Van Veen Grab Research Articles

CHARACTERISTICS AND DISTRIBUTION OF MICROPLASTICS IN SURFACE SEDIMENT OF SELAT PULAU TUBA, LANGKAWI, KEDAH

This study aims to assess the characteristics and occurrence of the microplastics contamination in surface sediment of Selat Pulau Tuba, Langkawi, Kedah. Van Veen Grab Sampler was used to collect the samples of sediment. The samples were immediately preserved and analyzed using a Fourier-transform infrared spectrophotometer and a microscope to determine the presence and characteristics of microplastics. The result indicates the presents of polypropylene and polyethylene with a size of 500 µm -1000 µm and 1000 µm - 1500 µm respectively. Overall, Selat Pulau Tuba, Langkawi, Kedah has minimal pollution of microplastics in sediment.

Microplastics Contamination in a High Population Density Area of the Chao Phraya River, Bangkok

Microplastics (MPs) are distributed globally, including in aquatic environments. While a large number of studies on MPs in marine environments have been performed, few studies are available in freshwater environments. Therefore, the distribution of MPs in surface water and sediment from the Chao Phraya River at Tha Prachan, a high population density area of Bangkok, was investigated. Water samples were collected by a manta trawl with a net mesh size of 300 mm. Sediment samples were collected by a Van Veen grab sampler. The total number and concentration of MPs in the water samples were found to be 104 particles/m 3 and 805.20 mg/m 3 , respectively. The dominant MPs were fragments, 0.5 to 1.0 mm in size, for the water samples. In the sediment, MPs were detected only in a size range of 0.053 to 0.5 mm with a total number and concentration of 2,290 particles/kg and 650 mg/kg, respectively. The presence of different types of MPs was confirmed by Fourier-transform infrared spectroscopy with a dominant abundance of polypropylene, polyethylene, and polystyrene. In brief, this study suggests that high levels of MPs occur not only in the water but also in the sediment of the Chao Phraya River at Tha Prachan area.

Microplastic contamination on the lower Chao Phraya: Abundance, characteristic and interaction with heavy metals

While a large number of studies on microplastics (MPs) in the western hemisphere have been performed, few studies are available in the eastern hemisphere, especially in Southeast Asia. In this study, the abundance of MPs in water and sediment samples from the Chao Phraya River at the Tha Pra Chan area, Thailand, was investigated. Water samples were collected by a manta trawl, and sediment samples were collected by a Van Veen grab sampler. The average number and concentration of MPs in water samples were 80 ± 65 items/m³ and 53.3 ± 58.4 mg/m³, respectively. The average number and concentration of MPs in sediment samples were 91 ± 13 items/kg and 4.9 ± 3.4 mg/kg, respectively. The main morphologies of MPs were fragments and fibers, mostly white. Polypropylene (PP) was the dominant polymer type found in both water and sediment. Moreover, the content of heavy metals (Cr, Cu, Ni, and Pb) on MPs was extracted by aqua regia solution and analyzed by ICP-OES. Results show high concentrations of Pb and Cu adsorbed on MPs in the study area. In brief, this study suggests that there are high levels of MPs in the water and sediments of the Chao Phraya River at the Tha Pra Chan area.

Ecological risk assessment of surface sediments of Çardak Lagoon along a human disturbance gradient.

Lagoons are the hotspot ecosystems whose sustainability should be secured using the ecological assessment indicators. This study aimed to quantify the surface sediment metal distributions of Çardak Lagoon in the Marmara region of Turkey, to characterize their natural and anthropogenic sources and transport mechanisms and to assess their potential ecological risks. The surface sediment samples were collected from 11 stations using Van Veen grab, while for the background values to be determined, core sampling was used from two stations. The analyses of multiple elements, total organic carbon, carbonate, and chlorophyll degradation by-products were carried out to characterize sediments. Enrichment factor and the indices of potential ecological and toxic risks were applied to assess the ecological status of the surface sediments. The operation of the gold mine in the close vicinity was found to be responsible for the enrichment of Au and Hg in the lagoon sediments. Cd, Tl, Sb, and Sr were the other elements responsible for the enrichment. The potential risk levels of the lagoon varied between the low and significant levels. The riskiest elements were found to be Hg and Cd which in turn pointed to the mining and agricultural activities as the most dominant human disturbance. The toxic risk index of Çardak Lagoon was estimated to range from 5.21 to 11.00, with a low mean value of 7.98. The C:N ratio range of 8.52 to 134.93 (a mean of 29.07) indicated that the organic C source was mostly of the terrestrial origin, in particular, from the surrounding agricultural lands.

An illustrated checklist of macrofaunal molluscs from soft-sediments of the Abrolhos Parcel (northeastern, Brazil) with 15 new records

Comprehensive understanding of marine biodiversity is essential for conservation, especially for vulnerable ecosystems. In this paper, we implemented and illustrated a checklist of molluscs from the Abrolhos Parcel, Brazil, the most important coralline area in South Atlantic waters. The list features 100 species belonging to 4 classes and 85 genera, of which 15 are new records for Bahia State, northeast Brazil. The results highlight the potential for new records in the area. The species came from 54 unconsolidated sediment samples collected from the bottom of the reef with a 0.042-m2 van Veen grab. Among the listed species, Curveulima sp., Notarchus sp. and Guyanella clenchi are new records for the South Atlantic, while Caecum metamorphosicum, Eratoidea janeiroensis, Volvarina serrei, Solemya notialis, Solariorbis shimeri, and Amphithalamus glabrus are endemic to Brazilian waters. A comparison of our results with those obtained in other reef environments indicates that the Abrolhos Parcel has a rich malacofauna and suggests that many more species can still be found with more samplings.

Spatial and temporal distribution of macrobenthic fauna of subtropical Richards Bay Harbour, South Africa

Richards Bay Harbour, which was constructed in early 1976, is South Africa’s largest and busiest port. Despite comprising mostly deep channels (>15 m) and associated harbour and shipping activities, the system still functions as an estuarine system. Information on the macrozoobenthic community structure in Richards Bay Harbour is scarce. This study was therefore conducted to examine the status of the macrobenthic community structure. Sediment and benthic samples were collected quarterly using a Van Veen grab during the period 2016–2017. The majority of habitat types had sediment compositions ranging from very fine sand to mud. The implication of this difference in sediment substrata was profound in the benthic abundance and distribution. Analyses of the benthic fauna identified 98 taxa, of which the tanaid Halmyrapseudes digitalis, the polychaetes Mediomastus capensis, Aphelochaeta marioni and Prionospio sexoculata and the brachyuran crab Paratylodiplax blephariskios were numerically abundant. Multivariate analyses performed using PRIMER and PERMANOVA indicated significant differences in community structure between sites and habitat types, with no significant differences between seasons. The intertidal mudflat areas in Richards Bay Harbour supported a more diverse assemblage, with habitat types strongly influencing the community structure. Despite this, habitat loss and degradation due to anthropogenic pressure from harbour and industrial activities were identified as potential threats to the overall abundance and distribution of macrozoobenthic organisms in Richards Bay Harbour. We conclude that despite anthropogenic pressures related to industrial and port activities, Richards Bay Harbour still contains estuarine habitat of high conservation importance that supports a diverse macrobenthic community.

Structure of benthic macroinvertebrates population in an area of Mopoyem Bay (Ebrie Lagoon, Côte d'Ivoire) exposed to the discharge of a fish farm effluents.

Discharges of untreated effluent from fish farming into the aquatic environment are a practice that can affect local biodiversity. This study was conducted to characterize, in the Ebrie Lagoon, the structure of benthic macroinvertebrates inhabiting an environment exposed to effluent discharges from fish farms. The benthic macroinvertebrates were collected with a Van Veen grab seasonally between August 2016 and July 2017 at the effluent discharge point in the lagoon and at a reference station out of anthropogenic activities. Identification of organisms was done using specialized keys. The results revealed that the proportion of tolerant macroinvertebrates is relatively high (47.74%) at the point of discharge of fish farming effluents into the Ebrie Lagoon. While at the reference station, macroinvertebrates population is dominated by sensitive and medium-sensitive taxa (93.53%). The benthic macroinvertebrates population, influenced by seasonal variations, exhibits peaks of abundance and diversity during the rainy seasons, while during the dry seasons, they strongly decline. Fish farming effluents dumped in Ebrie Lagoon lead to structural modifications of the local benthic macroinvertebrates population. These disturbances are intensified in dry seasons and attenuated in rainy seasons. This information should be taken into account in any decision to promote the responsible practice of fish farming and the sustainable management of water resources exploited for fish farming purposes.

Diversity and New Records of Polychaetes (Annelida) in the Sinop Peninsula, Turkey (Southern Black Sea)

Objective: This study determines the diversity of annelid polychaete species distributed around the coast of Sinop and to identify possible spatial and temporal variations of the Polychaeta community. Materials and Methods: Benthic material was collected from 8 stations using Van Veen grab between October 2013 and July 2014 on the soft bottom of Sinop Peninsula. Results: A total of 90 species belonging to 30 families were identified. Among them, Galathowenia cf. oculata, Rhodine loveni Malmgren, 1865, Paradoneis armata Glemarec, 1966, Paralacydonia paradoxa Fauvel, 1913 and Syllis cf. amica are new records for the Black Sea fauna and Glycera tridactyla Schmarda, 1861 is new for the Turkish coast of the Black Sea. Prionospio (Minuspio) maciolekae Dagli and Cinar, 2011, Micronephthys longicornis (Perejaslavtseva, 1891) and Protodorvillea kefersteini (McIntosh, 1869) were the most frequent and dominant species in the study area. The highest mean number of species (29 species) was found in spring at station G2; the lowest mean number of species (4 species) was determined at station G3 in winter. The highest mean density value (9470 ind. m-2) was determined at G2 station in summer; the lowest mean density value (357 ind. m-2) was calculated in autumn at station G5. Conclusion: The Polychaeta diversity on the soft bottom of the Sinop Peninsula was analyzed and four species were newly recorded for the Black Sea fauna and one for the Turkish Black Sea fauna.

Composition and spatiotemporal distribution of benthic macrofauna in a macrotidal estuary on the Amazonian Coast of the State of Maranhão, Brazil

The aim of the present study was to analyse the composition and spatiotemporal distribution of the benthic macrofauna in the estuary of the Perizes River (state of Maranhão, Brazil). Biological and environmental samples were collected at five sampling sites along the estuary during six campaigns covering the months of September, October and November 2016 (dry period) and February, March and April 2017 (wet period). Sampling was performed with a van Veen grab sampler (682cm2). Environmental variables as temperature, pH, salinity, dissolved oxygen, saturation and water transparency were measured and related to the biological data at each sampling site. After collection the samples were sieved through a 0.5 mm mesh and the organisms fixed in a 10% formaline solution. A total of 35,597 individuals belonging to 84 taxa were identified, corresponding to Insecta, Mollusca, Crustacea, Annelida, Nematoda, Nemertea, Sipuncula and Collembola. Polychaeta showed the greatest species richness, while Tanaidacea were the most abundant. No gradient was found throughout the sampling sites with regard to the environmental variables, but marked differences were found in the temporal distribution. The temporal distribution of the benthic macrofauna was influenced by salinity and rainfall. Oligochaeta and Tanaidacea were abundant at all sampling sites. Acari were abundant in the inner portion of the estuary, while the number of Ostracoda was very high in the outer portion. The structure of the macrobenthic community differed in composition from the majority of the studies on estuaries, with the dominance of Tanaidacea and Oligochaeta. The higher abundance of Tanaidacea is related to environments rich in fine sediments with organic matter and the occurrence of this characteristics was determinant for the distribution of other taxa. The results indicate that the wet period favours the establishment of the benthic community, as evidenced by the increase in diversity and equitability.

Quantitative validation of a sediment trap attached to the bottom of a fishing trawl for Polychaete sampling

Trawling is an important method for world fisheries production and it is the main source of livelihood of many artisanal communities along the Brazilian coast. Trawling is considered a high-impact modality deeply altering the seafloor and affecting the structure and composition of benthic communities, which are considered the bedrock of the marine food chain. Tests were run using a sediment trap attached to a trawl for collecting and analysing Polychaete samples. The aim of this work was to verify whether the samples collected in this trap can be treated quantitatively. A sampling experiment was conducted to compare samples obtained with the trap and three Van Veen grab samplers with apertures of 0.026 m2 0.035 m2 and 0.05 m2. The number indicators of abundance, taxonomic richness and Shannon diversity index were used to compare the samplers. The samplers were also compared using the Bray–Curtis similarity measure in taxonomic composition and accumulation curves for taxa. Linear and mixed models were applied to compare the numerical indicators and PERMANOVA was used to compare the similarities. The sediment trap attached to a trawl was more similar to the grab sampler with the smallest (S) aperture (0.026 m 2). The mean values of abundance and richness were lower than the other samplers. The sediment trap attached to a trawl proved a good sampler for diversity and evenness. Results show that the quantitative efficiency of the trawl mounted trap is different from the quantitative efficiency of the other samplers.

Does grab size influence sampled macrofauna composition? A test conducted on deep-sea communities in the northeast Atlantic

In deep-sea surveys, heavy gears are often preferred to effectively collect macro benthos while smaller samplers are sufficient in coastal and shallow areas. However, there are few comparative studies of the samples retained and results gained from different-sized grabs. To study the differences in sampling properties between a small (sampling area of 0.1 m2) and a large (0.25 m2) van Veen grab, 1 m2 of seafloor was sampled with each of the grab sizes at four test sites in the Barents- and Norwegian Sea; one inside a fjord and three offshore, across a depth range of 287–963 m. Overall, the small and large grab collected a comparable number of species and individuals: 248 and 233 species, and 6074 and 6143 individuals, respectively. The large grab retrieved the most species at the deepest location while the small grab collected more species at the other test sites. Based on internationally recommended 0.5 m2 sampling units, a variation in the total species richness per test site of 7–13% was found while the diversity indices (ES100 and H′) varied by less than 10%. Independent of grab size, a cluster and nMDS analysis showed four clearly separated sample-groups that correspond to the four test stations although the multivariate dispersion was consistently higher for the small grab. A SIMPROF test showed no grab size-dependent differences. ANOSIM and PERMANOVA tests showed differences between grab sizes for the deepest station, where a similar difference occurred also between samples of the same grab size. This station displayed the least faunal heterogeneity, indicating that faunal patchiness may influence any grab-size differences. The results indicate that the two van Veen grabs tested deliver comparable quantitative faunal compositions. For the small grab, however, numerous samples were rejected due to poor performance, resulting in increased sampling time, ship costs and a suggested biased sampling towards less heterogeneous sediments at the fjord site.

Impacts of land-based pollutants on water chemistry and benthic macroinvertebrates community in a coastal lagoon, Lagos, Nigeria

Tropical coastal waters are prone to increased influx of pollutants from land during the rains. The effects of pollution influx on the water and macrobenthic fauna of a coastal lagoon, Lagos, Nigeria were investigated. Six sampling stations were established at point sources of different pollutants inflow into the lagoon. Surface water temperature at each station was measured in situ. Water samples were collected using Hydrobios Water Sampler while benthic samples were collected using the Van-veen grab, and analysed in the laboratory following standard procedures. Result of water analysis shows high Turbidity (50.1 ± 9.0), Total Suspended Solids (79.5 ± 10.1), Total Organic Carbon (4.2 ± 1.9) and Nitrates (8.5 ± 0.6), and low Dissolved Oxygen (4.4 ± 0.7) indicating a deteriorating water quality. Tympanotonus fuscatus, Nereis diversicolor and Capitella capitata which are more tolerant to organic pollution were relatively higher in abundance than Clibanarius africana and Pachymelania aurita which are less tolerant. The low diversity and abundance of the benthic macroinvertebrates could be attributed to a high influx of pollutants from land which was exacerbated by the rainfall. The use of the benthic macroinvertebrates as bioindicators in the monitoring of the Lagos lagoon should be enhanced in order to forestall the increasing pollution menace and improve its ecosystem functions.

Sand size variability inside the hopper of a trailing suction dredger for beach nourishment purposes

Research about the variability of sand size inside the hopper of a trailing suction dredger has yet to be done, despite its importance for beach nourishment projects. In this study, several samples were taken using different methodologies during dredging for a particular case of beach nourishment on board one dredger. Sampling was carried out with a tube core and a Van Veen grab at the surface when the hopper was full of sand. The results showed problems with the Van Veen grab, the standard methodology used for sampling aboard a dredger. This method should be reconsidered in the future because surface samples were not representative of the whole hopper due to the bias of higher percentage of shell pieces. According to the results, the core tubes introduced by percussion were the only useful method in determining average sand parameters closer to the values obtained for the borrow site. Moreover, cores also showed a linear correlation between sand size and depth: D50 increased 20% from the surface to 1 m depth; this is a sixth of the hopper depth of this study case. Regrettably, the manual percussion procedure could not reach depths greater than 1 m.

Distribution and sources of polycyclic aromatic hydrocarbon (PAH) on sediment around makassar coast

This study conducts an analysis related to distribution and source of PAH in sediment around Makassar coast. Sediment sample has been taken up using Van Veen grab and put in a plastic sac, brought to laboratory, added with salt, stored in dried freezer, and followed for PAH analysis. Sample preparation has been carried out using DCM and n-hexane (1:1) solvent to obtain extract of organic matter (EOM). The EOM is fractionated to yield alkane fraction (F1) and aromatic fraction (F2) containing PAH. The GC-FID has been used to determine PAH concentration through analysis of F2. Validation of the analytical method applies linearity, LoD, and LoQ. The recovery test has fulfilled for all PAH compounds except for naphthalene and fluoranthene. The highest concentration of PAHs is found at station 7 with benzo(a)antracene 933.23±3.88 ppm and perylene 205.75±19.45 ppm. The lowest total concentration of PAHs is found at station 12 located at the estuary of Tello River caused by dilution from both river and sea water. The source of PAHs in sediment is generally from petrogenic and pirolytic process.

Macroinvertebrates’ Pollution Tolerance Index in Calabar River, Cross River State, Nigeria

A study was undertaken to determine the macroinvertebrates pollution tolerance index (PTI) in Calabar River, Cross River state, Nigeria. Five sampling stations were chosen along the river course: Ikot Okon Abasi, Tinapa, Unicem, Marina resort and Nsidung beach which were labeled stations 1, 2, 3, 4 and 5 respectively. Physico-chemical parameters; surface water temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), total dissolved solids (TDS) and total suspended solids (TSS) were measured using their respective meters while macroinvertebrates were sampled using a Van Veen grab, stained with Rose Bengal solution and identified under microscope. Macroinvertebrates pollution tolerance index was obtained using online software designed by Northern Kentucky Univeristy and Leaf Pack Network Biotic and Water Quality Calculator. The results obtained for physicochemical parameters showed the highest temperature as 29.90C in station five while the lowest was 26.40C in station one. pH was highest (6.60) in station five and lowest (5.52) in station one. DO was highest (4.4mg/L) in station four and lowest (3.0 mg/L) in station five while BOD was highest (3.2 mg/L) in station three and lowest (0.3 mg/L) in station one. An average total of 5366 macroinvertebrate individuals were encountered belonging to nine families and eleven species. Tubificidae had the lowest occurrence with 18 individuals which made up 0.3% of the total macroinvertebrates while Penaeidae had the highest occurrence with 2,455 individuals constituting 45.8% of the total count. Pollution tolerance index was highest (21) in station five and lowest (9) in station four with the water quality being generally poor. Hence, it is suggested that anthropogenic activities should be regulated and continuous monitoring of the river course should be carried out.

Mollusk Shell Debris Accumulation in the Seabed Derived from Coastal Fish Farming

Fish farm facilities become colonized by biofouling, and in situ cleaning activities may increase the accumulation of biofouling, mostly shell-hash, on the sediment. However, there is a lack of knowledge about the effect of fish farming on this process. We evaluated the effect of fish farming on shell-hash accumulation on sediments in three fish farms in the Western Mediterranean in Spain. On the one hand, coverage of non-degraded shell on the seabed was estimated using an underwater camera attached to a frame of 1 × 1 m. On the other hand, superficial sediment samples were taken by a Van-Veen grab, and from a subsample, shell-hash was sorted at the laboratory, dried, and weighted. A significant increase of shells on sediment was detected under fish farms compared with the other treatments, with average values of 53 g kg-1, and 1.12% of cover. Shell-hash at zones close to the fish farm cages (Zone of Influence located between 40 to 60 m from the closest cage) did not show statistical differences compared to the reference zones, 300–500 m away from the concession limits, but the shell cover showed statistical differences. Fish farming activities produce a local increase in the sedimentation rate of shells under the cages. The derived ecological consequences of this accumulation need to be further studied.

Natural and anthropogenic factors influencing abundance of the benthic macrofauna along the shelf and slope of the Gulf of Guinea, a large marine ecosystem off West Africa

Summary The West African continental margin belongs to the least known areas in terms of the ecology of benthic ecosystems. At the same time, this region is influenced by various threats associated with human activities, including industrialisation and oil excavation. Here, we analyse the abundance and distribution patterns of macrozoobenthic communities along the coast of Ghana. The material was collected in 2012 on nine transects at depths ranging from 25 to 1000 m. Over 200 quantitative samples were collected using a 0.1-m2 van Veen grab. Generally, the mean density of macrozoobenthos decreased gradually from the shallow zone (25 m: 231.4 ± 262.2 ind./0.1 m2) down to bathyal depths (1000 m: 55.4 ± 51.4 ind./0.1 m2), but we observed intermediate scale variability in distribution patterns among the transects along the Ghanaian coast. Analysis of environmental factors showed no evidence of substantial pollution, although levels of hydrocarbons, barium and some other toxic metals show some local increases at particular stations, especially on the continental slope. Cluster analysis based on Bray–Curtis similarity and abundance of higher taxonomic groups of macrofauna yielded five groups of stations, while SIMPER analysis demonstrated that polychaetes and amphipods contributed most significantly to within-group similarity. Canonical Correspondence Analysis demonstrated that PAH, THC and toxic metal levels (Ba, Cd, Pb), as well as oxygen concentration, were the most important factors structuring benthic communities.

First record of Nais elinguis Müller, 1773 (Annelida: Oligochaeta: Naididae), Spatio-temporal patterns of its population density and biomass production along two estuaries in the South Caspian Sea, Mazandaran Province, Iran

The cosmopolitan oligochaete worm, Nais elinguis, is common to fresh and brackish water habitats. This species was found while investigating the limnology of two rivers alongside the Iranian coasts and has not been reported in the Iranian freshwater fauna and Caspian Sea before. N. elinguis was collected bimonthly from Cheshmehkileh and Sardabrood estuaries using a Van Veen grab (0.03 m2) and Surber (0.1 m2, 0.2 mm-mesh size) with three replicates from 6 stations from November 2014 through September 2015. The results of temporal distribution showed that the highest and lowest density and biomass of this species were in January (242.2±84.45 ind m-2 and 0.105±0.035 g m-2) and in September (33.35±23.5 ind m-2 and 0.010±0.006 g m-2) respectively which were significantly different (p<0.05). Among the sampling stations, station (S1) within the river with freshwater showed higher density and biomass (273.5±87.35 ind m-2 and 0.116±0.036 g m-2) than riverine brackish station (S2) within the mouth (39.8±22.6 ind m-2 and 0.013±0.006 g m-2) and marine brackish station (S3) (0±0 ind m-2 and 0±0 g m-2) which were significantly different (p<0.05). Density and biomass of this species in Cheshmehkileh River and estuary were more than that in Sardabrood. A significant correlation (p<0.05) between the density and biomass of N. elinguis with environmental variables was found.

Benthic macro-faunal abundance and diversity and sediment distribution in Akhziv submarine canyon and the adjacent slope (eastern Levant Basin, Mediterranean Sea)

The Israeli coastline is generally characterized by a broad and shallow continental shelf. Akhziv submarine canyon (ASC), in its northern reach, creates a locally unique marine ecosystem. The present study is the first to investigate the benthic macro-fauna of ASC, in order to assess its importance as a potential productivity ‘hotspot’ within its ultra-oligotrophic surroundings. Seven research cruises were conducted during 2010-2013, along ASC’s two channels and at iso-bathic control sites on the adjacent slope (AS), encompassing 8 sampling stations, at depths of 40-450 m. Bottom samples were collected by a Van Veen Grab, gravity corer and a GOMEX box corer. The infauna (≥500 µm) were counted and identified to the lowest possible taxonomic level. Sediments were analysed for grain size &amp; composition and total organic carbon concentration. Mean benthic macro-faunal abundance (individuals/500ml ± SD) was higher inside the canyon (13.0±19.4) compared to the AS (2.9±3.3) (p=0.004), as was estimated true taxon richness (Chao1): 42.2 versus 10, respectively. Sediments’ mode grain size was found to be significantly higher in ASC’s eastern channel compared to AS (p=0.028), along with sand enrichment of up to 36%. The higher macrofaunal abundance and taxon richness may relate to a more heterogeneous sea bed provided by the higher diversity in grain size existing inside ASC. A relatively rich benthic realm, such as that observed in the ASC, may serve as a refuge for certain species and by hosting a relatively diverse assemblage, stands a better chance of adapting to changing conditions such as climate change.

Planktonic foraminifera as indicators of oceanographic complexity on the southern Caribbean Sea continental shelf

The southern Caribbean Sea over the northern South American continental shelf is oceanographically complex. It is subject to (1) widespread coastal upwelling, (2) wakes and eddies in the NW-flowing Guiana and Caribbean Currents to the lee of islands, and (3) the hypopycnal Orinoco River plume. Upwelled water is dispersed NW along high-productivity filaments. Offshore northern Trinidad, an intra-plume front separates higher-productivity Orinoco-derived water to the west from lower-productivity Amazon-derived water. This paper examines planktonic foraminiferal assemblages in surface sediment samples (a) below upwelling foci in the Gulf of Venezuela (GoV). North of Lake Maracaibo, and (b) at an upwelling focus in the North Coast Marine Area (NCMA) offshore northern Trinidad, near but west of the intra-plume front. The samples were collected for previous studies and only certain size fractions, which differed between the study areas, were available for current study.Samples from the GoV (>250 μm fraction; taken using an Alpine corer or a Petersen dredge) were assigned a priori to groups underlying upwelled and non-upwelled water. Discriminant analysis after cluster analysis confirmed these assignments. Total recovery was dominated by Neogloboquadrina dutertrei with lesser Globigerinoides ruberpink and the upwelling indicator Globigerina bulloides. All four non-upwelled samples, co-dominated by N. dutertrei and Gs. ruberpink, reflect seasonal freshwater outflow from Lake Maracaibo. Five upwelled-area samples were dominated by G. bulloides with subdominant N. dutertrei or Globigerinoides ruber Morphotype B. The remaining two upwelled samples (dominant N. dutertrei, subdominant Gs. ruber Morphotype A) apparently reflect the transition between upwelling and non-upwelling areas. The mean proportions of assemblages as Trilobatus sacculifer Morphotype A did not differ markedly between the upwelled and non-upwelled GoV clusters. This morphotype was absent from the Gulf proper but present to the north.NCMA total recovery (>150 μm fraction; samples taken using a van Veen grab) was dominated by Gs. ruber Morphotype B. Cluster analysis here indicated three clusters: Cluster 1, proximal to the intra-plume front; Cluster 2, distal to the intra-plume front; and Cluster 3, scattered throughout the NCMA. Upwelling was pervasive, canonical variate analysis (CVA) verifying that G. bulloides did not differentiate the clusters. Instead, these clusters were differentiated by Gs. ruber Morphotype B only, the proportional abundance of which was highest in Cluster I and lowest in Cluster 2. This pattern indicates that the influence of the Orinoco plume on assemblage composition is stronger than that of upwelling, Cluster 1 reflecting higher productivity near the front.