Hydrographic Conditions Research Articles

Limiting navigational and hydrographic factors when using 3D electronic navigation charts for ship handling during locks passage

A vessel is a qualitatively complex movable object, which motion can easily predicted when proceeding in unchanged navigation conditions. When navigation conditions become more difficult prediction of vessel requires the implementation of a complex set of actions to assess the position and parameters of the vessel’s motion relative to the limits and directions of the waterway. Lock approaches are characterized by significantly congested conditions and variable dimensions, tortuosity of the waterway, and spatial navigational hazards of complex form, to indicate which floating and land marks are used, organized in complex patterns. Thus, the complexity of navigational and hydrographic conditions has a limiting effect on the navigator’s ability to control the vessel. As navigation conditions become more complex, the navigator changes priorities in controlling the vessel motion, gradually shifting from controlling the course of the vessel, to controlling the vessel’s speed vector, and then to controlling the motion of the stem and stern. Navigating a vessel in difficult navigational and hydrographic conditions requires periodic clarification of navigational information, for which the navigator turns to the navigational chart, which is a visual source of navigational information. Notwithstanding use of modern aids to navigation to display navigation information, such as, for example, an electronic chart navigation and information system (ECDIS), approaches to locks usually present difficulties when taking into account navigation and hydrographic factors, due to the variability of navigation conditions and the static nature of the navigation equipment system waterway. The use of ECDIS, which enables displaying 3D electronic navigation charts (ENCs) to solve the navigator’s tasks enroute lock approaches, is new. The effectiveness of their use in the process of ship handling through locks, which is significant for the navigator, is performed by modern methods in this article.

Seasonal patterns of microbial plankton and periodicity of climatic and hydrographic conditions in a semi-desert macrotidal wetland

Macrotidal wetlands of temperate areas are highly productive systems where interactions between land and water are particularly dynamic. Typically, these systems display temporal shifts in their water properties not only because of annual fluctuations in the photoperiod and air temperature but also due to strong tidal regimes and climatic events. In contrast with the well-studied microtidal systems, the temporal fluctuations in structure and biomass of microbial communities of semi-desert, enclosed temperate macrotidal wetlands are scarcely known, and thus the coupling between primary producers and the bacterial community occurring within them remains poorly understood. In this study we analyze the fluctuations of unicellular plankton and hydrographic conditions on a fixed station located in San Antonio Bay (SAB, Northern Argentine Patagonia) from spring 2016 to early summer 2018 with the aim of detecting possible associations with the periodicity of some climatological variables and local meteorological events. Density and biomass of microbial size fractions (pico-, nano- and microplankton) along with their nutrition modes (autotrophic, potentially mixotrophic and heterotrophic) were assessed based on bi-weekly samplings. In addition, the study also examines the relationships of autotrophs and bacterioplankton with the frequency, duration, and magnitude of phytoplanktonic blooms, as well as the biomass contribution of dominant diatom species. We found a microbial-dominated planktonic system with increased densities of both autotrophic and heterotrophic picoplankton and flagellated protists. The biomass of potentially mixotrophs dominated over that of autotrophs and heterotrophs along the entire period. Autotrophic biomass showed a single annual maximum in summer, while chlorophyll-a displayed a biannual cycle. Neither chlorophyll-a nor autotrophic biomass reached high values as compared to other coastal systems with no clear dominant phytoplanktonic taxa. The annual phytoplanktonic biomass cycle in SAB appears not to be related to those of other coastal environments from North Patagonia. We infer that the strong macrotidal dynamics limits primary production and turns this system into a high nutrient/low chlorophyll one that exports surplus nutrients in tide-driven pulses to neighboring areas.

Genetic identification of zoonotic parasite Anisakis pegreffii (Nematoda: Anisakidae) parasitizing the shortfin squid Illex argentinus under commercial exploitation in the Southwestern Atlantic Ocean.

Despite the shortfin squid, Illex argentinus, is one of the most important commercial species for the Argentine fisheries, being the third frozen product exported to Europe, the occurrence and distribution of zoonotic anisakid nematodes is scarcely reported. A total of 712 I. argentinus distributed in 17 samples, corresponding to its three main commercial stocks, caught along its distribution range in Argentine waters were examined for anisakid parasites. In total, 360 nematodes were detected in the viscera, however no infestations in the mantle were observed. According to their morphology, all the larvae (L3) were assigned to the genus Anisakis. Genetic identification was performed by sequence analysis of the mitochondrial (mtDNA cox2) gene loci resulting in the record of only Anisakis pegreffii. Distance-based multiple linear regressions (DistLM) evidenced that dorsal mantle length (ML) and date of capture (as surrogate of cohort) were the most important predictors of parasite abundance across infrapopulations in I. argentinus. At component population, DistLM analysis showed that ML and latitude (indirectly representing a gradient in water temperature) were the most important variables determining the prevalence of parasites, however, its mean abundance was only influenced by ML. Parasite burdens were temporally inestable, due to variability in recruitment to host populations, being associated with changing hydrographic conditions and the opportunistic feeding behaviour and annual life cycle of the hosts. The genetic identification of A. pegreffii is relevant for both human health and the fishery industry, given its importance as an etiological agent of human anisakiosis. Due to the restriction of larvae to internal organs, the risk of anisakiosis by the consumption of edible parts of I. argentinus is low.

Pigment-based Phytoplankton Size Classes and Community Composition along the Western Antarctic Peninsula during the Turkish Antarctic Expedition of 2019

This study investigates the spatial variability of phytoplankton size classes (PSCs) and community composition along the western Antarctic Peninsula (WAP) during the Turkish Antarctic Expedition (TAE-III) in 2019. Using high-performance liquid chromatography (HPLC) pigment analysis, microscopy, and hydrographic data, we characterized phytoplankton communities across 11 stations during the Turkish Antarctic Expedition (TAE-III). The results revealed substantial regional differences, with nanophytoplankton contributing the most to the total phytoplankton biomass (23–78%), followed by microphytoplankton (3–53%) and picophytoplankton (1–69%). Prominent pigments, including chlorophyll-a, fucoxanthin, and 19-hexanoloxyfucoxanthin, indicated diatom and haptophyte dominance in specific areas. Variations in community composition were strongly influenced by sea surface temperature, salinity, and nutrient availability, driven by regional hydrographic conditions and ice melt dynamics. These findings enhance our understanding of phytoplankton adaptive strategies under changing environmental conditions and highlight their crucial role in the WAP`s polar marine ecosystem. This study provides baseline data essential for monitoring climate-driven changes in Antarctic phytoplankton communities.

Aquaculture source of atmospheric N2O in China: Comparison of system types, management practices and measurement methods.

Aquaculture systems contribute to atmospheric N2O, but the magnitude of this N2O source is largely uncertain. Here, we synthesized data from 139 aquaculture sites based on 59 peer-reviewed publications, and estimated that China's aquaculture systems emitted 9.68 Gg N yr-1 (4.12 Tg CO2-eq yr-1). N2O emission varied significantly according to system types, farmed species, physical dimensions of the system, hydrographical conditions, and management practices. Of these, inland pond systems had a higher N2O flux (268.38 ± 75.96 mg N m-2 yr-1) and indirect N2O emission factor (4.4 ± 0.9‰) than the other system types. Mixed species farming tended to emit less N2O than monospecific farming, whereas small (< 1 ha) and shallow ponds (< 1 m) were hotspots for N2O emission. Flux values based on different wind-driven diffusion models varied widely, and the model CC98 agreed most closely with direct measurements using floating chamber. Overall, aquaculture waters had a lower emission intensity than streams, rivers and reservoirs, but comparable to estuaries and lakes. Rapid expansion of the aquaculture sector and the limited N2O data for this sector, especially for rice-aquaculture co-culture systems, highlight the need for better monitoring and on-site measurements to refine the inventory of greenhouse gas emissions from the aquaculture systems.

An Assessment of the Construction and Hydrographic Conditions of Bukhtarma and Ust-Kamenogorsk Reservoirs in the East Kazakhstan Region for 2017–2021

The article defines the morphometric, hydrochemical, and hydrobiological parameters of the Ust-Kamenogorsk reservoir, located on the territory of Ablaketka and the Bukhtarma reservoir, formed in the zone of narrowing of the mountain valley (1960), 12 km below the confluence of the Bukhtarma River with the Irtysh River. When determining deviations in indicators of the reservoirs, data from gauging stations have been taken into account. The purpose of the article is to conduct a comprehensive assessment of the current state of two large reservoirs in the East Kazakhstan region during the specified time period. The novelty of this topic lies in its comprehensive approach to assessing various aspects of the reservoirs’ condition in a specific region over a defined period. This approach enables the identification of current trends and issues and facilitates the proposal of practical measures to address them and enhance water resource management. As a result of this research work, after analyzing changes in indicators, the condition of the reservoirs was determined. During the research work, according to the results of hydrochemical studies, the Bukhtarma reservoir is favorable for the habitat of aquatic organisms, and in the Ust-Kamenogorsk reservoir, a positive change in hydrochemical parameters has been noted compared with 2020. In addition, after analyzing the research indicators, it was proposed to form specially protected areas in the Bukhtarma reservoir, suitable for use in connection with the distribution of valuable fish listed in the Red Book of the Republic of Kazakhstan. When demonstrating the location of gauging stations, methods of remote sensing of the earth and the method of geoinformation mapping were used.

Contrasting copepod community composition in two Greenland fjords with different glacier types

Abstract Greenland's fjord ecosystems are strongly influenced by meltwater discharge from glaciers. Marine-terminating glaciers can significantly enhance primary production during the melt season (compared to land-terminating glaciers), but their impact on secondary producers is not well understood. Here, we study seasonal changes in the zooplankton community (&amp;gt;50 μm) and grazing rates along two fjord transects in southwest Greenland influenced by different glacier types. Zooplankton biomass was comparable between the fjords, but community composition differed during summer. Nuup Kangerlua, a predominantly marine-terminating system, was characterized by large, herbivorous copepods and a longer summer grazing period in connection with the summer bloom. Ameralik, influenced by a land-terminating glacier, was characterized by small, omnivorous copepods, particularly Microsetella norvegica and Oncaea spp., and indicated a faster post-bloom transition towards regenerated production. Local hydrographic conditions also impact copepod biomass. A station with high biomass was found in Ameralik, potentially linked to a frontal zone where fjord water masses meet, providing favorable grazing conditions. We hypothesize that a future transformation from marine- to land-terminating glaciers could result in an increased abundance of smaller copepods, as observed in Ameralik. Such a community would constitute a less lipid-rich food source for higher trophic levels.

Observed Pathways and Interannual Variability of the Warm Inflow Onto the Continental Shelf in the Southern Weddell Sea

AbstractModel projections suggest that the continental shelf in the southern Weddell Sea may experience a shift from today's near‐freezing temperature to a much warmer state, where warm water floods the shelf and basal melt rates beneath the Filchner Ronne Ice Shelf increase dramatically. Today, the Filchner Trough serves as a conduit for the southward flow of Warm Deep Water (WDW) during summer and, thus, requires continuous monitoring of its hydrographic conditions. An extensive network of moorings was installed at key sites along the inflow pathway from 2017 to 2021, to expand on existing mooring records starting in 2014. The moorings complemented with under‐ice profiling floats reveal two inflow pathways, where WDW enters along the eastern flank of the Filchner Trough as well as through a smaller trough east of there. Within the observed period, 2017 and 2018 feature anomalously warm inflows. The inflow is regulated by the heaving of isopycnals over the continental slope, and the southward propagation toward Filchner Ice Shelf is two times faster during these warm years. Furthermore, the warm years coincide with low summer sea ice concentration, which enhances surface stratification through increased freshwater input and modifies sea ice‐ocean stresses that both act to lift the warm water layer and increase the temperatures on the continental shelf. Finally, the recent record low sea ice conditions around the Antarctic emphasize the importance of our findings and raise concerns regarding a potentially increasing presence of WDW on the southern Weddell Sea shelf.

Investigations-based results on the hydrographic conditions with special reference to the tourist bathing areas of the protected Romanian littoral

The aim of the present work is related to the new hydrographic conditions within newly developed coastal areas through coastal protection measures extension. The study also seeks to assess the impact on the touristic bathing areas and its safety. The new bathymetry, induced by the sediment size, together with currents propagation into the bathing areas adjacent to the newly arranged beach areas were subject of Conductivity Temperature and depth profiler (CTD) and Acoustic Doppler Current Profiler (ADCP) measurements in relation to the summer waves regime and sea level variations. Several experiments habitually conducted during the summer period were considered; the experiments are related to the marine hazards associated to the swimming areas, such as seasonal storm-inducing currents and the propagation of the rip currents in the nearshore, but also to the specific marine currents setups around beach protection groins and longitudinal breakwater, the influence of vertical water movements, including up-welling and specific intensifications in the periods with complex stormy waves.

Influence of mini warm pool extent on phytoplankton productivity and export in the Arabian sea

The Arabian Sea is a highly productive tropical ecosystem of the Indian Ocean that supports high fluxes of particulate organic carbon to the mesopelagic zone from two distinct periods of elevated biological productivity associated with the semiannual reversals of the monsoonal wind system. There are now strong indications that the Arabian Sea's monsoonal wind patterns and hydrographic conditions are being impacted by long-term temperature increases, but the consequences of these changes on primary production and carbon export to the mesopelagic zone are unknown. This is especially true for the summer monsoon period when cloud cover obscures much of the Arabian Sea basin and therefore precludes remotely sensed ocean color measurements for estimating phytoplankton biomass and productivity. Here we overcome this limitation by using a database of bio-optical profiles from Biogeochemical Argo floats collected over the last decade to evaluate the impact of interannual temperature increases on Arabian Sea primary production and carbon export. We classify individual years of float observations based on the spatial extent of the Arabian Sea Mini Warm Pool that appears in the southeast Arabian Sea before the onset of the summer monsoon. This Mini Warm Pool, which begins to build in winter and collapses with the onset of the summer monsoon in late spring, has gained considerable interest on account of its influence on the timing of the onset of the summer monsoon. We observed a 35 percent decrease in primary production during the summer monsoon phytoplankton bloom in strong warm pool years, and a 13 percent decrease in particle stocks in the upper mesopelagic zone following the peak of the bloom. Decreases in production and export were additionally accompanied by a decrease in average particle size, indicating a shift from larger cells like diatoms that appear from fertilization of the oligotrophic waters to smaller phytoplankton size classes in response to a deepening of the thermocline and increased stratification of the water column. These results suggest changes in phytoplankton community structure and further decreases in primary production and carbon export in the Arabian Sea in response to future warming.

Tidal influence on Fish Faunal Distribution and Species Diversity in Kakum Estuary, Ghana

Estuarine and coastal areas are complex and dynamic aquatic environments. In such an area, where river water mixes with seawater, a large number of physical and chemical processes take place, which may influence water quality thereby affecting the distribution and diversity of the biota. The study was conducted in the transition period of dry and wet conditions from February to May 2018. The influence of low and high tides on the hydrographic parameters such as salinity, dissolved oxygen, and water temperature in the three sampling stations was analyzed in relation to fish faunal distribution and species diversity of the estuary. The common fish species in the estuary were juveniles of Sarotherodon melanotheron and Mugil cephalus, Liza falcipinnis and the crab Callinectes amnicola. These species were encountered during both low and high tides in all sampling stations, which indicates their adaptation to a broader range of hydrographic conditions. The majority of species encountered were juveniles. Although most of the fish species were marine in origin, some including Tilapia zillii, Hemichromis fasciatus and Apolochelichthys spilauchen were freshwater in origin whilst, S. melanotheron is a resident fish species in the estuary. Length-frequency distribution and length-weight relationships of S. melanotheron, T. zillii, L. falcipinnis, Mugil cephalus, and Eucinosthomus melanopterus which were the five most dominant fish species during the period of study in Kakum estuary were analyzed. The modal sizes of the dominant fish species were mainly juveniles in the length-frequency distribution. The length-weight relationships of S. melanotheron, L. falcipinnis and M. cephalus showed allometric growth, whereas that of T. zillii and E. melanopterus showed isometric growth. The study, therefore, identified that Kakum estuary is a transitional zone for both marine and freshwater fish species using the estuarine ecosystem as nursery grounds. The presence of marine and freshwater-origin species, and resident species in the estuary further suggest that estuaries are highly dynamic, and slight changes in their environment can cause a great deal of harm to its fish biota.

Seasonal variations in the contribution of zooplankton fecal pellets to the particulate organic carbon fluxes over the slopes of the Pacific Arctic region

As part of the Korea Arctic Mooring System (KAMS), sequential sediment traps were deployed at KAMS1 over the East Siberian Sea slope (∼115 and ∼335 m) and at KAMS2 over the Chukchi Sea slope (325 m) to collect sinking particles from August 2017 to August 2019. Fecal pellet carbon (FPC) fluxes and their contribution to the particulate organic carbon (POC) fluxes were measured to assess the role of zooplankton fecal pellets in the biological carbon pump at both sites. FPC fluxes increased at the onset of an under-ice bloom and peaked during the melt period at both sites in 2018. At KAMS1, a remarkable increase in FPC fluxes reflected the enhanced grazing of large copepods during the anomalously productive spring and summer of 2018, however their contributions to the POC fluxes mostly remained <10%. At KAMS2, relatively low FPC fluxes during the under-ice bloom suggested the export of a larger proportion of pellets produced by small copepods. Sustained FPC fluxes from January to May 2018 at KAMS2 contributed up to 24% of the POC fluxes, possibly resulting from pellet production by overwintering copepods grazing on particles laterally transported into the region in the presence of ice. These results indicate that despite their limited contribution to the POC fluxes, FPC fluxes varied with food availability, zooplankton community structure, and hydrographic conditions over the East Siberian and Chukchi Sea slopes.

Role of phytoplankton composition on exudation of dissolved organic carbon in the Bay of Bengal

Phytoplankton in the marine environment exudates part of the primary production as dissolved organic carbon (DOC) into the surrounding waters. The rate of exudation of DOC is depended on the hydrographic condition, nutrient availability, phytoplankton composition, and their size structure. To examine this, samples were collected from the coastal and offshore regions where different hydrographic conditions exists in the Bay of Bengal. The coastal waters were relatively low saline, rich in inorganic nutrients, high phytoplankton biomass (Chl-a) and primary production in the coastal compared to offshore regions. The photic zone integrated Chl-a displayed insignificant difference between coastal and offshore regions whereas higher photic zone integrated primary production was observed in the former than latter region. Dominance of microplankton was observed in the coastal waters associating with high inorganic nitrogen concentrations, in contrast, picoplankton dominated in the offshore region associating with low inorganic nitrogen but high organic nitrogen concentrations. Due to high surface-to-volume ratio of picoplankton, ∼45% of the primary production exudated as DOC in the offshore compared to the coastal region (∼12%) due to dominance of microplankton. The sum of primary production and DOC exudation, called total primary production, was almost equal in the coastal and offshore regions. The mean phytoplankton biomass normalized primary production (pB) in the Bay of Bengal was low (17 ± 8 mgC mgChl-a−1 d−1) compared to Arabian Sea (37 ± 5 mgC mgChl-a−1 d−1). In contrast pB estimated based on total primary production is close (30 ± 16 mgC mgChla−1 d−1) to that of the Arabian Sea (37 ± 5 mgC mgChl-a−1 d−1) suggesting that the Bay of Bengal is equally productive compared to that of Arabian Sea than hitherto hypothesized due to strong stratification and less nutrients input in the former basin. The low sinking carbon flux observed below the photic zone is attributed to the release of primary production as DOC. The released DOC from the phytoplankton may support heterotrophic activity as evidenced by the existence of strong net heterotrophy in the Bay of Bengal. This may lead to the time lag between primary and export productions. None of these processes were incorporated into the numerical models resulting in inaccurate simulations of carbon cycling in the northern Indian Ocean. Modifications in the models by incorporating these processes may improve model simulations for a better understanding the modifications in biogeochemical processes due to climate change in the Bay of Bengal.

Unveiling the Faunal Diversity in the Water Column Adjacent to Two Seamounts in the Deep Arabian Sea Using Environmental DNA Metabarcoding

The diversity of organisms inhabiting deep-sea ecosystems, such as seamounts, has hitherto remained under-studied. In this study, we report on the faunal diversity in the water column adjacent to the summit and periphery of two seamounts (SMS2 and SMS3) and an oxygen minimum zone site located away from the seamounts in the southeast Arabian Sea. Environmental DNA (eDNA) in the water column was metabarcoded using the Cytochrome Oxidase C subunit I (COI) gene marker and Oxford Nanopore sequencing technology. Hydrographic conditions revealed that the summits of the seamounts intersect with the core oxygen minimum zone between depths of 300 and 600 m. Comparisons of COI gene sequences with those in available databases, MIDORI and BOLD, indicated the existence of a diverse group of novel organisms in the study area. Crustaceans dominated (75–95%) in the summit and periphery of the SMS2 and the OMZ site, while Cnidaria (56–63%) and Chordata (55%), respectively, dominated the summit and periphery of SMS3. Overall, the current study highlights the broad diversity of organisms living in the water column around the seamounts and underscores the potential of eDNA for exploring them.

Stable isotopic composition of tissues and shells in the Mediterranean mussel, Mytilus galloprovincialis, in estuarine and aquaculture settings

The Mediterranean mussel, Mytilus galloprovincialis Lamarck, 1819 is a widely distributed commercially important bivalve species, and is one of two cultivated bivalve species in the Adriatic Sea, with the Krka River estuary being a key aquaculture location. Understating the feeding ecology of M. galloprovincialis could help aquaculture be more efficient. The aim of this study is to use stable isotopes to advance our understanding of M. galloprovincialis feeding ecology, as well as explore the potential of their shell as proxies for environmental change. We analyzed stable isotope composition (hereafter, δ13C and δ15N), of M. galloprovincialis soft tissue, as well as the δ15N signature of its shell, over one year at multiple sites in the Krka River estuary. Mussels showed differences in the isotopic niche depending on the site, indicating that feeding varies according to geographic location, likely due to specific conditions in the Krka River estuary and differences in food availability. During our entire survey period, marine organic carbon was the dominant source in the mussels cultivated in the Krka estuary. However, in the period from late summer to late autumn, the contribution of freshwater carbon sources increased for both sites situated in the middle estuary. The distinct feeding patterns observed at each sampling site could be attributed to a combination of factors such as local hydrographic conditions, food availability, and the presence of other competing species. Overall, the stable isotope results present valuable information on the feeding ecology of Mytilus galloprovincialis, highlighting the complex interactions between environmental factors and feeding habits. The results of our study contribute to the isotope data archive for M. galloprovincialis. Furthermore, this work shows the potential of M. galloprovincialis shell δ15N values as an indicator for nitrogen loading in aquaculture settings and coastal marine environments.

Diversity and distribution of small-sized planktonic ciliate communities in the East China Sea

Ciliates are an important ecological component in the microbial food web, but few studies have been conducted on the spatial distribution of small-sized planktonic ciliate communities in the East China Sea (ECS). Investigating ciliate communities using conventional morphological approaches is particularly difficult for the small, fragile, and naked species. Therefore, we applied DNA metabarcoding analysis to explore the spatial pattern of small-sized planktonic ciliate community structure within the surface, deep chlorophyll maximum (DCM), and bottom layers. Results showed the cosmopolitan species, Leegaardiella sp., was dominant and widespread in the ECS. The relative abundance of the mixotrophic family Tontonnidae decreased in the deeper layer. We characterized water masses of the ECS using environmental variables. In nano-sized ciliate communities, non-metric multidimensional scaling (NMDS) plots revealed a correlation with temperature, salinity, density, and depth. The circulation patterns were similar to cluster analysis results, suggesting that hydrographic conditions shaped small-sized ciliate community composition.

Coral geochemical response to uplift in the aftermath of the 2005 Nias–Simeulue earthquake

On 28 March 2005, the Indonesian islands of Nias and Simeulue experienced a powerful Mw 8.6 earthquake and coseismic uplift and subsidence. In areas of coastal uplift (up to ~ 2.8 m), fringing reef coral communities were killed by exposure, while deeper corals that survived were subjected to habitats with altered runoff, sediment and nutrient regimes. Here we present time-series (2000–2009) of Mn/Ca, Y/Ca and Ba/Ca variability in massive Porites corals from Nias to assess the environmental impact of a wide range of vertical displacement (+ 2.5 m to − 0.4 m). High-resolution LA-ICP-MS measurements show that skeletal Mn/Ca increased at uplifted sites, regardless of reef type, indicating a post-earthquake increase in suspended sediment delivery. Transient and/or long-term increases in skeletal Y/Ca at all uplift sites support the idea of increased sediment delivery. Coral Mn/Ca and Ba/Ca in lagoonal environments highlight the additional influences of reef bathymetry, wind-driven sediment resuspension, and phytoplankton blooms on coral geochemistry. Together, the results show that the Nias reefs adapted to fundamentally altered hydrographic conditions. We show how centuries of repeated subsidence and uplift during great-earthquake cycles along the Sunda megathrust may have shaped the modern-day predominance of massive scleractinian corals on the West Sumatran reefs.

The physical and biogeochemical parameters along the coastal waters of Saudi Arabia during field surveys in summer, 2021

Abstract. During the last decades, the coastal areas of the Kingdom of Saudi Arabia, on the Red Sea and the Arabian Gulf, have been subjected to intense economic and industrial growth. As a result, it may be expected that the overall environmental status of Saudi Arabian coastal marine waters has been affected by human activities. As a consequence, adequate management of the Saudi Arabian coastal zone requires an assessment of how the various pressures within this zone impact the quality of seawater and sediments. To this end, environmental surveys were conducted over 15 hotspot areas (areas subject to environmental pressures) in the Saudi Arabian coastal zone of the Red Sea and over three hotspot areas in the Saudi Arabian waters of the Arabian Gulf. The survey in the Red Sea, conducted in June/July 2021, acquired measurements from hotspot areas spanning most of the Saudi coastline, extending from near the Saudi–Jordanian border in the north to Al Shuqaiq and Jizan Economic City (close to the Saudi–Yemen border) in the south. The survey in the Arabian Gulf, carried out in September 2021, included the areas of Al Khobar, Dammam and Ras Al Khair. The main objective of both cruises was to record the physical and biogeochemical parameters along the coastal waters of the kingdom, tracing the dispersion of contaminants related to specific pressures. Taken together, these cruises constitute the first multidisciplinary and geographically comprehensive study of contaminants within the Saudi Arabian coastal waters and sediments. The measurements acquired revealed the influence of various anthropogenic pressures on the coastal marine environment of Saudi Arabia and also highlighted a strong influence of hydrographic conditions on the distribution of biochemical properties in the Red Sea and the Arabian Gulf. The data can be accessed at SEANOE https://doi.org/10.17882/96463 (Abualnaja et al., 2023), whereas the details of the sampling stations are available at https://mcep.kaust.edu.sa/cruise-postings (last access: 25 March 2024). The dataset includes the parameters shown in Tables 1a, b and 2a.

Coccolithophore and paleoproductivity variations in the subtropical western South Atlantic since the late deglaciation

Here we present a record of coccolith variation over the past 14 kyr BP from core KF-02 (25.84°S, 45.2°W; 827 m water depth) collected from the continental slope of the São Paulo Bight (SPB), located in the subtropical western South Atlantic. Additionally, we estimated primary productivity based on Florisphaera profunda nannoliths and compared it with other published investigations on the productivity based on different proxies. The coccolith assemblages varied and agreed with the main regional oceanic and atmospheric changes since the latest deglaciation, likely in response to the terrestrial influence and nutricline depth variations. Among eutrophic species, Gephyrocapsa oceanica was more abundant during times with enhanced productivity promoted by the input of terrestrial material. Emiliania huxleyi and small Gephyrocapsa dominated the middle Holocene samples and probably benefitted from the more stable oceanic conditions and the enhanced light availability promoted by the Brazil Current. The paleoproductivity estimates indicated that moderate levels of productivity persisted since the latest deglaciation with a decreasing trend after the middle Holocene, delaying the productivity reduction that was indicated by other regional studies based on planktonic foraminifera. Apparently, seasonal regional hydrographic conditions were responsible for changing coccolith assemblages, and these were not reflected by the planktonic foraminifera G. bulloides variations.

Spatiotemporal variation, composition, and implications for transport flux of nitrogen in Leizhou Peninsula coastal water, China

Nitrogen, as the main bioactive element, plays an important role in biological productivity, ecosystem function, and biogeochemical processes in marine environment. In this study, seawater samples collected from China’s Leizhou Peninsula coastal water (LZPCW) during dry, normal, and wet seasons in 2018 were explored to reveal the spatiotemporal variation, composition, and transport flux of dissolved inorganic nitrogen (DIN) linked to hydrographic condition. DIN concentration and speciation showed significantly seasonal variation (P < 0.01), and the concentration of DIN species was significantly higher in dry season than other seasons. The annual mean DIN concentration was 8.01 ± 5.79 μmol L−1. In addition, the N–NO2−, N–NO3− and N–NH4+ were significantly different in the DIN bulk in different seasons. The largest fraction of DIN was N–NO3−, followed by N–NH4+, the lowest was N–NO2−, comprising up to 67.92 ± 23.20%, 23.90 ± 23.19% and 8.18 ± 8.19%, respectively. Besides, the Beibu Gulf was subjected to 7.28 × 1010 mol DIN annual flux through the Qiongzhou Strait. The annual transport fluxes of N–NO2−, N–NO3−, and N–NH4+ accounted for 6.43%, 77.20% and 16.36%, respectively. The DIN concentration and coastal water flow led to the largest DIN flux transport in dry season. This study revealed that the coastal ocean currents, river plumes and human activities jointly drove the dynamic variations of N species in LZPCW. It provides a baseline data for studying the spatiotemporal effects of hydrographic condition on nitrogen distribution and transport flux in the LZPCW, which is implications for understanding nutrients dynamics and coastal water quality management in future.