Inorganic Suspended Matter Research Articles

Impact of phytoplankton, CDOM, and suspended sediments on the vertical attenuation of light, changing heat content and circulation on a continental shelf: A modelling study of the Great Barrier Reef

Solar radiation propagating through the water column is scattered and absorbed by optically active constituents in the ocean, in particular phytoplankton, coloured-dissolved organic matter (CDOM), suspended inorganic particulate matter (SPIM) and detritus. These wavelength-dependent processes affect the vertical distribution of heating in the water column and its stratification. The continental shelf north-east of Australia, containing the Great Barrier Reef (GBR), is characterised by highly seasonal and intermittent freshwater inputs leading to large sediment and nutrient discharges that strongly impact the water optical properties. While this complex mixture of optically active constituents is known to affect water clarity and the euphotic zone depth in the river plumes, its impact on the ocean circulation and thermal balance is still unclear at the scale of the GBR. In this study, we use a hydrodynamic-optical-biogeochemical ocean model to investigate the feedback between heat absorption by phytoplankton, CDOM and suspended sediments and ocean dynamics in the GBR region. The results show that the attenuation of the vertical heat flux due to phytoplankton, CDOM and SPIM concentrations is stronger on the continental shelf and dominated by the absorption and scattering from suspended sediments. The presence of absorbing constituents in the water column drives a temperature increase at the surface and a decrease below the mixed layer with stronger stratification and greater heat losses to the atmosphere. Inshore, the ocean heat content increases by up to 1% due to optically active constituents. Offshore, absorption by optically active constituents near the surface is compensated by less absorption underneath the mixed layer resulting in a decrease in the ocean heat content of the top 500 m. We find that considering a spatially- and temporally-variable vertical attenuation of heat due to multiple optically-active components improves hydrodynamic model skill. This study highlights the importance of the impact of water clarity and its spatial variability on hydrodynamic processes.

Estimates of carbon sequestration potential in an expanding Arctic fjord (Hornsund, Svalbard) affected by dark plumes of glacial meltwater

Abstract. In polar regions, glaciers are retreating onto land, gradually widening ice-free coastal waters, which are known to act as new sinks of atmospheric carbon. However, the increasing delivery of inorganic suspended particulate matter (iSPM) with meltwater might significantly impact their capacity to contribute to carbon sequestration. Here, we present an analysis of satellite, meteorological, and SPM data as well as results of a coupled physical–biogeochemical model (1D GOTM-ECOSMO-E2E-Polar) with a newly implemented iSPM group to show the impact of iSPM on the ecosystem dynamics in a warming polar fjord (Hornsund, European Arctic) with numerous shallow-grounded marine-terminating glaciers. Our results indicate that with a longer melt season (9 d per decade, 1979–2022), the loss of sea ice cover (44 d per decade, 1982–2021) and the formation of new marine habitats after the retreat of marine-terminating glaciers (around 100 km2 in 1976–2022, a 38 % increase in the total area), glacial meltwater has transported increasing loads of iSPM from land (3.7 g m−3 per decade, reconstructed for 1979–2022). The simulated light limitation induced by the iSPM input delayed and decreased the peaks in phytoplankton, zooplankton, and macrobenthos. The newly ice-free areas still markedly contributed to plankton primary and secondary production and carbon burial in sediments (5.1, 2.0, and 0.9 Gg C yr−1, respectively, on average for 2005–2009 in the iSPM scenario). However, these values would have been 5.0, 2.1, and 0.1 Gg C yr−1 higher, respectively, without the iSPM input. Since carbon burial was the least affected by iSPM (a decrease of around 16 %, in comparison to 50 % for plankton primary and secondary production), the impact of marine ice loss and enhanced land–ocean connectivity should be investigated further in the context of carbon fluxes in expanding polar fjords.

Tracing sources of inorganic suspended particulate matter in the Great Barrier Reef lagoon, Australia

Water clarity on the inshore Great Barrier Reef (GBR) is greatly influenced by terrestrial runoff of suspended particulate matter (SPM). Catchment sediment tracing studies often do not extend into the marine environment, preventing the analysis of preferential marine transport. This study employs novel collection and sediment tracing techniques to examine the transport of the terrigenous ‘mineral’ component of plume SPM within the GBR lagoon for two flood events. Utilising geochemical, radionuclide and clay mineral analysis, we trace terrigenous mineral sediments > 100 km from the river mouth. We show that the SPM geochemistry is highly influenced by particle-size fractionation, desorption, and dilution within the plume, rendering traditional tracing methods unviable. However, the ratios of rare earth elements (REE) to thorium (Th) provide stable tracers of mineral SPM transported across the catchment to marine continuum and allow the identification of discrete catchment sources for each flood event. Plume sediment radionuclides are also stable and consistent with sub-surface erosion sources.

Particle Size Distribution Slope Changes along the Yellow River Delta Observed from Sentinel 3A/B OLCI Images

Quantitative estimates of particle size in estuaries and shelf areas are important to understand ocean ecology and biogeochemistry. Particle size can be characterized qualitatively from satellite observations of ocean color. As a typical marginal sea, the Yellow River Delta (YRD) with the Bohai Sea experiences a complex hydrodynamic environment. Here, we attempt to quantify the particle size distribution (PSD) slope (ξ) based on its relationship with the particle backscattering exponent from Sentinel-3A/B OLCI. The PSD slope, ξ displays temporal and spatial variability in the YRD with the Bohai Sea. Its value varies between 3 and 4, and typically exceeds 5 in offshore areas. The lowest value of ξ occurs in the winter, indicating the presence of fine inorganic particles in the water, while high values are attained in the spring, when phytoplankton blooms increase the particle size. ξ decreases near the river mouth because of the large sediment-laden discharge debouching into the sea. We detected a slight increase in ξ when turbid waters were present in the period 2016–2022. Environmental factors, such as sea surface temperature, sea surface wave height, and wind, may control particle size and ξ in the long term. Inorganic suspended particle matter is derived along the YRD using the magnitude of ξ. The mean inorganic suspended particle matter area in winter approaches 23,900 km2 when ξ < 4.6. This study thoroughly characterizes variations in ξ in the YRD with the Bohai Sea and clarifies the contributions of driving factors from human activities and climate change.

Influence of land-terminating glacier on primary production in the high Arctic fjord (Blagopoluchiya Bay, Novaya Zemlya archipelago, Kara Sea)

Glaciers retreat linked with rapid Arctic warming changes bioproductivity in the bays and coastal areas of the Arctic Ocean (AO). The impact of different types of glaciers shrinking on water column primary production (IPP) is widely discussed. This work studied the influence of the land-terminating glacier on IPP and chlorophyll a concentration (Chlph) in Blagopoluchiya Bay (Novaya Zemlya archipelago). It is known that meltwater runoff from land-terminating glaciers enriches coastal waters with inorganic suspended matter and nutrients. The aim of the present study was to establish the main environmental factor determining IPP in the bay influenced by the glacier. During summer and autumn, IPP in the bay was low. The medians of IPP were 69 and 26 mgC m−2 day−1, respectively, which was 1.7- and 1.9-fold lower than in open waters of the Kara Sea in the vicinity of the bay. Generally, IPP increased from the inner part, close to the glacier, to the outer part of the bay. In summer, IPP and Chlph depend on both nutrient concentrations in the photosynthetic layer and the parameters of water transparency. On the contrary, in autumn, IPP and Chlph depend only on the optical properties of the subsurface layer. It can be concluded that low IPP in Blagopoluchiya Bay is determined mainly by unfavorable conditions of underwater PAR formed by meltwater discharge from the glacier. Thus, the fast melting of the land-terminating glaciers linked with climate warming can lead to a decrease in the biological productivity of the AO bays.

Multi-Parameter Algorithms of Remote Sensing Reflectance, Absorption and Backscattering for Coastal Waters of the Southern Baltic Sea Applied to Pomeranian Lakes

The Pomeranian lakes in Northern Poland and the nearby coastal waters of the Baltic Sea belong to optically complex water bodies characterised by high eutrophication levels. These water types require a local approach when developing bio-optical algorithms that combine the inherent and the apparent properties of seawater. Well-established local algorithms are of great value for understanding and addressing rapid changes in water quality related mostly to human activities in coastal and near-shore zones, as well as in optically similar lakes. Our research analyses the possibility of using the multi-parameter algorithms of absorption a(λ), backscattering bb(λ) and remote sensing reflectance Rrs(λ), originally developed for the coastal waters of the Southern Baltic Sea, for three selected Pomeranian lakes. Our multi-parameter algorithms are based on the input concentrations of the biogeochemical components measured in the lake waters, i.e., chlorophyll a (Chl a), suspended particulate matter (SPM), inorganic suspended particulate matter (SPMinorg), the sum of the surface concentrations of accessory pigments (ΣC) and coloured dissolved organic matter with a wavelength of 400 nm (aCDOM(400)). Rrs(λ) and a(λ) output values were compared with independent measurements of these parameters conducted in the lake waters at 20 sampling stations. Our algorithm output values of bb(λ) were compared to the values obtained based on the algorithm provided by Ficek, previously developed and validated for Pomeranian lakes, at the same stations. The statistical analyses conducted afterwards showed that the multi-parameter algorithms of Rrs(λ) and a(λ) for the Southern Baltic Sea are sufficient to be used for the stations investigated in the aforementioned three lakes. Specifically, the correlations between the bb(λ) values obtained based on the Ficek algorithm and the bb(λ) values obtained using our multi-parameter algorithm reveal a statistical error rate of less than 20%.

A novel framework for turbidity source apportionment of the urban lakeside river network

Turbidity source apportionment is essential but complex for precise environmental rehabilitation of worldwide urban lakeside river networks impaired by turbidity. A new turbidity source analysis framework including in-situ sampling, vessel monitoring, remote sensing, and hydrodynamic modelling was proposed, where the critical processes of flow reversal from the turbid lake, navigation, and urban non-point source in urban lakeside river networks were explicitly considered. The case study results showed that the turbidity problem (mean value was 211.3 nephelometricturbidityunits (NTU)) was primarily led by suspended inorganic matter (58%), followed by suspended organic matter (19%) and other matter. The Tiaoxi River and busy shipping contributed most to the annual total suspended solids load of the target river, with the same percentage of 34%. The turbid Lake Taihu provided 64,663 tonnes and 31% of the total suspended solids load, focusing on the autumn and winter months. Tiaoxi River load was highly concentrated on the storm events, which accounted for 71.4% of the annual Tiaoxi River source (209846 tonnes). The large water volume of reverse flow and the high TSS concentration of Lake Taihu in the autumn and winter months accounted for the seasonal change in Lake Taihu’s TSS load. The coronavirus disease lockdown reduced the mean monthly total suspended solids concentration of 152.4 mg/L in November and December 2019 to 49.2 mg/L in January and February 2020, by limiting the waterway transportation and the market demand for building materials. The river estuary’s vegetation interception belt, shipping restriction and rerouting, and integrated catchment management were advised to mitigate the urban river network turbidity.

A classification-based approach to mapping particulate organic matter (POM) in inland water using OLCI images.

Particulate organic matter (POM) plays a major role in freshwater ecosystems by serving as a bridge for the conversion of various nutrients. The composition and sources of POM in inland lakes are complex, making it difficult to estimate its concentration accurately via remote sensing. Therefore, a classification-based method based on the sources and composition of POM is proposed for estimating POM concentrations in inland lakes. In this study, 379 samples were collected from ten lakes in the Yangtze River Delta (YRD) at different times. A water-type classification method based on OLCI [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] was developed for POM estimation based on biological and optical characteristics. Water type 1 is relatively clear, and POM may originate from aquatic vegetation or sediment. Water type 2 was dominated by inorganic suspended matter, and POM mainly originated from the attachment and entrainment of inorganic minerals. Water type 3 is an algae-dominated water body, and POM is mainly derived from fresh algal particles and the microbial degradation of phytoplankton. Therefore, specific POM estimation algorithms were developed for each water type. OLCI [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] were used for water type 1; [Formula: see text], [Formula: see text], and [Formula: see text] were adopted for water type 2; and [Formula: see text], [Formula: see text], and [Formula: see text] were selected for water type 3. Using an independent dataset to evaluate the estimation accuracy of the developed algorithm, the results show that the estimation performance of this algorithm is significantly improved compared to the two other algorithms used; the mean absolute percentage errors (MAPE) decreased from 72.56% and 52.21% to 32.61%, and the root mean square errors (RMSE) decreased from 3.05mg/L and 2.24mg/L to 1.75mg/L. A random error analysis of the atmospheric correction demonstrated that this algorithm is robust and can still perform well within a random error of 30%. Finally, this method was successfully applied to map the POM concentrations in the YRD using OLCI images acquired on November 12, 2020.

Satellite assessment of coastal plume variability and its relation to environmental variables in the Sofala Bank

Monthly composites of remote sensing reflectance at 555 nm wavelength (Rrs555) from ocean color imagery of the MODIS sensor onboard the Aqua platform were used to characterize the spatial and temporal variability of coastal plume in the Sofala Bank and its relation to river discharge, local rainfall, and wind speed. To achieve the objective, maps of monthly composites of Rrs555 over the Sofala Bank were inspected and statistical analysis was performed, including correlation, analysis of variance, and wavelet coherence between environmental variables and both plume area and Rrs555. Climatology of Rrs555 revealed that both plume dispersion and Rrs555 values are higher during June to December and lower during January to May. A positive correlation (r = 0.77) between wind speed and monthly time series of Rrs555, and a negative correlation between the Zambezi river discharge (r = −0.21) and rainfall (r = −0.67) with Rrs555 were found. These results suggest that variation of suspended matter in the Sofala Bank is mainly controlled by erosion and re-suspension by winds rather than the input of terrigenous matter by the Zambezi River discharge and rainfall, assuming that Rrs555 can be a valid proxy for the inorganic suspended matter. The southern portion of the Sofala Bank (i.e., near the mouths of the Pungue and Buzi Rivers) presented higher values of Rrs555 if compared to the center region near Zambezi river mouth and the northern region near Licungo river mouth. The higher Rrs555 values in the southern region might be associated with higher re-suspension rates due to increased tide mixing, dredging activities, and the shallower nature of bathymetry in the southern region. The dominance of wind in controlling the variability of suspended sediments and the eventual relatively greater contribution of Pungue and Buzi River than the Zambezi in supplying sediments could represent an evidence of weakening of Zambezi River supply of sediments, a process that might have started after damming the Zambezi Catchment.

Inherent optical properties of dissolved and particulate matter in an Arctic fjord (Storfjorden, Svalbard) in early summer

Abstract. There have been considerable efforts to understand the hydrography of Storfjorden (Svalbard). A recurring winter polynya with large sea ice production makes it an important region of dense water formation at the scale of the Arctic Ocean. In addition, this fjord is seasonally influenced by freshwater inputs from sea ice melt and the surrounding islands of the Svalbard archipelago, which impacts the hydrography. However, the understanding of factors controlling the optical properties of the waters in Storfjorden are lacking and are crucial for the development of more accurate regional bio-optical models. Here, we present results from the first detailed optical field survey of Storfjorden conducted in early summer of 2020. Our observations are based on spectrometric analysis of water samples and in situ vertical profiles with an absorption and attenuation meter, a fluorometer, and a conductivity, temperature, and depth (CTD) sensor. In addition to the expected seasonal contribution from phytoplankton, we find that in early summer waters in Storfjorden are optically complex with a significant contribution from coloured dissolved organic matter (CDOM, 33 %–64 % of the non-water absorption at 443 nm) despite relatively low CDOM concentrations and in the nearshore or near the seabed from non-algal particles (up to 61 % of the non-water absorption at 550 nm). In surface waters, the spatial variability of light attenuation was mainly controlled by inorganic suspended matter originating from river runoff. A distinct subsurface maximum of light attenuation was largely driven by a subsurface phytoplankton bloom, controlled by stratification resulting from sea ice melt. Lastly, the cold dense bottom waters of Storfjorden from winter sea ice production periodically overflows the sill at the mouth of the fjord and can thus reach the Fram Strait. It contained elevated levels of both non-algal particles and dissolved organic matter, which are likely caused by the dense flows of the nepheloid layer interacting with the sea bed.

Optical characteristics and factors that influence representative Lakes in the Taihu Lake basin, China

From 2018 to 2019, a survey of a typical lakes system in the Taihu Lake basin, China, was carried out. To provide reference values for the restoration and management of submerged vegetation in the lakes, the optical attenuation coefficient (Kd ) and euphotic depth (Zeu ) of the water body were calculated, and the distribution characteristics and factors that influenced the underwater optical field lands with different nutrition levels in the basin were analyzed. The main factor affecting the distribution of photosynthetically active radiation (PAR) in lakes in the Taihu Lake basin is suspended solids (SS), dominated by inorganic suspended matter (ISS). Chlorophyll a (Chl-a), dissolved organic carbon (DOC), and chromophoric dissolved organic matter (CDOM) all affect, although weakly, the optical characteristics of lake wetlands. In CDOM, humic-like components have a more significant impact on Kd . The Kd of lakes in the Taihu Lake basin is closely related to permanganate index (CODMn) and especially total phosphorus (TP); The growth of aquatic vegetation is increased in Shanghu, Dianshan-Yuandang, Yangcheng, and Wuli Lakes that have higher Zeu and Zeu /Depth values.

Providing Satellite Data to R/V Akademik Mstislav Keldysh during a Mission in the Southern Ocean

During cruise 79 of R/V Akademik Mstislav Keldysh in the Atlantic Antarctic, information is supplied using optical and radar high-, mid-, and low-resolution satellite data, in combination with geoinformation technologies. During field studies from December 2019 to February 2020, preliminarily processed information obtained by a multisatellite Earth remote sensing (ERS) system on sea surface temperature, sea ice concentration, icebergs, altimetry, and the concentration of near-surface layer matter (chlorophyll, particulate organic carbon, inorganic suspended particulate matter, and total suspended matter) is transmitted to the vessel. A description is given of the information infrastructure that provides the research vessel with routine satellite data that is automatically integrated into the user’s geoinformation environment as unified spatiotemporal distributions of important water environment parameters. Aspects of using satellite information when planning a ship’s route and making measurements are described.

Temporal dynamics of rotifers' feeding guilds shaped by chlorophyll‐a, nitrate, and environmental heterogeneity in subtropical floodplain lakes

AbstractIn floodplains, rotifers are among the most abundant zooplankton organisms and play an important role in ecosystem functioning. Here, we evaluated the distribution of six feeding guilds of rotifers including filter C1 (body size: <200 µm), filter C2 (body size: >200 to <600 µm), filter C3 (body size: >600 to <1000 µm), filter C4 (body size: >1000 µm), suctor, and predator for 11 years. We also analyzed the relationship between guild distribution and environmental parameters (i.e., chlorophyll‐a, phosphate, nitrate, ammonia, and inorganic suspended matter). Finally, we investigated the relationship between feeding guilds heterogeneity (abundance inconsistency) and environmental heterogeneity. Sampling occurred every 3 months from 2000 to 2010 in six shallow lakes of the Upper Paraná River floodplains. Filters C1, Filter C2, and suctors were the dominant feeding guilds. Nitrate and chlorophyll‐a shaped the temporal distribution of the guilds. An intermediate value of environmental heterogeneity was correlated with greater feeding guilds heterogeneity, potentially indicating that intermediate disturbance in the environmental variables may allow for greater differences in abundance distribution between rotifer guilds in shallow floodplain lakes. Our study elucidated the role of rotifers in food resource consumption, energy transfer, and competitive relationships in response to temporal environmental heterogeneity in subtropical floodplains.

Assessment of the salinity level of water and sediments used for irrigation and agricultural farming in Jos north

Irrigated agriculture is dependent on an adequate water supply of usable quality. The different Irrigation sites were identified randomly, and named A, B, C, D and E respectively. Therefore, water and sediment or soil samples were collected from Rukuba Road River, Yelwan Zangam River, Gangare River, Busa Buji River and Angwan Rimi River respectively in Jos, Plateau State, Nigeria to evaluate their salinity level suitability for irrigation purpose and Agricultural Farming. The analytical results shows that the Electrical conductivity (EWc), Total dissolve solids (TDS), Sodium adsorption ratio (SAR) and specific ion toxicities of water and sediment are as followed: Rukuba Road River “A” (ECw = 508.00 µs/cm, 897.00µs/cm; TDS = 440.50 mg/l, 540.60mg/l and SAR = 12.73, ND), Yalwan Zangam River “B” ( ECw = 750.00µs/cm, 987.00µs/cm; TDS = 330.20mg/l, 470.50mg/l and SAR = 12.56, ND), Gangare River “C” (ECw = 489.00µs/cm, 897.00µs/cm; TDS = 40.70mg/l, 550.90mg/l and SAR = 13.16, ND), Busa Buji River “D” (ECw = 250.00µs/cm, 499.00µS/cm; TDS = 355.60mg/l, 495.00mg/l and SAR = 14.06, ND) and Angwan Rimi River “E” (ECw = 1030.00µs/cm, 1233.00µs/cm; TDS = 460.00mg/l, 610.60mg/l and SAR = 11.20, ND). The salinity of river A B C D fall within the normal ranges which were of excellent quality and considered to be highly suitable without any restriction on the use. Water and sediment from Angwan River “E” (ECw = 1030.00µs/cm, 1233.00µs/cm; TDS = 460.00mg/l, 610.60mg/l and SAR = 19.20, ND) will be highly suitable under proper management such as improved irrigation system and schedule, light soil with good infiltration and internal drainage and plant with good salt tolerant. The variation in chemical composition of the irrigation water and sediment sources could be attributed to the fact that the Angwan Rimi River “E” water and sediment sources are located within Jos metropolis. The additions from waste waters (domestic sewage and municipal), dirt and suspended inorganic matter and automobile effluents from Mechanic workshops could contributes to the high levels of Salinity, SAR and Total hardness and specific ion toxicities of the irrigation water.

Remote estimation of total phosphorus concentration in the Taihu Lake using a semi-analytical model

ABSTRACT Eutrophication is a severe environmental problem in the most inland lakes. Taihu Lake, the third largest freshwater lake in China, is one of the most eutrophic lakes. Increased phosphorus concentration is thought to be the primary cause of water eutrophication. Proper total phosphorus (TP) monitoring is essential to effectively manage eutrophication in the Taihu Lake. In this study, 216 sample points with 172 modelling points and 44 verification points acquired from 5 field experiments in Taihu Lake, a semi-analytical model was established for estimating the TP concentration based on the absorption coefficient, with the mean absolute percentage error (MAPE) and root mean square error (RMSE) as 16.8% and 0.04 mg L−1, respectively. The application of the model on Sentinel-3 Ocean and Land Colour Instrument (OLCI) data proved the suitability of the model for satellite image with the MAPE and RMSE as 28.56% and 0.05 mg L−1. The OLCI derived TP concentration in the Taihu Lake shown the unique temporal and spatial distribution: TP concentration in Zhushan Bay, Meiliang Bay, Gonghu Bay, and the western coastal regions was significantly higher than the eastern, the southern, and the centre areas. The concentration of TP in Taihu Lake was the highest in summer and the lowest in winter. Furthermore, the versatility of this method was validated by applying in the Hongze Lake and Qiandao Lake, which is a water body dominated by inorganic suspended matter and a clean water body in China with the MAPE and RMSE as 24.10%, 19.35% and 0.004 mg L−1, 0.014 mg L−1. The results of this study could provide a reference for future remote sensing estimation of TP concentration and inland water eutrophication researches.

Tidal and Hurricane Impacts on Saltmarshes in the Northeastern Coastal and Barrier Network: Theory and Empirical Results

The responses of marsh elevation in four National Parks affected by Hurricane Sandy were examined using empirical data from surface elevation tables (SET) and modeling. The parks examined were Fire Island National Seashore and Gateway National Recreational Area in New York; Cape Cod National Seashore, Massachusetts; and Assateague Island National Seashore, Maryland. Observed vertical accretion rates were compared with calculations made with the Marsh Equilibrium Model (MEM). MEM predicts vertical accretion resulting from the accumulation of organic material in soil and the capture of suspended inorganic material at the marsh surface. MEM simulations of a decade or more of marsh elevation change at 52 SET stations were generally consistent with observations. Park-specific averages of observed vertical accretion ranged from 0.16 ± 0.33 (± 1 SD) to 0.51 ± 0.21 cm/year, while the range of calculated rates was 0.15 ± 0.03 to 0.22 ± 0.05 cm/year, depending on the park. Grand means of observed and calculated rates were 0.36 ± 0.34 and 0.19 ± 0.06 cm/year, respectively. We defined a novel metric termed normalized elevation capital (NEC) that incorporates information about tide range and elevation capital. All but 2.3% of biomass collections from all the parks fell within 0 < NEC < 1. Consistent with marsh equilibrium theory, long-term vertical accretion rate tended to be greatest, 0.4 ± 0.2 cm/year, in the range 0.4 < NEC < 0.6 where vertical accretion is dominated by organic production. Average episodic accretion during the storm from mineral deposition also was greatest and positive, 0.6 ± 0.9 cm in the range 0.4 < NEC < 0.6. Finally, one marsh in Gateway NRA, restored by an application of sediment to NEC = 0.55–0.68, had post-treatment vertical accretion rates of 0.36 ± 0.31 cm/year, not statistically different from SET stations elsewhere in Gateway, 0.57 ± 0.54 cm/year. The sediment amendment placed restored sites in the range of NEC where theory predicts that biogenic accretion should dominate vertical accretion. Model simulations suggest that current rates of vertical accretion in the parks are close to their theoretical limits, and in the absence of new sediment, extant marsh communities in these parks are unlikely to survive continued acceleration of sea-level rise in the absence of periodic sediment renourishment.

Deep Gaussian processes for biogeophysical parameter retrieval and model inversion

Parameter retrieval and model inversion are key problems in remote sensing and Earth observation. Currently, different approximations exist: a direct, yet costly, inversion of radiative transfer models (RTMs); the statistical inversion with in situ data that often results in problems with extrapolation outside the study area; and the most widely adopted hybrid modeling by which statistical models, mostly nonlinear and non-parametric machine learning algorithms, are applied to invert RTM simulations. We will focus on the latter. Among the different existing algorithms, in the last decade kernel based methods, and Gaussian Processes (GPs) in particular, have provided useful and informative solutions to such RTM inversion problems. This is in large part due to the confidence intervals they provide, and their predictive accuracy. However, RTMs are very complex, highly nonlinear, and typically hierarchical models, so that very often a single (shallow) GP model cannot capture complex feature relations for inversion. This motivates the use of deeper hierarchical architectures, while still preserving the desirable properties of GPs. This paper introduces the use of deep Gaussian Processes (DGPs) for bio-geo-physical model inversion. Unlike shallow GP models, DGPs account for complicated (modular, hierarchical) processes, provide an efficient solution that scales well to big datasets, and improve prediction accuracy over their single layer counterpart. In the experimental section, we provide empirical evidence of performance for the estimation of surface temperature and dew point temperature from infrared sounding data, as well as for the prediction of chlorophyll content, inorganic suspended matter, and coloured dissolved matter from multispectral data acquired by the Sentinel-3 OLCI sensor. The presented methodology allows for more expressive forms of GPs in big remote sensing model inversion problems.

Environmental factors affecting the nursery function for fish in the main estuaries of the Gulf of Cadiz (south-west Iberian Peninsula)

Hydrological, geomorphological, physicochemical and biological factors influence the nursery function of estuaries. Our study compared the environmental conditions and the assemblages of early life stages of fish in the main four estuaries of the Gulf of Cadiz (Cadiz Bay, Guadalquivir, Odiel-Tinto and Guadiana). Samples were taken within each estuary and on their adjacent coast, during the dry-warm seasons of 2016, 2017 and 2018. Results showed that rivers with smaller basins had a very low freshwater input and their estuaries, Odiel-Tinto and Cadiz Bay, were essentially sea extensions into the land, containing similar physicochemical conditions to nearshore zones, as well as similar assemblages and densities of early life stages of fish. Open water masses of these estuaries do not have important nursery functions. In contrast, inner zones of estuaries with bigger basins and higher freshwater discharges, Guadalquivir and Guadiana, have different environmental characteristics and a long transition zone with a well-defined salinity gradient. Their assemblages and densities of early life stages of fish were different between them and with other estuaries. The Guadalquivir estuary held the highest abundance of larval and early juvenile fish, as well as macrozooplankton biomass. The most abundant fish species in all zones of every estuary was the anchovy Engraulis encrasicolus; the Guadalquivir inner zone had the highest density. High concentration of suspended organic matter, provided by freshwater input and correlated with total suspended solid, suspended inorganic matter and turbidity, was the physicochemical characteristic more typical of the Guadalquivir. This characteristic, in addition to the salinity gradient, could explain the highest densities of macrozooplankton found in this estuary, and consequently, of early fish stages. Recurrent jellyfish blooms were observed in Cadiz Bay and the inner zone of Guadiana, affecting their nursery functions. Odiel-Tinto showed altered physicochemical and biological characteristics, which may need further specific research.

Inorganic suspended matter as an indicator of terrestrial influence in Baltic Sea coastal areas — Algorithm development and validation, and ecological relevance

Suspended particulate matter (SPM) consists both of an organic (OSPM) and an inorganic fraction (ISPM) and the latter can be used as an indicator for coastal influence in the Baltic Sea. The concentration of SPM can be derived from particle scatter if the specific scattering properties of the respective water body are known. In this paper we show that likewise, ISPM can be derived reliably from remotely sensed particle scatter. An empirical algorithm between particle scatter (AC9 data) and ISPM concentration (measured gravimetrically) was derived from in-water measurements. This regional algorithm was then applied to the iop_bpart level 2 product (i.e. the particle scatter measured at 443 nm) derived from OLCI data on Sentinel-A (S3A) using the C2RCC neural network and validated against an independent data set. The standard error of the derived OLCI match-up data was 10%, and was thus within the goal of the mission requirements of Sentinel-3.The generated S3 composite images from spring and autumn 2018 show that in the Baltic Sea most of the ISPM falls out rather close to the shore, whereas only a very small proportion of ISPM is carried further off-shore. This is also supported by in situ ISPM transects measured in the coastal zone.The ISPM images clearly highlight the areas that are most strongly influenced by terrestrial matter. Differences between the NE Baltic and the SE Baltic proper can be explained by the difference in hydrology and coastal influence as well as bathymetry and wind-wave stirring. The method is of interest for coastal zone management and for assessing the effect of seasonal changes in terrestrial run-off and wind-driven resuspension of sediments. It can also be used to evaluate the effect of climate change which has led to an increase of extreme storm and flooding events that are usually accompanied by increased erosion and run-off from land. Last but not least, turbidity caused by particles influences the light conditions in inner coastal areas and bays, which has a profound effect on pelagic productivity, the maximum growth of macroalgae as well as fish behaviour.

Remote Sensing Estimation of Lake Total Phosphorus Concentration Based on MODIS: A Case Study of Lake Hongze

Phosphorus (P) is an important substance for the growth of phytoplankton and an efficient index to assess the water quality. However, estimation of the TP concentration in waters by remote sensing must be associated with optical substances such as the chlorophyll-a (Chla) and the suspended particulate matter (SPM). Based on the good correlation between the suspended inorganic matter (SPIM) and P in Lake Hongze, we used the direct and indirect derivation methods to develop algorithms for the total phosphorus (TP) estimation with the MODIS/Aqua data. Results demonstrate that the direct derivation algorithm based on 645 nm and 1240 nm of the MODIS/Aqua performs a satisfied accuracy (R2 = 0.75, RMSE = 0.029mg/L, MRE = 39% for the training dataset, R2 = 0.68, RMSE = 0.033mg/L, MRE = 47% for the validate dataset), which is better than that of the indirect derivation algorithm. The 645 nm and 1240 nm of MODIS are the main characteristic band of the SPM, so that algorithm can effectively reflect the P variations in Lake Hongze. Additionally, the ratio of the TP to the SPM is positively correlated with the accuracy of the algorithm as well. The proportion of the SPIM in the SPM has a complex effect on the accuracy of the algorithm. When the SPIM accounts for 78%, the algorithm achieves the highest accuracy. Furthermore, the performance of this direct derivation algorithm was examined in two inland lakes in China (Lake Nanyi and Lake Chaohu), it derived the expected P distribution in Lake Nanyi whereas the algorithm failed in Lake Chaohu. Different water properties influence significantly the accuracy of this direct derivation algorithm, while the TP, Chla, and suspended particular inorganic matter (SPOM) of Lake Chaohu are much higher than those of the other two lakes, thus it is difficult to estimate the TP concentration by a simple band combination in Lake Chaohu. Although the algorithm depends on the dataset used in the development, it usually presents a good estimation for those waters where the SPIM dominated, especially when the SPIM accounts for 60% to 80% of the SPM. This research proposed a direct derivation algorithm for the TP estimation for the turbid lake and will provide a theoretical and practical reference for extending the optical remote sensing application and the TP empirical algorithm of Lake Hongze’s help for the local government management water quality.