2022 Vol. 44, No. 8
Display Method:
2022, 44(8): 1-10.
doi: 10.12284/hyxb2022132
Abstract:
During the past decades of years, the widespread restrictions and ban on the use of legacy persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) around the world have resulted in gradual decrease in their concentration in various environmental media. As an open sea area, the Northwest Pacific Ocean is far away from the continental area without obvious pollution point source, the ocean currents play an important role in the transportation and diffusion of POPs. In this study, the surface waters (2−5 m) and subsurface waters (150 m) in the Kuroshio area of the Northwest Pacific Ocean were collected and analyzed for dissolved OCPs and PCBs. The results showed that the concentrations of HCHs, DDTs, CHLs and PCBs in the surface waters ranged from 30.7 pg/L to 68.8 pg/L, 6.16 pg/L to 23.8 pg/L, 1.07 pg/L to 5.75 pg/L and 49.8 pg/L to 124 pg/L, respectively; the concentrations in the subsurface waters ranged from 27.3 pg/L to 68.4 pg/L, 7.06 pg/L to 14.1 pg/L, 0.518 pg/L to 10.1 pg/L and 34.1 pg/L to 68.4 pg/L, respectively. The concentration levels of OCPs in different water bodies were comparable, which may be related to the huge water body and internal homogeneity of the Kuroshio. The ratios of the various isomers of HCHs indicated that the sea area was dominated by lindane input, while the ratio of DDTs and CHLs showed that the DDTs and CHLs in the waters of the sea area were mainly derived from the residues of legacy. PCBs were dominated by tri-PCBs and tetra-PCBs, which consistented with the use of PCBs in East Asia. The large volume and uniform internal distribution of Kuroshio water mass have an important impact on the vertical distribution of pollutants, that is, the concentration and composition of OCPs in water at different depths are similar. At the same time, Kuroshio brings high temperature and high nutrient salt water masses, forming potential risks to the enrichment of pollutants in the marine organisms.
During the past decades of years, the widespread restrictions and ban on the use of legacy persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) around the world have resulted in gradual decrease in their concentration in various environmental media. As an open sea area, the Northwest Pacific Ocean is far away from the continental area without obvious pollution point source, the ocean currents play an important role in the transportation and diffusion of POPs. In this study, the surface waters (2−5 m) and subsurface waters (150 m) in the Kuroshio area of the Northwest Pacific Ocean were collected and analyzed for dissolved OCPs and PCBs. The results showed that the concentrations of HCHs, DDTs, CHLs and PCBs in the surface waters ranged from 30.7 pg/L to 68.8 pg/L, 6.16 pg/L to 23.8 pg/L, 1.07 pg/L to 5.75 pg/L and 49.8 pg/L to 124 pg/L, respectively; the concentrations in the subsurface waters ranged from 27.3 pg/L to 68.4 pg/L, 7.06 pg/L to 14.1 pg/L, 0.518 pg/L to 10.1 pg/L and 34.1 pg/L to 68.4 pg/L, respectively. The concentration levels of OCPs in different water bodies were comparable, which may be related to the huge water body and internal homogeneity of the Kuroshio. The ratios of the various isomers of HCHs indicated that the sea area was dominated by lindane input, while the ratio of DDTs and CHLs showed that the DDTs and CHLs in the waters of the sea area were mainly derived from the residues of legacy. PCBs were dominated by tri-PCBs and tetra-PCBs, which consistented with the use of PCBs in East Asia. The large volume and uniform internal distribution of Kuroshio water mass have an important impact on the vertical distribution of pollutants, that is, the concentration and composition of OCPs in water at different depths are similar. At the same time, Kuroshio brings high temperature and high nutrient salt water masses, forming potential risks to the enrichment of pollutants in the marine organisms.
2022, 44(8): 11-22.
doi: 10.12284/hyxb2022162
Abstract:
In order to understand the distribution characteristics, relationships and diffusion fluxes of nutrients and metal elements across the sediment-water interface, we investigated the vertical profiles of nutrients and metal elements through the diffusive gradient in thin-films (DGT) technology in Shenzhen Bay (SZB) and Maozhou River (MZR). The two-dimensional high-resolution available sulfur (DGT-labile S) distributions were also synchronously measured. The results showed that the mean concentrations of\begin{document}${\rm{NH}}_4^+ $\end{document} ![]()
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In order to understand the distribution characteristics, relationships and diffusion fluxes of nutrients and metal elements across the sediment-water interface, we investigated the vertical profiles of nutrients and metal elements through the diffusive gradient in thin-films (DGT) technology in Shenzhen Bay (SZB) and Maozhou River (MZR). The two-dimensional high-resolution available sulfur (DGT-labile S) distributions were also synchronously measured. The results showed that the mean concentrations of
2022, 44(8): 23-30.
doi: 10.12284/hyxb2022128
Abstract:
The outbreak of crown-of-thorns starfish has seriously threatened the ecological health of coral reefs, and the supplement of nutrients in seawater may be a key factor leading to the outbreak of starfish. Sandy sediments play a key role in regulating the nutrient concentration and structure in coral reefs. Therefore, crown-of-thorns starfish and sandy sediments were incubated using flow-through reactor, to analyze the effects of crown-of-thorns starfish excretion and dead body degradation on nutrient concentration and structure, and to explore the role of sandy sediments under activities of crown-of-thorns starfish. The results were as followed: (1) crown-of-thorns starfish excreted dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) at rates of (83.55±4.74) μmol/(ind.·h) and (2.53±0.03) μmol/(ind.·h), respectively, which maight provide nutritional conditions for the continuous outbreak of starfish; (2) sandy sediments could regulate the nutrient concentration changed by the excretion of starfish, about 70.7% of DIN and 91.4% of DIP were trapped in the sediments, but the increase of DIN/DIP caused by nutrient exchange at the sediment-seawater interface may be detrimental to coral growth; (3) the degradation of starfish organisms could promote the release of nutrients at the sediment-seawater interface. Based on the density of starfish, the released nutrients could cause the concentrations of DIN and DIP in the overlying water to increase by 0.32 μmol/L and 0.01 μmol/L, respectively, which maight promote the rapid growth of macroalgae and hinder the self-restoration of corals.
The outbreak of crown-of-thorns starfish has seriously threatened the ecological health of coral reefs, and the supplement of nutrients in seawater may be a key factor leading to the outbreak of starfish. Sandy sediments play a key role in regulating the nutrient concentration and structure in coral reefs. Therefore, crown-of-thorns starfish and sandy sediments were incubated using flow-through reactor, to analyze the effects of crown-of-thorns starfish excretion and dead body degradation on nutrient concentration and structure, and to explore the role of sandy sediments under activities of crown-of-thorns starfish. The results were as followed: (1) crown-of-thorns starfish excreted dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) at rates of (83.55±4.74) μmol/(ind.·h) and (2.53±0.03) μmol/(ind.·h), respectively, which maight provide nutritional conditions for the continuous outbreak of starfish; (2) sandy sediments could regulate the nutrient concentration changed by the excretion of starfish, about 70.7% of DIN and 91.4% of DIP were trapped in the sediments, but the increase of DIN/DIP caused by nutrient exchange at the sediment-seawater interface may be detrimental to coral growth; (3) the degradation of starfish organisms could promote the release of nutrients at the sediment-seawater interface. Based on the density of starfish, the released nutrients could cause the concentrations of DIN and DIP in the overlying water to increase by 0.32 μmol/L and 0.01 μmol/L, respectively, which maight promote the rapid growth of macroalgae and hinder the self-restoration of corals.
2022, 44(8): 31-41.
doi: 10.12284/hyxb2022136
Abstract:
The temporal and spatial variation characteristics and influencing factors of euphotic depth and primary productivity in the Zhanjiang Bay were studied by applying voyage data of four seasons from 2016 to 2017．The results showed that the average value of euphotic depth was (6.95±3.17) m, and the spatial variations were more obvious than the seasonal variations. There was a significant positive correlation between Kd (PAR) and turbidity, as the R2 of established linear regression model was 0.73 (p<0.01), indicating that suspended particles on euphotic depth was the dominant attenuation factor in the Zhanjiang Bay. The average value of primary productivity obtained by VGPM model was (639.53±427.95) mg/(m2·d), and its temporal and spatial characteristics were basically consistent with euphotic depth, which mean euphotic depth explained the temporal and spatial distribution pattern of primary productivity better than chlorophyll a concentration.
The temporal and spatial variation characteristics and influencing factors of euphotic depth and primary productivity in the Zhanjiang Bay were studied by applying voyage data of four seasons from 2016 to 2017．The results showed that the average value of euphotic depth was (6.95±3.17) m, and the spatial variations were more obvious than the seasonal variations. There was a significant positive correlation between Kd (PAR) and turbidity, as the R2 of established linear regression model was 0.73 (p<0.01), indicating that suspended particles on euphotic depth was the dominant attenuation factor in the Zhanjiang Bay. The average value of primary productivity obtained by VGPM model was (639.53±427.95) mg/(m2·d), and its temporal and spatial characteristics were basically consistent with euphotic depth, which mean euphotic depth explained the temporal and spatial distribution pattern of primary productivity better than chlorophyll a concentration.
2022, 44(8): 42-50.
doi: 10.12284/hyxb2022174
Abstract:
In order to improve the study of the interaction between internal solitary waves and submarine slope sediments, the stage of continued motion on the slope after internal solitary waves fragmentation is focused on in this paper, and conducts physical simulation experiments to analyse the changes in earth pressure and super-pore water pressure in response to the slope to reveal the process of internal wave action. The results show that the sediment particles on the slope are resuspended under the combined action of vortex and seepage caused by the internal solitary waves fragmentation, and the change in slope gradient does not change the dominant dynamic role of the sediment in generating the dynamic response; the amplitude of the internal solitary waves affect the ratio between vortex and seepage, i.e. the vortex is dominant under small amplitude conditions and the seepage is dominant under large amplitude conditions; the fragmented fluid forms a new dynamic role when it rushes out along the slope. The dynamic response of the sediment to the new vorticity is influenced by the slope of the slope. The results of this paper are useful for the study of internal solitary waves resuspension transporting seafloor sediments and modifying seafloor topography.
In order to improve the study of the interaction between internal solitary waves and submarine slope sediments, the stage of continued motion on the slope after internal solitary waves fragmentation is focused on in this paper, and conducts physical simulation experiments to analyse the changes in earth pressure and super-pore water pressure in response to the slope to reveal the process of internal wave action. The results show that the sediment particles on the slope are resuspended under the combined action of vortex and seepage caused by the internal solitary waves fragmentation, and the change in slope gradient does not change the dominant dynamic role of the sediment in generating the dynamic response; the amplitude of the internal solitary waves affect the ratio between vortex and seepage, i.e. the vortex is dominant under small amplitude conditions and the seepage is dominant under large amplitude conditions; the fragmented fluid forms a new dynamic role when it rushes out along the slope. The dynamic response of the sediment to the new vorticity is influenced by the slope of the slope. The results of this paper are useful for the study of internal solitary waves resuspension transporting seafloor sediments and modifying seafloor topography.
2022, 44(8): 51-65.
doi: 10.12284/hyxb2022150
Abstract:
The applicability of environmental DNA (eDNA) metabarcoding fragments to relative fish species had not been compared. There was a risk of “species loss” in diversity surveys. In order to screen out the best fragments, we compared the resolution rate differences of 15 eDNA metabarcoding fragments in 106 genera (a total of 935 species). The results were as follows: (1) the protein-coding gene (COI, fragment 15) had the highest resolution rate, but the universality of its corresponding primer pairs was the worst; the overall mean distance based on primer pair sequence of fragment 09, fragment 11, fragment 07, fragment 03 and fragment 12 were obviously large, suggesting their eDNA amplification efficiency were possibly low. (2) The resolution rates were significantly affected by the length of fragments, and the fragment 05, fragment 06, fragment 01, fragment 02 and fragment 13 of ribosomal genes had a higher resolution rate except fragment 15. (3) Non-metric multidimensional scaling analysis (NMDS) showed that there were great differences among different genes and different fragments belonging to the same gene. Therefore, the combination application of multi-fragment and multi-gene should be considered; besides, fragment 01 and fragment 02, and fragment 05 and fragment 06 were close to each other in the NMDS plot. They function of fish resolution were overlapped. (4) Species groups affected the resolution results, and eDNA studies stilled need to develop fragments with higher resolution rates. Based on the resolution rate of relative species, the universality of primer pairs and NMDS analysis, this study recommended fragment 01 (Mifish-U) for 2×150 bp sequencing platform and fragment 05 (Ac12S) for 2×250 bp sequencing platform, supplemented by fragment 13 (Vert-16S-eDNA) to investigate the diversity of relative fish. This study provided some support for improving the accuracy of fish eDNA survey results.
The applicability of environmental DNA (eDNA) metabarcoding fragments to relative fish species had not been compared. There was a risk of “species loss” in diversity surveys. In order to screen out the best fragments, we compared the resolution rate differences of 15 eDNA metabarcoding fragments in 106 genera (a total of 935 species). The results were as follows: (1) the protein-coding gene (COI, fragment 15) had the highest resolution rate, but the universality of its corresponding primer pairs was the worst; the overall mean distance based on primer pair sequence of fragment 09, fragment 11, fragment 07, fragment 03 and fragment 12 were obviously large, suggesting their eDNA amplification efficiency were possibly low. (2) The resolution rates were significantly affected by the length of fragments, and the fragment 05, fragment 06, fragment 01, fragment 02 and fragment 13 of ribosomal genes had a higher resolution rate except fragment 15. (3) Non-metric multidimensional scaling analysis (NMDS) showed that there were great differences among different genes and different fragments belonging to the same gene. Therefore, the combination application of multi-fragment and multi-gene should be considered; besides, fragment 01 and fragment 02, and fragment 05 and fragment 06 were close to each other in the NMDS plot. They function of fish resolution were overlapped. (4) Species groups affected the resolution results, and eDNA studies stilled need to develop fragments with higher resolution rates. Based on the resolution rate of relative species, the universality of primer pairs and NMDS analysis, this study recommended fragment 01 (Mifish-U) for 2×150 bp sequencing platform and fragment 05 (Ac12S) for 2×250 bp sequencing platform, supplemented by fragment 13 (Vert-16S-eDNA) to investigate the diversity of relative fish. This study provided some support for improving the accuracy of fish eDNA survey results.
2022, 44(8): 66-77.
doi: 10.12284/hyxb2022144
Abstract:
To explore the differences in the composition, diversity, and functions of bacterial communities in tissues from two-year old and healthy Crassostrea sikamea, Crassostrea angulata and Crassostrea gigas, the bacterial community structures and functional potentials among three oysters by combining the Illumina MiSeq high-throughput sequencing technology and phylogenetic investigation of communities by reconstruction of unobserved states 2 (PICRUSt2) was compared in this paper. The results showed that a total of 6 020 OTUs were identified in the five tissues from the three oysters, among which the numbers of shared OTUs accounted for 42.4% of total OTUs. The γ-proteobacteria, α-proteobacteria, Tenericutes and Firmicutes were dominant in five tissues of three oysters. The relative abundance of Vibrio genus was significantly higher in the gill, mantle, hepatopancreas and hemolymph tissues of C. sikamea than in the five tissues of C. angulata and C. gigas. Compared to other tissues, the relative abundance of Vibrio genus was the highest in the mantle of C. sikamea, the gonad of C. angulata and the hemolymph of C. gigas, but was lowest in the hepatopancreas of all three oysters. The diversity of bacterial communities was different among the five tissues of three oysters. Compared to other tissues, the bacterial community α-diversity was higher in the gill of C. sikamea, the mantle of C. angulata and the hemolymph of C. gigas, respectively, but was lowest in the hemolymph of C. sikamea, the gonad of C. angulata and the hepatopancreas of C. gigas. Regardless of tissue types, the bacterial community structures differed significantly (r=0.661, p<0.001) among the three oysters. Additionally, the abundances of bacterial-mediated functional pathways involved in the energy metabolism were significantly higher in the hepatopancreas of C. sikamea, the gill of C. angulata and the hemolymph of C. gigas than that in other tissues of corresponding oysters. Our findings suggested that the structure and composition of bacterial communities were different among five tissues of C. sikamea, C. angulata and C. gigas, and the bacterial-mediated functional potentials ware affected by oyster species and tissue types.
To explore the differences in the composition, diversity, and functions of bacterial communities in tissues from two-year old and healthy Crassostrea sikamea, Crassostrea angulata and Crassostrea gigas, the bacterial community structures and functional potentials among three oysters by combining the Illumina MiSeq high-throughput sequencing technology and phylogenetic investigation of communities by reconstruction of unobserved states 2 (PICRUSt2) was compared in this paper. The results showed that a total of 6 020 OTUs were identified in the five tissues from the three oysters, among which the numbers of shared OTUs accounted for 42.4% of total OTUs. The γ-proteobacteria, α-proteobacteria, Tenericutes and Firmicutes were dominant in five tissues of three oysters. The relative abundance of Vibrio genus was significantly higher in the gill, mantle, hepatopancreas and hemolymph tissues of C. sikamea than in the five tissues of C. angulata and C. gigas. Compared to other tissues, the relative abundance of Vibrio genus was the highest in the mantle of C. sikamea, the gonad of C. angulata and the hemolymph of C. gigas, but was lowest in the hepatopancreas of all three oysters. The diversity of bacterial communities was different among the five tissues of three oysters. Compared to other tissues, the bacterial community α-diversity was higher in the gill of C. sikamea, the mantle of C. angulata and the hemolymph of C. gigas, respectively, but was lowest in the hemolymph of C. sikamea, the gonad of C. angulata and the hepatopancreas of C. gigas. Regardless of tissue types, the bacterial community structures differed significantly (r=0.661, p<0.001) among the three oysters. Additionally, the abundances of bacterial-mediated functional pathways involved in the energy metabolism were significantly higher in the hepatopancreas of C. sikamea, the gill of C. angulata and the hemolymph of C. gigas than that in other tissues of corresponding oysters. Our findings suggested that the structure and composition of bacterial communities were different among five tissues of C. sikamea, C. angulata and C. gigas, and the bacterial-mediated functional potentials ware affected by oyster species and tissue types.
2022, 44(8): 78-86.
doi: 10.12284/hyxb2022154
Abstract:
As a junction between land and sea, the intertidal zone is vulnerable to oil pollution from the ocean, and the degradation process of various types of petroleum hydrocarbons entering the sediment is still unclear. There have been many studies on aerobic microbial hydrocarbon degradation, but little has been reported on anaerobic hydrocarbon degradation in the offshore intertidal environment. In this study, anaerobic enrichment culture was conducted on deep intertidal sediment samples from Qingdao Nüdao Bay with mixed hydrocarbons (medium and long chain alkanes and polycyclic aromatic hydrocarbons) as carbon source and sulfate as electron acceptor. The bacterial diversity of the enriched flora indicated that the dominant flora changed to Desulfosarcinaceae, Desulfobacteraceae and other sulfate-reducing bacteria with petroleum hydrocarbon degradation potential under the effect of mixed hydrocarbons as carbon source. An anaerobic hydrocarbon-degrading strain ND17 was obtained by isolation and purification, with 99.93% similarity to the 16S rRNA gene sequence of Desulfovibrio subterraneus HN2T, the model species of Desulfovibrio subterraneus genus. Further experiments showed that strain ND17 could degrade eicosanoids and phenanthrene up to 53.9% and 35.7%, respectively, under anaerobic conditions. This is the first study on the degradation of petroleum hydrocarbons under anaerobic conditions by a single bacterium of the genus Desulfovibrio. As a widely distributed bacterium in anaerobic environments, this study supports further understanding of its remediation potential in marine petroleum-contaminated environments.
As a junction between land and sea, the intertidal zone is vulnerable to oil pollution from the ocean, and the degradation process of various types of petroleum hydrocarbons entering the sediment is still unclear. There have been many studies on aerobic microbial hydrocarbon degradation, but little has been reported on anaerobic hydrocarbon degradation in the offshore intertidal environment. In this study, anaerobic enrichment culture was conducted on deep intertidal sediment samples from Qingdao Nüdao Bay with mixed hydrocarbons (medium and long chain alkanes and polycyclic aromatic hydrocarbons) as carbon source and sulfate as electron acceptor. The bacterial diversity of the enriched flora indicated that the dominant flora changed to Desulfosarcinaceae, Desulfobacteraceae and other sulfate-reducing bacteria with petroleum hydrocarbon degradation potential under the effect of mixed hydrocarbons as carbon source. An anaerobic hydrocarbon-degrading strain ND17 was obtained by isolation and purification, with 99.93% similarity to the 16S rRNA gene sequence of Desulfovibrio subterraneus HN2T, the model species of Desulfovibrio subterraneus genus. Further experiments showed that strain ND17 could degrade eicosanoids and phenanthrene up to 53.9% and 35.7%, respectively, under anaerobic conditions. This is the first study on the degradation of petroleum hydrocarbons under anaerobic conditions by a single bacterium of the genus Desulfovibrio. As a widely distributed bacterium in anaerobic environments, this study supports further understanding of its remediation potential in marine petroleum-contaminated environments.
2022, 44(8): 87-96.
doi: 10.12284/hyxb2022126
Abstract:
In recent years, the rising of sea surface temperature caused by global warming resulted in frequently large-scale coral bleaching events, which have seriously damaged the health of coral reef ecosystems. In order to reveal the influence of bleaching events on the thermal tolerance of Porites lutea and further explore the physiological response of P. lutea in high temperature, comparative study was carried out on high-stress experiment on P. lutea before and after high temperature bleaching events at Weizhou Island, Guangxi in summer 2020. Coral’s physiological and biochemical indexes were also analyzed. The results showed that: (1) the response pattern of the two groups to high temperature stress was that the contraction of coral tentacles, the density of zooxanthellae, the maximum quantum efficiency of Photosystem II (Fv/Fm) and chlorophyll a content decreased significantly, antioxidant (superoxide dismutase, catalase, glutathione) and ammonium assimilase (glutamine synthase) activities (content) increased and then decreased; (2) the physiological indexes showed better performance and its antioxidant and ammonium assimilation enzyme kept high activity and sensitive response in the after high temperature bleaching events group. It means that the P. lutea in the Weizhou Island can improve its thermal tolerance by increasing the activities of antioxidant and ammonium assimilation enzyme after high temperature bleaching events which is one of the strategies to cope with global warming. This study also revealed the response pattern of Weizhou Island’s P. lutea to extreme high temperatures, providing theoretical support for coral reef protection and ecological restoration.
In recent years, the rising of sea surface temperature caused by global warming resulted in frequently large-scale coral bleaching events, which have seriously damaged the health of coral reef ecosystems. In order to reveal the influence of bleaching events on the thermal tolerance of Porites lutea and further explore the physiological response of P. lutea in high temperature, comparative study was carried out on high-stress experiment on P. lutea before and after high temperature bleaching events at Weizhou Island, Guangxi in summer 2020. Coral’s physiological and biochemical indexes were also analyzed. The results showed that: (1) the response pattern of the two groups to high temperature stress was that the contraction of coral tentacles, the density of zooxanthellae, the maximum quantum efficiency of Photosystem II (Fv/Fm) and chlorophyll a content decreased significantly, antioxidant (superoxide dismutase, catalase, glutathione) and ammonium assimilase (glutamine synthase) activities (content) increased and then decreased; (2) the physiological indexes showed better performance and its antioxidant and ammonium assimilation enzyme kept high activity and sensitive response in the after high temperature bleaching events group. It means that the P. lutea in the Weizhou Island can improve its thermal tolerance by increasing the activities of antioxidant and ammonium assimilation enzyme after high temperature bleaching events which is one of the strategies to cope with global warming. This study also revealed the response pattern of Weizhou Island’s P. lutea to extreme high temperatures, providing theoretical support for coral reef protection and ecological restoration.
2022, 44(8): 97-109.
doi: 10.12284/hyxb2022160
Abstract:
Seagrass bed is one of the three typical coastal ecosystems, which plays an important role in environmental improvement, resource conservation, and mitigation of environment degradation caused by natural disasters. It is also important as a global carbon stock. In August 2016, a field survey was conducted in the sea area of Mashanli of Rongcheng. A seagrass bed with an area of 58.26 hm2 was found, consisting of Phyllospadix iwatensis and Zostera caespitosa meadows. The P. iwatensis meadow was composed of two belt regions south and north of the bed, occupying an area of 54.50 hm2 and accounting for 93.5% of the seagrass bed. The P. iwatensis shoot density was (368.0±18.2) shoots/m2 and the biomass was (297.0±41.5) g/m2. While the Z. caespitosa generally formed dense patches within the P. iwatensis meadows, and occupied an area of 3.76 hm2, accounting for 6.5% of the seagrass bed. The shoot density of Z. caespitosa was (691.2±17.1) shoots/m2, and the biomass was (534.0±70.7) g/m2. The water depth in the seagrass bed was (2.8±0.3) m, and the seabed was mainly rocky, with some sediments covering on the rocky beds. The growth of the seagrasses showed significant spatial variation, which was positively correlated with the water temperature, and negatively correlated with water depth and terrestrial pollutants. By comparing with historical data, it was found that the degradation of seagrass beds in Mashanli sea area was severe. Anthropogenic activities are the main causes of seagrass degradation, including fishing and aquaculture activities, as well as the pollution of land-based sources. Therefore, it is suggested that rationally planning the scale and density of aquaculture in surrounding area, strengthening the control of terrestrial pollutants, and carrying out ecological restoration projects of seagrass beds will promote the effective protection and scientific management of seagrass beds in temperate zone.
Seagrass bed is one of the three typical coastal ecosystems, which plays an important role in environmental improvement, resource conservation, and mitigation of environment degradation caused by natural disasters. It is also important as a global carbon stock. In August 2016, a field survey was conducted in the sea area of Mashanli of Rongcheng. A seagrass bed with an area of 58.26 hm2 was found, consisting of Phyllospadix iwatensis and Zostera caespitosa meadows. The P. iwatensis meadow was composed of two belt regions south and north of the bed, occupying an area of 54.50 hm2 and accounting for 93.5% of the seagrass bed. The P. iwatensis shoot density was (368.0±18.2) shoots/m2 and the biomass was (297.0±41.5) g/m2. While the Z. caespitosa generally formed dense patches within the P. iwatensis meadows, and occupied an area of 3.76 hm2, accounting for 6.5% of the seagrass bed. The shoot density of Z. caespitosa was (691.2±17.1) shoots/m2, and the biomass was (534.0±70.7) g/m2. The water depth in the seagrass bed was (2.8±0.3) m, and the seabed was mainly rocky, with some sediments covering on the rocky beds. The growth of the seagrasses showed significant spatial variation, which was positively correlated with the water temperature, and negatively correlated with water depth and terrestrial pollutants. By comparing with historical data, it was found that the degradation of seagrass beds in Mashanli sea area was severe. Anthropogenic activities are the main causes of seagrass degradation, including fishing and aquaculture activities, as well as the pollution of land-based sources. Therefore, it is suggested that rationally planning the scale and density of aquaculture in surrounding area, strengthening the control of terrestrial pollutants, and carrying out ecological restoration projects of seagrass beds will promote the effective protection and scientific management of seagrass beds in temperate zone.
2022, 44(8): 110-122.
doi: 10.12284/hyxb2022130
Abstract:
Long-term changes of phytoplankton community structure with relation to environmental factors in the Daya Bay in summer between 1999 and 2017 were investigated. The results showed that seawater temperature showed a significant decreasing trend, while salinity increased significantly. During the period 2008 to 2017, the dissolved inorganic nitrogen (DIN) annual mean concentration increased by 72.73% relative to 1999 to 2007. Trend of phytoplankton species number and dominant species were not significant, Pseudonitzschia delicatissima was overwhelmingly dominant followed by Skeletonema costatum. The abundance of total phytoplankton, diatoms, dinoflagellates, and some dominant species (Pseudonitzschia delicatissima, Skeletonema costatum, Ceratium furca) significantly increased during the study period in the Daya Bay. Species diversity and evenness indices showed downward trends. The analysis showed that the increased DIN concentration induced by human activities and seawater temperature and salinity changes were the main reasons for long-term changes of phytoplankton community structure in the Daya Bay in summer.
Long-term changes of phytoplankton community structure with relation to environmental factors in the Daya Bay in summer between 1999 and 2017 were investigated. The results showed that seawater temperature showed a significant decreasing trend, while salinity increased significantly. During the period 2008 to 2017, the dissolved inorganic nitrogen (DIN) annual mean concentration increased by 72.73% relative to 1999 to 2007. Trend of phytoplankton species number and dominant species were not significant, Pseudonitzschia delicatissima was overwhelmingly dominant followed by Skeletonema costatum. The abundance of total phytoplankton, diatoms, dinoflagellates, and some dominant species (Pseudonitzschia delicatissima, Skeletonema costatum, Ceratium furca) significantly increased during the study period in the Daya Bay. Species diversity and evenness indices showed downward trends. The analysis showed that the increased DIN concentration induced by human activities and seawater temperature and salinity changes were the main reasons for long-term changes of phytoplankton community structure in the Daya Bay in summer.
2022, 44(8): 123-132.
doi: 10.12284/hyxb2022148
Abstract:
During June 10 to 14, 2018, the extinction of Gymnodinium catenatum bloom in the Quanzhou Bay was studied in this paper. In the field investigation, a total of 4 stations were set up to monitor the marine environment factors and phytoplankton within 6 times. Combined with the investigation of dinoflagellate cysts in the Quanzhou Bay, the relationship of dinoflagellate cysts and the evolution of bloom was explored. The results showed that when the bloom occurred, the sea state was good and the water temperature and salinity were 27.1℃ to 28.2℃ and 29.7 to 31.4 respectively. The concentration of PO4-P and inorganic nitrogen were between below detectable limit to 0.0454 mg/L and 0.050 mg/L to 0.281 mg/L respectively. There was no significant correlation between the density of bloom biology and nutrients. The strong winds and waves were the important factors for the extinction of bloom. One hundred species belonging to 48 genera and 3 phyla of phytoplankton were identified in the extinction of bloom, and Bacillariophyta was the most phylum. The community structure of phytoplankton changed during the extinction of bloom, Gymnodinium catenatum was the absolute dominant, the maximum density of which reached （7.02±0.11）×106 cells/L. In the declination of the bloom, Skeletonema costatum and Chaetoceros curvisetus dominated, and the number of phytoplankton species increased significantly. At the same time, 37 species of dinoflagellate cysts in 5 groups and 1 undetermined species were identified in the Quanzhou Bay, and the average abundance of which was 574 cysts/g, mainly dominated by heterotrophic dinoflagellate cysts. The resting cysts played an important role in the evolution of bloom. They occurred when the bloom dissipated and decreased with time. However, they still could germinate and had the potential to re-outbreak and form bloom, which should raise concern.
During June 10 to 14, 2018, the extinction of Gymnodinium catenatum bloom in the Quanzhou Bay was studied in this paper. In the field investigation, a total of 4 stations were set up to monitor the marine environment factors and phytoplankton within 6 times. Combined with the investigation of dinoflagellate cysts in the Quanzhou Bay, the relationship of dinoflagellate cysts and the evolution of bloom was explored. The results showed that when the bloom occurred, the sea state was good and the water temperature and salinity were 27.1℃ to 28.2℃ and 29.7 to 31.4 respectively. The concentration of PO4-P and inorganic nitrogen were between below detectable limit to 0.0454 mg/L and 0.050 mg/L to 0.281 mg/L respectively. There was no significant correlation between the density of bloom biology and nutrients. The strong winds and waves were the important factors for the extinction of bloom. One hundred species belonging to 48 genera and 3 phyla of phytoplankton were identified in the extinction of bloom, and Bacillariophyta was the most phylum. The community structure of phytoplankton changed during the extinction of bloom, Gymnodinium catenatum was the absolute dominant, the maximum density of which reached （7.02±0.11）×106 cells/L. In the declination of the bloom, Skeletonema costatum and Chaetoceros curvisetus dominated, and the number of phytoplankton species increased significantly. At the same time, 37 species of dinoflagellate cysts in 5 groups and 1 undetermined species were identified in the Quanzhou Bay, and the average abundance of which was 574 cysts/g, mainly dominated by heterotrophic dinoflagellate cysts. The resting cysts played an important role in the evolution of bloom. They occurred when the bloom dissipated and decreased with time. However, they still could germinate and had the potential to re-outbreak and form bloom, which should raise concern.
2022, 44(8): 133-141.
doi: 10.12284/hyxb2022156
Abstract:
Blooms of red Noctiluca scintillans is an annual eco-disaster in coastal waters of China, but the mechanism of outbreak of N. scintillans is still unclear. To explore the role of nutrient conditions in the formation of N. scintillans blooms, the population growth of N. scintillans feeding several diet algae, including common diet algae and local diatoms, were investigated under standing water, mixing water and different inorganic nutrient levels. Results showed that there were significant differences in population growth of N. scintillans under different diets. Population growth of N. scintillans was fastest in Platymonas subcordiformis treatment, with growth rate of (0.151±0.001) d−1. N. scintillans growth significantly increased in mixing water when feeding on some diet algae. The population growth rate of N. scintillans in Thalassiosira minima treatment was (0.136±0.001) d−1, which was much higher than growth rate of N. scintillans in other algae treatment except in P. subcordiformis treatment. Growth rate and maximum population of N. scintillans cultured with P. subcordiformis firstly increased and then decreased with increasing inorganic nutrient levels, and results suggested that its growth fitted the Boltzmann model, with parameters were highly related to inorganic nutrients. Results indicated that proliferation of local diet algae, such as Thalassiosira species, leading by nutrients input in spring, combined with mixing of seawater, might play an important role in the formation of massive N. scintillans bloom in Pingtan coastal waters.
Blooms of red Noctiluca scintillans is an annual eco-disaster in coastal waters of China, but the mechanism of outbreak of N. scintillans is still unclear. To explore the role of nutrient conditions in the formation of N. scintillans blooms, the population growth of N. scintillans feeding several diet algae, including common diet algae and local diatoms, were investigated under standing water, mixing water and different inorganic nutrient levels. Results showed that there were significant differences in population growth of N. scintillans under different diets. Population growth of N. scintillans was fastest in Platymonas subcordiformis treatment, with growth rate of (0.151±0.001) d−1. N. scintillans growth significantly increased in mixing water when feeding on some diet algae. The population growth rate of N. scintillans in Thalassiosira minima treatment was (0.136±0.001) d−1, which was much higher than growth rate of N. scintillans in other algae treatment except in P. subcordiformis treatment. Growth rate and maximum population of N. scintillans cultured with P. subcordiformis firstly increased and then decreased with increasing inorganic nutrient levels, and results suggested that its growth fitted the Boltzmann model, with parameters were highly related to inorganic nutrients. Results indicated that proliferation of local diet algae, such as Thalassiosira species, leading by nutrients input in spring, combined with mixing of seawater, might play an important role in the formation of massive N. scintillans bloom in Pingtan coastal waters.
2022, 44(8): 142-150.
doi: 10.12284/hyxb2022142
Abstract:
In order to examine the regulatory mechanism of size structure of algal blooms in eutrophic estuarine waters, we used river water, sea water and their mixed water in Zhujiang River Estuary during dry season and conducted incubation experiments to examine changes of nutrients and chlorophyll a (Chl a) concentrations. Algal growth rate (μ) and microzooplankton grazing rate (m) were estimated by dilution experiments to examine the effects of bottom-up (nutrients stimulation) and top-down control (microzooplankton grazing) on size structure of algal blooms. We found that nutrient additions increased the peak of Chl a concentration, and phytoplankton community dominance changed from picophytoplankton and nanophytoplankton to microphytoplankton. Generally, μ kept high in the first 2 to 3 days and then declined (1.13±0.37) per day in nutrient added river water; μ kept increasing (1.06±0.16) per day in nutrient added sea water and slightly fluctuated (0.58±0.14) per day in nutrient added mixed water with microphytoplankton having the highest μ. In contrast, m increased in the first 2 days or 3 days and then decreased, and there were no size differences in all treatments. The microzooplankton grazing vs algal growth (m/μ) increased from microphytoplankton, nanophytoplankton, to picophytoplankton, indicating that larger size phytoplankton were under less top-down control. In addition, m/μ increased as daily algal specific growth rate decreased, indicating that bottom-up control played a stimulating role at early stage, and the top-down control played a more important role in the late stage of algal blooms. This study suggests that eutrophication can make a difference in both the magnitudes and size structure of algal blooms in estuarine waters.
In order to examine the regulatory mechanism of size structure of algal blooms in eutrophic estuarine waters, we used river water, sea water and their mixed water in Zhujiang River Estuary during dry season and conducted incubation experiments to examine changes of nutrients and chlorophyll a (Chl a) concentrations. Algal growth rate (μ) and microzooplankton grazing rate (m) were estimated by dilution experiments to examine the effects of bottom-up (nutrients stimulation) and top-down control (microzooplankton grazing) on size structure of algal blooms. We found that nutrient additions increased the peak of Chl a concentration, and phytoplankton community dominance changed from picophytoplankton and nanophytoplankton to microphytoplankton. Generally, μ kept high in the first 2 to 3 days and then declined (1.13±0.37) per day in nutrient added river water; μ kept increasing (1.06±0.16) per day in nutrient added sea water and slightly fluctuated (0.58±0.14) per day in nutrient added mixed water with microphytoplankton having the highest μ. In contrast, m increased in the first 2 days or 3 days and then decreased, and there were no size differences in all treatments. The microzooplankton grazing vs algal growth (m/μ) increased from microphytoplankton, nanophytoplankton, to picophytoplankton, indicating that larger size phytoplankton were under less top-down control. In addition, m/μ increased as daily algal specific growth rate decreased, indicating that bottom-up control played a stimulating role at early stage, and the top-down control played a more important role in the late stage of algal blooms. This study suggests that eutrophication can make a difference in both the magnitudes and size structure of algal blooms in estuarine waters.
2022, 44(8): 151-168.
doi: 10.12284/hyxb2022138
Abstract:
Estimating coral reef area accurately is fundamental for assessing the resource and environmental effects on coral reefs. However, there is little clear agreement on the areas of coral reefs until now. The main reason is that there is lack of a reliable method to estimate the areas of coral reefs. To address this problem, a low-cost semi-automatic method of coral reef area estimation by using multi-temporal and multi-spectral satellite images is proposed in this paper. The method contains extraction of instantaneous boundaries and fusion of the boundaries. Firstly, the boundaries of the coral reef geomorphologic zones are automatically delineated by using gradient vector flow-snake model (GVF-Snake) after roughly locating the positions of the geomorphic zone boundaries. Thereafter, the extracted multi-temporal geomorphic zone boundaries are converted to geomorphic zone areas and then fused to establish a reliable and accurate geomorphic zone. According to our experiments on the 53 images of Sentinel-2 MSI (the Landsat 8 OLI images are used to verify method stability, the area of Ling Yang Reef is 17.29 km2), the area of Ling Yang Reef is 17.22 km2, among which the areas of the front reef slope, the reef flat-lagoon slope, and the lagoon are 1.76 km2, 10.29 km2, and 5.17 km2, respectively. The results are consistent with in-field survey data. Specifically, the differences between the positions of the geomorphic zone boundaries extracted by using the proposed method and those determined by bathymetric data are in the range of 0.2−4.9 m (less than 0.5 pixel of Sentinel-2 MSI images). The differences between the outline of the coral reef and the 30 m isobath line is also within 1 pixel (5.7−9.5 m). The difference between the area extracted from multi-temporal images by using the proposed method and the area determined by using a high-resolution WorldView-2 image is 0.02%, i.e. Coral reef area calculated from multi-temporal Sentinel-2 MSI images by using our method is able to compete to high-resolution WorldView-2 image in accuracy. Furthermore, the complete, the correction, and the quality of the boundaries are improved from 60%, 64%, and 54% for single-image method to 84%, 83%, and 72% for our multi-temporal method, respectively. Besides, the proposed method can also reduce variations of the estimated coral reef area caused by using satellite images with different sensors. In other word, if more than 6 scenes of satellite images was utilized, the standard deviations of the estimated coral reef area are shown to be less than 0.01 km2 and 0.05 km2 respectively for Sentinel-2 MSI and Landsat 8 OLI images. They are only equivalent to 0.2% and 0.5% of the total coral reef area. In summary, the proposed method is accurate, reliable, and stable for coral reef area estimation.
Estimating coral reef area accurately is fundamental for assessing the resource and environmental effects on coral reefs. However, there is little clear agreement on the areas of coral reefs until now. The main reason is that there is lack of a reliable method to estimate the areas of coral reefs. To address this problem, a low-cost semi-automatic method of coral reef area estimation by using multi-temporal and multi-spectral satellite images is proposed in this paper. The method contains extraction of instantaneous boundaries and fusion of the boundaries. Firstly, the boundaries of the coral reef geomorphologic zones are automatically delineated by using gradient vector flow-snake model (GVF-Snake) after roughly locating the positions of the geomorphic zone boundaries. Thereafter, the extracted multi-temporal geomorphic zone boundaries are converted to geomorphic zone areas and then fused to establish a reliable and accurate geomorphic zone. According to our experiments on the 53 images of Sentinel-2 MSI (the Landsat 8 OLI images are used to verify method stability, the area of Ling Yang Reef is 17.29 km2), the area of Ling Yang Reef is 17.22 km2, among which the areas of the front reef slope, the reef flat-lagoon slope, and the lagoon are 1.76 km2, 10.29 km2, and 5.17 km2, respectively. The results are consistent with in-field survey data. Specifically, the differences between the positions of the geomorphic zone boundaries extracted by using the proposed method and those determined by bathymetric data are in the range of 0.2−4.9 m (less than 0.5 pixel of Sentinel-2 MSI images). The differences between the outline of the coral reef and the 30 m isobath line is also within 1 pixel (5.7−9.5 m). The difference between the area extracted from multi-temporal images by using the proposed method and the area determined by using a high-resolution WorldView-2 image is 0.02%, i.e. Coral reef area calculated from multi-temporal Sentinel-2 MSI images by using our method is able to compete to high-resolution WorldView-2 image in accuracy. Furthermore, the complete, the correction, and the quality of the boundaries are improved from 60%, 64%, and 54% for single-image method to 84%, 83%, and 72% for our multi-temporal method, respectively. Besides, the proposed method can also reduce variations of the estimated coral reef area caused by using satellite images with different sensors. In other word, if more than 6 scenes of satellite images was utilized, the standard deviations of the estimated coral reef area are shown to be less than 0.01 km2 and 0.05 km2 respectively for Sentinel-2 MSI and Landsat 8 OLI images. They are only equivalent to 0.2% and 0.5% of the total coral reef area. In summary, the proposed method is accurate, reliable, and stable for coral reef area estimation.
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