Structures In Coastal Waters Research Articles

Spatio-temporal dynamics of phytoplankton community structure in the coastal waters of the Southern Beibu Gulf.

This study was conducted during October 2021 (autumn) and April 2022 (spring) to explore the phytoplankton community structure, their distribution characteristics, and the influence of environmental factors in the coastal waters of the Southern Beibu Gulf. The 15 sampling sites were grouped based on the difference in offshore distance to analyze the temporal and spatial differences in community structure and environmental driving in the investigated sea area of the coastal waters of the Southern Beibu Gulf. Permutational multivariate analysis of variance was conducted on the sample data in time and space, revealing that there is no significant difference in space (p > 0.05), but there is significant difference in time (p < 0.05). Notably, water pressure, pH, chemical oxygen demand, nitrite, and labile phosphate were higher in autumn, while total ammonia nitrogen, dissolved oxygen, and suspended solids were significantly higher in spring. Additionally, the study identified 87 phytoplankton species belonging to 6 phyla, dominating by Bacillariophyta, followed by Dinophyta and Cyanophyta. The phytoplankton density, Shannon Weiner's diversity index (H'), Pielou's evenness index (J), and Margalef's richness index (D) ranged from 84.88 to 4675.33 cells L-1, 0.56 to 2.58, 0.26 to 0.89, and 1.21 to 3.64, respectively. Permutational multivariate analysis of variance showed non-significant spatial differences in phytoplankton composition (p > 0.05) but seasonal differences (p < 0.05). Furthermore, canonical correspondence analysis (CCA) identified pH, dissolved oxygen, suspended solids, chemical oxygen demand, nitrite, and labile phosphate as key environmental factors influencing the phytoplankton community structure (p < 0.05). In this study, the dynamic changes of phytoplankton community structure and environmental factors in the southern coastal waters of Beibu Gulf were analyzed in detail from two aspects of time and space. The key environmental factors to protect the ecological environment in the southern coastal area of Beibu Gulf were found out. It provides a reference method and theoretical basis for the management and protection of Beibu Gulf and other tropical marine environment.

Numerical modeling of the long surface wave impact on a partially immersed structure in a coastal zone: Solitary waves over a flat slope

This paper describes the numerical simulation of the solitary wave impact on a partially immersed and fixed structure located over a flat coastal slope. This topic is related to the need for assessment of the possible impact of long waves, such as tsunamis, on partially immersed structures in coastal waters. Numerical algorithms on a movable grid adapting to the motion of the shore point are developed for a fully nonlinear dispersive model and a dispersionless shallow water model. Their validation is carried out by comparing the obtained solutions with the data from laboratory experiments and with the results obtained using a fully nonlinear potential flow model. The study shows that the difference between the maximum wave impact on the body at the foot of the slope and near the shore can be up to 6 times. In many cases, the maximum horizontal component of the wave force occurs under the influence of the wave reflected from the shore, indicating the need to consider the influence of the shore-reflected wave when assessing the impact of long waves on structures located in coastal waters. Furthermore, the need to use runup algorithms instead of reflective boundary conditions (vertical wall) has been identified for gentler slopes, where the differences in the wave impact for these two configurations can be 2–3 times.

Distinct response of total and active fungal communities and functions to seasonal changes in a semi‐enclosed bay with mariculture (Dongshan Bay, Southern China)

AbstractIncreasing evidence suggests that fungal communities are key components of biogeochemical cycles in coastal ecosystems. However, at a regional scale, the major drivers of the seasonal and spatial distribution of fungi in areas impacted by mariculture remain largely unknown. Intensive aquaculture takes place in Dongshan Bay of Fujian, China, a typical subtropical marine ecosystem with multiple environmental gradients extensively perturbed by anthropogenic activities. To better understand the consequences of mariculture on fungal community composition and activities, we simultaneously evaluated the temporal (four different seasons) and spatial dynamics in total (DNA) and active (RNA) fungal communities of Dongshan Bay in relation to several major physicochemical properties. Our results revealed that fungal communities in the Bay were highly diverse, but showed the ubiquitous dominance of Dikarya and the occasional predominance of Glomeromycota, Mucoromycota, Mortierellomycota, Chytridiomycota, Olpidiomycota, and Rozellomycota. Fungal diversity varied much more with season than with the degree of aquaculture activity, for both total and active communities. This notion is supported by co‐occurrence networks exhibiting a clear seasonal pattern. Furthermore, fungal community structure in coastal waters showed distinct relationships with environmental factors varying both with season and in space. For both total and active fungal communities, a combination of environmental variables including temperature, dissolved oxygen, and nitrite exhibited the greatest impact on community structure. Our study demonstrates a distinct spatiotemporal dynamics of both total and active fungi and provides a foundation to better understand the ecological roles of marine fungi in coastal ecosystems in relation to mariculture activities.

Kinetic modulation of bacterial hydrolases by microbial community structure in coastal waters.

In this study, we hypothesized that shifts in the kinetic parameters of extracellular hydrolytic enzymes may occur as a consequence of seasonal environmental disturbances and would reflect the level of adaptation of the bacterial community to the organic matter of the ecosystem. We measured the activities of enzymes that play a key role in the bacterial growth (leucine aminopeptidase, β- and α-glucosidases) in surface coastal waters of the Eastern Cantabrian Sea and determined their kinetic parameters by computing kinetic models of distinct complexity. Our results revealed the existence of two clearly distinct enzymatic systems operating at different substrate concentrations: a high-affinity system prevailing at low substrate concentrations and a low-affinity system characteristic of high substrate concentrations. These findings could be the result of distinct functional bacterial assemblages growing concurrently under sharp gradients of high-molecular-weight compounds. We constructed an ecological network based on contemporaneous and time-delayed correlations to explore the associations between the kinetic parameters and the environmental variables. The analysis revealed that the recurring phytoplankton blooms registered throughout the seasonal cycle trigger the wax and wane of those members of the bacterial community able to synthesize and secrete specific enzymes.

Non-hydrostatic modelling of the wave-induced response of moored floating structures in coastal waters

Predictions of the wave-induced response of floating structures that are moored in a harbour or coastal waters require an accurate description of the (nonlinear) evolution of waves over variable bottom topography, the interactions of the waves with the structure, and the dynamics of the mooring system. In this paper, we present a new advanced numerical model to simulate the wave-induced response of a floating structure that is moored in an arbitrary nearshore region. The model is based on the non-hydrostatic approach, and implemented in the open-source model SWASH, which provides an efficient numerical framework to simulate the nonlinear wave evolution over variable bottom topographies. The model is extended with a solution to the rigid body equations (governing the motions of the floating structure) that is tightly coupled to the hydrodynamic equations (governing the water motion). The model was validated for two test cases that consider different floating structures of increasing geometrical complexity: a cylindrical geometry that is representative of a wave-energy-converter, and a vessel with a more complex shaped hull. A range of wave conditions were considered, varying from monochromatic to short-crested sea states. Model predictions of the excitation forces, added mass, radiation damping, and the wave-induced response agreed well with benchmark solutions to the potential flow equations. Besides the response to the primary wave (sea-swell) components, the model was also able to capture the second-order difference-frequency forcing and response of the moored vessel. Importantly, the model captured the wave-induced response with a relatively coarse vertical resolution, allowing for applications at the scale of a realistic harbour or coastal region. The proposed model thereby provides a new tool to seamlessly simulate the nonlinear evolution of waves over complex bottom topography and the wave-induced response of a floating structure that is moored in coastal waters.

Was Dissolved Nitrogen Regime Driving Diatom to Dinoflagellate Shift in the Bohai Sea? Evidences From Microcosm Experiment and Modeling Reproduction

AbstractThe shift of diatom dominance to combination of diatom and dinoflagellate dominance in the Bohai Sea (BS), China might be associated with the change of dissolved nitrogen (DN). This study combines field investigation, ship‐based microcosm experiments, a nitrogen biogeochemical model, and statistical analysis to reveal the impact of DN loading on the dominance of diatoms and dinoflagellates in the BS, considering the quantitative relationship between the algal growth/death and nitrogen migration/transformation processes. The diatom to diatom‐dinoflagellate shift was significantly associated with the DN regime shift of oxidized nitrogen (NO3‐N) to reduced nitrogen (NH4‐N and dissolved organic nitrogen [DON]) since the mid‐1990s. This phenomenon was supported by microcosm and numerical experiments: (a) Gonyaulax verior as a dominant dinoflagellate in the BS efficiently absorbed/assimilated NH4‐N, and it can also utilize DON derived from centric diatoms; Chaetoceros densus as dominant centric diatoms in the BS was able to absorb/assimilate NO3‐N, and it can also utilize DON derived from the Xiaoqing River; (b) The change in dinoflagellates/diatoms ratios was reproduced with the change in DN regime from the 1980s to the 2010s by the proposed nitrogen biogeochemical model based on localized parameters in the BS. Moreover, mixotrophism and stronger survival stability, associated with the faster NH4‐N and DONalgal uptake and slower decomposition of G. verior, also supported the shift from diatoms to diatoms–dinoflagellates during high variations in nutrient supply. This study infers the phytoplankton regime shift mechanism associated with the DN structure in coastal waters, providing a credible scientific basis for the shift from water quality‐based to ecosystem‐based environmental management.

Co-occurrence networks reveal the central role of temperature in structuring the plankton community of the Thau Lagoon

To identify the environmental factors that drive plankton community composition and structure in coastal waters, a shallow northwestern Mediterranean lagoon was monitored from winter to spring in two contrasting years. The campaign was based on high-frequency recordings of hydrological and meteorological parameters and weekly samplings of nutrients and the plankton community. The collected data allowed the construction of correlation networks, which revealed that water temperature was the most important factor governing community composition, structure and succession at different trophic levels, suggesting its ubiquitous food web control. Temperature favoured phytoplanktonic flagellates (Cryptophyceae, Chrysophyceae, and Chlorophyceae) and ciliates during winter and early spring. In contrast, it favoured Bacillariophyceae, dinoflagellates, phytoplankton < 6 µm and aloricate Choreotrichida during spring. The secondary factors were light, which influenced phytoplankton, and wind, which may regulate turbidity and the nutrient supply from land or sediment, thus affecting benthic species such as Nitzschia sp. and Uronema sp. or salinity-tolerant species such as Prorocentrum sp. The central role of temperature in structuring the co-occurrence network suggests that future global warming could deeply modify plankton communities in shallow coastal zones, affecting whole-food web functioning.

Influences of the hydrophilic components of two anthropogenic dissolved organic nitrogen groups on phytoplankton growth in Jiaozhou Bay, China

Increasing human activities have caused the accumulation of dissolved organic nitrogen (DON) in the ocean, which can alter dominant coastal phytoplankton species. However, insights into DON's effects on marine phytoplankton growth are insufficient compared with those of dissolved inorganic nitrogen (DIN), especially regarding the role of specific DON components. Therefore, in this study, the effects of the hydrophilic (Hic) and low molecular weight (LMW) components of two anthropogenic DON sources on the growth and bioavailable nitrogen uptake of phytoplankton were studied using in situ cultural experiments conducted in Jiaozhou Bay, China. Animal-derived DON from domestic and livestock breeding showed a higher bioavailability compared with that of vegetal DON derived from agricultural sources, with bioavailable component proportions of 76% ± 4% and 66% ± 3%, respectively. Both forms of DON could be absorbed by Skeletonema costatum, stimulating it to become the dominant species in the mesocosm ecosystem; the hydrophilic components of DON contributed approximately 75% of the uptake of DON by S. costatum. The bioavailability of LMW DON was significantly (p < 0.05) lower than that of the Hic DON. The high bioavailability of the Hic DON was mainly associated with its protein-like T1 and T2 components, identified using parallel factor analysis on the excitation-emission-matrix spectra, while the low bioavailability of LMW DON was mainly associated with the humus-like A component. The protein-like T2 components may be directly absorbed by algae, while T1 may be transformed through mineralization and algal absorption. Understanding the impacts of anthropogenic DON and its components on phytoplankton will help improve coastal environmental management. More knowledge of the effect of anthropogenic DON on the phytoplankton community structure in coastal waters should be accumulated in the future.

Assessing the in situ bacterial diversity and composition at anthropogenically active sites using the environmental DNA (eDNA)

In this study, we identified the in situ bacterial groups and their community structure in coastal waters influenced by anthropogenic inputs. The use of environmental DNA (eDNA) and high throughput sequencing (HTS) were employed to derive accurate and reliable information on bacterial abundance. The V3 and V4 hypervariable regions of the 16S rRNA gene were amplified and the sequences were clustered into operational taxonomic units to analyze the site-specific variations in community composition. The percentage composition within the bacterial orders varied significantly among nearshore anthropogenic hotspots and offshore (5 km) samples. The microbial network constructed taking the bacterial abundance as nodes displayed strong positive and negative correlations within the bacterial families. Overall, the use of eDNA coupled with HTS is an incredible means for monitoring and assessing the abundance of bacterial communities and also serves as a biomonitoring tool to understand the degree of anthropogenic contamination in coastal waters.

Particles, protists, and zooplankton in glacier-influenced coastal Svalbard waters

Glacier retreat is an eminent consequence of exacerbating climate change. In the Svalbard archipelago, most of the glaciers are discharging fresh and turbid waters directly to the sea, substantially impacting the coastal Arctic marine ecosystems. This study attempted to characterise the environmental conditions (hydrography, turbidity, marine aggregates) in the glacial-influenced waters and relate them to the abundance and species composition of protists and zooplankton. The study was conducted in the summer of 2016 in two Svalbard fjords (Wijdefjorden and Rijpfjorden) as well as in coastal waters close to glacier terminations on two islands (Nordaustlandet and Edgeøya). Well-recognised gradients in seawater salinity, turbidity, and particle aggregates that spread from glacier fronts towards open waters were not directly associated with the corresponding horizontal gradients in plankton communities. However, the studied environmental parameters explained the high overall variability in protists and zooplankton abundance (70 and 62% of explained variation, respectively). Different vertical distribution patterns and composition of plankton and marine aggregates were observed between fjords compared to open sea island locations suggesting different origin and transport of pelagic organisms and aggregate suspensions among study locations. The results do not support the hypothesis of synchronised horizontal change in environmental and biological components, which indicates that the relation between glacier meltwaters and plankton dynamics is a derivative of complex interactions driven by several physical and ecological processes that occur at different spatiotemporal scales. Nevertheless, this investigation provides new data pertaining to particle and plankton concentrations and structure in coastal waters near glaciers, which is essential for further understanding of the future coastal Arctic ecosystems functioning under rapid glacier retreat caused by climate change.

SPATIAL AND TEMPORAL VARIABILITY OF FISH COMMUNITY BIOMASS IN COASTAL WATERS OF TANGERANG REGENCY, BANTEN

Coastal waters of Tangerang Regency has abundant in fish resource including pelagic, demersal, and reef fish. This study was conducted to assess fish biomass variability and of fish community structure in coastal waters of Tangerang Regency which can be used as a basis in determining alternatives for sustainable fish resource management. This research was conducted in June and August 2013 in three locations i.e., Kronjo, Cituis, and Tanjung Pasir. Primary data collected were fish weight per species. Fish biomass from each locations was obtained using swept area method using trawl. The results showed that Kronjo region contained the highest total average biomass of fish. Temporally, total ave-rage biomass of fish in August was higher than in June for Kronjo and Cituis. Meanwhile, the con-trary occurred in Tanjung Pasir. This conditions occurred due to the high current and high wave in August than in June. In general, biomass of planktivorous was dominant during the study indicating overfishing lead to fishing down the food web in the Coastal waters of Tangerang Regency. Keywords: biomass, coastal waters of Tangerang Regency, spatial and temporal variability, swept area, over fishing.

Remote sensing of the impacts of construction in coastal waters on suspended particulate matter concentration – the case of the Yangtze River delta, China

This study investigates the capability of high-spatial resolution Landsat Thematic Mapper (TM) data to sense and document suspended particulate matter concentration (SPMC) variability resulting from the influence of large structures in coastal waters. Two bridges, located in the coastal waters of the Yangtze River delta, are used as examples. A new SPMC inverse model, relating SPMC to TM optical properties through linear regression in the red and near-infrared bands, is developed. In total, 780 samples and 30 transects taken between 2006 and 2011 were used to compare and contrast SPMC at locations upstream and downstream of the bridges. The comparisons show: (i) within a distance of 0.3 km downstream from the bridges, SPMC mostly increased by 3–60% (8.40–176.29 mg l–1); (ii) when SPMC values upstream were low (<300 mg l–1), the increase in SPMC extended to 3.0–6.5 km downstream; (iii) under conditions of high turbidity (>400 mg l–1) upstream, decreases in SPMC were observed in 0.3–6.5 km downstream. The bridges influenced SPMC by blocking the transport of upstream suspended particulate matter (deposition) and through stirring of the sediments near the base of their piers (resuspension). The results can be generalized to other offshore engineering structures.

Estimation of phytoplankton size structure in coastal waters using simultaneous laser diffraction and fluorescence measurements

This work was partly supported by EHRE (CTM2009-08270) and GRADIENTS (CTM2012-39476) projects. A.J. was supported by a Ramon y Cajal grant (RYC-2010-06898) from the Spanish Ministry of Economy and Competitiveness. S.A. was supported by a Marie Curie International Outgoing Fellowship (GA-302562) within the 7th European Community Framework Programme

The potential of offshore windfarms to act as marine protected areas – A systematic review of current evidence

As offshore windfarm (OWF) construction in the UK is progressing rapidly, monitoring of the economic and ecological effects of these developments is urgently needed. This is to enable both spatial planning and where necessary mitigation in an increasingly crowded marine environment. One approach to mitigation is co-location of OWFs and marine protected areas (MPAs). This systematic review has the objective to inform this co-location proposal and identify areas requiring further research. A limited number of studies addressing marine renewable energy structures and related artificial structures in coastal waters were found. The results of these studies display a change in species assemblages at artificial structures in comparison to naturally occurring habitats. An increase in hard substrata associated species, especially benthic bivalves, crustaceans and reef associated fish and a decrease in algae abundance were the dominant trends. Assemblages associated with complex concrete structures revealed greater similarity to natural hard substrata compared to those around steel structures. To consider marine renewable energy sites, especially large scale OWFs as MPAs, the dissimilar nature of assemblages on the structures themselves to natural communities should be considered. However positive effects were recorded on the abundance of commercially important crustacean species. This suggests potential for incorporation of OWFs as no fishing, or restricted activity zones within a wider MPA to aid fisheries augmentation. The limited available evidence highlights a requirement for significant further research involving long term monitoring at a variety of sites to better inform management options.

Is global ocean sprawl a cause of jellyfish blooms?

Jellyfish (Cnidaria, Scyphozoa) blooms appear to be increasing in both intensity and frequency in many coastal areas worldwide, due to multiple hypothesized anthropogenic stressors. Here, we propose that the proliferation of artificial structures – associated with (1) the exponential growth in shipping, aquaculture, and other coastal industries, and (2) coastal protection (collectively, “ocean sprawl”) – provides habitat for jellyfish polyps and may be an important driver of the global increase in jellyfish blooms. However, the habitat of the benthic polyps that commonly result in coastal jellyfish blooms has remained elusive, limiting our understanding of the drivers of these blooms. Support for the hypothesized role of ocean sprawl in promoting jellyfish blooms is provided by observations and experimental evidence demonstrating that jellyfish larvae settle in large numbers on artificial structures in coastal waters and develop into dense concentrations of jellyfish‐producing polyps.

A Fast Simulation Method for Wave Transformation Processes In Coastal Zones

We develop a numerical model based on the mild-slope equation of water wave propagation over complexbathymetrys, taking into account the combined effects of refraction, diffraction and reflection due to protectionstructures. The numerical method was developed using a split proposed version of the mild-slope equation in ellipticalform and solved by an implicit method in a finite volume mesh, this technique easily allows the modeling of the wavetransformations caused by the protection structures in coastal waters, where industrial and other economic activitiestake place. Study cases controlled have been made and the results match very well with the reference solution. Thecapability and utility of the model for coastal areas are illustrated by its application to the breakwater of the LagunaVerde Nuclear Power Plant (LVNPP) and the protection structure of the Nautical Marine named “Los Ayala”.

Tidal front and its relation to the biological process in coastal water

A tidal front is a unique structure in coastal waters where tidal mixing is dominant during the summer. Various indexes to define tidal fronts and their dynamics have been reviewed in coastal waters where tidal mixing is dominant. The classification of a front in coastal waters is determined by the freshwater inflow, heating/cooling, Ekman transport, and mixing intensity. The strength of mixing plays an important role, dynamically, in creating a tidal front. The hydrography and circulation around a tidal front are crucial in the biological processes leading to the cross-frontal transport of nutrients and phytoplankton blooms. Physical-biological cooperation is necessary to clearly assess the impact of a tidal front on the distribution of phytoplankton and chlorophyll a in the tidal front area.

Relative importance of water column vs zooplankton variables in the determination of late-stage larval fish assemblage structure in coastal waters of a coral reef lagoon

SUMMARY: The relationship between fish larvae and their zooplanktonic prey has not been fully explored for late-stage larvae of coral-reef fish in lagoonal environments. However, compared to most temperate taxa, these larvae are characterized by strong sensory and swimming abilities, which may influence their feeding behaviour in the water column. The present study aims to determine the relative importance of the water column and zooplankton variables for the structure of pre-settlement larval fish assemblages within a single season in three bays of the coral reef lagoon of New Caledonia, southwest Pacific. The structure of larval assemblages was found to be explained better by water column variables in two out of the three bays examined. Zooplankton variables only played a role in one bay out of the three, probably due to the lower variability in the water column variables. Moreover, the relationship between total larval fish abundance and zooplankton density was not significant in any of the three bays. These results suggest that the relationship between late-stage coral-reef fish larvae and their prey: 1) is difficult to detect at small spatial and temporal scales, 2) is probably complex and non-linear, 3) depends on environmental conditions, and 4) probably varies between fish taxa.

Evolutionary Computing for Detection of Retentive Structures in Coastal Waters

The demography of anchovy fishes in the Gulf of Biscay seems to be related to the presence of so- called “retentive” hydrodynamical structures, that keep fish eggs and larvae in a favorable environment. To verify this hypothesis, an automatic detection tool is needed to process a database of thousands of hydrodynamical maps to be compared with biologists observations and fisheries statistics. The results could be used to decide fishing quotas or bans for the sake of preserving the natural resource. We propose two evolutionary schemes, one based on ant systems, the other on induction of genetic programming filters, in order to automatically detect these retentive structures. Our heuristics are shown to be competitive with human experts and are compared to other detection schemes.

Abundance and diversity of fish on mussel farms in New Zealand

Fish are often attracted to floating structures, particularly as juveniles, and in many parts of the world longline mussel farms provide complex, three-dimensional floating structures in coastal waters. There have been few quantitative studies of the assemblages of fish living on and around mussel farms. We sampled fish on mussel farms at three sites in the north of the South Island of New Zealand over a year to characterise the assemblages present and their variability. Predictions of the species likely to be present were made on the basis of their occurrence in the general area, habitat preferences, and occurrence around floating structures in previous studies. The farms differed in their degree of exposure, distance from shore and degree of riverine and oceanic influence. Fish were sampled by underwater visual census, and a remote-operated vehicle, and destructively sampled using an anaesthetic. Abundances of fish on the mussel lines were small (median values up to 1.25 fish m − 1 of line) and were dominated by small, demersal species characteristic of rocky reefs in the area, notably triplefins ( Forsterygion lapillum and Grahamina gymnota, Family Tripterygiidae) and the wrasse Notolabrus celidotus. The abundances and species of fish present differed among sites and among sampling methods (but the small and inconsistent numbers of fish recorded precluded formal statistical testing of differences). Few large, commercially or recreationally important species (demersal or pelagic) were recorded. Triplefins may recruit to the lines at settlement from planktonic larvae and spend their entire lives there. N. celidotus, in contrast, may recruit to stands of macroalgae on nearby rocky reefs and move to farms later. Direct recruitment of N. celidotus may be limited by the low abundances of macroalgae on the mussel lines.