Faunal Density Research Articles

Benthic Invertebrates in Karst Springs: Does Substratum or Location Define Communities?

AbstractOnly a few studies to‐date have dealt with the habitat preferences of the fauna of springs. The main objective of our study was to fill this gap. The research was carried out in springs situated in the Kraków‐Częstochowa Upland, Poland. The benthic fauna was collected from fine and coarse substrata using a typical hydrobiological approach. Forty‐nine families or subfamilies and four higher taxa (Hydrozoa, Turbellaria, Nematoda, Hydracarina) were found in the springs studied. Invertebrates collected in springs were successfully classified into groups and, using the Analysis of Discriminant Function, were found to diverge in terms of substratum type. This prediction was 96% accurate for samples collected from fine sediments and 91% for samples collected from coarse sediments; the differences were higher in springs located in the southern part of the study area. Substratum type was found to be the main discriminatory factor with regard to the fauna density while faunal composition was related to the geographical position of springs. Our results emphasise that, even in very small habitats such as springs, all major substratum types should be considered for sampling. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Vertical distribution of macrobenthic infauna from the shallow sublittoral zone of Admiralty Bay, King George Island, Antarctica

A 0.0625 m2 mini-box corer (MBC) was used to study the vertical distribution of macrobenthos in the shallow sublittoral zone of Admiralty Bay, during the 2003/2004 summer, near the Brazilian Station Comandante Ferraz, and the Peruvian Station Machu Picchu. Sediment samples were taken from 20, 30 and 60 m, and stratified for particle-size, total organic matter (TOM) and faunal composition analysis. The most abundant taxa were Polychaeta, Oligochaeta, Amphipoda, Cumacea, Bivalvia and Gastropoda. In general, macrofauna were concentrated in the 0–4 cm layer (64% of total organisms). Correlations between sediment characteristics and faunal densities have not completely explained neither the aggregation of organisms at the surface sediment layers nor the differences in faunal composition between locations at 20 m depth. Analysis of parameters such as organic carbon, heavy metals, interstitial water, and species composition should contribute to a better understanding of the diversity patterns found in this study.

ENVIRONMENTAL CONTROLS ON FORAMINIFERA IN LAKE QARUN, EGYPT

Foraminifera were investigated in Lake Qarun, an Egyptian inland saltwater lake, to determine their spatial distribution and the most common environmental factors that influence this distribution. Forty surface sediment grab samples from the lake were found to be rich in benthic foraminifera. Their faunal density ranged from 63 to 13,400 tests g(-1) with an average of 1700 tests g(-1) (s = +/- 2480). Faunal diversity ranged from 4 to 15 species with an average 10 species per sample (s = +/- 2.3). Both faunal density and diversity decreased in areas (biotopes 1 and 3) dominated by clay and silt (grain size <63 mu m) rich in organic matter. Degradation of organic matter by aerobic and anaerobic bacteria could lead to very low dissolved oxygen in pore and bottom waters where foraminifera live. Faunal data were used to divide the lake into three ecological biotopes. Samples from biotopes; 1 and 3 are characterized by high clay-and-silt content, with Ammonia tepida and Quinqueloculina seminula characterizing biotope 1 and A. tepida, Q. seminula and Cribroelphidium excavatum dominating biotope 3. Samples from biotope 2 are characterized by bioclastic sand-dominated substrates that are rich in Q. seminula, A. tepida, Quinqueloculina poeyana, Bolivina striatula and Rosalina globularis.Ammonia tepida and Quinqueloculina seminula compose similar to 70% of the total foraminiferal assemblage in Lake Qarun. The distribution patterns of these species indicate that each is controlled by distinct environmental factors. In biotopes I and 3, A. tepida positively correlates with high clay-and-silt content and Q. seminula correlates with high total dissolved solids. Cribroelphidium excavatum correlates positively with magnetic susceptibility and negatively with total dissolved solids (TDS). In biotope 2, Quinqueloculina poeyana, Bolivina striatula and Rosalina globularis correlate positively with coarse bioclastic substrates enriched in phytal remains, a condition consistent with the presence of the epiphytic taxon R. globularis. The occurrence of these halophilic species in Lake Qarun seems to be a consequence of rising salinity that has made the lake a suitable habitat for these foraminiferal taxa.

The Impact of Benthic Macrofauna for Nutrient Fluxes from Baltic Sea Sediments

This article focuses on the ecological role of benthic macrofauna on nutrient dynamics and benthic-pelagic coupling in the Baltic Sea with relation to eutrophication. Generally, benthic macrofaunal activities have large effects on sediment biogeochemistry and often with stimulatory effects on processes that counteract eutrophication, i.e., denitrification and increased phosphorus retention of the sediment. The degree of faunal impact on such processes varies depending on faunal density and functional group composition. The effect of macrofaunal activities on sediment nutrient dynamics can also result in a higher nitrogen: phosporus ratio of the sediments efflux compared with sediments without macrofauna. Increased internal nutrient loading during eutrophication-induced anoxia is suggested to be caused both by altered sediment biogeochemical processes and through reduced or lost bioturbating macrofauna and thereby a reduced stimulatory effect from their activities on natural purification processes of the Baltic Sea ecosystem.

Detecting impacts and setting restoration targets in arid‐zone rivers: aquatic micro‐invertebrate responses to reduced floodplain inundation

Summary Water extraction from arid‐zone rivers increases the time between floods across their floodplain wetlands. Less frequent flooding in Australian arid‐zone rivers has impaired waterbird and fish breeding, killed riparian vegetation and diminished invertebrate and macrophyte communities. Restoration currently focuses on reinstating floods to rejuvenate floodplain wetlands, yet indicators to measure the success of this are poorly developed. We explored the application of criteria for ecologically successful river restoration to potential restoration of floodplain wetlands on the Darling River, arid‐zone Australia. Using emergence of micro‐invertebrates from resting eggs as an indicator, we compared responses of taxa richness, densities and community composition in floodplain lakes with different inundation histories. Increased drying of floodplain lakes reduced the number of micro‐invertebrate taxa. Several key taxa were absent and faunal densities (particularly cladocerans) were reduced when the duration of drying increased from 6 to 20 years. A conceptual model of the ecological mechanisms by which restoration of flooding regime could achieve the target of preserving micro‐invertebrate community resilience predicts that reducing the dry period between floods will minimize losses of viable resting eggs. Protection of this ‘egg bank’ permits a boom in micro‐invertebrates after flooding, promoting successful recruitment by native fish and waterbirds. Synthesis and applications. In arid‐zone rivers, micro‐invertebrate densities and community composition are useful indicators of the impact of reduced flooding as a result of water extraction. Critical to successful native fish recruitment as their first feed and as prey for waterbirds, micro‐invertebrates are a potential early indicator of responses by higher trophic levels. Taxon richness, density and key taxa present after flooding, all indicators of resilience, can be incorporated into targets for arid‐zone river restoration. For example, one restoration target may be microcrustacean densities between 100 and 1000 L−1 within 2–3 weeks after spring flooding. These criteria can be applied to measure the ecological success of restoration projects seeking to recover natural flood regimes. Given the high economic cost of water in arid zones, convincing demonstrations of the ecological success of environmental water allocations are crucial.

Infaunal responses to seagrass habitat structure: A study of life-history traits and population dynamics of Corophium volutator (Pallas)

Using a subtidal seagrass mosaic on the Åland Islands, northern Baltic Sea, as a model system, and the amphipod Corophium volutator as the main study organism, we investigated organism-, species- and community-level responses of macrofauna over two seasons in three habitats; the interior and the unvegetated edge of a seagrass (Zostera marina–Potamogeton pectinatus) meadow, and isolated seagrass patches (Ruppia spp.–Zannichellia spp.). Corophium volutator was the most abundant organism in the edge and patch habitats and the second most abundant in the interior habitat. Female biomass, reproduction and offspring fitness components of C. volutator did not seem constrained by habitat structure, and were synchronized across habitats. However, juvenile body length was significantly greater in the patches than in both meadow habitats. All habitats exhibited female-biased sex ratios, and the population was male dominated only on a single sampling occasion. The edge habitat did not support fewer macrofaunal individuals and species than the interior parts of the meadow. The patches supported the lowest animal densities, but were as equally diverse as the interior and edge habitats. When significant edge effects in terms of elevated faunal densities were found, they were usually species specific and consistent over time, e.g. the polychaete Nereis diversicolor showed consistently higher densities along the meadow edge. It is concluded that although devoid of above-ground structure, seagrass meadow edges are a critical part of the seagrass habitat, and thus of potential importance for higher trophic levels and energy transfer from the seagrass habitat.

Preliminary Response of Soil Fauna to Simulated N Deposition in Three Typical Subtropical Forests

ABSTRACT A field-scale experiment arranged in a complete randomized block design with three N addition treatments including a control (no addition of N), a low N (5 g m−2 year−1), and a medium N (10 g m−2 year−1) was performed in each of the three typical forests, a pine (Pinus massoniana Lamb.) forest (PF), a pine-broadleaf mixed forest (MF) and a mature monsoon evergreen broadleaf forest (MEBF), of the Dinghushan Biosphere Reserve in subtropical China to study the response of soil fauna community to additions of N. Higher NH+4 and NO−3 concentrations and a lower soil pH occurred in the medium N treatment of MEBF, whereas the NO−3 concentration was the lowest in PF after the additions of N. The response of the density, group abundance and diversity index of soil fauna to addition of N varied with the forest type, and all these variables decreased with increasing N under MEBF but the trend was opposite under PF. The N treatments had no significant effects on these variables under MF. Compared with the control plots, the medium N treatment had significant negative effect on soil fauna under MEBF. The group abundance of soil fauna increased significantly with additions of higher N rates under PF. These results suggested that the response of soil fauna to N deposition varied with the forest type and N deposition rate, and soil N status is one of the important factors affecting the response of soil fauna to N deposition.

Effects of water exchange and abiotic factors on zooplankton and epibenthic fauna in shrimp ponds

Assemblages of zooplankton and epibenthic invertebrates were collected from a commercial Penaeus monodon (Fabricius) pond at fortnightly intervals over an entire grow-out season. The pond inlet and outlet water were also sampled intensively over three 1-week periods throughout the season. Before stocking the ponds with shrimp postlarvae, copepods dominated the zooplankton. Immediately after the ponds were stocked, there was a rapid decline in zooplankton numbers, particularly the dominant larger copepods, suggesting heavy predation by shrimp postlarvae. For the rest of the season, barnacle nauplii were the dominant zooplankton component in the pond. Pond water exchanges had little detectable influence on the composition or density of the zooplankton assemblage. Instead, the dominance of barnacle nauplii appeared to have been maintained by steady recruitment due to barnacle reproduction in the pond. While changes in the biomass of pond zooplankton were not correlated with physico-chemical characteristics, changes in density were positively correlated with temperature, and negatively correlated with pH, dissolved oxygen and secchi disc readings. Epibenthic faunal density peaked at the end of the season, while the biomass peaked during the middle part of the season. Sergestids (Acetes sibogae Hansen) were the most abundant epibenthic taxa. No correlations were found between physico-chemical parameters and epibenthic fauna biomass or density. Abundances of epibenthic fauna were not related to zooplankton densities, suggesting that trophic interactions between these assemblages is not important. No Acetes were captured in samples of outlet water, and only on a single occasion were large numbers captured in the inlet water; after this, there was a notable increase in the number of Acetes in the pond. This evidence, together with the lack of an increase in the size of Acetes during the season, suggests that water exchange is an important but unpredictable source of recruitment of epibenthic fauna into the pond. The results emphasize the benefits of ensuring that appropriate zooplankton assemblages have been introduced into the ponds, when they are filled, to support the shrimp immediately after stocking. This will depend on the initial inoculum and may be difficult to manipulate with water exchanges once established. Assemblages of epibenthic fauna appear more likely to change with exchanges and may need to be monitored across the season, particularly if their presence reduces production through adverse impacts such as competition with postlarvae, introduction of disease or deteriorated water quality.

Distribution of Benthic Fauna in Relation to Environmental Conditions in an Inundated Opencast Sulphur Mine (Piaseczno Reservoir, Southern Poland)

Highly specific environmental factors such as the presence of strongly mineralized water, oxygenation of the water down to 10 m, a low trophic status of the water and low organic matter content in the bottom sediments, were found in the studied post-exploitation Lake Piaseczno. Of the 42 macroinvertebrate taxa found, Oligochaeta (Tubificidae) and Chironomidae predominated. Almost exclusively ubiquitous species were found, except for some chironomid taxa recorded for the first time in Poland. The most diversified faunal communities occurred at 1 m water depth whereas the highest densities were found at 5 m. At the deepest points studied only oligochaetes and Chaoborus flavicans were found. There was no correlation between organic matter content and macrofauna densities. Differences in inhabitation at the studied transects could result from various environmental factors such as the degree of macrophyte cover and protection from the wind. Undisturbed transects overgrown by macrophytes had a similar community composition and higher faunal densities than those which were less protected.

Community structure of macrobenthos in two tropical sandy beaches with different morphodynamic features, Rio de Janeiro, Brazil

AbstractThe macrobenthos of two exposed tropical sandy beaches in Rio de Janeiro (Brazil) were compared in relation to density, species richness, and vertical zonation. Biological and sediment samplings were carried out in the austral winter of 2002 and the austral summer of 2003. The sampling design consisted of 10 transects perpendicular to the water line, evenly divided into strata. A sampling unit was taken in each stratum with a 0.04 m2 quadrat sampler. Beaches were also compared according to physical features, such as slope, wave period, wave height, and grain size. According to Dean's Ω morphodynamic index the Pontal is a dissipative beach while the Costa Azul is a reflective one. The mean grain size ranged from median to coarse sand in Costa Azul, whereas in Pontal it ranged from median to very fine sand. Eleven species were collected in the two beaches. Crustaceans were the dominant in the Costa Azul Beach, while the polychaete Scolelepis squamata dominated the Pontal beach. A negative correlation was found between the density of the macrobenthos and mean grain size, and beach slope. On the other hand, the Dean's parameter correlated positively with faunal density. Based on the results of ANOSIM, in both beaches, two groups of stations were identified, defining an upper and a lower beach zone along the vertical distribution of the macrobenthos.

Interactions between the grass shrimp Palaemonetes pugio and the salt marsh grasses Phragmites australis and Spartina alterniflora

The grass shrimp Palaemonetes pugio, a species common to Spartina alterniflora-dominated marshes, may be sensitive to the invasion of the common reed Phragmites australis in northeastern US salt marshes. We examined two questions: (1) Do grass shrimp have a preference for the native plant over the non-native plant? (2) Are grass shrimp more effective foragers on P. australis? We tested the first hypothesis by comparing the amount of time shrimp spend in physical contact with the plant types over a 1-h period. Shrimp were observed under different arrangements of vegetation to control for differences in conspicuous structural features. Additionally, the amount of time shrimp spent foraging on S. alterniflora and P. australis shoots was compared to determine if shrimp graze more often on S. alterniflora. Shrimp spent significantly more time in contact with S. alterniflora only when plant types were grouped at opposite ends of aquaria, but did not exhibit a foraging preference for this plant type. To address our second question, we investigated the effects of shrimp foraging on stem epifauna, an assemblage of semi-aquatic invertebrates associated with macrophyte shoots. Previous research showed that P. australis supports a lower density of stem-dwelling epifauna relative to S. alterniflora. We hypothesized that the primary grazer of this community, P. pugio, can forage on P. australis stems more effectively due to structural differences between the two plants, causing the lower abundance of epifauna through top-down effects. We exposed individual shoots inhabited by epifauna to shrimp and compared faunal densities on exposed shoots to densities on control shoots after 18 h. The reduction of epifauna by predation was proportional on the two plant types. Therefore, top-down effects can be ruled out as an explanation for the patchy distribution of epifauna observed in P. australis–S. alterniflora marshes.

Comparison of benthic foraminifera inside and outside a sulphur-oxidizing bacterial mat from the present oxygen-minimum zone off Pakistan (NE Arabian Sea)

Assemblages of live (Rose-Bengal-stained) and dead benthic foraminifera and stable oxygen and carbon isotopic composition of live benthic foraminifera were studied in and outside a bacterial mat composed of the large sulphur-oxidizing bacteria Thioploca and Beggiatoa from the oxygen-minimum zone off Pakistan (NE Arabian Sea). Two cores from the same Multicorer retrieved a bacterial mat and ambient sediment. The dominant species ( Globobulimina affinis, G. turgida, Bolivina pacifica, B. pseudopunctata, Uvigerina peregrina and Buliminella tenuata) in both cores are characteristic for dysoxic oxygen minimum zone conditions. The most significant difference between the two cores is the reduced number of stained benthic foraminifera (SBF) in the top 0.5 cm of the bacterial mat. Faunal densities of stained species are more than four times higher in the sediment surface sample (0–0.5 cm) outside the bacterial mat, at a distance of only 1.5 m. All stained species, however, observed outside the Beggiatoa/Thioploca mat were also observed in the core with the mat. Two species, Virgulinella fragilis and Bolivina dilatata, occur exclusively in the core with the bacterial mat. The diversity within the bacterial mat core is thus slightly higher than outside. Furthermore, the abundances of the species Buliminella morgani, B. tenuata and Alliatina primitiva are substantially higher in the bacterial mat than outside. Globobuliminids, on the other hand, seem to prefer the conditions outside the bacterial mat and are five times more frequent in the core taken outside the bacterial mat. Benthic foraminifers inhabit a broader microhabitat range outside the bacterial mat (∼5 cm) than within (3.5 cm). A marked decrease in SBF abundances was observed at the level of a black sulphur-rich layer which is interpreted to mark the shallow redox front below the bacterial mat. Stable carbon isotope analyses on live benthic foraminifera do not support a relation of the investigated Beggiatoa/Thioploca mat to a constant or seasonal seepage of methane at the continental slope off Pakistan. Surprisingly, however, stable oxygen isotope values of many species and especially of U. peregrina decrease with depth, which calls into question the suitability of U. peregrina as a recorder of bottom-water δ 18O.

The soft-bottom macrobenthos of Gray's Reef National Marine Sanctuary and nearby shelf waters off the coast of Georgia, USA

As part of an ongoing ecological assessment of the Gray's Reef National Marine Sanctuary (GRNMS), a 58-km 2 marine protected area 32 km off the coast of Georgia, USA, surveys of benthic macroinfaunal communities, contaminant levels in sediments and biota, and general habitat conditions were conducted during 2000–2002 at 20 stations within the sanctuary and along three cross-shelf transects in nearby shelf waters. Macroinfaunal community structure and composition exhibited distinct cross-shelf patterns associated with sediment granulometry, depth and possibly other factors related to shoreline proximity (e.g., erosional effects, recruitment of estuarine species). Finer-scale spatial patterns of benthic fauna among stations within the sanctuary appear to be related to proximity to live-bottom habitat and other features of seafloor structure (e.g., rippled vs. flat sand). Population densities of dominant fauna within the sanctuary also varied considerably among years, resulting in shifts in the ranking of dominants at most stations. Chemical contaminants generally were at low background concentrations below probable bioeffect levels and thus are not a likely cause of the observed spatial patterns of benthic fauna. However, trace concentrations of pesticides, PCBs, and PAHs were detectable in sediments and biota throughout the study area, demonstrating that chemicals originating from human activities are capable of reaching the offshore sanctuary environment, possibly from atmospheric deposition or cross-shelf transport of materials outwelled through coastal sounds. Highly diverse infaunal assemblages also were observed within the sanctuary and nearby sites of similar depth, suggesting that the sanctuary is an important reservoir of marine biodiversity. Results of this study should be useful in addressing long-term science and management needs of the GRNMS and in furthering our understanding of broader ecological patterns and dynamics of the surrounding South Atlantic Bight (SAB) ecosystem.

Community structure of canopy arthropods associated toQuercus crassifolia×Quercus crassipescomplex

Quercus crassifoliaandQ. crassipesare dominant species in temperate forests of central Mexico and hybridize between each other when they occur in sympatry. Oak canopies contain a considerable portion of arthropod diversity and the hybrid zones can provide new habitats to epiphyte fauna. We tested if the establishment of hybrids in contact zones with their parental hosts increases the species diversity of canopy arthropods assuming that hybrid trees constitute new genotypes of potential new habitats to small organisms. We examined the effect of hybridization on some community structure parameters (diversity, composition, similarity and density of arthropod fauna) of canopy arthropods compared to their parental species in a hybrid zone located in central Mexico. We employed 17 leaf morphological traits and six diagnostic RAPD primers to identify parental and hybrid plants. The RAPDs marker showed unidirectional introgression towardsQ.crassifolia, and were detected hybrid (F1), backcrosses and introgression individual trees. In total, 30 oak canopies were fogged during rainy and dry season. We recognized 532 taxa of arthropods belonging to 22 orders associated with tree canopies. The taxonomic status of host‐trees may be an important factor in the arthropod community structure and that seasonality (dry and rainy) is not a factor that could modify their organization. Trees ofQ. crassipesregistered the highest densities of arthropod fauna followed by hybrid hosts (F1); trees originated by backcrosses towardsQ. crassifoliaregistered a significant less arthropod density than F1hybrids; and trees ofQ. crassifoliahad the lowest density. Hybrid plants andQ. crassipesindividuals had higher diversity (H′) of arthropods thanQ. crassifoliaplants. Hybrid plants had also more rare species in both seasons in comparison with parental species. This study suggests that hybrid oaks act as a center of biodiversity by accumulating arthropods of both parental and different species including a considerable number of rare species.

SOIL FAUNA AND LEAF LITTER DECOMPOSITION IN TROPICAL RAIN FOREST IN XISHUANGBANNA, SW CHINA: EFFECTS OF MESH SIZE OF LITTERBAGS

Background and Aims The influence of soil fauna on litter decomposition is rarely explored in tropical rain forest. This study examined the effect of soil fauna on the decomposition of mixed substrate by litter bag technical at two tropical seasonal rain forest plots in Xishuangbanna,SW China in year of 2000. The following questions were considered in the present study: 1) What roles do soil fauna play in regulating litter mass loss and decomposition rate? 2) How do soil fauna influence litter nutrient release? Methods In order to examine the role of soil macro-mesofauna in mass loss and nutrient release of litter,litter bags with both fine mesh size (0.15 mm) that excludes the soil macro-mesofauna population from litter and coarse mesh size (2 mm) that allows soil fauna access to litter were used in this experiment. Mass loss and C,N,P,S,K,Ca,and Mg concentrations of leaf litter were determined from the litter in two different mesh size litterbags at monthly intervals. The soil fauna were extracted by hand and by heating the samples. Key Results Higher relative density and taxonomic diversity of total soil fauna were found in the bags with 2 mm mesh size (22.3-21.77 individuals and 2.67-2.83 orders per g of dry litter) compared to the bags with 0.15 mm mesh size (2.88-2.77 individuals and 0.27-0.28 orders per g of dry litter). Collembola and Acari were the most abundant group,and Hymenoptera(ant),Coleoptera,Hemiptera,Diptera,Diplopoda,Isopoda,Araneae,Pseudoscorpiones were common groups of soil fauna in litter bags with 2 mm mesh size. There were very few individuals of Collembola and Acari in the 0.15 mm litter bags. Our results suggested that soil macro-mesofauna contributed more to the decomposition of leaf litter in 2 mm litter bags than that in 0.15 mm litter bags. The higher mass loss rate (around 71%),decomposition rate (k=1.88-2.44),and nutrient release in litter bags with 2 mm mesh size than in litter bags with 0.15 mm mesh size (34%-35%,k= 0.48- 0.58) indicated a significant influence of soil macro-mesofauna on mass loss and nutrient release in tropical seasonal rain forest. The release rates of N,S and Ca that could be attributable to the soil macro-mesofauna were higher than other elements whereas K release rate that could be attributable to the soil macro-mesofauna was the lowest. Soil macro-mesofauna caused greater decreases in C/N and C/P ratios in litter bags with 2 mm mesh size than litter bags with 0.15 mm mesh size. There were negative relationships of the percentage of litter mass remaining with order richness and individuals abundance of soil fauna. However,a positive relationship between Shannon-Wiener index of soil fauna and the decomposition rate was found. Conclusions This study suggests that the presence of soil fauna accelerated plant litter decomposition in the tropical seasonal rain forest. The litter mass loss attributable to the soil macro-mesofauna was about 46%. The effects of soil macro-mesofauna on the nutrient release rates were different among elements. The diversity of soil fauna may have important ecosystem consequences,particularly in tropical rain forest.

Benthic response to chronic natural physical disturbance by glacial sedimentation in an Arctic fjord

The activity of Arctic tidal glaciers results in high turbidity, high rate of inorganic particulate sedimentation and sedimentary instability in near-glacier marine basins. The chronic physical disturbance of sediments is accompanied by low input levels of organic matter. The response of soft-bottom macrofauna to glacial disturbance was studied in Kongsfjord, Svalbard. The quantita- tive characteristics of the macrofauna of 4 associations located along a gradient of glacier-induced disturbance were examined. Benthic biomass decreased with increased proximity to the glacier (from 10.9 g wet weight (ww) m -2 in the outermost association to 2.7 g ww m -2 in the glacial bay). Faunal density was highest in the transitional zone (592 ind. 0.1 m -2 ) between the central basin (425 ind. 0.1 m -2 ) and the inner glacial bay (442 ind. 0.1 m -2 ). The average individual biomass was lowest in the glacial bay as a result of the smaller body size of organisms. A decrease in the size of organisms in disturbed sites was not accompanied by a classical shift from 'equilibrium' to 'opportunistic' species. The functional structure of the faunal associations was simplified in the impoverished glacial bay association where 1 guild, the mobile surface-detritus feeders, strongly dominated. Average species number per sample was lowest in the glacial bay (22 species) and highest in the transitional associa- tion (42 species). Species diversity expressed by the Shannon-Wiener and Hurlbert rarefaction indices and evenness expressed by the Pielou index was lower in the glacial bay than in the remain- ing associations. The decrease in biomass, mean size of organisms, species diversity and evenness as well as the peaked distribution (i.e. maximum in the transitional zone) of density and species richness are consistent with patterns reported in studies of different natural and anthropogenic disturbances. Some distinct features of the case of glacial-induced disturbance include relatively high taxonomic distinctness and low beta diversity and low faunal dispersion in the near-glacier association.

Impact of Land Use Practices on Faunal Abundance, Nutrient Dynamics and Biochemical Properties of Desert Pedoecosystem

Increased dependence of resource-poor rural communities on soils of low inherent fertility are the major problem of desert agroecosystem. Agrisilviculture practices may help to conserve the soil biota for maintaining essential soil properties and processes in harsh climate. Therefore, the impacts of different land use systems on faunal density, nutrient dynamics and biochemical properties of soil were studied in agrisilviculture system of Indian desert. The selected fields had trees (Zizyphus mauritiana, Prosopis cineraria, Acacia nilotica) and crops (Cuminum cyminum, Brassica nigra, Triticum aestivum) in different combinations. Populations of Acari, Myriapoda, Coleoptera, Collembola, other soil arthropods and total soil fauna showed significant changes with respect to different land use practices and tree species, indicating a strong relation between above and below ground biodiversity. The Coleoptera exhibited greatest association with all agrisilviculture fields. The Z. mauritiana system indicated highest facilitative effects (RTE value) on all groups of soil fauna. Soil temperature, moisture, organic carbon, nitrate- and ammonical-nitrogen, available phosphorus, soil respiration and dehydrogenase activity were greater under tree than that of tree plus cropping system. It showed accumulation of nitrate-nitrogen in tree field and more utilization by crops in cultivated lands. Positive and significant correlation among organic carbon, nitrate- and ammonical-nitrogen, phosphorus, soil respiration and dehydrogenase activity clearly reflects increase in soil nutrients with the increase in microbial and other biotic activity. P. cineraria field was the best pedoecosystem, while C. cyminum was the best winter crop for cultivation in desert agroforestry system for soil biological health and soil sustainability. The increase in organic carbon, soil nutrients and microbial activity is associated with the increase in soil faunal population which reflect role of soil fauna in fertility building. This suggests that strategies may be developed for nurturing fertility-building soil fauna and managing degraded pedoecosystem in desert just by adopting suitable agricultural practices.

Feeding and territorial behavior of Paralvinella sulfincola, a polychaete worm at deep-sea hydrothermal vents of the Northeast Pacific Ocean

Behavioral adaptations to the severe nature and high faunal densities of hydrothermal vent habitats have received little attention from researchers. In this study, video and digital still imagery were analyzed to document the feeding and general behavior of the polychaete Paralvinella sulfincola at deep-sea vents on the Juan de Fuca ridge (North-East Pacific). This worm lives in mucous tubes on the actively growing portions of sulphide mineral chimneys and is considered to be the pioneering macrofaunal species in this habitat. We identified 6 recurrent behavior patterns, including antagonistic territoriality between neighboring conspecifics. The latter likely explains the regular spatial distribution of P. sulfincola populations on the substratum they colonize, and the observed confinement of feeding and exploration activities to a definable territory around the tube opening. Territory size, territorial overlap and density were significantly related to body weight, further supporting the importance of size and aggressive encounters in the maintenance of the worm's feeding area. During feeding, P. sulfincola uses its buccal tentacles to gather particles from the substratum using two different capture modes: seizing single macro-particles and aggregation of small particles.

Foraminiferal responses to polluted sediments in the Montevideo coastal zone, Uruguay

A study of foraminiferal assemblages was carried out in 24 sediment samples collected from the Montevideo coastal zone (south-eastern coastal region of South America) to assess the response of the benthic foraminifera to the polluted sediments. The area is affected by different pollutants such as sewage, hydrocarbons and heavy metals derived from different sources. Biological data were analyzed with multivariate techniques of cluster analysis and a principal component analysis (PCA) was performed for abiotic factors. The results allowed the recognition of different species assemblages corresponding to different sub-environments, which reflected the prevalent ecological conditions. The Montevideo Bay, particularly, its inner part showed an extremely poor foraminiferal fauna—including a totally azoic station—and high percentages of abnormal tests, when compared with the adjacent Punta Carretas and Punta Yeguas zones. Mean faunal density showed a strong relationship with organic matter, oxygen and heavy metal concentrations, as well as redox potential and pH values of each sub-environment. Although the adjacent zones presented a moderate pollution degree, it was noticed that a positive effect on the foraminiferal density specially on Ammonia tepida, caused by the sewage pipe located in Punta Carretas, a pure organic contamination. Differences among foraminiferal assemblages seemed to be related to the combined action of the several kinds of pollutants and the natural abiotic variables, like the rapid salinity changes that occurred in this area.

Benthic macro-invertebrate community composition within a mangrove/seagrass estuary in northern New Zealand

In the tropics and sub-tropics, estuarine environments with mangrove and seagrass habitats provide important structures and resources for diverse communities of benthic organisms. However, temperate estuarine habitats, especially in mangrove areas, may differ significantly in their community associations and interactions. The community composition of benthic macro-fauna was investigated within temperate Matapouri Estuary, northern New Zealand. The density and distribution of fauna were sampled within six distinctive habitats (mangrove stands, pneumatophore zones, Zostera beds, channels, banks, and sand flats), within four sampling events between December 2002 and September 2003. Each type of habitat was replicated seven times within different locations in the estuary. Counts of all infauna and epifauna within four replicate cores were recorded from each habitat and location. Multidimensional scaling plots were used to identify differences in structure and composition of assemblages among habitats and locations within each sampling event. Results from these benthic samples indicate that Matapouri Estuary has a high overall biodiversity, with distinctive faunal assemblages found within different habitats, and some seasonal variations also apparent. In terms of both number of individuals and taxa per unit area, seagrass beds had the highest numbers and mangrove areas had the lowest numbers, with all other habitats in between. Some locations were found to support a high diversity of organisms across habitats, while other locations had high densities of a few species only. Several physical and biological differences between tropical/sub-tropical and New Zealand's temperate mangrove habitats are put forth as potential reasons for the lower density and diversity of the benthic component observed herein. Further ongoing studies aim to elucidate the structure and interactions within food webs in this estuarine ecosystem.