric rates of LWD recruitment and transport. Mortality recruitment did not follow a spatial pattern and ranged from 0.1 to 8.1 m3·km−1·year−1 (recruitment corresponded to forest mortality rates of 0.1–2.6% per year). Wood recruitment by bank erosion increased with increasing drainage area and ranged from 1 m3·km−1·year−1 at the smallest drainage areas to about 16 m3·km−1·year−1 at 60 km2. Bank erosion recruitment exceeded the maximum mortality recruitment at a drainage area of approximately 20 km2 (about 10-m-wide channel). Recruitment from land-sliding was only locally significant. The contribution of fluvial transport (flux) to total LWD storage increased with drainage area to an asymptotic maximum of 50% at about 50 km2 (about 20-m-wide channel). Mean predicted transport distances for mobile LWD over the lifetime of individual pieces ranged from about 200 m in small, jam-rich streams to about 2,500 m in larger channels with fewer jams. Fluvial transport of LWD increased interjam spacing and jam size and decreased jam age with increasing distance downstream. Constructing LWD budgets at the watershed scale has numerous geomorphic and ecological implications, including identifying spatial controls on the abundance and diversity of aquatic habitats. In addition, information on LWD budgets may be useful for determining how and where to protect LWD sources to streams.

Long-term trends in the breeding populations of waterbirds (1951–1985) at a sewage treatment plant

Long-term (1951–1985) data on the breeding waterbird populations and habitat modifications at Cape Flats sewage treatment works (Strandfontein) and Rondevlei Bird Sanctuary (Rondevlei) were assessed to establish the main factors affecting the breeding species richness and nest abundance. Fifty-two 'water-associated' breeding species were recorded in the Zeekoe River catchment waterbodies, 46 (88.5%) at Strandfontein, 38 (73.1%) at Rondevlei Bird Sanctuary (Rondevlei), 33 (63.5%) at Zeekoevlei and ten (19.2%) at Princess Vlei. Thirteen (25.5%) of the species were unique to Strandfontein and five (9.8%) to Rondevlei. Sorenson's similarity indices indicated high similarity (Cs = 0.81) in species richness and low similarity in nest abundance pattern (CN = 0.10) for the paired sites Strandfontein-Rondevlei. The lowest breeding species richness (11 species) was in winter (June) and the peak (42 species) was in spring (October). Twenty-four species joined the breeding population of Strandfontein during 1959–1976 (during which time pond water surface area increased 2372%). The mean breeding species richness increased significantly (χ 2 2 = 14.42, P <0.001) at Strandfontein during three distinctive periods: 1951–1958 (pre-construction), 1959–1976 (construction) and 1977–1985 (stabilization). At Rondevlei there were no significant differences in breeding species richness during the same periods. However, there were significant differences in the nest abundance pattern between these grouped years, both at Strandfontein (χ 2 2 = 1472.2, P <0.001) and at Rondevlei (χ 2 2 = 60.28, P <0.001). It is suggested that the same pool of species use the heterogeneous habitats at all the sites in the catchment according to their availability. The remarkable increase in species richness and nest abundance at Strandfontein after the late 1970s is attributed to higher habitat structural complexity, broad habitat types, stabilization and maturation of pond water and the subsequent increase in food diversity and availability. The decrease in Rondevlei nesting populations after the 1960s is probably related to fluctuations in water levels, cover of mudbanks with vegetation and high density of alien fish. A multipurpose management concept for conservation is proposed for the Zeekoe River catchment area. Strandfontein provides the greatest diversity of aquatic habitats not available elsewhere in the catchment (habitats for rare breeders such as Avocet, Black-winged Stilt, Red-billed Teal and some plovers) Rondevlei has a complementary habitat spectrum (suitable for Great Crested Grebe, Podiceps cristatus, Little Bittern, Ixobrychus minutus, and reedbed species). Zeekoevlei provides a large area of reedbed habitat for colonial breeding species (African Spoonbill and herons) and Princess Vlei is suggested for attracting Laridae.

Aquatic habitat diversity along the corridor of an Alpine flood plain river (Fiume Tagliamento, Italy)n

Habitat structure and diversity were investigated at multiple scales along the Tagliamento River (NE Italy) to analyze the spatial and temporal configuration of the aquatic habitat templet in a complex alluvial river corridor in the European Alps. A geomorphic approach was employed to determine floodplain structure and channel configuration using aerial photographs and digitized maps. Structural, thermal, and chemical variables were sampled monthly for one year in 3-km long study sections within six distinct geomorphic reaches along the longitudinal continuum. Aquatic habitat heterogeneity and complexity was quantified along the longitudinal dimension (corridor scale), within geomorphic reaches (floodplain scale) and within floodplain water bodies (within-habitat scale). Four major types of aquatic habitats were distinguished: surface-connected channels (SC), alluvial channels (AC), tributary channels (TC), and isolated standing water bodies (ISO). The first 3 types included primary, secondary, and tertiary branches plus backwaters. Active floodplain width was greatest in the island-braided lower floodplain (reach IV), which also exhibited the highest values for aquatic habitat area per river km, aquatic-terrestrial ecotone length per river km, within-floodplain thermal heterogeneity, and aquatic habitat diversity. Principal component analysis (PCA) clearly distinguished lotic from standing waters along the primary axis and substrate gradients (both longitudinally between floodplains and laterally within floodplains) on the secondary axis. PCA applied to 21 chemical variables illustrated a downstream increase in floodplain-scale spatio-temporal heterogeneity along the river corridor. Total environmental variance is considerably enhanced by the superimposition of longitudinal changes (corridor scale) on lateral changes within geomorphic reaches (floodplain scale). This study clearly demonstrated the high levels of structural complexity and habitat diversity that are possible in Alpine rivers, with implications for the important role of environmental heterogeneity in sustaining functional integrity.

Sympatry in theCulicoides variipennisComplex (Diptera: Ceratopogonidae): a Taxonomic Reassessment

We report sympatry among larval populations of the Culicoides variipennis complex in widespread and diverse aquatic habitats throughout the United States. Six sites in California, Nevada, New Mexico, and Texas were co-inhabited by C. v. occidentalis and C. v. sonorensis, whereas 8 sites in Florida, Georgia, Louisiana, Maryland, and Texas were co-occupied by C. v. sonorensis and C. v. variipennis. No intermediate forms were identified either electrophoretically or morphologically in adults reared from field-collected larvae and pupae. The absence of intergrades in zones of sympatry represents sufficient evidence to confirm species status for Culicoides variipennis (Coquillett) and Culicoides occidentalis Wirth & Jones, and to elevate Culicoides sonorensis to species rank (NEW STATUS). Culicoides v. albertensis Wirth & Jones is a synonym of C. sonorensis (NEW SYNONYMY); C. v. australis Wirth & Jones also is confirmed as a synonym of C. sonorensis. We also demonstrated a correlation between population taxonomic status as determined by electrophoresis and adult morphology.

The natural heritage of Loch Lomond: Its importance in a national and international context

The dual character of Loch Lomond, its size as the largest area of fresh water in Great Britain and its diverse communities of plants and animals, make it of major importance locally, nationally and internationally and it will undoubtedly be the ‘Jewel in the Crown’ of the proposed Loch Lomond and Trossachs National Park. The greatly contrasting bathymetry, with a long narrow deep northern trough and a broad shallow southern basin, is unique for any lake in Europe. This division, by the Highland Boundary Fault, is reflected also in the catchment and in the flora and fauna of the loch. Among the flora are found notable species such as the Scottish Dock (Fig. 1), Slender Rush, Elongated Sedge and two species of Waterworts. Rare invertebrates also occur in Loch Lomond: the worm Arcteonais lomondi was new to science when it was discovered there and named accordingly. Nineteen species of fish occur in Loch Lomond — the largest number in any Scottish loch. Fifteen are native and four introduced. Two are of particular importance ‐Powan (Fig. 2) and an unusual local race of River Lamprey. Other aquatic vertebrates of significance are the Greenland White‐fronted Goose and the Otter. Within the Loch Lomond catchment there is a great variety of aquatic habitats that make a substantial contribution to the diversity and importance of the natural heritage of the area. Notable among these waters is the River Endrick. The importance of the loch itself has been recognised by the creation of the Loch Lomond National Nature Reserve, which itself was designated in 1976 as a wetland of international importance under the Ramsar Convention. In spite of this, the loch's high amenity value — to tourists and for recreational purposes, as a fishery and a source of water supply — poses various threats and those with interests in tourism, camping, boat hire, cabin cruising, power boating, water skiing, canoeing, bathing, picnicking, natural history, angling, research, conservation and water supply are likely to be involved in conflicts of interests. Of particular concern are the number of alien plants and animals which have been introduced to the area; some of these are now well established. The problems concerned are likely to be resolved successfully only if some form of co‐ordinated programme involving the integration of conservation and multi‐purpose usage is developed for the loch and its catchment. Such a programme and its relevant monitoring must be one of the first tasks of the new National Park Authority.

ATMOSPHERIC CHANGE AND THE DIVERSITY OF AQUATIC INVERTEBRATES: ARE WE MISSING THE BOAT?

The response of natural systems to atmospheric change may depend critically on species diversity and on the genetic diversity (variability) found within their respective populations. Yet, most surveys of aquatic invertebrates account for neither. This may be of particular concern for benthic populations in running waters because of the considerable variability and the fragmentary nature of these habitats (e.g. isolated watersheds). In such habitats, species with limited genetic variability and/or limited dispersal capabilities (genetically differentiated populations) may be unable to track rapid environmental change, and may be more susceptible to climatic perturbations. We present a conceptual framework to illustrate some of the potential problems of ignoring population genetics when considering the impacts of global atmospheric change. We then review a simple method to assess population genetic structure and we evaluate available data on the genetic structure of North American stream invertebrates. These data indicate that benthic taxa often consist of genetically differentiated local populations, or even previously unknown species. Accordingly, our limited knowledge of population structure among benthic invertebrates may result in the unwitting loss of genetic and/or species diversity. Enhanced taxonomic research incorporating molecular techniques is clearly warranted. Conservation strategies based on the preservation and remediation of a diversity of aquatic habitats are likely to be our best means of ensuring species and genetic diversity of invertebrate taxa.

Effects of channel restabilization on habitat diversity, twentymile creek, mississippi

AbstractTwentymile Creek, a sand‐bed stream draining a 450 km2 catchment in northeast Mississippi, was channelized prior to 1910, in 1938, and in 1966. Straightening and enlargement in 1966 was followed by channel instability—rapid bed degradation (2‐4 m) and cross‐section enlargement by 1.4 to 2.7 times. Grade control structures (GCS) (weirs with stoneprotected stilling basins) and various types of streambank protection were constructed along the channel in the early 1980s to restore stability. Other investigators have suggested that habitat recovery in incised, channelized streams is facilitated by construction of GCS because they create stable scour holes and promote natural formation of a low‐flow channel flanked by vegetated berms. Effects of restabilization of Twentymile Creek on aquatic habitats were assessed in four ways. The fraction of the bank line covered by woody vegetation was mapped from aerial photographs taken in 1981 and 1985; physical habitat (depth, velocity, substrate, and cover) and fishes were sampled at base flow; and the existence and size of a low‐flow channel was ascertained from cross‐section surveys taken in 1980 and 1989. Woody vegetation, physical aquatic habitat, and fishes were also sampled from Mubby‐Chiwapa Creek, a similar‐sized unstable channel with no GCS. Physical habitat variables and fishes were sampled concurrently at five stations on Twentymile Creek, and four stations on Mubby‐Chiwapa. Four of the five Twentymile stations were either above or below a GCS. Bank‐line woody vegetation cover increased 8 per cent between 1981 and 1985 along Twentymile Creek but was stable along Mubby‐Chiwapa. Reaches above and below GCS were deeper with slower current velocities than elsewhere. Mean Shannon diversity indices based on physical data were similar for both streams, but were 58 per cent higher for stations immediately above and below GCS than for other stations. Since construction of the GCS and bank protection measures, longitudinal berms have formed within the enlarged Twentymile Creek channel, creating a low‐flow channel. Low‐flow channel capacity was equivalent to a mean daily discharge equalled or exceeded 30 per cent of the time, and was considerably lower than the effective discharge. Differences in aquatic habitat diversity among the stations sampled were primarily due to the scour holes below the GCS and the low‐flow channel. Thirty‐nine fish species were collected from Twentymile Creek, but only 22 from Mubby‐Chiwapa. Fourteen species were collected exclusively at GCS. Principal component analyses of the abundance of the eight numerically dominant fish species indicated similar faunas at most stations, but Twentymile Creek GCS stations were faunistically distinct. Abundance of several of the numerically dominant species was positively influenced by greater depths and lower velocities found near Twentymile GCS. The mean fish diversity index for Twentymile Creek was 29 per cent higher than for Mubby‐Chiwapa, and fish diversity was positively correlated with substrate diversity and mean depth.

Long term monitoring of amphibian populations with respect to the effects of acidic deposition

Amphibians breed in a variety of aquatic habitats in the United States. While the tolerance of low pH has been examined for many species of amphibians, those that breed in temporary ponds have been the most studied in terms of acidic precipitation. Some of the latter have been shown to have lethal limits for low pH that are close to or above the pH's found in many breeding ponds. Temporary ponds occur in large numbers in the areas of the country most affected by acidic precipitation. Many of these ponds are susceptible to acidification and reduced reproductive success of sensitive species of salamanders has been observed in acidic ponds. Additional practical and logistical considerations clearly make temporary ponds, and certain salamanders that breed in them, the best candidates for monitoring the long term effects of acidic precipitation on amphibian populations. We recommend a cost efficient monitoring scheme across three categories of acidic temporary ponds (low, medium, and high) that incorporates (a) chemical analyses of pond samples, (b) a census of the annual deposition of egg masses, as well as assessment of embryonic mortality in enclosed and unenclosed egg masses in the ponds, and (c) sampling of larval success. This plan offers the best opportunity for detecting changes in amphibian populations that are correlated with the acidity of precipitation, and would provide desperately needed long term data on the abundance of these amphibians.

Colonization by Mosquitofish (Gambusia affinis) of a Great Plains River Basin

Mosquitofish have rapidly colonized the Arkansas River basin in Kansas during the past 50 yr. Fish were collected from creeks in the basin to compare genetic and demographic characteristics of populations taken from relatively earlier and more recently established areas. Mean population levels of genetic variation were not significantly lower in more recently colonized areas, a result unexpected if initial founder events are important. In this case, multiple insemination of females and differential selection of colonizers may have decreased the eroding effects of founder events on genetic variation. Heterogeneity of genotypic and demographic frequency distributions was most common among populations in newly established areas, a finding attributed to non-random movement and/or survivorship of individuals involved in the colonization process. Male and female colonization patterns differed across the basin. Male heterozygosity values were significantly less than female and juvenile heterozygosities at all collection sites, indicating either differential mortality of heterozygous males or dispersion of them from creek populations. Males also exhibited a greater degree of genetic differentiation between sites within the basin, a finding which further supports the contention that males incur a greater selective force during colonization than females. The noted success of this species as a colonizer in many diverse aquatic habitats can be attributed to increased colonization capabilities of females in comparison to males and to the fact that single females who are multiply inseminated are able to seed new habitats with a genetically diverse group of offspring.

Specific growth rates of natural microbial communities measured by adenine nucleotide pool turnover

A novel experimental approach has been development to estimate the mean specific growth rates of natural populations of microorganisms. The method is based on the direct measurement of the turnover rate of the total adenine nucleotide (AN)pool using either [ 3H]adenine or 32PO 4 radiotraces. In laboratory cultures of bacteria and unicellular algae, the AN pool turnover rate is highly correlated with specific growth rate. This empirically derived relationship is then used to extrapolate AN pool turnover rates measured in the field to population-specific growth rates. The method is technically simple, straightforward and potentially capable of measuring a wide range of growth rates. Microbial community growth rate estimates measured using this new method ranged from 0.04 to 2.45 per day for samples collected from a variety of aquatic habitats. Growth rate estimates derived from data on AN pooll turnover compared favorably with estimates derived from measurements of microbial biomass and production. The AN pool turnover methos has numerous potential applications in applied and environmental microbiology.

Metabolism of Reduced Methylated Sulfur Compounds in Anaerobic Sediments and by a Pure Culture of an Estuarine Methanogen

Addition of dimethylsulfide (DMS), dimethyldisulfide (DMDS), or methane thiol (MSH) to a diversity of anoxic aquatic sediments (e.g., fresh water, estuarine, alkaline/hypersaline) stimulated methane production. The yield of methane recovered from DMS was often 52 to 63%, although high concentrations of DMS (as well as MSH and DMDS) inhibited methanogenesis in some types of sediments. Production of methane from these reduced methylated sulfur compounds was blocked by 2-bromoethanesulfonic acid. Sulfate did not influence the metabolism of millimolar levels of DMS, DMDS, or MSH added to sediments. However, when DMS was added at approximately 2-muM levels as [C]DMS, metabolism by sediments resulted in a CH(4)/CO(2) ratio of only 0.06. Addition of molybdate increased the ratio to 1.8, while 2-bromoethanesulfonic acid decreased it to 0, but did not block CO(2) production. These results indicate the methanogens and sulfate reducers compete for DMS when it is present at low concentrations; however, at high concentrations, DMS is a "noncompetitive" substrate for methanogens. Metabolism of DMS by sediments resulted in the appearance of MSH as a transient intermediate. A pure culture of an obligately methylotrophic estuarine methanogen was isolated which was capable of growth on DMS. Metabolism of DMS by the culture also resulted in the transient appearance of MSH, but the organism could grow on neither MSH nor DMDS. The culture metabolized [C]-DMS to yield a CH(4)/CO(2) ratio of approximately 2.8. Reduced methylated sulfur compounds represent a new class of substrates for methanogens and may be potential precursors of methane in a variety of aquatic habitats.

Simple multi-filter sensors for determining relative radiation in the sea and in freshwater

The design, construction, testing and use of an underwater relative radiation sensor are described. The sensor incorporates four narrow band interference filters and a broad band (400–700 nm) filter so that variation in spectral quality as well as visible light attenuation can be determined. Comparison with a proprietary, calibrated sensor, a Macam SD 101, indicates the reliability of the relative radiation sensor of the range 1 to >300 Wm−2 P.A.R. and to a depth of at least 20 m. Brief reference is made to selected data from a variety of aquatic habitats. A general table for the comparison of radiation and illumination units is presented.

On Invertebrate Fauna of Benue and Plateau Waters, Nigeria 1. Preliminary Check-list of Zooplankton

This communication lists 45 zooplankton (26 rotifers, 12 cladocerans, and 7 copepods), identified from diverse aquatic habitats in the central part of Nigeria.