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Benthic Fauna (benthic + fauna)
Selected AbstractsLand-use influences macroinvertebrate community response following a pulse disturbanceFRESHWATER BIOLOGY, Issue 8 2003Kevin J. Collier Summary 1.,We tested the hypothesis that interactions between disturbance types can influence invertebrate community response and recovery in two streams draining pasture (press-pulse disturbance) and native forest (pulse disturbance) catchments before and after a one-in-28-year flood. We also sampled drift and adult insects to gain insights into the relative importance of these two postdisturbance recolonisation pathways. 2.,Taxa numbers and total density declined markedly at the forested site after the flood, but there was a delayed response at the pasture site, reflecting greater initial resistance to this pulse disturbance among taxa adapted to the underlying press disturbance. 3.,Community composition was less stable at the pasture site where per cent abundance of taxa was highly variable prior to the flood and over the 2-year postflood sampling period. After the flood, the pasture stream fauna was more heavily dominated by vagile taxa, including several chironomid species and hydroptilid caddisflies. 4.,Taxa numbers and densities recovered to preflood levels within 5,7 months at both sites, but a range of taxa-specific responses was observed that took up to 18 months to recover to preflood densities. Community stability at the pasture site had not returned to preflood composition by 2 years postflood. 5.,Changes in drift densities of several common stream invertebrates at the pasture site reflected postflood changes in benthic densities and seasonally low drift in winter. Terrestrial invertebrates dominated drift at the pasture site for 3 months postflood whereas Ephemeroptera were most common at the native forest site. 6.,Flight patterns of selected adult aquatic insects showed a strongly seasonal pattern. Abundance of adults at the pasture site in the second year following the flood increased in line with the recovery of the non-Dipteran benthic fauna. Significant upstream flight occurred for several caddisfly species at the native forest site, and weakly directional or downstream flight was evident for most common Plecoptera and Ephemeroptera. 7.,This study indicates that the magnitude and duration of responses to major pulse disturbances can depend on the presence or absence of an underlying press disturbance. This finding has implications for monitoring, and suggests that a knowledge of disturbance history beyond 2 years may be required to interpret mechanisms contributing to observed land-use impacts. [source] Chronic fishing disturbance has changed shelf sea benthic community structureJOURNAL OF ANIMAL ECOLOGY, Issue 3 2000M. J. Kaiser Summary 1.,Bottom fishing using towed nets and dredges is one of the most widespread sources of physical disturbance to the continental shelf seas throughout the world. Previous studies suggest that degradation and ecosystem changes have occurred in intensively fished areas. Nevertheless, to date it has been difficult to attribute habitat and benthic community changes to fishing effort at a spatial scale that is truly representative of commercial fishing activities. 2.,In this study we present convincing evidence that chronic bottom-fishing disturbance has caused significant and widespread changes in the structure of two distinct soft-sediment benthic assemblages and habitats. 3.,Our study compared the benthic fauna found in areas that have been exposed to either high or low levels of bottom-fishing disturbance over the past 10 years. We were able to validate the fishing effort data in some areas using scars in the shells of a long-lived bivalve mollusc (Glycymeris glycymeris) which result from fishing disturbance. Shell scars occurred most frequently in bivalves collected from the area of highest fishing effort. 4.,Multivariate analyses and the response of abundance/biomass curves indicated that chronic fishing has caused a shift from communities dominated by relatively sessile, emergent, high biomass species to communities dominated by infaunal, smaller-bodied fauna. Removal of emergent fauna has thus degraded the topographic complexity of seabed habitats in areas of high fishing effort. The communities within these areas currently may be in an alternative stable state. [source] The biology of Roule's goby in the Kvarner area, northern Adriatic SeaJOURNAL OF FISH BIOLOGY, Issue 4 2001M. Kova Roule's goby Gobius roulei in the Kvarner area of the northern Adriatic Sea attained , 87.5 mm LT and an age of 7 years. In both sexes gonad development began in their second year. All males were mature by 3 years, and females by 4 years. Fecundity was related to LT and varied between 1200 and 8000 eggs. The breeding season lasted from April to August. Nests were built under empty shells of Pitaria chione or stones. Roule's goby was a predator and picker, feeding mostly on mobile benthic fauna, including bivalves, gastropods, polychaets, pagurids, mysids, gammarids and fishes. Larger specimens ate mainly macrofauna, while smaller specimens ate both meiofauna and macrofauna. [source] Environmental modulation of reproductive activity of the invasive mussel Limnoperna fortunei: implications for antifouling strategiesAUSTRAL ECOLOGY, Issue 7 2009DEMETRIO BOLTOVSKOY Abstract Limnoperna fortunei (Dunker, 1857) (Bivalvia) invaded Argentina through the Río de la Plata estuary around 1990 and is presently established throughout five South American countries as a dominant component of the benthic fauna and a major nuisance for industry and power plants. Between 1997 and 2006 we monitored the reproductive activity of L. fortunei through weekly measurements of planktonic larvae in six South American water bodies: Río de la Plata estuary, Paraná and Carapachay rivers, Salto Grande, Itaipú and Embalse de Río Tercero reservoirs. Mean larval densities varied between 4000 and 7000 individuals m,3; except in the reservoirs of Itaipú (450 ind. m,3) and Salto Grande (869 ind. m,3), where the mussel was first recorded shortly before our surveys, and upstream dispersal is limited (Salto Grande). In all cases, reproductive output decreases during the winter. At four of the six sites surveyed larval densities were comparatively high for 8.8,10.2 months per year. A lower food supply is possibly responsible for the shorter reproductive period of 5.9 months at Embalse. At Salto Grande, there is a well-defined mid-summer drop in larval numbers, coinciding with blooms of cyanobacteria. We propose that, in addition to temperature, two major factors may regulate the reproductive activity of L. fortunei: (i) the availability of food; and (ii) blooms of toxic cyanobacteria, significantly shortening the otherwise very long reproductive period. This information is important for the design of antifouling programmes involving the use of molluscicides, and has potential for reduced biocide use. These results provide supporting evidence for some fundamental ecological theories of invasions discussed here. [source] Temporal Distribution of Diagnostic Biofabrics in the Lower and Middle Ordovician in North China: Clues to the Geobiology of the Great Ordovician Biodiversification EventACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009Jianbo LIU Abstract: The temporal distribution of the diagnostic biofabrics in the Lower and Middle Ordovician in North China distinctly illustrates that the sedimentary systems on the paleoplate have been changed markedly as consequences of the Great Ordovician Biodiversification Event (GOBE). The pre-GOBE sedimentary systems deposited in Tremadoc display widespread microbialite and flat-pebble conglomerates, and a less extent of bioturbation. Through the transitional period of early Floian, the sedimentary systems in the rest of the Early and Mid- Ordovician change to GOBE type and are characterized by intensive bioturbation and vanishing flat-pebble conglomerates and subtidal microbial sediments. The irreversible changes in sedimentary systems in North China are linked to the GOBE, which conduced the increase in infaunal tiering, the expansion of infaunal ecospace, and the appearance of new burrowers related to the development of the Paleozoic Evolutionary Fauna during the Ordovician biodiversification. Thus, changes in sedimentary systems during the pivotal period of the GOBE were consequences of a steep diversification of benthic faunas rather than the GOBE's environmental background. [source] | |||||||||||||