Offshore Sampling Stations Research Articles

Salinity significantly reduces plastic-degrading bacteria from rivers to oceans

Microplastics (MPs) are found in rivers and offshore areas. However, there is a lack of detailed research on the changes of surface microbial species attached to MPs when MPs enter the sea. Moreover, no study has been conducted on changes to plastic-degrading bacteria during this process. In this study, using rivers and offshore in Macau, China as examples, bacterial diversity and bacterial species composition attached to surface water and MPs at four river sampling stations and four offshore sampling stations around Macau were studied. Plastic-degrading bacteria, plastic-related metabolic processes, and plastic-related enzymes were analyzed. The results showed that MPs-attached bacteria in rivers and offshore were different with the planktonic bacteria (PB). The proportion of major families on the surface of MPs continued to increase from rivers to estuaries. MPs could significantly enrich plastic-degrading bacteria both in rivers and offshore. The proportion of plastic-related metabolic pathways on the surface bacteria of MPs in rivers was higher than that in offshore waters. Bacteria on the surface of MPs in rivers may induce higher plastic degradation than offshore. Salinity significantly alters the distribution of plastic-degrading bacteria. MPs may degrade more slowly in the oceans, posing a long-term threat to marine life and human health.

Sources and Distribution of Organic Matter in Coastal Area of Muang Chonburi District, Eastern Thailand: Using Carbon and Nitrogen Stable Isotopes

The sources and spatial distribution of organic matter were investigated in the nearshore area receiving untreated urban wastewater and offshore areas containing bivalve mariculture in Muang Chonburi District. Content, elemental, carbon, and nitrogen isotopic analyses in particulate organic matter (POM) and surface sediments were performed. We found particulate organic carbon (POC), δ13C, and δ15N of POM ranging from 435.0-5,247.7 µg/L, -27.7 to -22.0 ‰, and 1.7-8.6 ‰, respectively, whereas total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N in sediment were 3.5-76.9 µg/g, 0.8-8.3 µg/g, -25.7 to -22.9 ‰ and 2.6-6.0 ‰, respectively. These values show significant differences between nearshore and offshore sampling stations wherein accumulation of organic matter was high in the nearshore and decreased with greater distance offshore, with some retained in the bivalve farming area. The results from a mixing model indicated that organic matter in POM and sediment were initially derived from anthropogenic organic matter. In contrast to the offshore water which had organic matter derived from marine organic matter. This study highlights the distribution of anthropogenic organic waste released to coastal waters with plenty of bivalve farms such as green mussels and oysters. The results can be used to advise national strategies regarding bivalve aquaculture zoning and seafood safety policies going forward.

The allochthonous material input in the trophodynamic system of the shelf sediments of the Gulf of Tigullio (Ligurian Sea, NW Mediterranean)

The organic allochthonous material input in the benthic system of a NW Mediterranean shelf area was studied using a three-pronged approach, focusing firstly on the evaluation of the sedimentary stable isotope ratios and organic matter (OM) composition, then on the OM recycling processes performed by the microbial organisms, and finally on the potential trophic relationships between the macrobenthic organisms. The highest allochthonous signal, indicating continental input, was observed within the 50-m isobath, while at the 80-m isobath the marine signal was higher, pointing to a rather low continental influence approximately 5 km from the shore. Heavier rainfall, often generating abrupt allochthonous inputs by river outfalls, led to a wider spread of fine sediment particles. Carbohydrates were the compounds that best represented the continental input and these compounds were associated with potential recycling activities by microbiota, pointing to the entry of these C-containing allochthonous materials into the microbial food web. The macrofaunal deposit-feeders used sedimentary OM characterised by a continental signature as a food source, although the isotopic ratios of the organisms also pointed to selective feeding on materials that had a marine signature, especially at our offshore sampling stations. Predators fed on deposit- or suspension-feeders, with a potential selection of the latter during the highest inputs of continental materials occurring in winter.

Occurrence, distribution and prey items of juvenile marbled sole Pseudopleuronectes yokohamae around a submarine groundwater seepage on a tidal flat in southwestern Japan

Occurrence, distribution and prey items of juvenile marbled sole Pseudopleuronectes yokohamae were investigated around a submarine groundwater seepage on a tidal flat in southwestern Japan. Spatial distribution of radon-222 (222Rn) concentration in water showed more submarine groundwater seepage in the offshore area. The lower salinities at offshore sampling stations corresponded with the highest 222Rn concentrations. Juvenile marbled sole were collected from March through June with seasonal peak in April in 2013 and 2014. Mean abundance of juvenile marbled sole was highest at the second most offshore station where high submarine groundwater seepage was indicated. Major prey items in the stomachs of the marbled sole at the post-settlement stage (10–40mm) were small crustaceans such as cumaceans and gammarids, which were partially replaced with polychaetes in larger juveniles (40–50mm). Abundance of these major prey items was also higher at offshore stations. A negative correlation between gammarid abundance and salinity indicated a higher concentration of gammarids around the area of high submarine groundwater seepage, a pattern not observed for the other major prey organisms. Stable isotope analysis showed greater dependence of post-settlement stage marbled sole on the small crustaceans with low δ13C indicating that nutrients of terrestrial origin contribute to production of the juvenile marbled sole on the tidal flat.

Integration of ecosystem-based models into an existing interactive web-based tool for improved aquaculture decision-making

Proper site selection is critical to the development and expansion of marine aquaculture. Major considerations for site selection include: potential for competing uses, environmental interactions, and animal productivity. Two types of existing site selection tools, mapping and modeling, have proven useful independently, and in some recent studies have proven useful when used together. GIS-based mapping tools have become important in the decision-making process. These tools provide access to marine and coastal datasets allowing farmers and extension agents to gather information on availability of cultivation sites. They are also used by resource managers to assess potential use conflicts (e.g. existence of commercial fishing, mooring areas, fixed fishing gear) and possible environmental interactions (e.g. presence of seagrasses, contaminants, threatened or endangered species). Models have been used separately to predict animal growth, farm productivity, and farm-related effects on the surrounding water and sediment quality.The integration of the Farm Aquaculture Resource Management (FARM) model (http://www.farmscale.org) into the U.S. state of Connecticut's Aquaculture Mapping Atlas (http://seagrant.uconn.edu/whatwedo/aquaculture/shellmap.php) was tested in three geographically distinct waterbodies within Connecticut (CT) waters of Long Island Sound. Nearshore waters within the towns of Mystic, Milford, and Westport were selected as pilot locations to determine usability and capability of the combined tools. Data from two long-term offshore sampling stations adjacent to existing shellfish leases were used to test spatial and temporal sampling variability impacts on model results. Partnerships with local monitoring programs and growers were important for acquisition of water quality data, oyster measurement data, and information about local culture practices. All sites were deemed suitable for oyster aquaculture based on model results that predicted Moderate to High growth based on estimated time to reach harvest size from one in (2.54cm) seed oysters (Crassostrea virginica). Time to harvest varied from 282days (High growth) to 645days (Moderate growth) among the 22 stations in the three nearshore sites, and 724–956days (Moderate growth) at the two offshore sites. Results from the two long-term offshore stations indicate that data from the same year must be used when comparing production-based suitability of sites. Addition of potential production estimates improved the ability to select between suitable mapping-based sites. This mapping and modeling combination should be encouraged to provide a strong basis for successful siting and expansion of aquaculture while minimizing user conflict and adverse environmental interactions. This approach may be particularly useful in waterbodies where shellfish aquaculture is possible but is not well established.

English

Three short sediment cores (12-32 cm) from South China Sea off Southern Terengganu were collected during May (post-Northeast monsoon) and September (pre-Northeast monsoon) 2007. The concentration of total organic carbon (TOC) obtained ranged from 0.41-2.23 and 0.38-2.31% during post and pre-monsoon, respectively. TOC concentration was found to decrease with depth and distance from the coast and river mouth. In particular, station with close proximity to the coast exhibits most pronounced variation of TOC with depth. Besides spatial variation, it is noted that the seasonal variations also considerably affect the distribution and concentrations of TOC, where both near and offshore sampling stations showed significant variations in TOC content during May and September sampling. These findings suggest the importance of terrestrial organic carbon flux, physical mixing and seasonal variations in regulating the concentration and distribution of the organic carbon in the study area.

Spatiotemporal distribution patterns of dissolved methane in lakes: How accurate are the current estimations of the diffusive flux path?

AbstractLakes have been identified as an important source of atmospheric methane. Here the spatiotemporal distribution of dissolved methane was measured in a medium‐sized freshwater lake. The data reveal that littoral zones (nearshore, shallow) are the predominant source of methane. Offshore‐directed gradients of dissolved methane suggest the transport of methane from the nearshore zone to the pelagic epilimnion. The distribution patterns of epilimnetic methane were highly heterogeneous, independent of the mean lake‐wide methane concentration. Consequently, the diffusive flux of methane to the atmosphere strongly varies with location in the lake. A comparison of the diffusive methane flux from different offshore sampling stations indicates that single‐point measurements are not necessarily sufficient to estimate lake‐wide emissions to the atmosphere accurately. Thus, spatially resolved measurements of methane emissions are needed to improve the reliability of estimates of the methane that lakes contribute to the global methane budget.

Factors controlling variability in nearshore fecal pollution: The effects of mortality

A suite of physical–biological models was used to explore the importance of mortality and fluid dynamics in controlling concentrations of fecal indicator bacteria (FIB) at Huntington Beach, CA. An advection–diffusion (AD) model provided a baseline to assess improvements in model skill with the inclusion of mortality. Six forms of mortality were modeled. All mortality models performed better than the AD model, especially at offshore sampling stations, where model skill increased from <0.18 to >0.50 (Escherichia coli) or <−0.14 to >0.30 (Enterococcus). Models including cross-shore variable mortality rates reproduced FIB decay accurately (p<0.05) at more stations than models without. This finding is consistent with analyses that revealed cross-shore variability in Enterococcus species composition and solar dose response. No best model was identified for Enterococcus, as all models including cross-shore variable mortality performed similarly. The best model for E. coli included solar-dependent and cross-shore variable mortality.

Spatial and seasonal variations of subtidal free-living nematode assemblages in the northern Beibu Gulf, South China Sea

This study determined the spatial and seasonal density, number of genera, genera composition, maturity index and trophic structure of free-living nematode assemblages in the subtidal waters of the northern Beibu Gulf, South China Sea, and explored whether these five biotic characteristics were related to various environmental variables. Based on the data derived from samples collected seasonally at nine stations, the mean densities of nematodes decreased from alongshore to offshore station in the northern Beibu Gulf. However, the number of nematode genera increased from alongshore to offshore station. Non-parametric multidimensional scaling analysis showed no clear seasonal changes for nematode assemblages in most sampling stations. Higher densities of the generaElzaliaandTricomawere found in offshore sampling stations, and a higher density of the genusCheironchuswas found in alongshore sampling stations. The mean percentage of each feeding type compared to the total numbers was highest in epigrowth feeders (2A), second highest in non-selective deposit feeders (1B), third highest in predators (2B), and lowest in selective deposit feeders (1A). There were significant negative correlations between nematode density and water depth and temperature; significant positive correlations between the number of nematode genera and water depth and salinity; and significant negative correlation between the maturity index of the nematode assemblage and organic matter. BIOENV analysis indicated that water depth, salinity, pH, median sediment particle size and organic matter were the most correlated combination of environmental variables affecting the nematode assemblages.

Larval fish assemblages and water mass structure off the oligotrophic south‐western Australian coast

AbstractLarval fish assemblages were sampled using replicated oblique bongo net tows along a five‐station transect extending from inshore (18 m depth) to offshore waters (1000 m depth) off temperate south‐western Australia. A total of 148 taxa from 93 teleost families were identified. Larvae of Gobiidae and Blenniidae were abundant inshore, while larvae of pelagic and reef‐dwelling families, such as Clupeidae, Engraulidae, Carangidae and Labridae were common in continental shelf waters. Larvae of oceanic families, particularly Myctophidae, Phosichthyidae and Gonostomatidae, dominated offshore assemblages. Multivariate statistical analyses revealed larval fish assemblages to have a strong temporal and spatial structure. Assemblages were distinct among seasons, and among inshore, continental shelf and offshore sampling stations. Inshore larval fish assemblages were the most seasonal, in terms of species composition and abundance, with offshore assemblages the least seasonal. However, larval fish assemblages were most closely correlated to water mass, with species distributions reflecting both cross‐shelf and along‐shore oceanographic processes and events. Similarity profile (SIMPROF) analysis suggested the presence of twelve distinct larval fish assemblages, largely delineated by water depth and season. The strength and position of the warm, southward flowing Leeuwin Current, and of the cool, seasonal, northward flowing Capes Current, were shown to drive much of the variability in the marine environment, and thus larval fish assemblages.

Utilizing gamma isotope tracers to determine sediment source at reef sites near the Charleston Ocean Dredged Material Disposal Site

The Charleston, South Carolina Ocean Dredged Material Disposal Site (ODMDS) has been heavily utilized as a disposal site for dredged material resulting from maintenance and channel deepening in the Charleston Harbor. Continuous monitoring by the South Carolina Department of Natural Resources at the ODMDS has indicated the presence of fine-grained sediment within the monitoring zones. However, since the Charleston Harbor is formed by the conjunction of three rivers, it has been suggested that some of the fine-grained sediment surrounding the ODMDS could be due to river transport rather than solely by disposal activities. In order to trace the outflow of sediment from the harbor, natural and man-made isotopes were utilized. 7Be (natural cosmogenic isotope) and 137Cs (man-made isotope) are often associated with estuarine sediments. Both isotopes were used as tracers in an attempt to determine the extent of density driven sediment flow from the Charleston Harbor. 7Be was detected in many of the offshore sampling stations indicating a direct correlation to the harbor. 137Cs was only found in one sediment trap sample offshore, but none the less indicated some transport from the harbor. Further study for utilizing isotopic tracers in determining offshore sediment transport is still being conducted at the disposal site. It is anticipated that further 7Be and 137Cs isotopic monitoring offshore Charleston will aid in determining the role that tidal and density driven sediments play in the sediment budgets at the hard bottom reef sites.

Flux estimates and sedimentation of polychlorinated naphthalenes in the northern part of the baltic sea

The concentrations and fluxes of polychlorinated naphthalenes (PCNs) were measured in surface sediments, and settling particulate matter collected in sediment traps, at two coastal and two offshore sampling stations in the Gulf of Bothnia, northern Baltic Sea, Sweden. The PCN concentrations (of tetra- to hepta-chloro congeners) in the surface sediments ranged from 0.27 to 2.8 ng/g dry weight and were of the same order of magnitude as background concentrations reported previously in Europe. The PCN fluxes in the southern basin (0.93 and 0.86 μg/m 2/year) of the Gulf of Bothnia were higher than those in the northern basin (0.58 and 0.49 μg/m 2/year); they were also higher near the coast than in the open sea. These PCN fluxes are similar to the pre-industrial levels determined from lake sediments in northwest England. The PCN homologue distribution changed from a relatively even distribution in samples collected near the coast, to TeCNs dominating in the samples from the open sea. This indicates that higher chlorinated PCNs are deposited and retained in sediments to a higher degree near the coast. The total annual deposition of PCNs in sediments in the Gulf of Bothnia was estimated to be 91 kg/year.

The Role of Tidal Salt Marsh as an Energy Source for Marine Transient and Resident Finfishes: A Stable Isotope Approach

Stable isotope ratios of carbon, nitrogen, and sulfur (δ13C, δ15N, and δ34S) in bay anchovy Anchoa mitchilli and white perch Morone americana from Delaware Bay were a function of capture location and, for restored tidal salt marshes, possibly a function of the relative position of the marsh restoration trajectory. White perch collected in polyhaline restoration and reference (Moore's Beach) sites had stable isotope signatures that reflected contributions from both benthic microalgae and Spartina alterniflora. Isotope values from white perch captured at the reference site were slightly enriched compared with those captured at the restoration sites. At upper estuary oligo–mesohaline locations, Phragmites australis contributed to the isotopic composition of both species. Although P. australis was not dominant at the reference marsh (Mad Horse Creek), it also seemed to influence the flow of nutrients into these species. White perch were not collected in open waters of Delaware Bay, but bay anchovy were abundant at offshore sampling stations. A striking result of this study was that stable isotopes that originated in macrophytes and benthic microalgae of salt marshes occurred ubiquitously among bay anchovy collected several kilometers from shore. Interestingly, fish from Mad Horse Creek, a reference marsh where Phragmites was abundant only along creek banks, were intermediate in their isotopic composition. Although benthic microalgal signatures varied both within and among sites, the isotopic composition of bay anchovy and white perch was clearly influenced by these primary producers across all marsh types. Particulate organic matter (POM) appeared to play a lesser role in bay anchovy and white perch nutrition, although depletion of POM sulfur due to the presence of inorganic sulfur may have led to underestimates of the contribution of phytoplankton. Further studies are required to elucidate the relative role of phytoplankton in the trophodynamics of these species.

Sedimentation rate and bioturbation in the Arabian Gulf

The Arabian Gulf is a shallow marginal sea of the Indian Ocean. It is a semi-closed basin which extends for nearly 1000 km from Shatt Al-Arab, the nexus of the Tigris, Euphrates, and Karun Rivers in the northwest, to the Strait of Hormuz in the southeast, and covers a surface area of about 239 000 km 2. In addition to Shatt Al-Arab, river inflow into the Gulf occurs primarily on the Iranian northeastern side, the estuary of major rivers such as the Hendijan, the Rud Hilleh, and the Mand. The bathymetry of the Inner Sea basin shallows to the northwest and to the west coast (Reynolds 1993), whilst the basin floor is asymmetric with its axis lying close to the Iranian Coast. It slopes gradually from the shallow deltaic northern part to deeper waters in the south, with the depth rarely exceeding 100 m (only 36 m on average). It is a region of great interest to environmental scientists. It is bordered by rock sequences which contain the richest oil deposits in the world, and one-third of world oil energy is transported through this body of water. Despite the tremendous stress exerted by oil production and transportation, this area was also a subject of man-made pollution. Between 19 and 30 January 1991, an estimated 10.8 million (1.7 Mm 3) barrels of oil were spilled deliberately by Iraqi troops in the Gulf waters, mainly from seven abandoned tankers and the Al-Ahmadi Sea Island terminal near the coast of Kuwait, in addition to smaller discharges from the Iraqi Mina Al-Bakr terminal and nearby sunken tankers, and the Saudi Ras Al-Zur refinery at Mina Sa'ud (Tawfiq and Olsen 1993). It is also estimated that 8 million (1.3 Mm 3) barrels of oil fallout from the smoke plumes of the 727 oil well blowouts and fires in Kuwait oil fields, started in late February 1991 by departing Iraqi troops, were deposited in the Gulf marine environment (Al-Rabeh et al. 1992; Literathy 1993). The airborne fallouts, which contained oil-combustion products, particularly ash, and trace metals originally present in the burnt crude oil, doubled the size of the oil slick and made the event the largest of its kind in the history of marine pollution (Reynolds 1993). As part of the efforts exerted by the international community to assess the impact of the Kuwait oil slick, an integrated programme was planned and sponsored by the Regional Organization for the Protection of Marine Environment (ROPME), the Intergovernmental Oceanographic Commission (IOC), the United Nations Environmental Programme (UNEP), and the U.S. National Oceanic and Atmospheric Administration (NOAA). The programme was partially achieved through a 100-day cruise in the region from February to June 1992 aboard the NOAA research vessel “Mt. Mitchell”. During this cruise, the Arabian Gulf was extensively surveyed and a large number of samples was collected for more than 100 offshore sampling stations. Two years later an integrated project plan was formulated by ROPME and IOC to study the long-term impact of the oil slick on the Gulf marine environment. As part of this plan, arrangements were made for a group of scientists to cruise the region aboard the Japanese research vessel “Umitake Maru” between 15 and 26 December 1993. The main objective of the Japanese cruise, however, was to study the effect of the oil slick on marine biota. Therefore, a limited number of sediment core samples was collected during the cruise from only 20 sampling stations selected for such biological studies (Al-Ghadban et al. 1996). Massoud et al. (1986) and Al-Abdali et al. (1996) carried out a series of sedimentological and geochemical studies on 112 sediment core samples (≈ 15 cm deep) collected from the Arabian Gulf during the 1992 Mt. Mitchell cruise to investigate the petroleum hydrocarbon and trace metal pollutants transferred from the Kuwait oil slick to the sea bed and residing in these sediments. Also, measurements taken for total organic carbon (TOC), total petroleum hydrocarbons (TPH), and selected trace metals in sediment samples collected during the 1993 Umitaka Maru cruise were also compared with those made on samples collected from the same offshore sampling stations during the 1992 Mt. Mitchell cruise to throw light on the status of oil pollution in the Arabian Gulf and the fate and effect of the Kuwait oil slick three years after the oil was spilled. None of the previous studies provided detailed information about the nature and importance of sedimentation rate and bioturbation in the Arabian Gulf. Both environmental factors have certain implications in any data interpretation that concerns the fate of pollutants in any marine environment.

Seasonal Variation of the Suspended Solid Matter, off the Coast of North Yorkshire

An investigation into the natural regime of coastal suspended solids before discharge of potash mining waste is described. Regular samples of suspended material were taken over the period September 1968 to August 1970. Statistical analyses showed significant differences in suspended solid values between the months and between inshore and offshore sampling stations. There was no significant difference between sampling points along the coast. The inshore suspended solid values were low from May to September. At other months and at the offshore stations there was a gradual change from summer (low) to winter (high) values and vice versa.Sea temperature, sea state, tidal range and river flow correlated significantly with suspended solid values. It is suggested that wave action, tidal currents and river flow control most of the variation in load of suspended matter off the N. Yorkshire coast. The significant negative correlation between temperature and suspended solid values is not regarded as a causal relationship. Low temperatures are associated with high wave activity and high river flow rates; factors which are more likely to have a causal relationship with suspended solid loads than temperature. Thus, suspended matter variations off the Yorkshire coast are probably determined by physical rather than biological temperature-dependent processes.From multiple linear regression analyses, sea state, tidal range and river flow were found to account for 64·1% of the variation of the inshore suspended solid values and 52·4% of the variation of offshore values. Using the multiple regression equations as mathematical models it was possible to derive accurate predictions of the natural suspended solid load.