Polychlorinated biphenyls (PCBs) were quantified in 18 surface sediment samples, 1 sediment core, and several mangrove tissue samples collected in Jobos Bay, Puerto Rico in September 2013. Total PCBs ...in surface sediments ranged from 0.42 to 1232ngg−1 dw. Generally, higher levels were observed near-shore close to urban and industrial areas. The levels suggest significant pollution in Jobos Bay with respect to PCBs. Two-thirds of the sites were dominated by lighter PCB congeners (tri- to penta-chlorinated PCBs) while one-third had heavy PCB congeners (hexa- to octa-chlorinated PCBs) dominant. Total PCBs in a sediment core indicated levels fluctuating according to historical usage patterns. Total PCBs were measured in mangal leaves (14–747ngg−1 dw), roots (0.26–120ngg−1 dw), and seeds (16–93ngg−1 dw), suggesting bioaccumulation from sediments. This is the first report of a historical profile of PCBs in the study area and of PCB bioaccumulation in mangroves. This article provides new and useful information on PCBs in the Caribbean area of the GRULAC region.
A - agriculture, B - urban, C - thermoeclectric plant, D - metal manufacturing, E - pharmaceutical, F - superfund site. G - petrochemical, H - chlorinated underwater pipe Display omitted
•PCBs were measured in sediments (surface and a core) and mangroves in Puerto Rico.•Levels and congener composition of PCBs were discussed.•Surface sediment levels consistent with anthropogenic input from surrounding areas.•PCB profiles from the sediment core were consistent with historical usage patterns.•Results indicated bioaccumulation of PCBs in mangroves in the study area.
Coral reefs worldwide are degrading at alarming rates due to local and global stressors. There are ongoing needs for bioindicator systems that can be used to assess reef health status, the potential ...for recovery following destructive events such as tropical storms, and for the success of coral transplants. Benthic foraminiferal shells are ubiquitous components of carbonate sediment in reef environments that can be sampled at minimal cost and environmental impact. Here we review the development and application of the FoRAM Index (FI), which provides a bioindicator metric for water quality that supports reef accretion. We outline the strengths and limitations of the FI, and propose how it can be applied more effectively across different geographical regions.
Display omitted
•FoRAM Index is a powerful water quality management tool in coral reefs.•FoRAM Index must be modified to suit location-specific assemblages.•Methodological modifications will ensure usability of the index worldwide.
Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and ...central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present‐day volcanism is confined to the region with the highest heat flow.
Key Points
Heat flow in the Lesser Antilles is similar to other volcanic arcs
No evidence for subsurface fluid flow
Volcanism is confined to the region with high heat flow
Marine sediments around volcanic islands contain an archive of volcaniclastic deposits, which can be used to reconstruct the volcanic history of an area. Such records hold many advantages over often ...incomplete terrestrial data sets. This includes the potential for precise and continuous dating of intervening sediment packages, which allow a correlatable and temporally constrained stratigraphic framework to be constructed across multiple marine sediment cores. Here we discuss a marine record of eruptive and mass‐wasting events spanning ∼250 ka offshore of Montserrat, using new data from IODP Expedition 340, as well as previously collected cores. By using a combination of high‐resolution oxygen isotope stratigraphy, AMS radiocarbon dating, biostratigraphy of foraminifera and calcareous nannofossils, and clast componentry, we identify five major events at Soufriere Hills volcano since 250 ka. Lateral correlations of these events across sediment cores collected offshore of the south and south west of Montserrat have improved our understanding of the timing, extent and associations between events in this area. Correlations reveal that powerful and potentially erosive density‐currents traveled at least 33 km offshore and demonstrate that marine deposits, produced by eruption‐fed and mass‐wasting events on volcanic islands, are heterogeneous in their spatial distribution. Thus, multiple drilling/coring sites are needed to reconstruct the full chronostratigraphy of volcanic islands. This multidisciplinary study will be vital to interpreting the chaotic records of submarine landslides at other sites drilled during Expedition 340 and provides a framework that can be applied to the stratigraphic analysis of sediments surrounding other volcanic islands.
Key Points
Biostratigraphy, isotope geochemistry, and clast componentry of IODP Site U1396
Deposits are correlated across sites to the south and south west of Montserrat
Results highlight the spatial heterogeneity of deposits around volcanic islands
The Apapa and Badagry creeks in Nigeria are a corridor of long-term anthropogenic activities, including mangrove removal, urban expansion, and industrialization. Consequently, this uncontrolled ...development led to the release of untreated effluents and wastes, which resulted in sediment and water quality degradation. This area has the highest degree of pollution (Enrichment and Contamination Factors) especially north of Tincan Island where potentially toxic element (PTE) depocenters occur. Our data shows that salinity and pH are the two main factors favoring foraminiferal distributions, but the sediments in the depocenters with the highest degree of PTE pollution are barren of foraminifera. Bioavailable sediment-bound PTEs have been found to negatively impact the assemblage distribution and diversity. It is important to highlight that dissolved phosphorous was the only PTE that negatively impacted species richness. This study highlights the significance of implementing PTE bioavailability as an integral part of ecosystem functioning in all nearshore environments.
Display omitted
•Ammonia and Ammotium species dominated the foraminiferal assemblage.•Salinity and pH gradients controlled the spatial distribution of PTEs.•Bioavailable PTEs (F4-organic-bound fraction) negatively impacted the foraminifers.•Phosphorous dissolved in water negatively impacted species richness.
To assess "bottom-up" to "top-down" trophic transfer, we analyze As, Cd, Co, Cr, Cu, Hg, Ni, Se, Zn, Fe, and Mn from two sediment chemical fractions (exchangeable and organic-bound), red mangrove ...(Rhizophora mangle) leaves, and fiddler crab (M. rapax) soft tissues from Isla del Carmen, Yucatán Peninsula. Both mechanisms were observed indictive that R. mangle and M. rapax indeed bioaccumulated the toxic elements from the different matrices with the latter being a macro-concentrator only for Cu and Zn. Although the modified Geo-accumulation factor (combined exchangeable and organic matter fractions) suggested that the studied sites are practically "uncontaminated", Hg is the only toxic element to be having a "moderately to strongly" impact. Data shows how M. rapax had progressively bioaccumulated Hg, but no biomagnification could be corroborated given that the fiddler crab behaved as a de-concentrator.
•Biotic indices based on benthic foraminifera are efficient tools to evaluate pollution in the Gulf of Gabes (Tunisia).•Indices based on epiphytic foraminifera reflect environmental conditions in ...seagrass meadows.•The Djerba Island considered as “pristine” seems also affected by pollution.
Biotic indices are tools to assess the ecological status of marine systems, and can be based on different metrics (such as ecological groups, specific diversity). The present study applies five biotic indices based on living (stained) benthic foraminiferal assemblages to assess ecological conditions in a wide area of the Mediterranean Sea in the heavily polluted Gulf of Gabes and along the western and eastern coasts of the Djerba Island, with the eastern coast considered as “pristine”. The applied indices are based on epiphytic foraminifera e.g., the “long versus short life span” index (ILS) and the modified FoRAM-Index (FI’), benthic foraminiferal assemblage composition and diversity, e.g., the Tolerant Species index (TSstd), the Foram Stress Index (FSI), the diversity Index (exp(H’bc)) and the newly developed Foram-AZTI Marine Biotic Index (Foram-AMBI). This latter index was tested using species of benthic foraminifera presently assigned to ecological groups in the Mediterranean Sea. All indices confirm good ecological conditions eastern of Djerba. The FI’ and ILS, % TSstd, FSI, indicate a severe anthropogenic impact especially in the central part of the Gulf of Gabes, next to the phosphate industry of Skhira and along the western coast of Djerba Island and confirm direct observations and geochemical data. The indices based on epiphytic foraminifera seem to better reflect actual environmental conditions in the investigated region because of the extended Posidonia oceanica meadow in the area. The exp(H’bc) reflects lower degrees of pollution. The application of the Foram-AMBI index presents limitations that prevent its current use. It strongly underestimates the pollution impact along the Tunisian coast, and additional work is needed to increase the number of species attributed to ecological groups and to possibly modify the coefficients to be used in its equation.
The Apapa-Badagry Creek in southwestern Nigeria is a largely man-impact area being bordered to the north by sprawling residential estates and industries and to the south by recreational centers and ...villages. It also houses the Lagos Harbour and petroleum terminals. Sewage from these complexes is discharged into the creek, thus the pollutants impact the living faunas, such as benthic foraminifera. The implications of organic matter (OM) type and source on the diversity and abundance of living benthic foraminifera in the Apapa-Badagry Creek are investigated. Results show that the distribution of the living benthic foraminifera in this area is largely dependent on sediment type, OM source, and salinity and that only ten species of living benthic foraminifera thrive in muddy sediments with TOC < 2 wt%. Carbon and nitrogen isotopes (δ13C and δ15N) and C/N molar ratios reveal that the OM is of terrestrial origin (C3 plants) and that it is not the ideal food for benthic foraminifera in this estuary, in particular, for Ammonia species.
•The Apapa-Badagry Creek represents a typical marginal marine environment under great anthropogenic stress.•Benthic foraminifera are used as ecosystem indicators.•Stable isotopes of carbon and nitrogen (δ13C and δ15N) reveal the terrestrial origin of the sedimented organic matter.•Changes in assemblage structure and distribution are due to presence of organic matter nutrients, and salinity gradients.
•Tropical estuary in Puerto Rico has experienced anthropogenic alterations.•Distributions of Potentially toxic elements are controlled by sediment textures.•Foraminifers are applied as ...bioindicators.•Anoxia controls fractionation of PTEs and foraminiferal distributions.•Acid-soluble (carbonate) bioavailable PTE fraction does not correlate with benthic foraminifers.
Torrecillas Lagoon, on the north coast of Puerto Rico, has experienced extensive anthropogenic influence over the past 200 years. Elevated concentrations of Potentially Toxic Elements (PTEs) in bulk sediment (Cu, Zn, Pb, Ni, Cr, Li, V, Fe, As, Se, and Mn) have been reported in surficial sediments and have relatively uniform spatial distributions. Areas with higher concentrations are associated with a higher percentage of total organic carbon (TOC) and percent mud (mud), as well as anoxic conditions. Ammonia beccarii, Quinqueloculina rhodiensis, and Triloculina oblonga are the dominant foraminifers in the lagoon and are characteristic of stressed coastal environments. Bulk concentrations of Cu-Zn-Fe are negatively correlated with numerous foraminiferal taxa, absolute abundances, and diversity indices, though very few correlations with the bioavailable counterparts (F2Tess-bioavailable) are observed. Similarly, relative abundances of Quinqueloculina and Triloculina positively correlate with bulk Cu-Zn-Fe but not with F2Tess-bioavailable. The waters in Torrecillas lagoon show strong stratification, with hypoxic/anoxic (dissolved oxygen <3mg/L) and corrosive (pH<7.4) conditions below 4m depth. The presence of such strong gradients in very shallow water represents a dynamic chemical environment, with changes occurring on day-night cycles, tidal cycles, and especially with storm activity that induces mixing of otherwise highly stratified, very localized waters. Recognizing the potential for sequestered PTEs to be remobilized is an essential insight for coastal management agencies that must assess the risks of existing PTEs during coastal engineering activities (e.g., dredge and fill activities) and major storm events. Exchangeable and oxidizable fractions are likely more bioavailable than acid-soluble fractions in influencing the ecology of foraminifers under most circumstances.
Fiddler crabs are known as “eco-engineers” who maintain habitat health through sediment bioturbation. They regularly interact with microplastics (MPs) due to their contact with the sediment. In this ...study we compared MPs concentration between burrows and pellets resulting from bioturbation, and MPs bioaccumulation in the soft tissues of Minuca rapax (Smith, 1870), along a gradient of urbanization in Isla del Carmen, southern Gulf of Mexico. Overall, MPs shape and color in the pellets and in the tissues reflected those of the burrow's sediments. MPs were more abundant and diverse in burrows (9 ± 12 MPs.g−1) than in pellets (5 ± 5 MPs.g−1) or in the soft tissues (1.3 ± 1.2 MPs.g−1). Bioturbation can concentrate MPs in pellets and tissues, depending on the MPs contamination and urbanization level. M. rapax is an important structuring agent of sedimentary MPs, showing a strong top-down translocation of MPs in subtropical tidal flats.
Display omitted
•Bioturbation activity of the fiddle crab Minuca rapax can influence MP distribution in sediments.•Microplastics were more abundant and diverse in burrow sediment than in pellets resulting from bioturbation.•It was not observed an ability to discriminate between sizes, colors, and shape of microplastics by Minuca rapax.•MP particles were more bioaccumulated in sites with the highest amount of MP in the sediment burrows.•Minuca rapax causes a top-down effect of microplastics in subtropical tidal flats.
PDF
