Remote sensing of upwelling off Australia's north-east coast

Abstract. Cross-shelf processes drive the exchange of water between the continental shelf and western boundary currents, leading to the import and export of heat, freshwater, sediments, nutrients, plankton, fish larvae, and other properties. Upwelling is an important process which modulates those exchanges. It regulates primary productivity, which in turn promotes higher trophic levels and fisheries. In this paper, we investigate upwelling events in the East Australian Current (EAC) intensification zone off Southeast Queensland through the analysis of remotely-sensed Chlorophyll-a (Chl-a) and Sea Surface Temperature (SST) as well as wind and ocean reanalysis products. A particular focus is on identifying the likely mechanisms that drive upwelling events during the austral autumn to winter which are evident from cold SST and enhanced Chl-a concentrations. Four complementary Upwelling Indices (UIs) are derived. Chl-a (UIChla) and SST (UISST) based indices characterize the oceanic response to upwelling, while indices based on wind (UIw) and current (UIc) data capture the forcing of upwelling. The spatial and temporal variability of all UIs is examined over the continental shelf. It reveals distinct seasonal patterns. For the northern region, UIs identify the well-known Southeast Fraser Island Upwelling System. It prevails during the austral spring to early summer and is driven by current- and upwelling favourable wind. In contrast, upwelling is enhanced over the southern shelf during austral autumn to winter. About 70 % of all UISST and UIChla identified upwelling events occur during this period. A case study is presented that provides observational evidence for the existence of a shelf-break upwelling. Simultaneous downwelling favourable wind stress and upwelling favourable current-driven bottom stress establish a flow convergence in the bottom boundary layer (BBL). These convergent BBL flows force upwelling of cold and nutrient-rich slope waters as evident from negative SST anomaly and enhanced Chl-a in austral autumn to winter. It is evident from these results that the shelf region is characterised by two distinct seasonally reoccurring upwelling regimes.

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Age, growth and population structure of jumbo flying squid, Dosidicus gigas, based on statolith microstructure off the Exclusive Economic Zone of Chilean waters

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315410001438 ◽

2010 ◽

Vol 91 (1) ◽

pp. 229-235 ◽

Cited By ~ 17

Author(s):

Xinjun Chen ◽

Huajie Lu ◽

Bilin Liu ◽

Yong Chen

Keyword(s):

Population Structure ◽

Growth Rates ◽

The Body ◽

Exclusive Economic Zone ◽

Spatial And Temporal Variability ◽

Dosidicus Gigas ◽

Austral Spring ◽

Economic Zone ◽

Austral Autumn ◽

Jumbo Flying Squid

The jumbo flying squid, Dosidicus gigas, support an important squid fishery off the Exclusive Economic Zone of Chilean waters. However, we only have limited information about their biology. In this study, age, growth and population structure of D. gigas were studied using statoliths from 533 specimens (386 females and 147 males) randomly sampled in the Chinese squid jigging surveys from 2007 to 2008 off the Exclusive Economic Zone of Chile. Mantle lengths (MLs) of the sample ranged from 206 to 702 mm, and their ages were estimated from 150 to 307 days for females and from 127 to 302 days for males. At least two spawning groups were identified, the main spawning peak tended to occur between August and November (austral spring group), and the secondary peak appeared during March to June (austral autumn group). The ML–age relationship was best modelled by a linear function for the austral spring group and a power function for the austral autumn group, and the body weight (BW)–age relationship was best described by an exponential function for both the groups. Instantaneous relative growth rates and absolute growth rates for ML and BW did not differ significantly between the two groups. The growth rate of D. gigas tended to be high at young stages, and then decreased after the sub-adult stage (>180 days old). This study suggests large spatial and temporal variability in key life history parameters of D. gigas, calling for the collection of more data with fine spatial and temporal scales to further improve our understanding of the fishery biology of D. gigas.

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Fish Catch Is Related to the Fluctuations of a Western Boundary Current

Journal of Physical Oceanography ◽

10.1175/jpo-d-17-0041.1 ◽

2018 ◽

Vol 48 (3) ◽

pp. 705-721 ◽

Cited By ~ 3

Author(s):

Lie-Yauw Oey ◽

Jia Wang ◽

M.-A. Lee

Keyword(s):

North Pacific ◽

Fish Larvae ◽

Early Spring ◽

Western Boundary Current ◽

Western Boundary ◽

Boundary Current ◽

Wind Stress Curl ◽

Chl A ◽

Clear Cut ◽

Fish Catch

AbstractIn eastern boundary upwelling ecosystems, substantial variance of biological productivity (~50%) can often be related to physical forcing such as winds and ocean temperatures. Robust biophysical connections are less clear-cut in western boundary currents. Here the authors show that interannual variation of fish catch along the western boundary current of the North Pacific, the Kuroshio, significantly correlates (r = 0.67; p < 0.001) with the current’s off-slope (more fish) and on-slope (less fish) sideways shifts in the southern East China Sea. Remotely, transport fluctuations and fish catch are related to the oscillation of a wind stress-curl dipole in the tropical–subtropical gyre of the western North Pacific. Locally, the current’s sideways fluctuations are driven by transport fluctuations through a feedback process between along-isobath pressure gradients and vertical motions: upwelling (downwelling) during the off-slope (on slope) shift, which in turn significantly enhances (depresses) the chlorophyll-a (Chl-a) concentration in winter and early spring. The authors hypothesize that changes in the phytoplankton biomass as indicated by the Chl-a lead to changes in copepodites, the main food source of the fish larvae, and hence also to the observed variation in fish catch.

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Satellite-Derived Protein Concentration of Phytoplankton in the Southwestern East/Japan Sea

Journal of Marine Science and Engineering ◽

10.3390/jmse9020189 ◽

2021 ◽

Vol 9 (2) ◽

pp. 189

Author(s):

Hyeonji Bae ◽

Dabin Lee ◽

Jae Joong Kang ◽

Jae Hyung Lee ◽

Naeun Jo ◽

...

Keyword(s):

Protein Concentration ◽

Japan Sea ◽

Biological Properties ◽

Measured Data ◽

Trophic Levels ◽

Coefficient Of Determination ◽

P Value ◽

Chl A ◽

Major Factors

The cellular macromolecular contents and energy value of phytoplankton as primary food source determine the growth of higher trophic levels, affecting the balance and sustainability of oceanic food webs. Especially, proteins are more directly linked with basic functions of phytoplankton biosynthesis and cell division and transferred through the food chains. In recent years, the East/Japan Sea (EJS) has been changed dramatically in environmental conditions, such as physical and chemical characteristics, as well as biological properties. Therefore, developing an algorithm to estimate the protein concentration of phytoplankton and monitor their spatiotemporal variations on a broad scale would be invaluable. To derive the protein concentration of phytoplankton in EJS, the new regional algorithm was developed by using multiple linear regression analyses based on field-measured data which were obtained from 2012 to 2018 in the southwestern EJS. The major factors for the protein concentration were identified as chlorophyll-a (Chl-a) and sea surface nitrate (SSN) in the southwestern EJS. The coefficient of determination (r2) between field-measured and algorithm-derived protein concentrations was 0.55, which is rather low but reliable. The satellite-derived estimation generally follows the 1:1 line with the field-measured data, with Pearson’s correlation coefficient, which was 0.40 (p-value < 0.01, n = 135). No remarkable trend in the long-term annual protein concentration of phytoplankton was found in the study area during our observation period. However, some seasonal difference was observed in winter protein concentration between the 2003–2005 and 2017–2019 periods. The algorithm is developed for the regional East/Japan Sea (EJS) and could contribute to long-term monitoring for climate-associated ecosystem changes. For a better understanding of spatiotemporal variation in the protein concentration of phytoplankton in the EJS, this algorithm should be further improved with continuous field surveys.

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Response of Total Suspended Sediment and Chlorophyll-a Concentration to Late Autumn Typhoon Events in the Northwestern South China Sea

Remote Sensing ◽

10.3390/rs13152863 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2863

Author(s):

Junyi Li ◽

Huiyuan Zheng ◽

Lingling Xie ◽

Quanan Zheng ◽

Zheng Ling ◽

...

Keyword(s):

South China Sea ◽

Continental Shelf ◽

Suspended Sediment ◽

Chlorophyll A ◽

South China ◽

Total Suspended Sediment ◽

Offshore Area ◽

Chl A ◽

Late Autumn ◽

China Sea

Strong typhoon winds enhance turbulent mixing, which induces sediment to resuspend and to promote chlorophyll-a (Chl-a) blooms in the continental shelf areas. In this study, we find limited Chl-a responses to three late autumn typhoons (typhoon Nesat, Mujigae and Khanun) in the northwestern South China Sea (NWSCS) using satellite observations. In climatology, the Chl-a and total suspended sediment (TSS) concentrations are high all year round with higher value in autumn in the offshore area of the NWSCS. After the typhoon passage, the Chl-a concentration increases slightly (23%), while even TSS enhances by 280% on the wide continental shelf of the NWSCS. However, in the southern area, located approximately 100 km from the typhoon tracks, both TSS and Chl-a concentrations increase 160% and 150% after typhoon passage, respectively. In the deeper area, the increased TSS concentration is responsible for the considerable increase of the Chl-a. An empirical analysis is applied to the data, which reveals the TSS and Chl-a processes during typhoon events. The results of this study suggest a different mechanism for Chl-a concentration increase and thus contribute toward further evaluation of typhoon-induced biological responses.

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Five new species of Oncholaimellus (Oncholaimidae: Nematoda) from north-east Brazil, with an emended diagnosis and an updated key to the genus

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315414000113 ◽

2014 ◽

Vol 94 (4) ◽

pp. 703-727 ◽

Cited By ~ 2

Author(s):

Patrícia Fernandes Neres ◽

Maria Cristina da Silva ◽

Geruso Vieira de Miranda-Júnior ◽

Verônica Fonsêca-Genevois ◽

André Morgado Esteves

Keyword(s):

New Species ◽

Continental Shelf ◽

North East ◽

Potiguar Basin ◽

Tail Shape ◽

Emended Diagnosis

Five new species of Oncholaimellus are described. They were found in macrofauna samples from the continental shelf in the Potiguar Basin, north-east Brazil. Cuticular pores with a sclerotized outline associated with a gland were observed in some species. Oncholaimellus multiporus sp. nov. is differentiated from other species by the presence of cuticular pores of different sizes; the smaller pores are abundant and give an appearance of ornamentation. Oncholaimellus intersexus sp. nov. and O. distortus sp. nov. are similar, but differ in the size of the external labial and cephalic setae compared to the corresponding diameter, the presence of the cuticular pores and the tail shape. Oncholaimellus paulus sp. nov. and O. sineporus sp. nov. are similar, although features such as the external labial and cephalic setae size compared to the corresponding diameter and the cuticular pores differentiate between them.

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Extreme Levels of Ocean Acidification Restructure the Plankton Community and Biogeochemistry of a Temperate Coastal Ecosystem: A Mesocosm Study

Frontiers in Marine Science ◽

10.3389/fmars.2020.611157 ◽

2021 ◽

Vol 7 ◽

Author(s):

Carsten Spisla ◽

Jan Taucher ◽

Lennart T. Bach ◽

Mathias Haunost ◽

Tim Boxhammer ◽

...

Keyword(s):

Ocean Acidification ◽

Fish Larvae ◽

Plankton Community ◽

Trophic Levels ◽

Coastal Regions ◽

Mesozooplankton Community ◽

Planktonic Food ◽

Elemental Stoichiometry ◽

Secondary Consumers ◽

Induced Changes

The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978 – 2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced differences in the plankton community emerged early in the experiment, and were amplified by enhanced top-down control throughout the study period. The plankton groups responding most profoundly to high CO2 conditions were cyanobacteria (negative), chlorophyceae (negative), auto- and heterotrophic microzooplankton (negative), and a variety of mesozooplanktonic taxa, including copepoda (mixed), appendicularia (positive), hydrozoa (positive), fish larvae (positive), and gastropoda (negative). The restructuring of the community coincided with significant changes in the concentration and elemental stoichiometry of particulate organic matter. Results imply that extreme CO2 events can lead to a substantial reorganization of the planktonic food web, affecting multiple trophic levels from phytoplankton to primary and secondary consumers.

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Spatial and temporal variability in the response of phytoplankton and prokaryotes to B-vitamin amendments in an upwelling system

Biogeosciences ◽

10.5194/bg-17-2807-2020 ◽

2020 ◽

Vol 17 (10) ◽

pp. 2807-2823

Author(s):

Vanessa Joglar ◽

Antero Prieto ◽

Esther Barber-Lluch ◽

Marta Hernández-Ruiz ◽

Emilio Fernández ◽

...

Keyword(s):

Vitamin B12 ◽

Growth Stimulation ◽

B Vitamins ◽

Inorganic Nutrients ◽

Spatial And Temporal Variability ◽

Response Patterns ◽

Coastal Station ◽

Chl A ◽

B Vitamin ◽

Microbial Plankton

Abstract. We experimentally evaluated the temporal (interday and interseason) and spatial variability in microbial plankton responses to vitamin B12 and/or B1 supply (solely or in combination with inorganic nutrients) in coastal and oceanic waters of the northeast Atlantic Ocean. Phytoplankton and, to a lesser extent, prokaryotes were strongly limited by inorganic nutrients. Interday variability in microbial plankton responses to B vitamins was limited compared to interseason variability, suggesting that B-vitamin availability might be partially controlled by factors operating at seasonal scale. Chlorophyll a (Chl a) concentration and prokaryote biomass (PB) significantly increased after B-vitamin amendments in 13 % and 21 %, respectively, of the 216 cases (36 experiments × 6 treatments). Most of these positive responses were produced by treatments containing either B12 solely or B12 combined with B1 in oceanic waters, which was consistent with the significantly lower average vitamin-B12 ambient concentrations compared to that in the coastal station. Negative responses, implying a decrease in Chl a or PB, represented 21 % for phytoplankton and 26 % for prokaryotes. Growth stimulation by B1 addition was more frequent on prokaryotes than in phytoplankton, suggesting that B1 auxotrophy in the sampling area could be more widespread in prokaryotes than in phytoplankton. Negative responses to B vitamins were generalized in coastal surface waters in summer and were associated with a high contribution of Flavobacteriales to the prokaryote community. This observation suggests that the external supply of B12 and/or B1 may promote negative interactions between microbial components when B-vitamin auxotrophs are abundant. The microbial response patterns to B12 and/or B1 amendments were significantly correlated with changes in the prokaryotic community composition, highlighting the pivotal role of prokaryotes in B-vitamin cycling in marine ecosystems.

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Trichome abundance, chlorophyll content and the spectral coefficient for light absorption of Trichodesmium slicks observed in the Southwestern Atlantic

Journal of Plankton Research ◽

10.1093/plankt/fbaa009 ◽

2020 ◽

Vol 42 (2) ◽

pp. 135-139

Author(s):

Amália Maria Sacilotto Detoni ◽

Aurea Maria Ciotti

Keyword(s):

Natural Waters ◽

Degradation Products ◽

Spectral Feature ◽

Quantitative Information ◽

Southwestern Atlantic ◽

Austral Spring ◽

Chl A ◽

Ocean Colour Remote Sensing ◽

Break Region

Abstract Dense slicks of Trichodesmium were found in the shelf-break region in the Southwestern Atlantic during austral spring and autumn. A total of 14 slicks were sampled, and the absorption coefficients of phytoplankton (aph(λ)) indicated clear spectral features of phycobilin pigments. Although these samples showed low-degradation products and detrital importance, the chemotaxonomy, shape, and magnitude of aph(λ) indicated the importance of co-occurring species in the slicks. In addition to the difficulties of enumerating trichomes in situ, co-occurring species affect the expected chlorophyll-a (Chl-a) to trichome ratio, further complicating the detection of Trichodesmium by ocean colour remote sensing. Our results showed that trichome density could be predicted similarly by Chl-a and by aph(621), especially for trichome densities above 8000 trichomes L−1. The phycocyanin spectral feature is a potential source of quantitative information for the detection of Trichodesmium, but noninvasive techniques for quantifying the abundance of Trichodesmium in natural waters are necessary.

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Spatial and temporal variability of the phytoplankton community structure in the North Water Polynya, investigated using pigment biomarkers

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f04-152 ◽

2004 ◽

Vol 61 (11) ◽

pp. 2038-2052 ◽

Cited By ~ 36

Author(s):

Francesca Vidussi ◽

Suzanne Roy ◽

Connie Lovejoy ◽

Marie Gammelgaard ◽

Helge Abildhauge Thomsen ◽

...

Keyword(s):

Community Structure ◽

Phytoplankton Community ◽

Phytoplankton Bloom ◽

Circulation Pattern ◽

Spatial And Temporal Variability ◽

Phytoplankton Community Structure ◽

Southeastern Part ◽

Chl A ◽

The North ◽

North Water

Phytoplankton taxonomic pigments were measured by high-performance liquid chromatography (HPLC) during a 3-month survey (AprilJune 1998) in the North Water (NOW) Polynya (Canadian Arctic) to investigate changes in phytoplankton biomass and composition and the physicalchemical factors that influence these changes. A phytoplankton bloom with high chlorophyll a (Chl a) concentrations (up to 17.45 mg·m3 at 15 m) occurred in mid-May along the Greenland coast in the southeastern part of the NOW Polynya. The initiation of the phytoplankton bloom was linked to shallow mixed-layer depths. The contribution of the different phytoplankton groups to Chl a inferred using a factorization program (CHEMTAX) indicated that the bloom was diatom-dominated (maximum 94% diatoms). The phytoplankton community structure was influenced by the water mass characteristics and the surface circulation pattern. Autotrophic flagellates dominated in April and May along the Canadian coast, where cold Arctic waters with relatively deep mixed layers were found. In contrast, diatoms dominated in May along the Greenland coast in warmer water masses of Atlantic origin and during June in the whole polynya, except in the southernmost part.

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