High Primary Productivity Research Articles

Fisheries impact on the Sea of Marmara ecosystem structure and functioning during the last three decades

The Sea of Marmara (SoM), without doubt, is one of the most disturbed marine ecosystems of the Mediterranean basin. As a semi-enclosed and a recognized eutrophic basin, it has a unique natural characteristic by permanent stratification at ~25 m depth. The SoM ecosystem is under threat by multiple stressors from excessive nutrient enrichment, overfishing, invasive species, habitat loss to the climate change. Within this study, an assessment on the SoM ecosystem structure and functioning and its changes over time have been achieved. Hence, we firstly evaluate the SoM ecosystem over a period of three decades from the 1990s to the 2010s by using three mass-balance Ecopath models, secondly, we delineate the prevailing ecosystem structure and functioning in each period, thirdly we determine how the fishing impact contributed to the changes in the SoM since the 1990s and finally establish a baseline for the management and future studies of the ecosystem. The comparison of the models’ results for three consecutive time periods of the SoM showed that the energetic capacity of the ecosystem decreased significantly over the three decades while the decrease in cycling indices indicated that the SoM ecosystem became fragile to anthropogenic disturbances. According to ecosystem theory indices, the SoM is an immature ecosystem at a stage of autotrophic succession, with a very high total primary production, much more above unity that greatly exceeds total respiration. Our results highlighted that the SoM ecosystem was under bottom-up control exerted by mesozooplankton; however, anchovy was a bottleneck in energy transfers to higher trophic levels creating also a wasp-waist control in the food-web. The bycatch of demersal species with long life span, sharks and rays, brought them to the brink of going commercial extinction. Overall, the changes in the SoM ecosystem were due to the trophic cascades exerted by fisheries exploitation in addition to the changes in the productivity of the system. We conclude that the concomitant impacts of stressors on the SoM have been so diverse that an immediate action plan is required. Therefore, we propose a tentative outlook that will help in ecosystem monitoring and better management of the SoM.

A practical pCO2 estimation and carbonate dynamics at an event of hypoxic water upwelling in Tokyo Bay

Urban bays have been considered to have a high CO2 absorption function due to the high nutrient load and resultant primary production. It is expected to enhance the function by promoting a blue carbon policy co-beneficial with strengthening ecosystem services such as fisheries. Estimates of CO2 absorption in urban bays have been based mostly on fragmentary information from shipboard observations, and an evaluation based on continuous observation of water quality is necessary considering the large spatiotemporal variability of such bay environment. In particular, Tokyo Bay has a specific feature of water pollution problem of hypoxia and anoxia leading to emitting high CO2. Bottom hypoxic and anoxic waters develop from early summer to autumn in the central part of the bay and enclosed areas such as navigation channels and borrow pits. It is known that pCO2 becomes very high in these waters, and their upwelling (called blue tide in the bay from the discoloration of the sea surface) is thought to cause high CO2 emissions; however, the actual situation is unknown. We developed a practical method for continuous estimation of pCO2 by appropriately combining continuous observation of water quality using sensors and measurements of carbonate parameters by water sampling. The results show that a highly reproducible and practical method for continuous estimation of pCO2 was possible by combining in situ salinity and pH meters and the total alkalinity and calc. pH measured by a total alkalinity titrator for water samples. This method was then applied to the duration of blue tide that occurred in the head of the bay in the summer and autumn of 2021. The pCO2 in the surface water was found to increase significantly and exceed 2000 µatm due to the upwelling of anoxic bottom water containing high pCO2. Mean CO2 emissions of approximately +2150 and +1540 µmol m-2 h-1 were observed at two stations during the upwelling period. The mean values rose to +2390 and +2190 µmol m-2h-1 with the blue tide and lowered to +810 and +1120 µmol m-2 h-1 without it, suggesting that high CO2 emissions may occur due to upwelling, especially with blue tides.

Paleoenvironment and Organic Characterization of the Lower Cretaceous Lacustrine Source Rocks in the Erlian Basin: The Influence of Hydrothermal and Volcanic Activity on the Source Rock Quality.

Lower Cretaceous lacustrine source rocks in the Erlian Basin are highly heterogeneous. It is important to assess and explain these heterogeneities for the reconstruction of paleoenvironments and the prediction of high-quality source rock distributions. In this study, well-logging, organic, and elemental geochemical data were comprehensively analyzed for the source rocks of Member 4 of the Aershan Formation (Fm) and Member 1 of the Tengger Fm in the southern Bayindulan (BNAN), southern Wulanhua (WLHs), Anan, Aer, and southern Wuliyasitai sags of the Erlian Basin. The variability in sedimentary environments, sources of organic matter of the source rocks in different sags, and the influence of hydrothermal and volcanic activity on the source rock quality in the Erlian Basin were assessed. The results reveal that the source rocks can be divided into four types of organic facies (A, B, BC, and C). Organic facies A-B present hydrogen indices (HIs) higher than 400 mg/g and are mainly composed of mudstone and thick (average thickness >50 m) dolomitic mudstone, with biomarkers characterized by a Pr/Ph ratio lower than 1.0, a gammacerane/C30 hopane (Gam/C30H) ratio higher than 0.2, and a C19 tricyclic terpane/C23 tricyclic terpane (C19/C23TT) ratio lower than 0.6. Organic facies BC-C are composed of mudstone with an HI < 400 mg/g, with biomarkers characterized by a Pr/Ph ratio higher than 0.8, a Gam/C30H ratio lower than 0.2, a C19/C23TT ratio higher than 0.6, and a sterane/hopane ratio lower than 0.4. Dolomitic mudstone belonging to organic facies A-B is mainly developed in the BNAN, WLHs, and Anan sag and is characterized by a fault-controlled distribution in the sag, a right-declined rare earth element pattern, and an enrichment in the elements of Ba, Cu, Zn, Fe, and Ni. The genesis of high HI dolomitic mudstone is associated with hydrothermal and volcanic activity because the hydrothermal fluid or hydrolysis of volcanic ash result in increasing input of reducing gas and soluble nutrient ions, thus promoting the formation of anoxic and saline Cretaceous lakes with high primary productivity.

On the Spatial and Temporal Variations of Primary Production in the South China Sea

Primary production (PP) of the South China Sea (SCS) basin area (waters depth deeper than 200 m) is estimated using satellite products, with an overarching goal to reliably characterize the spatial distribution and temporal variation of PP of this important marginal sea. Among the PP models used, the absorption-based model (AbPM) showed better performance (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.47, N = 39). In comparison, the R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> value is 0.26 for a chlorophyll-based model (VGPM), and 0.15 for the carbon-based model (CbPM). Further, we observed that the PP spatial patterns obtained from these models were similar, but disagree on the annual PP magnitude, where VGPM and CbPM, respectively, obtained ~50% lower and ~40% higher annual PP compared to that obtained by AbPM. Especially, after analysis using Empirical Orthogonal Functions, the upwelling induced high PP off Luzon (winter) and Vietnam coast (summer) was clearly reflected in the first EOF mode of the AbPM results, and its principal component 1 has shown a decreasing trend for the period of 2003-2019 (-15.0% yr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for winter, p < 0.05; -14.7% yr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for summer, p < 0.05), which reflects the impact of weakening wind and higher sea surface temperature in the SCS. For the results of VGPM and CbPM, however, no strong relationships were found with the main regional oceanographic features. These results suggested that the spatiotemporal variations of SCS PP obtained from AbPM are more reasonable, and further highlight the importance of a robust model in reliably capturing large-scale spatiotemporal dynamics of primary production in marine environments.

Extraordinarily High Organic Matter Enrichment in Upper Permian Wujiaping Formation in the Kaijiang-Liangping Trough, Sichuan Basin

The study of extraordinarily high organic matter content (EHOMC) is beneficial to promote the fine evaluation of shale oil and gas, but so far, there have been few studies on its mechanism. This paper carried out a comprehensive lithological and geochemical analysis of the black shales of the Wujiaping Formation in the Kaijiang-Liangping Trough. The results showed that the black shales of the Wujiaping Formation can be divided into two units (the upper and lower parts), and EHOMC occurs in its upper part. The redox-sensitive trace elements (RSTEs), MoEF-UEF covariation, and Ni/Co correlation showed that the lower part of Wujiaping Formation was a weakly restricted oxidation environment, while the upper part evolved into a sulfidation reducing environment. The productivity indicator elements (BaXS, NiXS, CuXS, P, and Mo) indicated that the upper Wujiaping Formation had higher primary productivity than the lower part. However, rare earth elements ((La/Yb)N) indicated that the deposition rate in the lower part of the Wujiaping Formation was higher than that in the upper part. In general, although the oxygenated water in the lower part of the Wujiaping Formation is not conducive to the preservation of organic matter, the high input of nutrients from land sources and the high deposition rate inhibit the decomposition of organic matter, so the lower part has a certain degree of organic matter accumulation. The sulfidation reducing environment and high paleoproductivity are the main reasons for the enrichment of organic matter in the upper part of the Wujiaping Formation. In addition, the sulfidation reducing environment and high paleoproductivity occurred during the violent upwelling at the end of Guadeloupe, a period of high sea level, these factors have jointly contributed to the enrichment of OM in the upper the Wujiaping Formation.

Temporal dynamics of the deep-sea pink urchin Strongylocentrotus fragilis on the Northeast Pacific continental margin

The Northeast Pacific continental margin is characterized by strong seasonal upwelling, which drives high primary productivity, and supports high diversity and biomass of benthic megafauna. The recent occurrence of a marine heat wave (“The Blob”, sensu Kintisch, 2015) in 2013–2016 resulted in changes to phytoplankton community composition and loss of coastal kelp abundance and diversity, reducing gross primary productivity in the region. However, cumulative effects of marine heat waves and ongoing basin-scale deoxygenation in deep-sea ecosystems remain poorly understood. Here, we use a 7-year time series of physicochemical and video imagery data from Ocean Networks Canada's NEPTUNE observatory to investigate temporal dynamics of the deep-sea pink urchin Strongylocentrotus fragilis in relation to multi-year environmental variability. Using generalized additive models, we show that local S. fragilis density at Barkley Upper Slope (420 m) fluctuated over time and was partially explained by changes in dissolved oxygen concentration and suspended particulate matter in the benthic boundary layer (ADCP backscatter), with high urchin density corresponding to high oxygen and low backscatter. Seafloor dissolved oxygen ranged from 0.80 to 1.89 mL/L and varied seasonally, exhibiting a clear negative correlation with sea surface primary productivity (MODIS satellite Chl-a data), corresponding with the onset of yearly upwelling conditions. However, during the anomalously warm years affected by ‘The Blob’, dampened upwelling maintained higher dissolved oxygen conditions near the seafloor. S. fragilis density declined during ‘Blob’ conditions, likely in response to reduced kelp and phytodetritus subsidies from coastal waters. We propose a foraging-respiration trade-off hypothesis, whereby S. fragilis forages in deeper water during weak upwelling and migrates to shallower habitats during low oxygen conditions. S. fragilis is an important bioturbator and detritivore; changes in the density and distribution of this species may directly affect sediment turnover rates and nutrient cycling on the continental margin, with consequences for surface and coastal productivity.https://github.com/rjcommand/.

Upwelled plankton community modulates surface bloom succession and nutrient availability in a natural plankton assemblage

Abstract. Upwelling of nutrient-rich waters into the sunlit surface layer of the ocean supports high primary productivity in eastern boundary upwelling systems (EBUSs). However, subsurface waters contain not only macronutrients (N, P, Si) but also micronutrients, organic matter and seed microbial communities that may modify the response to macronutrient inputs via upwelling. These additional factors are often neglected when investigating upwelling impacts on surface ocean productivity. Here, we investigated how different components of upwelled water (macronutrients, organic nutrients and seed communities) drive the response of surface plankton communities to upwelling in the Peruvian coastal zone. Results from our short-term (10 d) study show that the most influential drivers in upwelled deep water are (1) the ratio of inorganic nutrients (NOx : PO43-) and (2) the microbial community present that can seed heterogeneity in phytoplankton succession and modify the stoichiometry of residual inorganic nutrients after phytoplankton blooms. Hence, this study suggests that phytoplankton succession after upwelling is modified by factors other than the physical supply of inorganic nutrients. This would likely affect trophic transfer and overall productivity in these highly fertile marine ecosystems.

Dark Matter Enhances Interactions within Both Microbes and Dissolved Organic Matter under Global Change.

There are vast but uncharacterized microbial taxa and chemical metabolites (that is, dark matter) across the Earth's ecosystems. A lack of knowledge about dark matter hinders a complete understanding of microbial ecology and biogeochemical cycles. Here, we examine sediment bacteria and dissolved organic matter (DOM) in 300 microcosms along experimental global change gradients in subtropical and subarctic climate zones of China and Norway, respectively. We develop an indicator to quantify the importance of dark matter by comparing co-occurrence network patterns with and without dark matter in bacterial or DOM assemblages. In both climate zones, dark matter constitutes approximately 30-56% of bacterial taxa and DOM metabolites and changes connectivity within bacterial and DOM assemblages by between -15.5 and +61.8%. Dark matter is generally more important for changing network connectivity within DOM assemblages than those of microbes, especially in the subtropical zone. However, the importance of dark matter along global change gradients is strongly correlated between bacteria and DOM and consistently increased toward higher primary productivity because of increasing temperatures and nutrient enrichment. Our findings highlight the importance of microbial and chemical dark matter for changing biogeochemical interactions under global change.

Eucalyptus clones respond differentially for heavy-metals phytoextraction and carbon sequestration in tree biomass and soil with distillery effluents irrigation in north-western India

Forest ecology has significant potential for carbon (C) and heavy-metals’ accumulation, and is considered important for mitigating environmental impacts within the ecosystem. Heavy-metals enter the soil–plant system via different anthropogenic activities per se industrialization, which has huge contribution through the discharge of heavy-metals enriched effluents. Although, irrigation with effluents to large biomass producing forestry plantation e.g. Eucalyptus sp. with high net primary production (NPP) are considered ecologically and environmentally safe, yet the information on differential response of diverse clones towards applied effluents is scares. We therefore, performed field evaluation of nine Eucalyptus clones originated from diverse agro-ecological environments irrigated with distillery effluents to investigate their growth attributes, heavy-metals (e.g. As, Cr, Cd and Ni) and micro-nutrients (e.g. Cu, Zn, Fe and Mn) uptake potential, and C storage in above-and below-ground biomass and sequestration in soil C pool. The diameter at breast height (DBH), tree volume, fresh and dry biomass of stems, leaves, branches and roots of C-316 clone was significantly (p < 0.05) higher, lowest for PE-6, whilst the C-411, C-2045, PE-5, PE-7, PE-8, PE-11 and C-413 were in-between. The Cr uptake was significantly higher for PE-8 and C-413, Ni uptake in PE-6 and C-413 and Pb uptake in clone C-2045. Among micro-nutrients, Zn, Mn and Fe uptake was significantly higher for C-316, compared with other clones. However, the metal content in surface (0–15 cm) soil layer was well below the threshold level. The partitioning of NPP among different above-and below-ground biomass components revealed that dry stem biomass comprised ~ 54.8–56.7%, branches ~ 15.8–17.1%, while leaves ~ 5.6–7.5% of total dry tree biomass. Root biomass comprised ~ 21.3% of total tree biomass. Carbon stocks in dry above-ground biomass (stems + branches + leaves) varied between 33.9 and 59.5 kg C tree−1, and were significantly higher for C-316, and lowest for PE-6 clones. The total C sequestration in tree biomass varied between 229.7 and 450.9 Mg C ha−1 in different clones; with significantly higher in C-316 and lowest in PE-6. Carbon sequestration rate varied between 57.4 and 112.7 Mg C ha−1 year−1 for different Eucalyptus clones. Total organic C (TOC) stocks in surface soil layer under C-413, C-411 and C-316 clones were significantly (p < 0.05) higher than others. The discriminant function analysis (DFA) showed that two significant canonical discriminant functions (DFs) viz. DF-1 and DF-2 involving total tree biomass, total uptake of As, Pb, Zn, Mn and Fe in above-ground biomass of Eucalyptus clones distinguished different cones, appropriately grouping 97.5% of the tested clones. These results underpin overwhelming significance of C-316 plantation for increased heavy-metals’ uptake with co-benefits of C sequestration in tree biomass as well as in soils. Therefore, a stringent policy framework for large scale C-316 clone plantation in regions with availability of distillery effluents is required for restoring the forest ecosystem on sustainability basis.

Preservation of biotic and palaeoenvironmental signatures in organosulfur compounds of immature fine-grained sedimentary rocks

Organosulfur compounds (OSCs) in sedimentary rocks are considered to have formed primarily by abiotic incorporation of inorganic sulfur species into biogenetic functionalized molecules during early diagenesis, thus preserving carbon skeletons of appropriate biomolecules. OSCs could be characterized at a molecular level by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) even when they are small in amounts and large in molecular weights. Herein, to reveal the palaeoecological and palaeoenvironmental information that OSCs have recorded but might not be contained in other biomarkers, OSCs’ composition in solvent extracts of rocks with different geological histories were determined utilizing FT-ICR-MS. The analyzed natural laboratories are the marine Schöneck, Dynow and Posidonia formations and the lacustrine Wealden Formation which are in the late diagenetic or early catagenetic stages.The prevailing iron-deficient sulfidic depositional settings of the marine Posidonia and Schöneck formations are reflected by abundant OSCs bearing up to three sulfur atoms. The high ratios of reduced relative to oxidized forms (Sz versus SzOx) further illustrate the restricted presence of oxidants at the oxic-anoxic interfaces. The high average oxygen numbers of S1Ox compounds and the exclusive presence of nitrogenous OSCs (SzNy and SzNyOx) found in the marine rock extracts document the high abundances of polyoxygenated compounds and proteinaceous moieties in marine organisms that can be sulfurized. In contrast, the lacustrine organisms contain abundant sulfurizable aliphatic moieties.The observed prominent enrichment of Sz and SzOx compounds containing 40, 35, 30, 25 carbon atoms are associated with the selective and efficient preservation of polyfunctionalized biomolecules via sulfurization, such as C40 carotenoids, C35 bacteriohopanepolyols, C30 unsaturated tetracyclic polyprenoid alcohols, or C25 or C30 highly branched isoprenoid (HBI) polyenes. The strong enrichment of sulfurized C35 bacteriohopanepolyols can be developed as an indicator of the low levels of oxygen exposure prior to sulfurization, which occur only in the Dynow and Schöneck formations. The prominent enrichment of sulfurized carotenoids is generally associated with high primary productivity. While the strongly enriched sulfurized HBI polyenes in the Upper Schöneck Formation is indicative for diatom blooms, the precursors of C30 pentacyclic polyprenoid organosulfur compounds are more abundant in fresh/brackish water algae.

Composition of terrestrial mammal assemblages and their habitat use in unflooded and flooded blackwater forests in the Central Amazon.

Several forest types compose the apparently homogenous forest landscape of the lowland Amazon. The seasonally flooded forests (igapós) of the narrow floodplains of the blackwater rivers of the Amazon basin support their community of animals; however, these animals are required to adapt to survive in this environment. Furthermore, several taxa are an important source of seasonal resources for the animals in the adjacent unflooded forest (terra firme). During the low-water phase, the igapó becomes available to terrestrial species that make use of terra firme and igapó forests. Nonetheless, these lateral movements of terrestrial mammals between hydrologically distinct forest types remain poorly understood. This study tested the hypothesis that the attributes of the assemblages (abundance, richness, evenness, and functional groups) of the terrestrial mammals in both these forest types of the Cuieiras River basin, which is located in the Central Amazon, are distinct and arise from the ecological heterogeneity induced by seasonal floods. After a sampling effort of 10,743 camera trap days over four campaigns, two for the terra firme (6,013 trap days) and two for the igapó forests (4,730 trap days), a total of 31 mammal species (five were considered eventual) were recorded in both forest types. The species richness was similar in the igapó and terra firme forests, and the species abundance and biomass were greater in the terra firme forest, which were probably due to its higher primary productivity; whereas the evenness was increased in the igapós when compared to the terra firme forest. Although both forest types shared 84% of the species, generally a marked difference was observed in the composition of the terrestrial mammal species. These differences were associated with abundances of some specific functional groups, i.e., frugivores/granivores. Within-group variation was explained by balanced variation in abundance and turnover, which the individuals of a given species at one site were substituted by an equivalent number of individuals of a different species at another site. However, the occupancy was similar between both forest types for some groups such as carnivores. These findings indicate that seasonal flooding is a relevant factor in structuring the composition of terrestrial mammal assemblages between terra firme and floodplain forests, even in nutrient-poor habitats such as igapós. The results also highlight the importance of maintaining the mosaic of natural habitats on the scale of the entire landscape, with major drainage basins representing management units that provide sufficiently large areas to support a range of ecological processes (e.g., nutrient transport, lateral movements and the persistence of apex predators).

High ammonium recycling in an anthropogenically altered Yeongsan River Estuary, South Korea

Regenerated nitrogen (N) cycling was studied in a turbid and nutrient-rich estuary located in the southeast region of the Yellow Sea (Yeongsan River Estuary; YRE), in order to elucidate the biogeochemical consequences of coastal development. Ammonium regeneration and potential uptake rates were measured from March 2012 to June 2013 using 15N tracer techniques. Size fractionation suggested that small-sized bacteria (&amp;lt;0.7 μm), rather than zooplankton, were responsible for most of the ammonium regeneration. Intermittent freshwater discharge events might have prevented stable zooplankton community development and caused the insignificant role of zooplankton in ammonium regeneration. Ammonium regeneration and potential uptake rates were relatively high (0.1–1.2 and 0.2–1.5 µmol L−1 h−1, respectively), and were highest during summer. Ammonium turnover times were shorter than water residence times throughout the study period. These results indicate that ammonium is actively recycled and is likely to supply enough N required to sustain the high primary productivity observed in the YRE (50%–450%). Reduced turbidity and increased water residence times caused by the construction of an estuarine dam in the YRE have probably resulted in the formation of optimal conditions for the high ammonium regeneration.

The abundance and species assemblages of dinoflagellate cysts at sediments in the three estuaries of the Southern part of South Sulawesi

Harmful algal blooms (HAB) are a phenomenon of drastically increasing phytoplankton populations, which can cause problems in aquatic ecosystems. Dinoflagellate cysts are a type of phytoplankton that are the main source of causing the HAB phenomenon; this occurs due to unfavorable environmental conditions. The Southern Estuary of South Sulawesi has high fishery resources and high primary productivity. The coastal areas around these waters are widely used for anthropogenic activities that trigger nutrient increases. There are no studies on HAB, especially the abundance and community structure of dinoflagellate cysts at this location. This study aims to identify the types, abundance, and species assemblages of dinoflagellate cysts in the three estuaries of southern South Sulawesi. Sampling was carried out at three locations, namely the Pappa River Estuary, the Kelara River Estuary, and the Calendu River Estuary, in January 2022. Each location consists of 4 stations, 3 sub-stations with 3 repetitions sampling for each substation. Results showed that there were 34 species of dinoflagellate cysts belonging to 6 families, namely Gonyaulacaceae, Gymnodiniaceae, Osteropsidaceae, Peridiniaceae, Polykrikaceae, and Protoperidiaceae. The highest abundance of dinoflagellate cysts was at the Calendu River estuary station III, accounting for 82 cysts g−1, while the lowest abundance of dinoflagellate cysts was found at Pappa River estuaries stations I and II, accounting for 8 cysts g−1. The level of diversity, uniformity, and richness of dinoflagellate cysts was not significantly different in the three study sites. The family Osteropsidaceae was the most common type of dinoflagellate cyst found in the three study sites. The Osteropsidaceae family is a type of dinoflagellate cyst that contains toxins, so it can be assumed that the three research sites have the potential for HAB.

Determination of potential fishing ground of mackerel fish (Rastrelliger kanagurta) using satellite imagery in the Malacca Strait

Mackerel fish (Rastrelliger kanagurta) is a fishery commodity in high demand by the community which is caught in the Malacca Strait. The number of mackerel catches tends to fluctuate every month because it is influenced by different mackerel fishing grounds. Determination of fishing ground tends to use traditional methods such as seeing ripples and a flock of birds flying above the water surface. This study aims to determine the effect of sea surface temperature and chlorophyll-a concentration on mackerel catches and determine the value of primary productivity of the VGPM model every month and also to determine the potential fishing ground to catch mackerel fish based on the sea surface temperature (SST) and chlorophyll-a concentration and Aqua MODIS satellite image data (SST and Chlorophyll-a) were downloaded from oceancolour.gfc.nasa.gov while the catch data were obtained from the Belawan Ocean Fishery Port, the data was taken from 2016 to 2020. The influence of SST and Chlorophyll-a concentration was analyzed and visualized on a map. It was found that every month the potential fishing ground for catching mackerel fish has a different location due to the influence of sea surface temperature and fluctuating chlorophyll-a caused by seasonal changes that occur in Indonesia, where the average SST ranged from 30.01 to 31.34°C and the concentration of chlorophyll-a ranged from 1.48 – 2.28 mg/m3 from 2016 – 2020 with a high net primary productivity ranged from 802.12 – 1.341.59 mgC/m2/day from 2016 to 2020. The potential area for catching mackerel (Rastrelliger kanagurta) caught using purse seines in the Malacca Strait is in the coordinates range of 980 10"51.6” – 1000 19"4.8” (longitude) and 30 28" 48” – 4 0 56"34.8” (latitude) and perpendicular horizontally to the Langkat Regency to Asahan Regency shoreline with a distance under 12 miles to 50 miles. Information on potential areas for catching mackerel can help fishermen in fishing activities so that they are more efficient and catch maximum results.

Ecological security assessment of Qinzhou coastal zone based on Driving forces-Pressure-State-Impact-Response (DPSIR) model

A coastal zone represents the intersection of ocean and land, and is characterized by high primary productivity, biodiversity, and rich resources but with strong sensitivity and vulnerability of the natural environment. In this study, 29 indicators reflecting the status of ecological security were selected to construct an ecological security evaluation index system using the Driving force Pressure State Impact Response (DPSIR) model. The comprehensive index method was used to evaluate the ecological security of Qinzhou coastal zone from 2011 to 2020 and to explore the driving factors of its evolution. The results showed that (1) In the past 10 years, the ecological security of Qinzhou coastal zone fluctuated and developed, and the security level changed from early warning – safer – more dangerous – early warning to safer; and the security level was the lowest (0.361) in 2014. The main reason was the impact of ecological marine disasters, such as three red tides with the eutrophication index of seawater as high as 4.170. (2) Since 2015, the ecological security of the coastal zone has shown an upward trend, which was mainly due to the implementation of the newly revised environmental protection law in the same year, the comprehensive promotion of “The 13th Five-Year Plan for environmental protection”, and a series of measures related to the construction of ecological civilization and environmental protection, which provided a strong guarantee for the ecological security of the coastal zone. This study proposes measures to promote the better development of the ecological environment of Qinzhou coastal zone.

Formation conditions of Ediacaran–Cambrian cherts in South China: Implications for marine redox conditions and paleoecology

The Ediacaran–Cambrian transition period was a critical time interval for the environmental fluctuations and organismal evolution in geological history, popularly known as the “Cambrian Explosion”. The diagenetic mechanism of the widely developed Liuchapo bedded cherts in South China remain unclear and controversial during this critical time interval. To address this, we examined silicon and oxygen isotopes, as well as major and trace elements in the Liuchapo cherts from three wells developed from slope to basin facies in South China. Results reveal that the bedded cherts from the three wells were affected by episodic hydrothermal activity, and the percentage of hydrothermal fluids is highest in the Xc1 well and lowest in the Xb1 well. The paleo-seawater temperature, calculated from chert oxygen isotope values, present a gradual increasing trend from shallow- to deep- areas in South China from 542 to 526 Ma. Redox proxies indicate that the water column of the Xa1 and Xc1 wells were dominated by suboxic condition, while those of the Xb1 well was mainly in oxic conditions. There should exist an oxygen minimum zone (OMZ) during the shelf and slope transition. A suitable temperature and oxic environment are conducive to biological reproduction, which is consistent with higher primary productivity and abundant acritarch fossils in the Xb1 well. Silicon isotope values range from −0.6 ‰ to 1.2 ‰ in the three wells. The diagenetic origin of the Xa1, Xb1, and Xc1 wells was the consequence of the mixture of hydrothermal fluid and seawater, biological activity, and direct hydrothermal precipitation, respectively. Due to the redox condition and seawater temperature variation, silica-secreting organisms should be relatively limited. The episodic hydrothermal fluid, biological activity, and replacement of precursor rock may jointly affect the formation of the Liuchapo bedded cherts during the Ediacaran–Cambrian transition.

Towards process-oriented management of tropical reefs in the anthropocene

Tropical reefs and the fish relying on them are under increasing pressure. Shallow-reef fish provide important ecological information in addition to sustaining fisheries, tourism and more. Although empirical metrics of fish biomass are widely used in fisheries management, metrics of biomass production—how much new biomass is produced over time—are rarely estimated even though such production informs potential fisheries yields. Here we estimate fish standing biomass (B), biomass production (P, the rate of biomass accumulation) and biomass turnover (P/B ratio, the rate of biomass replacement) for 1,979 tropical reef sites spanning 39 tropical countries. On the basis of fish standing biomass and biomass turnover, we propose a conceptual framework that splits reefs into three classes to visualize ecological and socio-economic risk and help guide spatial management interventions (for example, marine protected areas) to optimize returns on conservation efforts. At large scales, high turnover was associated with high human pressure and low primary productivity, whereas high biomass was associated with low human pressure and high primary productivity. Going beyond standing fish biomass to consider dynamic ecological processes can better guide regional coral reef conservation and sustainable fisheries management.

Bacterial dynamics along the west coast of India during the non-monsoon and monsoon season

The West Coast of India (WCI) is influenced largely by semi-annual changes in the wind pattern and monsoonal currents. This is reported to cause upwelling which increases the phytoplankton growth in this region during the summer monsoon and it is recorded to be one of the world's highest primary productivity. Increase in the phytoplankton productivity is known to influence the microbial activity which is one of the key biogeochemical processes of the marine ecosystem as it plays an important role in the biotransformation of organic matter. However, the changes in the bacterial community structure and their heterotrophic enzyme activity with increasing primary production are not clearly understood from this region. Hence in this study, the bacterial dynamics along the WCI at Goa, Mangalore and Trivandrum, were investigated from the continental shelf, slope and off-shore region during the non-monsoon and monsoon season. Seasonal changes in the bacterial parameters such as abundance, viable counts and radioactivity based in-situ primary and bacterial productivity were estimated, along with the physicochemical characteristics. Statistical analysis shows a significant (p < 0.05) correlation between primary and bacterial productivity. Significant seasonal variations could also be established for the physicochemical parameters such as dissolved oxygen, nitrate, nitrite and phosphate, fluorescence values representing the chlorophyll concentration, bacterial abundance, viable counts and productivity. Taxonomic diversity studies on the cultivable bacterial morphotypes have shown that Proteobacteria, Firmicutes and Actinobacteria were the major phyla found during both the non-monsoon and monsoon season and Bacteroidetes, was represented only in the non-monsoon season. The bacterial community structure at phylum, genus and operational taxonomic unit levels also changed with higher diversity in the monsoon season. However, the hydrolytic enzyme activity of the bacterial morphotypes was comparatively lower during the monsoon season probably due to the active primary production. Though this study has improved our understanding of the monsoonal influence on the bacterial dynamics along the WCI, further studies based on metagenomic and transcriptome analysis are required to get a better understanding of the role played by the bacterial community from this region.

Atmospheric temperature and humidity demonstrated strong correlation with productivity in tropical moist deciduous forests.

Tropical forests sequester six times higher carbon than that released by humans annually into the atmosphere. These biodiversity-rich tropical forests have high net primary productivity (NPP), which differs among constituent plant communities. Tropical moist deciduous forests occupy 179,335 km2 of India's geographical area and constitute 44% of the country's total protected area (PA) forests. The productivity of these forests has neither been estimated specifically nor precisely. We measured the annual NPP of three predominant distinct community types, viz., mixed (DM), sal (SM), and teak (TP), in a tropical moist deciduous forestin northern India. The NPP was estimated from tree biomass data collected from nine long-term ecological research (LTER) plots of 1ha each representing the above three community types. The estimatedannual NPP were 10.28, 6.25, and 9.79Mgha-1year-1 in DM; 8.93, 7.09, and 10.59Mgha-1year-1 in SM; and 14.57, 7.14, and 13.56Mgha-1year-1 in TP for the years 2010, 2011, and 2012, respectively. The NPP was correlated with tree density, height and DBH, species richness, diversity, microclimatic and edaphic variables, and leaf area index (LAI) using principal component analysis (PCA) and generalized linear modeling (GLM). Air temperature and humidity were strongly related to NPP in all the community types, while "complementarity" and "selection effects" contributed to the NPP in both the sal and mixed forestcommunities with equal importance, and the NPP in teak plantation ould point to "dominance effect."

Organic matter enrichment due to high primary productivity in the deep-water shelf: Insights from the lower Cambrian Qiongzhusi shales of the central Sichuan Basin, SW China

• Cambrian shales in the Sichuan Basin were formed under humid anoxic conditions with low-moderate productivity. • High primary productivity was responsible for organic matter enrichment. • Much higher primary productivity occurred in the deep-water shelf than in the shallow-water shelf. • Hydrothermal upwelling can increase primary productivity. The formation and enrichment mechanisms of organic-rich shales under different marine environments remain unclear. Recently, Cambrian Qiongzhusi (QZS) shales with greater thickness and total organic carbon (TOC) content were found in a deep-water shelf (DWS) than in the adjacent shallow-water shelf (SWS) of the central Sichuan Basin, and these locations provide ideal conditions for determining the mechanisms underlying differences in organic matter (OM) enrichment. In this study, we investigated the TOC, pyrolysis, organic carbon isotopes (δ 13 C org ), biomarkers, and elemental geochemistry of the QZS shales. Based on a detailed comparison between shales from the DWS to the SWS, an OM enrichment model of different shelf conditions was established and the reasons for the higher TOC content in the DWS were clarified. The deposition of QZS shales was accompanied by a large-scale regional transgression. Against the background of an overall humid climate, the water mass at the bottom of the DWS was more restricted, resulting in limited external material exchange and supply. The water mass of the DWS represented by the bottom of the QZS was anoxic and showed the development of euxinic conditions. The biogenic Ba (Ba bio ) content of the samples in the DWS under deep basinal conditions was significantly greater than that in the SWS region, which reflects higher primary productivity and is associated with a large accommodating space and upwelling flows caused by the hydrothermal activities in the DWS. Under conditions in which OM enrichment is dominated by productivity, the DWS is a more favorable location for the formation of high-quality shales.