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Journal of Oceanology and Limnology
Journal Prestige (SJR): 0.301  Citation Impact (citeScore): 1 Number of Followers: 4  Hybrid journal (It can contain Open Access articles)ISSN (Print) 2096-5508 - ISSN (Online) 2523-3521 Published by Springer-Verlag  [2468 journals]
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- A new decomposition model of sea level variability for the sea level
anomaly time series prediction-
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Abstract: Rising sea level is of great significance to coastal societies; predicting sea level extent in coastal regions is critical. When carrying out predictions, the subsequences obtained using decomposition methods may exhibit a certain regularity and therefore can provide multidimensional information that can be used to improve prediction models. Traditional decomposition methods such as seasonal and trend decomposition using Loess (STL) focus mostly on the fluctuating trend of time series and ignore its impact on prediction. Methods in the signal decomposition domain, such as variational mode decomposition (VMD), have no physical significance. In response to the above problems, a new decomposition method for sea level anomaly time series prediction (DMSLAP) is proposed. With this method, the trend term in a time series can be isolated and the effects of abnormal sea level change behaviors can be attenuated. We decompose multiperiod characteristics using this method while maintaining the smoothness of the analyzed series. Satellite altimetry data from 1993 to 2020 are used in experiments conducted in the study area. The results are then compared with predictions obtained using existing decomposition methods such as the STL and VMD methods and time varying filtering based on empirical mode decomposition (TVF-EMD). The performance of DMSLAP combined with a prediction method resulted in optimal sea level anomaly (SLA) predictions, with a minimum root mean square error (RMSE) of 1.40 cm and a maximum determination coefficient (R2) of 0.93 during 2020. The DMSLAP method was more accurate when predicting 1-year data and 3-year data. The TVF-EMD and DMSLAP methods had comparable accuracies, and the periodic term decomposed by the DMSLAP method was more in line with the actual law than that derived using the TVF-EMD method. Thus, DMSLAP can decompose SLA time series better than existing methods and is an effective tool for obtaining short-term SLA prediction.
PubDate: 2023-05-27
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- Effect of light and nutrients on interspecific interactions between
submerged macrophytes: implications for restoration of multispecies
aquatic vegetation in eutrophic lakes-
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Abstract: Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes. However, little is known about the interactions between successional and existing species of different growth forms, particularly under the low light and high nutrient conditions of eutrophic lakes. We measured the functional traits of mature Vallisneria natans (Lour.) Hara plants and Potamogeton crispus L. shoots in monoculture and mosaic patterns under different light and nutrient conditions. The effect of light on functional traits of the submerged macrophyte species was more significant than that of nutrients, but the reverse was true for P. crispus biomass allocation. Moreover, interspecific interactions affected only the submerged macrophytes under the low light condition and varied with species. Specifically, the interaction of P. crispus to V. natans was biased towards competition, while the interaction of V. natans to P. crispus was converted from facilitation to competition by eutrophication, particularly in the homogenous mosaic growth pattern. This study demonstrates that sufficient light is a prerequisite and patch planting is an effective means to form a multispecies submerged vegetation system. In addition, we emphasize that the coexistence of eutrophication and low light will likely result in a competition between submerged macrophytes thus simplifying the vegetation, even if their growth forms and growing seasons are different. These findings help explain the collapse of multispecies submerged vegetation and guide the restoration of aquatic plants in eutrophic lakes.
PubDate: 2023-05-27
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- Comparison of multiple salinity datasets: upper ocean salinity and
stratification in the tropical Pacific during the Argo period-
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Abstract: Ocean salinity is an important variable that affects the ocean stratification. We compared the salinity and ocean stratification in the tropical Pacific derived from the Argo (Array for Real-time Geostrophic Oceanography data), EN4 (Ensemble 4 analysis), SODA (the Simple Ocean Data Assimilation reanalysis), IAP (Institute of Atmospheric Physics data), and ORAS4 (Ocean Reanalysis System 4) over 2005–2017. Results show that the spatial distribution of climatological mean of sea surface salinity (SSS) in all the products is consistent, and the low salinity region showed large deviation and strong dispersion. The Argo has the smallest RMSE and the highest correlation with the ensemble mean, while the IAP shows a high-salinity deviations relative to other datasets. All the products show high positive correlations between the sea surface density (SSD) and SSS with respect to the deviations of climatological mean from ensemble mean, suggesting that the SSD deviation may be mainly influenced by the SSS deviation. In the aspect of the ocean stratification, the mixed layer depth (MLD) climatological mean in the Argo shows the highest correlation with the ensemble mean, followed by EN4, IAP, ORAS4, and SODA. The Argo and EN4 show thicker barrier layer (BL) relative to the ensemble mean while the SODA displays the largest negative deviation in the tropical western Pacific. Furthermore, the EN4, ORAS4, and IAP underestimate the stability in the upper ocean at the depths of 20–140 m, while Argo overestimates ocean stability. The salinity fronts in the western-central equatorial Pacific from Argo, EN4, and ORAS4 are consistent, while those from SODA and IAP show large deviations with a westward position in amplitude of 0°–6° and 0°–10°, respectively. The SSS trend patterns from all the products are consistent in having ensemble mean with high spatial correlations of 0.95–0.97.
PubDate: 2023-05-27
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- Metabolomics of astaxanthin hyperaccumulation in Haematococcus pluvialis
under high light stress-
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Abstract: Variation in metabolite profiles of Haematococcus pluvialis (a type of unicellular green algal) under light stress is a key issue of study at the present. To investigate the effect of light intensity on accumulation of astaxanthin in H. pluvialis, a 26-day batch culture experiment of H. pluvialis under the light intensity levels at 73, 127, 182, 236, and 291 µmol/(m2·s) was conducted. Therefore, the optimal light intensity and the corresponding metabolic pathways of accumulation in H. pluvialis were determined. Results show that 236 µmol/(m2·s) was the optimum light intensity to induce astaxanthin accumulation, at which a maximum content of 9.01 mg/L was achieved on Day 24. A total of 132 metabolites were identified and quantified, of which 38 differential metabolites were highlighted and classified, including 3 fatty acids or intermediates, 5 amino acids or derivatives, 5 carbohydrates or intermediates, 16 nucleoside derivatives, and 9 other metabolites using LC-MS/MS technique. Subsequently, 16 statistically significant differential metabolic pathways were enriched and annotated based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis between the control and the 236 µmol/(m2·s) treatment group (P<0.05). In addition, the bioprocesses included cellular basal metabolism and signaling systems, such as carbohydrate metabolism, amino acid metabolism, glycerol and derivatives metabolism, nucleotide and derivative metabolism, and inositol phosphate metabolism were activated and regulated under strong light stress conditions. Moreover, 4 hub metabolites containing D-glucose-6-phosphate, L-tyrosine, glycerol-3-phosphate, and L-glutamine were identified, based on which the associated metabolic network was constructed. The study provided a metabolomic view of astaxanthin accumulation in H. pluvialis under strong light stress.
PubDate: 2023-05-26
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- The dissolution of total suspended solids and treatment strategy of
tailwater in a Litopenaeus vannamei recirculating aquaculture system-
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Abstract: In recirculating aquaculture systems (RASs), the effective treatment of aquaculture tailwater is essential to maintain the health of the RAS. This study investigated the optimal time and method for tailwater treatment during three periods of the aquaculture of the Litopenaeus vannamei: nursery (0–26 d), middle (27–57 d), and later (57–104 d). The variation of several water parameters during the dissolution of total suspended solid (TSS) in tailwater, applied with the effects of ozone on the microorganism and water quality parameters were investigated. Results showed that the TSS concentrations in tailwater decreased with time, although not significantly (P>0.05), whereas total ammonia nitrogen (TAN), nitrite (NO 2 − -N), and nitrate (NO 3 − -N) increased significantly (P<0.05). Therefore, TSS should be removed from the tailwater as early as possible, being most optimal within 4 h. Ozone removed 38.24%–48.95% of TSS, 17.78%–90.14% of TAN, and 87.50%–98.90% of NO 2 − -N after 4 h of treatment. However, it resulted in the significant accumulation of NO 3 − -N. Moreover, the total number of Vibrio and bacterial counts in aquaculture tailwater was reduced completely by ozone within 4 h. Thus, these results provided technical details and data support for the effective treatment of tailwater from shrimp RAS.
PubDate: 2023-05-26
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- Water temperature induced interannual variation in spawning of Japanese
Spanish mackerel Scomberomorus niphonius in the northern Yellow Sea-
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Abstract: Japanese Spanish mackerel Scomberomorus niphonius is a pelagic, neritic species that occurs in the Yellow Sea in high commercial value. The spawning period of this fast-growing species is controlled by water temperature. Based on microstructural analysis of otoliths from 145 young-of-the-year (YoY) S. niphonius collected by trawl in 2017, 2018, and 2020, and the temporal variation in the spawning period in the northern Yellow Sea, and its relationship to water temperature were examined. We found that the spawning lasted from late April to late June but differed in year: in 2017 it occurred from April 23 to June 1 and peaked in early May, in 2018 it extended later from May 7 to June 29, and in 2020 from May 6 to June 22 and peaked later from late May to mid-June. The highest temperature in 2017 corresponds with the earliest end of the spawning period and a lower growing degree-day (GDD, °C·day) of 383 °C·day. In 2018, slower warming corresponds with a longer spawning period, and a GDD spawning period of 506 °C·day. Rapid warming in late 2020 corresponds with a spawning peak, and a GDD spawning temperature of 448 °C·day. Despite differences in spawning period, the water temperature when spawning commenced was 10–12 °C. Therefore, water temperature is the major determinant of the spawning period, affecting both the starting and the ending of spawning. This study improved our understanding of the spawning dynamics and environmental adaptation of S. niphonius, and how these might change in environments subject to increased warming.
PubDate: 2023-05-24
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- Spatial-temporal dynamics of bacterioplankton communities in the breeding
area of large yellow croaker Larimichthys crocea in Sansha Bay, China-
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Abstract: As an important spawning ground for large yellow croaker Larimichthys crocea, Sansha Bay, South China Sea has been a research hotspot. However, studies on the influence of the bacterioplankton community and assessments of its seasonal succession of bacterioplankton in different sea areas in Sansha Bay are still limited. To address the issue, we use 16S rRNA gene amplicon sequencing and functional prediction to investigate the spatial-temporal dynamics of the bacterioplankton community in three distinct areas, i.e., Breeding Area (BA), Yantian Harbor (YH), and Bay Margin (BM) of Sansha Bay. Results show that the structure of the bacterioplankton community in Sansha Bay had a significant seasonal succession. Moreover, the representative zero-radius Operation Taxon Units in different seasons were significantly different among the three selected sea areas. Specifically, during the breeding season, bacterioplankton communities in BA were characterized by compound-degrading bacteria, such as Rhodococcus and Owenweeksia, while in YH and BM, animal parasites or symbionts such as Vibrio and Arcobacter were dominant. Furthermore, the redundancy analysis and Spearman correlation analysis further explained that water temperature, dissolved oxygen, and ammonia nitrogen were the main environmental factors responsible for the difference. In addition, the bioindicator functions screened by Functional Annotation of Prokaryotic Taxa and random forest machine learning mainly relied on compound degradation, nitrite oxidation, and photoheterotrophy. The compound-degradation-corresponded bacterioplankton genera such as Rhodococcus had relatively higher abundance in BM, while Nitrospina corresponding to nitrite oxidation tended to be abundant in YH and BA. Based on the spatial and temporal variation in the composition and function of bacterioplankton, our findings provide a basis for understanding the theory of bacterioplankton community structure in the inner-bay habitat of the large yellow croaker in Sansha Bay.
PubDate: 2023-05-24
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- Characterization of Wnt genes in Argopecten scallops and their involvement
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Abstract: As “Bohai Red” scallops were originated from the hybrids between the Peruvian scallop (Argopecten purpuratus) and the bay scallop (Argopecten irradians) northern subspecies (Argopecten irradians irradians). Twelve Wnt members were identified from the two subspecies of bay scallop, and 13 Wnt genes were found in the genome of the Peruvian scallop. Protein structure analyses showed that most Wnt genes poses all 5 conserved motifs except Wnt1, Wnt2, Wnt6, and Wnt9 in the bay scallops and Wnt2 and Wnt9 in the Peruvian scallop. Unexpectedly, Wnt8 gene was present while Wnt3 was absent in both the bay scallops and the Peruvian scallop. Phylogenetic analysis revealed that Wnt3 might have disappeared in the early evolution of mollusks. The expression profile of Wnt genes in the “Bohai Red” exposed to different temperatures was examined by qRT-PCR. Results show that expression of Wnt genes responded differentially to temperature changes. The Wnt genes such as Wnt1, Wnt6, Wnt7, Wnt11, and WntA that responded slowly to low and high temperature stresses may be related to the maintenance of basic homeostasis. Other Wnt genes such as Wnt4, Wnt9, Wnt5, and Wnt2 that responded rapidly to low temperature may play an important role in organismal protection against low temperature stress. And yet some Wnt genes including Wnt10, Wnt16, and Wnt8 that responded quickly to high temperature stress may play key roles in response to high temperature stress. The results provide new insights into the evolution and function of Wnt genes in bivalves and eventually benefit culture of “Bohai Red” scallops.
PubDate: 2023-05-20
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- Identification of navigation characteristics of single otter trawl vessel
using four machine learning models-
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Abstract: Fishing logbook records the fishing behaviors and other information of fishing vessels. However, the accuracy of the recorded information is often difficult to guarantee due to the misreport and concealment. The fishing vessel monitoring system (VMS) can monitor and record the navigation information of fishing vessels in real time, and it may be used to improve the accuracy of identifying the state of fishing vessels. If the VMS data and fishing logbook are combined to establish their relationships, then the navigation characteristics and fishing behavior of fishing vessels can be more accurately identified. Therefore, first, a method for determining the state of VMS data points using fishing log data was proposed. Secondly, the relationship between VMS data and the different states of fishing vessels was further explored. Thirdly, the state of the fishing vessel was predicted using VMS data by building machine learning models. The speed, heading, longitude, latitude, and time as features from the VMS data were extracted by matching the VMS and logbook data of three single otter trawl vessels from September 2012 to January 2013, and four machine learning models were established, i.e., Random Forest (RF), Adaptive Boosting (AdaBoost), K-Nearest Neighbor (KNN), and Gradient Boosting Decision Tree (GBDT) to predict the behavior of fishing vessels. The prediction performances of the models were evaluated by using normalized confusion matrix and receiver operator characteristic curve. Results show that the importance rankings of spatial (longitude and latitude) and time features were higher than those of speed and heading. The prediction performances of the RF and AdaBoost models were higher than those of the KNN and GBDT models. RF model showed the highest prediction performance for fishing state. Meanwhile, AdaBoost model exhibited the highest prediction performance for non-fishing state. This study offered a technical basis for judging the navigation characteristics of fishing vessels, which improved the algorithm for judging the behavior of fishing vessels based on VMS data, enhanced the prediction accuracy, and upgraded the fishery management being more scientific and efficient.
PubDate: 2023-05-20
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- Improvement in lipid production and biodiesel quality of Pavlova sp. by
monochromatic illumination-
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Abstract: Pavlova sp. is not only one of the most popular microalgae in aquaculture, but also a source of high-quality biodiesel feedstock. With white light as a control (W), Pavlova sp. was cultured in this study under varying light quality, including monochromatic red light (R), blue light (B), and combinations thereof with different proportions (illuminators of mRnB, comprised of m red light units and n blue ones, m+n=7), to examine the effects of illuminating light quality on biocomponent production and biodiesel quality. The results show that combined monochromatic light, especially 2R5B, 3R4B, 4R3B, and 5R2B, could improve the growth of Pavlova sp. The dry weight of harvested algae powder in the 5R2B group reached 418.03 mg/L, and was 22.65% higher than that in the control group (W). Lipid production under combined monochromatic light of 4R3B reached 107.86 mg/L, and was 25.61% higher than in the control (W). In addition, illumination using 4R3B increased the proportion of C16:0 (palmitic acid) and C16: 1 (palmitoleic acid) fatty acids in Pavlova sp. by 15.55% and 21.94%, respectively, which translates into improved biodiesel quality. All cetane numbers (CN) for 4R3B–6R1B were over 51, while iodine values (IV) and degrees of unsaturation (DU) were reduced, leading to more stable biodiesel suitable for long-term storage. In addition, protein production under 6R1B was as high as 31.56 mg/L, 1.8 times greater than under W. Light quality is proposed as an effective tool to regulate biocomponent production by microalgae.
PubDate: 2023-05-20
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- Genetic diversity and population structure of the sea star Asterias
amurensis in the northern coast of China-
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Abstract: The sea star Asterias amurensis is widely viewed as a severe “marine pest” because of its broad feeding habits. Over the past few decades, A. amurensis undergoes massive and sporadic population outbreaks worldwide, causing extensive economic and ecological losses to the local aquaculture industry and marine ecosystem. Understanding the genetic diversity and population structure of A. amurensis can provide vital information for resource management. By analyzing the polymorphism of the mitochondrial cytochrome C oxidase subunit I (COI) gene and ten simple sequence repeat (SSR) microsatellites markers, the genetic diversity and population structure of A. amurensis of four populations along the northern coast of China was uncovered. A total of 36 haplotypes were identified, and a main haplotype was found in four populations. The Qingdao (QD) population displayed the highest genetic diversity among all the populations. The AMOVA and pairwise Fst showed that there was small but statistically significant population differentiation among the four populations, especially between QD and Weihai (WH). Moreover, the principal component analysis (PCA) and admixture analysis showed that several individuals in Yantai (YT) and Dalian (DL) had little genetic association with other individuals. Overall, this study provided useful information of the genetic diversity and population structure of A. amurensis and will contribute to the resource management of A. amurensis in China.
PubDate: 2023-05-12
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- Expression and localization of vitellogenin genes (VTG) and receptor (VGR)
in the gonad development of silver pomfret Pampus argenteus-
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Abstract: Vitellogenesis is the main event of oocyte growth in oviparous animals, which is mainly manifested by the accumulation of vitellogenin (VTG). The accumulation of vitellogenin depends mainly on the absorption of exogenous vitellogenin, which enters oocyte through endocytosis mediated by its receptor (VGR). We investigated the expression and localization of VTG and VGR during gonad development of Pampus argenteus. The qPCR results show that vtgs were not expressed in male fish, but in the ovary and liver of female fish; the expression levels went up at first and then down. The expression levels of vgr in the testis were low and only 1%–3% of that in ovary. ELISA results show that during the ovarian development of P. argenteus, VTG in liver, serum, and ovary all showed a trend from increasing to decreasing. However, VTG in liver peaked in Stage IV, and in serum and ovary peaked in Stage V, reflecting changes in the characteristics of VTG in the liver (synthesis), blood (transport), and ovaries (accumulation). During gonad development, VGR in the ovaries first increased and then decreased, reaching a peak in Stage V, in contrast to vgr mRNA expression. The VGR content in the testis was extremely low and stable, consistent with vgr mRNA. Immunohistochemistry results show that the location and intensity of VTG and VGR positive signals were synchronized with the changes of their protein content, which revealed that VTG was mainly synthesized in the liver cytoplasm, secreted into the blood, and transported to ovary in Stage III. VGR is highly expressed in oocytes in Stage II. In Stage III, a large amount of VTG reaches the ovary, when VGR begins to translate and is subsequently transported to the plasma membrane of the oocyte. Therefore, the positive signal of VGR was stronger near the plasma membrane of oocytes in Stages I and II. By using qPCR, ELISA, and immunohistochemistry, the synthesis, transport, and accumulation of vitellogenin were elucidated and the mechanism of its endocytosis on egg membrane mediated by VTG during the development of P. argenteus was revealed preliminarily.
PubDate: 2023-05-12
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- Marine ecological risk assessment for the herbicide sulfometuron-methyl
based on species sensitivity distribution approach-
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Abstract: In recent years, herbicide sulfometuron-methyl (SM) has been used to kill the invasive plant Spartina alternflora in some coastal areas of China, which may lead to the toxic effects on non-target marine organisms. The 96-h median effective concentrations (96-h EC50) of SM on six species of marine microalgae were measured in growth inhibition tests, and were then compared with other published toxicity data, based on which a method of species sensitivity distribution (SSD) was built to estimate the hazardous concentration of SM for 5% of species (HC5) and potentially affected fraction (PAF) for a certain concentration. Results indicate that SM exhibited a high toxicity to two species of green algae (Chlorella pacifica and Dunaliella salina) with a 96-h EC50 of 0.11 and 0.13 mg/L respectively, had a medium toxicity to two species of golden algae (Diacronema viridis and Isochrysis galbana) with a 96-h EC50 of 14.24 and 21.48 mg/L respectively, and showed a low toxicity to two species of diatoms (Skeletonema costatum and Phaeodactylum tricornutum) with a 96-h EC50 of 148.99 and >100 mg/L, respectively. The estimated values of HC5 and the predicted no-effect concentrations (PNEC) for SM were 0.077 and 0.015 mg/L, respectively. According to the current dosage for killing S. alterniflora in tidal flats in Fujian Province, China, SM entering the sea by spraying might cause the acute injury or death of 14% of marine species. This hazard could last for about a month for those sensitive species. Therefore, on the premise of inhibiting the growth of this invasive plant, the dosage of SM should be reduced as much as possible to avoid severe damage to the marine ecosystem. The results provide a valuable information for marine ecological risk assessment on SM and for marine environmental management.
PubDate: 2023-05-12
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- Compositional characteristics of sediment from Jiaozhou Bay in North China
and the implication to the provenance-
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Abstract: Rare earth elements (REEs) can be used to trace source materials and identify their provenances, because of significant conservation and immobility during chemical alteration processes after erosion of materials from the provenance. This study focused on the temporal variation of REEs for columnar sediments from the mouth of Jiaozhou Bay in North China to understand the potential controls for the geochemical variations of sediments. Through extraction experiments, we identified that the residual fraction is the main host for REEs compared with other fractions (i.e., exchangeable and carbonate fraction, easily reducible oxides fraction, reducible oxides fraction, magnetite fraction). REE ratios (e.g., LaN/SmN and LaN/YbN; N: normalized by chondrite) lack correlations with grain size or the chemical index of alteration (CIA), which is correlated with major elements. All these indicate that these REE variations reflect the varying contribution of source materials from different provenances instead of grain size or chemical weathering effects. REE ratios (e.g., LaN/SmN and LaN/YbN) remain relatively constant until the depth of roughly 40 cm (equivalent to the year 1995), and show obvious changes beyond this depth. Compared REE characteristics of Jiaozhou Bay with those of neighboring rivers and bedrocks, the relative contributions of Dagu River-Jiaolai River, and Licun River may have been increased during the sedimentary processes, which could be caused by the construction of reservoir and related change of aquaculture (e.g., rapid accumulation of organic materials).
PubDate: 2023-05-12
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- Degree of ontogenetic diet shift and trophic niche partitioning of
Euphausia superba and Thysanoessa macrura are influenced by food
availability-
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Abstract: Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly. Studies of the feeding strategies of these two krill species will help us better understand the coexistence mechanisms and estimate the roles that krill played in the food web of the Southern Ocean. The trophodynamics of E. superba and T. macrura at different ontogenetic stages (furcilia, juvenile, adult) were studied using fatty acid and stable isotope biomarkers in the samples collected in Amundsen Sea during austral summer of 2017/2018 and 2018/2019. Diatoms like Fragilariopsis spp. was the most abundant phytoplankton species in the summer of 2017/2018, while the abundance of phytoplankton in the summer of 2018/2019 was dominated by Phaeocystis sp. The gradual increase of the carnivorous index 18:1n–9/18:1n–7 with ontogeny of both species in 2018/2019 indicated more carnivorous feeding of adults compared with juveniles and larvae. Meanwhile, greater δ15N values of T. macrura than that of E. superba were more significant in the juvenile and adult stages during the summer of 2018/2019. Our results indicate that the trophic niche differentiation between the two krill species appeared in postlarval stage and can be influenced by food availability. Compared with E. superba, T. macrura was more prone to feed omnivorously or carnivorously responding to food availability.
PubDate: 2023-04-29
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- Predicting impacts of climate change on the biogeographic patterns of
representative species richness in Prydz Bay-Amery Ice Shelf-
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Abstract: The research on the biological ecology of the Prydz Bay-Amery Ice Shelf in East Antarctica is inadequate under the increasing threat from climate change, especially for Antarctic fish and krill. The Dynamic Bioclimatic Envelope Model (DBEM) has been widely used in predicting the variation of species distribution and abundance in ocean and land under climate change; it can quantify the spatiotemporal changes of multi population under different climate emission scenarios by identifying the environmental preferences of species. The species richness and geographical pattern of six Antarctic representative species around Prydz Bay-Amery ice shelf were studied under RCP 8.5 and RCP 2.6 emission scenarios from 1970 to 2060 using Geophysical Fluid Dynamics Laboratory (GFDL), Institut Pierre Simon Laplace (IPSL), and Max Planck Institute (MPI) earth system models. The results showed that the species richness decreased as a whole, and the latitude gradient moved to the pole. The reason is that ocean warming, sea ice melting, and human activities accelerate the distribution changes of species biogeographical pattern, and the habitat range of krill, silverfish, and other organisms is gradually limited, which further leads to the change of species composition and the decrease of biomass. It is obvious that priority should be given to Prydz Bay-Amery ice shelf in the planning of Marine Protected Areas (MPAs) in East Antarctica.
PubDate: 2023-04-29
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- Descriptions of two species of Nassarius (Gastropoda: Nassariidae) from
the South China Sea-
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Abstract: Two new species belonging to genus Nassarius are described and illustrated based on shell morphology and radular features. Nassarius sanyaensis sp. nov., collected from intertidal zone of Sanya, Hainan Island, China, most resembles Nassarius lyraeformis (Marrat, 1880) in general shell shape, but differs from the latter in having remarkable nodules on shell surface. Nassarius beibuensis sp. nov., sampled from shallow water of Beibu Gulf, is most similar to Nassarius oblongus (Marrat, 1877), but can be distinguished from it mainly in having stronger sculpture. This study expands our knowledge of Nassarius diversity and distribution in China seas.
PubDate: 2023-04-28
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- Factors inducing morphological transition in harmful algal bloom-forming
species Phaeocystis globosa with emphasis on predator chemical cue-
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Abstract: The microalga Phaeocystis globosa is recognized as a harmful alga and also one of the few keystone phytoplankton genera that shape the structure and function of marine ecosystems. P. globosa possess a complex polymorphic life cycle, exhibiting phase alternation between free-living cells of approximately 3–6 µm in diameter and gelatinous colonies (palmelloid stage) reaching several millimeters. The knowledge on the factors that induced the morphological transition of P. globosa in the last two decades was reviewed. Emphasis is given to infochemicals, an additional biological factor induced by predator, with the attempt to reveal a relevant mechanism of induced morphological defense.
PubDate: 2023-04-28
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- Spatio-temporal dynamics of cyanobacterial abundance and toxicity in a
Mediterranean hypereutrophic lake-
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Abstract: The Mediterranean basin is considered one of the most vulnerable areas in the world under the impacts of global warming and changes in precipitation patterns. Oubeira, a shallow and polymictic freshwater lake located in northeastern Algeria (36°50′N, 08°23′E), has recently experienced a significant proliferation of harmful cyanobacteria resulting in the generation of toxins. We carried out this study in order to understand the succession patterns of dominant cyanobacteria and cyanotoxin production and the factors driving this in Oubeira Lake. A total of 26 cyanobacterial genera were identified, and among them Microcystis and Planktothrix accounted for more than 60% of the overall cell abundance. The summer/fall period was dominated by Microcystis, Planktothrix, and in lesser extend by Cylindrospermum, Cylindrospermopsis. During the fall/winter transition, Dolichospermum, Pseudanabaena, and Aphanizomenon were the dominant genera. Statistically, the bloom-forming cyanobacteria showed significant differences between months but not between stations. Intracellular microcystins (MC-LR) was detected in all collected samples (0.62- and 19.14-µg MC-LR equivalent/L), but appeared in high concentrations throughout the period of dominance of Microcystis and Planktothrix. Microcystis was more sensitive to nutrients than to temperature. Planktothrix was more dependent on temperature than on nutrients, which explains their coexistence during summer-fall period. However, both genera are positively correlated with MC-LR and would probably be the main producers of microcystins. Pseudanabaena, Dolichospermum, and Aphanizomenon co-occurred at the end of Planktothrix dominance period (December). Aphanizomenon and Pseudanabaena were correlated negatively with temperature and positively with water conductivity. Dolichospermum showed a strong positive correlation with MC-LR. Oubeira Lake, could serve as a model of how cyanobacteria blooms may develop in lakes within Mediterranean climates.
PubDate: 2023-04-28
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- Sedimentary record of a late Holocene storm event in Laizhou Bay, Bohai
Sea, China-
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Abstract: The Bohai Sea is influenced by numerous extreme oceanic wave events in history. However, it is often difficult to determine the types of these events due to the lack of detailed historical records, causing uncertainty in the reconstruction of historical coastal disasters. We investigated an anomalous sand layer in the Xiliyu Village by the coast of Laizhou Bay, Shandong, from which an extreme event deposit was identified using a multi-proxy approach including grain size distribution, geochemistry, and magnetic susceptibility. This event was dated 2 700–3 100 a bp, and caused inundation of a large coastal area of Laizhou Bay. By comparing historical records with instrumental data, we believe that the event deposit was generated by a severe storm surge with wind speed of >34.9 m/s.
PubDate: 2023-04-28
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