Low Suspended Particulate Matter Concentrations Research Articles

Incidence of harmful algal blooms in pristine subtropical ocean: a satellite remote sensing approach (Jeju Island)

Despite the increasing numbers of red tide events in the pristine subtropical ocean, a paucity of previous observations has limited understanding of harmful algae in the seas around the Korean Peninsula. Therefore, using six years (2012–2017) of Geostationary Ocean Color Imager (GOCI) satellite data, we characterized the red tides around Jeju Island, a volcanic island located near the paths of the Jeju Warm Current and Tsushima Warm Current, using the Normalized Red Tide Index (NRTI) method. The seawater around Jeju Island has for a long time been considered to be very clear, with relatively low suspended particulate matter concentrations and few harmful algae. Nonetheless, the satellite-based NRTI detection method used in this study detected and supported the existence of red tides in the coastal region around Jeju Island. Analysis of the red tide distribution showed that red tide first began to appear near the western coast of Jeju Island, then developed in the northern and eastern coastal regions, and finally vanished in the eastern coastal region. The monthly averages of the NRTI demonstrated a bloom event from April to May in every year. Additional fall blooms were detected in August–September, particularly in 2013 and 2016. The NRTI revealed strong interannual variations. The longest blooms occurred in 2015, and the most comprehensive and strongest event occurred in the spring of 2016. The latter three years (2015–2017) had much higher NRTI than the former three years (2012–2014). The probability of red tide occurrence at a given point during the 6-year study period revealed spatial differences. Relatively high probability of 0.3–0.5 was determined along the northern coastal region, whereas low probability of less than 0.2 was found along the southern region. Ground truth data also showed more frequent observations and higher red tide cell densities along the northern coast. Changes in NRTI in spring are positively correlated with changes in ENSO indices in winter. This study is the first to use a satellite-based approach with a vast long-term satellite database to elucidate the existence and probability of red tides near Jeju Island. We anticipate that this study will provide a useful strategy for remote monitoring of harmful algal blooms over wide regions using optical data.

Dominance of Autochthonous Phytoplankton-Derived Particulate Organic Matter in a Low-Turbidity Temperate Estuarine Embayment, Gwangyang Bay, Korea

In estuaries, the sources of organic matter, its composition, and its functional role in the coastal ecosystem food web are all influenced by dominant estuarine processes. We investigated seasonal variations in the quantity and composition of dissolved inorganic nutrients, suspended particulate matter (SPM), and phytoplankton across a low-turbidity estuarine–coastal continuum in Gwangyang Bay, South Korea. The narrow estuarine channel has a sharp salinity gradient (from 0 to around 30) and low SPM concentrations (<20 mg L−1). The channel carries river discharge, with a large quantity of nutrients (NO3 and SiO2), into the bay. The especially low SPM concentrations in the estuary (range: 2.0–29.1 mg L−1), and generous nutrient source, create an exceptionally low-turbidity condition in the water column and high primary productivity with no conspicuous spatial or seasonal trends. Gradually increasing 13C values, low POC:Chla (<200), and low molar C:N (4–8) in the SPM, together with higher Chla concentrations at low SPM locations along the longitudinal transect, suggest that local production of phytoplankton has a strong influence on the distributional patterns of particulate organic matter. Short water-residence times, within the bay system, impede the accumulation of diverse-origin organic matter. The community composition of phytoplankton, distinguished by their size group, also plays a role in characterizing SPM quantity and composition. The results indicate that autochthonous pelagic production governs biogeochemical features in the low-turbidity estuarine embayment, contrasting with a prevalence of allochthonous organic matter, and its active processing, in highly turbid and/or longer residence-time systems.

Decay rates of faecal indicator bacteria from sewage and ovine faeces in brackish and freshwater microcosms with contrasting suspended particulate matter concentrations

To safeguard human health, legislative measures require the monitoring of faecal indicator bacteria (FIB) concentrations in recreational and shellfish waters. Consequently, numerous studies have focussed on FIB survival in the water column and more recently in estuarine sediments. However, there is a paucity of information regarding the influence of contrasting suspended particulate matter (SPM) concentrations on the survival of FIB in the water column of estuaries. Here, microcosms containing freshwater or brackish water with low, high and extreme SPM concentrations were inoculated with sewage and ovine faeces and the decay rate of Escherichia coli, coliforms and enterococci were determined by enumeration over five consecutive days. E. coli derived from ovine faeces proliferated and persisted at high levels in both freshwater and brackish microcosms (no decay), whereas ovine enterococci demonstrated a net decay over the duration of the experiment. Furthermore, SPM concentration had a significant effect on the decay rates of both E. coli and enterococci from ovine faeces in brackish microcosms, but decay rate was greater at low SPM concentrations for E. coli, whereas the opposite was observed for enterococci, whose decay rates increased as SPM concentration increased. E. coli, enterococci and coliforms derived from wastewater demonstrated a net decay in both freshwater and brackish microcosms, with contrasting effects of SPM concentration on decay rate. In addition, some FIB groups demonstrated contrasting responses (decay or proliferation) in the first 24h following inoculation into freshwater versus brackish microcosms. Overall, SPM concentrations influenced the proliferation and decay rates of FIB in brackish waters, but had minimal influence in freshwater. These results demonstrate that the survival rates of FIB in aquatic environments are system specific, species and source dependent, and influenced by SPM concentration. This study has important implications for catchment-based risk assessments and source apportionment of FIB pollution in aquatic environments.

Assessment of heavy metal content in suspended particulate matter of coastal industrial town, Mithapur, Gujarat, India

Heavy metal concentrations in suspended particulate matter (SPM) were investigated for their distribution and source in the atmosphere of coastal industrial town, Mithapur, Gujarat, India. SPM, at 10 locations covering three seasons, were trapped on glass fibre filters using high volume samplers and quantification of metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) was done using Atomic Absorption Spectrometry employing HNO 3 based wet digestion. Results show relatively low concentrations of SPM (211.3 to 375.2 μg/m 3) compared to National Ambient Air Quality Standard (NAAQS), specified By Central Pollution Control Board (CPCB, India), however, they were 2–3 times higher as compared to reference site. Among the heavy metals Cr, Mn and Pb levels were low, while Ni and Cd found to be exceeding the USEPA standards. The metal levels were also compared with those reported for other rural, coastal, industrial and urban parts around the world. Enrichment Factor analysis indicated that Cd, Zn, Cu, Pb and Ni were highly enriched relative to their crustal ratios (to Fe) and correspond to substantial contribution of anthropogenic source of these metals. The source identification was carried out by principal component analysis by applying a Varimax Rotated Component Matrix.

Wind-driven estuarine turbidity maxima in Mandovi Estuary, central west coast of India

Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate that the average concentrations of SPM at the regular station are ∼20mg/l, 5mg/l, 19mg/l and 5mg/l for June–September, October–January, February–April and May, respectively. SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June–September is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1–5.6ms−1) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring in February–April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2–3.7ms−1) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition

Mercury distribution in Douro estuary (Portugal)

Determinations of dissolved reactive and total dissolved mercury, particulate and sedimentary mercury, dissolved organic carbon (DOC), particulate organic carbon (POC) and suspended particulate matter (SPM) have been made in the estuary of river Douro, in northern Portugal. The estuary was stratified by salinity along most of its length, it had low concentrations of SPM, typically <20 mg dm −3, and concentrations of DOC in the range <1.0–1.8 mg dm −3. The surface waters had a maximum dissolved concentration of reactive mercury of about 10 ng dm −3, whereas for the more saline bottom waters it was about 65 ng dm −3. The surface waters had maximum concentrations of total suspended particulate mercury of ∼7 μg g −1 and the bottom waters were always <1 μg g −1. Concentrations of mercury in sediments was low and in the range from 0.06 to 0.18 μg g −1. The transport of mercury in surface waters was mainly associated with organic-rich particulate matter, while in bottom waters the dissolved phase transport of mercury is more important. Lower particulate organic matter, formation of chlorocomplexes in more saline waters and eventually the presence of colloids appear to explain the difference of mercury partitioning in Douro estuarine waters.

Trace metal behaviour in the Conwy estuary, North Wales

The distribution of trace metals Zn, Ni, Mn, Fe, Cu, Pb, Cd and Cr between suspended particulate matter (SPM) and water in the Conwy estuary, North Wales, has been studied in three surveys in 1998. Dissolved Cu and Mn showed some monthly variations. Most of the dissolved trace metals displayed a negative association with salinity, indicating rivers as a major source of inputs for them. Particulate Zn, Mn and Fe showed a decreasing concentration seaward, whilst the levels of Ni, Cu, Cr and Pb increased with salinity. SPM concentration was the most important variable significantly related to trace metal concentrations in SPM, with an inverse relationship between the two parameters. This was explained by the relative enrichment of trace metals in fine particles at low SPM concentrations and relative depletion of trace metals in coarse particles at high SPM concentrations. Particulate Zn, Mn and Pb were dominated by the fraction available to acetic acid (non-detrital), whilst particulate Ni, Fe and Cr were dominated by the fraction available to nitric acid (detrital). The partition coefficient of trace metals between SPM and water declined with increasing SPM concentration, consistent with the so-called “particle concentration effect”. Such a phenomenon may be explained by the presence of fine particles (including colloids) enriched with trace metals at low SPM concentrations, and the salinity-induced desorption.

섬진강 하구역에서 염분경사에 따른 입자성 유기물질의 분포

1999년 3월부터 2001년 4월까지 섬진강하구역에서 염분경사에 따른 부유입자물질 (SPM), 엽록소 <TEX>$\alpha$</TEX>, 입자유기 탄소 (POC)와 질소 (PON) 그리고 입자유기규소 (PBSi)의 분포를 조사하였다. 조사 정점은 지리적 위치보다는 각 조사시마다 표층염분을 현장에서 측정하여 결정하였다. 섬진강으로부터 다량의 육수가 유입됨에도 불구하고 대부분의 조사시기에서 SPM의 농도는 20mg/L 이하로 낮아 섬진강을 통해 유입되는 육상기원의 SPM 공급은 낮은 것으로 판단된다. 1999년 11월의 5<TEX>$\~$</TEX>15psu (난초도로부터 10<TEX>$\~$</TEX>20km), 2000년 4월의 15<TEX>$\~$</TEX>25psu (10<TEX>$\~$</TEX>20km), 그리고 2000년 10월의 약1<TEX>$\~$</TEX>15psu (15<TEX>$\~$</TEX>20km) 염분구간에서는 엽록소 a농도가 약 8<TEX>$\~$</TEX><TEX>58$\mu$</TEX>g/L로 매우 높았으며 POC, PON 및 PBSi의 농도도 매우 높았다. POM의 농도가 매우 높았던 염분역을 포함한 중간염분역에서의 POC와 엽록소 <TEX>$\alpha$</TEX> 비가 비교적 낮아 POC의 대부분이 식물플랑크톤으로 구성되어 있음을 보여주고 있다. 반면, 초저염분역과 하구 입구에서는 POC와 엽록소 <TEX>$\alpha$</TEX> 비가 상대적으로 높아 담수 및 저층으로부터의 detrital POC 공급이 있었음을 의미한다. 따라서 섬진강 하구수역에서의 비교적 낮은 SPM 농도와 중간염분역에서의 높은 엽록소 <TEX>$\alpha$</TEX> 농도 및 낮은 POC와 엽록소 <TEX>$\alpha$</TEX> 비는 식물플랑크톤 생산이 염분에 따른 POM의 분포를 조절하는 가장 중요한 요인임을 시사해 준다. The distributions of suspended particulate matter (SPM), chlorophyll a, particulate organic carbon (POC) and nitrogen (PON) and particulate biogenic silica (PBSi) along the salinity gradient were investigated in the Seomjin River estuary from March 1999 to April 2001. Sampling sites were set based on the surface salinity during each cruise rather than geographic locations. Concentrations of SPM were less than 20 mg/L, suggesting relatively low input of terrestrial SPM despite large freshwater discharge through Seomiin River, Chlorophyll a peaks occurred at 5<TEX>$\~$</TEX> 15 psu salinity zone (10<TEX>$\~$</TEX>20 km from Nan Cho Island) in November 1999, at 15<TEX>$\~$</TEX>25 psu (10<TEX>$\~$</TEX>20 km) salinity zone in April 2000 and at 1<TEX>$\~$</TEX>15 psu salinity zone (15<TEX>$\~$</TEX>20 km) in October 2000 (ca. 8<TEX>$\~$</TEX>58<TEX>%\mu$</TEX>g/L). Concentrations of POC, PON and PBSi were also high at the same zone. Relatively low ratios of POC to chlorophyll a in mid-salinity zone where POM peak occurred suggests high contribution of living phytoplankton to the total POC. On the other hand, relatively high ratios of POC to chlorophyll <TEX>$\alpha$</TEX> in very low salinity zone and the mouth of estuary indicated relatively high portions of detrital POC. Consequently, the low concentrations of SPM in this estuary and the high concentrations of chlorophyll <TEX>$\alpha$</TEX> and the low ratios of POC to chlorophyll <TEX>$\alpha$</TEX> in the mid-salinity zone suggest that production of living phytoplankton is primary factor in controlling distribution of POM along the salinity gradients in the Seomjin River estuary.

Observations on Suspended Particulate Matter (SPM) and Microalgae in the Dollard Estuary, The Netherlands: Importance of Late Winter Ice Cover of the Intertidal Flats

Three years of combined physical and biological measurements in the Dollard tidal basin showed that in the early spring of 1996, suspended particulate matter (SPM) concentrations were low compared to observations in spring 1995 and 1997. Since in 1996 the duration of ice formation on the tidal flats in winter was much longer than in 1995 or 1997 (until late February), it is proposed that ice cover reduced resuspension of bed material by enhancing consolidation of the sediment and thus increasing the critical shear stress for erosion (τcrit), and also by preventing the occurrence of high waves. Both phenomena led to low suspended particulate matter (SPM) concentrations. After the ice cover vanished, the clear water phase was followed by a microalgal bloom both in the water column and on the sediment. During the algal bloom, SPM concentrations remained low. Floc size measurements indicated that low SPM concentrations during the benthic and pelagic algal blooms were not caused by increased flocculation. On the sediment bed however benthic microalgae produced large amounts of extracellular carbohydrates, which led to an increase in bed strength (τcrit) and a reduction of resuspension, and thus kept SPM concentrations low during the algal bloom.

Distribution of particulate and reactive mercury in surface waters of Swedish forest lakes — an empirically based predictive model

The partition coefficient ( K d) expresses the ratio between particulate bound and dissolved metals. In lake dynamic modelling, it is used to distribute the total load between the dissolved and particulate routes of lake transport. An empirically based model for prediction and evaluation of a modified partition coefficient for mercury (Hg) in lake water has been developed using field data from 25 Swedish lakes. As a substitute for dissolved Hg determined by filtration, this study uses the easy reducible (or reactive) proportion of Hg in water samples and the modified partition coefficient is here denoted K d *. The model relates K d * for Hg to the best correlating of several lake specific environmental variables, resulting in an r 2-value of 0.69. K d * was found to decrease with increasing suspended particulate matter (SPM) concentration, iron concentration (Fe) and ratio of lake to drainage area ( a/ADA). Interpretations of the model parameters were discussed in light of the clusters of statistically and functionally related variables they represent. The negative correlation between K d * and SPM is possibly due to the particle concentration effect, which seems to be valid also for the definition used here for the partition coefficient. For K d the particle concentration effect is often explained by an exponential relationship between colloids and SPM which results in relatively more colloid bound metals at low SPM concentrations. The fraction of colloid bound metals is counted with the ‘dissolved’ fraction which decreases the K d. Influences of spurious correlations on the relationship between K d * and SPM have been assessed and found to contribute to the statistical correlation. The negative correlation with iron can also be accounted for by Hg association with small particles (iron/manganese oxides and hydroxides, possibly in association with humic matter). The influence of the morphometric factor a/ADA is probably due to differences in K d * with different Hg transport paths (direct deposition on the lake surface is believed to decrease K d *). The model was tested using stability tests, which indicated that other related variables could replace the given model parameters. The model parameter interpretations, in terms of clusters of related variables would, however, have been similar.

Monitoring suspended particulate matter fluxes and patterns with the AVHRR/NOAA-11 satellite: application to the Bay of Biscay

AVHRR/NOAA-11 satellite images of the C1 (580–680 nm) and C2 (725–1100 nm) channels were used to quantify the suspended particulate matter discharged into the ocean by the Gironde estuary (France). The calibration method is based on a comparison between satellite values (AVHRR reflectances) and suspended particulate matter (SPM) concentrations at the sea surface, measured in situ. To correct the aerosol variations a C1-C2 image subtraction is applied. However, when the SPM concentration is greater than about 15 mg l −1, the C2 channel image is affected by water turbidity and the C1-C2 correction cannot be used. The C1 channel is more sensitive, and we were able to distinguish SPM concentration variations greater than 0.5 mg l −1. A subtraction of two images recorded with a 24 h interval was carried out to evaluate vertical and horizontal fluxes. The residual image shows the quantity of particles leaving the surface layer. To assess horizontal displacements, turbid fronts were mapped by means of an image gradient analysis. Major and minor fronts recorded each day, superimposed to outline displacements (gradients and orientations), were displaced from the Gironde estuary to the West and the Northwest. During the ECOFER cruises (1989–1991), several AVHRR scenes were processed using an atmospheric correction based on the low SPM concentrations (“ocean pixel subtraction”). Generally, surface particulate matter is confined to the inner continental shelf. Higher values were observed during the ECOFER 4 cruise. Suspended particulate matter concentrations with the maximum extension appeared during the ECOFER 1 cruise. Concentrations were very low during the ECOFER 5 cruise, even in the lower estuary. This was due to low summer discharges that occurred during the dry period of 1988–1991 in France. During these surveys, estimated SPM concentrations were less than 1.5 mg l −1 in the ECOFER area.

Seasonality in nutrient concentrations in Galveston Bay

In order to investigate factors controlling nutrient cycling in the shallow and turbid coastal ecosystem of Galveston Bay, data from: (1) the Texas Water Commission (TWC) database 1980–1989, and (2) salinity transects in 1989 and 1993 are presented and analyzed. Statistical regression and time-series analysis were carried out on data acquired by TWC between 1980 and 1989, in an attempt to establish seasonally of nutrient and chlorophyll-a (chl.-a.) concentrations in the bay and to determine factors which regulate these concentrations. A strong seasonality was found for phosphorus and chl.-a. in the upper and mid-bay stations. A recurring maximum for phosphate occurred in September and a chl.-a. maximum occurred regularly in March–April. It is hypothesized that benthic regeneration of phosphorus at the end of summer is responsible for the phosphate maximum. The inverse correlation of the partition coefficient ( K d ) for phosphate with the concentration of suspended particulate matter (SPM), coupled to a strong enrichment of phosphate in suspended particles at low SPM concentrations, indicates additional control by geochemical and physical processes such as particle sorting and/or particle-colloid interactions. Nitrate is inversely correlated with salinity at the upper and mid-bay stations, indicating the Trinity River is a major source. Nutrient concentrations in the lower bay (East and West Bay stations) are considerably lower and less predictable, as they are not correlated with salinity or temperature. Data from the 1989 and 1993 transects confirm the yearly maximum in phosphate concentration in late summer months, with peak concentrations in the upper Trinity Bay. It is concluded that despite possible phosphate buffering by physical and geochemical mechanisms, relatively large concentration maxima recur regularly every year during the summer, possibly caused by a benthic source of phosphate.

Seasonal and spatial variability of particulate matter of a muddy intertidal flood front

ABSTRACTThe concentration and composition of suspended particulate matter (SPM) were measured weekly for a period of one year in the flood front waters traversing a muddy tidal flat. SPM concentrations were lowest in the winter when portions of the tidal flat were covered with ice, and biological activity was minimal. In contrast, the summer months had the highest SPM concentrations which reflected increased bottom resuspension.The two main sources of SPM were suspended matter carried in from offshore on the flooding tide and resuspended in situ bottom sediments. The offshore source was characterized by low SPM concentrations, coarse textures, and a high content of protein and chlorophyll ‘a’. Samples taken during resuspension events (storms/showers) had high SPM concentrations, finer textures, and were enriched in dead detrital organic material (phaeophytin). At any one time the SPM was primarily an admixture of these two sources.The highest SPM measurements were taken during storm events, with rainfall seeming to play a dominant physical role in aiding resuspension. SPM concentrations, textures, and compositions collected during the storms closely approximated SPM measurements made over newly dug ‘clam flats’.