scholarly journals Nematodes as bio-indicators of physical disturbance of marine sediments following polychaete bait harvesting

2021 ◽  
Vol 19 (2) ◽  
pp. 117-130
Author(s):  
Matthews Wafula ◽  
Agnes W. Muthumbi ◽  
Virginia Wangondu ◽  
Charles Kihia ◽  
Julius Okondo
Keyword(s):  
Benthic Communities ◽  
Feeding Guilds ◽  
Physical Disturbance ◽  
Sediment Samples ◽  
Community Assemblage ◽  
Deposit Feeders ◽  
Low Diversity ◽  
Nematode Diversity ◽  
Genus Richness ◽  
Disturbed Site

Sediment disturbance in marine environments is caused by activities including polychaete bait harvesting, trawling, dredging, sediment erosion and treading. These activities affect the benthic communities by changing the densities, community assemblage and diversity. The aim of this study was to evaluate the potential of nematodes as indicators of sediments disturbance following polychaete bait harvesting. The study was conducted in three sites experiencing different bait harvesting intensities in Mida Creek, Kenya. Sediment samples were collected from the mudflats during low tide, preserved in 5% formalin and transported to the laboratory for processing and identification of nematodes. The highly disturbed site recorded the lowest nematode genus richness while the less disturbed sites had the highest. Overall, the most abundant nematode genera in the non-disturbed (Dabaso) and less disturbed sites (Kirepwe) were selective deposit feeders (Spirinia and Terschellingia), while most disturbed sites (e.g. Mayonda) had predators/omnivores (Pheronus, Aporcelaimellus) and selected members of the genus Spirinia. The disturbed site was characterised by low nematode diversity (H’) and low dominance (D) while the non-disturbed and less disturbed sites had higher diversity and dominance. Clearly, nematode community assemblage, diversity and feeding guilds changed following disturbance to a low diversity that favoured higher proportions of predator/omnivore taxa.

Spatio-temporal variability of zoobenthic communities in a tectonic lagoon (Lake Vouliagmeni, Attika, Greece)

2008 ◽  
Vol 88 (5) ◽  
pp. 873-881 ◽  
Author(s):  
Chariton Chintiroglou ◽  
Chryssanthi Antoniadou ◽  
Panagiotis Damianidis
Keyword(s):  
Multivariate Analyses ◽  
Benthic Communities ◽  
Marine Species ◽  
Trophic Group ◽  
Spatial And Temporal Scales ◽  
Mediterranean Lagoons ◽  
Deposit Feeders ◽  
Spatio Temporal ◽  
Lagoon Lake ◽  
Hard Substrata

Lake Vouliagmeni (Attica, Greece) is a lagoon of great scientific interest due to its endemic fauna, widely used for recreational activities. Understanding the dynamics of this peculiar ecosystem is essential for its conservation. An ecological survey of the benthic communities was carried out, in both spatial and temporal scales. Material was collected with SCUBA diving, by taking off samples from the principal habitats of the lagoon, i.e. meadows, soft and hard substrata. The identification of the collected 61,975 living specimens revealed the presence of 12 floral and 20 faunal species. Multivariate analyses separated the sampling sites according to the four different habitats of the lagoon, whereas no temporal patterns came up. Micrograzers were the dominant trophic group, followed by deposit feeders regardless of the habitat studied. Lake Vouliagmeni is among the less diverse Mediterranean lagoons, mostly due to its isolation from the sea that hinders the entrance of marine species.

Changes in benthic communities of Port Phillip Bay, Australia, between 1969 and 1995

1998 ◽  
Vol 49 (8) ◽  
pp. 847 ◽  
Author(s):  
Robin S. Wilson ◽  
Simon Heislers ◽  
Gary C. B. Poore
Keyword(s):  
Benthic Communities ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Suspension Feeding ◽  
Deposit Feeders ◽  
Low Levels ◽  
Muddy Sediments ◽  
Sandy Sediments ◽  
Major Division

Changes in benthic communities in Port Phillip Bay, Australia, were assessed over a 25- year period by comparing an intense bay-wide survey carried out in the early 1970s, a 3-year study in the mid 1970s, a limited survey in the early 1990s, and a resurvey in the mid 1990s. A major division of benthic communities into those on deeper muddy sediments and those on marginal sandy sediments persisted was less well defined (by ordination methods) in the 1990s than in the 1970s. The densities of individuals and species declined significantly, but absolute numbers of taxa did not change noticeably. Nevertheless, temporal variability in all variables over 25 years was within the range reported for the 3- year study. Polychaetes have become relatively more abundant than crustaceans and molluscs, and the proportion of suspension-feeding organisms has increased at the expense of deposit feeders. The introduced Japanese bivalve Theora lubrica was the most abundant invertebrate in the 1970s. In the 1990s, this species, the European bivalve Corbula gibba and the polychaete Euchone limnicola were the most abundant. Decreasing abundances of macrobenthic invertebrates, and a decreasing proportion of deposit feeders, is consistent with a decrease in nutrient load from moderate to low levels—such as occurred with reduced discharge from Melbourne’s sewage treatment plant—but lack of contemporaneous data prevents further explanation.

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.

Effects of a fish weir on the structure of the macrobenthic community of a tropical sandy beach on the Amazon coast

2020 ◽  
Vol 100 (2) ◽  
pp. 211-219
Author(s):  
Thuareag Monteiro Trindade dos Santos ◽  
Daiane Aviz
Keyword(s):  
Sandy Beach ◽  
The Other ◽  
Artisanal Fisheries ◽  
Trophic Groups ◽  
Gradual Decline ◽  
Sediment Samples ◽  
Deposit Feeders ◽  
Waves And Currents ◽  
Sandy Sediments ◽  
Fish Weir

AbstractThe present study investigated the effects of a fish weir, a fixed trap used by artisanal fisheries, on the intertidal macrobenthic infauna of a macrotidal sandy beach on the Amazon coast. Biological and sediment samples were collected from within the weir and at five points of increasing distance (10 cm, 50 cm, 1 m, 2 m, 5 m and 50 m) from the external portion of the trap. The sediments from the weir and at 10 cm were dominated by mud, with a gradual decline in fine grains, water content and organic matter with increasing distance from the weir to 50 m (control). Taxon abundance and richness were significantly higher in the weir and at 10 cm than at the other sampling points. There was a trend of decreasing density and richness of the infauna from the weir to 1 m (which was a point of transition between the muddy and sandy sediments), after which the biological descriptors tended to increase once again. A shift was also observed in the dominant trophic groups, with a decrease in the abundance of the deposit feeders with increasing distance from the weir. By contrast, predators were more abundant at the points further from the weir. Our results indicate that fish weirs alter the associated sedimentary habitats, due to the increased protection from the action of waves and currents, with a micro-scale (from a few centimetres to 1–2 m) influence on the local macrofauna.

Comparative distribution of macrocrustaceans in a north-western Australian mangrove system

1984 ◽  
Vol 35 (5) ◽  
pp. 591 ◽  
Author(s):  
FE Wells
Keyword(s):  
Species Diversity ◽  
Trophic Levels ◽  
Deposit Feeders ◽  
Mangrove System ◽  
Low Diversity ◽  
Mollusc Species ◽  
Density And Biomass ◽  
Deposit Feeding ◽  
Western Australian ◽  
North Western

Species diversity, density and biomass of macromolluscs and macrocrustaceans were investigated in the Bay of Rest (22� 18'S.,114�08'E.), a small mangrove system in north-western Australia. Mollusc species diversity, density and biomass were generally greatest on the seaward mudflat and lower in Avicennia and Rhizophora tree zones; no molluscs were recorded on the landward backflat. Crustaceans were diverse and abundant on the mudflat but the biomass was low. Diversity, density and biomass were high in Avicennia, lower in Rhizophora and the backflat. Filter-feeding molluscs were important on the mudflat, as were deposit feeders which dominated in Avicennia. Surface raspers were most important in Rhizophora. Deposit feeding and omnivorous crustaceans were dominant in all areas. It is suggested that molluscs and crustaceans in the system, both in the tree zones and on the seaward mudflat, are largely dependent on detrital breakdown of the mangroves for their nutrition. They may play a key role in converting primary production by the trees into animal tissue available to higher trophic levels.

Ecological singularity of temperate mesopredatory myliobatoid rays (Chondrichthyes: Myliobatiformes)

2017 ◽  
Vol 68 (6) ◽  
pp. 1098 ◽  
Author(s):  
Natalia L. Ruocco ◽  
Luis O. Lucifora
Keyword(s):  
Benthic Communities ◽  
Trophic Niche ◽  
Trophic Resources ◽  
Ecological Redundancy ◽  
Low Diversity ◽  
Trophic Overlap ◽  
Oligotrophic Ecosystems ◽  
First Time ◽  
High Diversity ◽  
Trophic Models

Many myliobatoid rays are important mesopredators, having significant effects on coastal benthic communities. In tropical and subtropical high-diversity oligotrophic ecosystems, they partition their trophic resources, which results in high ecological singularity. However, it is unknown whether this is true for temperate low-diversity eutrophic ecosystems. In the present study, we tested, for the first time, the hypothesis that myliobatoid mesopredators are ecologically redundant in a temperate low-diversity eutrophic ecosystem. We quantified diet and measured intra- and interspecific trophic overlap in the three species that regularly occur off Uruguay and northern Argentina, namely Myliobatis goodei, Myliobatis ridens and Dasyatis hypostigma. M. ridens had a typical durophagic diet composed of bivalves and gastropods, M. goodei fed primarily on polychaetes and decapods, diverging from the durophagic diet typical of its genus, and D. hypostigma preyed primarily on amphipods and decapods. There were ontogenetic and seasonal dietary differences in all three species. It is concluded that ecological singularity is present in this temperate myliobatoid assemblage, with each species having a different trophic niche. The practice of pooling together myliobatoid mesopredators in trophic models must be abandoned unless there is evidence of ecological redundancy.

scholarly journals Historical Shifts in Benthic Infaunal Diversity in the Northern Gulf of Mexico since the Appearance of Seasonally Severe Hypoxia

Diversity ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 49
Author(s):  
Nancy N. Rabalais ◽  
Melissa M. Baustian
Keyword(s):  
Species Richness ◽  
Dissolved Oxygen ◽  
Bottom Water ◽  
Benthic Communities ◽  
Penaeid Shrimp ◽  
Severe Hypoxia ◽  
Low Oxygen ◽  
Large Area ◽  
Surface Deposit ◽  
Deposit Feeders

Severe and persistent bottom-water hypoxia (≤2 mg O2 L−1) occurs on the Louisiana/Texas continental shelf from mid-May through mid-September over a large area (up to 23,000 km2 in mid-summer). Benthic infauna are less mobile than demersal organisms and become stressed by the low dissolved oxygen; benthic community composition, abundance, diversity, and biomass become altered. From the 1950s to the early 1970s, when sediment core indicators identified the initiation and subsequent worsening of dissolved oxygen conditions, there were no hydrographic data or benthic infaunal studies within the current area of frequent bottom-water hypoxia. This study highlights the impacts of severe hypoxia on benthic macroinfaunal communities and how they may have changed from less-hypoxic periods. Polychaetes were and are the dominant taxa in the available studies, but polychaete species richness in summer is now curtailed severely beginning with our 1985–1986 data. Species richness of polychaetes in summer hypoxia (1985–1986 and 1990–1991) was about 60% less than comparable taxa in 1972–1973. Abundance of polychaetes was much less in summer than spring, and recent infaunal biomass in summer was only 15% of what was found in spring. The result is less prey for demersal penaeid shrimp and fishes. Over the period of our comparison, infaunal feeding modes shifted from subsurface deposit feeders and surface deposit feeders to primarily surface deposit feeders (i.e., 95.5% of all polychaetes). Most were opportunistic, hypoxia tolerant, and recruited in high numbers following hypoxia abatement, some in fall and winter but most in spring. As benthic communities succumb to the stress of severe and continued seasonal low oxygen, they occupy the few upper centimeters of the sediment profile above the redox discontinuity layer with negative feedbacks to the water column by way of altered biogeochemical processes.

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