Patterns in sponge (Porifera) assemblages on temperate coastal reefs off Sydney, Australia

1996 ◽  
Vol 47 (7) ◽  
pp. 897 ◽  
Author(s):  
DE Roberts ◽  
AR Davis
Keyword(s):  
Positive Relationship ◽  
Multivariate Analyses ◽  
Spatial And Temporal Variation ◽  
Small Scale ◽  
Remotely Operated Vehicle ◽  
Percentage Cover ◽  
Macrobenthic Assemblages ◽  
Voucher Specimens ◽  
Encrusting Sponges ◽  
Sydney Australia

Pattern and process in deep-water macrobenthic assemblages have largely been inferred from the study of such assemblages on shaded artificial structures in relatively shallow water. This paper examines patterns in the diversity and abundance of sponges to a depth of 50 m on coastal reefs off Sydney, Australia. Photo-quadrats were used to provide estimates of the species richness and percentage cover of sponges on three reefs. Sponge morphotype (i.e. encrusting or massive) was also recorded. Within-reef variation was examined by nesting three sites within each reef at each of three depths; replicate photo-quadrats (0.45 m², n = 5) were taken at each site. In addition, a remotely operated vehicle was used to collect voucher specimens. Over 50 species of sponge were identified, many of which have never been described. In general, sponge richness increased with depth, as did the number of erect or massive forms. In contrast, cover decreased with depth, particularly for encrusting sponges. Univariate and multivariate analyses revealed considerable small-scale spatial and temporal variation in sponge distribution and abundance. A significant positive relationship between richness and cover was also apparent. In general, there were greater temporal changes in the patterns of abundance for the shallow reef assemblages at 20 m, relative to those at 30 m and 50 m.

The influence of an offshore artificial reef on the abundance of fish in the surrounding pelagic environment

2015 ◽  
Vol 66 (5) ◽  
pp. 429 ◽  
Author(s):  
Molly E. Scott ◽  
James A. Smith ◽  
Michael B. Lowry ◽  
Matthew D. Taylor ◽  
Iain M. Suthers
Keyword(s):  
Artificial Reef ◽  
Management Tool ◽  
Small Scale ◽  
Pelagic Environment ◽  
Significant Difference ◽  
Small Scale Effect ◽  
Total Fish ◽  
Seriola Lalandi ◽  
Natural Reefs ◽  
Sydney Australia

Artificial reefs are a popular fisheries management tool, but the effect of these reefs on the abundance of fish in the surrounding pelagic environment is uncertain. Pelagic baited remote underwater video (PBRUV) was used to observe the fish assemblage surrounding an offshore artificial reef (OAR), near Sydney, Australia. PBRUVs were deployed at three distances (30, 100, 500m) from the OAR, and compared with a drop camera deployed directly over the OAR. There was a significantly greater abundance of fish on the OAR, but no significant difference in abundance at the 30-, 100- or 500-m distances. Two highly mobile non-resident species (Seriola lalandi, Pseudocaranx dentex) were significantly more abundant on the OAR, but this association was not detected 30m away. The lack of a significant difference in total fish abundance, or in assemblage composition, between the 30-, 100- and 500-m distances suggests that any association with the OAR is on a localised scale (<30m). One exception was the ocean leatherjacket (Nelusetta ayraudi), which had an association detected 100m from the OAR. This predominantly small-scale effect may be influenced by the proximity of this OAR to numerous natural reefs.

Long-Range Dependence of Traffic Flow and Speed of a Motorway: Dynamics and Correlation with Historical Incidents

2017 ◽  
Vol 2616 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Sai Chand ◽  
Gregory Aouad ◽  
Vinayak V. Dixit
Keyword(s):  
Time Series ◽  
Long Range ◽  
Traffic Congestion ◽  
Hurst Exponent ◽  
Fractal Theory ◽  
Urban Traffic ◽  
Spatial And Temporal Variation ◽  
Long Range Dependence ◽  
Incident Rates ◽  
Sydney Australia

Speed and flow of vehicles tend to have several effects on the dynamics of a transport system. Fluctuations of these variables can implicate congestion, can lower predictability, and may even catalyze crashes. A concept of fractal theory called the Hurst exponent—a measure of the long-range dependence (LRD) of a time series—was used to understand the fluctuations in flow and speed of a motorway in Sydney, Australia. The spatial and temporal variation of the LRD for flow ( Hflow) and speed ( Hspeed) at several monitor sites is discussed. Furthermore, the effects of number of lanes on flow and speed predictability are explored. It was observed that the flow predictability of two-lane sections was significantly lower when compared with three-lane and four-lane sections. Conversely, the speed predictability of four-lane sections was considerably higher than that of two-lane and three-lane sections. Finally, traffic congestion was defined with regard to the LRD of speed, and its correlation with historical incident rates was measured. It was ascertained that monitor sites with a historically high proportion of large Hspeed were correlated with unsafe locations. This study could lead to many applications of fractal analysis on highways and urban traffic.

Spatial and temporal variation in the abundance and taxonomic composition of estuarine and terrestrial macrofauna associated with mangrove logs

2013 ◽  
Vol 94 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Jennifer T.M. Andrade ◽  
Natália Barros Palhano ◽  
Claudia Helena Tagliaro ◽  
Colin Robert Beasley
Keyword(s):  
Dominant Species ◽  
Multivariate Analyses ◽  
Taxonomic Composition ◽  
Economic Importance ◽  
Spatial And Temporal Variation ◽  
Mangrove Forests ◽  
Tidal Channel ◽  
Total Abundance ◽  
Significant Difference ◽  
Northern Brazil

Brazilian mangroves have ecological and economic importance, with molluscs, crustaceans and polychaetes being diverse and common faunal groups. The present study characterizes the macrofauna associated with logs from two mangrove forests in Pará State, northern Brazil, sampled in September, January and April, between 2008 and 2010, at three different distances from a tidal channel (2, 10, 20 m). In each forest, five logs (diameter/length: 10/40 cm) were randomly selected at each distance, totalling 15 logs per sampling date. The macrofauna was removed, counted and identified. Three-way analysis of variance was used to compare mean numbers of individuals, numbers of taxa and Berger–Parker dominance per log, between forests and among sampling dates and distances from the tidal channel. Non-metric multidimensional scaling and permutational multivariate analyses of variance were used to investigate macrofaunal structure in relation to the three factors. A total of 5437 individuals from both estuarine and terrestrial faunas was found in both forests, with 85 taxa distributed among Mollusca, Annelida, Arthropoda and Nemertea. Abundance increased from September through January to April in both mangrove forests. The most dominant species was Neoteredo reynei, representing 48% of total abundance. No significant difference in any variable was found among the two forests and between the three distances. Logs may represent a stable microhabitat for the macrofauna, with little variation in humidity, salinity or temperature, despite different distances from the tidal channel. However, macrofaunal structure varied significantly between forests and among sampling dates, probably due to seasonal differences in precipitation and salinity between both locations.

Variability of macrobenthic assemblages under abnormal climatic conditions in a small scale tropical estuary

2006 ◽  
Vol 68 (1-2) ◽  
pp. 17-26 ◽  
Author(s):  
Carlos H. Lucero R. ◽  
Jaime R. Cantera K. ◽  
Isabel C. Romero
Keyword(s):  
Climatic Conditions ◽  
Small Scale ◽  
Tropical Estuary ◽  
Macrobenthic Assemblages

Small-scale spatial structuring of interstitial invertebrates on three embayed beaches, Sydney, Australia

2014 ◽  
Vol 150 ◽  
pp. 92-101 ◽  
Author(s):  
Belinda C. Cooke ◽  
Ian D. Goodwin ◽  
Melanie J. Bishop
Keyword(s):  
Small Scale ◽  
Spatial Structuring ◽  
Sydney Australia

scholarly journals Boat anchors not OK: Loss of Dugong grass (Halophila ovalis) population structure in Havelock island of Andaman and Nicobar Islands, India

2019 ◽  
Author(s):  
A.K. Mishra ◽  
N.S. Sumantha ◽  
A. Deepak
Keyword(s):  
Population Structure ◽  
Shoot Density ◽  
Canopy Height ◽  
Small Scale ◽  
List Type ◽  
Andaman And Nicobar Islands ◽  
Percentage Cover ◽  
Halophila Ovalis ◽  
Seagrass Ecosystem ◽  
Nicobar Islands

AbstractAnthropogenic disturbance due to deployment of boat anchors and loss of seagrass ecosystem is not well understood in India. So, we used Govind Nagar beach of Havelock Island of Andaman and Nicobar Islands (ANI)to assess the impacts of boat anchors from traditional fishing and recreational activities on the seagrass Halophila ovalis population structure. H. ovalis density, biomass, morphometrics, canopy height and percentage cover were estimated from two stations of Govind Nagar beach i.e., one highly impacted from boat anchors (Station1) and a sheltered station (Station 2). A clear evidence in reduction of shoot density of H. ovalis was observed at station 1, exception was similar apex densities between both stations. H. ovalis morphometrics, such as number of leaves per shoot, leaf length, width and horizontal rhizome length were observed with significant lower values at station 1 compared to the sheltered station 2. Reduction in seagrass morphometrics also resulted in the loss of seagrass canopy height and percentage cover. A clear evidence of loss of seagrass population structure under the influence of physical disturbances caused by boat anchors were observed. We report for the first time the impacts of boat anchors on seagrass ecosystems of India and our results pitch for wider studies across India. The impact of boat anchors is small-scale, but in long-term loss of seagrass ecosystem services will have dire consequences on fish habitat and carbon storage. Therefore, proper management and conservation measures should be taken to prevent the loss of important dugong grass habitats of ANI.HighlightsPhysical disturbances caused by boat anchors decreased the shoot density of H. ovalis by 1.2-fold.1 to 2-fold reduction in canopy height and the morphological features of individual plants were observed due to damage caused by boat anchorsHabitat disturbance reduced 1.6-fold percentage cover of H. ovalis at Havelock Island of Andaman and Nicobar Islands, India

scholarly journals The First Cut Is the Deepest: Trawl Effects on a Deep-Sea Sponge Ground Are Pronounced Four Years on

2020 ◽  
Vol 7 ◽  
Author(s):  
Katelin M. Morrison ◽  
Heidi Kristina Meyer ◽  
Emyr Martyn Roberts ◽  
Hans Tore Rapp ◽  
Ana Colaço ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Deep Sea ◽  
Multivariate Analyses ◽  
Benthic Communities ◽  
Bottom Trawl ◽  
Physical Disturbance ◽  
Remotely Operated Vehicle ◽  
The Status ◽  
And Control ◽  
Distinct Separation

Few studies have described the effects of physical disturbance and post-recovery of deep-sea benthic communities. Here, we explore the status of deep-sea sponge ground communities four years after being impacted by an experimental bottom trawl. The diversity and abundance of epibenthic megafauna of two distinct benthic communities in disturbed versus control areas were surveyed using a remotely operated vehicle on the Schulz Bank, Arctic Ocean. Four years after disturbance, megafaunal densities of the shallow (∼600 m depth) and deep (∼1,400 m depth) sites were significantly lower on the disturbed patches compared to the control areas. Multivariate analyses revealed a distinct separation between disturbed and control communities for both sites, with trawling causing 29–58% of the variation. Many epibenthic morphotypes were significantly impacted by the trawl, including ascidians, Geodia parva, Hexactinellida spp., Craniella infrequens, Lissodendoryx complicata, Haliclonia sp. Stylocordyla borealis, Gersemia rubiformis and Actiniaria sp. However, we found some smaller morphospecies to be equally abundant with control transects, including Polymastia thielei, Geodia hentscheli, and Stelletta rhaphidiophora, reflecting lower trawl impact for these morphotypes. Overall, our results suggest that these are fragile ecosystems that require much more time than four years to recover from physical disturbance typical of trawling activities.

Small-Scale Effects of Offshore Wind-Turbine Foundations on Macrobenthic Assemblages in Pinghai Bay, China

2019 ◽  
Vol 36 (1) ◽  
pp. 139
Author(s):  
Zhiqiang Lu ◽  
Xiaofang Zhan ◽  
Yuqing Guo ◽  
Li Ma
Keyword(s):  
Wind Turbine ◽  
Scale Effects ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Small Scale ◽  
Macrobenthic Assemblages

scholarly journals Spatial and Temporal Variation of Wideband Indoor Channels

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
David L. Ndzi ◽  
Nick Savage ◽  
Boris Gremont
Keyword(s):  
Impulse Response ◽  
Transfer Functions ◽  
Temporal Variations ◽  
Spatial And Temporal Variation ◽  
Small Scale ◽  
Time Of Arrival ◽  
Prony Algorithm ◽  
Detailed Assessment ◽  
Value Decomposition ◽  
The Impact

Extensive studies of the impact of temporal variations induced by people on the characteristics of indoor wideband channels are reported. Singular Value Decomposition Prony algorithm has been used to compute the impulse response from measured channel transfer functions. The high multipath resolution of the algorithm has allowed a detailed assessment of the shapes of individual multipath clusters and their variation in time and space in indoor channels. Large- and small-scale analyses show that there is a significant dependency of the channel response on room size. The presence of people in the channel has been found to induce both signal enhancements and fading with short-term dynamic variations of up to 30 dB, depending on the number of people and their positions within the room. A joint amplitude and time of arrival model has been used to successfully model measured impulse response clusters.

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